RWD, want to maximize Acceleration grip.

[StingertimeNC]

Ok gang, looking for some sound advice. I've been thinking about what tire size to move up to, but I don't want to get so wide that I end up with worse acceleration grip. In general, my understanding is wider tires help with lateral grip, but may not be so helpful with acceleration and braking as the front to back contact patch is shorter. I currently have stock Pilot PS4 19" tires, but on my new 8.5 wide front and 9.5 wide rear tires. so 225x40 19" up front and 255x35 19" rear. Vossen, the wheel manufacturer suggested that I can stay with stock tires, which I did as they only had a few k miles on them, or go up to a max of 245's in the front and 275's in the rear. I'm RWD so traction is somewhat of an issue at launch. I currently have the JB4, running map 2, and will be adding meth soon.

I could also go with 235's in the front and 265's in the rear. I'm not in love with the stretch look, although I can live with it as is. So, go up to the largest size tire I can, or split the difference and go up only one size. pick up a little lateral grip, but maybe lose a bit of acceleration grip in the process. Or, will the two up-size options not even really have much of an effect either way?

 

[Houstinger1]

FWIW, I went with 245 up front and 275 in the back. It pokes a little bit, but not much. What's strange is after I got the wider wheels, it looks like it needs to be lowered now more so than it did before. With your springer, it should look very nice and give you more traction. I did go ahead and get new tires at the same time and went with the PS4S so I can't comment on one vs the other providing the best upgrade in traction.

 

[Oryan]

The stock tires on wheels that wide are gonna stretch to some degree. 235/265 should be fine and 245/275 will most certainly not stretch and give more of a meaty look. As far as wider meaning more grip...Yes, to a point. The actual tire compound itself matters as well. Getting more sidewall with a higher tire profile can help the tire absorb the initial torque shock and reduce spinning on launch. PS4 or PS4S should be fine but there's other tires that can do more in terms of pure straight line grip.

Next, suspension. You want a suspension setup that enables weight to transfer to the rear of the car over the rear wheels on launch. Coils that you can adjust would be a good start, but most lowering springs for the car happen to have spring rates that help. Subframe braces help with wheel hop on launch. Bracing the differential or differential bushings can reduce driveline slop and help the car more cleanly get out of the hole.

Beyond that is tossing some slicks on the back or going all-out radials if you can fit them over the brakes, if you're willing to go that far.

 

[StingertimeNC]

Thanks for the thoughts. so right now I have Ark Springs, the ones with the least amount of drop. the car definitely transfers the weight to the rear under hard acceleration. I agree that there's probably better suspension solutions if I'm really serious. I do have the BMS diff brace and that seemed to help noticeably. Winter is here and although I live in NC, it's still pretty nippy right now so the PS4's are fine for mild acceleration, but can't really get on it until about 40mph or so. It's above 45f for most of the year so tires are pretty great most of the time. I'll stay with PS4S most likely. just can't find much hard data. So if Kia thinks the best fit was the stock size, and then we add power, are we better off adding a little tire too? I understand the RWD is always going to be the biggest issue for off the line acceleration, but can it be just a little better??

 

[Oryan]

Summer tires aren't gonna be grippy while it's cold out. I don't think there's anything we can do about that until it warms up.

 

[StingertimeNC]

Summer tires aren't gonna be grippy while it's cold out. I don't think there's anything we can do about that until it warms up.

yes, of course. wish I could get some input on the 255/265/275 as far as acceleration goes, assuming it's summer. if I go wider am I losing acceleration benefit?

 

[AWDGT2]

Tim, your backwards on What you understand pertaining to wheel width. It's actually the opposite.... A wider tire in fact reduces lateral grip but increases forward grip (acceleration). Go Wide!!! for RWD cars only, I would recommend a 9.5" wide wheel with a 275x35 or 275x40 on an 18" rim as opposed to the factory 19. Make up the height difference in tire and not rim. Rubber weighs less than metal or aluminum. For AWD guys I will preach to the cows come home about a square setup. Advantages so outweigh the disadvantages, but for RWD guys you almost have to go with staggered. I have a ton of research on wheel and tire combinations that go way beyond this thread, but front wheels can be tricky if you dont understand wheel offset. This is a good article to support my claims Wheel Tech, Part II: Width Matters | Tuner University

 

[StingertimeNC]

Darrin, ok, so I have the 19" rims on the car already (aftermarket) so I'm staying with those. you are saying go with the 275's then. that's essentially the largest tire I can get with the offset I have. it was my understanding that the front to back contact patch is more important than the lateral contact patch. I read somewhere that a larger diameter wheel is also better for acceleration as that makes the front to back contact patch larger. (added weight obviously causing other issues) I'm going to check out the article! thanks D!

 

[StingertimeNC]

so, I checked out the article, and this is what I was trying to say originally:

"Wider wheels will give you a more rectangular patch, while thinner wheels will give you a narrow yet longer more square patch. The thinner wheels will therefore be better (and of course there are extremes in both cases) for straight line acceleration and braking. The wider ones, because of the direction of the forces on the tire tread in the corners, will be better for cornering at the expense of some straight line acceleration."

So, if I go by this, I may be better off staying at the stock tire size of 255 x 35 in the rear. I definitely wanted to add a little tire width just so there's a little less stretch, but this may cause me to lose acceleration grip. Maybe I'll just get Michelin sport cup 2's! LOL.

 

[oddball]

Slicks or drag radials.
Anything else is just window dressing. Do whatever you like.

 

[Travis Wills]

There is a lot of great discussion here. I just wanted to add my two cents. Temperature affects traction more than people realize with these “summer only tires”.

If you can only choose one method of improving traction you should choose raising the temperature every time. These tires lose pretty much all of their grip around 40 degrees F. However, they still lose significant grip even above that temperature.

I honestly believe you would be better off buying a tire warmer than going a centimeter or two wider in tires. Going wider in colder temps just gives you more of a tire that won’t grip.

Also torque is what is breaking the traction. Limiting torque in first and second gear is definitely what all of the tuning companies have been recommending to improve traction.

You can also change the effective gear ratio to reduce or even increase torque for the AWD guys. Just changing the outside tire diameter can change the overall gear ratio.

For RWD cars going up to a heavier 20” wheel and tire combination might actually help traction even if the tire is not wider. However, you will throw off the speedometer if you change the overall diameter significantly.

For the AWD guys going with a lightweight 18” wheel with a thicker tire may still have the same overall diameter but the lighter wheel can effectively act like an increase in motor torque.

With my RWD Stinger completely stock I really didn’t have significant traction issues. However, once I increased air flow and torque I immediately started having massive traction issues. I almost put it in the wall at the track because it was spinning so much all of a sudden.

Now I make sure I heat the tires up as much as possible and that helps to some extent. There really isn’t much you can do if it is really cold out unless you have tire warmers or something like that.

 

[StingertimeNC]

Thanks for the comments. so I think I may just go to a 265x35, 19 in the rear. adding 10mm of width versus 20mm with the 275mm. I did shave off 8 pounds per wheel versus stock and stayed with 19's. same weight pushing down will result in a marginal traction reduction but I need a little more meatier look. Going to stay with Summer tires as NC is pretty mild most of the year. winter does suck but 8-9 months out of the year will be pretty good!

 

[G70 Owner]

When temperature enters the discussion I always like to point to this video to show actual testing on summer tires grip levels in different temperatures and wet vs dry: