TCS wheel sizes: +- 5% math and example

[nsxinmn]

Please bear with me Prime members; I have reviewed the tire and wheel wikis and threads as best I can.

I have blitz Technospeed wheels 17x8 and 18x10 on my recently purchased 1994 nsx. The currently installed 245 front tires are rubbing as expected.

From the wiki and various threads, the standard rear/front wheel ratio for TCS (94-01) is ~1.0466, calculated using the OEM Yokohama tire sizes (24.7/23.6). If I understand correctly, aftermarket rear/front tire ratios should be +-5% of the 1.0466 value.

My tolerance calculations are the following:
Minimum ratio: 1.0466x.95 = .99427
Maximum ratio: 1.0466*1.05 = 1.0989

One tire I am considering is Bridgestone Pole Positions for all four wheels in the following sizes:
Front: 215/45R17 (24.7")
Rear: 265/40R18 (26.3")

The rear/front ratio of this combination is 1.0647 (25.3/24.7) and falls within the minimum and maximum values above.

Is my understanding correct, and both the Pole Position tire example and any rear/front tire combination fitting within the min/max ratios above will work properly with TCS?

Thanks!

Shawn

 

[jwmelvin]

Your ratios do seem okay. The problem will be rubbing in the front. Stock fenders? Suspension?

 

[stuntman]

91-93 = 1.079
94-01 = 1.046
02-05 = 1.054

The factory ranges are 1.046 - 1.079

You will probably run in to more problems with a 215/45-17 than the often used 235/40-17 and 265/35-18 or 275/35-18 rears. Why not just go with those sizes that will fit easier?

 

[nsxinmn]

Thx for the responses and questions.

The fenders and suspension are stock. My thought with the proposed sizes is to preserve the intended diameter ratio back to front as well as the smoother ride of the taller sidewall (lots of potholes in Minnesota). I will not be racing the vehicle.

The current tires are nearly the same diameter which may be causing intermittent TCS/ABS that I've noticed since I picked up the car.

Have improvements in tire technology since the car was manufactured reduce the need for a taller sidewall? Are there any problems with having back tires 1-1.5" larger?

I really like that look, but I don't want to mess up the handling or repeat the current problem with tires rubbing in the fender well.

 

[stuntman]

What are the current sizes? I'd still go with the tried and true 235/40-17 & 275/35-18 which has plenty of sidewall height.

 

[M-P]

EDIT: Ignore my last post...too early in the morning.

 

[jwmelvin]

What are the current sizes? I'd still go with the tried and true 235/40-17 & 275/35-18 which has plenty of sidewall height.

If the goal is eliminating rubbing on the fender liner, reports are few and far between of that result with a 235/40-17 front tire. Rather, the safe bet is 215/40-17. What is your front wheel offset?

 

[stuntman]

I had a 215/45-17 on a 17x8 on the front of my MR2 Turbo and put the tire on the NSX, and it was just too big and hit way worse than the 235/40-17 on the 17x8 +38, which is a commonly used front size for the NSX.

You can look at some of the pictures in my MotoIQ Project NSX articles to see what it looks like. The amount of rubbing also depends on your camber, ride height, and spring rates, but a 17x8 +40 would help tuck the tire in even more to reduce rubbing the factory liners at full lock. 215/40-17 is a no-brainer to have no rubbing at full lock.

http://www.motoiq.com/MagazineArtic...Nitto-Tires-in-Pursuit-of-a-Track-Record.aspx

http://www.motoiq.com/MagazineArtic...est-A-Ported-Intake-Manifold-and-Headers.aspx

 

[Hapa88]

If the goal is eliminating rubbing on the fender liner, reports are few and far between of that result with a 235/40-17 front tire. Rather, the safe bet is 215/40-17. What is your front wheel offset?

+1 the safe bet is definitely 215/40/17 and 255/35/18 or 265/35/18. If you have the correct offset wheels, you shouldn't have any rubbing issues at all.

Don't forget that the 45 series tires are TALLER (or larger in diameter) than a 40 series. That causes the tire to "fill" the wheel well more giving you even less room for it to turn and move.

