Maitoy - canti brake geometry calculator

[MartinC]

http://www.circleacycles.com/cantilevers/

This site used to work in older browsers and allowed you to dynamically plot the MA of different brakes and straddle heights.  It doesn't seem to work with current browser versions - does anyone know of an updated version?

[rogerzilla]

Looks awful on my phone (running Firefox).

Basically...pads as far out on their studs as you dare without introducing vibration, straddle as low as possible for low-profile arms, height not important for old-school wide arms.  If braking is still crap, fit better pads.

[Brucey]

still works OK with IE.

If this is a question about using centre pulls with particular levers, which are they?

cheers

[MartinC]

Yes, it used to work fine with IE, but I upgraded my PC - maybe I need to resurrect IE and ignore Edge.

It is a segue from the 4700 thread.  I can't remember how CP brake MA and cable pull varies with the straddle height.

I've got a fairly traditional steel frame (Soma Pescadero) that takes 35mm tyres with MG's and caliper brakes to build up sometime.  I may use some mid noughties Veloce 9 speed ergos with some centrepulls or Tektro R559's, which I'm reasonable confident will work OK.  One of the other options is 4700 'cos I've got mechs and chainset from another donor bike - I was just idly wondering if tarting around with the straddle with length might get the cable pull and MA to better match 4700 STI's and GC700's.

I've also got some traditional Dia Compe brake levers with sprout cables and friction shifters in the spares box too so it's all the stress of choice really. 

[Brucey]

The Dia Compe levers with the centre pulls will be a good combination, and so with the campag ergos with the Tektro DPs.  With ST4700 you must use a NSSLR caliper, else older DPs will be a 'bit wooden' and centre pulls will be quite a bit worse than that.

You don't need a calculator to see that altering the straddle length doesn't make that much difference with most CP brakes; obviously the caliper MA reduces whenever the brake blocks are lowered in the slots, but at the straddle end, just put a horizontal  construction line through the two arm pivots, and see where the projection of the straddle cable intercepts them. From the intercept point to the arm pivot  is the 'virtual arm length'. If you can make this arm length longer, then the MA is improved.  However whilst you can improve matters,  IME you never get that much bang for your buck by altering the straddle length (mainly because the straddle is always anchored close to the construction line) and what you do get is usually lost very quickly as the brake blocks wear, if you adjust the cable in the normal way.

The only cantis which respond well to attempt to tune the MA are mid-arm ones; it is the same story with virtual arm length but in this case you can soon work out that you can roughly double this between a very poor setup and a very good one.

cheers