Janus00

Has anyone seen this article before?

http://www.tuneruniversity.com/blog/...-size-matters/

Everyone seems to want to run wider tires (hence wider wheels), but my roommate states that wider tires will actually affect handling negatively.

I know many people run larger and wider tire sizes all the time (mostly for more traction in high HP applications), but does it actually make the car unsafe?

Would it even be worth running larger width tires with anything other than much higher HP/tq than stock?

I do plan on going FI eventually, but it may be years before that point.

Manga_Spawn

Yes. It has been shown that wider wheels and tires do result in faster lap times. That's not to say there isn't downsides. Your wheels and tires should go along with the purpose of the car.

s2000Junky

No argument from me, ive been one of the bigger proponents on this forum of the wider package. Ive experienced nothing but benefits as far as im concerned.

Wide tires are for generating more lateral adhesion primarily and the wider rim is there to support or even slightly pre load the wall of the tire to retain good handling precision through maintaining tire shape wile G loading, and so a wide tire and wide rim should be properly sized together to get the full and proper benefits. This is the primary focus rather then strait line grip or breaking. There is a residual benefit in those areas as well but secondarily to lateral grip. So hp doesn't quite have the importance some people like to place on this, with in regard to s2000. It makes plenty of power to run efficient with 295+ with stock realm power.

Tire compound has a drastic effect on grip level as well, but on a street car it makes more sense to run a non track compound tire that is wider to move the compromises. There is usually some compromise somewhere, its just a matter of where you place it and in order to know how/where to do that is to understand what the goal/use of the car is. Moving outside of the typical 9"/255 wide package to a 11.5"/295 in rear was probably one of the best single performing modifications ive done, not only in grip, but in handling/stability which translated to a more confident, planted rear of the car. Something the s2k needs improvement in from the factory, certainly in the ap1. I think a 10"/255 up front is a well balanced width option. Ive seen as high as 285 up front on a dedicated semi pro auto x S2000.

Keep in mind the weight of the vehicle as well for tire width. A heavier car places more load and heat generation on a tire. A wider tire runs cooler/more consistent, and too wide a tire may never get up to proper peak operating temp. Ive never found that threshold on an s2k yet. I think a 315 in the rear is totally reasonable for a near stock weight stiff sprung s2k. So there is a balance. The S2k is not a tank, but its no feather weight either at a typical 2900-3000lb with driver. There are a lot of high performing sports cars/super cars in the 3000-3300lb range that run tires in the 300mm width range+. Its not just about holding hp. A taller rather then wider tire works better at that single purpose anyway.

riceball777

i love my 295 tires on my s2000. The difference in both straight line grip and lateral gripe is huge. If i ran a standard 255/40/17 extreme performance street tire i would have no traction in the first 4 gears and my car would be much more dangerous to drive. My car is way safer to drive because of the 295 tires compared to stock size.

Chance S2K

The only real potential "downside" that anyone would ever really face is by adding width to the rim/tire you're obviously also adding rotational mass which adds weight and slows the car down in a straight line.


Assuming your tires are all aligned and matched/set up correctly though, the added traction and stability you get while planted on the ground more than make up for it. I'm turbo at only about 350WHP right now with some cheap Continental 225's up front and some 245 RE-11's in the back, and I can definitely attest to the importance of traction already. Breaking first and second gear loose is all too easy.

That's part of what makes driving my car fun though, since I'm not really trying to set fast lap times around town

Janus00

Thanks for your input guys. I talked to UrgeDesigns about it too, and they agree with all of you. I think there is a point of diminishing returns, but none of us ever reach that point. That said, I can't wait for wider tires.

Car Analogy

That article that was linked is correct in that wider tires dont increase contact patch, they just change its shape. Contact patch size is dependent on weight of that corner of car and tire air pressure. Wider tires won't increase the square footage (inchage?) of the patch.

Wider tires will make the patch shorter front to rear, but wider left to right. Generally, better for cornering, not as optimized for acceleration or braking (but if its a road course or autocross, both acceleration and braking will overlap some with cornering, so its likely wider tires will also seem to have better stoping and going traction.)

Sent from my SM-G920P using IB AutoGroup

RedCelica

The article makes some valid points. Going more than 1" wide with tires to match without adjusting the suspension and/or adding more rotational mass is going to lessen the performance advantages. Even still, the juice is definitely worth the squeeze until the law of diminished returns comes into fruition.

s2000Junky

Yep, and I cant clearly say where those diminishing returns starts to factory in yet myself. I still can overheat my rear 295 at the road course about 3rd session in, and I'm just running typical NA bolt on power so that's not really a factor like some people think. The overall un sprung weight is still close to factory, running light wheels so that keeps me above water as far as diminishing returns go with that aspect, but I think the stock motor has plenty of power to 'maintain' a higher rate of speed overall with the added grip generation in the turns, which is the name of the game after all. It is more or less a momentum car anyway, until you get into FI game. I'm toying with the idea of moving to 315 in the rear NA. I have a strong suspicion that the threshold of diminishing returns will still not have been reached. Camber alignment and proper spring rates are a key element into getting the rubber to work effectively no matter what width it is. Obviously the wider the tire, the less camber you want if you are to maintain a more even heat across the section width, which is important.

ZDan

I think the grip benefits of wider tires is often overestimated and overstated. Particularly on the street where wider tires may not ever get near optimal operational temperatures and may give *less* grip. Even at the track I would bet that going from, say, 245s to 275s could be worth on the order of a couple to three of tenths a lap, depending. Hugely significant if you are competing and the competition is close! But for general HPDE usage, not that big a deal.

Here's a test Car and Driver did on same make/model (but two different compounds, speed ratings, and wear ratings) tires of different sizes on a VW GTI:
http://www.caranddriver.com/features...d-tires-tested

V-rated, higher treadwear rating compound:
195/65-15 0.83g
205/55-16 0.85g
225/45-17 0.85g

W-rated softer/lower treadwear rated compound:
225/40-18 0.89g (+.04g over same-width 225/50-16 attributable to different compound)
235/35-19 0.88g (very slight disadvantage of 235 vs. 225 possibly due to this tire being larger diameter, higher c.g.)

Lateral grip appears to be practically width-independent. Granted, those are M&S street tires. I would expect track tire grip to be a bit more width-dependent.

I've driven on a variety of tire widths and staggers at the track, and IMO subjectively there just isn't that much in it.

If tenths of a second at the track are critically important, yeah it matters and wider is better. But there will be diminishing returns. I.e., 255s will have a greater grip advantage over 225s than 285s will have over 255s. I would bet...