In the not too distant future I will be changing from Sierra 4x4 calipers to a lighter 4 pot setup. The first choice, as is for many, is the wilwoods due to the price but I have heard stories from different sources of the calipers flexing/warping under load. From a reputable source, I was told that one of their calipers flexed 10mm to then score the inside of the rim of the wheel!

Are these installation errors or do the wilwood really not perform great under intense loading?

What is the next cheapest option to wilwood that will fit under 13" wheels?

There is no way the caliper itself deflected/deformed by 10mm.

Sounds like the upright mounts or conversion brackets weren't upto the job.

Also remember that if your buying wilwood calipers designed for a sierra set up, they will be stopping a car roughly half the weight of the one they are designed for, so wont really be under intense loads.

calipers are way to solid to flex at all sounds like total bulls%it to me. If you think about it to flex 10mm then the whole disk would have to have moved 10mm too, yeah and like that's going to happen. Either someone had awful wheel bearings or didn't mount the caliper correctly

Never had a problem with mine. The rears are on drum conversion brackets and the handbrake levers ar every close to the 13" rims. Never touched as far as I know and no marks on the rim.
Wilwoods seem to be the caliper of choice in the RGB series. I've heard of othewr makes both leaking and binding.

All callipers flex, alloy multipot callipers will generally flex more but it should be within acceptable limits the main cause of excess pedal travel is the calliper not being properly aligned to the plane of the disc friction surface. Even a small (less than 0.5mm) error in the brackets can result in a very spongey brake pedal.

It pays dividends to spend some time doing old fashioned checking the pad to disc gap with feeler gauges and doing old fashioned hand fitting to get the calliper true to the disc surface in all 3 axis.