Wheels
When it comes to wheels and tyres, most of the decisions are easy. Smaller is better, up to a point.
Either way, I would plan to run two sets of wheels and tyres. This is to allow testing of different tyres and to have a spare set for track days.
I'm currently planing to run 6" rims on the front of the car and 7" rims on the rear. This extra rear width is to handle the increased power and is better suited to the LSD planned.
Light Weight
Small and light-weight is good because this is unsprung mass and the suspension settings can then be optimised with other light-weight components. Obviously, this is a balancing act against the overall strength of the wheel. You do have to be careful when using race wheels on public roads, which tend to have potholes and other hazards. I've had no issues with the Compomotive CXR wheels in eight years of Fisher Fury R1 ownership but, I'm very careful to avoid holes and bumps.
Low Rotational Inertia
This is a function of the wheels being light in weight but it is also about the distribution of the weight across the radius of the wheel and is also a function of the overall radius. Smaller wheels spin faster for a given speed though.
The radius of the tyre (closely linked to radius of the wheel) is also a huge factor in this as it is a very significant part of the overall mass.
Basically, you want to minimise the weight and also keep any weight as close to the wheel centre as possible. This is very desirable as it means they can be stopped (i.e. braked) with much less effort. It also means that they can be turned with much less effort, i.e. the steering effort and feedback is much improved.
Availability
13" wheels are readily available and so are tyres. The speed rating of the tyres needs to be considered though.
Cost
Not a big factor but, 13" wheels are 'relatively cheap' and a very good set of four tyres can be bought for around £350.
| These Compomotive CXR wheels are my obvious choice and are what I have on my . They are light and provide excellent clearance for the brake calipers. They are also available in various widths and offsets. The 13×6" CX-R wheel weighs 4.6Kg. It is also available in 7" width, which weighs 4.8Kg. |
| If it was purely down to looks, then I'd use these Caterham R500 wheels but, brake clearance can be an issue and they don't really have the right offset. I like the simpler design which would be much easier to clean! |
| These lightweight 'Image Billet 93' race wheels weigh just 3.8Kg in 13×6" form. They are over £800 for a set of four though. Personally, I think this is money well spent. |
Tyres
| For the last seven years my first choice of tyre has been the Yokohama A048R and I find that using 185/60R13 size (which weigh 7.55Kg) on the front and rear of my Fury R1 gives perfect balance. These tyres only really work well in warm and dry conditions, with grip being poor when the road surface is cold or wet. This hasn't really been an issue though as I've adjusted my driving style to suit. Keeps you alert though! |
| The Avon ZZR seems to be very highly regarded and I'm am going to be trying these tyres on the Fisher Fury R1 next time I replace them. |
There are lighter tyres available in this size. It is possible to save at least 1Kg per wheel.
Style
13" wheels are not everyone's cup of tea. The fashion seems to be big wheels and low profile tyres, to the detriment of handling. Not on this car!
Wheel Nuts
The wheel nuts on my Fisher Fury R1 are M12 with a 1.5mm thread pitch. Fisher Sports Cars supplied closed steel wheel nuts that were not quite long enough to fit over the studs, so I hacked the end off with an angle grinder and tidied them up. They weigh 44.0g each. There are much lighter titanium and 7075 aluminium wheel nuts available that weigh as little as 20g each. Although not a major consideration for me, the MSA do not allow alloy wheel nuts in competition use.
Wheel nuts are unsprung mass, so it makes sense to spend a bit more money on light-weight, quality items.
| Many light-weight wheel nuts are also security wheel nuts, requiring a special tool to remove them. Whilst improved security is handy, this kind of defeats the main objective of them in my view, as I would have to carry this tool around with me in the car. |
| I also don't like coloured wheel nuts. They draw attention to something that really doesn't warrant it. My preferrence is for silver / aluminium finish, to match the wheels or black. Something like these forged 7075 aluminium Skunk 2 wheel nuts are what I have in mind. They weigh just 23.5g each and cost around £90 for a set of 16. |