djazzy99

hey guys;
i did a search, but couldnt find the exact info i was looking for. could anybody please tell me the exact wheel offset and bolt pattern i would need for a 1987 951 for the size 17x8 in front, and 17x9 in the rear? i am trying to buy track wheels. thank you.

Ski

Danno

Be very, very careful about using that chart from the 944-FAQ, it's got numerous errors that'll throw you off. Like the stock '87 16x7 and 16x8" wheels. There's no way you can have two wheels of the same offset with different widths ending up with the same backspacing. The 1" wider 16x8 wheel should have a backspacing that's 0.5" wider than the narrower 16x7" wheel if they're both to have the same offset.

I recommend learning to measure your wheels directly and computing your own dimensions as needed. I've got the procedure, diagrams and equations on the "944 Wheels FAQ" section of my 951 RacerX website.

For an '87 951 with 17x8"and 17x9" combo, I recommend the following:

F: 17x8", 60mm offset, 225/45-17 tyre (increased offset to prevent rubbing fenders with wider tire)
R: 17x9", 52.3mm offset, 255/40-17 tyre

GeorgeNZ

Hey Danno - BTW stock front for the 88 TurboS CS wheels is x7" not 7.5"
ET is Good

Danno

Thanks George! Also the chart lumped all '87-91 cars together for stock wheel sizes. Didn't the '89+ cars have the same wheels & offset as the '88 TurboS?

sybelix

Hi Danno, actually the 951S had Club Sport wheels,7*16 ET 65and 9*16 ET 60
MY90 & 91 7½*9 Design 90 ET 65 and 9*16 D90 ET 52,3

djazzy99

thanks guys. Danno, you're right about the tire sizs, i already have my car set up with the confiuration you recommended, but i bought them from somebody who already had them on his 88 turbo, so i didnt need to check for offset or bolt pattern. now that i'm buyign new rims for the track, i had to find that info. has anybody ran 10" in the rear??? clearance/spacing issues??

moreboost

forgive me for being ignorant about this, but since the 944s are balanced naturally already, wouldnt you change the handling by running such a staggered tire setup like 8 and 10 inch wheels? a 35 mm tire width difference doesnt sound like that much, but wouldnt the front tires give up earlier, all things being equal? or did i miss an important concept? can you "balance" it back out with swaybars or spring rates? on a stock car, 8 inch wheels seems like a nice comprimise for the fronts and the backs. tia, im still pretty ignorant when it comes to suspension setup.

take care,
brian

Danno

"but wouldnt the front tires give up earlier, all things being equal? or did i miss an important concept? can you "balance" it back out with swaybars or spring rates?"

Vertical weight loading is what gives the car its F/R weight distribution sitting still or moving in a straight line. However, once you introduce the spectre of cornering, there's a lateral shift in weight to the outside wheels:

This shift doesn't have to be 50/50. It can be 60/40 or 40/60 depending up on the springs and sway-bars. Looks like like this:


So rather than the 50/50 you might expect to be optimal with a 944NA with equal size tires all around, you might want go with a 45/55 F/R distribution of lateral weight transfer to take advantage of the larger rear tire.

Another aspect aside from cornering grip, is drive traction. With larger rear tires, you can have extra grip on the rear tires when the front has hit their limit. This will allow you to get on the throttle a little sooner coming out of the corners. This can give you an additional 5mph down the straights and faster laptimes, even if cornering speeds were still the same.

"has anybody ran 10" in the rear??? clearance/spacing issues??"

I'm running 17x11.5" in the rear. The sidewalls of the tires will rub on the inner and outer fenders at about the same time with over 3" of suspension travel. Although I think this is largely due to the 1" taller 275/40-17 tire compared to stock. Once I get 1" wider fenders, that shouldn't be a problem any more...

ian kam

a quick note if you are ever going to upgrade to bigger brakes figure out the offset ahead of time to fit these brakes. I'm having trouble with my rims right now stock brakes fit no concerns with big reds no fit. Now the rims are going back to kinesis to have offset redone. Save time and money do it right the first time!!! Just a hint if your like many of us constanly upgrading.

Andrew Wojteczko

i just checked my kinesis 17*9 K20's with S4 big reds and 928 S4 rotors up front, cleared with tons of room, which big reds are you using?

Thanks,

Andrew Wojteczko

David Floyd

S4's are not Big Reds

djazzy99

s4's are the same size as "big reds", but are just black. he is referring to a set of 928 s4 brakes that have been painted red.

Danno

"s4's are the same size as "big reds", but are just black."

uh... no...

djazzy99

hey guys, i did some checking around, and i got my info about the s4/big red calipers from a site called 944s2.com. in his brake section, he went on to explain

"Therefore, I chose the 928 GTS "big black" calipers. These calipers are physically the same size as the big reds and use the same size brake pads. However, since they are meant to mount in the trailing position they are a true bolt-on option. "

"The piston sizes used in the big red or GTS 4-piston Brembo calipers are the same size as those used in the M030 option S4 calipers, namely 36 and 44 mm. The brake pad width is also the same 132 mm. However, the brake pad depth is increased substantially to match the larger rotor diameter."

that is where i must have red about the s4/big red caliper mix up. can anybody clear this up for me? ie- differences etc...