I know this is an older less expensive brake system so not sure of my best options. The brake lever are quite firm so is there a way I can remove a bit of the hydraulic fluid from the system? I also find them very difficult to maintain alignment with my rotors...would removing a bit of hydraulic fluid put less pressure on the pistons and open the brake pads even the tiniest bit? Any help is greatly appreciated.
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What do you mean by maintain alignment with your rotors? They shouldn't really be able to go anywhere. How old are the brakes and how long have you been using them, have they been re-bled or are they straight out of the box?– Nate WNov 3, 2016 at 22:42
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I've used them for about 6 months now with 180mm rotors. I've recently replaced my rotors again with brand new rotors which I know are not warped in any way and nomatter what I do the rotor scrapes the pad on rotation. The brakes have never been bled and I still have the original pads installed from out the box which have loads of wear left on them. The brakes have always felt very firm from out the box is it possible they have too much fluid in the system.– Dave LNov 3, 2016 at 22:51
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I personally have never had or heard of an overfilled hydraulic brake, and i'm not sure if that would even be possible as you can't really pressurize the system. You can't put more fluid in than what will fit.I have heard that The Clarks skeletals can be a little stiff, but they should not be dragging the brake pad, that's for sure. I don't however think bleeding them would hurt anything, probably worth a shot. Also make sure that the piston is not sticking, if you clean them use alcohol.– Nate WNov 3, 2016 at 23:00
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How would I go about checking the piston? I must say the brake lever don't immediately spring back with as much force as they originally did. I will bleed them in the next few days as the rear hose is waayyy too long for my current frame so need to shorten it. Thank you for your help with this really!!– Dave LNov 3, 2016 at 23:05
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you should be able to tell how well it is moving by looking at it push on the brake pad while someone pulls the lever, just don't pull the lever with no rotor in place or a bleed block or you can pop the piston all the way out, which is bad. lol Your welcome, sorry i didn't have a more concrete solution, hopefully someone else will chime in as well.– Nate WNov 3, 2016 at 23:27
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1 Answer
I'm reading the question as saying there's too little pad gap and it's causing rub as well as lever travel that seems too tight/short/firm.
The first thing to do with any problem of this nature is to try pushing the pistons back in (after cleaning the outside if needed) and re-adjusting the caliper centering. Pistons that have somehow gotten pushed out too far can cause all the problems you're having. Some good tools to do this are a tire lever or an 8mm box wrench against the piston faces directly, or a degreased cone wrench, table knife, etc against the pads. It can help to slightly lubricate the pistons first with whatever fluid the system uses (DOT 3/4 fluid in this case) after cleaning them, in case drag when passing through the caliper seals is causing retraction issues.
Overfill per se is not usually the problem, although it is possible to overfill a brake using an incorrect bleed block. What usually gets mistaken for overfill is DOT fluid expanding due to absorbing water that makes it past the seals, because it absorbs water out of the air very readily. Most or all DOT fluid brakes seem like they do this to some extent over time, or at least can. (Mineral oil doesn't do this, which is one of its advantages). It's extremely common, for example, that a new bike that's been sitting warehoused halfway through a model year has this symptom when unboxed for assembly. When Juicy 3s were one of the most commonly specced brakes it seemed like half of them had this out of the box.
If you observe that the pistons can't be pushed back in fully on a DOT fluid brake, fluid expansion due to water contamination is the first thing to suspect.
The simple option is to "burp" a little fluid out by removing and putting aside the pads, putting a rag up to the caliper bleed port, slightly opening the port, and resetting the pistons with the port open (again cleaning/lubricating the pistons first as needed). Some fluid will come out, which the rag is there to soak up before it makes a mess. Close the bleed port quickly when you're done of course. This usually works fine for all intents and purposes. You are reducing the boiling point of the brake fluid every time you do this as well as increasing its compressibility, both of which could hypothetically make some kind of meaningful difference at some point, but we're really talking about a very small amount of water. You also shouldn't try this if you're not prepared to bleed the brake in case something goes wrong. I'll add the disclaimer that I haven't actually done this on Clark's brakes, only on many, many Avid/SRAM brakes. Wear gloves and eye protection.
You could also replace all the fluid, which is the safer and technically correct path if water contamination is suspected.
answered Nov 4, 2016 at 6:49
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That is quite possible really especially seeing as during the past rainy I've not had space to bring the bike inside. I've got a good weather cover for it but it's old and got loads of big rips where my tyres have torn it open. I've ordered a bleed kit online and I'll have a go at it when I've got it. It probably doesn't help that I noticed the post mount adapter on my forks is stripped so I can't secure the lower caliper bolt at all...not sure if it's fixable but I've got a spare fork I can use. Thanks very much for the help with this issue.– Dave LNov 4, 2016 at 7:01
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You're welcome. Stripped post mounts can be usually be helicoiled. It's an M6x1 thread. Nov 4, 2016 at 15:21