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Just fitted 18" rims

OllieW

OllieW

New member
Decided the suspension replacement could wait until the back end of the year and have fitted a set of 18" Split Rim Cup replica's from Design 911, shod with Toyo R888's. Other reason for a new set of rims is that the mags can now be retired to the garage on only get the occasional use.

Took it out for a blast last night and was impressed with the ride quality and feel on the bigger rims. Proof in the pudding will be Spa/Ring in May.

Next question is tyre pressures, I know Simon started a thread about it but it was a little inconclusive...

Anyone got any experience of what pressures I should run with 18's?
 
Nice one Ollie, however it's the law that you must post pictures.

Tyre pressure wise I run the same as with the 17's .....whatever that is[:)]
 
Ollie

Trust me. It wasn't inconclusive[;)]

On a 964RS, running negative 1.8 degrees of camber, the best lap times were on 30 psi all round. This proved to give even heat across the tyre. Vic also seemed to get good results at 32 psi. However, it seems that cars running more camber and that are significantly heavier have had problems.

I would start at 32 -34 psi and adjust to taste. Keep an eye for undue wear or overheating.
 
Tyre pressure? Try and find out!

Basically the same as on 17" rims. A friend of mine and myself, both running 964 Cup cars, one on 17", the other on 18", came to this conclusion:

Diameter makes no difference in tyre pressure, for track use start with 1.9 bar front and 1.8 or 1.9 bar rear on cold tyres. Check after a few laps. We figured out that 2.4 bar with hot tyres (front and rear) is great. If pressure rises higher than 2.4 bar be careful! The grip vanishes as the rubber melts and by ignoring that you will experience an uncontrollable car. (Know what I´m talking about, lots of smoke and a nice 360 [:(])
Camber, toe in, ARB position, surface and driving style have influence, so just check any time on the track after some laps. 2.4 with hot tyres is the goal.

For daily use I recommend a tendency for low pressure, e. g. 2.1 bar, which is less than Porsche recommends. That´s a matter of personal taste.

Sorry, don´t know what that is in PSI.

Have fun and post pics!

Hacki
 
I have to agree with Hacki about running too high pressures. The car becomes very loose as it runs on the overheating centre of the tyre. It is very disconcerting
 
I used to run 34/36 on 'road tyres', 32/32 on PO's, 30/31 on slix -and can concurr -as little as one psi over on the rears and it tends to go a little squirrelly!!

BTW, running on nitrogen at the mo, start day at 24/26psi, let it go to about 32 then bleed off a little to 30/31 and leave it at that....
 
I've just had a call from Toyo regarding this as I emailed them last week and they have come back to me saying that I should be aiming for a pressure of 33-34 HOT in the fronts and 38-40 HOT in the rears. Apparently they have been working with a lot of GT3 boys to get this right...

Roll on Spa [:D]

Oh and I promise to get some pics taken soon...
 
ORIGINAL: OllieW

I've just had a call from Toyo regarding this as I emailed them last week and they have come back to me saying that I should be aiming for a pressure of 33-34 HOT in the fronts and 38-40 HOT in the rears. Apparently they have been working with a lot of GT3 boys to get this right...
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Total BS! Maybe somebody should tell them about the difference between the weight of the cars, the amount of camber being run and the power. 34 front and 38 rear made my car as loose as anything, to hte point that I came in early from a qualifying session. I was proved correct as my laptimes slowed and there was overheating the centre of the tyres etc. Totally wrong! I made the same mistake by telling the GT3 boys to run lower pressures - I didn't take into account the differences between the models.

I don't think it is a coincidence that Vic Cohen also found the lower pressures to work on his 993 GT2.

The only sure way of getting this right is to test the tyre temps across the tread. I did this, Vic did it. The GT3 boys did it and we all ended up with pressures that suited the car.
 
ORIGINAL: Melv

BTW, running on nitrogen at the mo, start day at 24/26psi, let it go to about 32 then bleed off a little to 30/31 and leave it at that....
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We are running the cars on "dry air" from diving compressors. Not quite as good as nitrogen but a hell of a lot cheaper.
 
So is nitrogen better than normal air then??

Garage round the corner from me uses nitrogen, charges £1 per tyre to inflate. Is it worth getting some pumped into mine before Spa/Ring?

Rob
 
Rob

It is only worth it if you have a supply for topping up etc. Using normal air just ruins the nitrogen. There is a lot of hype about nitrogen and done properly, you get less heat gain pressure rise and it doesn't leak away in the same way air does.

You need to ensure the rim and inside of the tyre are bone dry before you fill and I also believe that thetop motorsport teams are careful about where they get their gas. The cost isn't in the initial fill but in the cost of taking nitrogen to the circuit with you!

Hope that helps.
 
Pics of wheels fitted as promised...

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Very Nice...but the photography needs some practice mate[;)]

Hope you've locked the car up in the garage...wouldn't want to get it dirty with new wheels now would we[;)]

We all getting together to discuss Spa?[:D]
 
ORIGINAL: jason

Very Nice...but the photography needs some practice mate[;)]

Hope you've locked the car up in the garage...wouldn't want to get it dirty with new wheels now would we[;)]

We all getting together to discuss Spa?[:D]
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I didn't think the photography was too bad considering I am colour blind, i think my black car looks ace [:D]

Just so I don't get labeled as Lee 2, i promise to use it once or twice this year and might even get it wet if it rains. As for Spa trip I know Steve is trying to get an evening sorted to get us all together to chat about the plans.

I'll keep you posted.

Cheers

Ollie
 
ORIGINAL: OllieW

ORIGINAL: jason

Very Nice...but the photography needs some practice mate[;)]

Hope you've locked the car up in the garage...wouldn't want to get it dirty with new wheels now would we[;)]

We all getting together to discuss Spa?[:D]
Click to expand...

I didn't think the photography was too bad considering I am colour blind, i think my black car looks ace [:D]

Just so I don't get labeled as Lee 2, i promise to use it once or twice this year and might even get it wet if it rains. As for Spa trip I know Steve is trying to get an evening sorted to get us all together to chat about the plans.

I'll keep you posted.

Cheers

Ollie
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Cool.

Hope you are gonna murder my 3 at Spa in your RS...wouldn't want me to stop living the dream[;)]
 

ORIGINAL: carreraboy



Read your post, how much wheels and tyres?
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From memory they were in the region of £1650 inc vat, delivery and the tyres fitted and balanced.

A fair bit cheaper than a new set of mags...
 
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