jakermc

I know its an old topic, but I am ready to ditch my 6x7x16 street tires for larger track tires. If I understand right, I can go 7x8x16 or 7x9x16 without rolling the fenders. Putting 8x16 up front requires rolling the fender, correct? The car in question is an 83 911 SC with stock suspension at Euro ride height (25 1/2" f, 25") rear.

For now I am going to stay with the stock suspension and current ride height. Which set up 7x8x16 or 7x9x16 will give the best performance on the track? Is it true that 7x8x16 offers better balance and more neutral handling than having 9s in the rear?

Are 205/55/16 and 245/45/16 the tire sizes everyone is using?

I did read the archives, but I am still confused about the proper set-up for a track (Drivers Ed) car.

Bill Verburg

pretty much, each car seems to be a bit different. There are some that have reported touble especially w/ the left front, tires make a difference as well, not all nominally identical tires are physically the same size or shape

definately a yes here, but o/s can make a difference all the Fuchs that would be used on the front have a +23.3mm o/s, using a larger o/s makes fitment at the lip easier but increases the likelyhood of rubbing at the tub. +31mm is the largest commonly used front o/s for an 8.


I have used all of those fitments at one time or another, plus some others. I liked the 7&9x16 best w/ 205/55 & 245/45x16 tires, it fits the best w/ fewest hassles. Tune handling to suit w/ adjustable bars. If you wnt a bit more aggressive track set w/ a few more installation issues 8 & 9 w 225/50(or /45) front and 245/45 x16 rear will give the front a bit more bite and dial in a bit more oversteer.

That said for serious track use you will want the widest wheel and widest rubber(in general) that fits. Which means 235-245 front on 8s and 265-275 on 9.5-10s in the back. Fitment isn't easy and class rules need to be checked, they may prohibit some of the larger fitments.

Bill Gregory

If you haven't already, you can read the Fuchs wheel differences and track setups in the 911SC FAQ at tech.rennlist.com. If you're going to wider wheels, have your 911 lowered a bit and corner balanced, which will make a world of difference on the track. On my SC, I ran stock R compound tire sizes on 7x16's and 8x16's which worked well (the wider rims make the sides of the tire stiffer), and 8 and 9x16's too. 944 8's with 225's on the front requires a bunch of negative camber and possible rolling the fender lips or cutting the ender lips off. 9x16's with 245's in back are a natural fit.

You'll soon be thinking about slightly thicker torsion bars and upgrading your shocks. To tune your suspension to a fairly neutral position, you'll also consider adjustable sway bars.

Inside, in addition to the fire extinguisher that many groups require, you'll consider cloth seats with cutouts for a 5 or 6 way harness as well as a roll bar.

Enjoy!!

g-50cab

I have 944 turbo fronts on mine (8x16's) just required slight rolling. - Especially the driver's side front.

Ed Bighi

I presently run 16x7 and 16x9 with 205/55/16 and 245/45/16 Michelin Pilot Sport Cup for daily driving an track. I used to run 7's and 8's and liked it too. First with 225's in the back and later with 245's. The extra inch in rim makes for a slightly better foundation for the sidewalls though. Don't forget what is said in Paul Frere's book "The Porsche 911 Story" about what Porsche claimed was the case with rim sizes. It states "a same size tire on a larger rim provides more grip than a same size tire on a smaller rim." I also like the look of the extra hair of width of the 9's. But the 8 inch rears will really make a difference in grip even when using the same tires due to the wider track alone. To become a wide track believer, drive a 930 turbo with just 225's in the back and you will be surprised at the extra grip. For a while, I also ran 944 turbo 8's in the front with 225's to kill a little understeer. But adding camber there along with a camber brace the 30mm torsion bars I have in the back have negated my understeer to zero thereby requiring only a 7 in the front with a 205/55. If I were you, get 9's for the back and chuck the 7's in the front with the same 205/55 there. You will save money since 944 8's aren't cheap, and the extra track given by that 7 in the front will make a big difference in grip there. Trust me. But if money is tight, then put 8's in the back. You can't go wrong with Fuchs. The lightness/strength ratio is unmatched. Some of the potholes I have driven over in the decade or so of Porsche ownership would have bent any other rim. After all, I have bent every rim in every car I have owned except for Fuchs.

geo.aigel

Consider also 15 inch wheels. I have 7 and 8 by 15. A couple of my friends run the same size at DE with very good success. There are less clearance issues. You get some extra torque / steeper ratio from the smaller diameter and an automatic lowering of your car when you switch to the track wheels.

