what wheel sizes and tires do all you road racers run?
 

I have 235/45/17 in the front and 255/40/17 in the rear. Thinking of going to 18's with 245/40/18 and 275/35/18 in the back. Does anyone know how this will affect the handling characteristics of my car, or am I better off sticking with the 17's?

Good luck finding 18" race tires. There are some hoosiers for $$$$$, but no RA1, V7oo, V70a, Yoks, Etc. I currently run 235-40-17 RA1s on a 17x8 rim. I am going to make some flares for my FC, and run 275-40-17s on a 17x9.5" rim all around. I'll probably use Supra tt rear TT rims as I already have 3 from my Supra. You'll have to experiment with your shocks, and sway bars to keep the car from pushing, assuming your pretty neutral now. I run 255-40-17s front, and 275-40-17s rear on my supra. If your making a lot of power, you'll love the bigger rears as you may be able to exit under full power instead of waiting to get straight. Carl

SRX7 ('81-'85) runs 13" wheels (most ppl use either panasports, diamonds, american racing wheels) on 205-60-13 Kumho Victoracer V700 or Toyo Proxes RA-1.

--eric

Kumho makes 18s in the Estca V700s. 265/35 and 285/30

Now, I would stick with 17s because of weight, I don't know of anyone making a decent race wheel in 18s that isn't the price of your first AND second born children.. A good CCW wheel is ~25lbs IIRC in 17x10

I run 15x6.5" stock wheels with 205/50/15s, moving to a max legal 15x7 Kosei K1 with 225/50/15 Toyo RA1 very soon.

PaulC

245/45-16 Hoosier A3S03s on stock fd wheels. I can't beat on them to much because I have to save them for auto-X.

Re: what wheel sizes and tires do all you road racers run?
 

First of all, if you move up to 18s, you will need lower profile tires than that (unless using true shaved race tires). With street tires, you can run 245/35 or 255/35 up front and 265/35 or 285/30 in the rear.

Max Cooper runs 18x10 CCW wheels (which only weigh 21 lbs) with 285/30s on all 4 corners. SleepR1 ran 245/40 17 and 275/40 17 Hoosiers but is going to a different set-up for next year. I believe he is going with 265/35 18 up front and 285/30 18 for the rear.

Note that to go 18x10 up front (like Max), you will need aftermarket coil-overs with 2.5" springs. I think I've seen you post that you have the tein HA's, so you would be set there.

I was thinking about 225's on 16 x 7.5 wheels for an n/a. Would that be a good size?

That's fine if your race class allows 16x7.5 wheels.

Victor
 

This year the setup was 8.5 x 17 with 245/45-17 front and 9.5 x 17 with 275/40-17 rear. Wheels were SSR Comps. Tires were Hoosier R3S03

2003--if I have transport service to the track--9.5 x17 with 245/40-17 front and 10.5 x 18 with 285/30-18 rear. Wheels will be Volk CE28N. Tires will be Hoosier R3S03. If I have no track transport for 2003, and I'm forced to drive to and from the track--FIVE 9.5 x 17 CE28Ns with 255/40-17 Michelin Pilot Sport Cup Comps. The fifth wheel/tire serves as a full-size spare; I'll invariably pick up a screw or nail during my commute TO the track!

FWIW Your setup will create understeer. If you stagger the wheel diameters to allow for taller tire profiles up front (while maintaining the correct overall tire diameters fr/rr), you will dial in more oversteer for a more neutral handling setup. Understeer is a good thing, but not too much of it, such that you have a hard time turning in...

I run 18x19 Technomagnesio wheels with 265.650x18 Dunlop slicks all around.The Technos are very light at 17.5 lbs. each and Dunlop GT slicks come in 6 compounds and I run 'medium minus'. Grip is very good. <G>

Wow, Brad...you must mean 9 x 18 Technomagnesios, based on your Dunlop slicks' sizes. Converted to inches your tires are 10.4 inches wide x 25.5 inches tall x 18-inch wheel diameter? Nonetheless I'd like to see a pic :) Curious why you didn't go with Pirelli D5 compound or Michelin slicks (the Porsche Supercups have switched to the Michelins from Pirellis)?

Doh, I hit 19 instead of 10. They are 18x10. The tire is exactly the same size as the old 275/40x17 I used to run. The Dunlops are awesome tires with a very sharp shoulder profile.

Ahhh, makes sense now :)

Glad you like the Dunlops...

where I race in EP biggest we can run is 15x7 with 10 wide slicks. BTW when I used to race a VW I started on 13x6 rims with 205/60x13 tires. I was given a chance to do some tire testing for Toyo and found that the car was faster on 185/60x13 tires. Just goes to show that bigger is not always better.

Brad, do you have a good source for the dunlops? i have 18x10s also and would like to try the pure slick as as opposed to the V700s ive been using.
1R1

TIRES?
 

UNLESS u have super big BRAKE or big pocket. the 17 are good enough for every thing. I will run 17x9 F/R with either 245 or 255. on MY ITE and FP race car

i recently debated this decision and decided to go with the "cooper" fitment....that is 18X10 all around with 285/30 khumo v700. basically the pro/con list comes down to weight vs contact patch.

ccw, kinesis, fikse, forgeline, and probably others make 18X10 that weigh about 22lbs. v700's in 285/30-18 weigh about the same....so that's about 44lbs per corner. all in all a pretty reasonable number given the size of the contact patch you get. any fd making 350 or more rwhp will be fine accelerating that rotating mass.....of course another downside to the weight is the handling effect of the unsprung weight. i decided the extra contact patch off set this issue.

additionally the issue of lower aspect ratio effectively changing the spring rate may or may not be an issue for some.

all in all, i elected to maximize my contact patch. i'll let you know how it turns out if kinesis ever delivers the wheels....waiting for more than two months now and getting pissed!

fabian

fabian,

I need a loan :) Those are some expensive wheels you just rattled off..

Seriously though, why not 17x10? 285s will fit on 17s just as easily as on 18s..

Anyway, enjoy either way :)

PauLC

wow, how much are those wheels?! :eek: I know the gold magnessium mazdaspeed wheels are extremely expensive...

1RedR1and1RedPEP... As for a good source, not really. I scour the tire dealers, like Sasco, for quallie take offs. You need to wait until right after a big GT race like Daytona to snare a quantity. Then, I bag them and use them up.

Chronos... The 18x10 (I made a typo when I said 18x19) Technos are in the same bracket as my old Kinesis which were stolen along with my old car and never seen again. Istill have my eyes open and the wheels serial number, hehe. Sooner or later they will appear. <wicked grin>

Paul,

New CCWs are 19 lbs in 17x10 and 20 lbs in 18x10. I have the "intermediate" lighweight design (non-cheese-holed centers) which is 20.5 lbs in 18x10. Another reason the 18x10 is nice is that one can use 285-30-18s which, for some tires, are actually lighter (not Hoosier which is .5 lb more)than the 275-40-17s due to shorter sidewall (of couse there are issues with running such a short sidewall). You can maintain the stock diameter/circumference for similar gearing with this setup as well.

Gene

For you guys concerned about unsprung weight, there is one other point worth mentioning re: tire weights. Kumhos, though less expensive, are much heavier than Hoosiers- even the new Ecsta V700. For example, in 275-40-17 the V700 Victoracer weighs a whopping 28.8 lbs, the Ecsta weighs 27.2 lbs, and the Hoosier R3S03 weighs 20.5 lbs. That's roughly a freakin' 7 lb difference with the lighter Kumho!

BTW- the Kumho Ecsta in 285-30-18 weighs 25.6 lbs.

Full blown slicks like Brad's Dunlops are even lighter than the Hoosiers.

Gene

Gene is correct regarding tire/wheel weight differences.

While I did not weigh the combos on a scale, while swapping the CCW 17"/Hoosier for the Tecnho 18"/Dunlop the weight differnence was noticable favoring the latter.

Also, John Purner at CCW has been offering 18" CCWs with Goodyear slicks for years. You hard core brethren may want to check with him regarding affordable tire/wheel combo deals.

Actually, the CCW's are less than $2k for the set. No one makes a 285 tire in 17" diameter. 275/40 really only works for a race tire, 275/40 17" street tires are too tall

If any manufacturers made a 285/35 17 tire, there would be no reason to go to 18s IMO.

Uh, I believe this section is 'Race Car Tech'. We are discussing track only tire/wheel combos, not street 'bling-bling'.

Back on topic, I'm not sure you can fit any tire wider than 275/40x17 (or a 265/650x18 which is dimensionally the same) without flaring the fenders. Even then, you will need to run an off-center wheel and suffer the suspension problems that will occur.

It will probably generate enough grip to match the driver ability anyway. We all need to work on the driver as he/she is the biggest performance weak spot.

Can you elaborate a bit on this for me please? :) I'm somewhat of a newbie when it comes to race mechanics...

