Rear brakes seized

Friday Nov. 18th,, one last ride for the season,, on a gorgeous 18c deg day. But BlueStar had other plans. It had been running just great,,, but after leaving a country intersection,, it suddenly felt like I had lost a cylinder,,, then two cylinders worth of power drop. But when I clutched and the bike decelerated rapidly,, I knew it was brakes dragging. By the time I pulled over,,, maybe 10 seconds worth,, the rear tire was stuck solid. Knowing what the likely causes were,,, I just called CAA and about 30 minutes later a big old flat bed was gently trucking us home. After that 30 min delay,, the rear wheel was still dragging,, but I could roll it with effort.

So the investigation begins,,, and it is worth noting that I installed new rear pads about 8k km's ago. Firstly, I am going to do a visual inspection of the SMC,, as much has been written about it's problems. btw,, BlueStar has about 140k km's on it, and I don't know if the SMC has ever been serviced before. So it is time to do that anyway. But if the SMC looks good (little corruption on the piston),, then that indicates the rear caliper may need rebuilding as well.

Any other checks I should consider ?? It was a fantastic summer on my ST, and I hardly rode my other bikes. BlueStar was just letting me know there is a problem or two lurking,, and it is time to call it a season to deal with those. Any advice on the topic is appreciated,,, Cat'

My smc looked good, but the piston was out of round and was sticking in the bore. after disassembly, you should be able to move the piston in/out with only the rubber seal worth of resistance.

Catmandu2 said:

Any advice on the topic is appreciated,,, Cat'

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When I rebuilt my SMC at 60,000 K I was surprised that it had continued to work at all. It was difficult to get the piston out of the bore and I succeeded with difficulty using the air pressure method described in the threads. When it did pop out it did so with a surprising velocity. If yours is the same keep a heavy towel over the top of the cylinder to catch the pieces .... and keep your fingers out of the way. Once I cleaned the cylinder the new piston slid like butter. Make sure the groove for the retaining circlip is immaculate to save yourself grief on the reassembly.

"you should be able to move the piston in/out with only the rubber seal worth of resistance."

This comments refers to the piston in the bore without the spring. Once reassembled the spring will return the piston smoothly to top position against the clip without any hesitation or delay.

While you are at it... have the brake circuit opened up, would be a good time to rebuild all three calipers. The hardest part will be recharging the brake fluid. Cleaning the pistons and replacing the seals will help in giving you better stopping power. The brake performance can diminish slowly over time due to sticky, dirty pistons.

This is probably your SMC but before going out and buying parts, I would check and clean all three master cylinders, thoroughly clean the pistons, clean the calipers, pull the calipers apart and grease the Nissin pins. No need to replace the piston seals unless they are leaking. Check your rear master cylinder for trash and make sure the fluid return orifice is not occluded.

My experience with rebuilding MCs of any kind has been a crap shoot, so, if it were mine, I would just replace it. It seems like SMCs were updated at some point so all may not interchange with all years, also, ABS may be different. Good luck!

I would agree with JMCarruth. Given the the safety critical nature of any brake system part and the pretty tough environment in which they function (heat, dirt, vibration, corrosion etc. etc.) - I would look at replacement unless you are an expert at rebuilding or the problem is very simply to fix upon inspection. That bike is now 13 MY old - and so it likely hasn't had any major repairs - so those parts don't owe you much at this point.

Pete

Not sure about ON but here in Calgary, the difference between the SMC rebuild kit and a complete SMC was only about $65. Based on Larry's (Igofar) experience and recommendation, I opted for the complete kit.
Rod

On my 2010, I had my rear brakes lock up a couple of years ago after replacing the rear tire. Not sure why, but I had to rebuild the SMC, the rear Master cylinder and the rear caliper. They've been great ever since!

SupraSabre said:

On my 2010, I had my rear brakes lock up a couple of years ago after replacing the rear tire. Not sure why, but I had to rebuild the SMC, the rear Master cylinder and the rear caliper. They've been great ever since!

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Now I'm just repeating what I've read, but it made sense to me. If you push the pistons back in at the caliper (as you may need to do when refitting a wheel) you may push any debris that has accumulated at the end of the line (i.e. the caliper) back into the master cylinder where it can cause a clog. The work around for that is to open the bleed valve when you push pistons back, or do a bleed/flush at the same time.

TerryS said:

Now I'm just repeating what I've read, but it made sense to me. If you push the pistons back in at the caliper (as you may need to do when refitting a wheel) you may push any debris that has accumulated at the end of the line (i.e. the caliper) back into the master cylinder where it can cause a clog. The work around for that is to open the bleed valve when you push pistons back, or do a bleed/flush at the same time.

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That is quite true Terry - and not a bad idea for any time you have to push the pistons back into any sort of slave cylinder (clutch slave cylinder or brake caliper).

Pete

TerryS said:

Now I'm just repeating what I've read, but it made sense to me. If you push the pistons back in at the caliper (as you may need to do when refitting a wheel) you may push any debris that has accumulated at the end of the line (i.e. the caliper) back into the master cylinder where it can cause a clog. The work around for that is to open the bleed valve when you push pistons back, or do a bleed/flush at the same time.

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MaxPete said:

That is quite true Terry - and not a bad idea for any time you have to push the pistons back into any sort of slave cylinder (clutch slave cylinder or brake caliper).

