Upgrading Discs
Discussion
Preparing for the abuse as I'm sure this has been asked loads of times before - but the search function is broken.
I've buckled a disc (f
k knows how!) to the point it almost seizes when the buckle goes through the caliper so almost unrideable.
I figured that seeing as I'm gonna have to spend money on a new disc, I may as well spend a bit more and replace both front and rear and get some bigger ones.
What else do you actually need to upgrade discs though, as I'm guessing larger discs will rub on the outside edge of the caliper? And if anyone can point me in the direction of decent bits I'll need it would be appreciated.
I've buckled a disc (f
k knows how!) to the point it almost seizes when the buckle goes through the caliper so almost unrideable. I figured that seeing as I'm gonna have to spend money on a new disc, I may as well spend a bit more and replace both front and rear and get some bigger ones.
What else do you actually need to upgrade discs though, as I'm guessing larger discs will rub on the outside edge of the caliper? And if anyone can point me in the direction of decent bits I'll need it would be appreciated.
Few answers from me but some considerations:
Larger diameter affords greater (negative, as you're braking) torque but higher circumferential speeds. Essentially the energy you need to convert is the same regardless. A larger disc might cool more quickly of be able to soak more heat thus re-presenting a cooler face to the pads, and therefore reduce fade.
I would have thought that greater surface area would afford greater braking effort. Bike discs look (to me) very counter-intuitive with their "more holes than metal" appearances.
For an increase in diameter you'll need a bracket to offset your calipers. I believe these are fairly standard.
Larger diameter affords greater (negative, as you're braking) torque but higher circumferential speeds. Essentially the energy you need to convert is the same regardless. A larger disc might cool more quickly of be able to soak more heat thus re-presenting a cooler face to the pads, and therefore reduce fade.
I would have thought that greater surface area would afford greater braking effort. Bike discs look (to me) very counter-intuitive with their "more holes than metal" appearances.
For an increase in diameter you'll need a bracket to offset your calipers. I believe these are fairly standard.
HowMuchLonger said:
You will need different adaptors as well.
Something like these?http://www.wiggle.co.uk/a2z-adapter-pm-to-pm-160mm...
And what's the difference between PM and IS?
james239 said:
Something like these?
http://www.wiggle.co.uk/a2z-adapter-pm-to-pm-160mm...
And what's the difference between PM and IS?
Pm = post mounthttp://www.wiggle.co.uk/a2z-adapter-pm-to-pm-160mm...
And what's the difference between PM and IS?
The holes on the fork are perpendicular to the axle. Normally manitou if I remember correctly
IS = International standard
The holes are parallel to the axle.
Ironballs said:
Can your forks take a bigger disc? ie are they strong enough as they may not be rated to take the additional torsional force.
Do bigger discs actually give stronger braking force though?I understand where that thinking comes from, but the pads will be the same so the contact patch remains the same. I know the bigger discs are potentially better at cooling so less fade etc and will keep up their braking force for longer (but sustained braking at the same force shouldn't be bad for the forks, their designed to take the force of the standard discs anyway), but actual braking force surely doesn't actually increase unless you increase the contact patch?
It's not the contact patch that is important, it's the radius of the disc. If you have a larger rotor then you have a higher speed of rotation and a greater lever effect on the wheel (and fork), this is why a larger rotor will give more power.
A more powerful brake, whether larger rotor or more pistons, exerts more force on what it is attached to, otherwise it wouldn't be a more powerful brake.
My warranty will be invalidated on my Fox 100mm forks if I go beyond a 165mm rotor because they're lightweight forks and not designed to take the higher torque of a larger disc
A more powerful brake, whether larger rotor or more pistons, exerts more force on what it is attached to, otherwise it wouldn't be a more powerful brake.
My warranty will be invalidated on my Fox 100mm forks if I go beyond a 165mm rotor because they're lightweight forks and not designed to take the higher torque of a larger disc
Rotor size does increase braking force. Surface area of the disc makes no difference to braking force, more holes equal more surface area for cooling the disc, thats all they do.
The pads will produce a force stopping the rotor. Torque = force * radius so the bigger the rotor the bigger the braking force.
The pads will produce a force stopping the rotor. Torque = force * radius so the bigger the rotor the bigger the braking force.
Floor Tom said:
Rotor size does increase braking force. Surface area of the disc makes no difference to braking force, more holes equal more surface area for cooling the disc, thats all they do.
The pads will produce a force stopping the rotor. Torque = force * radius so the bigger the rotor the bigger the braking force.
Force isn't what you're measuring - you want to dissipate energy and that fixed regardless of rotor/disc size.The pads will produce a force stopping the rotor. Torque = force * radius so the bigger the rotor the bigger the braking force.
Mars said:
Floor Tom said:
Rotor size does increase braking force. Surface area of the disc makes no difference to braking force, more holes equal more surface area for cooling the disc, thats all they do.
The pads will produce a force stopping the rotor. Torque = force * radius so the bigger the rotor the bigger the braking force.
Force isn't what you're measuring - you want to dissipate energy and that fixed regardless of rotor/disc size.The pads will produce a force stopping the rotor. Torque = force * radius so the bigger the rotor the bigger the braking force.
To anyone who thinks that bigger discs will not give you more braking force, ask yourself if your braking would be as efficient with a disc half the size.
The diameter of the disc is a factor. The braking force between the pad and the disc is multiplied by the radius of the disc.
Just be careful not to go too big and have them locking up too easily.
[edit for pur spelin]
Edited by Raven Flyer on Friday 9th September 12:06
Mars said:
Force isn't what you're measuring - you want to dissipate energy and that fixed regardless of rotor/disc size.
The level of basic maths is shocking.Energy = force x distance
So to reduce your kinetic energy , a larger force requires less distance.
Force at the tyre = (Force at the pad x disk radius)/tyre radius
If you go too large you end up with a set of magura hydraulic rim brakes, which when combined with a ceramic rim are amazing.
Mars said:
You all missed my point - I wasn't disputing whether you got more force or not.
Not sure what your point was.You state that the energy is the same. Yes the amount of energy you need to dissipate is the same, but larger disks enable you to do this in a shorter distance/time.
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