If the centerline of the wheel is far away fropm the centerline of the wheel bearing, then the resulting moment will add undue forces onto the bearing. This can result in early failure. Also, the extra increase in scrub radius (in front) can unduly effect your handling when turning. In other words, don't run 18" wide wheels. <g>

Gee Brad, I was planning to run 285/30-18 Hoosiers mounted on 10.5 x 18 CE28Ns (45-mm offset) in back?

Yes, I believe this is why you should run as close to stock offsets as possible when upgrading wheels.

John Purner's CCW setup for 10 x 18, with 285/30-18 Hoosiers--offset is 2 inches (50.8 mm). Stock offset is 50 mm (1.96 inches).

Change the offset to more negative (smaller number) then the scrub radius, wheel bearing load, AND wheel rate (the overall "spring rate" of the suspension) all change.

SleepR1... I agree. Talk to the wheel manufacturer about your setup. If they don't know, they should. As you know, .8mm is very little and you will be fine. The wheel/tire will fit your wheel wells and you can worry about other things.

i agree that if a 285 was made in 17in diameter with the proper overall diameter, this issue would be moot and we'd all have 17X 10 all around. however, no luck so 285/30-18 is the "largest contact patch" tire we can use without body mods and we're stuck with the compromise.

the 18X10 fitment uses a 50 mm offset which is not significantly different from the stock offset to worry about.

i may be off on the khumo tire weight. my khumos are still sitting at rishies shop.....still waiting on my wheelset from kinesis :(
rishie told me he weighed one on his shop scale at a little over 22lbs can't verify that as i wasn't there....though i agree it may be a bit optimistic.

and finally, i agree that in the end, the driver is STILL by far the most important variable. despite that, i won't mind running those 285's too much while i'm "improving" :)

regards
fabian

i'll post some pix if i ever get the damn things on the car!!!

foko,

please do post pics. I miss my old Kinesis K20s that were stolen along with my car a few years back. Alan Bayliss makes fine products.

also, 275/285 is PLENTY of tire for our cars in road race configuration. If you use slicks (not DOT) the grip is plenty.

best,
Brad

yeah, i know he makes a great product but i have to admit that so far the service has been less than spectacular. rishie has been hounding the guy for months and finally the wheels are almost here. the latest word is that the wheels are just shipping....should be here next week sometime. will be installed soon thereafter and i'll post some pics.

i'll be running this setup at sears point at an open track event on 1/25.....full report to follow.

kinesis k28 18X10 all around with khumo v700 285/30.
just talked to rishie today, he gave me revised weight on the khumo's of just over 25lbs each. when the tires are mounted we'll weigh the whole setup and post it.

my present setup is oz comp wheels (very, very heavy) in 17X8.5 f and 17X10 r (235/255 toyo ra1). this setup understeers predictably even with relatively soft front spring rate (10kg/mm) and dampers full soft (j.i.c flta2).

i suspect the new setup will be better:)

regards
fabian

Fabian,

Your turn-in issues will evaporate with the 285 all around. When I converted to all 275/40 Hoosiers the car came alive again. Next time you need tires, try everything you can to go to Hoosiers. The weight savings alone over Kuhmos is amazing not to mention the grip.

Hoosier R3S03s are the sh*t :)

Say Brad, you think I can squeeze 10 x 17s CCW P4 mesh all around with 275/40-17 Hoosier R3S03s? I have stock style H&R springs, OE R1 Showa shocks, and Eibach sway bars fr/rr.

Don't know what it is about the 245/45-17 fr and 275/40-17 rr, but that setup was VERY forgiving. Must be the tallish sidewalls for both tire sizes (25.3 inch tall) ?

Anyhow, I'd like to dial out some of the understeer, and increase the car's overall cornering stick with same size 275/40-17s all around.

I read somewhere that John Purner uses two different offsets for the 10 x 17 setup. Something about the clearance from the rear trailing arms in back?

I'd like to be able to rotate the tires, so I was thinking of using 1/4-inch wheel spacers with longer wheel studs for the rear hubs; or do you think the stock studs will be fine with 1/4-inch spacers?

This isn't the forum for it, but this discussion caught my attention. I have a set of Kinesis K10 wheels for my FD, 17x9.5" that I run 275/40's on all around. Anyone want to buy them? $1700 (compare to about $3k new)

I just bought a new race car and won't be tracking the FD much anymore.

Manny, you can't run that wide a wheel with stock diameter springs. With 10s you will need tubular rear control arms and 2.5" diameter springs. Nothing else will do. Even then, you will eat the front liners. Most of us hard core trackers don't care, mine are cut away in both front inside corners anyway. Also, you will need some ride height, as well. Look at the picture on my web page. I am turning right at about 90 mph in that picture so the car is up a little on that side, but yu can see I am not slammed. That is the solution, not spacers and stuff.

