Fchat members, I am currently running a set of Potenza's in 285/35/19 225/35/19 Which are OEM size. The front diameter is 25.2" vs. 26.9" in the rear. Sidewall is front 3.1" vs. 3.93" in the rear. I picked up a set of tires used off a friend (Michilen Pilot Spot Cup 2's) which were off size and now am thinking they are way too far off. They work in regards to ABS/Traction (4-5% different from OEM), but I am worried that the car will be "loose" feeling since the rear of what I got is much smaller. New Setup: 285/30/19 235/35/19 The front diameter is 25.5" vs. 25.7" in the rear (no rake) Sidewall is front 3.24" vs. 3.37" in the rear. From how I see it, the car should look better since the tire sizes are more equal in diameter, but again am worried about handling. Does anyone have any advice? I see some guys running 295/30/19's and 235/35/19 which they seem to like and are very similar. Please assist if you can.
Referencing this thread: F430 Rear Tire Suggestions - FerrariChat.com A lot of people are doing 295/30/19 rear. Thats really similar to a 285/30/19 rear from doing tire calculations. Everything is within .3" difference.
If you're going to do anything, keep the rears the stock size and go wider in the front. The F430 understeers worse than most performance cars out there, and really benefits from increased front-end grip. I track my F430 often, and you have to really finesse the car into turns to prevent it from plowing. Of course, the 99% of owners who take it to Starbucks and back each Sunday can probably keep the OEM sizes all around
Well, I would love to, but these are 30's vs. 35's. Just wondering how far off I will be. Again, from a looks perspective, I always thought the 35's out back just were too tall for a street car. For the track or for spirited driving, the 285 patch works for me (but 295 would be preferred). My issue is the height in the rear is too small compared to the 35 (vs. the 30)?
You've gone up in front diameter and down in rear diameter. It's not about getting "loose", it's about your ABS and traction control freaking out. As said above going slightly wider up front (or all round) is fine. Otherwise stick with OEM sizing.
You are correct. However, there are people running 295/30/19 rear and 235/35/19 front constantly. The difference in diameter between 295's and 285's is quite minimal. Any thoughts on that?
ABS starts going able sugar somewhere in the 4-5% difference from OEM front to rear tire diameter differential. OEM 26.85"-25.20"=1.6" or 6.35% F-R differential. 285/30 19=25.73", 235/35 19=25.48", 25.73"-25.48"=0.25" or 0.98% F-R differential. Difference between OEM and new set-up is 6.35%-0.98% or 5.37%. Not good. Sounds like a very good chance the ABS is not going to work as advertised because it only cares about differences in ABS sensor rotation speed and that is determined by tire diameter.
Terry, Thanks for the input. The .37% could be enough to throw this off if the system is calibrated 4-5% of threshold. ABS aside, what do you feel about handling? I find the stock 285/35 rears to be pretty sizable for height while the fronts look like skinnies. I do like the cars balance but feel that it understeers really bad. The extra 10mm up front and some extra sidewall should help plant more rubber on the ground. However, the rear is what worries me about it being smaller in diameter and possibly feeling a bit loose at higher speeds? Any experience with this?
I've always thought the front tire was a little narrow on the 430... 225/35, really! Will consider changing to 235 next time. also not sure if you guys knew this but I always use this website to calculate tire sizes. Helpful when you are trying non oem sizes/aftermarket wheels Tire size calculator
That 0.37% is imprecise because ABS can act up anywhere in that 4-5% range or greater. If you want to cut down on understeer, try a Scuderia/CS rear anti-roll bar and do it the correct way. Part number 198416 and you would need the matching bushings, too. Not an F430 expert, so I do not know the difference in diameter between the F430 bar and thicker CS/Scud bar. You can fiddle with tire sizes to a certain degree, as long as you maintain a similar geometry and the fronts do not rub, but a larger rear anti-roll bar is a sure way to help. That is what Ferrari does on handling packs for quite a few cars. My 575M has a 21 mm bar that is 133% stiffer than the standard 17 mm bar. Here is how to quickly calculate tire diameters or look them up on TireRack. On a hand calculator, takes me about 10 secs to calculate a tire diameter. Not as accurate as the manufacturers' numbers on TireRack, but will tell you what not to use. 235/35 19 (235 x .35 x 2)/25.4 + 19. Pretty simple. The aspect ratio is doubled because you have tire depth top and bottom.
I fully agree with you in regards to the % being off and the proper way to get the car to handle. Back to the tire sizes. the 285/30/19 is .2" in diameter smaller than a 295/30/19. There are a lot of people here running 295/30/19 rear and 235/35/19 fronts. Based on the calculation, we should be within tolerance on both setups granted they don't have an issue. What do you think in regards to that?
You sure they are not running 295/35 19s instead of 295/30 19s? Over an inch difference in those two, 25.97" for the 30s vs 27.13" for the 35s. The 35s should work a lot better for the ABS. Same width, just taller.
Affirmative, with 35 series tires, up or down a size from OEM does not make much of a difference. When you start going to 30 series tires from 35s, there is a big difference in tire diameter. On the 575s, the 255/35 19s in front are pretty much the same diameter as the 305/30 19s in the rear, ~26". To find a 30 series tire to match the 27.13" of the 285/35 19s, you would need a 345/30 19 (27.15") designed for 12" or so wide wheels.
295/30/19's is what they were after. Here is a post of a gent running them 2016-03-11_1525 - elichstein's library from url: F430 Rear Tire Suggestions - FerrariChat.com thats why I don't foresee an issue, however, I fully agree with you on going down an inch.
Try them and see. That little extra height 0f 0.24" may make the difference between happy ABS and unhappy ABS.
Did you ever try this? I'm curious as I think the problem won't be with ABS but the traction control. ABS only sensing if each tires locked up, not really care if there is difference with other wheels. Traction control on the other hand monitor that rear tires don't spin faster than the front. This the necessity of having correct ratio. I know first hand that even with CST off the traction control will still kick in albeit they give a lot of allowance
It seems we all agree 235/35/19 front is good. However, what is the consensus on 295/35/19 vs 295/30/19 rear? Mathematically, 295/35/19 has less % change from stock versus 295/30/19. This should be better for traction control system and ABS, right?
