LSD = More traction control?

[rtv900]

it would be possible to get it to kick in with the winters on if I shifted, and then hammered the throttle.
But that's a pretty significant different being
a) a manual
b) supercharged so boost is essentially instantaneous
c) it wouldn't actually spin them anyway, but yes the TC 'could' be tricked by the soft tread rubber flex



Even paddle shifting in the stinger if you stomped the gas and downshifted to spike the rpm's it still puts that power down WAY softer going through a torque converter and all
I think you already know this and I know it doesn't solve the problem, but I'm pretty sure you have some sort of a TC malfunction going on
I mean my stinger is the 3.3 and I have narrow winters on it now and absolutely never get TC issues.

 

[Volfy]

I know it doesn't get to the bottom of your TC quirks, but I still think your simplest solution is not to do that in Comfort mode. Engaging Sport mode with a quick flick of that rotary dial. The only times where pulling the throttle wide open on public roads might be a NEED is passing (for example: on a two-lane road). Most other scenarios, it's more-or-less a driver's choice. Why not just flick it into Sport mode for that?

 

[7Andrei7]

@Volfy Yup, overtaking is the only moment when I might need to actually floor it. And that was how I discovered the problem. It was quite scary to have the TC cut power midway through an overtake. Now that I know it might happen, I can definitely live with it. But it still baffles me.
If I would have a custom mode it would be perfect. Everything in comfort but the TC in sport . Sadly, not an option on my car.

I've been reading on bmw forums and everyone confirms there is no software coding when they put in LSDs, even at the dealer. This further points to some kind of problem or glitch on my car, maybe caused during the Diff install but unrelated to the LSD.

 

[Thomby]

I can't believe that the car is able to spin both rear wheels at 120kph with only 245hp and 353nm of torque.

This almost certainly isn't happening. It must be detecting (or think it's detecting) a speed difference, either between the two rears or between the rears & fronts.

Any chance you have a difference in wheel/tire height vs. stock? Maybe it's close enough that in normal driving it's fine, but at higher speeds it's enough to confuse the trac control?

 

[7Andrei7]

This almost certainly isn't happening. It must be detecting (or think it's detecting) a speed difference, either between the two rears or between the rears & fronts.

Any chance you have a difference in wheel/tire height vs. stock? Maybe it's close enough that in normal driving it's fine, but at higher speeds it's enough to confuse the trac control?

No, everything is stock, including tire sizes. Tire pressure is also as required.

Even thread depth difference is minimal between the 2 axels. Less than 1mm.

 

[Volfy]

@Volfy Yup, overtaking is the only moment when I might need to actually floor it. And that was how I discovered the problem. It was quite scary to have the TC cut power midway through an overtake. Now that I know it might happen, I can definitely live with it. But it still baffles me.
If I would have a custom mode it would be perfect. Everything in comfort but the TC in sport . Sadly, not an option on my car.

I've been reading on bmw forums and everyone confirms there is no software coding when they put in LSDs, even at the dealer. This further points to some kind of problem or glitch on my car, maybe caused during the Diff install but unrelated to the LSD (Limited Slip Differential).

I cannot imagine any SW/FW changes being necessary for a purely mechanical LSD, like ours. For an electronic LSD that is controlled and activated by an ECU in concert with other subsystems on the car... sure, I can see needing SW/FW for sure.

FWIW, I just did an AutoX with the '23 2.5T. The mechanical LSD did it's job just fine. Standing start with WOT from the line (JB4 map1) was remarkably uneventful. Car tracked straight and no tire spins. I let my son have the Kumho V730 track tires, I was on our back-up (rain day) set of Bridgestone Potenza Sport. With TC/SC off, the tail end will step out, if I get on the gas too early coming out of corners, but the LSD can only help out so much. The driver still needs to learn to balance the checkbook between lateral and linear acceleration. That $10 worth of tire traction only goes so far. Try to cash more than $10, and the check will bounce.

For me, that's where the main value of the LSD lies - managing available traction over rear wheels on corner exit drive out, so I can roll in power just that little bit sooner. Might not sound like much, but worth every bit of the money and sweat I put in.

