FAQ: Vibration under braking: warped rotors? NO!

[StingertimeNC]

Nice post! Last track session I went with Hawk HPS 5.0's, ponly because I had a decent experience at my first track event. Unfortunately they did not give me the confidence to push the car.

I have a set of Gloc R12's to pair up with my dba rotors for my next track session in March. Can't wait!

Car is fun at the track and always turns heads. Nice to see another member tracking the Stinger!!

 

[stoopid]

No, I don't have enough power to chase down the big guns, but not having to worry about the brakes was a big plus. The instructor that sat with me asked what mod I did and was very glad to hear what I did for brake prep.
View attachment 77478

Any chance you post your track dashcam footage online? I'm curious to see what someone with some time with the Stinger can do.

 

[Snicklefritz]

I didn't see EBC Bluestuff mentioned much here, so I thought I should give my two cents on it. Like just about every Stinger owner with the crappy Brembo OEM brake pads, mine had the infamous pad material deposit. Since I normally take it really easy in everyday driving, it didn't bother me much. The only thing I noticed was a rough gritty feel whenever I had to step on the brake a bit harder than usual. Otherwise, the Brembos did just fine. Even with quite a few AutoX's last year, I knew the brakes were not worked hard enough to cause heat spotting, but I did keep a very close eye on all four rotors. Below was about as bad as it got.
View attachment 77473
Not ideal, but far from unserviceable for normal everyday commuting. That said, compared to our '21 G70 6MT Sport with the Euro-Sport pad (below), which over the same period of time had absolutely no brake pad material transfer and worked brilliantly, I knew the Stinger OEM pads had to go sooner or later.

View attachment 77472

So, when I signed up for a Track Dat at Motorsport Ranch at Cresson last year, I did my due diligence to look for a worthy replacement pad. Having had excellent experience with EBC sintered HH pads on many of my motorcycles over the years, I was a bit partial to the brand. So I chose their Bluestuff "super-sport and Track Day" pad.

Being the cheapskate that I am, and the rotors still in excellent shape with no grooving or measurable tapering, I just scrubbed off the pad material deposit and slapped on the Bluestuff.
View attachment 77474
As I was just finishing up the initial "breaking in" or seating the pad to the rotor, and starting in on stage 1 bedding in, the rear was nice and smooth, but the front started to vibrate a bit. Yeah, sometimes the Scrooge does get caught for being cheap. No biggie, I took off the front rotors and had them turned at O'Reily's for $25 a rotor. Back on they went.
View attachment 77475
O'Reily's did an excellent job and only shaved less than 0.2mm off each surface. I'm still far from the minimum rotor thickness (F 28.0mm R 20.4mm).
View attachment 77476
As expected, the front brakes complained no more, and I repeated the seating process for another 100 miles or so of really easy driving/braking. Then did my stage 1 bedding in, per EBC instructions. I decided to wait for the actual track session to do Stage 2 bedding in, because trying to do it on public road was just not practical, or safe. All there was left to prep was bleed/flush with high-temp DOT4 fluid.

So Track Day came, and I took it easy for the first session, mainly to memorized all 16 turns of the long 3.1mile course, which at my age took a while. Just as well, it gave the pad and rotor time to really know each other, consummately their marriage, and bed in (pun intended) properly.
View attachment 77477
For the other three 20-min sessions, Bluestuff performed brilliantly - zero fade, linear pedal feel, and ample braking power that's easy to modulate.

No, I don't have enough power to chase down the big guns, but not having to worry about the brakes was a big plus. The instructor that sat with me asked what mod I did and was very glad to hear what I did for brake prep.
View attachment 77478

This is what it looked like at the end of the day. The brakes got plenty toasty, enough to disintegrate the plastic hub-centric rings that TireRack included with the Enkei TFRs. Lesson learned there. All 4 rotors had that nice even color sheen that's indicative of the proper kind of micro-layer pad material transfer track-prepped brakes should look like - for optimum brake performance and rotor life.
View attachment 77480

Now... the downside. Yes, there are always compromises with everything related to engineering. Like just about all performance-oriented brake pads, the Bluestuff produces prodigious amount of brake dust. The Euro-Sport pads on our G70 6MT are the same. That is just the nature of the beast. This is going to put off a lot of street drivers, but to me, it is a worthy price to pay for excellent track performance. This is why I buy easy-to-clean wheels. And it's why I went with the Enkei TFR.

