Bicycle Mechanics - Brakes/straddle cable
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1991 Raleigh mtn bike. Has center pull cantilever brakes. The front hardware is original and the straddle cable is about 100 mm long. The rear stuff is gone and I am putting on a new cable and shop gave me a similar piece but it is marked rear, B/82. So it is shorter. I have been told the longer cable gives u less mechanical advantage so the front has "less" grip than rear? Been riding awhile with no rear brakes and thought it was good to have both.
05-18-12, 10:36 PM
So, did you try the new cable? Is the front working satisfactorily? What is your question, exactly?
Front brakes do not work well. Original 1991 Deore xt pads. New brake cable. 105mm straddle cable. Different front wheel. Same material as original wheel. I got new cable and straddle hardware for rear but brake cable is thinner than front. Tech said cables are 1.2 or 1.8 mm. Either derailler or brake cable. But my 2 yr old front cable is thicker than 1.8mm. So straddle clamp will not grip thin cable. Went back to shop. Tech gave me a simpler straddle clamp that allows cable to self cinch. But than front and rear cables are different. Am trying to find rear thick cable.
Main pont was, should I try the 105mm straddle cable on front and the 82mm cable to see if 1 works better? Or get both brakes working? Or get new better pads? Are 21 yr old pads ok?
The front straddle cable has 2 anchor points. 1 is marked F and the 2nd is marked R. I always thought it was for fat or narrow tires.
05-19-12, 08:01 AM
Change your pads first, 21 year old pads are doubtless hardened and ineffective. Kool Stop Salmon pads are often recommended. This, and an adjustment, may be the only change you will need to restore effective braking. Go ahead and swap the straddle cables if you want, it will cost nothing to do the experiment. Make sure that your new cables are installed correctly; if all that you changed were the inner wires I would suggest you consider changing the housings as well. Pay special attention that the housing ends are correctly prepared; filed flat and with the correct ferrules installed. Here is a link to several articles about brakes: http://sheldonbrown.com/brakes/index.html Here is an article on adjusting cantilever brakes in particular: http://sheldonbrown.com/canti-trad.html Just a guess, but I think the markings on your straddle cables denote "front" and "rear", whatever that means. I'd suggest you pick the one which gives you the shortest cable. Generally the shorter you make the straddle cable the more braking force you achieve. Some clear, well-focused photos of your setup might be helpful in giving further guidance.
I put on new housing for frt brakes and FD and RD. I did not do rear brakes and than misplaced straddle clamp. The anchor points on frt cable are about 1" apart so I can effectively make the cable shorter. I think new pads is a good idea. I can post pics? Or include/embed them?
Andrew R Stewart
05-19-12, 01:21 PM
Often the rear straddle cable was shorter then the front due to the less distance the hanger stop was above the tire/bosses. Your 1991 bike was before ft suspension was common so the hanger was likely up on the upper HS or stem. Is this correct? This greater distance allows more choice in the straddle cable length and how that effects the leverage on the canti arms. A higher straddle cable/primary cable junction (the yoke placement) produces a stiffer feel, lower is a more flexy feel. somewhere in between is the sweet spot for max leverage when the pads are in contact with the rim. My understanding of this cable/pad geometry is that when the straddle cable is at a 90* angle with the pad/end of canti arm "line" the max leverage is attained. Really small sized bikes don't always have a lot of this tire to cable stop distance to fully explore the leverage range. Placing the pads at different points along their post is an additional change to play with. Andy.
My frt brake cable is routed thru stem. I put on a stem riser since I have flat bars and I do road/paved trails. Raising bar forced me to recable. Yes it is a rigid fork. I did not want to change bar for a different design. Was easy to find stem riser at local shops in mpls. Even got a black one to match.
here is a pic251214251215
05-19-12, 04:01 PM
Back in the day thicker brake cables were common in MTB land, but not these days.
That's a mega riser!
Straddle looks a little long for my taste.
These are typically prescribed for shudder problems but might help in your situation also, dunno:
05-19-12, 04:15 PM
I would definitely shorten the straddle cable significantly.
+1 on the fork mount cable hanger; when you get your brakes working better shudder may become a problem. I prefer this type, myself: http://www.specialized.com/us/en/bc/SBCEqProduct.jsp?spid=47409 and this cable carrier: http://problemsolversbike.com/products/wide_cable_carrier/ Using the fork mount hanger will automatically make you use a shorter straddle wire. Here's an article which explains the rationale for their use: http://problemsolversbike.com/blog/comments/get_wide/
The front straddle cable is original but that does not mean it is the best for my install. Do the 2 anchor points on it allow for going with a shorter setup depending on ur preference or it is for using different width rims? It is 20 yrs old. Maybe they did stuff like that back than?
05-19-12, 07:34 PM
I solved all my canti brake problems by replacing my Tektro canti's with a set of Deore MTB V brakes. Magic and you won't go back. Just saying. Al
the bottom cable is the original front. it is 105mm and 125mm. i was using it at 125mm. the top cable assy is about a 90mm. the unseen one i am using now is a 82mm and is marked "R". i put on the 82 and the angle from the canti arm to brake pad is about 85 degrees. so its probably too short. i think the thick front brake cable is too thick to slide thru the rigid plastic tube. its raining out now. wait till tomorrow to do some more tweaking.251232
251373ok, this is the shortest cable. i think it is 82mm. stops the same as the 125mm cable. so much for the theory about cantilever arm angle and so on.
Andrew R Stewart
05-20-12, 08:53 PM
Cavell- While the cable/arm angle is a factor in the stopping power of a brake the far more important factors are the pad's gripiness (although I don't like the red compounds) and the hand's strength. The former is affected by age and grit/grime. The later by the whims of our needs. I would set up the angles for the best leverage possible, replace the pads with fresh ones of your choice, lube all pivots and cable/casings and then ride the bike. Andy.
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