Author Topic: XTR internal spring not springing?  (Read 1251 times)

Matt2matt2002

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XTR internal spring not springing?
« on: July 31, 2016, 08:15:28 PM »
While way on tour I noticed my front XTR brake not retracting fully on the right side, where the cable connects.
While riding I could reach down and nudge one side so that the pads didn't rub.

Today I removed the front wheel and took a good look at the set up.
I dusted it down and then used a tooth brush and soapy water to clean things up.

The none brake cable side definitely sprung back fully and easily. I presume this is the function of the small ' internal' coiled spring?
The other side did not retract and return to the same degree. I could see why one side would be rubbing.

I then removed both brakes from their spindles and oiled the moving hinges/ moving parts. I also greased the spindles before replacing the brakes.
On inspection the coiled springs looked OK but can these fail or loose their tension?
Both were hooked up fine.

Reassembled I still had the same/ original problem. On releasing the brake lever, one pad still rubs the rim.
I can see it not retracting. So I don't think it's an untrue wheel rim.

Any thoughts folks?

Matt
Never drink and drive. You may hit a bump  and spill your drink

Danneaux

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Re: XTR internal spring not springing?
« Reply #1 on: July 31, 2016, 08:22:31 PM »
My guess...

While  your bike was in transport with the front wheel out -- and the box being dragged along the tarmac with enough force to bend your forks(!) -- something probably pressed in on that one brake arm enough to deform the spring, causing it to ride closer to the rim.

Yes, the linear springs on v-brakes are quite elastic and can be bent in this way. I have yet to receive a pair from the Shimano factory with equal spring tension and set mine up with the spring-tension adjusting screws backed out equally, then set the tension by bending the springs lightly. I once ran into a Shimano rep at a MTB race and he confirmed this was his own preferred method for initial setup.

The springs are not coils in the strictest sense, more like one coil and the rest laid out in a line. Simply use a fingernail to unhook the end from the peg that holds it, then pull gently out a bit under tension, then rehook it under its mount and try again. Normal function should be restored quickly. If not, you can try again. The tension-adjustment screws that bear on the lower spring ends can be used for fine adjustment.

Hope this helps.

All the best,

Dan.

Matt2matt2002

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Re: XTR internal spring not springing?
« Reply #2 on: July 31, 2016, 08:57:00 PM »
Thanks Dan.
Bedtime here in UK but will try your suggestions tomorrow

Matt
Never drink and drive. You may hit a bump  and spill your drink

mickeg

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Re: XTR internal spring not springing?
« Reply #3 on: July 31, 2016, 10:43:35 PM »
... The tension-adjustment screws that bear on the lower spring ends can be used for fine adjustment.
...

I would start with the screws as that may be all the adjustment you need.  If the screws can't do the adjustment, then try bending the springs.

The screws thread in to tighten the springs, thus tighten the screw on the side with the rubbing pad first, the tighter spring then pushes the pad out further. 

If that is insufficient, you may need to loosen the screw on the other side.  I am assuming both sides of the brake have the screws, some cheaper models have only one screw on one side.

I find that I am adjusting these little screws more often than any other adjustment on my bike.  I think that V brakes are more sensitive to adjustment than cantilever brakes.

Bill C

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Re: XTR internal spring not springing?
« Reply #4 on: August 01, 2016, 04:53:55 PM »
Rather than bend the spring I would try the spring in the upper of the three holes on the brake boss on the arm that's sluggish, that will increase the tension on that arm

geocycle

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Re: XTR internal spring not springing?
« Reply #5 on: August 01, 2016, 05:16:07 PM »
Rather than bend the spring I would try the spring in the upper of the three holes on the brake boss on the arm that's sluggish, that will increase the tension on that arm

Good idea, and make sure the pivot is well lubricated.
 

Danneaux

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Re: XTR internal spring not springing?
« Reply #6 on: August 01, 2016, 05:29:00 PM »
Quote
Rather than bend the spring I would try the spring in the upper of the three holes on the brake boss on the arm that's sluggish, that will increase the tension on that arm
It surely will and is functional, but the brakes will end up with a base tension that is unequal.

I've surely been disappointed to find *all* my new Shimano v-brakes came from the factory with such wildly varying spring tension, which headed me in the direction of gentle spring-bending. Once the spring tension was equalized, they've stayed nicely centered ever since. With the linear springs, it takes surprisingly little -- and gentle! -- force on the ends (after unhooking from their perches) to equalize the tension over their length.

If you do this, be mindful to use a thumb and forefinger, so the bending forces don't impinge on the base plastic covers.

All the best,

Dan.
« Last Edit: August 01, 2016, 05:36:16 PM by Danneaux »

Danneaux

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Re: XTR internal spring not springing?
« Reply #7 on: August 01, 2016, 06:01:40 PM »
Ah! I see from personal correspondence, we are talking about different springs, Matt. Your problem is not with the linear springs, so my advice does not apply.

All the best,

Dan.

Matt2matt2002

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Re: XTR internal spring not springing?
« Reply #8 on: August 01, 2016, 06:48:06 PM »
Thanks Dan.
Linear spring. The long ' straight ' thin one?

What is the other one called?
This is the one that concerns me.
Is it removable/ adjustable?
One is definitely weaker than the other.
Matt
Never drink and drive. You may hit a bump  and spill your drink

Bill C

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Re: XTR internal spring not springing?
« Reply #9 on: August 01, 2016, 07:27:16 PM »
Pretty sure there is only one spring in a v brake arm and it looks like this
http://www.ilovebike.it/en/parts-brake/spring-brake-v-brake-right-left/

Try the top hole as I said earlier

Matt2matt2002

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Re: XTR internal spring not springing?
« Reply #10 on: August 01, 2016, 07:52:08 PM »
Thanks Bill.
I know the one your link shows but I appear to have another one.

I'll post pix asap tomoz
Matt
Never drink and drive. You may hit a bump  and spill your drink

JimK

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Re: XTR internal spring not springing?
« Reply #11 on: August 01, 2016, 11:38:02 PM »
XTRs are odd brakes. Hard to photograph, too - really needs manual focus, which my camera does have, if I could just remember which knobs... Anyway, maybe this is the spring of concern:

mickeg

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Re: XTR internal spring not springing?
« Reply #12 on: August 02, 2016, 12:36:43 AM »
I previously suggested starting with the spring adjustment screws.  Without being there to see why that is not the best option, my advice is the same as before.

They have lots of models, not sure which you have.
http://si.shimano.com/php/download.php?file=pdf/ev/EV-BR-M960-2141.pdf

JimK

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Re: XTR internal spring not springing?
« Reply #13 on: August 02, 2016, 01:36:39 AM »
seems I have the m970 which sure looks like the m960! No idea what Matt has. For sure with my brakes, the adjustment screws have always handled what imbalance has arisen.

JimK

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Re: XTR internal spring not springing?
« Reply #14 on: August 02, 2016, 01:39:27 AM »
here somebody says the 960 and 970 are mechanically identical: http://forums.mtbr.com/brake-time/difference-between-shimano-xtr-br-m960-br-m970-998583.html