Also, performance pads are usually on the noisy side. Some like to hiss. Others love to creak. Bluestuff tend to groan, when they are just making/breaking contact with the rotor. Not surprising, since their friction coefficient remains very very high, even when stone cold. I have to be really careful to feather the brake pedal pressure to minimize the noise, especially in crawling stop-n-go rush hour traffic. Doesn't bother me that much. I just look at it like the Bluestuff pads are complaining why I made they put up with this s***, when we should be out at the track tearing up the corners.

Thirdly, the wear rate is higher than with street pads. Again, that is just the nature of the beast. 6 months in including the track day, the pads are visibly worn. I have not taken off the pads and mic'ed them, but I would have no problem doing another track day right now. Doing a 3rd TD... that would be very iffy. Once pads are worn to the last 1/3, their wear rate accelerates. Like tires, brake pads are consumables. Their performance vs. life expectancy is also similar to tires. Thankfully, pads are nowhere near as expensive as tires.

Would I recommend them? If track days are in your plans - absolutely. If not, they still make excellent street performance pads, as long as you are okay with the compromise. Otherwise, something a bit less hard-edged, like their Yellowstuff, or even Redstuff, might be better suited.

That's it. I'll leave you with the thought that regardless of what you might think of the Stinger, it is first and foremost a really great GT car. A pure-bred sport car it is most definitely not. As long as you keep your expectations in check, much fun you'll have.

Otherwise, it's why folks bring track tools like this (taken at the same track day):
View attachment 77479

questions: how far into ownership were you when you put the brembos on? how expensive was that?

 

[Volfy]

Nice post! Last track session I went with Hawk HPS 5.0's, ponly because I had a decent experience at my first track event. Unfortunately they did not give me the confidence to push the car.

I have a set of Gloc R12's to pair up with my dba rotors for my next track session in March. Can't wait!

Car is fun at the track and always turns heads. Nice to see another member tracking the Stinger!!

I'm surprised to hear the Hawk pads didn't do well enough to your liking. They are quite well known in SCCA circles.

Stinger/G70 are an uncommon sight at AutoX and especially Track Days. Probably because they are not the best track bunnies, but with a bit of work, they do well enough to be a barrel of fun. Yes, it's great share notes.

Any chance you post your track dashcam footage online? I'm curious to see what someone with some time with the Stinger can do.

Please PM me, I can't seem to find a way to PM, maybe because I haven't posted enough?

questions: how far into ownership were you when you put the brembos on? how expensive was that?

I bought the '19 base 2.0T around the end of 2020, when dealerships were just coming out of the Pandemic lockdown full of inventory and were practically giving them away. It was too good a deal to pass up on. As I was working the deal, I already found a set of almost brand new Brembos on ebay listed for $500. Seller happened to be local so I asked if he would be okay to show them in person. IIRC, I offered him $400 cash and came home with them before I picked up the Stinger. I wasn't aware of any Stinger/G70 that had done Brembo conversion at that time, but I did know Genesis Coupe guys have been done them, so I just took a leap of faith.


I think I drove the Stinger with stock brakes for a few hundred miles before starting the conversion. I decided to use the pads that came with the Brembos, since they were in excellent shape. However, the stock rotors on the 2.0T Stinger were smaller diameter, so I bought a set from Advanced Auto for a little over $200. The front dust shield fitted the Brembos perfectly, but the rear dust shields were too small. At the time, I just bent the stock shields to fit - functional if not all that pretty. Later I bought a set of brand new dust shields from an online Kia OEM parts house. Swapping them out turned out to be a royal PITN, but since I swapped the stock open differential with an LSD from a G70 6MT Sport (also found on ebay), at least I got to kill two birds with one stone.



All said and done, I probably have $800 in the Brembo conversion.

 

[Snicklefritz]

I'm surprised to hear the Hawk pads didn't do well enough to your liking. They are quite well known in SCCA circles.

