Braking bad, braking better...

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nickst4
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Braking bad, braking better...

Post by nickst4 »

The last time I went out on the 1K, I found the front brakes were virtually non-existent when I needed to pull up sharply at a roundabout. This had happened before too, not long after I got the bike, but I don't recall how much I had to do to reinstate them, apart from freeing sticky caliper pistons.

This time, all eight pistons were extremely difficult to pull out, despite using a proper piston-extractor tool. I invested in a Powerhouse kit to include eight stainless pistons in hope that the problem would be solved once and for all. When I did get the old pistons out, they were immaculate, so the seizure was due to the seals gripping them far too tightly. Here things get a little tricky, because the seals had some sort of residue on them. At one time, I was using a red grease on hydraulic assembly that I subsequently found was mineral-based and not compatible with rubber, so I suspect I was responsible for the seals expanding and sticking the pistons. Well, you live and learn, even if it takes several lessons!

So I cleaned the otherwise immaculate calipers and proceeded to fit the Powerhouse kit. Fine with the larger pistons, but the smaller ones were almost impossible to get to go in, despite using proper Brembo lubricant. There was no option for it but to refer to Powerhouse, who were extremely responsive and offered to have the complete calipers in their workshop and even contributed to the postage. However, they found the small pistons were indeed very difficult to fit, despite their seals having been successfully used in very many Brembo calipers of this spec. They rebuilt the calipers twice, and even fitted new stainless clamping screws to the two halves, returning them free of charge, but felt that there might be inconsistencies in the original machining of the seal grooves. Seems unlikely to me, and I'd question the spec of their 30mm seals.

Whatever, after a protracted bleeding session which never got the proper feel at the lever, presumably because because the pistons were not yet moving freely, I went out on the bike. I thought if I put light pressure on the front brake, I'd get some heat into the system and get the pistons to advance more closely to the discs. Maybe they did all of a sudden, because the next moment the front wheel locked! The road was not clean so I should have been more wary, but the bike stayed upright. Scary though: I've never locked a front wheel before. :shock: And stayed upright anyway.

In the course of the subsequent ride, the brakes improved a lot. It may well be that the very recent pads need to bed back in properly, but the bike won't go out again this year because the roads are so slimy around here and the road-tax expires in a couple of weeks anyway.

Aside from all the other complications in this saga, please do ensure that any lubricants you use with hydraulics are compatible, and don't trust them just because they are the traditional colour! :oops:

Nick
Last edited by nickst4 on Fri Nov 13, 2020 8:51 am, edited 2 times in total.
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Trevor68
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Re: Braking bad, braking better...

Post by Trevor68 »

Timely, I actually just bought some red rubber grease to use while putting a kit through my master cylinder.

Amazing the difference new seals make, brakes are awesome now. Though I'm using Suzuki K5 Master with Suzuki K3 calipers.
andybaggies
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Re: Braking bad, braking better...

Post by andybaggies »

Timely, I actually just bought some red rubber grease to use while putting a kit through my master cylinder.
That red rubber grease it great stuff. I try to be diligent and clean the brakes once a year usually after the winter. Take a caliper off, gently squeeze the lever with the pads chocked to reveal more of the pistons. Clean accumulated crud with cotton buds, zip ties & brake cleaner. Smear a new layer of red rubber grease around the pistons and push back in.
Whatever, after a protracted bleeding session which never got the proper feel at the lever,
I've never quite managed to bleed the front brakes to 100% satisfaction. I suspect the curved section behind the triple tree allows for air bubbles. Tilting, moving the bars and fruitless pipe tapping may help.

One other thing to check is the action of the lever on the master cylinder piston. I've had this go squeaky and uneven in its action before now.
Maybe they did all of a sudden, because the next moment the front wheel locked!
That doesn't sound good... as much as it's a pain I'd be tempted to at least remove the caliper to re-check & re-grease the pistons (without removing them).
nickst4
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Re: Braking bad, braking better...

Post by nickst4 »

Thanks for your comments, Andy.

My write-up was a bit long-winded, but I did say the calipers had only just been assembled to the highest standards by Powerhouse, albeit with new small-piston seals that were rather tight. That was why the pads weren't applying themselves evenly to the discs, until they suddenly did. Definitely a brown-trouser moment!

I'm sure the pads have still got to make proper friends with the discs, but they were much better during the ride, and the lever feel was pretty good. It'll get better, I'm sure. :nod:

Cheers,

Nick
nickst4
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Re: Braking bad, braking better...

Post by nickst4 »

Just a follow-up to the saga of sticky pistons. I took the Raptor 1K for MOT this week, and despite excessive lever travel, the braking passed Sean's test, as did the rest of the bike. I rode away from the garage, applying some front brake to try to get things to settle down and just like before, the front wheel locked with no warning, and this was on a dry road at maybe 30mph. Fortunately, I stayed upright if shaken!

At home, I confirmed that the pistons were very tight in the seals, especially the smaller ones, and they just would not slide through but merely rebounded with the resilience of the seal rubber. This left the pads quite loose, hence the excessive lever travel. Likely, one or more of the pistons would suddenly move and cause the instant lockup.

At this point, I remembered buying a spare pair of decent Brembo front calipers from a Ducati ST years ago, in case I might need them sometime. Being the exact same spec as the Raptor ones, I dug them out, fitted my old pads, and was delighted to see how easily the pistons slid in and out.

The upshot was a super short (untaxed) ride today with normal braking restored. Powerful and progressive, and completely controllable. The bottom line appears to be that the original Brembos fitted to my Raptor were machined with the seal grooves too shallow. This is the only explanation that the helpful people at PowerHouse can come up with, and I can't see any other possibility. I'd had some history of the Raptor's brakes losing power due to sticky pistons before I attempted to refurbish them, so that points in the same direction.

I wish I'd tried the caliper swap before investing £170 in the seals and pistons kit, but such is life... :angry: :roll:

NIck
sidrat
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Re: Braking bad, braking better...

Post by sidrat »

Nick, that is intersting, I dont theink the Brembo's are much good on the Raptor. I have cleaned them and put my favourite pads in them and run new single lines to each caliper, but they are still not good brakes. I was considering a master cylinder swap as the next step.
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nickst4
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Re: Braking bad, braking better...

Post by nickst4 »

I've never had a problem with the same calipers on my 2000 ST4, which is appreciably heavier than the Raptor. They aren't as powerful as the later Brembos, much less the modern radials, but they more than do the job if you ride with anticipation. The same calipers are on our 650 Raptor, and they are OK. Obviously, the choice of pads is relevant, and I stick to GoldFren HH type; enough bite but not silly.

All good fun! Roll on the 1st of May when all the bikes get back on the road! :thumbsup:

Nick
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