Mountain Biking - XT disc Question

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View Full Version : XT disc Question


Wilson10
01-19-04, 03:23 PM
How do I lube my pistons? Only one side seems to be operating properly.


KleinMp99
01-19-04, 03:37 PM
How do I lube my pistons? Only one side seems to be operating properly.


I believe the mineral oil is supposed to lubricate them.

Jim311
01-19-04, 07:01 PM
I saw some XT discs at an online retailer for 65 bucks!! I was so close to snatching them up even though they are a Shimano product.


sscyco
01-19-04, 08:41 PM
I saw some XT discs at an online retailer for 65 bucks!! I was so close to snatching them up even though they are a Shimano product.
Where?

Jim311
01-19-04, 08:59 PM
At pricepoint:

http://www.pricepoint.com/detail.htm?stylepkey=11314&style_id=115%20SHIMD1&dept_id=3&deptName=Parts&sub_id=46&subName=Brakes/Accessories%20&lprice=64.98&hprice=64.98&detailName=Shimano%20XT%20Disc%20Brake%20M755%20-%20%20Front

Jim311
01-19-04, 09:05 PM
They only have the front brake on sale for 65, and it doesn't include a hose. But I'm sure you can find the rear XT disc brake for 100 bucks or less somewhere online.

a2psyklnut
01-20-04, 10:00 AM
DON'T LUBRICATE THE PISTONS!

You'll contaminate the pads and render your brakes useless!

The DOT or Mineral Oil does in fact lubricate as it works.

With many disc brakes, only one side moves anyways. The outside piston is the one that moves, The inside one is fixed and the outside piston pushes the rotor in toward the fixed one.

Wilson10
01-20-04, 10:02 AM
Ok, but in my case the inside pistons on the inside are the ones moving. thoughts? should i just leave it be

a2psyklnut
01-20-04, 10:12 AM
Front brake?

Probably, I was thinking (picturing in my head) my rear Hayes brake. Anyways, only one moves!

I'd just leave it.

If you're having problems with stopping power, I'd first replace the pads. I use EBC Gold pads and it completely improved my braking performance.

L8R

SS_MB-7
01-20-04, 11:47 AM
How do I lube my pistons? Only one side seems to be operating properly.

I have XTR discs and have sticky pistons in both the front and rear calipers. Mine are now back at Shimano for warranty. This is a known issue with some of the XTR calipers in which the inner piston bore surface is too smooth for the piston seals to grab the surface. Newer version have slightly rougher surfaces.

I tried everything to get my pistons to work, but ultimately, it was just a waste of time.

Curiously, I spoke with both Shimano USA and Shimano Canada. Shimano USA said to lube the pistons, but didn't specify what lube. This was also written-up on Velonews.com. However, Shimano Canada advised against lubing since it will attract dirt. But, they did say, if you are going to lube, use Shimano Mineral Oil, which is in the system, and not TriFlow, etc. So, if you do lube, make sure you clean-up any excess. Shimano Canada also recommended thoroughly cleaning the pistons with White Lightening Clean Streak.

Ride Hard,
Mike B.
http://www.one-speed.com

SS_MB-7
01-20-04, 11:50 AM
DON'T LUBRICATE THE PISTONS!

You'll contaminate the pads and render your brakes useless!

The DOT or Mineral Oil does in fact lubricate as it works.

With many disc brakes, only one side moves anyways. The outside piston is the one that moves, The inside one is fixed and the outside piston pushes the rotor in toward the fixed one.

Depends who you talk to...Shimano USA or Canada. USA says to lube the pistons, but Canada advises against it.

Yes, if you aren't careful, you can get fluid on your pads when lubing the pistons. So, I'd recommend removing the wheel and pads and then gently extending the pistons by gently pulling the lever. Don't pull too hard, too fast or too hard because the pistons can pop-out.

Actually, very few, if any, are single-piston. Most brakes are now dual piston. The older Magura Louise were single-piston, but are now dual.

Ride Hard,
Mike B.
http://www.one-speed.com