XTR disk brake inconsistencies

Hello usenet,

I've had a set of XTR disk brakes (newer M975) for a season now and
have had a re-occurring scenario which I'm not sure is normal. Today
was probably the most pronounced experience, hence why I'm asking this
newsgroup. Here's the scoop:

I hadn't ridden the bike in a few days and when I started, the brakes
were very soft (lots of lever pull). Over the course of an extended
downhill (mile or two) with hard braking, they gradually stiffened to
where at the end there was very little lever pull. After driving
home, eating dinner, etc I just took the bike off the car and lo and
behold, the brakes are feeling very soft again.

I first noticed it this summer but it wasn't quite as pronounced. I
would start and end the ride with the lever pull "just right", but
under extended braking found that they became more and more "stiff".

There are no visible leaks in the system anywhere. Is this a bleed
issue? If so, why do they stiffen up?

Thanks in advance for anyone's help.

"Barry" wrote in message
...
Hello usenet,

I've had a set of XTR disk brakes (newer M975) for a season now and
have had a re-occurring scenario which I'm not sure is normal. Today
was probably the most pronounced experience, hence why I'm asking this
newsgroup. Here's the scoop:

I hadn't ridden the bike in a few days and when I started, the brakes
were very soft (lots of lever pull). Over the course of an extended
downhill (mile or two) with hard braking, they gradually stiffened to
where at the end there was very little lever pull. After driving
home, eating dinner, etc I just took the bike off the car and lo and
behold, the brakes are feeling very soft again.

I first noticed it this summer but it wasn't quite as pronounced. I
would start and end the ride with the lever pull "just right", but
under extended braking found that they became more and more "stiff".

There are no visible leaks in the system anywhere. Is this a bleed
issue? If so, why do they stiffen up?

Thanks in advance for anyone's help.


Sounds like is a closed type hydraulic setup. When it heats up you
experience what you've written. They stiffen up becuase the system gets hot
and the oil expands, in a closed system, there is no where for the extra
pressure to go so it stiffens up the lever. Open systems have a bladder to
cover for this and dont change the feel of the lever hot or cold.

I was under the impression that most if not all newer type hydro discs were
all open systems??!?!? weird...

Cheers Dre

On 16 Pa¼, 04:01, Barry wrote:
Hello usenet,
snip
Thanks in advance for anyone's help.

Bleed - there is air in the system.

Regards
--
Adam Kadlubek

On 16 okt, 04:19, "Dre" wrote:
"Barry" wrote in message

...





Hello usenet,

I've had a set of XTR disk brakes (newer M975) for a season now and
have had a re-occurring scenario which I'm not sure is normal. *Today
was probably the most pronounced experience, hence why I'm asking this
newsgroup. *Here's the scoop:

I hadn't ridden the bike in a few days and when I started, the brakes
were very soft (lots of lever pull). *Over the course of an extended
downhill (mile or two) with hard braking, they gradually stiffened to
where at the end there was very little lever pull. *After driving
home, eating dinner, etc I just took the bike off the car and lo and
behold, the brakes are feeling very soft again.

I first noticed it this summer but it wasn't quite as pronounced. *I
would start and end the ride with the lever pull "just right", but
under extended braking found that they became more and more "stiff".

There are no visible leaks in the system anywhere. *Is this a bleed
issue? *If so, why do they stiffen up?

Thanks in advance for anyone's help.

Sounds like is a closed type hydraulic setup. *When it heats up you
experience what you've written. *They stiffen up becuase the system gets hot
and the oil expands, in a closed system, there is no where for the extra
pressure to go so it stiffens up the lever. *Open systems have a bladder to
cover for this and dont change the feel of the lever hot or cold.

I was under the impression that most if not all newer type hydro discs were
all open systems??!?!? *weird...

Cheers Dre- Tekst uit oorspronkelijk bericht niet weergeven -

- Tekst uit oorspronkelijk bericht weergeven -

XTR is not of the closed kind. There is air in the system. Bleed.

Lou

On Oct 16, 2:58*am, Adam Kadlubek wrote:
On 16 Pa¼, 04:01, Barry wrote:

Hello usenet,
snip
Thanks in advance for anyone's help.

Bleed - there is air in the system.

Regards
--
Adam Kadlubek

Is this normal for air to gradually be introduced to the system? I
only expected bleeding to be necessary after brake pad/fluid changes,
etc. V-brakes sure were a lot simpler!
Thanks everyone,
Barry

On Oct 16, 7:20*am, Barry wrote:
On Oct 16, 2:58*am, Adam Kadlubek wrote:

On 16 Pa¼, 04:01, Barry wrote:

Hello usenet,
snip
Thanks in advance for anyone's help.

Bleed - there is air in the system.