Got pics? How posting a bit more info?

Yeah, but that stuff costs money :(

Old saying:
Speed costs money, how fast do you want to go?

yeah, i expect the understeer to disappear.

i will definitely consider the switch to hoosiers after i cook this set of khumos. unfortunately, i may need to use the same wheelset for dry and wet....(yeah it rains up here in north. calif.:) ) and since i actually like running in the rain, i may need to stick with the treaded tire until i get a second wheelset for rain tires.

the wheels arrived today and are being mounted tomorrow. should be on the car this weekend....yippie!

fabian

brad, where did you get the idea to use 1000 & 700 lb springs? I run 650 & 450lb. Whats the difference in feel.
Did you do it because of a switch from performance dot to slicks?

racedriver,
I was running 800/600 on my old car (the one that was stolen) after moving up from 650/400. The idea was to eliminate roll from the car. My track driving friend Jim O'Brien had taken the increases to the next level and went to 1000/700 on his car. We were at Watkins Glen for an open track event in 1999 amd I drove Jim's car. I was impressed and was planing on the increase for my car when it was stolen. As things worked out, Jim ended up selling me his car. I've since changed almost everything on the car BUT the spring rates. It helps that I run a lot of downforce and a very stiff front bar (Tri-Point .25" wall set to full stiff). After switching to slicks I was afraid the car might need some changes, but I only needed to take a little camber out to get my tire temps perfect. Like anything on a race car, it works for my tracks and my driving style. On my home track, Texas World Speedway, I am in long fast sweepers where the stiff chassis works great. At tracks like VIR with a lot of quick fast transitions, the chassis has been very happy.
Hope that helps,
Brad

thanks

So, even the CCW "special" 17 x 10 fitment won't work without tubular rear control arms? And if so, what about 17 x 9.5's on both F&R? I'm looking at 'new' wheels and I want to go as wide as possible. And will 275's fit on a 9.5-in rim?

10" wide wheels will fit statically but you will run into problems under cornering when the tire offsets. It will rub the control arm. the tubular bars are slightly narrower than the stock ones and you can gain a little more room with offset bushings at the Heim joint. On my current setup, the tire is 3/16" from the bar and it rubs a little when I corner.

275s on a 9.5 is pinching the tire. you may get it to mount, but thesidewalls are not happy. My suggestion is to take the high road, get the correct wheel/tire/suspension fitmet for your setup. You don't want to cut corners on your set up and drive 155mph into turn one.

Great thread guys....keep it up
Regards,
Crispy

PS Brad, the wheels are almost finished ;)

Seems reasonable to me, Brad. Definitely agree with the 275/40-17 Hoosier preferring a 10-inch wide. I'd go with 255/40-17 Michelin Cup Comps or 245/40-17; 245/45-17 Hoosier R3S03s on 9 or 9.5s. FWIW 245/45-17 and 275/40-17 Hoosier R3s03s are identical in height 25.3 inches. Rim widths would be 9 wide for 245 and 10 wide for 275.

Thanks for info. If this is going to be the case with the rear control arms, then what is the ideal spacing so that no rub occurs? And is there a way to approximate this using front/backspacing calculations?

Brad, I have the utmost respect for your opinion, but in looking at both the Hoosier, and the Kumho sites, the 275-40-17 measured rim width for both brands is 9.5". It seems to me that given this, a 9.5" rim is certainly not pinching the tire. On the Kumho, which I have on my Supra(17x9.5"),the sidewall of the 275 is both straight, and vertical. It behaves predictably, and shows perfect temps across the tread. Kumho lists 9-11" as usable rim width. The Hoosier as most of us know is a little different story, as they tend to like a little larger rim, still hoosier lists this tire as having a 9.5" rim width(9.5-11 usable). There was a nice article recently in Sport Compact, that talked about using various rim widths on the same size tire to vary the turn in and break away characteristics of a given tire size. One suspension tuner was using a wider rim on the front, for a vertical sidewall, and good turn in. On the rear they used a narrower rim, for a slightly rounded sidewall, and more gradual break away. Granted there are other ways to accomplish the same thing, but ity does represent another tool for getting the car just right. On a side note, I believe someone on the forum has run the 9.5" Supra rims on an FD. Does anyone know what's required to accomplish that? I would like to run these all the way around on my FC with 275-40-17s. (Already working on the widebody). Best regards, Carl Byck