Brembo caliper piston Dust Seal

[suecanada]

Apologies for being so tardy visiting this forum for oh so long but now I need your sdvice:

Little Red Baron (LRB) is a 1983 R65LS who I knew would get back at me for allowing him to sit too long while the DR650 and Honda NX250 got to travel.

The brembo brake caliper dust boot surrounding the caliper pistons on both pistons have become dislodged BECAUSE there was rust on the back of the pads so when i levered those pads up and out (took a lot of effort), the dust seals on the left brembo caliper were dragged out of their seats. They look fine but are probably stretched so I have ordered new ones from Motobins.

Question: How to put them on? Do I have to split the caliper to accomplish the job or can a small pair of fingers fit the dust seal into those very shallow grooves. Not even sure there is a groove to receive a seal lip. I personally have little faith they would stay in the grooves.

[suecanada]

Just me again...I will really need the answer to my question pretty soon! Please someone out there...help...!!??? :-? :-/

[Kelvin]

I've only done it with the caliper split. I see no reason why the dust seals couldn't be installed with the caliper assembled it would be difficult to confirm that they'd seated properly.

Have your calipers not been rebuilt recently? For peace of mind I'd be scheduling a rebuild so I could inspect the pistons following the problem with the rusty pads.

[Barry]

Looking on Motobins I see  a difference between the otherwise similar Ate and Brembo calipers.  The Ate dust boots are secured with a circular metal ring which is included in the Ate overhaul kit.  The Brembo overhaul kit does not contain this part for securing the dust boots. 

From that I deduce that Brembo dust seals just press into position but someone may be able to confirm that. 

Many years ago there was a thread that posted a fairly detailed comparison of the Ate and Brembo calipers which I think noted the difference in the dust seals.

[Kelvin]

The Brembo dust seals just press in under finger pressure (when the caliper is split). Easy when they're apart, difficult to access with the caliper assembled but I'm sure with a bit of fiddling it could be done.

The exposed end of the piston has a lip that the inside of the dust cap fits into.

There's no extra part, no circular metal ring, necessary.

[suecanada]

Thanks Kelvin. I can get my fingers inside the unsplit caliper
so when the new seals arrive I will get those pistons out just a tad to expose that groove. Then give it a go. If that begins to frustrate me I will bit the bullet and split the caliper. There is an O-ring shown in the big BMW manual I have so I was hoping not to disturb it. But maybe my Motobins delivery will have one of those in its rebuild kit.
No matter, I'll let you know how it all goes down later.

[dogshome]

The seals on Brembo calipers are not exactly a tight fit - even brand new. I found I had to get the pistons out about 5mm to get the inner lip on though. Pads out, bit of wood in between and pump with lever.

If they have not been apart for a while, I would do the seals internally as well. Changing the fluid and bleeding doesn't get the gunk out from the seal area.

My front brakes felt fine and very powerful if a bit grabby. Then they decided to emergency stop by themselves. Luckily only doing 20 just coming off an island and in a straight line 5 mins from home.

Rebuilt: the brakes are more like 'adequate' and definitely not powerful or grabby. If you grab it like you mean it, then it will stop very well. In normal, good condition they should be un-noticeable, progressive and definitely not to be wary of or weak.

Bleeding means one caliper, then other, then back again. Takes several goes and minutes. Take the master cylinder out and clean the little bleed hole with a <0.3mm wire and around the input shaft (which will be corroded to hell by the aluminium it lives in). You know it makes sense  8-)