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Discussion Starter · #1 ·
Hi dudes

Not a happy chappy tonight:mad: .

I have been tuning my brakes. New 08 XTs. The pads are ok plenty of material left.

I was finding the levers far too spongy and they were coming back to nearly touch the bars. To firm them up, I followed advice of a bike mechanic friend and with the reservoir on the lever closed, I pumped and extra few ml (about 3ml) of oil into the caliper (ensuring no air).

Yes the lever is firmer, but oil leaked from the reservoir seal. Is this because I put too much pressure to the seal? I was applying only gentle pressure to the syringe to get the oil in.

This is worrying me and I'd love some feedback. How much is too much. How can you tell? What is the best and most effective way to firm up the levers.

I have done a bleed per the Shimano instructions already and am fairly confident that it went very well. I had to bled the front anyway as I popped a piston out earlier trying to correct a sticky one. Its not my night:madman: :madman: . The problem re firmness was there before the pop issue though

I love the power of my brakes but miss the easy tune of V's! Don't miss V's in the wet and mud though.

Thanks very much for your help. Please fire away!

Davo
 

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you shouldn't need to overfill the system to get a good lever feel....

a usually overlooked detail is alignment, assuring that both pistons are moving similar amounts... this has a huge effect on how the brake feels at the lever...

sponginess has one clear cause: air in the system
 

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Discussion Starter · #3 ·
Good points. Thanks. Alignment has been tricky. I always seem to have one piston (inboard) pushed out way further than the outside piston, despite seeming to have the caliper aligned right. I wonder if it is sticky? The piston which is 'over extended' is also dragging on the disc.

Mmmm. thoughts?
 

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to equalize the pistons, first clean the outside of the sticky piston and lube it with mineral oil, to make sure it moves freely (you can hold the other piston with a plastic tire lever,and pump the lever a tiny bit to help the sticky one come out a bit and then push it back, a couple of times)


also when aligning them, you can hold back the piston that comes out more with a feeler gauge...or with a business card to give the other piston a chance to come out the same amount...
 

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Also consider that both pistons aren't supposed to come out equal distances. The side with the hose will most always move farther than the opposite side. At least this is according to my lbs. But sticky pistons can still limit the movement alot more than it is supposed to.
 

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Big Wave Dave said:
Hi dudes

Not a happy chappy tonight:mad: .

I have been tuning my brakes. New 08 XTs. The pads are ok plenty of material left.

I was finding the levers far too spongy and they were coming back to nearly touch the bars. To firm them up, I followed advice of a bike mechanic friend and with the reservoir on the lever closed, I pumped and extra few ml (about 3ml) of oil into the caliper (ensuring no air).

Yes the lever is firmer, but oil leaked from the reservoir seal. Is this because I put too much pressure to the seal? I was applying only gentle pressure to the syringe to get the oil in.

This is worrying me and I'd love some feedback. How much is too much. How can you tell? What is the best and most effective way to firm up the levers.

I have done a bleed per the Shimano instructions already and am fairly confident that it went very well. I had to bled the front anyway as I popped a piston out earlier trying to correct a sticky one. Its not my night:madman: :madman: . The problem re firmness was there before the pop issue though

I love the power of my brakes but miss the easy tune of V's! Don't miss V's in the wet and mud though.

Thanks very much for your help. Please fire away!

Davo
Same thing happened to me when I did that. No problems since. You just overcame the pressure the cover is tightened at.

also, alignment is critical. I had to dremel the holes on the back caliper to get the lateral alignment centered. Not much, maybe half ao milimeter.

They have been fantastic brakes, once properly set up.
 

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Discussion Starter · #8 ·
Mmmm.

All good points. Thanks folks.

I think I could achieve better alingment if I fiddle the mounts or holes. I might try it over the weekend. No power atall in the front this morning. A mixture of a poor bleed (?) and maybe oil on thr pads or rotor. Its not my week.

D
 
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