Stinger/G70 are an uncommon sight at AutoX and especially Track Days. Probably because they are not the best track bunnies, but with a bit of work, they do well enough to be a barrel of fun. Yes, it's great share notes.


Please PM me, I can't seem to find a way to PM, maybe because I haven't posted enough?


I bought the '19 base 2.0T around the end of 2020, when dealerships were just coming out of the Pandemic lockdown full of inventory and were practically giving them away. It was too good a deal to pass up on. As I was working the deal, I already found a set of almost brand new Brembos on ebay listed for $500. Seller happened to be local so I asked if he would be okay to show them in person. IIRC, I offered him $400 cash and came home with them before I picked up the Stinger. I wasn't aware of any Stinger/G70 that had done Brembo conversion at that time, but I did know Genesis Coupe guys have been done them, so I just took a leap of faith.
View attachment 77487

I think I drove the Stinger with stock brakes for a few hundred miles before starting the conversion. I decided to use the pads that came with the Brembos, since they were in excellent shape. However, the stock rotors on the 2.0T Stinger were smaller diameter, so I bought a set from Advanced Auto for a little over $200. The front dust shield fitted the Brembos perfectly, but the rear dust shields were too small. At the time, I just bent the stock shields to fit - functional if not all that pretty. Later I bought a set of brand new dust shields from an online Kia OEM parts house. Swapping them out turned out to be a royal PITN, but since I swapped the stock open differential with an LSD (Limited Slip Differential) from a G70 6MT Sport (also found on ebay), at least I got to kill two birds with one stone.
View attachment 77488

View attachment 77490
All said and done, I probably have $800 in the Brembo conversion.

excellent, and thanks for the detailed story. you definitely scored, even if the job was a pain, since all that is behind you now. what brand is your sway bar(s)? I find the 2.0l to be nimble on the oem sways compared to the 3.3l and have no plans to go aftermarket sways.

 

[Volfy]

excellent, and thanks for the detailed story. you definitely scored, even if the job was a pain, since all that is behind you now. what brand is your sway bar(s)? I find the 2.0l to be nimble on the oem sways compared to the 3.3l and have no plans to go aftermarket sways.

I chose 2.0T primarily because it's a better teaching tool for introducing my son to performance driving - and to re-acquaint myself since my college days. Higher HP would certainly be a lot more fun, but a moderately powered car helps the learner concentrate on the real aspects that makes one a faster driver - maintaining momentum, holding the proper line, setting corner entry speed, proper brake/throttle timing, judging car's cornering attitude, etc. etc. None of which has anything to do with raw HP. Becoming a fast driver means you'll be fast in any car. Having a fast car just means you'll be fast in that car.

It's even more so with motorcycles. My track bunny is an old '05 Gixxer 600. It is far better tool at the track than my road bikes with wayyy more HP.

Anyhow, the swaybars. Our G70 and Stinger have identical chassis tuning - Eibach Pro kit lowering springs and Whiteline anti-roll bars on stock end links. I just ordered a rear camber link for the Stinger, because I'm maxed on our rear camber adjustment. I may eventually go whole-hog and replace all four rear suspension links, which I suspect would help with the rear end vagueness when the pace quickens. There are some thick rubber bushing that wobble around a lot at high lateral Gs.

I keep digressing... I like and trust Eibach at lot, but I went with the Whiteline bars because:

1. They re-use the OEM brackets. Eibach uses their own brackets, which have a grease nipple built-in, which is nice. However, from what guys have reported, the way the bolts are installed makes it difficult to R&R. The stock rear brackets are already a PITN, especially on the left (fuel filler) side. I'd rather not have it any more PITN. I installed grease nipples on the stock brackets, so mine are better in everyway than the Eibach.

2. They come with positionable end stops. Eibach has built-in stops, but I've read folks say they don't always center the bars correctly.

3. They are less expensive. Big +.

4. They come in an understated light grey color. Same reason I like the black Eibach springs.





IMO, chassis tuning should be in the following order:

1. Reducing unsprung mass. That means lighter weight wheels (and tires). OEM Stinger 18x8 wheel weighs 30 lbs. G70's 19x8 and 19x8.5 are 34.0 and 34.5 lbs. Our Enkei 18x8.5 are 20lbs each. Less unsprung mass take less spring and damping force to control; less rotational inertia means faster accel/decel. Along with better tires, this mod has far great impact on handling response than any other.