Take Ed's advice and stick to the fuchs. It is mandatory that you go with the originals, not reproductions. only the factory OEM stuff has the strenth and workmanship you want.

Cheers, George

jakermc

I'd already planned on staying with Fuchs - I am a big fan as well.

Sounds like a 7x9x16 upgrade is in order. I like the idea of not having to roll the fenders. Although I have 7s on my rear already, I may buy a new set of 4 rims and keep one set with competition tires and keep my current set-up mounted as they are for rainy days/street. I am currently leaning towards Toyo RA-1 as I understand they have a longer tread life than the others. Until my driving ability improves a bit more, I don't feel compelled to get the last ounce of performance out of a disposable item. (Though I do love my Pagid Orange pads)

One more question about running 7x16 up front. I took another spin through Bruce Anderson's book last night and saw that the 7x16 from the 944 Turbo has the same offset as the 911 rim but has the added advantage of providing more clearance for larger brakes. Would it be preferably to run with 944 Turbo wheels then so that I have an upgrade path later? What calipers are usually paired with this wheel on a 911? Do they appear identical in appearence to 911 rims?

Next years projects will be torsion and sway bars. I have alredy equipped the car with Recaro SRDs and 6 point harnesses.

Thanks for the help.

Ed Bighi

I noticed that part about the 944 turbo fuchs in Anderson's book as well. He seems to say in the book that they fit easier. But when I had it up front, the rim stuck out a bit more. At the time, I already had a tight fit with the 7's. Actually, it isn't unheard of to have to roll the fenders for 7's. This usually happens from not having the right amount of camber. Once you put some negative camber in the front, which I highly recommend by the way, then they will fit fine. Actually, you don't have to worry about brake clearance with even the 7's. Provided you upgrade to 930 turbo calipers and you grind the "Porsche" engraving there. Tight fit though. The way I look at it, just stick your rear 7's up there since they come free with the car. And if you ever decide to put bigger brakes, then worry about it. That way you have the luxury of taking your time finding that killer deal on 944 turbo rears since they are pricey due to their rarity. Keep in mind that the 944 turbo only had those wheels for a year. There aren't a boatload of them out there.

Don't worry about brakes. Make sure yours are working at 100% and you will have no problems. You will be surprised how many people out there have brakes that are in marginal state and think the actual system isn't up to par. Not true, it's usually the condition that isn't up to par. Luckily I had a friend convince me of that years ago when I thought I needed bigger brakes. But one mod I highly recommend for track duty is to remove the brake warmers (dust shields) from behind the rotors. This is a very effective modification on the SC and Carrera.

jakermc

Well, I didn't get Fuchs. I found a set of 7x9x16 OZ Racing wheels for a decent price. They are not as strong as Fuchs, but weigh about the same - approx. 18 lbs in the front and 19 in the rear. Not many pot holes on the track, so I think they will work well. Black centers with polished rims, so they do at least keep a similar look to the Fuchs.

I am going to mount Toyo RA-1 on them, 205/55 and 245/25. My question is about camber. The websites I have seen seem to indicate that camber must be between -2.5 degrees and -5.0 degrees, otherwise unusual wear will occur. This seems extreme. I am currently running with -1 degree everywhere. Should I put all 4 corners at -2.5 degress? What are you guys running with?

Alan Herod

Concerning camber, You pick up some negative by lowering, but not that much -- up front you will be lucky to get -1.5, and that will require some slight modification to the strut tower - slot mounting holes and clean the insulation goo off the top of the strut mount. Easier would be to switch to the offset suspension plates with monoballs, but I don't think that would get you to the extremes that you mention. I suspect you will more likely settle for something between -1.5 and -2.0 in front. The rear may be even more of a challenge without some sort of offset bushings. I think my SC is maxed at -1.7 in the rear with the adjustable spring plates. Someone else has probably got some ideas about how to gain more negative without radically altering the suspension.