Brake bleeding tip

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nickst4
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Joined: Mon Jul 11, 2016 12:48 pm
Location: Norfolk

Brake bleeding tip

Post by nickst4 » Sat Sep 07, 2019 7:51 am

This is a memo to self really, because I remember having this revelation before but forgot it yesterday! :doh:

I've been suffering from poor front brakes on the Raptor 1K just recently and decided to upgrade the old Brembo pads to my favourite GoldFren HH ones, which have good initial bite but not excessively so. All well and good, but of course the caliper pistons wouldn't retract fully so a full stripdown was needed. This was made easier with a Laser-brand piston-removing tool, rather than the usual juggling with a footpump.

Anyway, the pistons and seals were fine but just needed cleaning and lubrication with red grease. Then came the installation and bleeding. These bikes have composite brake pipes with curved metal sections that appear to trap bubbles, so the bleeding took a while.

The revelation (to get to the point!) is that if you have adjustable brake levers, set them to the widest span so you get the longest-possible stroke of the master cylinder to expel air. Once the pistons have advanced and the pads have bedded in, I'll reset the lever span.

There: maybe I'll remember the next time! :thumbsup:

Nick

andybaggies
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Re: Brake bleeding tip

Post by andybaggies » Sun Sep 08, 2019 7:43 pm

It's memo I'll read and also refer to...

And yes I've always had trouble bleeding the front and the last time I had to add fluid to an empty system I used the reverse bleeding method by using a syringe to pump fluid up from the caliper end, and it worked a treat.

nickst4
On the Road
Posts: 271
Joined: Mon Jul 11, 2016 12:48 pm
Location: Norfolk

Re: Brake bleeding tip

Post by nickst4 » Mon Sep 09, 2019 7:46 am

Yes, I eventually resorted to reverse filling with a big syringe. Effective but scary, fearing that the connection will come off and brake fluid will go everywhere. End result was still extreme sponginess, simply because the pistons were not staying in their advanced position when the lever was released and bounced back on the resilience of the seals plus, of course, the new pads weren't bedded-in.

I went for a cautious ride like that, and was relieved to find the lever travel was almost back to normal by the end of twenty miles and the pads were beginning to bite satisfactorily. Job done, now back to the Raptor 650ie's shock linkage! :nod:

Nick

andybaggies
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Joined: Mon Feb 16, 2015 4:31 pm
Location: Wiltshire

Re: Brake bleeding tip

Post by andybaggies » Mon Sep 09, 2019 6:49 pm

Thinking back I also zip tied the brake lever in the 'on' position with the master cylinder cap removed with occasional 'taps' on the calipers & along the lines especially the curved pieces you mention.

I also unscrewed the lines from the bottom yoke and moved the bars from one side to the other in an effort to get them at a better angle.

I'm sure I read somewhere that you can get also air caught at the point the lines meet the master cylinder which can be a pig to release.

Not sure if any of this actually worked but it made me feel I'd accomplished something :oops:

Andy B

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