2. Lowering/stiffer springs. These more profound impact on chassis dynamics than just anti-roll bars. They control not only suspension control at each corner independently, they also lessen brake dive and accel squat (pitch axis), as well as cornering lean (roll axis). Typically, lowering springs need to be also stiffer to compensate for the reduced suspension travel. The Eibach are about 10% stiffer both front and rear. To my surprise, I have found that not all brands of Stinger lowering springs are that way.

3. Anti-roll bars. Although their namesake makes their function rather self-explanatory, I added them to both cars primarily to introduce a measure of control to the car's overall cornering attitude. As is, Both Stinger and G70 tend to understeer on corner entry, having adjustments on the anti-roll bar should help tune some of that out.

I'll skip the downside on this go-around. Folks are probably getting tired of my long spiels and digressions.

 

[RM7]

I disagree with the order of the springs, you basically have excessive undamped movement in both directions, which will reduce traction. There's no free lunch, lowering springs mean a stiffer spring rate to keep from bottoming. You will have stiffer suspension, but it will break loose easier too. I see cars all day in autoX leaning all over the place...but not breaking traction. I see stiff cars doing the opposite too. Lowering springs and not adjusting damper rates to match means excessive wheel movement. You won't "see" this very much with the naked eye, as you correctly describe the reduced body roll/squat, etc., but as surfaces are never perfect, the hard you go and push over these irregularities will cause you to break loose earlier, as compared to not messing with spring rates OR also increasing the damping rates. I had a nice setup with my BMW 4 series because I had the electronic shocks and not only could I put them on a stiffer setting, I had an aftermarket Dinan tune for the electronic suspension that made it even stiffer...which in that case did pair well with the ACS lowering springs. IMO, you only put on lowering springs by way of coil-overs or adjusting the damping rates. Otherwise, you really aren't gaining anything and just decreasing the performance. It "seems" more aggressive, but during quick maneuvering and G-limits, you're lowering the traction limit.

Swaybars are a mixed bag. Helping to not transfer excessive weight/cause roll and liftoff from the inside tires is an obvious plus for turning, but stiffening the rear often is at odds with putting power down. I would still 100% add them to this car (like I did), but just realize that they aren't necessarily a sure shot for everyone when racing AutoX. Lot of people simply think they need "these stiffest sways" and that's one that can make you slower if it's too stiff.

And tires and wheels, yep. Get the smallest widest wheels you can with the smallest profile and width tires that normally fit it. For practicality reasons you can't necessarily put 11s with 285s on there, but you want a stiff sidewall, which means you need wider wheels to support a decent width tire.

Some of the "big wheels" trends are just out of control IMO.

 

[Snicklefritz]

I'll skip the downside on this go-around. Folks are probably getting tired of my long spiels and digressions.

only if they are not interested in which case your not talking to them. I appreciated the pictures as well.

having @RM7 weigh in is pretty cool as this could turn into an informative discussion. I do not track my cars but am fascinated with the madness of trying to stay on a narrowing ribbon of asphalt and concrete while going faster. why do drivers do it? 'because it's there' like the mountains for another brand of madness.

 

[Volfy]

I disagree with the order of the springs, you basically have excessive undamped movement in both directions, which will reduce traction. There's no free lunch, lowering springs mean a stiffer spring rate to keep from bottoming. You will have stiffer suspension, but it will break loose easier too. I see cars all day in autoX leaning all over the place...but not breaking traction. I see stiff cars doing the opposite too. Lowering springs and not adjusting damper rates to match means excessive wheel movement. You won't "see" this very much with the naked eye, as you correctly describe the reduced body roll/squat, etc., but as surfaces are never perfect, the hard you go and push over these irregularities will cause you to break loose earlier, as compared to not messing with spring rates OR also increasing the damping rates. I had a nice setup with my BMW 4 series because I had the electronic shocks and not only could I put them on a stiffer setting, I had an aftermarket Dinan tune for the electronic suspension that made it even stiffer...which in that case did pair well with the ACS lowering springs. IMO, you only put on lowering springs by way of coil-overs or adjusting the damping rates. Otherwise, you really aren't gaining anything and just decreasing the performance. It "seems" more aggressive, but during quick maneuvering and G-limits, you're lowering the traction limit.

