Why so many wheels?

[65 mat]

Why did Porsche use so many different types of wheels on the RS range?

Early Cup cars: steel cup 1's (8''x17'' fronts/9.5''x17'' rear)
RS Lightweights: Magnesium cup 1's (7.5'' fronts/9''x17'' rear)
N-GT Clubsports: '' '' '' '' '' '' '' ''
Later Cup cars
(Supercup) :Speedline split rims (8''x18 front/10''x18 rear)
C4 Lightweight :Magnesium design 90's (8''x16 front/9.5'' rear)
3.8 RS :Speedline split rims once again

Please correct me if some of these sizes are incorrect,I do not class myself as an expert. You get where I'm coming from though don't you? Why not just use the same wheels on them all (especially on the narrow bodied cars)?[8|] Are some better than others?[8|]

 

[Melv]

Simple -lower weight of mags and 18" go around corners quicker and 18" Pirelli slicks, from '92 onwards, more readily available as also the control tyre in the DTM series. So in order to homologate the wheel for the Carrea Cup, it must be available on road car.....

Split rims better for racing, since a damaged part, instead of whole wheel, can be replaced -so back to homologation issues again......

Next![]

 

[65 mat]

Thanks for that Melv... now I can finally sleep at night![]

 

[mike2]

ORIGINAL: Melv

Simple -lower weight of mags and 18" go around corners quicker and 18" Pirelli slicks, from '92 onwards, more readily available as also the control tyre in the DTM series. So in order to homologate the wheel for the Carrea Cup, it must be available on road car.....

Split rims better for racing, since a damaged part, instead of whole wheel, can be replaced -so back to homologation issues again......

Next![]

I think there is no need for homologation for the Carrera Cup, because it's a one-make cup... e.g. today Cups have a sequential transmission and no official street car has such a gearbox...

I assume, they took the 8" and 9,5" (1990/91) without magnesium, because you have to check magnesium wheels regularly because of the breaking issue, if you use them on the track... On the street cars they put smaller wheels to have a better straigth-running performance...
The Cups in 1992 and 1993 were 1 sec. faster in Hockenheim with 18" because of the lower tyres on the wheels.... the wheels had 8" and 9,5"(!)...

 

[carreraboy]

The 964RS C4 was on D90's?

 

[RSGulp]

ORIGINAL: carreraboy

The 964RS C4 was on D90's?

http://rpmsportscars.com/door25.htm

 

[carreraboy]

Nice bit of kit, Brian Burrows had one for sale a few years back $154000 seems reasonable in comparison to money still being achieved for standard 964RS ....

 

[65 mat]

ORIGINAL: carreraboy

The 964RS C4 was on D90's?

Shocking isn't it!...but apparently they were wider and were made from magnesium. They were Jurgen Barths idea.[8|] A limited batch was made especially for the 22(?) cars which were produced.

 

[964RS]

I read that the mag D90s weigh less than the mag Cup 1s. [8|]

 

[Tony]

Probably because the dia. is less. Generally speaking bigger the wheel the more it weighs - materials being constant.
If you want something really different they did mag. telephone dial wheels for the 1st cup car series (944 turbos).

Tony

 

[ChrisW]

ORIGINAL: 964RS

I read that the mag D90s weigh less than the mag Cup 1s. [8|]

What are D90's ?

 

[964RS]

 

[RSGulp]

ORIGINAL: ChrisW

ORIGINAL: 964RS

I read that the mag D90s weigh less than the mag Cup 1s. [8|]

What are D90's ?

Short for 'Design 90' wheels - I assume because they were designed in 1990?

 

[ChrisW]

Thankyou --- I guess I should have looked at Tom's C4 Lightweight ... not pretty wheels to my eye ...

 

[harry]

ORIGINAL: carreraboy

The 964RS C4 was on D90's?

Shame on you Des, I expected you to know this [] You're slipping...

Harry

 

[65 mat]

Porsche says that 18'' rims must not be retro fitted to cars which were originally fitted with 17''s. WHY? They did this with some of the early cup cars (ones with tiny wing mirrors),and many guys on here have gone for 18''s. [8|]

 

[Tony]

It was the later cup cars that had 18's. If you seach the archive I thing this has come up a number of times before. I think the simple answer is because for road use, they wern't designed with 18" wheels and didn't have type approval.
In reality bigger wheels are generally heavier & that with better grip puts more strain on components - wheel bearings in particular - but also steering , for the 993RS with 18's as std there is an additional brace along the rack - don't know if this was also fitted to the '92 cup cars. I believe the main reason the cup cars used 18's was the availability of slicks, in particular the deal Dunlop came up with.

Tony

 

[65 mat]

Thanks for the info on that one Tony...Talking of a tyre deal Tony,one of the reasons I prefer 17'' wheels is that the tyres are so much bloody cheaper![]

 

[Melv]

And some US cars had suspension breakages running 18"..........

 

[Hacki]

Tony,

when Porsche decided to go for 18" on the Cup cars, they simply wanted faster cars. Those days there was direct comparison with the DTM race cars, often the DTM and Cup cars were run the same race day (Not in the same race though). Lap times of the Cup cars were not that much slower and Porsche didn´t want a bigger gap.

I also remember tyre problems with the 18". The cars were significantly faster, had more grip and in case the set up was a bit to "special" one could ruin the tyres before the race was over. So there was for sure additional strain on the suspension and the weakest part of the system had to break.

I don´t remember a Dunlop deal, I think it was always either Pirelli or Michelin and I think the first year on 18" it was Pirelli. The original Speedline 18" rim was very light (if my memory is correct), so the weight was probably not the problem.

For the spectators the bigger wheels gave the car a different look, one could see the difference (compared to the previous year). It was one of the first steps on a long ladder. Those days a Cup car was way closer to the standard car than a 997 Cup car is today.

Hope I got it all right and I can still trust my petrol influenced memory capacity.

Rgds

Hacki