Shimano bleed block mods?

[dunndog]

This isn't a new issue, but bled brakes again yesterday and it reminded me to ask.
Using a bleed block on my XT's and always get a really firm crisp result. However, once pads are installed and they clamp down onto a rotor, that same feeling isn't maintained. I'm considering sanding a block down so it's not so wide, so there's not as much difference in width of calliper spacing between the bleed block and the real world. Is this going to work or is there a reason it won't?

 

[Markee]

Maybe try adding a little more fluid to the reservoir after the pads are sitting up against the disc, I've found that this helps retain that feeling you get when they're freshly done with the bleed block.
Just remember that if you do change your pads(because they're worn out) that it would be better to flush the fluid and start again with the bleed block due to the reservoir being so small and if you try to push the piston back with the lid on the reservoir there won't be enough room for the fluid.

 

[dunndog]

Reservoirs were full to the point of a drop or 2 being squeezed out when I fitted the caps back on.. i feel like to get more in I need the pistons to not be fully retracted. The issue then potentially becomes, does this not allow any room for heat expansion and potentially causing the levers to stiffen up?
I don't really know enough about it, but it doesn't seem like rocket surgery. Think I'll shave the blocks down and give it a go anyway as it's almost always the same result as they are..

 

[moorey]

Blocks seem to assume you're fitting new pads while bleeding....being shimano, it's a silly assumption.
Can't you carefully bleed with current pads in? I regularly do it....and occasionally don't get oil all over the calipers, pads and rotors :woot:

 

[dunndog]

Ha yeah that was my initial thought, but I've got so many bleed blocks I figure why risk the pads, I'll just shave a block down.. you're right though, they must be assuming new pads every time. Those finned pads are too expensive to sacrifice before they're totally spent!

 

[schred]

I thought the block width was to ensure pistons are fully retracted that ensures the caliper is bled properly. I wouldnt shave them down.

Note that when you are bleeding against blocks there's almost zero piston movement so system builds pressure in the line quickly, feels great at the lever.

But thats not how it is in practice when you first squeeze the lever, the pistons have to move a bit, otherwise it would be like riding around with pads hard up against the rotor all the time.

May as well ask, how true is the rotor?

 

[stirk]

You could advance the pistons a little with the pads out but you'll lose that shorter bite point as the pads wear.

Just enjoy shimano's 'modulation'

 

[schred]

Afaik they're self adjusting for pad wear, piston seals are designed so that pistons retract a certain amount when lever is released. If they dont it means something is up. And not sure how long lasting any workarounds would be.

I mentioned the rotors as they can knock pads back and can make lever feel less firm/direct.

 

[stirk]

Yep but the self adjust is fixed by the lever mechanism hence it will go back to normal as the pads wear.

 

[Staunch]

I've got a shaved down bleed block I use for bleeding my brakes when the pads are half worn but not worth replacing yet. The results are better than using the stock bleed block, I'd recommend it. After all, bleed blocks are worth nothing so shaving one down and just giving it a crack isn't going to break the bank or anything.

Basically it just allows you to bleed the system so that the pistons aren't fully retracted (as they usually would be) when the lever isn't engaged, hence shortening the distance between pad and rotor to compensate for the partially worn pads.

 

[wkkie]

This is basically what you're after, they advocate a pads in bleed..... http://www.epicbleedsolutions.com/blog/5-minute-shimano-mini-bleed/

 

[redbruce]

I thought the block width was to ensure pistons are fully retracted that ensures the caliper is bled properly. I wouldnt shave them down.

Note that when you are bleeding against blocks there's almost zero piston movement so system builds pressure in the line quickly, feels great at the lever.

But thats not how it is in practice when you first squeeze the lever, the pistons have to move a bit, otherwise it would be like riding around with pads hard up against the rotor all the time.

This is correct. The idea is to minimise the volume of brake fluid in the caliper to ensure a more effective bleed (puts most fluid in one area and less areas for gas to be trapped).

Having said that I have had the same result using the mini bleed method advocated by Epicbleedsolutions.

It did result in over filling at the next pad change and took a bit longer to get all the gas out, but then it was on Avids.

 

[dunndog]

Great link, this is a glorified version of what Markee suggested earlier, which I've done. Got an extra few drops into the reso with the pads in and it's added a nice amount of firmness. Pretty happy with that.