Spacing brake caliper?

[wagonist]

So I've found a bolt on rear disc conversion for my Excel using Mitsubishi parts.

The problem is the hub to caliper bracket offset is different & I need to move the caliper outwards by 6mm.

I was thinking of just using 6mm plate, but the straight line between the mounting holes has the brake piston in the way.

Can I get away with just using 2 6mm thick washers, or should I go to the effort of making up a shaped plate that then clears the piston?

The car isn't registered, so it doesn't need to pass engineering, but it's still got to be good enough to withstand race use including handbrake turns for motorkhanas.

[thechuckster]

can you make the spacer a dog-bone shape so the pistons clears but you still have the holes joined up?

[wagonist]

I can, just a crap load more work in the extremely limited time I've got to do this conversion.

The end of next week is the first aim, but definitely has to be the end of the following week to (apart from fitment of parts):
pick up replacement rotors & front pads
make 2x spacers for rear calipers
get booster pin adjusted/shortened to suit replacement master cylinder
get 2x braided brake lines made for rear calipers
get wheel alignment done (because I've changed steering knuckles & replaced tie rod ends)

[wagonist]

And even if I do the dog bone arrangement, the only places they'll be touching anything are where the bolts go through.

[oldcorollas]

how thick is the plate the caliper bolts to?

will that 6mm be an extra 5% moment arm, or 200%?
ie, will it help the caliper to rotate and bind the disc?

can you get the outer face of the hub machined down 6mm?

[wagonist]

The plate is 10mm thick where it bolts to the suspension, thins down to 8mm, and then back to 10mm at the caliper end (offset 3mm from the other end).

Can't machine down the hub face because I'm already rubbing tyre on springs under high cornering loads at Wakefield.

There's about a 2.5mm clearance between the inside of the fixed part of the caliper & the machined face of the rotor. Do you reckon it would twist that much?

I'll see what metal I can get hold of. I only need to scollop one side (for now anyway).

Should I try to keep the dog bone shape the same width for the full length (which might cause some clearance issues with the hub)?

[thechuckster]

I'd suggest a mockup in cardboard, then roughly sculpt the flat 6mm steel plate with an angle grinder using the cardboard mockup.

Only thoughts are that maximum width where possible and must be wider than the mounting faces (the actual surface that touches) on the hub & caliper.

Give it a quick spray of matt black then fit spacer, have quick celebratory beer, then onto the 295 other things that have to be done by the end of the week.


fwiw: the nissan-caliper-onto-Ma61-front-strut spacer isn't very wide and only 8mm thick. Does suggest that most adaptor brackets are wildly over-engineered.

[banana_socks]

If its just a spacer, then I don't see how a dog bone shape would be any better than using washers. The only concern is increasing the moment arm as mentioned, but that would be the same for either design.

[wagonist]

This is the part I'm in agreeance with.
I'm not trying to move the caliper further away from the axle line, just more offset.

However, from a quick CAD drawing I've done up (which I can make a template from), the farthest point of the dogbone is 50mm, so I ended up getting some 6mm thick x 50mm wide flat plate today for nix, just a matter of drilling the 2 holes & mounting the bracket without the floating part of the caliper to confirm the width is correct.
And then I'll try to shape it.