JimmyT

I posted this in the 987 forum, but figured many of you with great knowlegde but other cars may not venture in there, so I'd post the question here as well.
I'm considering a set of track wheels & tires for DE use for a base boxster. Here is what my (reasonably close size) options appear to be. All would be mounted on OZ alleggerita 8x18 and 9x18:

Stock size - only option:
Bridgestone RE-11.
235-40-18 25.4" dia
265-40-18 26.3" dia
dia ratio = 1.031

In alternate sizing I see these options:

Direzza star spec
225-45-18 25.1"
275-35-18 25.6"
dia ratio = 1.02 is close to stock and car would be lowered about 0.35" front and rear. This could be great as it also lowers gearing about 3%. But narrower front with wider rear seems less than ideal.

I could get nearly the same effect of reducing overall diameter slightly, but keeping F/R dia ratio by doing this:

Kumho Ecsta XS
245-35-18 24.8"
275-35-18 25.6"
dia ratio = 1.032 Again slight lowering of car and gear ratio. Perfect dia ratio.

And finally narrower front but stock width rear:
Advan A048 (rcomp) or MPSC:
225-40-18 25.0"
265-35-18 25.2"
dia ratio 1.01. This is nearly matched F/R diameter, but would lower the rear a lot.

Or:
Toyo R888 (rcomp)
235-40-18 25.3"
275-35-18 25.7"
dia ratio 1.016. This seems to be a slightly better option than Yok's & MPSC.

I assume that any options of 235-40-18 with 265-35-18 are a bad fit as there is no F/R diameter stagger, and rear ride hight is lowered vs front. This is the size combo that seems to be most widely available. Here is what I want your feedback on:

1) I don't mind the idea of a little smaller overall dia, as it will lower the car just a bit, reduce gearing a bit, reduce unsprung weight (and moment arm), all point to better performance. That's not what I'm specifically trying to achieve, though, just a side benefit.

2) I think I should try to keep the F/R ratio about stock, which means stock sizes or lowering dia on both ends about the same. Not doing this can fool electronic gadgets and mess with balance of car, right?.

3)If using these set ups for driving to/from track and DE weekends will the R comps be noticibly better on track?

4) will they wear noticibly faster than the non R comps? I will can get about -1.0 front camber on my car, but I'm worried about outside wear, and wonder if R comps might be more durable in this regard since the tread is more solid and handles heat better.

Thanks in advance for sharing your expertise.

Jim

Bill Lehman

On a Cayman, I ran 245/40 x 18 F and 275/35 x 18 R using Toyo R888. This year I'm running MPSC 235/40 F and 265/35R. In the dry, I'm liking the MPSC better. The R888 were acceptable in the wet but not great, haven't tried the MPSC in the wet yet. I drive to and from the track on these tires.

JimmyT

Thanks for the reply. No issues due to the rear diameter being smaller and the F/R stagger being different on either setup, then? Does it look funny, meaning nose high?

Bill Lehman

No issues at all with the Toyo setup. Still learning and adjusting the MPSC setup. The front does not look high but the rear wheel wells look hugh with the Cups but there is no other size option with this tire. I experienced some ABS issues on my first outing but do not know if it was caused by the tire diameter. The last event had no brake issues.

himself

You should just pony up and get a separate set of track wheels with RComps. It'll make life a lot easier in the long run.

FWIW, I never liked running MPSC for DEs. They take too long to heat up - especially compared to Hoosiers or even Toyos [I ran RA1s]. Depending on your session length, it might eat up 10-25% of your time. That being said, when they were hot, I didn't notice much difference in lap times.

Oh, and the only blowout I ever had at the track [*knock wood*] came on MPSC. Doh!



-td

J richard

Only suggestion I would make is running Nitto NT01s instead of the 888s, much better tire, more consistent and won't HC out with plenty of tread like the 888s...

e9stibi

What is your experience on the track? If you are still a "beginner" I would stay an street tires. They are much better to support your early learning objectives in your track career and give you much easier to handle feedback when you get closer to the limit.

Just my 2ct

JimmyT

Novice class. I'm more interested in durability of the tires than ultimate grip, so the only reason I included some r compounds was thinking maybe due to tread block design they might actually be as(more?) durable on the outside edges with the low stock front camber I'm running.

My main question is the specifics of the size alternatives. Stock sizes are hard to come by for the rears, and I don't want t make any mistakes when it comes to relative diameters between F/R. RE-11's will work great at stock sizes, but they are a little pricey and aren't reversible, like the star specs would be, for example, making them effectively even more expensive. So I was just exploring other alternatives.

Jim

Dave DE

In my opinion, if you are looking for more tire longevity you will need to increase front camber beyond stock regardless of what tire you are running.

As for sizes, I've had good luck with 245/40-18 and 275/40-18 on my 987cs. I chose these to try and retain close to the stock front/rear stagger. I've used both 888's and NT-01's in this size and prefer the NT-01.

JimmyT

Yeah, I'm going to have the front camber maxed, but not going to do GT3 lower arms or camber plates. I was considering the Kumho XS in the 245-35 & 275-35 sizes to accomplich just what you did in keeping the F/R dia ration unchanged, and the price compared to the others.

KS-CS

You might want to look at the Nitto NT-05s, which are probably a little more durable than the NT-01s, and $100-200 cheaper/set - I ran on them last season and was pretty pleased with them once they were broken in. You could run either 235/40 or 245/40 on the front and 275/40 on the rear, which would fit your rims, and shouldn't cause any problems (a lot of Caymans run 245 front and 275 rear on the track).

I had 275/35 NT01s, and they did look a little too small in the rear wheel well.

JimmyT

The smaller diameter "look" did occur to me with that 275/35 rear. Since it's a track only tire wheel setup, I don't think I'd mind, especially since it would have a performance benefit to gearing, unsprung weight, COG slightly lower, etc. BUT - How bad DID it look? And did you like the effect on gearing?

Jim

KS-CS

Well since I have the stock suspension (not lowered) it looked a little bit like an SUV in the rear.

I also thought I would benefit from the slightly lighter weight and improved final gear ratio with the smaller diameter tires, but I'm not sure that in reality, I could appreciate any difference on the track.

JimmyT

Ouch. SUV isn't good. Thanks for the feedback.

Jim