alberto_mg

Hi. A fellow board member PM'ed me about wheel/tire size for the FD and I found that we were both in a similar boat. I've searched around and read a bunch of threads about wheel/tire size for the FD, but most centered upon fitment and not driving characteristics.

So I ask, what is a good wheel/tire size combo for mostly street driving with an occasional HPDE event or autox? Something that makes the car feeling neutral and well balanced?

Assume the suspension is in good working order with a Koni street spring and stock sway bar setup.

My thoughts are as follows. Please someone confirm my suspicions/thoughts...

Wheel Diameter: I like 17s over 18s b/c 17s can often be lighter than 18s. I like a lighter wheel tire combo as it generally makes the car feel more nimble and responsive. less unsprung weight.

Tire Sidewalls: Again I like 17s b/c the the tires will have slighlty larger sidewalls to help soak up road irregularities and will likely help wet driving all things being equal.

Wheel Width: Wider ain't always better so I'm thinking some 8.5" for the front and some 9" or 9.5" for the rear. Or maybe some 8.5" or 9" all around. More on that next...

Tire Diameter: I also would like to keep the same tire diameter. I'm not a big fan of staggered tires b/c it sometimes makes the car feel like it understeers more. Plus I also like to rotate them b/c I'm not made of $$.

However, I think if you have slightly larger rear tires, it might improve the overall balance of the FD especially with stock sway bars. From what I've read, it seems like the 93 can be a little tail happy. I'm still sorting mine out so I haven't had the opportunity to get on it real hard.

I'm think that maybe running a 235 or 245 front with a 255 rear will make it a bit more neutral in its reactions. Tire Rack's site I think recommends 265s for the rear, but it seems so much larger than the front that I just have to question the balance side of things. I've also read about some guys running 255s all around. That seems a bit wide but it might be a nice setup. Or maybe 245s all around on 17s. Not sure how the overall diameters work out on 245s compared to 255s though. Maybe someone can comment.

Any comments would be appreciated. Thank you!
-Alberto

SleepR1

9 x 17, 40 mm to 45 mm offsets, 255/40-17. Proven fitment by me, and many others who drive their FDs daily, plus autocross, spirited country road-driving, and open track driving at high speed road courses.

Some wheel choices and their weights (9 x 17)
SSR Integral A2, 19 lbs
SSR GT-1, 19 lbs
5Zigen FN01, 18 lbs
Racing Sparco NT-R, 17 lbs

Some tire choices and their weights (255/40-17)
P-Zero Asimmetrico, 23 lbs
BFG G-Force KD, 27 lbs
Yokohama AVS I, 26 lbs
Bridgestone S-03, 27 lbs
Toyo Proxes T1-S, 25 lbs
Continental Sport Contact 2, 25 lbs

Good luck!

DamonB

Your points about 17" wheels are all valid. Your suspension is stock other than springs? Have you actually driven the FD during an HPDE or autocross? If so, how many times and what did you think of the handling?

If the car is nearly stock and you only rarely compete I would keep the same tire size front and rear so I could rotate the tires and greatly increase my treadlife. Balance front and rear can be easily altered with tire pressures or you could upgrade later to an affordable adjustable damper like the Koni yellows to allow you to further tune the car for events.

FWIW everyone speaks of the FD being tailhappy and I don't find it that bad (even before I starting modding the suspension); any powerful car can be tailhappy if the driver has a brick as a right foot. You haven't even driven the car hard much so run it like it is before you do something different with it, otherwise you can't say if the car is to your liking or not. The conventional wisdom about "handling" around here is in many cases flat wrong. Handling IMO only counts when at speed on a closed course, anything else is playing pretend because you have no idea what handling of any car is unless you're driving it hard.

alberto_mg

Thank you both. I'm very surprised that 255s actually fit up front w/o a coil over setup. Couple more questions...

Do you know if 245s can be used or does that throw off the overall diameter? I don't want to be "over-tired" either...

Any preference as to 40 or 45 offset? Is there more of a risk of rubbing with one vs. the other?

Yes, I basically have a set of Koni's with PFS springs, stress bars and stock anti-sway bars. I will be installing RE toe links and raising ride height in a week or so and re-aligning everything to the specs in the archives. No more suspension work is planned since it is primarily a street car. I race karts for some real fun.

I agree with all your points and will not be changing anything till I feel the car out on track. I'm in the education and planning phase trying to learn about what rim/tire size setup people run and why.

There are all these threads about how big and what offsets, but I haven't seen any that focus on that setup's effect on handling and feel hence this long winded thread.

I will need tires soon and will be keeping my eyes open in case I see something interesting used. I always thought the FD needed some bigger rims to fill it out.

I plan on hitting Lime Rock in April and maybe head up to Watkins Glen. I haven't had the opportunity to enjoy either track since I sold my last GTU. I hated my BMW at Lime Rock. It felt overweight and numb.

Thanks for the info and if you could answer the questions above, I'd greatly appreciate it.

adam c

iTrader: (2)

I agree with Damon. You should drive the car in a few events before making a bunch of changes. A car that oversteers a little may be great for autocrossing, but not so great for an open track.