 

[Thomby]

No, everything is stock, including tire sizes. Tire pressure is also as required.

Even thread depth difference is minimal between the 2 axels. Less than 1mm.

I'm reaching here, but have you checked the alignment recently? Put the car up and yank on the suspension and subframe connections, check bushings etc?

I'm assuming you would've noticed anything egregious when you did the swap, but maybe an edge case where something shifts enough when you hammer it at speed to confuse the computers.

In a prior car, I had worn subframe bushings, which normally behaved but accelerating out of *just* the right turn I'd get wheel hop. Not fun tracking that down with how specific it was.

 

[7Andrei7]

I'm assuming you would've noticed anything egregious when you did the swap, but maybe an edge case where something shifts enough when you hammer it at speed to confuse the computers.

I did have an alignment done and then rechecked after the diff change. I wanted to be on the safe side.

It might be something in the suspension but I don't even know how to start checking. I'll probably take it to a shop for an inspection.

The next step is to check the speed sensors. I ordered an OBD reader and will take the car out to try and trigger the TC while a friend will look at the live data. I REALLY hope he will see some kind of abnormal behaviour in one of the speed sensors. It would be the easiest fix..

 

[Volfy]

Since you do not have this issue when the car is in Sport mode, only in Comfort mode, I find it difficult to imagine a faulty wheel speed sensor would be the culprit. My best guess is that Sport mode's TC/SC is less intrusive and more tolerant of differing rear wheel speeds. Stinger/G70 doesn't have a "Rain" mode. On vehicles that does have a "Rain" mode, like Mrs. Volfy's Fiat 500X, that is exactly what happens.

Some motorcycles go beyond just various "named" drive modes and actually have a scale that you can set TC aggressiveness (like from 1-3 or 1-7). You can go from extremely conservative and won't allow any slippage for riding in the rain, to full-on hooligan antics like wheelies, stoppies, and rear wheel drifts.

 

[7Andrei7]

I have incredibly fixed it!!!
It was...... the tires. I'm not yet sure how I'll approach it with Continental but here is what I did.

Using a professional OBD reader I did a few readings of ABS speed sensors. With my current winter setup, OEM spec 225/40R19 front and 255/35R19 rear with Continental TS860S on the OEM wheels I have a difference in speed read by the ABS sensors of approx 2 km/h while cruising at 80 km/h. If I floor it at higher speed, the difference between both rear wheels and both front wheels can spike up to 5-6 km/h. In those scenarios, the TC steps in and cuts power. This is the first video below.

Last night I decided to put my summer wheels on the left side, both front and rear. My summers are the same OEM spec Michelin PS4 on OEM wheels. Immediately I could see that the summers (left front and back) recorded the same speed while the winters recorded a 2 km/h difference (rear front and back).



Then, I put on the full summer set and went on the highway and did a few flat out accelerations from 80 to 150-160 km/h. The speed of every wheel stayed consistently within 1 km/h of each other. Needless to say, there was no TC intervention. Video below.

I'm pretty sure I've gotten to the bottom of it but here is still one pressing question: WTF Continental?!?
I will contact them and try to send out one front and one rear so they can professionally measure it and tell me what in the world is going on.
Opinions?

 

[Volfy]

All tires balloon to some extent at higher speeds. Winter tires have carcass and tread compounds that allow them to stay soft and compliant at very low ambient temperature. This helps traction under those condition, when the tires need to flex and conform to the road surface for better grip. Summer tire compound would become hard and brittle at very low temp. In fact, most tire mfrs warns against running their Summer tires under such conditions. Your Michelin PS4 states so: "Max Performance Summer tires are not intended to be driven in near-freezing temperatures, through snow or on ice." Doing so risk cracking and chunking tread blocks.

It is a compromise and not anything wrong with either types of tires.

 

[7Andrei7]

Ok, I understand how they work but I'd say it's absurd for the winter Continentals to balloon so badly that they are off by 2-3 km/h at cruising speed and by 4-5 km/h under acceleration, compared to the same model tires on the front axle.

Why are the fronts not ballooning at the same rate as the rears? I'm talking about at cruising, constant speed, not under acceleration.
The front winter tire has a smaller speed difference compared to the two summer tire than to the other winter tire. How does this make sense?

