Menu toggle

18's on an RS

nineonetoo

nineonetoo

New member
Probably a question that has been asked numerous times but is it mechanically safe to run 18's on an RS. Ive heard all sorts of here say mentioning that the suspension/Drive train isnt up to it but then on the flip side cup cars used to run 18's.

Cheers
 
Simple answer is yes should be fine on an RS. But beware that the extra diameter and susquent stiffness is likely to cause increased wear and tear on wheel bearings and the like. In theory later cup cars used RS chassis and running gear (but kept the c2 body style?) though with stiffer dampers and springs and numerous other detail changes. These as you say had 18's.
 
I run 18"s and find them no stiffer than the 17"s when fitted with the stiff walled Pilot Cup sports sticky things.

The only difference you'll notice is the steering. The unsprung weight has an effect. all that gyro stuff going on.....don't want to get too technical....it's a bit late for me.
 
Lee i'm just going by common sense really, what was once rubber is now alloy and so must be stiffer (in theory for the same rolling radius) As to if it can be felt don't know but i bet the chassis notices!
 
Can't imagine it does any terminal damage. I'm sure I'd notice a difference in ride. I'm sure it would be noticeable if the 17's had normal road rubber.

Think about how hard the cup cars were driven......smooth track yes but those kurb stones are hard.

993Rs ran road also with 18's....Don't know if bushes and stuff were different.
 
Porsche put out a notice stating that 18" wheels should not be used. However, it is a complicated problem and it's all about inertia. Heavier wheels put more strain on components. Larger wheels weighing the same as the smaller ones they replace also put more strain on components as the metal is further from the centre and therefore the inertia is more. So, if you want to ensure you don't over stress components, such as the hubs, you need lighter wheels.

However, the above is a simplification. The overall weight and distribution of that weight, including tyres, needs to be considered. Simplest thing is to either stay on 17's or accept you are taking a (small) risk.
 
Accept you're taking a small risk

Porsche also state you should take the car to them for servicing.

don't forget the 964 Turbo 3.6 had 18's std and I'm not sure there were issues there either.
 
Maybe of some relevence, but Porsche recomended early 993 not to use 18" over the standard 17"...later 993 which came wth standard 18" had a steering rack support brace fitted,,,,this can be retrofitted to ealier versions.....on the basis that 993RS has a pas 964 rack.....probably a connection and may help an 18" shod 964 ??
I doubt forces of inertia are too much of a problem,,,most of us run far stickier rubber on track than was available when these cars were delivered with road tyres in the early '90s....the reliability and durability of these cars is one of their most appealing characteristics.
 
The issue is the hub axle points not the rack etc - I recall talking to some Porsche folks as well as other who delve these things - and the 993 had different units and pick-up points. Seems the issue was highlighted in the cup races at the time where 18" and sticky tyres caused the wheel and stub to come off. Heavier wheels cause an issue too. But I have only heard of some cases where on normal use where there is an issue - lighter wheels clearly help although the stub-to-tyre distance cause the extra leverage force. I certainly would not put heavy 18" aftermarket wheels, sticky tyres etc..... Personally having talked to folks I decided not to go for 18" wheels and keep to 17" - at least if the wheel comes off my C4 I can be satisifed that the engineers got it wrong and not I!
 
I Had 18" Split rims on mine when I got it 6 years ago. I also had a set of Mags with Pirelli Slicks. The steering was heavy at low speed and my daughter pronounced it the worst car she had ever driven! I put Pilot sports on the Mags and sold the splits.
The car was transformed and the steering is superb and the car feels so much more lively.
Jeff
 
You must log in or register to reply here.

Posts made and opinions expressed are those of the individual forum members

Use of the Forum is subject to the Terms and Conditions

Disclaimer

The opinions expressed on this site are not necessarily those of the Club, who shall have no liability in respect of them or the accuracy of the content. The Club assumes no responsibility for any effects arising from errors or omissions.

Porsche Club Great Britain gives no warranties, guarantees or assurances and makes no representations or recommendations regarding any goods or services advertised on this site. It is the responsibility of visitors to satisfy themselves that goods and/or services supplied by any advertiser are bona fide and in no instance can the Porsche Club Great Britain be held responsible.

When responding to advertisements please ensure that you satisfy yourself of any applicable call charges on numbers not prefixed by usual "landline" STD Codes. Information can be obtained from the operator or the white pages. Before giving out ANY information regarding cars, or any other items for sale, please satisfy yourself that any potential purchaser is bona fide.

Directors of the Board of Porsche Club GB, Club Office Staff, Register Secretaries and Regional Organisers are often requested by Club members to provide information on matters connected with their cars and other matters referred to in the Club Rules. Such information, advice and assistance provided by such persons is given in good faith and is based on the personal experience and knowledge of the individual concerned.

Neither Porsche Club GB, nor any of the aforementioned, shall be under any liability in respect of any such information, advice or assistance given to members. Members are advised to consult qualified specialists for information, advice and assistance on matters connected with their cars at all times.

Porsche
Lockton
Pirelli
Officially approved
Oracle Finance
WEX Esso
Collecting Cars
Archant Dialogue
Back
Top