what are you running on 16" Fuchs?

[rdane]

I have 944 8s up front and 9" 930s in back. Currenly I am using 225/245 RA1s.

But I am still getting some rubbing on hard compressions - bumps with drivers side front. Fenders are rolled and I am running 1.5 neg camber and can't seem to get any more with the car as is.

I am pretty tight up front and figure the 225 RA1 is pretty much all I can get in there.

But I have some room in the rear for a bigger tire.

I was thinking about trying Hoosiers, 205/45 and 245/45.
By Tire Racks specs it would be more tire and less weight and a bit more room up front.

Looking for a hill climb tire. So small cir. for gearing and light weight do make a differenece.

Are there other tires/sizes I should look at? Suggestions?

[rdane]

Thanks Noah. I ran 17 Fiskes for awhile with 235 and 255s. You are correct there was no rubbing.

Don't want to add any weight. Also an issue to get Lindey's to fit without spacers and longer lugs over the 930 brakes. Adding another 1/2 on the 255s in rear tire dia. won't help my gearing either. Not a big deal on the track but a liability in a hill climb. Hoosier will save me another 16#s in unsprung tire weight as well.

Anyone running the Hoosiers on 8/9s?

[RaceProEngineer]

rdane,

The first question which comes to mind is, "What are the rules of your class in the hillclimbs?" More specifically, are you required to use a "DOT approved" tire? Stock wheel sizes?

As you so correctly point out, the lower the profile of the rear tires, the greater the torque. Likewise, your point about unsprung weight ( in this case, wheel+tire ) is critical, and right on the money! However, an area you might be overlooking, because it seems so obvious, is mechanical GRIP. Without it, all the rest is just fanciful theory . . .

So, IF we were running hillclimbs or Solo Ies, and IF we were limited to near-stock wheel sizes, and IF there were no restrictions on rubber, we would have a set of soft-compound GoodYear or Hoosier slicks - without question. Supreme GRIP!

Assuming you need to stick to (pun intended) DOT Approved tires, Hoosier A3SO4 s ( or maybe now the new A3SO5 s ) are unbeatable. They come in nominally 225-50 16, and 245-45 16, but placed side-by-side with other "R" radials, they have a much lower profile, which should help your front rubbing in bump mode. The "A" compound is made specifically to heat up quickly, where one does not have the luxury of 1 or 2 full laps to get them up to optimum traction. GRIP!!

Good luck,
Ed LoPresti

[911-32]

I would look at this another way. Why are you rubbing? Because you have "only" 1.5 degrees neg camber. I managed to get within a whisker of 2 degrees by running a fairly low ride height and cranking the strut brace in a little. I have been using 225/45 track tyres which have never rubbed, though previously 225/50 road tyres would occasionally touch. I am now thinking of getting the Wevo Camber King strut brace and sperical bearing package that promises an extra degree of camber on torsion bar cars as the track tyre I want only comes in 225/50 or 205/45 (too small imho). After thinking of different wheels and tyres I have almost decided that the Wevo product at USD700 is actually the cheapest option allowing me to keep using my 2 sets of 16 inch Fuchs.

As you no doubt know, most r-compound tyres like at least 2 degrees of neg camber to perform at their best. So its a win:win really.

HTH

[greglepore]

If you're really looking to get a gearing advantage, I'd seriously look at 15x7 cookies and used 15 in canti slicks-cost effective and serious grip, assuming you can run slicksin your class. Very light as well.

[RaceProEngineer]

Greg,

Perhaps you missed it, but rdane is currently running wheels which are 8" wide in front, and 9" wide in the rear. Unless we are missing something, your suggestion of 7" x 15" Cookie Cutters would have three immediate effects:

(1) Reduce total contact patch by more than one square foot!
EDIT: One square foot - WOW!! I meant 1 LINEAR foot - actually between 13 to 18 square inches.

(2) Reduce front and rear track by ~ 2 inches each.

(3) Add some unsprung weight, at least in the wheel department.

All of these seem counter-productive to retaining or improving performance in hillclimbs. Unless we are overlooking the very latest "trick" setup, he would need some really COMPELLING reasons to follow this course of action.

