Locked Disc Brakes.

Tone C

Okay, now I have a number of bikes in my spare room. There's one with V brakes (not an issue) and 3 with Shimano discs.
The issue I have is with my Boardman Pro FS 2016 which has SRAM Guide 4 piston hydraulic disc brakes...(I know, I know).

Haven't ridden this in several weeks and thought I'd shake the cobwebs off her tomorrow with my son. My Shimano disc braked bikes are fine. However the room does get very hot and when I went to check tyres etc I found that the front and rear brakes are locked on. As the room has cooled the brakes are freeing up. I suspect the fluid has heated /expanded and caused the brakes to seize on and as the temperature cools they are releasing?

Thoughts? Reckon I can get a sneaky ride in at 6am before it heats up?

jamski

Never had it myself, but have read about it. Shimano and Sram use different fluid. Shimano is mineral oil, sram is dot fluid. Not sure if that’s the reason, but give it a google, you’ll find your answer.

I’m using Shimano now for various reasons, but the Guide Rs are good brakes.

Tone C

Yea, i thought that was the case, that's why I said about the Shimano braked bikes being fine. Hopefully it'll be fine come the morning. I have a set of SLX brakes I bought as an upgrade for one of the hardtails but then bought another bike (the Boardman) so I didn't bother fitting them as I used the Boardman the most and was happy with the brakes on that. I suspect the SLX will end up on the Boardman shortly.

figbat

I had this on some old Hayes disc brakes - I bled a drop of fluid from them and never had another problem. Maybe worth replacing the fluid anyway if it is getting on.

billycool

Might be worth a bleed and check fluid levels.

I've got SLX on my HT and think they're are really good for the money and just as good as my XT (M8000). I actually seem to get better modulation with the SLX as the XT seem more senisitve to bleeding and are slightly harder to set up.

JBA

I had two bikes with Avid/SRAM brakes and although they worked well and had a great feel both sets suffered from lock on during hot weather.
Bleed a couple of drops of fluid from the levers and you’ll be sorted. (Take care not to get dot brake fluid on your paintwork.)
The next problem you’ll exoerience if you do this is excessive brake lever travel when the weather cools down again!

All the bikes in my family now have Shimano brakes fitted.

jamski

BillyCool wrote:

Might be worth a bleed and check fluid levels.

I've got SLX on my HT and think they're are really good for the money and just as good as my XT (M8000). I actually seem to get better modulation with the SLX as the XT seem more senisitve to bleeding and are slightly harder to set up.

I was going to spec M7000 SLX brakes, but Bird recommended to just go for the M6000 Deores and put the money elsewhere The saving bought me an rt3 shock, and the brakes have been great. Have put Uberbike finned pads in now too, they're great!

Tone C

Cheers folks. Didn't get the ride in anyway, brakes freed up as it cooled down last night/this morning but although the front brake went pretty much back to normal albeit a tad spongy the rear lever was an issue- it was released as normal but a movement of about a millimetre or two caused the rear to lock full on. Not as much an issue as the front doing that I know but there was no control over it- either off or hard on (he he he). Will probably swap the brakes over for those SLX ones...

billycool

jamski wrote:

BillyCool wrote:

Might be worth a bleed and check fluid levels.

I've got SLX on my HT and think they're are really good for the money and just as good as my XT (M8000). I actually seem to get better modulation with the SLX as the XT seem more senisitve to bleeding and are slightly harder to set up.

I was going to spec M7000 SLX brakes, but Bird recommended to just go for the M6000 Deores and put the money elsewhere The saving bought me an rt3 shock, and the brakes have been great. Have put Uberbike finned pads in now too, they're great!

A very good idea. I think Shimano brakes are pretty good across the board.

I used to have Avid Juicy 5's and they were good until they needed some TLC and got a bit tired. Changing pads was hard work and bleeding was an art form. I think Avid make some good brakes so I'm not `anti`, but just comfortable with Shimano as they work for me and it's easier having the same brakes on my bikes.

I don't really need finned pads. Do you run sintered or resin - or both? I use sintered F&R but thinking about trying resin on the front. I'm F 180 and R 160 as that's all I need. Not much of a DH rider.

billycool

BillyCool wrote:

jamski wrote:

BillyCool wrote:

Might be worth a bleed and check fluid levels.

I've got SLX on my HT and think they're are really good for the money and just as good as my XT (M8000). I actually seem to get better modulation with the SLX as the XT seem more senisitve to bleeding and are slightly harder to set up.

I was going to spec M7000 SLX brakes, but Bird recommended to just go for the M6000 Deores and put the money elsewhere The saving bought me an rt3 shock, and the brakes have been great. Have put Uberbike finned pads in now too, they're great!

A very good idea. I think Shimano brakes are pretty good across the board.

I used to have Avid Juicy 5's and they were good until they needed some TLC and got a bit tired. Changing pads was hard work and bleeding was an art form. I think Avid make some good brakes so I'm not `anti`, but just comfortable with Shimano as they work for me and it's easier having the same brakes on my bikes (I did change to the SLX from the J5's as I'd lost the will to live - I can now change pads in under 2 minutes).

I don't really need finned pads. Do you run sintered or resin - or both? I use sintered F&R but thinking about trying resin on the front. I'm F 180 and R 160 as that's all I need. Not much of a DH rider.

02gf74

Yes it also happens if bike has not been used for a while, affects formula, avid and sram but never had this with shimano.

figbat

I suspect it is moisture absorption rather than thermal expansion, although mine was also kept in a hot environment when it happened, so maybe a combination of effects.

The Rookie

Where does the moisture get in?