Pete

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That is absolutely correct! Unless you're like me and get so tired at the end of it all that you just push to get it done, and then the rear locks up on you and you have to tear it all apart again! :

So,,, digging into the smc a bit,,, I got the rubber boot off, and found this pile of rust dust crud on top of the pushrod. Intially, I thought that the snapring was corroded away,,, but after a bit of cleaning I see that it is intact. Funny,,, once I put a bit of penetrating oil to soak in on the snapring,,, the rear brake freed up !! Not sure if I will pop the piston ***'y out before I have replacements in hand. That could take a while,, because I get my Honda spares state-side, where they are %40-50 less $$$,,, Cat'

TerryS said:

Now I'm just repeating what I've read, but it made sense to me. If you push the pistons back in at the caliper (as you may need to do when refitting a wheel) you may push any debris that has accumulated at the end of the line (i.e. the caliper) back into the master cylinder where it can cause a clog. The work around for that is to open the bleed valve when you push pistons back, or do a bleed/flush at the same time.

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If you maintain your brake system there is no debris at the end of the line. You will have flushed the system at least periodically.

As an aside pushing debris all the way from the calipers to the master cylinder will take far more movement than retracting a piston.

Catmandu2 said:

So,,, digging into the smc a bit,,, I got the rubber boot off, and found this pile of rust dust crud on top of the pushrod. Intially, I thought that the snapring was corroded away,,, but after a bit of cleaning I see that it is intact. Funny,,, once I put a bit of penetrating oil to soak in on the snapring,,, the rear brake freed up !! Not sure if I will pop the piston ***'y out before I have replacements in hand. That could take a while,, because I get my Honda spares state-side, where they are %40-50 less $$$,,, Cat'

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Yikes!! Seems like a bit of a mess. According to Larry (Igofar), he has found that simply repairing the SMC with a rebuild kit is risky (ie. prone to issues). If I recall, it seems he finds the bores are out of round sometimes. His recommendation is to replace the whole SMC assembly, which is surprisingly inexpensive (not to mention, easier). I think I paid about $120 Cdn a couple of years ago from the dealer here in Calgary.
Rod

dduelin said:

As an aside pushing debris all the way from the calipers to the master cylinder will take far more movement than retracting a piston.

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Maybe, maybe not. If you look at a typical 2-piston caliper on my ST1100 with 27mm pistons, and assume that the brake hose id is 2mm, for every 1mm of pad movement you will displace 572 mm3 of fluid and that will move 190mm along the brake line. Push the pads back by more than about 3mm and I'd say you have a very good chance of having fluid that had been in the caliper returned to the master, along with any crud that was floating in it..

Current Canadian pricing is $180.cdn plus %13 taxes,, so a bit over $200.cdn total. $65.cdn+ taxes for the rebuild kit. I think your dealer gave you a bit of break, Rod. My dealer recommends replacing the whole assembly as well. Filling the push-rod boot with a high temp silicone grease seems like a good idea, to prevent this kind of crud building up again. I may be asking Santa for an early gift ,,, Cat'

drrod said:

Yikes!! Seems like a bit of a mess. According to Larry (Igofar), he has found that simply repairing the SMC with a rebuild kit is risky (ie. prone to issues). If I recall, it seems he finds the bores are out of round sometimes. His recommendation is to replace the whole SMC assembly, which is surprisingly inexpensive (not to mention, easier). I think I paid about $120 Cdn a couple of years ago from the dealer here in Calgary.
Rod

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Catmandu2 said:

Current Canadian pricing is $180.cdn plus %13 taxes,, so a bit over $200.cdn total. $65.cdn+ taxes for the rebuild kit. I think your dealer gave you a bit of break, Rod. My dealer recommends replacing the whole assembly as well. Filling the push-rod boot with a high temp silicone
grease seems like a good idea, to prevent this kind of crud building up again. I may be asking Santa for an early gift ,,, Cat'

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Holy crap!!! That is a significant price increase. I looked up my bill and it was $128 in July of 2015. If you want, I can check here and if it is still a "good price", I could just send it to you. Let me know.

Interesting that the rebuild kit is about the same as I was quoted in 2015.

Rod

Short Story, Who would of thought?
I won an SMC at the Sooke, B.C. WESTOC. A member came up to me after I won it and asked me I wanted to sell it. I said sure as my brakes were working fine. So I said how bout $75, he said wait, let me go talk to my friend over at another table. I felt bad as I never knew what that were worth and maybe I was asking to much for it. He came back and said would you take a $100USD for it, said sure
You meet the nicest people on a Honda.

BTW,,, just for fun, I pulled the snap ring out of the smc tonight,,, and found a bunch more of that dusty rusty stuff underneath the push-rod. And I can see how it could easily be preventing the piston from rising back up to it's rest position. It is hard to say what this gunk is,,, road and brake dust mixed into the dried out remains of 12 year old grease, perhaps. Anyway,,, I have managed to do this much with the SMC still attatched to the bike. So when I get an hour tomorrow,,, I will clean the top out,, and see if the piston wants to move. Guess I best not stomp on the brake pedal,, huh !! Cat'

Interesting that you should say "stomp on the brake pedal"..... My current bike (04) had 72,000kms on it when I got it. I had just gotten rid on an 04 with 190,00 kms. My old bike never had a hint of a brake problem. On my way home, with the new bike, I had a left turner. Hit the brakes HARD. Within 100 yds of doing that, the rear brake started to hang up. Almost locked solid in the 2 miles it took to get home. When I took it apart, the SMC piston was seized solid. The bore above the piston was clean. I didn't even try to take the piston out or rebuild it, just replace the whole SMC. Incidentally, the previous owner had not a hint of brake problems. The brakes had been serviced religiously while he owned it.

Theory....the previous owner had not really used the brakes hard and when I did, it forced the piston into an area of the bore that was not been used very much (if at all). Result - piston got hung up for some reason.

Take home .........use the brakes hard and often ie. take them to the gym to keep them in shape.

Rod