Rainbow83

Hello folks,

I just took my first ride today on a bike that I've working on making rideable lately, and discovered something interesting with the brakes. One brake lever, the front, travels quite a bit before it engages with the wheel and begins to apply the brake, at which point, it slows the bike quite well and doesn't travel much further before being very hard to pull. The other lever engages much more quickly, but has a very linear feel in terms of pressure required and doesn't do much to slow the bike down. Both the front and rear brakes are canti brakes and both levers are the same, but the front and rear brakes are different models. I'm wondering if this may be an issue of the pull length of my brake levers (Tektro RL340) and the brakes (These ones on the front and Chang Star cantilevers from the late 80s/early 90s out back). See, I'm not entirely sure which set of brakes, if either, is doing the right thing in terms of when it's engaging and how hard it's braking. I definitely like the power of the front brakes much better, but I'm wondering if they shouldn't engage sooner. I think I've done a fairly good job of setting the brakes up correctly, but I'm no expert. I've attached some pictures so you can see what's going on with my setup. What are your thoughts?

Bigbus

Bill's response is sure to be more correct than mine, but it sounds like a simple adjustment up front and dried out pads in the rear, or contaminated pads and/or rim.

Rainbow83

Should tell me why what? Sorry if the original post was unclear, I'm wondering how the brake levers should feel, if either of those descriptions makes it sound like my levers are designed to pull too much or too little cable for the brakes I'm using, and if there's something I'm missing here. Beyond the fact that the rear cable doesn't quite follow the arc of the pulley and will flex a little when pulled before it tensions, I'm really not sure what I'm supposed to observe here and what it's supposed to tell me. What has the distance the brake posts stick out got to with this? Sorry if these all seem like questions with obvious answers, but I'm asking here because I want to learn. I haven't been doing this for ages like some users here, and there's still a lot for me to figure out.

Rainbow83

Do old brake pads stop functioning as well simply because of age? Do chemical reactions with the air make them dry out and become less sticky or somehow? The rear brake pads are definitely old, but they don't have tons of miles on them.

Bigbus

Yes, old pads are prone to dry out and lose their effectiveness, some to the point where you feel like the cable is about to snap and you're still flying down the road. I've ridden many bikes with brakes like that. As far as lever pull, you start by adjusting the cable where it's attached to the cross cable (not sure of the term there) and then fine tune at the barrel adjuster where it goes into your levers, if you have them. Some bikes have the barrel adjuster at the brake caliper end and not on the lever, but you don't have that setup and I can't see your levers. I have Tektro levers on my Fuji and I love them for what it's worth. Keep asking questions, there will be others here soon to throw answer, opinions, and suggestions at you. Good luck.

Bigbus

I believe Bill is referring to how much of the brake pad post is sticking out on the front ones, meaning you could adjust them in toward the rim more for less lever pull.

Andrew R Stewart 

A few comments- Rear brakes, even with the exact same set up, will always be less "powerful" due to weight transfer during braking and that longer cable. Old "rubber" pads do get less grabby over time. Replacing them with new is among the first steps to improve the performance. Bill's advice is spot on. Here's an image showing the basics of canti set up. BTW I would ditch those pulley straddle cable pull up clips with the common type. The pulley versions make it hard to slide, and stay put, the clip along the straddle cable to better center the pads WRT the rim. Andy

Rainbow83

As far as the cables goes, given that the rear brakes with the really long straddle cable came stock on the bike like that, I kind of figured that that was how it should be. Maybe it isn't, but it surprises me that whatever the manufacturer spec'd would be far from the ideal way to do it. The front brakes are set up with a shorter cable to get the brake arms set up so that they will be about parallel as suggested in this video: (which I think is probably a reasonably trustworthy source) I imagine the differences in the straddle cables makes some difference in how the brakes behave, but I'm not sure what.

Regarding the brake pads, the picture above is a little misleading, and it's a little hard to see exactly how close to the rims the pads are. To clear things up, I measured from pads to rims with a pair of calipers. In the rear, the left pad is 5/32" off the rim and the right pad is 1/8" off the rim. On front, the left pad is 7/64" off the rim and the right is close enough that I couldn't get the calipers in there to measure. So, correct me if I'm wrong, but none of those measurements seem to be particularly far off the rim, especially not as much as 1/2".

Frankly, if you are going to continue to provide vague responses that would be of little help to me or someone else reading this thread with similar problems, I would encourage you not to bother.