My recommendation is error on the side of safe and use the tried and true 40 series for the fronts.
I would only recommend the 235/40/17 and 275/35/18 if you track your car and have the right width and offset wheels. The 235/40/17 is not only wider than a 215/40/17, but it also is taller, so you definitely have a greater potential to rub.

 

[scammy]

On my track set of rims (Advan RG3 RGIII, 17x8+38 18x10+35) with Nitto NT01 235/40/17 front-275/35/18 rear, I have zero rubbing unless at full lock and on the Downforce brake/air deflectors, I do have the comptech camber kit at about -2.5deg but will check exactly from my last alignment.
I would like to see if I could fit 245's up front in the Nitto's on this setup but they don't make one
with my street set up I have the 215 and 265 Dunlop Z11's setup with zero issues entirely

 

[nsxinmn]

My car is getting the TB/WP service plus new hoses, but I have the info now:
front: 17x8 +41 with 245/35/17 tires (rubbing)
Rear: 18x10 +47 with 285/30/18 tires

I could go with Yokahama S.drives for the front 215/40/17. However, I noticed the 215/45/17 tire choices are much greater (90 vs. 9 for the 40 size). There are definitely good tires at the 40 size among those 9, but no Pilots, Potenza's etc.

BTW should all 4 tires be the same model? Or should certain models not be mixed with others?

Thanks for all the help.

Shawn

 

[jwmelvin]

If you're looking at S.drives then you're not concerned about performance? That suggests that you should definitely stay with 215/40-17 for the front. Once you are using the best tire you can in that size, and are still looking for more, then you can consider other sizes. The first of which would be a 235/40-17; that size rubs at full lock unless you modify/remove fender liners. From there you get into even more difficult territory making things fit.

How do you use the car? You say you are not racing. Are you tracking it? Do you drive at the limit of the tires?

 

[Tokuisport]

i currently run 215/40r17 and 265/35r18 dunlops with very very little to no rubbing. im lowered on bc coil overs with 8k and 10k springs instead of the standard 10k/12k off the shelf.

 

[Hapa88]

This hasn't been stated yet, but also remember that going above a 255/35/18 rear tire also changes your final drive gearing. Larger diameter wheels will affect your acceleration.

 

[MartinSD]

Is there a way to reset the TCS error light when it comes on?
Martin

 

[nsxtasy]

I could go with Yokahama S.drives for the front 215/40/17. However, I noticed the 215/45/17 tire choices are much greater (90 vs. 9 for the 40 size). There are definitely good tires at the 40 size among those 9, but no Pilots, Potenza's etc.

There are some excellent "extreme performance summer tires" available in the most common 17"/18" sizes of 215/40-17 front and 255/35-18 or 265/35-18 rear; these are among the stickiest street tires you can buy:

Dunlop Direzza ZII Star Spec 215/40-17 and 255/35-18 or 265/35-18
Yokohama Advan Neova AD08 215/40-17 and 255/35-18 or 265/35-18
Falken Azenis RT-615K 215/40-17 and 265/35-18

I would not recommend the Yokohama S.drive, which is a much lower performance tire and thus not really suitable for an NSX.

BTW should all 4 tires be the same model? Or should certain models not be mixed with others?

It is best for all four tires to be the same model, so that the tires all handle predictably. If that is not possible, then it's best to find models of tires whose performance is as similar as possible.

Is there a way to reset the TCS error light when it comes on?

No. And the most common reason for the TCS activation light to go on is using the wrong tire sizes, i.e. ones that don't preserve a ratio of front-to-rear outer diameters close to that of the factory sizes.

If you stick with these most commonly used tire sizes, you should not experience any TCS problems on any year NSX:

15"/16": 205/50-15 and 225/50-16
16"/17": 205/45/16 or 215/45-16, and 245/40-17 or 255/40-17
17"/17": 215/40-17 and 255/40-17
17"/18": 215/40-17, and 255/35-18 or 265/35-18
18"/19": 215/35-18, and 265/30-19 or 275/30-19