Adjusting Hydraulic Disk Brakes

[Tom B]

I have stock Tekto HDC-300s fitted to my bike... They are two piston Hydraulic jobbies

The rears are behaving like they need adjusting for pad wear. Sitting cold i can squeeze the handle down to the bar grip with some effort. Admittedly this is well past lock-out point but still i prefer a bit point nearer the top of the lever. When the brakes have been rubbing and all is hot, it seems a little worse.

There appears plenty of pad left.

I have never fiddled with hydraulics and on the face of it there does not seem any way of adjusting the pads out.

On cable operated disks i would have slackened off the slides and wound the pads out and then tightened. Thee does not seem an option for this.

It does seem on the face of it that both pistons move out and can be retracted and thus the pistons would take up the wear of the pads

Am I being a dunce and missing something or is this just likely to be the pipes swelling under pressure?

The bike is pretty new so is still in the bedding down stages - i just hope it doesnt bed down much more!

 

[Brandane]

Could be some air in the system which needs to be bled out.
Unless you are familiar with the process for bleeding brakes (or have some mechanical savvy and are willing to give it a try) then brake bleeding might be one for the LBS to do. There are some instructional videos on YouTube.

 

[lpretro1]

Hydraulic disk brakes are self-adjusting.If they are new then they should not need bleeding unless you have managed to boil the fluid - in that case it will now have air in it and then would have to be bled. You can usually tell there is air in the brake - pump the lever several times and if it firms up then it has air in it. Check the pads for wear - they don;t always last too long depending on where and how you ride. Check that you have not contaminated the pads with oil or lube - a common error is to use a spray lube round the cassette area - tiny droplets then get on the rotor and onto the pads then they don't bite well.

 

[Cubist]

If you have to use some effort to bring the lever to the bars it is possible you are simply forcing fluid so hard into the hoses that they are expanding. I hate to say it, but Tektro hoses aren't the most robust. having said that I once lost my temper trying to get some braided hoses to seal on some Hope brakes and managed to burst one by squeezing the lever as hard as I possibly could The best advice I can give is to stop doing it!
That aside, if the brakes are working properly, ie stopping you as they should, you may need to adjust bite point as the pads wear. There may be an adjuster screw in the lever assembly which will bring the bite point back to where you like it. I'll have a quick google for you.

 

[Cubist]

Tektro state that the HDC 300 is not adjustable for reach or bite point. Try resetting the pads, they may have bedded in, and if that doesn't fix the feel, you may need to bleed them.

 

[Tom B]

Hydraulic disk brakes are self-adjusting.If they are new then they should not need bleeding unless you have managed to boil the fluid - in that case it will now have air in it and then would have to be bled. You can usually tell there is air in the brake - pump the lever several times and if it firms up then it has air in it. Check the pads for wear - they don;t always last too long depending on where and how you ride. Check that you have not contaminated the pads with oil or lube - a common error is to use a spray lube round the cassette area - tiny droplets then get on the rotor and onto the pads then they don't bite well.

Could be some air in the system which needs to be bled out.
Unless you are familiar with the process for bleeding brakes (or have some mechanical savvy and are willing to give it a try) then brake bleeding might be one for the LBS to do. There are some instructional videos on YouTube.

I have had the pads out and they are only slightly worn, plenty left.

I had considered air in the system, I do regularly generate some temperature in the brakes with 3 big stops on or after big decents on my regular commute (one of the reasons i go a bike with disks) but i wouldn't have thought anything too excessive. I am much more experienced in dealing with hydraulic brakes as fitted to cars and vans but the principle seems the same. I think I am going to get myself some fluid and have a bash at bleeding them up.

I'm not quite sure I follow you when you say that if the lines have air in them that pumping the brakes will firm them up though

If you have to use some effort to bring the lever to the bars it is possible you are simply forcing fluid so hard into the hoses that they are expanding. I hate to say it, but Tektro hoses aren't the most robust. having said that I once lost my temper trying to get some braided hoses to seal on some Hope brakes and managed to burst one by squeezing the lever as hard as I possibly could The best advice I can give is to stop doing it!
That aside, if the brakes are working properly, ie stopping you as they should, you may need to adjust bite point as the pads wear. There may be an adjuster screw in the lever assembly which will bring the bite point back to where you like it. I'll have a quick google for you.

Tektro state that the HDC 300 is not adjustable for reach or bite point. Try resetting the pads, they may have bedded in, and if that doesn't fix the feel, you may need to bleed them.

Thanks, I hadn't really given much thought to the levers!..

The only way i can describe it is that it is almost like an ever lengthening brake pedal in a car, it sometimes feels that I am going to run out of travel before I get enough bite.

I have only ever ridden couple of other bikes with hydraulics and they seem to have a firmer more feel with better feedback. The bite point seems to have moved backwards too since new.

Ill bleed them and see what happens, then I might be looking at new pipes!

 

[I like Skol]

If they are new then they should not need bleeding unless you have managed to boil the fluid - in that case it will now have air in it and then would have to be bled.

Wrong! Boiled brake fluid expels gas bubbles (usually water in old, contaminated fluid) but this returns to the liquid state once cooled... until the next time. Many cycle brake systems now use a mineral oil based fluid as this does not absorb water like traditional brake fluids and is not so aggressively corrosive. Regularly boiling the fluid would suggest unsuitable fluid or contamination. Either way a fluid change is required but this is unlikely on a newish bike that has not been tampered with from new.

I'm not quite sure I follow you when you say that if the lines have air in them that pumping the brakes will firm them up though

Just like car brakes, if there is a small amount of air in the system then rapidly pumping the brakes can compress the bubbles until they liquefy, as the fluid return through the master cyclinder is too slow to allow the bubble to expand before the next pump of the brakes. Once the bubbles are compressed the system will feel just like normal while the pedal/lever is squeezed but once you release pressure the bubbles will slowly start to expand and push brake fluid back through the master cylinder and into the fluid reservoir.

Ill bleed them and see what happens, then I might be looking at new pipes!

I wouldn't waste too much time and money on the Tektros. In my experience they are not great or long lived and you will be much better off putting the money towards something like THESE instead which just work great, period! If money allows then the M785 XT set up are the cream of the crop (but in feel and performance almost indistinguishable from the M615s). The XT set on my commuter have done 6-7k with just pad swaps so far . Don't forget though, the rear brake will often feel slightly spongier than the front due to the longer hose length. Any swelling under pressure is magnified by the longer hose.