Tires & Sizing to get the most grip

[bubbajan21]

Anyone else have opinions on the matter?

[einstein57]

I dont know what the hell i was thinking. Federals are super steel. lol. I've heard good things about the kumho xs line but the tire selection is not that great. I'm going to end up with some NT05s on my go fast wheels.

[bubbajan21]

What super sports are you talking about? I only know of one tire branded as Super Sports.

Michelin Pilot Super Sports. They are a replacement for the Michelin Pilot PS2.

http://www.tirerack.com/tires/tires.jsp?tireMake=Michelin&bPostID=post-id-d6283ebe-ff20-4d7d-807b-4a916fbe160c&tireModel=Pilot+Super+Sport

[einstein57]

Now that would be interesting if I could fit 245/40 17 in the back because in that case I could run the Super Sports! :D That would put me at 245/40 17 in the rear and either 215 or 225/45 17 in the front. Hmmm, that's a bit narrow in the fronts and I don't want to set this thing up to be a drag racer. If they only made the Super Sports in a 235/40 17 I would rock that setup in a second with the 245's out back. Hmmmmmm, I've got some thinking to do. :)

What super sports are you talking about? I only know of one tire branded as Super Sports.

[bubbajan21]

Well they make the better one too. Not hard to find. They list all available sizes on federals website

http://www.onlinetires.com/products/...g+90w+bsw.html

I appreciate it, but I'm not really looking for Federal Tires.

[einstein57]

That's a cheap federal tire, I'm looking for a Michelin Pilot Supersports tire.

Well they make the better one too. Not hard to find. They list all available sizes on federals website

http://www.onlinetires.com/products/...g+90w+bsw.html

[Apps]

Any more input on 235 front and rear PS2s vs. 215 front & 245 rear Super Sports?

FYI Super Sport is the replacement for the PS2. PS2 will be phased out completely in the upcoming years.

The size differences will give you differences in cornering stiffness and in effect the understeer or oversteer gradient of the car. Wider tires in general will have higher cornering stiffness (especially true if the tire line is the same as the structure of the tire internally is extremely similar).

You can account for the difference in corning stiffness with sway bars and spring rates to get back to neutral handling. Just something to think about.

[Apps]

So by this logic, are you saying I'd be able to get power to the ground better via a 215/45 17 Michelin Pilot Supersport than I would via a 245/45 17 Toyo R1R assuming the Supersport has a better chemical compound for grip??

Supersport being better than an R1R is a function of the conditions. As I said before heat cycles will change the tire, some slowly some more quickly. This will be a factor in continued traction if you are interested in longevity. I can not tell you which tire has more traction (both longitudinal and lateral) without a set of conditions. This leads into the reason all-season tires exist. American customers in particular want a tire that has a long wear life but can perform adequately in many conditions (snow, ice, dry, wet, cold, hot). This tire is far from optimized for any of these conditions. If you have multiple conditions you would like performance in you will always have a compromised tire. Are you looking for a single performance condition?

The logic of "if the pressure and load on the tire stay the same then the area in contact with the road will also stay same" can't be sound because I guarantee you if you have 2 tires with the same compound, same load, and same pressre next to each other, one with a 100mm width and one with a 300mm width, the wider tire will have substantially more grip as it may have the same contact area front to rear in contact with the road, but the width of the contact patch would be ~3 times wider. Aside from chemical makeups of tires, grip is to some extent a function of contact patch and there is no way you can convince me a 100mm wide tire has the same contact patch as a 300mm wide tire. I agree that chemical make-up of a tire is more important than the size of the tire, but to claim that "the amount of rubber in contact with the road does not vary based on size" seems far fetched to me.

How can you "guarantee" this. I presented only physics. I do not wish to try to convince you. You are choosing to ignore a physical property.

How are you measuring "grip" to say that "the wider tire will have substantially more grip as it may have the same contact area front to rear in contact with the road, but the width of the contact patch would be ~3 times wider?"

In fact the tire that is wider will have a wider contact patch (lateral) as you stated but it will also be shorter in the longitudinal direction. The area of contact WILL be exactly the same. a = f/p, force = load (stays the same in your example), p = pressure (stays the same in your example) so area must be the same.

[bubbajan21]

They do

http://www.onlinetires.com/products/...5+90v+bsw.html

That's a cheap federal tire, I'm looking for a Michelin Pilot Supersports tire.

[einstein57]

If they only made the Super Sports in a 235/40 17 I would rock that setup in a second with the 245's out back. Hmmmmmm, I've got some thinking to do. :)

They do

http://www.onlinetires.com/products/...5+90v+bsw.html

[bubbajan21]

Any more input on 235 front and rear PS2s vs. 215 front & 245 rear Super Sports?

[bubbajan21]

215's up front and 245's out back will defenitely effect handling. IMO sqaure is the way to go, maybe 10mm wider in back, but 30mm is a lot of rubber.

Where are you at in MI? Would love to check out your car sometime if your close-ish. Also if your into autoX at all there is an event at MSU this weekend I'll be at. Speaking of tires, I could show ya what 225 R-comps feel like haha.

I'm in Flint, but I don't have the S50 E30 here in MI, I have my E28.

[Nsquared97]

215's up front and 245's out back will defenitely effect handling. IMO sqaure is the way to go, maybe 10mm wider in back, but 30mm is a lot of rubber.

Where are you at in MI? Would love to check out your car sometime if your close-ish. Also if your into autoX at all there is an event at MSU this weekend I'll be at. Speaking of tires, I could show ya what 225 R-comps feel like haha.

[DTMbimmer07]

I used to run 235-40-15 nitto nt555's up frotn and 245-40-17 nexen n3000 or n5000 i cant remember which one. but i loved it, never had understeer, and driving in the rain was pretty good. rubbed a little bit in the front because im 5lug and i didnt have the right control arms on but wasnt that but i kno if i would do it again it wouldnt rub.

[bubbajan21]

Sorry, I came off a little condescending. I have had rubbing issues with 225/45/16 on the fronts and it took a lot of hassle to correct so I don't like recommending wide fronts. I'm also not a fan of staggered setups so that really limits my opinion on rears if the fronts are 225 of narrower. I know you have better front tire clearance than M3s though without the side skirt to contend with so you are probably fine with 225 on ET20 there. R1R does run quite wide. Not as wide as 888s, but nearly.

http://marktg.toyotires.com/file/30251.pdf

Not a problem, I know on R3V you get used to dealing with guys who have an idea in their mind, post it, get told it's dumb, and fight it instead of listening to people who have more experience and knowledge than them, so I get where you're coming from.

I do know without a doubt that I can fit 235/40 17's on the front with zero rubbing (except on the inner frame rail at full lock, but the new car has a TMS steering rack limiter stop kit so it can't hit the frame rail) so that is not an issue. I do know the frustration of buying a set of wheels and tires only to put them on and see they rub.

I know 215 front 245 rear setup is far from ideal, but will my car handle like a pig in those sizes with the Super Sports? I know I've said it about 100 times, but I'll say it again, I don't want this to end up like a drag car.