Can you measure your Hydraulic brake calliper width for me

Now, I am not going to tell you guys why I need to know this, as you will all take the piss...so lets just leave it at that...but


I want to find a rear disk brake calliper unit (preferably hydraulic and not cable) that is as thin as possible on the 'inside' the wheel side of the unit.

Weight is not an issue, but clearance between the wheel /spokes/ hub and the 'backside/outside ' of the calliper is.

See the bit of video of one that a mate modified ...with an angle grinder ...to make it fit his wheel.
This was done AFTER spacing the disk out from the hub

I have done similar to a Hope C2...but with a milling machine and belt sander...

The 'inside' calliper piston side needs to be as thin as possible.


Any one have suggestions for units thinner than this one in the video.

From the face of the very thin pad on it, to the back of the unit is about 17mm.


[youtube]http://www.youtube.com/watch?v=yj4A3M8on3I[/youtube]

Re:

Formula RX : 17.05mm measured from inward side of disc to the most inward point of the caliper.

Oooo...thats big too, same as my Hope and Shimano.

Hoping to find something as thin as the Old matura Gustav M's ..theyr were about 10mm.

Re:

You'll be looking for a single piston then, which means the brake will push against the rotor from the outward side only. 10mm will never be enough for a pad, piston (which needs more than 5mm of sleeve to travel properly to begin with) and housing.

Your best bet would be a custom job, but that would require proper machining. Look for a caliper that can be split in half, then have someone make a new inward side for it that only holds the pad.
Of course that means that you'll have half the slave cylinder displacement whilst keeping the entire master cylinder, so your single piston will suddenly move twice as far with the same lever travel.

Maybe turn the split dual caliper into two single ones and mount them both on the same disc? Or one on the front and one on the rear (like the Dual Combined Braking System on some motorcycles) ?

Ummm..now there is a good idea...I have some basic machining skils and the kit...and a Hope C2 system...nice thinking batman

distance measure from inside of brake disc surface to calliper outer (inboard side i.e. the calliper side that is nearest to spokes)

shimano XTR m975 16.2mm
shimano XT 4 pot 16.8 mm
shimano cheapies 15.5 mm
Formula R1 17.0 mm
Formula RX 17.3 mm
Avid CR 17.8 mm
Avid XX 18.8 mm
Magura Marta 18.2 mm


as ^^^ said, you will struggle to go less than 16 mm due to piston.

Note that Avid callipers are two piece; so one side could be replaced by solid plate providing the oil way drilling reaches the piston on the other side but the lever travel will halve as you will be moving one piston instead of two.

single sided should give narrowest calliper

if thre is clearance between the stays and disc, then youo could space the disc out - post mount callipers would be problem as the hole would need to be elongating possible breaking through the metal ; IS could use spacers to move the mount out.

can you run a 140 mm disc on the rear - this could run further out than a 160 mm disc.

Hell thanks for that lot, you have been busy.

I am looking at various options..probably the easiest is actually to use a bigger rotor..a 205, that way the caliper clears the hub completely.


a 9 inch

http://www.chainreactioncycles.com/haye ... -prod20028

205 will put more stress on the frame so may not be a good idea unless the frame is some crazy downhill rig - 180 on rear is more than plenty for majority of cases..... but will the larger rotor clear the chain and seat stays?

Not sure if it will clear or not, tha is something I had not considered. I'll measure up thanks for that.