Regards
--
Adam Kadlubek

Is this normal for air to gradually be introduced to the system? *I
only expected bleeding to be necessary after brake pad/fluid changes,
etc. *V-brakes sure were a lot simpler!
Thanks everyone,
Barry

Do you store the bike upside down or on its side at all? My MTB with
hydraulic disk brakes loses its brake pressure when upside down or
certain positions on its side. Storing it upright as I started doing
eliminated the problem with lack of pressure when starting a ride -
but that wouldn't be a likely cause of stiffening when right at the
start. So look at a bleed as suggested but if the position applies,
consider that also.

Rick

On Oct 15, 7:01*pm, Barry wrote:
Hello usenet,

I've had a set of XTR disk brakes (newer M975) for a season now and
have had a re-occurring scenario which I'm not sure is normal. *Today
was probably the most pronounced experience, hence why I'm asking this
newsgroup. *Here's the scoop:

I hadn't ridden the bike in a few days and when I started, the brakes
were very soft (lots of lever pull). *Over the course of an extended
downhill (mile or two) with hard braking, they gradually stiffened to
where at the end there was very little lever pull. *After driving
home, eating dinner, etc I just took the bike off the car and lo and
behold, the brakes are feeling very soft again.

I first noticed it this summer but it wasn't quite as pronounced. *I
would start and end the ride with the lever pull "just right", but
under extended braking found that they became more and more "stiff".

There are no visible leaks in the system anywhere. *Is this a bleed
issue? *If so, why do they stiffen up?

Thanks in advance for anyone's help.

You can check to see if you need to bleed by "pumping" the brakes up
after it's been sitting awhile.
Simply work the brakes a dozen or so times, bottoming out the lever as
far as you can.
If this helps, you definitely need to bleed them!

-pete

wrote in message
...
On 16 okt, 04:19, "Dre" wrote:
"Barry" wrote in message

...





Hello usenet,

I've had a set of XTR disk brakes (newer M975) for a season now and
have had a re-occurring scenario which I'm not sure is normal. Today
was probably the most pronounced experience, hence why I'm asking this
newsgroup. Here's the scoop:

I hadn't ridden the bike in a few days and when I started, the brakes
were very soft (lots of lever pull). Over the course of an extended
downhill (mile or two) with hard braking, they gradually stiffened to
where at the end there was very little lever pull. After driving
home, eating dinner, etc I just took the bike off the car and lo and
behold, the brakes are feeling very soft again.

I first noticed it this summer but it wasn't quite as pronounced. I
would start and end the ride with the lever pull "just right", but
under extended braking found that they became more and more "stiff".

There are no visible leaks in the system anywhere. Is this a bleed
issue? If so, why do they stiffen up?

Thanks in advance for anyone's help.

Sounds like is a closed type hydraulic setup. When it heats up you
experience what you've written. They stiffen up becuase the system gets
hot
and the oil expands, in a closed system, there is no where for the extra
pressure to go so it stiffens up the lever. Open systems have a bladder to
cover for this and dont change the feel of the lever hot or cold.

I was under the impression that most if not all newer type hydro discs
were
all open systems??!?!? weird...

Cheers Dre- Tekst uit oorspronkelijk bericht niet weergeven -

- Tekst uit oorspronkelijk bericht weergeven -

XTR is not of the closed kind. There is air in the system. Bleed.

Lou

Thanks for the heads up. I thought it was weird to hear of a closed type
system these days...

Cheers Dre

Dre wrote:
wrote in message
...
On 16 okt, 04:19, "Dre" wrote:
"Barry" wrote in message

...





Hello usenet,
I've had a set of XTR disk brakes (newer M975) for a season now and
have had a re-occurring scenario which I'm not sure is normal. Today
was probably the most pronounced experience, hence why I'm asking this
newsgroup. Here's the scoop:
I hadn't ridden the bike in a few days and when I started, the brakes
were very soft (lots of lever pull). Over the course of an extended
downhill (mile or two) with hard braking, they gradually stiffened to
where at the end there was very little lever pull. After driving
home, eating dinner, etc I just took the bike off the car and lo and
behold, the brakes are feeling very soft again.
I first noticed it this summer but it wasn't quite as pronounced. I
would start and end the ride with the lever pull "just right", but
under extended braking found that they became more and more "stiff".
There are no visible leaks in the system anywhere. Is this a bleed
issue? If so, why do they stiffen up?
Thanks in advance for anyone's help.
Sounds like is a closed type hydraulic setup. When it heats up you
experience what you've written. They stiffen up becuase the system gets
hot
and the oil expands, in a closed system, there is no where for the extra
pressure to go so it stiffens up the lever. Open systems have a bladder to
cover for this and dont change the feel of the lever hot or cold.

I was under the impression that most if not all newer type hydro discs
were
all open systems??!?!? weird...

Cheers Dre- Tekst uit oorspronkelijk bericht niet weergeven -

- Tekst uit oorspronkelijk bericht weergeven -

XTR is not of the closed kind. There is air in the system. Bleed.

Lou

Thanks for the heads up. I thought it was weird to hear of a closed type
system these days...

Cheers Dre



it's not normally closed - it sounds like you have the adjusters set so
the return valve is occluded. back off the piston adjusting screws a
bit and you should be fine. air doesn't cause the symptoms described.