15x8 track wheels, what size tires: 205/50 or 225/45

I'm building my DC2 Integra GS-R for a time attack class next year (SCCA TT S6). The class doesn't allow for camber mods (no adjustable control arms, etc) and I'm not allowed to roll the fenders. 200 treadwear max, so alll the usual suspects: A052, RE-71RS, RT660, etc. The tire width limit is 225. No wheel width limit. 

Without being able to dial in more camber or roll fenders, I don't think I can run anything wider than a 225 (class limit anyway) on an ~8" wheel without making contact somewhere anyway. In truth, even with the perfect offset wheels, the 225's are probably pretty borderline to not make contact somewhere, in a class where fender rolling isn't an option; and an 8" wheel width is pretty much the widest I can go while still keeping the wheels under the fenders. 

Due to class limits, the car will be running on Integra Type R springs and Koni yellows, so it won't be terribly low (about 0.75" lower than a stock GS-R), which should help a bit in the not-hitting-fenders department. 

As such, I've already picked up a set of 15x8 +35 wheels (about the most ideal offset I could find for an 8" wheel on a DC2). 

My current dilemma: 

-Max out the class width, get a 225/45 tire. It should be noted that the RE-71RS and A052 are not available in a 225/45R15. The RT660 is available in this size, along with a few other 200tw tires.  
-Stick with a 205/50 tire, in which the tire selection is bigger (RE-71RS, A052, RT660 etc). 

Which would be faster on track? 

On a 9" wheel (which I can't fit), I'm sure the 225 would be faster... but on an 8" wheel, I'm not so sure. 

Thoughts? Experience with both? 

Thanks in advance! 

My experience is with a civic (Ek) chassis, not integra, but my guess is that you'll have rubbing issues with a 225 and such soft springs. That being said, the 225s will definitely be faster. I believe wider is always faster, even if pinched on the wheel (which an 8" won't be, even if a 9" is better). Check out GRMs tire tests with Andy Hollis and his crx.

Edit:

https://grassrootsmotorsports.com/articles/track-tire-buyers-guide/

Edit #2: some older info from Andy Hollis, scroll down to the bit on "optimal wheel size"

https://m.facebook.com/nt/screen/?params=%7B%22note_id%22%3A1075638742884465%7D&path=%2Fnotes%2Fnote%2F&refsrc=deprecated&_rdr

From the testing we've done, we find that a good rule of thumb is that the optimal rim is the same size (rounded up to the nearest half-inch or so) as the tread width (not section width!).  So a 205/50-15 tire with a typical tread width of 7.5" is best on 7.5" rim.  An 8" rim will work, too, but it will be majorly stretched on a 9.  Likewise, it will lose some performance on a 7, and will lose a LOT going down to a 6 or 6.5.  Similarly, a 225/45-15 with an 8.2" tread width works best on at least an 8.5" rim and loses a fair bit on a 7.5".

In reply to Run_Away :

Thanks for the feedback! I've read a few of Andy's notes in the past. I also noted Andy mentioned this in the same note: 

So a 205/50-15 tire with a typical tread width of 7.5" is best on 7.5" rim.  An 8" rim will work, too, but it will be majorly stretched on a 9.  Likewise, it will lose some performance on a 7, and will lose a LOT going down to a 6 or 6.5.  Similarly, a 225/45-15 with an 8.2" tread width works best on at least an 8.5" rim and loses a fair bit on a 7.5".

 

A practical example of this is in STC, STF and STS where the rim limitation of 7.5" keeps the 195/50-15 Toyo R1R at the top despite it not being the widest allowed tire size.  The 225/45-15 R-S3 mounted on that same 7.5" rim is not quite as fast.  But put that same R-S3 on an 8 and it comes alive.  And it's even better on something a bit bigger.  So in STR, where wider rims are allowed, the common 225 R-S3 on 9's is a faster combo than the 195 R1R on a 7.5 (assuming nominal weather).  And putting the 195 on an 8 or wider does nothing to enhance performance and close the gap.

 
Which would lead me to believe that since a 205 works ideally on a 7.5" wheel and a 225 works ideally on a 8.5" wheel, the ideal tire size for a 8" wheel is probably a 215. Unfortunately, 215/45 and 215/50 200tw tires don't exist. 