Swaybars are a mixed bag. Helping to not transfer excessive weight/cause roll and liftoff from the inside tires is an obvious plus for turning, but stiffening the rear often is at odds with putting power down. I would still 100% add them to this car (like I did), but just realize that they aren't necessarily a sure shot for everyone when racing AutoX. Lot of people simply think they need "these stiffest sways" and that's one that can make you slower if it's too stiff.

And tires and wheels, yep. Get the smallest widest wheels you can with the smallest profile and width tires that normally fit it. For practicality reasons you can't necessarily put 11s with 285s on there, but you want a stiff sidewall, which means you need wider wheels to support a decent width tire.

Some of the "big wheels" trends are just out of control IMO.

As with any tuning, there are the good, bad, and ugly.

I agree that the vast majority of "what's the widest wheel/tire I can fit" stuff is purely for looks and are almost always a detriment to handling and even to traction. This is why I mentioned nothing about size in my post above. I just said reducing unsprung weight and reducing rotational inertia. Light makes right. You are correct that is almost always achieved with the smallest diameter wheel that'l fit over the brakes. That is why I went with Enkei 18x8.5. However, going with the smallest profile tires is not always best, for the exactly same reason having too stiff springs is not good. Suspension control requires some degree of compliance. That compliance can be in the tire and/or in the spring/damper. That compliance helps to maintain tire adhesion over road surface undulations. Too soft/stiff a spring, too soft/stiff a damper, too soft/stiff a tire sidewall can all be a detriment to handling and traction.



I wrote a piece on G70 forum that explain this in more detail: 22 G70 / Stinger AWD Lowering Spring Install Review / Video The key to proper tuning is knowing what changing one parameter affect chassis response overall. It isn't easy and that's what make it a challenge... and fun.

Besides, there isn't a single BEST way to tune a chassis. Different mfrs have different philosophies and methodologies, each with its advantages and drawbacks. No free lunch is right.

 

[RM7]

As with any tuning, there are the good, bad, and ugly.

I agree that the vast majority of "what's the widest wheel/tire I can fit" stuff is purely for looks and are almost always a detriment to handling and even to traction. This is why I mentioned nothing about size in my post above. I just said reducing unsprung weight and reducing rotational inertia. Light makes right. You are correct that is almost always achieved with the smallest diameter wheel that'l fit over the brakes. That is why I went with Enkei 18x8.5. However, going with the smallest profile tires is not always best, for the exactly same reason having too stiff springs is not good. Suspension control requires some degree of compliance. That compliance can be in the tire and/or in the spring/damper. That compliance helps to maintain tire adhesion over road surface undulations. Too soft/stiff a spring, too soft/stiff a damper, too soft/stiff a tire sidewall can all be a detriment to handling and traction.

View attachment 77498

I wrote a piece on G70 forum that explain this in more detail: 22 G70 / Stinger AWD Lowering Spring Install Review / Video The key to proper tuning is knowing what changing one parameter affect chassis response overall. It isn't easy and that's what make it a challenge... and fun.

Besides, there isn't a single BEST way to tune a chassis. Different mfrs have different philosophies and methodologies, each with its advantages and drawbacks. No free lunch is right.

Yeah, I don't mean stretching tires, like with no sidewall, I mean within the range for the tire width that the tire mfr recommends. Typically the skinniest within *that* range is ideal for sidewall integrity and handling, without going to the over-stretching thing.

 

[Volfy]

Yeah, I don't mean stretching tires, like with no sidewall, I mean within the range for the tire width that the tire mfr recommends. Typically the skinniest within *that* range is ideal for sidewall integrity and handling, without going to the over-stretching thing.

You mean: "within the range for the tire width that the wheel mfr recommends"?

On our AutoX/Track set, I went with 245/40R18 Kumho V730 on TFR 18x8.5, for very similar reasons to what your described. It has worked well this whole last season and we've been quite happy with it. That said, there is always room for trials and experimentation. This set still has enough tread left and will probably do okay this season, but it's obvious they've heat-cycled substantially and no longer as sticky as when they were brand new. On the last AutoX a week ago, the ambient temp was low enough they were slip sliding around a good bit for the first 2 runs. I think they'll do better going into the Summer, but that's about it.

