ModeratedUser

Hello all,

I'm not a noob to disc brakes. Granted I'm definitely not the ace-know-it-all either! I do have some experience with disc brakes and I've used them alot in my MTB riding. I figured in this day and age they would have progressed quite a bit since they've been out there forever, it seems. So anyways on my discs in question are on a CX/touring setup. The bike is only 2 years old and they have, what looks like are good quality brakes. They are the mechanical Hayes CX Expert brakes. I bought the bike and the guy advertised that he put 200 miles on the bike. Going to see it and it was VERY clean. He then said he probably put 50 miles on the bike. That seemed more accurate. I tested it and brakes were crappy. This was on bike that was way over $1k new. I got the bike home and cleaned up the surface of the discs with alcohol. This gave me some braking power back, but nowhere near what it should be. Going down a paved hill I think I should be able to apply good pressure and lock up the back brake, but nothing. The front it should be if I applied good pressure I should be in danger of flipping if I'm not careful, again not close. There was even evidence of the brake fading going down one hill!

So I know if I had bank, you end up pulling the brakes and putting the best brakes money can buy, but I don't have bank. Roughing up the discs might work, but does that mean maintenance work down the road? I do have bank for the best pads money buys, as long as they aren't diamond encrusted.

Any ideas? Thanks for reading this and I most welcome any and all replies.

dabac

New pads, bigger rotors, good compression-resistant housing in no particular order.
Oh, and a proper bedding-in.

DrIsotope

Nine times out of ten, it's contaminated pads. Just buy new ones-- they're super cheap. Rotor thickness/glazing shouldn't be a problem with that low of miles. Clean the rotors well (denatured alcohol, acetone, or brakleen,) install fresh pads, set the pad clearances, then bed-in the new pads.

bikeman715

you might want to change the pads , cables and housing to see if that will improve things before anything else .

cpach

Those are pretty decent brakes. Mechanical discs are relatively sensitive to setup. My preferred method is to:
Completely loosen cable, loosen caliper bolts (assuming post mount)
Fit a business card between the moving pad (the more outboard one) and the rotor, adjust fixed pad until the rotor is pressed against the moving pad and nothing can move.
Tighten caliper bolts.
Back out fixed pad until rotor does not rub against it. Hopefully, the caliper is now aligned to the moving pad just far away enough not to rub. If it seems askew (rather than the rotor just being out of true) you may need to slightly realign the caliper by hand by slightly loosening the caliper bolts.
Move the cable clamp so it begins to move the pad, and clamp. This should result in a good lever feel--adjust to taste.

If a good adjustment leaves you wanting, I'd sandpaper the rotors, clean them with alcohol, and see if that fixes it.
If still wanting, using compressionless brake housing improves mechanical discs in particular.

ModeratedUser

Thanks for posting! I'm gona give the current brakes a good o' college try, but I'm also eyeing at getting the pads replaced. If and when that happens, I'll be using your tips here as a guide.

Thanks again.

Tape2012

+1. I would suspect the original owner contaminated the pads when he cleaned the bike to sell it. ArmourAll, wax or something like that.

DrIsotope

My thinking as well-- I bought my current calipers used, and the seller solvent-tanked the whole caliper, with the pads still installed. They were wrecked. Shame too, as they were Swiss Stop, and appeared to be practically brand new. Wouldn't stop for anything, though.

cyccommute 

I think "bedding in" is one of those things people tell you to do so that you'll go away and get used to poorly functioning disc brakes. I have never "bedded" a rotor or a pad. I just ride and use the brakes. Any "bedding" should occur through use.

How much lever travel is there before the brake pads contact the rotor? I've found that disc brakes are very sensitive to excess lever travel...much more then rim brakes are. If the lever is set up for the "usual" pad contact happening at half lever travel that some people use for rim brakes, disc brakes will perform very badly in my experience.

The levers need to be set so that the pads contact the rotor with minimal lever pull. Hayes says that there should be a 0.3mm (0.0118") gap between the pad and the rotor. That ain't much.

ModeratedUser

Well I got some pads from Performance. Some Clarks Organic pads. Granted they aren't seated yet, but so far these pads are pooh as far as I'm concerned. They are going to have to improve by 100% if these are going to work like I imagine disc brakes to work. I just installed the rear pads so far. I can't even come close to locking up my rear wheel! You think that's a possibility nowadays? Any idea how to achieve this? Please don't say hydraulics!

Canker

Even the crappiest mechanical disk brakes can lock up a wheel if they are setup right. How much lever pull do you have before the pads start to contact the rotor, I'm guessing a lot. Get those pads closer to the rotor and take out as much of the slop at the levers as you can without the pads rubbing the rotor. This whole bedding the brakes thing is way over rated. Brand new first time out they should work fine, they just work a little better after a few rides.

joejack951

Did you check and adjust the alignment of the calipers and the distance of the pads from the rotors? It may not seem like much but it really is critical to get this right, so take your time doing it. Also, I think in general, organic pads are going to be quieter but they aren't going to have the bite of a (semi)-metallic pad.

