Rear Brakes Issues

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Apr 26, 2014
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33
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Central New Jersey
Rear Brake Issues

I?ve felt that the rear brakes on my 1998 non-ABS ST1100 have been less than stellar for some time now. Prior to a summer trip to NH where I put on about 1300 miles over the course of 4 days I thought that I would change the rears pads. Well, I noticed that one of the cylinders was not as smooth as the other and it was very difficult to get it to more in and out. I also noticed that there was a little bit or corrosion on the cylinder wall, however, not what I would consider excessive, especially compared to what I?ve seen on cars. Anyway, I decided to attempt to clean what I could reach with a nylon abrasive pad. It got it cleaner, but not perfect. I was able to get the second cylinder to move by isolating the other one and eventually it got better. Not perfect; but better.

Anyway, as part of normal maintenance, I decided that it was time to change the brake fluids, front and rear. The fronts went off without a hitch, however, the rears are a bit of an issue. No matter what I do, I continue to get air in the line, and here?s the VERY weird part, I get air even when the bleeder valve is completely closed. I?m using a manual pump to get the air out. Yes, I?m pretty sure that it?s not the pump or the lines. They hold pressure when I put my finger on the end of the hose.

So, I completely removed the bleeder valve and noticed that it had some corrosion. I ensured that all of the holes were free of corrosion and used a brass brush on the ?vee? part of the bleeder screw. I put the bleeder back into the caliper and tried to bleed the brakes. To be honest it was about the same.
OK, after all of that, here?s my question. In addition to new seals and possibly new cylinders and a bleeder valve, is there a way to clean the seat within the caliper that the bleeder valve goes into (God, that?s incredibly poor grammar.) I?d appreciate any advice, short of ordering a new complete caliper.
Also, did anybody else notice that the Nissin bleeder valve is the same one that?s on a Honda CR-V?
 

ST1100Y

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...used a brass brush on the “vee” part of the bleeder screw.
hmm... a possible not so good move as the tip is supposed to seal against its counterpart in the calliper bore; scratches might be counter-productive so I'd replace the bleeder bolt too while at it...

...is there a way to clean the seat within the caliper that the bleeder valve goes into
That surface got milled at the factory, since its aluminium it should shape/smooth due/by the tip/cone of the bleeder bolt torqued in; so you'd probably on the safe side there (would need to see the thing...)
IMHO you will need new pistons, once their surface is corroded their done (car ones are covered with dust-bellows so only the outer edge corrodes, the ones on motorcycles not... long usage with worn down pads bears the risk of ending up with corroded calliper pistons and the consequential damages to rings and calliper-bores...)
Once the old ones are removed you can inspect the bore to check for scratches/scoring, ruling if you need a new/replacement calliper anyway or if its still usable.

Other items to consider:
- repair kit for master cylinder
- removing brake pedal to clean and lube the pivot
 

John OoSTerhuis

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Like Martin, I'd probably do an rebuild of pistons and seals. Did you pump the recalcitrant piston out enough to clean the portion behind the dust seal? BTW, I suspect that all you need to do to the bleeder valve is put a wrap of Teflon tape on the threads. A tip I've used to keep air out while bleeding. HTH

JOHN
 
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It might be a good time to replace the hose with a Galfer braided stainless one.
A braided SS hose on the front improves the braking response, but I wouldn't recommend a braided hose for the rear brakes. Less sensitivity on the rear brakes is a good thing, because you don't want your rear wheel to lock up easily. It would be better to replace the rear brake line with an OEM rubber hose.
 
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A braided SS hose on the front improves the braking response, but I wouldn't recommend a braided hose for the rear brakes. Less sensitivity on the rear brakes is a good thing, because you don't want your rear wheel to lock up easily. It would be better to replace the rear brake line with an OEM rubber hose.
Agreed. The big difference between front and rear is the rear line doesn't really flex all that much, partly because its a much shorter run of hose, and partly because you're not putting as much stopping pressure into it as well. SS lines won't really be worse, they're just not necessary because the issue they address (flexing) is generally not an issue with the rear brake line.
 

Firstpeke

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Having ridden a non ABS ST1100 with SS lines on the front I found the brakes had little feel compared to standard..... they were better, but required a more sensitive touch, especially if used in anger....

I would prefer not to put SS lines on a non ABS rear brake for that reason.....

I like to think I have a delicate touch on my rear brakes as I do use it more than average, especially for those delicate moments like trail braking, but as I said it would need a real sensitivity to use the rear brake with SS lines without ABS....

YEMV.
 
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As your rubber hoses age they will expand when you squeeze the lever or depress the pedal. The more they expand the more effort it takes from you to effect the same stopping power you had when they were new. Stainless braided hose eliminates that deterioration. You will always know that x amount of effort equals the same amount of braking, depending on conditions. I have 50 years in the saddle so I know enough to let off before wheel lock up/skidding. If I had the choice of buying a new ST with or without ABS, I would opt for one without it and less weight and complexity. Look at the trouble some have had with these systems. I was a Honda tech for five years and and aircraft tech for more than 40. We change flexible hoses on a time basis on aircraft. You should consider replacing rubber hoses with new or at least inspect them carefully for cracking. You can't see the inside of these hoses but they can fail internally as well. I wanted a worry free machine for the next ten years, if my body holds up well enough. I feel that the braided stainless hoses were a good investment. If they are not, why do all the race bikes use them?
 
OP
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I appreciate the inputs re: the trade offs re: SS brake lines versus standard rubber, however, I'm trying to figure out how the bleeder valve is leaking air even when it's completely closed down. I attached the vacuum hose to the rear caliper bleeder (again fully closed) pumped up the vacuum and then watched the vacuum gauge slowly lose pressure. I tried the same thing on one of the front bleeder valves and the gauge held pressure just fine. That being the case, it appears to me that I'm looking pressure (bleeding air) right through the center of the bleeder valve. I read John's O's previous response re: teflon tape on the threads, however, I'm figuring that the bleeder just isn't seating properly. Does that make sense? I understand that at some point I'm going to have to get new seals, possibly cylinders, and of course a new bleeder valve, but i'm worried about the seat that the bleeder fits into. Other than completely disassembling the caliper and possibly scraping the seat with something that won't damage it (I'm leaning toward a sharpened piece of wooden dowel) are there any other suggestions. Thanks in advance.
 
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Does fluid leak out around the bleeder threads when you aply brake pressure? If swapping a different screw in doesn't stop the leak you do have a bad seat. You might polish it a bit with a Q tip in a drill with some valve lapping compound on it.
 
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