Another thing to consider is weight. The stock FD wheels are pretty light. Heavier wheels and bigger tires may make the car feel less "nimble"

Being able to rotate the tires is a big plus. If you drive your car in a "spirited" manner, you will almost certainly wear out the rear tires 50% faster than the front tires.

You are smart to consider harshness of ride. A little more sidewall can provide a great difference in ride comfort. Most of the younger FD owners have forgotten how stiff the car comes from the factory, especially the 93's.

If your car oversteers too much (tailhappy), an alternative solution would be to change or remove your rear sway bar. A lighter, or softer bar will get rid of some oversteer. I completely removed the rear bar on my FB. It helped alot.

maxcooper

A stiffer front bar can also dial out the oversteer.

I like SleepR1s recommendation. 255s on 9" wheels all around would be nice for rotations and should maintain the stock balance.

-Max

tt2323

So you can get a 40lb rim tire combo running 255/40/17 all around going for the lightest...what is the weight of a common stock rim/tire combo?

maxcooper

Stock wheels plus tires is something like 37-44 lbs depending on the tires. Most are probably in the 39-42 lbs range.

-Max

DamonB

And that is the way to go A stiffer front bar makes the rear grip better on corner exit by keeping more weight on the rear inside tire without adding spring rate to the rear. On roadcourses (with race rubber, adjustable shocks, alignment, yadda, yadda, yadda) I have run some really high amounts of front bar and the car just loves it. On autox courses I can't run near as much front bar because the lower speeds and much tighter turns insist the front end be freed up so I can make it turn in.

ArcWelder

Alignment settings can also have a large impact on the balance of the car. Reference the Pettit Street/Long Track/Short Track/Autocross alignment numbers as a starting point.

My car behaves towards mild understeer at low speeds, neutral to maybe slight oversteer at high speed using the Pettit Long Track numbers. All controllable with throttle.

Mark

alberto_mg

Thank you very much! Great info.

One last question regarding overall wheel diameter. Running 255/40/17s on 17x9 rimes - Is it any different than overall diameter with stock wheels?

I believe stock is 24.5" overall diameter. Will running the 255 setup affect gearing at all?

saxyman990

Overall diameter kind of depends on tires. But running a 255/40/17 is extremely close to stock diameter. There's less than a 1% difference.

I also run Manny's (SleepR1) fitment of 255/40/17 for both my street and track setup. I absolutely love it and would recommend this setup to anyone! The tire/wheel combo I use is slightly lighter than my stock setup by about 0.5lb. But going off of Manny's posted tire weights, maybe I'll switch to P-Zero's to shave a couple of lbs... hmmm....

SleepR1

Stock 225/50-16 is 24.9 inches. 255/40-17 is 25 inches. Pretty much equal. No net effect on gearing.

SleepR1

Another satisfied SleepR1 fitment customer Love the Fikse FM-10s. Wish I had the cash to buy them when Fritz Flynn had them up for sale. Yeah, the P-Zero Asimmetrico in 255/40-17 (22.6 lbs) is nearly the same weight as 225/50-16 (23 lbs) Asimmetrico. Must be a sidewall thing?

saxyman990

Yep, definately satisfied. Thanks for the compliment on the wheels Manny! I love em too, so no you can't have them! I know how you feel about the cash though... I'm still eating tuna fish and crackers for three meals a day to help offset the cost of those suckers... ouch.

Definately interesting info regarding the weights of the Asimmetrico's. Very weird. My Toyo's are looking pretty bare... Maybe I'll try the Asimmetrico's for my next tire.

Rob

DamonB

So nobody is allowed to have 9x17 wheels without giving kudos to SleepR1?

saxyman990

Damn straight! Maybe he should start charging royalties... could pay for his own set of Fikse's that way

SleepR1

Hmmm...not a bad idea LOL

Well not 9 x 17 all around with 255/40-17 LOL Just glad to be of some service to the FD Rx7 community. Peace!

DamonB

We should have little labels that fit outside the barrel: This fitment by SleepR1. Then whenever you get tires mounted the tire guys would go "Ohhhhhh. The Sleep guy made these!"

SleepR1

Let's not forget Max Cooper's fitment of 10 x 18, 50-mm offset, 285/30-18s all around You'll need 2.5-inch coil springs, but it's the ultimate in contact patch (oops, I mentioned the dirty word, "contact patch" LOL )

DamonB

I always shave my patch before mounting new rubber.

CrispyRX7

iTrader: (139)

Bah! I've been running 17x9 SSR Integrals with 255/40-17's on all 4 corners (45mm offset) since early 1999 both street and track. Hi Manny
Regards,
Crispy

alberto_mg

Haha. I guess it becomes a matter of post quantity here between Crispy and Sleep

CrispyRX7

iTrader: (139)

Quality over quantity.

(ducking)

Crispy

ArcWelder

Let's not resurrect the contact patch discussion again.

Mark