Bicycle Mechanics - Brakes.. Very poor stopping power!

I am using my sidepull brakes again.. This is the one with no adjusting(centering) screw.. So alignment is a bit hard..

Anyway, the original pads were hard and brittle(I posted on other thread), so I replaced the pads..

Although it has improved braking, I belive it is still very poor.. I can't use the brakes for emergencies.. I can hardly stop me..

I have new cables and housing(the best I could find)... But instead of the metal ends(the one covers the cable ends), it has plastic ones which look very nice... Would this be the problem?

I have installed cables on other bikes, but this is the first time I had a problem like this..

The front brakes are fine, but I still lacks the power.. I weigh 200lbs, but its no excuse to have crappy breaks..

The rear however, is too weak.. When i grab the brakes(lever) it has a spongy feel.. It locks unto the rim, but you can still press harder until it touches the bar tape... And still it has too little power... The cable is well adjusted, and routing is fine(my standards though)...

By the way, the rim is new(rigida sphinx 700c)... Is there a break-in time for the pads? are the cables expanding? are the housings shrinking? I don't know why this is happening...

Anyway, how do you adjust toe with sidepull calipers?

The calipers are Shimano105... The green one.

I need your help.. I need brakes.. Its too dangerous to go out w/o brakes!

Thanks everyone...

Have you checked that your cables are pre stretched? If not, the cables will stretch the first few times you apply them, and lever travel will increas.

the type of end cap means nothing. Check your cable layout is not knked, and make sure that the brake pads are suitable for the rim you have.

Switch to a softer or wet weather compound might get better (if grabbier) results. they'll wear faster too.

Toe in on sidepulls is usually adjusted by application of mole grips and brute force, unless the pads have adjustment built in. be careful if trying to bend the caliper arm to toe in. Some are fragile.

Another way would be to angle grind the rear part of the pad down slightly.

If you can pull the brake lever to touch the bar, they are not adjusted properly. Brakes should be tight before that point.
Shimano 105 calipers are excellent with little flex. Brake pads do need a little wearing in. I usually roll down a steep hill and keep the brakes applied to run them in.
Koolstop pads are reckoned to be the best.

The housing is compressing. You want to shorten up the housing as much as practical and there is a fancy housing made with both straight and spiral windings. It compresses very little. You might also scuff the rim with emory cloth then wipe it down with rubbing alcohol. Also dress the pads with sand paper or a file, they may have glazed up some with the long stops.
If that Rigida is hard anodised, it may take a while before the rim beds in.

thanks all..

I'll be trying all your suggestions... I will update you on the results..

Wish me luck.

A couple of other random thoughts:

1) are you using dual-pivot calipers with levers that are designed for single-pivot calipers? Maybe the mushy feel is partially caused by a lever with more leverage and less cable travel than the caliper is made for.

2) perhaps your cable housing is not seating properly in your brake lever. What levers do you have? For example, if you have a Shimano STI brake lever, or most other Shimano road brake levers, then you would usually not use a housing cap ("ferrule") where the cable housing meets the brake lever.

3) a variation of #2: if your cable housing was not fully seated in the brake lever when you wrapped your handlebar tape over the cable housing, then the cable housing may be unable to seat since the handlebar tape holds it away from the lever. This could produce a mushy feel. If you think this might have occurred, then unwrap the bar tape that covers the brake cable housing and squeeze the lever firmly to seat the cable housing in the lever (after removing the ferrule from the housing if you put one on it).


edit: also, it may help to flatten the ends of the housing with a hand file, a rotary tool, or a grinder.

I didn't get much sleep last night so maybe those are daft suggestions, but who knows...

thank mechbgon..

I'm working on it right now..

The cable is seated properly and the ends flatten by a grinder.. I did this when I installed the cables..I will recheck the seating..

I am using STI levers with shimano 105 sidepull calipers(the safety something one???). This calipers are those without the centering screw/bolt type... Very hard to align.. I think this was the reason I didn't use these calipers much..

I will test ride it this afternoon(+800 GMT).

An update:

1. replaced the cable housing but retained the cable..
2. replaced all plastic end caps with metal ones.
3. aligned the pads and pivot.
4. pretightened cables
5. cables are well seated(removed some ferrule(s) to make cables seat properly).

Result:

1. an increase in braking performance but still performs poorly..
2. Still has that spongy feel (feels like there's a modulator like those with MTBs)

Is it the cables then? I am using MOB Pro cables(these cables costs twice as much as shimano cables)... Now I replaced the housing with those from Shimano..


Any more suggestions??? I need help.

Thanks.

just for reference...

Is this brake compatible with STI levers?

see pic below (shimano 105)

The STI levers do, in fact, have a modulator (unless they've changed them)! Look at the thing that the head of the cable sits in... it rides in a slot, yes? And look at the "roof" above it, is there a wave-shaped piece of plastic there? Ah so, grasshoppah... ;)

The type of brake in your diagram is not what the STI levers are built for, from a cable-travel/leverage standpoint. It is understandable that it would have less power, but I would expect the lever to feel very firm, not spongy... like if you paired up a V-brake mountain lever (high travel, low leverage) with a non-V brake.

If you can afford dual-pivot calipers, that may help a lot.

http://bike.shimano.com/product_images/BR/components/BR_5501-S_Component.jpg

are the pads aligned properly? they should hit the rim flat. or you can toe them in so that the front of the pad (the leading edge) hits the rims first. use a old playing card under the rear part of the card to achieve this.

this will help w/ the squishy feeling.

make sure your rims and pads are clean. I wipe mine down w/ glass cleaner or any other grease type cleaner.