After that, I'm thinking about switching to 255/35R18. Kumho under-rated the width of the 245/40R18. They are frankly as wide as the 255/40R18 A/S tires we have on the G70 now and actually a bit taller. Not uncommon for tire mfrs to do that on their 200 tread wear lines, probably to help skirt SCCA rules.

255/35R18 should help reduce the sidewall height a bit, which will help lower the ride height of the car, without reducing suspension travel. Because these are dedicate track tires, we don't much care if the speed calibration is correct.

Speaking of performance tire sizing, I see that you also have a 2SS 1LE. There were several of them at the AutoX here. They look like they were running 19" wheels with reduced diameter tires. Exactly what I would do if I had that car. I've never really cared for the old American muscle cars with big V8, but I do like that 6th gen with the 1LE. GM made a concerted effort to reduce weight on this platform and turn it into a genuine sports car. Weight distribution with the 6.2L is a very respectable 53:47 and the curb weight is about the same as the inline4 Stinger. That is just phenomenal. If I were to have a dedicated track tool, that would be on top of the list. I might get one in a few years, just to check that box, before emissions and EVs kill them all.

 

[StingertimeNC]

I'm surprised to hear the Hawk pads didn't do well enough to your liking. They are quite well known in SCCA circles.

Stinger/G70 are an uncommon sight at AutoX and especially Track Days. Probably because they are not the best track bunnies, but with a bit of work, they do well enough to be a barrel of fun. Yes, it's great share notes.


Please PM me, I can't seem to find a way to PM, maybe because I haven't posted enough?

 

[StingertimeNC]

whoops, meant to add to the above. Hawk HPS 5.0 pads are great, perfect for aggressive street, just not quite enough for a fast track. I had no issues other than I just couldn't get comfortable braking from 140 at the end of a long straight. Too much give in the brake pedal. They handled fine for the most part though and it was the second time I ran these pads at this track.

Hawk makes a ton of aggressive pads for the track, some of those options would have likely been great. I was hoping I could run something at the track that was also acceptable for the street, and I can, just not balls to the wall at the track, IMO.

I do have high temp brake fluid in the car too.

GLOC R10's did pretty well the first time around, so I'm stepping it up to the next most aggressive GLoc option as recommended by KNS Brakes, my pad and rotor supplier.

 

[RM7]

You mean: "within the range for the tire width that the wheel mfr recommends"?

On our AutoX/Track set, I went with 245/40R18 Kumho V730 on TFR 18x8.5, for very similar reasons to what your described. It has worked well this whole last season and we've been quite happy with it. That said, there is always room for trials and experimentation. This set still has enough tread left and will probably do okay this season, but it's obvious they've heat-cycled substantially and no longer as sticky as when they were brand new. On the last AutoX a week ago, the ambient temp was low enough they were slip sliding around a good bit for the first 2 runs. I think they'll do better going into the Summer, but that's about it.

After that, I'm thinking about switching to 255/35R18. Kumho under-rated the width of the 245/40R18. They are frankly as wide as the 255/40R18 A/S tires we have on the G70 now and actually a bit taller. Not uncommon for tire mfrs to do that on their 200 tread wear lines, probably to help skirt SCCA rules.

255/35R18 should help reduce the sidewall height a bit, which will help lower the ride height of the car, without reducing suspension travel. Because these are dedicate track tires, we don't much care if the speed calibration is correct.

Speaking of performance tire sizing, I see that you also have a 2SS 1LE. There were several of them at the AutoX here. They look like they were running 19" wheels with reduced diameter tires. Exactly what I would do if I had that car. I've never really cared for the old American muscle cars with big V8, but I do like that 6th gen with the 1LE. GM made a concerted effort to reduce weight on this platform and turn it into a genuine sports car. Weight distribution with the 6.2L is a very respectable 53:47 and the curb weight is about the same as the inline4 Stinger. That is just phenomenal. If I were to have a dedicated track tool, that would be on top of the list. I might get one in a few years, just to check that box, before emissions and EVs kill them all.

