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2008 XT brakes, the cold, and you...

-dustin

boring
Jun 10, 2002
7,165
1
austin
It was 23 this morning, windchill in the teens. My XT hydros are weeks old. Drove to the trail. Squeezed the lever...

Felt as though someone had just overloaded my lines with air. Pistons weren't retracting, lever very, very little throw, pads rubbing. Figured the cold...you know, ride it, and the brakes will warm up. Did 2 laps at a local trail and nothing. Still were feeling like ass. I thought the mineral oil I used was bad. Shimano stuff that we have at the shop...nothing crazy. Initially I'm like, "****, man...I just bled a guys brakes, and installed another set of XTs on a new bike. Did I **** up their brakes?"

Get to the shop, call Shimano.

Shimano says it's an issue they are aware of, and that the engineers are working on it. Happens in the cold, especially when transported on a rack outside of the car. I was told it is an issue involving their other lines. As of now, I have no answer as to why my brakes feel like crap.

What the ****? Why not correct the issue before releasing more brakes?

I let my bike sit inside the rest of the day at work. Spread the pistons, and all felt good. Loaded it up on the back of the truck and drove home (10min drive). Again, the pistons won't retract, and my lever has no throw.
 

blue

boob hater
Jan 24, 2004
10,165
0
california
My older XTs (the first Hydros after the Grimeca clones) did the same...felt craptastic in single-digit weather.
 

Jim Mac

MAKE ENDURO GREAT AGAIN
May 21, 2004
6,364
281
the middle east of NY
Thats Interesting , I have use my Shimano hydro Deore's In 10 degree weather and had no issues. Later this week when we get really cold , I'll have to see how my XTR's on my AC1 react
Ditto on that with my '02 Deore discs on my trail bike, hooray for cheap disc brakes!
 

-dustin

boring
Jun 10, 2002
7,165
1
austin
might have something to do with the fact that those temps are outside the normal operating conditions for the brakes.....
Coming from you, I'll accept that answer. However, that brings up the following question:

Being such a simple answer, why didn't the tech guy tell me this on the phone? Rhetorical...don't expect you to have an answer for that.

I told him what the temp was this morning, as I thought that was the issue. He mentioned a spring (can't remember exactly where, just remember him saying something about a spring).
 

DirtyMike

Turbo Fluffer
Aug 8, 2005
14,217
807
My own world inside my head
Maybe it has something to do with the properties of the type of fluid used in shimano brakes, and maybe you have some moisture built up in the fluid, being a mineral oil, it wont absorb into the fluid. Just a thought when thinking about teh properties of mineral oil vs a glycol fluid.
 

-dustin

boring
Jun 10, 2002
7,165
1
austin
Were moisture built up in the system, it seems as though I would notice it (spongy feeling in the brake) when functioning properly. I did consider that, though, and before talking to Shimano, it was what I considered to be the most probable cause.
 
the only spring i know of in a hydraulic system is in the master cylinder to push it back out and return the lever to its normal state. Now I don;t know for the reason you were having issues, but this would be my educated guess:

As a fluid gets colder it becomes thicker, denser, and harder to move, basically becomes more (or less not entirely sure of the correct way) viscous. Because the fluid is now this thicker mass that the spring, as well as the seals in the caliper are trying to move becomes harder. And, because of this the combined effort of that spring, and the seals in the caliper that hold the pistons, is not enough to retract the pistons. Hence, why when you warm it up it moves fine. I don't think it has anything to do with moisture in the system, a truly faulty system, or anything like that. I think it is just the general properties of mineral oil in the cold, and the brake not having a spring and seals that are strong enough to overcome the added difficulty of moving the thicker fluid through the small holes that it needs to. Brakes are designed to withstand heat buildup from heavy braking, I doubt many are designed to do this while also starting from an intense cold. I am sure if you were able to heat this system up over a long DH run to a more normal temperature that you would not notice any difference.

Again, this is just an educated guess from basic knowledge of fluids, and the hydraulic brake systems. But, seems like a reasonable answer to me.

As for the Tech at Shimano, curious they didn't think of this or you may have just caught them before their morning coffee. They tend to be highly intelligent guys working there, although there are a couple based on the BMX side of things and therefore may not understand the hydraulic brakes as well.
 

Westy

the teste
Nov 22, 2002
36,388
3,147
Sleazattle
My guess is that there are different metal types in the levers or calipers. When it gets cold they shrink at different rates causing too tight of a fit somewhere.
 

Mike B.

Turbo Monkey
Oct 5, 2001
1,522
0
State College, PA
All my Maguras with mineral function fine in the cold but it's possible the Shimano system is not as tolerant to increased viscosity as Zman was alluding to.
 
All my Maguras with mineral function fine in the cold but it's possible the Shimano system is not as tolerant to increased viscosity as Zman was alluding to.
I can't imagine a design difference which would react differently to viscosity variation with temperature. I had Maguras for quite a while and experienced no problems - I think mineral oil is not the culprit.

Water in the system could be another issue indeed if it were to freeze...
 

loco-gringo

Crusading Clamp Monkey
Sep 27, 2006
8,887
5
Deep in the heart of TEXAS
I can't imagine a design difference which would react differently to viscosity variation with temperature. I had Maguras for quite a while and experienced no problems - I think mineral oil is not the culprit.

Water in the system could be another issue indeed if it were to freeze...
It would depend on the oil as to whether that was the case. Different manufacturer's oil viscosity could change due to cold. Line thickness could also play a part. Water could be an issue, but that would likely be due to the maker's oil as well.

There is absolutely nothing else that should effect things, other than grease in a lever pivot, which should not be the case.
 

Nobody

Danforth Kitchen Whore
Sep 5, 2001
1,492
0
Toronto
I think one thing to look at is the 'super-cooled' effect of driving at resonably high speeds in cold air.

I mean, what was the relative temperature from the roof-rack ride?
 

-dustin

boring
Jun 10, 2002
7,165
1
austin
Bled brakes with new, sealed Shimano fluid, clean syringe, and clean little tube thing. Happened again today. Called Shimano and am sending them the brakes. They're going to bleed them and send them back.

I'm going to sell them.

Marta SLs are now on my bike.
 

Prettym1k3

Turbo Monkey
Aug 21, 2006
2,867
0
In your pants
Why not correct the issue on the 2-Step before releasing the Totems and Lyrics?

Because the market has a demand, and it's better to listen to some pissing and moaning, then listen to people bitch about not releasing stuff on time.
 

Smelly

Turbo Monkey
Jun 17, 2004
1,255
1
out yonder, round bout a hootinany
Bled brakes with new, sealed Shimano fluid, clean syringe, and clean little tube thing. Happened again today. Called Shimano and am sending them the brakes. They're going to bleed them and send them back.

I'm going to sell them.

Marta SLs are now on my bike.

A riding buddy had the same problem, and after 6 months of pissing around with them, he came upon the same solution.