Motobins brake pistons - plastic face covers?

[MMC]

May I have your advice chaps?

I'm rebuilding my calipers on the Panzer with s/s hoses, plus new pistons and seals. Just got the new pistons from Motobins. Unlike the old pistons, the new ones come with a sort of holed plastic cover on the pad side that sits slightly proud of the piston edge:



Not seen this before... The old ones have no cover (hollow cups) and ones I've used previously have been likewise. Are these plastic covers just a bit of protection that needs levering out before fitting or do I leave them in place?

I'll give 'Bins a call in the morning but wondered if anyone else had got the answer already.

And yes, I realise it's a klutz question

 

[Flipfly]

When I did my 2000 1150 brakes they had the plastic covers in place on the pistons.

 

[MMC]

Thanks Flip - looks like that's the case.

Advrider is saying the same thing: http://www.advrider.com/forums/showthread.php?t=161264

 

[Mr K]

I'm going to go controversial here and suggest the plastic caps should be taken off before installation..... for the simple reason plastic will compress under the forces imposed during braking.

 

[MMC]

Oooh - 50:50 now!

Any more votes? Or shall I just leave the brakes off altogether? I never really go fast enough to worry.

 

[Mr K]

Oooh - 50:50 now!

Any more votes? Or shall I just leave the brakes off altogether? I never really go fast enough to worry.

I would suggest plastic should not form any functioning part of a brake piston.

I don't know this to be true, but I feel it.

 

[DrFarkoff]

Its standard that they are fitted

Its the anti squeal mechanism that BMW chose to utilise

 

[MMC]

Its standard that they are fitted

Its the anti squeal mechanism that BMW chose to utilise

Ah - cool. I'll give Motobins a call this morning too, just to make sure

In the meantime I'm on the hunt for a set of rear caliper pistons. The Motobins kit for the fronts includes pistons. The kit for the rear just seals. Go figure.

 

[littleredrooster]

Its standard that they are fitted

Its the anti squeal mechanism that BMW chose to utilise

Yup - my old 1150 certainly used to have them.

 

[Flipfly]

Its standard that they are fitted

Its the anti squeal mechanism that BMW chose to utilise

It works too because my front brakes squeal now because I managed to crack the plastic covers.

 

[Timolgra]

It works too because my front brakes squeal now because I managed to crack the plastic covers.

Yes, it's only after the event you realise that levering them back with a screwdrivers' not a good idea

 

[Flipfly]

Yes, it's only after the event you realise that levering them back with a screwdrivers' not a good idea

Don't remind me.

 

[Orinoco]

Ha, my bike has the plastic covers on one calliper and none on the other

... so it only squeals on one side

 

[The Grey One]

Don't remind me.

You should leave the old pads in and lever against the friction material to push the pistons back, they re scrap anyway.

John

 

[Flipfly]

You should leave the old pads in and lever against the friction material to push the pistons back, they re scrap anyway.

John

It was a bit more than that as the pistons needed cleaning to get them back in place, hence I had to remove the pads. Took us an hour or so to get em back in and had to do each piston individually. I will be rebuilding them over winter with new pistons.

 

[MMC]

I will be rebuilding them over winter with new pistons.

Yep. Exactly what I'm doing. New s/s braided hoses, new pistons, new seals, new pads. And a lot of coffee.

 

[Packer]

Guys, buy the correct tool or use a "G" clamp, make blocks of wood to hold the replaced pistons fully home as you press in the next ones.

It's a 10 minute job per caliper

 

[Black Rooster]

I use this
http://www.toolbox.co.uk/draper-52335-12-square-drive-14630-66533