Naw, the tire mfr is better IME because they account for their slightly different sizes, so like a 295 michelin might be recommended for 10, but not a goodyear. The tire mfr is the best to go to IME

 

[Volfy]

whoops, meant to add to the above. Hawk HPS 5.0 pads are great, perfect for aggressive street, just not quite enough for a fast track. I had no issues other than I just couldn't get comfortable braking from 140 at the end of a long straight. Too much give in the brake pedal. They handled fine for the most part though and it was the second time I ran these pads at this track.

Hawk makes a ton of aggressive pads for the track, some of those options would have likely been great. I was hoping I could run something at the track that was also acceptable for the street, and I can, just not balls to the wall at the track, IMO.

I do have high temp brake fluid in the car too.

GLOC R10's did pretty well the first time around, so I'm stepping it up to the next most aggressive GLoc option as recommended by KNS Brakes, my pad and rotor supplier.

That makes sense.

The tracks around here are mostly technical tracks without really long straights where you can build speed. The only exception was Texas World Speedway, but they closed. I never like that track anyway, especially on 2 wheels. I doubt I got much above 100mph on the MSR Cresson 3.1mile I ran. Maybe some of the big HP cars did.

I think even Bluestuff might have trouble scrubbing off big speeds like what you described. EBC has several higher classes of pads compounds that might take even higher heat range better, but IMO at some point, you are going to run into thermal capacity limitation of the stock Brembo brake size. Going to larger brakes might be the way to go.

I prefer shorter more technical tracks. Fun, to me, is to be had in the corners. This is especially true on two wheels. If there weren't any twisties, I'd probably sell all my road bikes. Cornering is a finesse sport, and I find lateral Gs far more satisfying than straight line speed. Cost far less too.

 

[RM7]

You mean: "within the range for the tire width that the wheel mfr recommends"?

On our AutoX/Track set, I went with 245/40R18 Kumho V730 on TFR 18x8.5, for very similar reasons to what your described. It has worked well this whole last season and we've been quite happy with it. That said, there is always room for trials and experimentation. This set still has enough tread left and will probably do okay this season, but it's obvious they've heat-cycled substantially and no longer as sticky as when they were brand new. On the last AutoX a week ago, the ambient temp was low enough they were slip sliding around a good bit for the first 2 runs. I think they'll do better going into the Summer, but that's about it.

After that, I'm thinking about switching to 255/35R18. Kumho under-rated the width of the 245/40R18. They are frankly as wide as the 255/40R18 A/S tires we have on the G70 now and actually a bit taller. Not uncommon for tire mfrs to do that on their 200 tread wear lines, probably to help skirt SCCA rules.

255/35R18 should help reduce the sidewall height a bit, which will help lower the ride height of the car, without reducing suspension travel. Because these are dedicate track tires, we don't much care if the speed calibration is correct.

Speaking of performance tire sizing, I see that you also have a 2SS 1LE. There were several of them at the AutoX here. They look like they were running 19" wheels with reduced diameter tires. Exactly what I would do if I had that car. I've never really cared for the old American muscle cars with big V8, but I do like that 6th gen with the 1LE. GM made a concerted effort to reduce weight on this platform and turn it into a genuine sports car. Weight distribution with the 6.2L is a very respectable 53:47 and the curb weight is about the same as the inline4 Stinger. That is just phenomenal. If I were to have a dedicated track tool, that would be on top of the list. I might get one in a few years, just to check that box, before emissions and EVs kill them all.

And yeah, the SS 1LE is an amazing track car that doesnt suck at autoX. I wish they came with 19” standard, like the ZL1 1LE does.

Its not a muscle car IMO, its a balanced car with the suspension and rubber that should accompany a v8. Its so much fun to race. I won my class in it the year before (out early last year due to injury).

 

[Volfy]

Naw, the tire mfr is better IME because they account for their slightly different sizes, so like a 295 michelin might be recommended for 10, but not a goodyear. The tire mfr is the best to go to IME

Let me try again: "within the range for the tire width that the tire mfr recommends for the wheel rim width you have"?

I think I got it right this time. Like this:


This is, of course, spot on correct... when you are picking tire to fit over an existing wheel.

