Tire Contact Patch at Track, info needed

[Kemo]

All,

I currently run 16x7 and 16x8 fuchs with 225's up front and 245's in the rear on my 78' SC. I was thinking of going to Keizer 15 inch wheels and running the new/er Toyo Proxes RR ( TOYO Proxes RR Tires Direct ) which look like a great tire. Unfortunately, they only come in 225's and 205's.

I have heard alot of things concerning Contact Patch and was wondering if i would be doing myself a dis-service going this route.

The reasons for this consideration include the difficulty finding 16" tires and lower cost of tires. My other option would be 17" where there is a whole host of tire options. I have heard that I can get a slight gearing advantage going to 15s

as always, thanks in advance for the input...

[Cajundaddy]

The Toyo RR is a tire designed for spec racing with very limited sizes available. I'm not quite sure where you are coming from or what you are trying to accomplish.

Some things to consider when choosing a tire compound:

Driving experience in years or # of track days?
Current tire and exact sizes?
All up weight w/driver?
RW hp?
Club Racing, Time Trials, or DE?
Track use only or dual purpose street/track car?
What suspension and camber is available to control your contact patch?
Goals? Regional championships, beat my friends, DE for kicks and grins?

Give honest answers to these questions and you will get useful tire advice here.

[Cory M]

Why take chances with a brand new tire design in very limited (and wrong) sizes when you can get the proven performance of a Hoosier in practically any size? The last new racing tire Toyo released (R888) was a huge disappointment, it was so universally hated that they had to bring back the old tire it was meant to replace. Unless there are Toyo contingency $$ on the line it doesn't make sense to me.

I agree with Cajondaddy, more info needed, lots of fast 911's out there on everything from 15-18" wheels...

[Kemo]

Thanks for the response...here is a follow up to answer a few questions.

my car is a 78' 911 with stock motor, early style heat exchangers, bursh style franken muffler. So probably 180HP. I have only been doing DEs so far running RA-1, 225/50/16 Front, 245/45/16 Rear. Smart Racing Sway bars, 23mm/31mm torsion bars with matched revalved bilsteins, Rennline monoballs front and rear with Rennline triangulated tower brace, sway-away adjustable arms. the car has been stripped a bit, no a/c with spartan interior, fiberglass bumpers, sparco evos and an Autopower bolt in cage. I would estimate the weight to be about 2785 with me in it (i weigh 185ish)? I dont have an over aggressive alignment, but I think with this next set of tires ill have it done at a good speed shop and get it corner balanced as well since the car is track only at this point. the proxes RR have been compared to a shaved RA-1, which is why i was interested in the product. My goal, for now is to continue to learn to drive but set myself up for club racing if I ever get that good. And, should I ever make it to club racing, ill be on hoosiers. In the mean time, im just trying to maximize my dollar when it comes to tires and the RA-1s seem to be the best bang for the buck. Ill probably stay with those and wait to see how the RRs pan out. It seems the RA-1 on 15s, only come in 225/45, 225/50 and 205/50. I was just wondering about the grip differences between the different tire widths.

[Bill Verburg]

The Toyo RR is aimed at the Hoosier market, why not look at R6?

here is a comparison of some tire options on an SC


The shape of the contact patch is the important factor, a wider/shorter contact patch runs at lower slip angles and thus runs cooler and can generate more grip than the same rubber compound w/ a longer/narrower one

you get shorter /wider patches from using lower wider/lower profile tires

ie a 275/35 will have a shorter/wider contact patch than a 275/40

additional benefits can be obtained from shorter tires, a 275/35 x15 and 275/35 x18 have pretty much the same patch but the 15 is much shorter, the benefit depends on the specific gearing needs that are extent, some users will benefit and some won't

[Cajundaddy]

Ok good info. It looks like you have a pretty good setup to make use of racing tires but you are not racing yet. With that much car weight and no championships on the line I would stay on RA-1s or NT-01s. They are excellent track tires and are probably good for 8-10 days if you take care of them.

The RR is a 40tw DOT-R racing tire that will be ready for the dumpster after 3-4 days. You could go with a narrower, stickier compound tire but I think it's money down the rathole. One of our Boxster buddies is doing this in order to run in a lower car class but his lap times do suffer a bit. As you suggest it is probably better to stay on tires that are sized for your car at the track and focus or really getting suspension and alignment sorted. Don't forget to tighten the nut behind the steering wheel while you are at it.

[racer]

In my older days (before I could afford to step up to "hot set up" 16"s) I ran 15" with 205/225 combo. this was in the early 2000s. This was a very popular set in the 1970-1980s, less so by the late 1980s... just saying.

Since you aren't actually racing, all you stand to lose is the DE championships anyway Get what fits your budget and needs for now. You'll be spending plenty on Hoosiers soon enough.

You might like the gearing change.. you might not. If you run a lot of long straights, the skinnier tires might help your aero, at the cost of slight cornering speeds. Ahh tradeoffs.

[Kemo]

thanks for the great replies...it seems the RA1 is really loved by all when it comes to longetivity(sp?). after thinking on all this and viewing Bill's chart, I believe I'll stay with the 16" wheels and go with the Keizer-Buckley wheels if and when I make the jump to competition. I do think I would benefit from a ride height, alignment and corner balance. Its so tempting to throw some money at the car in hopes of a few seconds here and there. As mentioned, a tightning of the nut behind the wheel might make the most cost effective change