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Max Wheel/Tyre size for C2

 
Old 02-24-2010, 05:58 AM
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Racker79
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Default Max Wheel/Tyre size for C2

Hello All,

I was wondering what the largest wheel size/offset and tyre size is for a 964 C2?

Best Regards

Stefan
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Old 02-24-2010, 10:27 AM
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LastMezger
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I can only assume my rear tire fitment is the largest without moving oil lines and rolling the fender lip (I had to massage the passenger side with a broom handle;-).
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Old 02-24-2010, 06:25 PM
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suezen
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I can see in your signature that you have 9,5" wide ET47, but how wide tyres do you have?
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Old 02-25-2010, 01:01 AM
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LastMezger
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Originally Posted by suezen View Post
I can see in your signature that you have 9,5" wide ET47, but how wide tyres do you have?
265.

M
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Old 02-25-2010, 01:20 AM
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nidon
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Originally Posted by Racker79 View Post
Hello All,

I was wondering what the largest wheel size/offset and tyre size is for a 964 C2?

Best Regards

Stefan


hi there Stefan, I'm running 18 x 9.5 (265/35) ET47 and 8 x 18 (224/40) ET52 withouthout problem. Lowered on eibach springs without issue on a C4
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Old 02-25-2010, 08:20 AM
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Racker79
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Thank you very much for info. Iam looking at the 17inch cup wheels as wide as possible.

aparently anything larger that 17 inch is not approved by porsche. would like to know if anybody ever had issues with 18inch wheels.

http://www.pcarworkshop.com/images/d...0593geolab.pdf
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Old 02-25-2010, 01:49 PM
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Just needed a spacer. 15mm in the back.
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Old 02-25-2010, 05:29 PM
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I do like the look of 18inch.

I found this website which is quite good.

http://www.944racing.de/reload.php?u...ngewichte.html
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Old 02-26-2010, 01:35 PM
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964 and 911 SC/Carrera rear wells have just barely enough room to fit a 275 tire on a 9.5 or 10" wheel. Whether it is 17 or 18 is pretty irrelevant except that it alters the available tire choice

in 17 275/40 there used to be some great 265/35 but they were very rare and were only available for a few years
in 18 265/35 it would be great if 275/30 were available but I haven't seen any, you might be able to squeeze 285/30 if everything was perfect and you din't mind a little body work

factory Cup cars used 9.5x17 ET47(wheel ET68 w/ a 21mm spacer)
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Old 02-26-2010, 08:22 PM
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Hi Bill,

just looked at you http://members.rennlist.com/1976c38/index.html which is excelent.

Stock cup wheels are:
7 ET55 which would fit 235/? max
9 ET 55 which would fix 265/30 max

you could also argue that 8 ET 55 at the back saves 1.2kgs each. but I don't know if you could fit 265 and I'w like a bit more tracktion.

So when I have ET55 and I add a 10 (1cm) spacer the offset is reduced to E45 pushing the wheel away from the car making a bit more space between tyre and body.

When using spacer would I always use the same size for the front or back or would you reduce the front a little less? or does it depend on the tyre size. I gues the tyres should be allined. So I mean the front tyre to run in the middle of the rear tyre. If I would decrease the offset at the rear only the front tyre would run on the inside of the rear tyre. What works best ?

I am lookig for advise on my tyre , wheel and offset size whch has proven to work.

My aim is to fit 17" cup or 18" speedline wheels which the biggest tyres availabe and an off set that the wheels are flush with my narrow body.

Has anybody ever had any problem runnig 18" on C2??

Stefan
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Old 02-26-2010, 09:48 PM
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Bill Verburg
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Originally Posted by Racker79 View Post
Hi Bill,

just looked at you http://members.rennlist.com/1976c38/index.html which is excelent.

Stock cup wheels are:
7 ET55 which would fit 235/? max
9 ET 55 which would fix 265/30 max

you could also argue that 8 ET 55 at the back saves 1.2kgs each. but I don't know if you could fit 265 and I'w like a bit more tracktion.

So when I have ET55 and I add a 10 (1cm) spacer the offset is reduced to E45 pushing the wheel away from the car making a bit more space between tyre and body.

When using spacer would I always use the same size for the front or back or would you reduce the front a little less? or does it depend on the tyre size. I gues the tyres should be allined. So I mean the front tyre to run in the middle of the rear tyre. If I would decrease the offset at the rear only the front tyre would run on the inside of the rear tyre. What works best ?

I am lookig for advise on my tyre , wheel and offset size whch has proven to work.

My aim is to fit 17" cup or 18" speedline wheels which the biggest tyres availabe and an off set that the wheels are flush with my narrow body.

Has anybody ever had any problem runnig 18" on C2??

Stefan
Don't confuse Cup1 wheels(aka Cup design 92) w/ the wheels used on the Cup race cars.
964 cars including RS came w/ the following wheels in the Cup 1 design
aluminum
7x17ET55, 7.5x17 ET55, 7.5x17 ET65, 8x17 ET52, 9x17 ET55, 9.5 ET68

magnesium
7.5x17 ET55, 9x17 ET55

some of the above used spacers, for instance the 9.5 used a 21mm spacer.

