Not strictly Locost, but still automotive...

I'm attempting to fit slightly bigger brakes to my mk3 XR3. I've got a pair of Mondeo calipers which look like they will fit, as long as I use Escort Turbo mk4 discs. However, the Mondeo calipers have M12 bolts attaching them to the hubs and the Escort has M10.

Obvious thing to do is to drill out the holes in the hub to 12mm. There is plenty of 'meat' on the hub, so I can't see any problem in terms of strength once this has been done.

However, what I would like your opinion on is how to go about it. As I'm only going up by 2mm, will it be ok to use a regular drill and do it in situ - ie with the hubs still on the car? Will the drill follow the existing hole pretty accurately?

Or, should I be taking them off and using a pillar drill? In which case, it's going to be pretty difficult to hold them absolutely horizonally, due to the odd shape of the part.

Your opinions please!

Cheers, Chris

Could you use M12OD M10ID spacers and retain the M10 thread/bolt ?

alternative would be 1mm sleeve on the existing parts and re-use a 10mm bolt. is that not an option?

I would think that this is a case of "grinding cranckshafts" so should be done on correctly.

I prefer to use a pillar drill whenever possible.

Is it possible to bolt it down using a 10mm bolt or studding, with nuts above and below.
Drill to 12 and then swap to a 12 bolt or stud through the hole you just drilled to drill the next one.

When drilling small amounts out with pistol drill the drill bit tends to grab.

HTH

Paul G

it's not possible to use threaded rod or anything like that, and there's no spacer required, so that's out too.

The only other way would be something that goes inside the thread on the caliper that reduces it to 10mm.

My concern with the pillar drill is that the back of the hub has steering arm and ball joint mounting hanging off it, so it would be pretty hard to clamp it down to a drill base.

Chris

This guy

Has just done the same mod to a set of sierra uprights.

Similar, but not exactly the same. I got around the offset problem by using different discs.

When I mocked it up on the car I measured 12mm gap between the caliper and the mount, and after some cross-referencing, found that Escort turbo (series 2) and Sierra 2.0 w/ABS has the same diameter and thickness disc, but with 11mm more offset, which seems perfect.

Chris

since the clearance between the caliper and the disc is not exactly precisely machine to fit, i see no reason why it should need to be drilled so accurately.

i assume the hole in the upright is a clearance hole and the bolt clamps the bracket to the lugs on the upright.

you're not altering the mounting faces, so nothing's going to be driven out of square. if the hole is slightly wayard, it will only alter the radial position and there's got to be more than a mill of wiggle room.

i know it's brakes, but stop panicking!
tom

Thanks. Think I've just been convinced to just do it in situ. My worry was that this is (currently) the daily driver, so if it screws up I'm stuffed. Hubs for a 1982 XR3 are quite hard to find!

Cheers, Chris

quote:

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Originally posted by indykid
since the clearance between the caliper and the disc is not exactly precisely machine to fit, i see no reason why it should need to be drilled so accurately.

i assume the hole in the upright is a clearance hole and the bolt clamps the bracket to the lugs on the upright.

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