This can't be normal or otherwise you would all have flashing TC in your dash every winter.
I refuse to accept that this is normal behavior. Especially because this is my 5th winter with the car and the first one when I have TC cutting power when I'm trying to make an overtake. It's also the first winter with this exact set of tires.

 

[rtv900]

Ok, I understand how they work but I'd say it's absurd for the winter Continentals to balloon so badly that they are off by 2-3 km/h at cruising speed and by 4-5 km/h under acceleration, compared to the same model tires on the front axle.

Why are the fronts not ballooning at the same rate as the rears? I'm talking about at cruising, constant speed, not under acceleration.
The front winter tire has a smaller speed difference compared to the two summer tire than to the other winter tire. How does this make sense?

This can't be normal or otherwise you would all have flashing TC in your dash every winter.
I refuse to accept that this is normal behavior. Especially because this is my 5th winter with the car and the first one when I have TC cutting power when I'm trying to make an overtake. It's also the first winter with this exact set of tires.

you are right, it isn't normal. Something else has to be going on.
I have dedicated snows and don't have a lick of a problem at any speeds. I take it up to 120+ on the highway with those tires when it's clear out.

 

[7Andrei7]

I need to emphasize again this picture.
This is at normal, constant speed, 14 degrees celsius.

Left side wheels are summer, right side the winter. Notice the speed differences between the 2 winters. It looks like the front is slightly larger than the summers and the rear is slightly smaller.

At 120 km/h the difference is 3 km/h and if I suddenly accelerate the difference spikes to 5-6 km/h, enough to trigger the TC. At least this is my logic.

The summers never record a speed difference between themselves of more than 1 km/h, regardless of speed or amount of acceleration.

 

[rtv900]

At 120 km/h the difference is 3 km/h and if I suddenly accelerate the difference spikes to 5-6 km/h, enough to trigger the TC.

but 'suddenly' accelerating has nothing to do with the sensor recording a different speed. If the diameters were truly different the speed difference would progressively increase. But getting on the gas would not affect that unless you went from 60 to 120 in a tenth of a second.
If it's triggering when you hammer it the reason has to be the sensitivity and the flex in the rubber making the wheel 'think' it just slipped.

 

[Volfy]

Why are the fronts not ballooning at the same rate as the rears? I'm talking about at cruising, constant speed, not under acceleration.
The front winter tire has a smaller speed difference compared to the two summer tire than to the other winter tire. How does this make sense?

Quite possibly because the front tires are 225/40R19 quite well supported on 8" rims, while the rears are wider 255/35R18 mounted on 8.5" rims, which is towards the narrow end of recommended rim width. This means the rear tires are not as well supported, and combined with being wider means the rear tire can succumb to centrifugal forces easier than the front tires.

This can't be normal or otherwise you would all have flashing TC in your dash every winter.
I refuse to accept that this is normal behavior. Especially because this is my 5th winter with the car and the first one when I have TC cutting power when I'm trying to make an overtake. It's also the first winter with this exact set of tires.

Is tire ballooning "normal"? Absolutely. Some tires more than others. All ECU/TC have built-in tolerances that account for this in normal operations. To what degree a particular tire balloons and how much that ballooning might trigger ECU/TC fault... that I don't know.

Personally, I would've gotten some skinnier 18" Winter tires and just go easy on them. I certainly wouldn't want to go WOT at hwy speeds with Winter tires on, but that's me. If you insist on your car allowing you to do that without triggering ECU/TC faults, then you'll have to figure that out.

 

[7Andrei7]

 

[Volfy]

Yikes! I though 225/40 and 255/35 are supposed to have nearly identical overall diameter. Those two don't look any where close to similar OD.

 

[7Andrei7]

Yikes! I though 225/40 and 255/35 are supposed to have nearly identical overall diameter. Those two don't look any where close to similar OD.

Yup, something IS wrong.
Wrote to Continental earlier and hope they will reply and investigate.
Both have 2.5 bar pressure, as recommended.

 

[Ohiocruiser]

Looks like half inch of a difference. Not good at all.