Somewhat related: I know Andy was running 205/50 A052's on this One Lap CRX. I believe he was running a 15x9 front and 15x8 rear staggered wheel setup, with 205's on both. I remember reading something along the lines of him choosing the 205's because the A052's didn't come in 225/45 and he didn't want the taller sidewall of the 225/50's. If I remember correctly, I believe he chose based on compound over ideal tire width, which makes me think I should just get the 205's in either A052 or RE-71RS. 

Although I think you might be right. Without rolling fenders, it might be a moot point if 225's are just going to rub anyway. 

It looks like on Andy's CRX, a 205 wide A052 (on staggered 15x9 & 15x8 wheels) was putting down roughly the same times as 245/225 staggered RT660 and Nankang CR-1's: 

https://grassrootsmotorsports.com/articles/200tw-showdown/?fbclid=IwAR1Hla6GhG7a25hH7mrZNFTfAckJkgEl7cKOctRgptb1qm-DZA1cVqSBUxY

But I did notice him mentioning the A052's needing a lot of camber... and I would be in a class where camber adjustment mods wouldn't be allowed. 

I'm very surprised you can't fit a 9" wheel on a DC2 Integra.

Yeah, for sure hard to chose when the faster compounds may not come in the larger sizing, or how some tires (RT660) run especially wide.

Eye opening example below, 225/45/17 rt660 on left, 235/45/17 re71r on right stacked two high:

The ST class civics 195 width R1R data point is a huge outlier IMO, that specific tire size has different compound than all other R1R sizes making it faster.

Is your integra 4 lug or 5 lug? The 5 lug cars have a slightly wider track width, requiring more offset for the same fender clearance.

ProDarwin said:

I'm very surprised you can't fit a 9" wheel on a DC2 Integra.

I can probably run a 15x9 in the front, but the rear looks pretty limited. My 15x8 wheels are pretty close to the rear trailing arm. I can run spacers, but that would push the tires further outside the fenders (15x8 +35 is just about perfectly flush). A 15x9 out back would likely require a good bit lower offset (likely in the 15-28 range) and the wheels would be sticking out of the fenders. Some people notch the RTA's for extra inner clearance, which isn't legal in S6 and even if it was, I'm not sure I'm comfortable with it. 

In reply to Run_Away :

My Integra is a 4 lug. 

I knew the RT660's ran wide, but good lord! Which makes me think 225 wide RT660's would likely give me some trouble without extra camber and with unrolled fenders... 

I didn't realize the 195 R1R was a different compound than other R1R's! Makes sense. Which again makes me think about choosing compound over width. 

Generally speaking wider is better. The stuff quoted above is about outdated tires and should be taken with a grain of salt though. Pretty sure I've seen testing by a few people that showed 205 a052s work best on 9" wheels.

Honestly I'm not exactly sure what the right choice is. I would have said 225 re71rs as they run a bit narrower than the others, until you said those don't exist. If you're worried about clearance, 225 a052s are probably out as they're the widest and will move around under load the most.

In reply to dps214 :

The RE-71RS and A052 don't exist in 225/45. They do exist in 225/50, but the diameter is almost an inch bigger, giving up quite a bit of gearing and making clearance even more of an issue. Most of the Honda guys seem to steer clear of 225/50's for that reason. 

At 225/45, the tires to have are the RT660, or maybe the newcomer, the N Fera Sport R. Although the RT660's are known to run wide for their sizes, so clearance might be an issue. Admittedly, I know very little about the N Fera Sport R, other than what I read in the TR test. 

At 205/50, tire choices open up quite a bit, with pretty much all of the competitive 200tw tires showing up. Either the A052 or RE-71RS seem like the tires to have at this size. The RE-71RS runs a bit more narrow. If they made it in a 225/45, I would likely give it a shot.

At that point, I suppose it comes down to: A052's and try to get it done in 1 lap... or RE-71RS, which seem to give you 2-3 laps before they fall off a cliff. The A052 seems slightly wider at 205, but it's also said to need lots of camber, which I won't have... not sure about the camber needs of the RE-71RS. 

I run a 225/45R15 on a 15x8 on my Fiesta and its worlds better than any 205 setup ive run. It was a camber limited car for a very long time. I had issues with 205's originally where no matter the pressure it would scrub the lettering off the sidewalls at 10/10th. 

Miata guys seem to love the 15x8 and 205 combo. Although, looking at Tire Rack and manufacturer websites, alot of the 205 tires arent recommended for anything larger than a 7.5" wheel.

 

I had a 94 civic with 15X6.5 Konig Heliums and I ran 225/45s on it. Absolutely zero issues with rubbing, and grip for daaaaayyyys. 

