Rusting brake discs - elise s1

[zebedee]

alright, I know the answer is 'use it more' but with a baby arriving in early december, I put my car in a garage (after careful washing and drying) and when I went to it about 3 weeks ago, the brakes (despite me leaving the handbrake off) had all bound on and it took a fair bit of force to free them off. The first time I hit the brake pedal the scraping noise was awful and the pedal was pulsing like a cobbled street was slipping down the back of it. It pulled up well enough after a couple of hard stops, but the front discs are very dished, I reckon you could cut your fingers on the lips that have formed if you pushed hard enough - so I reckon it needs new front discs. The back ones are 3 years old, dimpled discs, but they are really badly pitted with rust and even my repeated hard braking 10-15 times over a 4 mile route hasn't smoothed them off. Are they likely to need replacing or should they be 'skimmable', they haven't really worn much at all.

I've never known a car have such rusty brakes as the Elise!

[111Robin]

It's nothing to do with the "Elise", the brake discs are cast iron (wouldn't rust if they were MMCs) like most cars on the road. If you wash it and then put it into the garage for any length of time the only way to prevent this is to take it for a reasonable run after washing, with plenty use of the brakes to dry them out properly. Otherwise any moisture in the pads will without doubt start the corrosion process on the bare iron.

[zebedee]

granted, its just that it seems far worse on the elise than any other car, including my dad's cobra replica and merc SL, which also live in a garage abd get less use than the Elise! Not sure why the brakes bind on when they are off and completely cool when I put the car away either

[Yee haa!]

zebedee said:

I put my car in a garage (after careful washing and drying) and when I went to it about 3 weeks ago, the brakes (despite me leaving the handbrake off) had all bound on and it took a fair bit of force to free them off.

that's basically a nono with the elise. definitely best to take it for a short run even it's it just round the estate.

[zebedee]

what physics/chemical process is at work that makes the discs bind onto the pads when the brakes aren't on and all is cool when put away? I don't understand!

[111Robin]

It's just corrosion on the surface of the disc. The pads are still in contact with the disc when the brakes aren't applied (otherwise there would be excessive brake pedal travel before the pads made contact), there just isn't any force being applied via the pistons.Any dampness in the pads or in the air will cause this to happen. I managed to shear the friction material off the front pads on one of my previous cars after storing it in a damp garage during the winter. Pads were seized solid to the discs and broke off the backing plate when I let the clutch up. This will happen on any car, don't start another Lotus paranoia thread, there are enough already.