Hydraulic disc brake calipers

Status
Not open for further replies.
Page may contain affiliate links. Please see terms for details.
Had all sorts of damage, self inflicted or otherwise through the workshop but never broken off.....
 

Cubist

Still wavin'
Location
Ovver 'thill
Do you mean the lugs themselves failing, or the caliper itself? I've never head of it, and can't imagine what sort of load the lugs or the caliper body would have to be under for either to fail.
Why do you ask?
 
OP
OP
Night Train

Night Train

Maker of Things
Thank you.

Why do you ask?
I'm designing something non standard and checking the one component I am not designing myself.

The standard configuration is that the caliper is behind the fork or chainstay and so in braking the bolts and mounting lugs are compressed against the fork.
However, the ISO mounting is also at an angle that is neither tangential nor radial to the disc so the mount lugs are part in compression and part in shear.
If the caliper was mounted ahead of the fork then the lugs would be part in tension and part shear.

I am trying to figure out if the caliper would be able to sustain abusively heavy braking loads in this configuration without failure of the bolts or the lugs.
 

andrew_s

Legendary Member
Location
Gloucester
The Cotic Roadrat has the disc mount on the front of the right-hand fork blade, and has had for some years.
This has the advantage that it's out of the way of mudguard stays, and that lawyer lips may be omitted without the fear of the wheel coming out of the dropouts under braking torque
 
OP
OP
Night Train

Night Train

Maker of Things
The Cotic Roadrat has the disc mount on the front of the right-hand fork blade, and has had for some years.
This has the advantage that it's out of the way of mudguard stays, and that lawyer lips may be omitted without the fear of the wheel coming out of the dropouts under braking torque
That sounds positive then.

I wonder why more manufacturers don't place them that way round in the first place?
 

battered

Guru
Go for it, similar size fastenings secure car brakes, both in supported shear and not, and they are bulletproof in use. If you want confirmation, look up the shear strength of M6 steel fastenings (it's massive) and then calculate how quickly this could stop say a 15 stone rider and 30lb bike from say 40 mph. This is going to be deep into crash territory.
 
OP
OP
Night Train

Night Train

Maker of Things
Go for it, similar size fastenings secure car brakes, both in supported shear and not, and they are bulletproof in use. If you want confirmation, look up the shear strength of M6 steel fastenings (it's massive) and then calculate how quickly this could stop say a 15 stone rider and 30lb bike from say 40 mph. This is going to be deep into crash territory.
I would have said that car brakes were around M10-M12 fine thread high tensile bolts in shear.
I'm not sure of the grade of M6 bolts used on bikes but that could be upgraded to graded bolts.
My main concern was if the casting lugs were up to the job.

Looks like it is a good probable.
However, it is an ISO standard and so 'the strongest' calipers could be specified and the 'weakest' discouraged.

Thank you.
 
OP
OP
Night Train

Night Train

Maker of Things
As most are aimed at off road use and you don't want the caliper leading as it makes it vulnerable to damage.
I can see your point with off road use but they wouldn't be vulnerable on a hybrid, urban, or touring bike, or tandem, where the tyre/road friction could be higher and possibly with higher speed and loading requiring higher breaking force.
 
OP
OP
Night Train

Night Train

Maker of Things
I'm not sure that matters, better to think over all possibilities in the design stage then to supply something that causes a potential failure later on.
Anyway, if it is still vulnerable then maybe the caliper isn't as well able to cope with use in that direction then in the conventional direction.

However, if there have been no instances of calipers being broken then it may not be an area I need to be concerned about in the design. The caliper will/can be located away/protected from any road hazards or impacts.
 
Status
Not open for further replies.
Top Bottom