Some of the wheels can optionally use a spacer depending on what the intent is, usually it's cosmetic but track width also affects handling
increased front track - less under/more over steer
increased rear track just the opposite

similarly w/ wheel and tire width
wider front less under/more over steer
wider rear just the opposite

no you don't have to use the same spacers f/r

each different wheel width wants different tire widths and cross section
9x17 can use anything from 225/40 to 275/40 tire
a 9.5x17 cuts from the narrow end and adds to the wide end, can use 235/40 to 285/40
for best performance you want to use a tire at wide end of the wheel width spec, for best comfort you want to choose a tire at the narrow end of the wheel width spectrum

in 18 inch sizes you generally run the same widths but w/ a lower cross section

the bigger the tire and wheel the less room you will have on either side so there is less room for ET that is off a little.

in 17 know good combos are
8x17 ET52 w/ 225/45 or 235/40 tires w/ 9x17 ET55 255/40 or 265/40 in back

in front you can't go wider w/ the wheels but a 245/40 x17 tire can be fitted if you go through some extra steps in setup. In back the 9.5 ET47 w/ 265/40 fits pretty well 275/40 can be fitted on that wheel or a 10 w/ some extra care in setup

in 18 the same width and ET are used but the tires would be 225/40 or 235/40 front and 265/35 or 285/30 in back

the smaller widths gives more latitude if the ET is slightly off.
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Old 02-27-2010, 01:48 AM
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I am running what I believe to be the max possible on the narrow body.

F: 245/40R18 ET56 8.5" Rim
R: 275/35R18 ET65 20mm spacer 10" Rim

I have the ovalized oil line in inside rear and it's very close on the inside and just clears the fender on the outside with max camber w/o ERP bits.

On the Front, I have -1degree+ camber and it fits pretty good but I have the upgraded steering spacers. It rubs at full lock.

If you don't have very stiff suspension you will get rubbing with this config. I have the Cross config with the 800lb springs (IIRC).

Here is a pic:
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Old 02-27-2010, 01:50 AM
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Oh, and you need extended studs in the rear to handle the spacer. I have PMNA spacer from the period and had to work very hard to get the correct stud lengths.

Also, my tires are RA1
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Old 02-27-2010, 06:39 AM
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kgorman, your rig looks the works. I do like the rims. Sounds like you found the absolute max.

For me wanting to run cup 1 rims the best combo is:

8x17 ET52 w/ 235/40 tires
9x17 ET55 265/40 in back

at the moment I run
205/40 and 255/40. The car still oversteers but corrects very nicely once of the gas. The most annoying is that every time I brake hard the APS certainly does its money worth. (any other suggestion to fix that would be appreciated)

First time I disabled APS I laid down a 15 m with of rubber. The tyres are getting better when warm but still not very good. They are Continental SuperContact 2.

I want to go wider and softer for road use manly. Would be happy if the tyres last 20000 km.

The over all setup would be manly for road use, normal ride hide with Bilstein shokies. I will add a tower brace and eventually bigger sway-bars, but thats down the road.

Best Regards

Stefan
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Old 02-28-2010, 06:46 PM
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Most people in Oz tracking 964's now run an 18" rim as it is cheaper here to get 18" track tyres now than 17". 18's usually run a 225 up front and a 265 rear with no issue. ET52 fr, 47 Rear. I run Cup 1's for both road and track and run 225/45/17 up front and 255/40/17 rear. This gives correct rolling diameter. Bear in mind that most aftermarket Cup 1 rims are HEAVY and this will effect your handling and go so try to get original but also bear in mind that original magnesium cup rims are usually very expensive. There are so many great aftermarket rims available for 964's like the cargraphic ones (and copies), BBS like KGormans (They look like BBS?) and also the CUP RS wheels in 18" look brilliant on a 964. Talk to Peter at Veloce wheels in the UK, he has some really nice, reasonable priced rims. Oz wheels also do some great light weight wheels and you can even get Rays and Enkei for 964 which are very light as well. You can also fit 95%of all late model narrow body rims. I run Cayman 17" rims (nice 5 spoke design) for my wet weather set up. I use a small spacer up front as the rear track is wider with these rims fitted so you need to increase the front track a bit to match as on the limit it understeers a bit more without the front spacers.

235's up front often rub on the inside of the guard on lock, especially if you are running big camber settings. And the rear issue is also the oil lines rubbing.
Tyre wise, have tried heaps of road and track tyres and for someone who likes a great fast road tyre and an occasional track day the Dunlop Direzza Sport Z1 tyres are fantastic. The tyre runs a track tyre carcass with stiffer sidewalls etc to give great steering response and a super sticky compound. I have previously run Falken RT 615's as road tyres which are a road biased semi slick and the Dunlops annihalate them for grip. They are WAY grippier than any road specific tyre but unlike the Falken's whish wear out in 8000kms, the Dunlops seem to wear quite well.

The Dunlops are also an excellent wet weather track tyre for those doing track days and have to sets of rims. ie one for dry, one for wet as the Dunlops have nice deep grooves to disperse the water in comparison to normal sprint tyres like the Dunlop DZ03-g or Brigestone Re55's.

Hope that helps.

Last edited by Jimjacqmx5; 02-28-2010 at 06:48 PM. Reason: spelling mistakes
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