Wheel Changes

[old captain slow]

My car has the 16" 5 spoke wheels. Can you advise me whether I can do a straight swap for 13" for use on track days etc. If so what would you recommend for an all round tyre. The car has flared wings, so mudguard size should not be an issue.

[Andy Checkley]

I maybe wrong, but I think you may have an issue with your back axle ratio. I think that the 13" wheeled cars use a 3.62 final drive but 15"/16" use a 3.92 final drive, as the overall tyre/wheel diameter is different.

 

If this is correct, acceleration should be good, but top end will be reduced. You may have to do some sums to work out the difference.

 

Someone else out there maybe able to shed more light on this.

 

Regards, Andy

[Graham Perry]

Another thing to beware of is the size of the front brakes. I know of a couple of people who have fitted 13" wheels where the brakes touched the spokes of the wheel and had to fit a small spacer to prevent this happening.(Mine miss the spokes by 2mm so they can run close) If you get a wheel with the correct offset for your own car then this should not be a problem.

[Barry]

I think that the 3.62 final drive was/is fitted to de dion cars with a 4 speed gearbox, and the 3.92 to those with a 5 speed 'box.

 

The issue of brakes touching wheels is an interesting one. IIRC the Caterham/AP big brakes have larger calipers and do indeed foul on some 13" wheels, notably 4 spoke Revolutions. However, to my knowledge, the standard brake calipers don't foul any. It's well to remember that it's not strictly speaking the offset that's the problem, but the design of the wheel, in other words it can depend on:

1) the inner radius of the spokes (whether they curve out enough to give clearance before meeting the rim.

2) the distance from the central, raised, part of the rim to the centre of the wheel and whether there's enough room between that and the wheel hub.

[Alex Wong1697456877]

When I went from 13" to 16" on my old crossflow car, the wheels fouled the wing stays for the flared wings. I had Bilstein shocks with about 4 circlip positions for height and this had to be raised / lowered at the front for 16" / 13" wheels.

 

Other than that, I just swapped the wheels. Gordan Cardew started with 16" wheels on his '96 de-dion supersport and just changed them for 13" without any other changes. He was very pleased with the smaller wheels.

 

Not all minilight type wheels fit over the AP calipers. Revo 4 spokes definitely don't. My minilight style wheels came from Caterham and they fitted fine.

 

Regards,

 

 

 

 

 

Alex Wong

alex.wong@lotus7club.co.uk

http://www.alexwong.net

Home : 44-(0)121-440 6972

Fax : 44-(0)121-440 4601

 

 

 

Edited by - Alex Wong on 4 Apr 2000 11:10:57

[old captain slow]

Thanks for the advice, guys. I wasn't aware that the diff might have different ratios depending on wheel size. I'll check with Caterham. I've got the 6 speed box by the way. Don't know if that makes any difference.

[old captain slow]

Oh! Forgot. What about the tyre choice question. Any favorites? Avons seem to be current flavour of the month. Mind you now that my son is buying a 7 with just less than enough money, I think the new wheels may have to wait.

[Alex Wong1697456877]

It depends on what you want to use the car for. It's all a compromise one way or the other - from standard road tyres that last forever to ultra soft compund ACB10's. Normal ACB10's last about 3000 miles with road use. The softer ones would probably go much quicker.

 

If the car is going to be used on the road mainly, and also in the wet, and is going to be used only for the occasional track day, I'd go for 021R's (Yokohama).

 

ACB10's are great but they're not the best thing for a wet day, plus they're very stiff sidewalled, meaning you'll need to dial out some of the camber and ideally replace the rear de-dion ears to get the most out of them. They're also expensive and don't last very long. I don't think they're particularly suited to a predominantly road car.

 

The difficulty comes if you want to compete in the car. If you are, you may want to stick to MSA 1A tyres to stay in the road going classes. The best 1A 13" tyre is either the A520yoko or one of the Falken tyres (according to BMTR). I use A520's on the road and they're ok. Good value and last forever (10,000 miles and only half worn) but they're not nearly as good as 021R's and to be honest, they take alot of the fun out of driving the car.

 

032R's are another option and they are very sticky in the dry. They're not as progressive as 021's on the limit though and in the wet, they let go quite suddenly. I found my car less fun to drive on the road with these than with 021's. Too sticky in the dry and too scary in the wet IMHO.

 

 

 

 

Alex Wong

alex.wong@lotus7club.co.uk

http://www.alexwong.net

Home : 44-(0)121-440 6972

Fax : 44-(0)121-440 4601

 

Edited by - Alex Wong on 5 Apr 2000 22:03:08