I've been looking for some Sierra rear calipers for some time and now have the chance to get a pair locally for a good price.

They came off a Cosworth which will presumably have had vented disks.

Are these any good or do I need to source some for solid disks?

If you have solid discs you need the calipers to go with them.

Stating the obvious - The calipers for vented discs have a wider gap.

Cheers

Mark

I have a set of both types, vented and unvented with disks for sale.

vented discs work the same as solid as far as i can work out ,vented just help you stop brake fade .
(as far as i can work out drilled and groved and better pads are better for stoping power but on the rear you will need a PROPORTIONING VALVE as the rear will lock up with discs thats why i have kept my 9"drum brakes on my rear and fitted a PROPORTIONING VALVE )
see this ebay add for more info

http://cgi.ebay.co.uk/BRAKE-BIAS-PROPORTIONING-VALVE-FIESTA-ZETEC-PUMA-FOCUS_W0QQitemZ150052095247QQihZ005QQcategoryZ21654QQrdZ1QQssPageNameZWD1VQQcmd ZViewItem

I have found - at great expense that sierras used at least the following:

253x10mm disks (std sierra)
273x10mm disks (2wd cosworth) i think
273x20mm vented discs (cosworth)

The calipers on the 253x10 and 273x10 are the same. It's the caliper carrier that the hub attaches to that has different spacings.

The 273x20 are vented and use calipers with wider jaws.

Hope this helps don't do what I did, and buy all derivatives until you find what works!!