I think the only Honda guys using 225/50 are the ones who drag race....

I am running 205/50/15 RT660s on my 15x8 Enkei PF01 on my Integra, and they run a lot wider than the RE71r and BFG rival I used to run on the same wheel. Probably closer to a 215 width tire. My rears slightly rubbed my very mildly rolled (basically just enough to clear the RT660 and still look factory), but I also am running around -2.5 degrees in the rear to clear. Front's don't seem to have any issues with -3 to -3.5 degrees up front with no rolling.

I don't have pictures on the PC I am on, have pictures on my phone I can probably send you if you are on IG (same screenname). 

aw614 said:

I think the only Honda guys using 225/50 are the ones who drag race....

I am running 205/50/15 RT660s on my 15x8 Enkei PF01 on my Integra, and they run a lot wider than the RE71r and BFG rival I used to run on the same wheel. Probably closer to a 215 width tire. My rears slightly rubbed my very mildly rolled (basically just enough to clear the RT660 and still look factory), but I also am running around -2.5 degrees in the rear to clear. Front's don't seem to have any issues with -3 to -3.5 degrees up front with no rolling.

I don't have pictures on the PC I am on, have pictures on my phone I can probably send you if you are on IG (same screenname). 

 

Good info, thank you! 

I took a peek at Goodwin Racing and it looks like the 15x8 Enkei PF01 is a +35 offset? Does that sound right? If so, any rubbing on the rear trailing arms with your setup? 

Did you rub with the RE71R and BGF Rivals on the same wheel? Or just the RT660's? 

I don't have IG, but a quick Google search and it looks like your DC2 (the white one I saw) sits pretty low. I'm wondering if I'll run into the same issues since my DC2 isn't terribly low (stock ITR height). 

Have you tried running a 225/45 on those wheels? 

roninsoldier83 said:

aw614 said:

I think the only Honda guys using 225/50 are the ones who drag race....

I am running 205/50/15 RT660s on my 15x8 Enkei PF01 on my Integra, and they run a lot wider than the RE71r and BFG rival I used to run on the same wheel. Probably closer to a 215 width tire. My rears slightly rubbed my very mildly rolled (basically just enough to clear the RT660 and still look factory), but I also am running around -2.5 degrees in the rear to clear. Front's don't seem to have any issues with -3 to -3.5 degrees up front with no rolling.

I don't have pictures on the PC I am on, have pictures on my phone I can probably send you if you are on IG (same screenname). 

 

Good info, thank you! 

I took a peek at Goodwin Racing and it looks like the 15x8 Enkei PF01 is a +35 offset? Does that sound right? If so, any rubbing on the rear trailing arms with your setup? 

Did you rub with the RE71R and BGF Rivals on the same wheel? Or just the RT660's? 

I don't have IG, but a quick Google search and it looks like your DC2 (the white one I saw) sits pretty low. I'm wondering if I'll run into the same issues since my DC2 isn't terribly low (stock ITR height). 

Have you tried running a 225/45 on those wheels? 

Are you referring to the part of the trailing arm closer to the trailing arm bushing? My 15x8 PF01s are +35 offset and I don't rub on the rear trailing arm.  

With a 15x8 +35 you might make contact on the upper rear control arm, when I had the stock upper rear control arm, my Integra didn't hit on it, but on a test fit on my EK civic, it did make contact with the rim itself and a friend with an EG Civic warned me about his car doing it too. I believe people would notch the rear upper control arm or go with an adjustable rear arm. (I have an adjustable rear arm on it now). I recall people who had the +36 15x8 6ul wheel would have issues there too.  https://www.ebay.com/itm/175239491379 From that link, people notch that upper portion on the left on the first picture. 

For the 205/50/15 tire size, it went from narrowest to widest RE71r, Rival S, RT660. I actually got some minor rubbing on the Rival S which is why I added rear camber. I went back to the RE71r again after the camber so I am not sure if it would have rubbed, but the tire itself looked a lot more narrower and I never felt or saw any rubbing marks from the RE71r. But I had to do a mild roll to get the RT660 to clear that I didn't have to with the Rival. 

You might also rub at full lock up front hitting the fender liner, but nothing major. But I think even stock Integra 15x6 wheels at full lock doing any autocross or track day seem to hit the front inner fender undercoating...

I have not tried to run 225/45s just because I am a bit paranoid of destroying my fenders and want to keep it more of a street car first with the occasional track day and monthly autocross. When I was stock ITR rear I never ran 15x8s with it and only had 15x7s. 

