James-man

Stock & original suspension on 86.5 with 75k miles, stock wheel sizes. Always have driven inexpensive street tires at the track. I am about to try R-compound tires for the first time.

Any tips?

What should I expect?

Should I adjust anything from the current factory-spec alignment in preparation for my first couple of days out?

Thanks!

RyanPerrella

WHY!

If you go from cheap tires to R compound your going to hate yourself. They will wear out in 5K miles. If your going from $50 per tire, to $150 you can get some good michelin's or bridgestone's. Why would you want R compound. Those really are a street legal track tire. I think Porsche has michelin pilot sport cup tires which are also R-compound on the GT3-RS. But nothing else. The CGT dosent use R-compound tires.

I would suggest against R-compound, unless you dont mind replacing tires every year or twice yearly. Its not that R-compound is overkill, its just totally the wrong tire for a street car. It would be like ....crap, i cant think of an example at the moment.

Dennis K

What brand of R-compounds? The difference in feel between brands can be as big a difference as between R and non-R tires. Generally though, a lot less audible warning of breakaway. Some tires are completely silent even when sliding. ALso, there's a narrower range of slip angle where the tire grips. Be prepared for the more sudden breakaway.

You'll probably see heavy wear on the outside shoulders if you run stock alignment. Again, the tire brand matters because they all like a different amount of neg camber. I think -1.5 would be a good number to start. I ended up at -2.5 but others here (who are faster) seem to run less. It really depends on your setup, tires, driving style. Get a probe-type pyrometer and take temps across the face of the tire after some hotlaps to find your happy place.

RyanPerrella

AHHHHHH

I didnt read that you "always use inexpensive r-compound tires for the track"

So yes you are tracking the car in which case its a good investment.

I like the Michelin Pilot cup sports personally.

Dennis K

What cambers do you run and what suspension setup? If I had the MPSC's up to the right temps, w/ the right camber and low heat cycles, they'd stick like velcro but damn, they were picky (and expensive). I'm curious about your experience w/ them . . .

mark kibort

go to world challenge events and pull a few sets out of the trash. (or buy a set of full tread RA1s if you only need to get 10k miles on them)
mk

RyanPerrella

I have no firsthand experience, I know just what automotive journalists have said about them. And based on that I dont think you can go wrong.

Take my suggestion with a grain of salt, i am no expert, I would consider myself a Michelin man, but I have Pirelli P zero's on my car currently, so what do i really know.

Last I checked MPSC tires should be about $200 each in a 16" size. A far cry from the $450 i have to shell out for 19" Pirelli's. So again cost is relative.

cdbtx

The biggest difference I noticed with R Compounds - They're very slippery when cold and offer little or no warning before they break loose. The first time I had them on my car for a track event during the 1st warmup lap I decided to apply a little gas around a corner to try and get a feel for them. Next thing I knew I was pointed in the wrong direction, followed by a stern lecture from the track officials.

It has taken me some time to get used to them, and now I would never run anything else. With time you develop a feel for the tires. The Pilot Sport Cups are the longest lasting and most expensive, the Toyo RA1's are an incredible buy comparably. To obtain the longest life and best grip for the track they should be shaved and heat cycled. I drove my car home from the track with the Pilot Sports in the rain - I could not get over 50mph without some serious sliding.

There are places to buy used R-Compound tires. A full set is the cost of a single Pilot Sport. It's been recommended to me to use street tires at track events because they do provide feedback. Sometimes during my practice sessions I'll run the street tires just for that reason.

James-man

75% of my driving is at the track. I already replace tires twice a year. I have two sets of wheels. If I can't get my car to turn in any better, I will probably ditch my 928 and get something else.

James-man

Oooops. I didn't read through all the posts before responding.

James-man

(please take my comment of ditching my 928 for something else - heat of the moment. I got to drive an Elise recently and that car was phenomenal! I've had my 928 since 1995 and it would be hard to part with it)

I just checked my last alignment sheet. Front: -.7 camber, Rear -1 camber. My last 2 sets of street tires had a LOT of wear on the outside edge. I am willing to go to -1.5. On my current street tires I usually run between 38 and 40 lbs hot pressures. Last event, I ran mid-40s of pressure to try to even out wear and make it through the weekend before cording the outsides. Is 38 - 40 a good starting point for Rs?

I am trying out a closeout set of Hankooks (Z211). If I like the direction they are going in, then I will consider higher $$$.

Mark - I don't know that anyone races with 16" tires, so dumpster diving may not work unless I move up the wheel-chain. I think Toyo still makes Rs in 16" sizes.

Thanks for the comments and tips!

Vlocity

I would start out with a set of Kumho Victor Racer 700. I've found them to be pretty predictable, great tread wear for an R compound and they are CHEAP. I'm able to get about 6 -8 track days out of a set before they are trashed.

As for alignment I am running my stock 85 lower control arm on the front with an upper control arm from an 87 up model year...the upper is shorter and allows me more camber than the stock arm is capable of....I'd start with the max camber and caster in the front. I doubt that you will be able to get more than about .75 degree....but it will help.

My settings are 2.5 degree camber in front 1.5 degree rear. max caster in front and about 1/8 degree toe in.

Are you running a stock width rim? Be sure to order tires that are well within the manufactures recommendation. You do not want to put a wider tire than recommended on a narrow rim....this will only create a lot of side wall flex and the car will not feel planted. I am running 315 on an 11 inch rim in the rear and 275 on a 9.5 in the front.

Is the rest of your suspension stock?

The next best money to spend is for an adjustable front sway bar and set of rear sway bar steroid links.

Hope this helps,

Ken

James-man

Yep - stock rims. I have both S and S4 wheelsets. Pretty nutty that I haven't gone wider yet.

Suspension is stock. I get some body lean now, but I'm used to it. I anticipate that it might become more pronounced with stickier tires.

Yes. Swaybar upgrade is on my mind. Over the course of the next 12 months...

1) Tires: see what happens
2) Swaybars
3) Seats & harnesses
4) Oil system modification

I may do #2, #3, and #4 in another order depending on how things go. My most frequent track does not have any long left sweepers, which is where I understand most oil problems arise.

I was looking at Quick Carl's web for swaybars. But we can talk about those later.... Thanks.

123quattro

If you want the car to turn in better, run the fronts slightly toed out. It will be twitchy, but turning won't be an issue.

SwayBar

You are running way too little camber both front and rear.
Those settings look good!