Rainbow83

Thanks for the helpful info. I'll stick some new pads on the rear and see how that goes. Your suggestion to replace the pulley style clips with the other style is surprising. I'd imagine that the pulley would allow it to center better, but I guess I can see how if the pulley is getting clamped it might not spin very freely. Since nobody seems to have told me that there's any issues with the matching of the brake levers and the brakes in terms of cable pull as I was worried, I'll probably replace the whole of the rear brakes with ones like the front. The current setup with the fixed length straddle cable is a pain to adjust anyway.

Bill Kapaun

Ditto-
You made my ignore list

Dan Burkhart 

It's about mechanical advantage which is greater when the straddle cable is straight,( closer to the tire) . It means you have to pull the lever further, but has the effect of moving the fulcrum closer to the load for more advantage.
There's actually a bit more to it than that, but that's the general idea.
Also, for the front, it's more than just a good idea to have something like a reflector bracket to prevent the straddle cable from falling onto a rolling tire That could end badly.

Andrew R Stewart 

That the pulley clip will move along the straddle cable on it's own is exactly the problem with keeping the pads centered. The goal is having pads centered, not having the clip centered. Often by moving the clip slightly off center one can better keep the pads centered as the friction and/or spring tensions of the two canti arms are not always identical.

The shorter the straddle cable gets the more mush will enter the system. As in more lever pull for less pad movement. People with weak hands often like this. Andy

blamester

So the park video does a good job of explaining how to adjust brakes.
But the only variable is you.
So the brakes have to be adjusted to function for you. Your speed, your hands, your strenght and terrain and the conditions.
This requires a bit of experimentation.
The brake has to stop you in all conditions easily.
I set my brakes up so that maximum braking I will ever need is just before the lever hits the bar.
I set the pad distance to the position where my hand or finger has a good positive grip of the lever before the brake is engaged. Meaning I leave some of the lever pull free to fit my hand better or not as the case may be

So if those conditions can't be met comfortably then a new combination is required.
So experiment. Consistent easy braking is the key.
Always give them a good pull before you set off.


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hokiefyd 

The front brakes are low-profile cantilevers. In general, you'll get the most mechanical advantage with these by pulling the cable anchors laterally (horizontally). For this reason, the lower you can get the straddle cable, the better.

The rear brakes are wide-profile cantilevers. In general, you'll get the most mechanical advantage with these by pulling the cable anchors straight up (vertically). For this reason, the longer you can get the straddle cable, the better. With wide-profile cantilevers, a lower straddle cable puts the force vector on the cable anchors closer to in a line with the brake arm pivots. This quickens the actuation speed and, at the same time, reduces mechanical advantage. Pulling at 90 degrees to the brake arm angle will create the slowest actuation speed and also generate the most mechanical advantage. It's often not possible to pull these at exactly 90 degrees, so you do what you can.

This is why the rear brake feels like it actuates quickly but has less stopping force. It'll cost you very little money to get a longer straddle/transverse cable and move the the straddle cable hanger up closer to the brake cable stop on the frame. In theory, this will improve your rear brake mechanical advantage. Or, you could replace the rear brakes with low profile brakes like what you have on the front and lower the straddle cable to as low as practicable.

All of that above is assuming the brake pads are similar in age and condition. Of course, if the front pads are new and soft and grippy and the rear pads are old and hard and glazed...that could explain it as well.

Edit: in addition to the above, if you're interested, that rear brake would be a great way to tinker and figure out what combination feels best to you. Scenario 1: make the straddle cable as long as possible and see how it feels. Scenario 2: make the straddle cable as short as possible and see how it feels. The optimum for you may be somewhere in the middle, but I suspect you'll like brakes better if you go towards either extreme. I think a shorter straddle cable on the rear brakes will create more of what you have now -- it should create a faster actuation speed and even less braking power. But...it'd be easy to test. It wouldn't cost more than a few dollars' worth of brake cable and some time.

Rainbow83

Thank you all for such detailed explanations. I think I have a much better idea of what I'm working with here and what I should do to figure out what I want. I'll replace the pads on the rear brakes and maybe have a try with a few different straddle cable configurations before I decide if I want to put another set of low profile brakes on the back. I'll also stick on some reflector mounts to keep the cables off the wheels. Again, thank you for all the very helpful responses.

oldbobcat

The pad studs should be horizontal at rest and the angle of the straddle cable should be 90 degrees at the harness for best mix of power, responsiveness, and ease of wheel removal (after detaching one end of the cable).