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Discussion Starter · #1 ·
It is very easy to warp your brakes if you do not bring them up to temperature carefully.


The standard (or any solid cast iron rotors) do not have good heat conduction. If you suddenly brake hard on cold brakes then the outer part of the disk will get a hotter quicker than the center part, hub and wheel. This will cause them to 'ripple' due to the outer part expanding more than the inner part. This may go away if you let them cool, but if you persist then permanant warping may occur as the peaks will get worn slightly compared to the valleys - then when the brakes cool and 'unripple' the 'peaks' will now be permanant valleys. Interestingly this is a typical road use scenario.

On the other hand if you brake gently at first, slowly increasing, this will give time for the inner rotor, hub and wheel to also heat up. Because the rate of heat conduction to the air (which cools the brakes) is proportional to the temperature difference the hotter the brakes the quicker they loose heat (this is why f1 brakes run so hot). Thus the whole assembly will tend to stabilise at a hot but consistant temperature even with continued hard braking. Thus the expansion of the whole assemmbly will be more consistant and permanent warping is less likely.

To sum up if you slowly bring the brakes up to temperature on the track by progressively braking harder then standard brakes will be less likely to warp (other problems such as pad fade or fluid boil not withstanding) than if you suddenly repeatedly brake hard on the road or go hard out immediatly on the track.

2 piece brakes with aluminum bells, etc are an alternative solution as aluminum expands more than cast iron and also dissipates heat quicker. Use of aluminum bells also reduces rotor mass - giving improved acceleration, faster braking and better handling due to lower unsprung weight, this is an important reason why they are used in racing and are also useful on a road car.

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