Ed

[greglepore]

Ed-
I'm talking cantilever slicks-the "standard" size for a 15x7 wheel is 9.5x23x15, a 245 tire is 9.6 inches, so you give up almost no contact patch. The sidewall is very bulged, hence the "cantilever" name, to give a useful contact patch on a narrow rim for various roadracing applications with wheel restrictions. The tires are extremely low profile, and run on 15's so you get a greater gearing advantage, which was a stated goal. The cookies are heavier than Fuchs, but not by much, and this is entirely offset by the weight advantage of the tire.

The other plus is cost-you can get a set of used 15x7's for 2-300 bucks, and used canti slicks are readily available in everything from 25 to 55 compound for 300/set or so, with 70% or better "tread".

Edit-what I did miss was the 930 brakes-you would need spacers and longer studs to use cookies with 930 brakes-I have this setup on the 914-6-but the expense is offset by the wheel cost. For the street wheels, you just run open lugs to clear the longer studs.

[RaceProEngineer]

Hi again, Greg,

At the risk of hijacking rdane's thread, we are certainly more IN agreement with you than not. That is evidenced by our original advice to him as a preferred solution, "we would have a set of soft-compound GoodYear or Hoosier slicks - without question. "

We would not "go backwards" in rim width, however, especially on the rear. In addition to the contact patch deficit, by narrowing the track, in particular in the back of a 911, one invites even greater lateral weight transfer.

You have an excellent point about Cookie Cutters as opposed to Fuchs or BBS when cost and availability are the primary considerations. When lap time is the driving factor however, we would use the lightest/strongest (and widest) wheel we could find. And YES, we too would prefer 15" diameter for this application.

As to the used slicks, it is more a matter of preference (or philosophy), but, for us, if the entire event hinges on three or four quick laps (or runs), we would want the softest compound, freshest rubber we could find. There are very good reasons why those "70% slicks" cost 30% of the new ones! Those first few millimeters of rubber are like gold.

Incidentally, I believe Hoosier has discontinued the R25 and R25A compounds in all the 15" diameters except for Formula Atlantic.

Lastly, thanks for not jumping all over my "one square foot less contact patch" statement - I must have had one too many turkey sandwiches . . .

-Ed

[rdane]

Thanks for the additional info guys.

One of the local hot shoes runs 8x15s Fuchs all around and R rubber on his light weight 3.6 and does very well on the track against much "better" cars on a regualr basis.

I had thought about 7 and 8 x 15" Fuchs and adding longer studs but was worried about loss of tire contact patch, braking, traction ect. with the smaller tires available.

I can legally run anything in class (wheel and dot tire) that will fit under the car.

The hill climbs/time trail is always on cold tires and under 3 miles long.

Top speed on the straights is under 90mph. So it is all 2nd and 3rd gear. But it is a exercise in "squirt" technology and torque if you can stay glued to the road. The R rubber should give me a bit more speed to carry through on to the straights. The highest top speed in the trap wasn't the fast run on the hill which surprised me. So cornering and top speed have to balance each other out to have a good run time.

Most of the gearing is already there in a purpose built short gear box. I just don't want to give up any of 2nd or 3rd gear to a larger tire dia.

Stick to the A3SO5 on the 16" wheels? Or build a 15" wheel set with the same tire?

I appreciate the help, thanks.

[greglepore]

If you're set on the A3SO5 rather than slicks, then by all means stay w/ the 16's as the sizing in 15 is too limited and gives up too much in the rear. Sorry we got off tangent with the slicks discussion as you can't run them anyway.

[rdane]

It is all good info....thanks.

[PcarPhil]

Originally posted by rdane
Thanks for the additional info guys.

One of the local hot shoes runs 8x15s Fuchs all around and R rubber on his light weight 3.6 and does very well on the track against much "better" cars on a regualr basis.

Is this on a 911? If so, what year and what flares?

Also, do you know how the front fitment is and what size tires the hot shoe is running?

Do you have any pics?

Thanks,
-Scott