Have a zed in for some serious welding and upgrade work and one of the reasons we had to recover it from the owners home was due to brake failure.

 

When it arrived we soon established the brake master cylinder was empty and the pedal went to the floor, so a quick top up and bleed at the abs unit just to give us some brakes to safely move the car about went ok except the front o/s calliper was jammed.

 

So look at the picture below to see how bad a caliper can get when its seized solid, a real mess and although rebuilding is possible this zed is in for some big brake upgrade so we just fitted a good used one and bleed it out again and now we have brakes albeit temporary for moving purposes till the new big calipers arrive.

 

From our experience the incident of caliper seizure is higher on the cast ones, the import alloy ones seem to not suffer the problem so much.

 

Jeff TT

 

they look like the ones ive taken off my breaker, cept they have more piston boots on. lol

 

i hear that those cast calipers are the upgrade from my ally ones?? i prefer the look of my ally ones. lol.

 

only because they don't suffer the warping you can get on overheated alloy ones. ill be rebuilding mine, the pistons still move JUST. by the way mike, once i got the front calipers off, it rolled well easy lol

The reason the alloy calipers were changed to steel is not because of warping but because of corrosion. Dissimilar metals such as aluminium and steel react when they are in contact with each other. One is ferrous and one is non ferrous and thus the reaction (corrosion). This corrosion obviously affected the caliper seals by wearing them prematurely and thus the early failure rates. Another side eaffect was the actual pistons siezing in the caliper. When both materials were changed to steel, this was aleviated but of course purists prefer the aluminium calipers because they are lighter. So really the difference is down to maintenance, the aluminium calipers require assembling / reconditioning differently to the steel ones to avoid / prevent the corrosion caused by these two metal reacting with each other. Sadly the approach as with most things these days is ' if it aint broke leave it alone' and of course buy the time it is broke, its normally too late.

I thought the reason they changed from alloy was the the caliper mounts to the hub flexed slightly under hard pedal pressure.The alloy ones were finned to aid cooling too.