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Brakes as well as first 850 mini - HELP?

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Brakes as well as first 850 mini - HELP?

Old 08-10-15, 01:13 PM
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amuseboucheUK
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Brakes as well as first 850 mini - HELP?

Hi

Newbie to the group and wondered if anyone could advise as to why my rear brakes do not seem to work as well (if at all) as my front ...

I've just got back into cycling for fitness as my knees cant take the running anymore so I dig my old Raleigh Max MTB from behind the kids bikes in bike rack and set about some maintenance before heading off to coed y brenin last week ... the original cantilever brakes were shot so I got a nice shiny set of new ones from eBay and fitted them ... although the front seemed to work (a lot) better than the rear I though it would probably be okay ... well it was BUT if I want to do anything more serious I need to get the balance right else I'm obviously going to be heading over the handlebars more often than not!

Looking at the geometry they appear to be set the same as the front ... I have got the cantilever bars as wide as possible to give best mech advantage but they do not stop me anywhere near as quick as the front can ...

The pads are the same front and rear (they were a set) :



The only thing I think it could be is that the rim needs to be "cleaned" ... the rims are aluminium (Alsea Challenger) ... is this likely and what's the best way to clean them (wire wool and elbow grease?)

Anyway ... thanks, in anticipation, for your wise words.

Matt
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Old 08-10-15, 01:24 PM
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wondered if anyone could advise as to why my rear brakes do not seem to work as well as my front ...
physics , as you decelerate the rear wheel is unweighted as the mass, mostly You, moves forward.

First of Newton's laws of motion: you are the body in motion that wants to stay in motion ,
the brake friction is the force acting to arrest that forward motion .


I dont feel a great need to have my brakes with that kind of shoe post all the way out on the ends like that .

to clean a lot of stuff I bought a carborundum grit impregnated version of the 3M'scotch-brite' scrubbing pads

in an 8.5x11" [A9] sized sheet at hardware and marine supply shops ,,

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Old 08-10-15, 01:44 PM
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Let's demythtify things a bit.

1- and most important. The risk of going over the bars is 100% dependent on the front brake, with the rear brake having little to do with it because as braking forces increase, the weight transfer forward allows rear brakes to skid the wheel with little effect on slowing the bike. Using the rear is a bit useful because if it locks the wheel, that's a bit of a warning that weight has transferred forward. It's not a precise indicator, but with experience becomes part of your feedback loop in controlling both brakes.

The rear brake should be able to lock the rear wheel without needing help from the front, but with heavier riders you won't lock the rear wheel unless you provide front wheel braking to help shift the weight forward a bit.

Reasons for poorer rear brake performance vary from things like cable geometry, longer cable length, brake shoe strike angle, separation of barke bosses, and so on.

One common reason is much simpler --- front rims stay cleaner. The front wheel operates in a clean environment, even in the rain where ithe tire's spray is directed back and away (to an extent). But the rear wheel gets the spray from the front, which includes what bounces off the chain and crankset. Add to the any oils coming from the drive train even without the help of the rain.

I always start a rear brake issue with a good wash (real detergent/water mix with some elbow grease, followed by good rinse)of the rim's brake track and the shoe itself. Only after eliminating a possible oil film do I start looking for other issues.
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Old 08-10-15, 01:47 PM
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How do they feel? Soft, so that the lever is bottoming out on the handlebar? Or are they rock hard but provide no braking power?

Did you install a new cable and housing? It's possible a poorly cut or poorly routed piece of housing is introducing too much friction and screwing up your brake. Pad placement looks roughly correct based on the picture.
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Old 08-10-15, 02:22 PM
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Thanks for the super quick responses ... and in answer to some of you suggestions and questions ...

@Fletsbob ... I have them extended to give max mechanical advantage ... almost cyclo-cross style? - also the rims are 1" wide but the tyres are over 2" so it gives a chance for the cantilevers to clear the tyre wall. Thank you I'll look out for that type of scotchbrite ... I use the standard green ones for "peeling" veg so may have a go with one of them and some hot soapy as suggested by @FBinNY ... and yes FB ... at just over 100kg I am a "heavier rider :-) and thank you for the rest of your post ... much information of interest there!
@FastJake ... not bottoming out ... and not soft (but softer than the front) and I installed new cable but used the existing housing ... I did check the housings and made sure they were burr and dust free but it may be worth investing in some nice new ones ... my initial thought was that the rear cable is longer so will stretch more overall length, mainly initially as a new cable than the front, but that this should reduce as the cable beds in.
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Old 08-10-15, 03:01 PM
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Lose the link wires and instead use a straddle wire and carrier; I have had great luck with the Problem Solvers Wide Cable Carrier Problem Solvers

Set it so that the wire is as low as possible.

However, you will need something like a reflector bracket under the wire to keep it from fouling the tire (and locking the brake) if the main brake wire breaks or comes loose. The stiffness of the link wire will prevent this but is the only advantage IMO.

Kool Stop Salmon pads are my default choice.
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Old 08-10-15, 03:10 PM
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Originally Posted by dsbrantjr View Post
Lose the link wires and instead use a straddle wire and carrier; I have had great luck with the Problem Solvers Wide Cable Carrier Problem Solvers
This shouldn't be necessary. I have link wires on a couple bikes and they work just fine, even with drop-bar levers which are a little harder to grab. Honestly, I'd love to buy a big box of various sized link wires and use them on all my canti equipped bikes due to how easy they are to setup. The straddle wire is such a pain by comparison.

I do agree on the Kool Stop pads though. They can make a big improvement.
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Old 08-10-15, 03:24 PM
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+ those link-wire pieces are made in several length configurations .
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Old 08-10-15, 05:55 PM
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Originally Posted by fietsbob View Post
+ those link-wire pieces are made in several length configurations .
I find that the straddle wires allow more latitude for adjustment, and I only have to stock 1 kind. YMMV.
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