Depending on which part of the tuning process we are talking about, this decision may not come first. My original post you first replied to was talking about reducing unsprung weight and rotational inertia from an OEM setup. At that point of the game, the first decision should focus on selecting the aftermarket wheel for best fitment, with optimum diameter/width/offset, and to maintain factory scrub radius.

Afterall, wheel selection is where you'll net the most gain on weight savings. For me, that was a whopping 14 to 14.5 lbs per wheel.

Only after that selection is done should you start considering tire choice. There might be an iterative process that goes back and forth a bit, but tire choice is a secondary consideration after wheel selection.

 

[Volfy]

And yeah, the SS 1LE is an amazing track car that doesnt suck at autoX. I wish they came with 19” standard, like the ZL1 1LE does.

Its not a muscle car IMO, its a balanced car with the suspension and rubber that should accompany a v8. Its so much fun to race. I won my class in it the year before (out early last year due to injury).

Spot on!

I catch a lot of crap when I told G70 owners I got rid of the stock 19' wheels and went to 18". I would go through the whole technical discussion that explains why that is the optimum decision for performance. Invariably, I get a grudging acknowledgement, with a parting shot: "but 18" looks like s***."

Yeah... I'm a form following function guy. What works right... looks right to me. Not the other way around.

Had I known back then about the ZL1 1LE 19" wheels drop from the normal trim with 20", that would've vindicated my call far easier than all that boring tech talk.

 

[RM7]

Let me try again: "within the range for the tire width that the tire mfr recommends for the wheel rim width you have"?

I think I got it right this time. Like this:

View attachment 77502
This is, of course, spot on correct... when you are picking tire to fit over an existing wheel.

Depending on which part of the tuning process we are talking about, this decision may not come first. My original post you first replied to was talking about reducing unsprung weight and rotational inertia from an OEM setup. At that point of the game, the first decision should focus on selecting the aftermarket wheel for best fitment, with optimum diameter/width/offset, and to maintain factory scrub radius.

Afterall, wheel selection is where you'll net the most gain on weight savings. For me, that was a whopping 14 to 14.5 lbs per wheel.

Only after that selection is done should you start considering tire choice. There might be an iterative process that goes back and forth a bit, but tire choice is a secondary consideration after wheel selection.

Yeah, although I weighed my 18x8.5 enkies and OEM 18x8s and the difference wasnt dramatic, with tires mounted about 5lbs lighter per, not bad considering its a wider tire than OEM. Also lighter due to no run flat BS, so not really much weight saved in the rim. Probably a few lbs and a combo of both the tires and the rim.

Another 1.5 lbs overall for lighter lugnuts.

For sure its the best place to save weight tho.

I was really concerned about the offset and running 255 up front, but having changed wheels several times now, no marks. I was measuring with a mirror and everything looked good initially, but you know, stuff can flex. I think 19s would buy a little more space for 255s because the rim would be further from the strut up higher, but i wanted to fit 18 if i could…and it worked.

Kind of opposite to my 1LE and dry handling though, i went with more sidewall and high performance AS on purpose, because sidewall flex improves handling in wet, thinking that if its just pissing rain and i signed up for an autoX id bring the stinger instead. Hasnt happened yet tho.

 

[Volfy]

I'm not sure why OEM wheels these days are so heavy. For every day driving the Stinger, I'm running the same 18x7.5 wheels that were on my '09 Genesis sedan. I was rather surprised they weight 23 lbs, compared to Stinger's 30 lbs OEM 18x8. You wouldn't think 14yr old rims would be an upgrade, but they weight less and ride better. Whatever sidewall rigidity I'm giving up by switching to 0.5" narrower rim, it is more than made up for in enhanced tire compliance. Along with the 7 lbs per corner less unsrpung weight, suspension control is more responsive and they give the Stinger a magic carpet ride feel that the stock 18x8 just couldn't match.

My only guess is that the disturbing trend of ever lower profile tires is forcing mfrs to overbuilt the OEM wheel, in an attempt to survive pothole strikes. Back in its day, these old Gennie wheels were shod with 50 series tires. Nowadays, 35 series are not at all uncommon. Lots of performance cars come with 30 series tires. Progress... I guess.