Also, which levers are on your bike, Shimano, SRAM, or Campagnolo?

cyccommute 

Start by getting rid of the Clarks. In my experience anything that Clarks makes is pretty low on the quality spectrum. If you can't get Hays, Kool Stop is a much better choice than Clarks.

In addition to the lever travel that I suggested above, you might want to look at the rotor size. I'm assuming that this is on a road bike an they tend to use tiny rotors which are, in my opinion, ineffective. Look at it this way, you are going from a 622mm rotor to a 140mm rotor for many road bikes. Of course the braking is going to suffer. This is what Santana Tandems has to say about it..

Go to a 180mm rotor.


I don't agree on crappy disc brakes being able to lock the wheel. The problem is that they can't be set up right. Some just have too much flex in the system.

I agree that the pads need to be close to the rotor and that bedding is somewhat akin to waving chicken bones around the bike.

ModeratedUser

@joejack951, Canker, I have the alignment down spot on. I didn't even take the bolts loose that dealt with the alignment. The clearance on the pads to the disc is pretty tight too. It's less than a business card thick. And yes organics seem way quieter than metallic. Finally these are Shimano 9sp drop levers.

@cyccommute, yeah I'll definitely go metallic if these don't work out. Seems kinda whack that I've got to upgrade the rotor on this. Granted I'm not the lightest dude out there, but it's not like this is a tandem either.

I'll get at least 100 miles on this before figuring out what to do next, but right now, I'm just glad I didn't replace the front pads too.

On the adjustment right now; I can squeeze the lever to the handlebar when I'm in a drop position. I still can't lock the wheel. There really isn't much room for "adjustment" either. I can get a little out, but there isn't much there.

joejack951

Huge red flags: gap between disc and rotor and bottoming levers. It sounds like you have WAY too much clearance between the rotors and pads. If the alignment is truly spot-on, you ought to be able to set the pads such that you can barely see any gap to the rotors at all. If you can't, either your alignment isn't as good as you think it is or your rotors are warps, or both.

It's no wonder that you can't lock a wheel if you are bottoming the levers out. Some of that could be using regular brake housing which compresses considerably and can affect disc brake performance, but the majority of it sounds like it's stemming from the pad to rotor clearance.

ModeratedUser

There's practically no clearance between the pads and the rotors. I left some so I'd have some adjustment or leeway. Can take a pic if needed. It's truly about a sheet of paper or two. And yes, I can barely see any gap there. And2 the rotors are practically new. The dude I bought the bike from didn't ride and I barely have ridden it. Meaning they are pretty darn straight.

I am bottoming the brakes out when squeezing hard and in the drop position. I should be able to lock the brakes when I'm on top the hoods, but that ain't going to happen!

I have yet to be caught by this disc brake on road bikes bug

Canker

What levers are you using? That is the only other than I can think of that could be causing this problem. They could have the wrong pull ratio.

fietsbob

from another thread: logically this also, applies to fresh brake pads.

DrIsotope

I don't think in our application it's so much actual bedding-in as it is just the pads and rotors adjusting to fit one another-- no matter how flat that rotor surface looks or feels, it isn't. I notice it regularly takes 2-3 rides after installing new pads or rotors for the braking to get really good-- which may only be 20 applications, really. On many rides, I don't recall using the brakes more than a handful of times.

Also, a hearty yes to bigger rotors-- run the biggest you can fit, really. No reason not to. Pads last longer, modulation is better. I wish I could fit a 180mm on the rear so I could put a big cartoony 203mm on the front.

ModeratedUser

Shimano 9sp drop levers.

ModeratedUser

I'm not really that hip on what fits and what doesn't. Seems like what makes the difference is that mount between the frame and brake, right?

I'm not excited in having to do this!

redlude97

first things first can you lock the brakes up rolling the bike on the ground without the lever bottoming out? If not there is a setup or compatibility issue.

joejack951

I love my recently built disc brake road bike. But I have had a cross bike (used as a commuter) since 2009 with a front disc (Avid BB7). Plenty of love for that bike which saw a lot of bad weather and lots of hard braking.

You mention leaving some clearance for 'leeway.' Don't. Get the pads as close as you can even if they rub ever so slightly. You can always fix the slight rubbing later if it doesn't go away on its own.

New rotors don't mean true rotors and even true rotors can be warped when mounted on an imperfect hub.

Your brake levers shouldn't bottom out period. If you can't tune your brakes so that they don't bottom you are using the wrong levers for the calipers. I know a bit about the latter situation from adapting Campy levers to TRP HY/RD calipers. But I don't think that's the case here.

joejack951

Both of my drop bar bikes have 160mm front discs. I can get the rear wheel to lift off the ground while stopping easily on both. If you weigh considerably more than me (160 lbs. currently) then maybe something bigger makes sense, or if you want even lighter lever feel. I would wait on swapping rotors until you've fixed the lever bottoming issue first.

ModeratedUser

Sounds like I'm not sitting on the bike when this is happening, so yes, I could do that. Also we're just dealing and focusing on the rear brake here. And yes the front brake is pooh too.