Brake Caliper Alignment

[Husky430]

Have just had something get stuck in my calipers and pulled it all apart to get it out. Once I had it apart, and with the wheel removed, I noticed that the pistons (4 pot Shimano Saints) weren't evenly out of the caliper housings. I pulled on the levers gently, so as not to pop the pistons out, and cleaned around them whilst they were sticking out a bit. Just wondering if you then need to re align the calipers to the disc so that everything works evenly. I figure this has probably been covered before somewhere on here but haven't been able to find it. Hoping someone can point me to the correct thread or to a website where this is covered, cheers Steve

 

[HORSPWR]

Do both pads move when you pull the lever or does one move first followed by the other. You don’t want one contacting the rotor first and trying to pull it side ways before the other pad contacts. I always set mine up so that they both contact the rotor at the same time and that the gap is even on both sides before they start to move. I shine a torch underneath and look down from the top to get it right. If they don’t move at the same time I reckon you’ll have to get that sorted first.

 

[Husky430]

Yeah that is happening now, since I've cleaned the pistons, but don't think it was happening before. I used an old brake pad and a large bladed flat screwdriver to hold one set of pistons in whilst pulling on the brake lever to get one set of pistons out at a time. Cleaned them and then changed over to the other side and did those.
Once I had them all clean I pushed the pistons all the way back in and then watched, with no wheel in, to see that they all moved at one time which they did. Just figured there would be something written about the whole process and the correct order in which to do it and also to align the actual caliper with the disc as I did this by eye.
All seems to work ok but would like to know the right way to do it for the future.

 

[boBE]

I put a 0.25 mm shim on each side of the rotor then pull the brake lever as I tighten the caliper mounting bolts. This seems to align the caliper as closely as possible.

 

[urastus]

I put a 0.25 mm shim on each side of the rotor then pull the brake lever as I tighten the caliper mounting bolts. This seems to align the caliper as closely as possible.

Yes, I forgot about about this. I used to use cloth tape on a section of the rotor - then remove it and clean with isopropyl alcohol.

 

[Husky430]

I was wondering as well, on the front Allen bolt of the caliper there is a funny type of clip, that if you pries it apart, turns around the bolt head. Seems to have teeth and so does the bolt that lock in one direction. Figure it's some kind of locking device to stop it coming undone, but not sure exactly how this works. Why on only the front bolt and not both? Can't seem to find a pic of it on the web, they all seem not to have it, maybe it's a Merida thing?

 

[Husky430]

I put a 0.25 mm shim on each side of the rotor then pull the brake lever as I tighten the caliper mounting bolts. This seems to align the caliper as closely as possible.

This would only work properly though if the pistons were coming out in unison?

 

[urastus]

This would only work properly though if the pistons were coming out in unison?

Try it. First loosen off the brake reservoir on the handlebar and move it so that it is level. Undo the bolt where the fluid / oil goes in. Remove wheel, now push pads all the way home (some oil might come out of the reservoir). Put tape or something on rotor to use as a spacer. Reinsert wheel. Work brake lever till it is hard. Top up brake oil with the correct funnel if you have it - note, with a small amount of oil in the funnel, work lever till bubbles stop coming out. Replace bolt in reservoir. Remove tape off rotor - gently. Then clean rotor with isopropyl alcohol or methylated spirits (wood alcohol in the states).

That clip is a safety feature. I think in some events it is mandatory. For motorcycle racing the caliper bolts have to be wired.

 

[Husky430]

Thanks for all that Urastus, will give it a go and see how I go.

 

[HORSPWR]

This would only work properly though if the pistons were coming out in unison?

And if they are coming out in unison you may as well forget the shim and just pull the pads onto the rotor to centre and align the calliper.

 

[KennyB]

Yeah but, especially on larger discs, tightening the mounting bolts seems to twist the caliper and mess it all up. I got these and they worked a treat.
Birzman Clam Disc Brake Measurer https://g.co/kgs/sFcFZ7

 

[Rusty]

Quite often it is only a bit of grunge causing a stick. I push each side in gently with an old motorcycle tire lever (a large flat screwdriver can do the same) then gently work the brake lever to see if both sides move. When the pistons are slightly out, wipe around the piston with a cotton bud dipped in the appropriate brake fluid then push them back in.
I then loosen the caliper slightly and refit the wheel. Give the wheel a spin then pull the lever and observe if both sides move correctly - then spin again and hold the lever while tightening the caliper bolts. As @KennyB said, often tightening the caliper causes a twist.

 

[salko]

Yeah but, especially on larger discs, tightening the mounting bolts seems to twist the caliper and mess it all up. I got these and they worked a treat.
Birzman Clam Disc Brake Measurer https://g.co/kgs/sFcFZ7

Large rotors easily flex sideways and while tightening caliper bolts while pressing the brake lever the caliper tends to make a slight side-movement, flexing the rotor sideways, and then after you release the lever caliper will stay put, but the rotor will return to its normal position resulting in not properly aligned brakes (possible rubbing). The only brakes I know that have small side bolts in mounting eyelets to prevent this from happening are Dominion A4.

 

[GrahamPaul]

Yeah but, especially on larger discs, tightening the mounting bolts seems to twist the caliper and mess it all up. I got these and they worked a treat.
Birzman Clam Disc Brake Measurer https://g.co/kgs/sFcFZ7

A folded business card does the same job. Usually cheaper and eminently disposable, too.