Avoiding overheating disk brakes.

[Bateleur1]

On Saturday  I went on a what was my toughest MTB ride I have yet done and involved a almost 20 km route of pure climbing on dirt roads and rockey hiking trails for 95% of the road.

 

Going down my inexperience on dirt road was very noticeable and did not go down as fast as the other guys.  But towards the end of the descent my confidence was improving.

 

However the last 5 odd km was on tar but the downhills according to Strava was in excess of 30% (not sure how accurate it is but can assure you it was bloody steep as we rode it out).  Now by the time we reached this section and being back on tar I would not say that I was lacking confidence and was in the slip of two other riders going down but we had to do alot of braking as it was very very steap in hairpin corners of note.  On the approach of the final bend I realised I am in big trouble.  That sinking feeling you get when you are pulling onto the brake levers and the just do not grip.  I immediately started alternating between the break in an attempt to cool one and use the other just to reduce the accelaration.  The other guys did not have a problem but I suppose being the taller and bigger guy of the three I would be at the greatest risk.  To make things worse is at the bottom of the hill are hikers and kids.  Losing control and I would wipe them out as well.

 

I eventually realised I am not going to make the final curve, the bike is increasing speed, I actually dropped of the back of the saddle and skid on my shoes and managed to reduce enough speed to make the final curve and come to a halt much to the amusement of some big eyed hikers.

 

My question is, what techniques are there to avoid overheating breaks.  Regular stopping? Harder shorter breaking periods?

[Rocket-Boy]

I have heard of that happening on Shimano brakes fairly often, is it a mineral oil thing where it is contaminated? 

Not trying to start a Friday response, genuine question.

[dirtypot]

IceTech brakes might help?  Cooling fins on the pads and the rotors are made of three layers to help disperse heat.

[Bateleur1]

One of the other bikes were also Shimano.  Not sure about the third.

[porqui]

Thicker and/or larger diameter discs.

 

Otherwise come down slower.

 

Speed and mass have an exponential effect on slowing down.

[Wannabe]

Chuck those Shimano's in favour of SRAM......

 

 

 

 

 

 

Just joking, L.

Try not to keep the brakes engaged for too long periods, use the front brake more as you have more stopping power (and bigger rotor) on the front. Don't "stay" on the brakes the whole time, feather them lightly to reduce speed.

 

 

In the end, if this does not work, try fitting a proper brakeset...... 

[Bateleur1]

IceTech brakes might help?  Cooling fins on the pads and the rotors are made of three layers to help disperse heat.

 

Actually I saw that.  My buddy rented a e-bike for the wife so that she could join us and on return he needed to buy new pads in anyway and bought some of those.

[Bateleur1]

Chuck those Shimano's in favour of SRAM......

 

 

 

 

 

 

Just joking, L.

Try not to keep the brakes engaged for too long periods, use the front brake more as you have more stopping power (and bigger rotor) on the front. Don't "stay" on the brakes the whole time, feather them lightly to reduce speed.

 

 

In the end, if this does not work, try fitting a proper brakeset...... 

 

Thought XT would not be so bad. 

[Halfdoesyn]

Thicker and/or larger diameter discs.

 

Otherwise come down slower.

 

Speed and mass have an exponential effect on slowing down.

Actually, speed is the big one. For kinetic energy, you have the formula:

 

E_k = ¹/₂mv²

 

So your energy is proportional to your mass and proportional to the square of your velocity.

 

Go slower or get better brakes.

[Thor Buttox]

I have XT that are 5 months old. They are being bled for the 3rd time already, as the stopping power drops radically over time. Also been told it's an issue with the oil and using the back brake too much. Pity the front one also needs it.

[Bateleur1]

I have XT that are 5 months old. They are being bled for the 3rd time already, as the stopping power drops radically over time. Also been told it's an issue with the oil and using the back brake too much. Pity the front one also needs it.

 

Ok, we might be onto something.  Bike is almost a year old.  Have done 1500 km of which most of it was in the last 3 months.  I have not done any maintenance on the brakes yet.

[JXV]

What brakes and discs do you have exactly?

 

Any hydraulic brake will have problems if it is not properly bled and then heats up. I assume your brakes are bled and have no air bubbles in them.

 

Likewise excessive heat from a long descent can cause brake fade. Are you using Shimano brake pads or some aftermarket type?

 

For the bigger guys, and also if you use bigger wheels (29er) then you should go with bigger than 160mm rotors at least in front. They give more leverage for the same braking pressure so are more effective. Larger disc surface too....better cooling. If you weigh more than 80kg on a 29er or 27.5 then ideally should have at least a 180mm disc up front.

 

Discs important too. Presume you have OE shimano discs. There is some rubbish out there with fancy patterns and more holes than steel friction surface. Shimano Ice-tech discs are brilliant....steel facings with alu sandwiched inside and then a alu carrier. They dissipate heat much much better than normal steel discs.

 

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[Martin PJ]

How is the stopping power reduced? Do you find there is too much travel in the brake lever when you brake?

 

I have this problem on my formula one brakes. I remove the wheel, pump the brake lever a few times and the brake comes up again. Need to do this as the brake pads wear out. When I replace the pads I use a screw driver and push the old brake blocks apart again. The problem is that the brakes are not really self adjusting.

 

 

I have XT that are 5 months old. They are being bled for the 3rd time already, as the stopping power drops radically over time. Also been told it's an issue with the oil and using the back brake too much. Pity the front one also needs it.

[JXV]

Ok, we might be onto something. Bike is almost a year old. Have done 1500 km of which most of it was in the last 3 months. I have not done any maintenance on the brakes yet.

My XT (M785) brakes have over 2 years and thousands of km on them. No bleeding or maintenance needed to date other than occasional new pads.

 

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[Bateleur1]

What brakes and discs do you have exactly?

 

Not 100% will check tonight but google revealed this: Shimano Deore BR-M615 Hydr. Disc Brake (180/160)

 

Any hydraulic brake will have problems if it is not properly bled and then heats up. I assume your brakes are bled and have no air bubbles in them.

 

As stated before, the brakes have not been serviced yet so that could be one problem.

 

Likewise excessive heat from a long descent can cause brake fade. Are you using Shimano brake pads or some aftermarket type?

 

Original components so should be Shimano

 

For the bigger guys, and also if you use bigger wheels (29er) then you should go with bigger than 160mm rotors at least in front. They give more leverage for the same braking pressure so are more effective. Larger disc surface too....better cooling. If you weigh more than 80kg on a 29er or 27.5 then ideally should have at least a 180mm disc up front.

 

29er, according to the specs it is either 160 or 180, will check. Yes at 1.86 meters and 85 kg, I am bigger than the other two guys that went down the hill with me.

 

Discs important too. Presume you have OE shimano discs. There is some rubbish out there with fancy patterns and more holes than steel friction surface. Shimano Ice-tech discs are brilliant....steel facings with alu sandwiched inside and then a alu carrier. They dissipate heat much much better than normal steel discs.

 

Once again not sure which disks. A quick google gave me this (sorry. it is in german),

http://www.linkradquadrat.de/fahrraeder/mountainbikes/hardtails-29-zoll/374/cube-reaction-gtc-pro-29-carbon-flashred-modell-2016?gclid=CNmY192Xts0CFYMK0wodb2sAzA

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[Bateleur1]

My XT (M785) brakes have over 2 years and thousands of km on them. No bleeding or maintenance needed to date other than occasional new pads.

 

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I do beleive that this was an extreme case and think technique was more the issue in a extreme situation.  Few lessons learnt but I am sure there are some things to take into consideration for the next time.