In reply to aw614 :

Thanks for the feedback! Yes, I was referring to the trailing arm closer to the trailing arm bushing. I know some folks have had their tires rub on that portion of the trailing arm. 

I ran into the same problem in the rear upper arm area with my old CRX. I know some people notch them there or swap them out for later RTA's (for SCCA folks, the later RTA's are fortunately a superceded part number, so swapping to a later RTA is legal for Solo & TT). Fortunately, my wheels don't contact the RTA/upper arm on the DC2 (I test mounted the wheels as soon as they got here), I just wasn't sure if the tires would rub the RTA, close to the bushing. 

Shockingly, my current 205/50's on OEM 15x6 wheels haven't touched my inner fender liners. But I did have the same problem on my old STS/T5 prepped CRX. 

Thanks again for sharing your experiences! I think I'll just stick to 205's and maybe consider 225's sometime in the future if I ever decide to jump to a class where camber mods and rolling fenders is allowed. 

Once upon a time, I ran 205/50 on the 15x8 on my E30--things like RT-615 and the RS3. Then I tried a 225/45 in options like the RS3 and Rival S 1.5. The 225 was always faster but did feel slightly softer. Granted, tire tech has improved quite a lot from the days I tried 205, so maybe there is still something to learn there. However, I also run 225/45 R7 on the same wheels, which measure out at an honest 9.5" section width. Numbers would suggest those are pinched, but I can't fit a 9" wheel, and the car is just plain quick on them anyway. It is on my list to try a 205/50 R7 in comparison. I suspect the optimal width ratio is also a function of how the car (weight), track (surface), and driver (style) contribute to tire loading--hammer it and let the wider tire squish and work, or put the narrower option on and improve feel and precision.

Nockenwelle said:

Once upon a time, I ran 205/50 on the 15x8 on my E30--things like RT-615 and the RS3. Then I tried a 225/45 in options like the RS3 and Rival S 1.5. The 225 was always faster but did feel slightly softer. Granted, tire tech has improved quite a lot from the days I tried 205, so maybe there is still something to learn there. However, I also run 225/45 R7 on the same wheels, which measure out at an honest 9.5" section width. Numbers would suggest those are pinched, but I can't fit a 9" wheel, and the car is just plain quick on them anyway. It is on my list to try a 205/50 R7 in comparison. I suspect the optimal width ratio is also a function of how the car (weight), track (surface), and driver (style) contribute to tire loading--hammer it and let the wider tire squish and work, or put the narrower option on and improve feel and precision.

That's solid information! I suspect not a lot of folks have ran the same tire compound in 2 different sizes on that same wheels! Much less measured them to see how much of a pinch there might be! 

When you ran both sizes, were you running autoX or track? I'm curious, on average, what would you say the time difference was between the 2 tire sizes? 

I suspect I will still likely go with a set of 205's. Partially because of more available compounds (the RE-71RS and A052 appear to be a smidge faster than the RT660) and partially due to concerns I have with rubbing on a 225.

Looking at Andy's most recent test with the RE-71RS vs the RT660, I saw that he used a wider RE-71RS (245 vs 235), but said their actual contact patches were about the same... the differences in times was pretty substantial, which makes me think the RE-71RS is likely the tire to have, even if it's not in the bigger size: 

https://grassrootsmotorsports.com/articles/bridgeston-returns-200tw-scene/

Andy had mentioned in a previous review, that the new RE-71RS was a very different tire vs the old RE-71R, insinuating that the new tire was less of an autoX tire and more of a track tire. For time attack, in the 200tw classes, I think either the RE-71RS or A052 are the 2 compounds to beat (if only the A052 wasn't to intolerant to heat!). 

If I wear my 205's out at some point during the season and I've avoided rubbing and feel like there's a safe amount of space between the RTA and tires, or if I've stayed far enough from the fenders to give a set of 3mm spacers a try, I might swap on a set of 225's. But I am curious to see/hear how much time I might be leaving on the table. 

For what it’s worth, I ended up going with 205/50/15 RE-71RS tires on 15x8 +35 wheels and Type R springs… no rubbing on the real trailing arm, but very light rubbing under hard cornering or at speed over larger bumps in the road on the inner edge of the right rear fender. 

I probably wouldn’t know it was happening if it wasn’t for the high pitch squeak from the tire rubbing the rubber fender liner. 

I’m 100% sure 225 wide RT660’s would have rubbed, likely much worse.