Perplexing Front Brakes

[oilspot]

Okay,

I had some dragging and Igofar talked me through some inspection and tuning advice. I found a pinched boot on the SMC side and a missing tiny o-ring on the rear. Rear pads were nearly new, so just cleaned everything and inspected the rear wheel bearings while I was in the vicinity. The front pads were maybe 50% worn, but the SMC side had a slight angle; so I put new Honda pads (06455-MCS-G02) on both sides.

Cleaned all the pistons, springs, used Q-tips to clean the slides. Reassembled everything carefully, checking that all the calipers freely floated on the pins (and no pinched boots this time!). I opened the front MC to check level. Visually checked rear MC and it was at upper line.

As far as I can tell everything went back together okay, no hiccups noted. Unfortunately the front wheel seems to be dragging and the rear wheel spins freely (a reversal of the original issue). I cracked a few bleeder screws and no residual pressure was observed. Yet the front wheel has a fair amount of resistance. I took it for a short ride, just in case bedding the pads would make a difference. Drove about 1/2 mile and coasted to a stop - all three discs were cool. I drove around slowly increasing speeds and doing firm stops with front or rear brakes. Then went for about ten mile loop on highway. I averaged about 45mpg if you believe the meter at speeds of around 65 mph. When I got home, none of the discs were excessively hot to the touch - but front wheel still barely turns.

I'm sure I checked a few other things, but probably forgot something important. What else can I check or adjust.

PS: The SMC has about 750 miles on it. I bled the system about five times before I got everything firmed up. After the new SMC, before I took everything apart, both the front and rear brakes felt nice and firm. After replacing the pads things were a bit spongy till about halfway through the test ride. I'm guessing maybe it took a while to fully push out all the pistons, but it could be something else.

 

[Obo]

Wheel spacers on the proper sides? (assuming you had the wheel off)

 

[SMSW]

Are you sure the springs and pads were seated properly in the caliper?

 

[Kevcules]

Surprised the front brakes aren't hot after a ride, if you say the front tire turns hard?
Try compressing one front caliper at a time and try rotating the tire to pinpoint which caliper is causing binding up front.
If both front rotors are cool after a ride, then it would seem to be ok.
These bikes LOVE a good slow brake fluid bleed.

 

[oilspot]

Are you sure the springs and pads were seated properly in the caliper?

Pretty sure. I removed everything and reassembled at the first sign of resistance with no change.

 

[oilspot]

Wheel spacers on the proper sides? (assuming you had the wheel off)

Good thought. Anything is possible in my opinion, given my newness. I think they are kosher - I realigned the forks prior to smc replacement. However, it’s worth checking. Any tips to easily check?

 

[jfheath]

Thoughts

Check the front wheel spacers and redo the front wheel tightening sequence - after slackening everything. Best to have the pads well clear of the discs for this.
While the pads are away from the disc surface, spin the wheel. If that is no better than when the pads are touching, then the binding isn't coming from the pads.

Article [13] - ST1300 - Maintenance - Front & Rear Wheel Install and Front Axle Animation | ST1300 Articles

Animated sequence to show the correct procedure when installing the front wheel into the forks of a Honda ST1300. The right hand side of the bike is the side with the brake lever. Left is the clutch lever side. This is the convention used in the Honda manuals. The video and the photo below...

www.st-owners.com

The pads fit into a chromed retainer clip that is fitted at the 'deep end' of the caliper - the opposite end from the pad pin. These are different for front and back - the rear retainer clip has a ridge in it to accommodate the notch in the tab end of the rear pads. The front clips do not have this ridge. Apart from this they are the same shape and size, and can be put into the wrong caliper if you are not aware. If the front caliper has the one with the ridge, then your calipers will not move as they should.

Since your rear wheel isn't binding my suspicions would be the front right caliper, but you need to check both.

The rear pads have a white heat shield sandwiched between the bronze metal back of the pads and the chrome antisqueal plate that has a lot of holes in it. The front pads should not have this white heat shield. The heat shield is not supplied with the front pads but there may be a temptation to fit one from the removed rear pads. If you have, it should be removed - especially with new pads - there isn't room. The rear pads must have the shield fitted. The rear caliper is not in a stream of fast flowing cold air and the shield is there to prevent heat from the pads from being transferred to the pistons - potentially boiling the brake fluid.

The slider pins - one on the caliper, one on the bracket - mate together into their respective partner holes. The holes have a rubber boot, and the slider pins have to be greased with silicone grease or red rubber hydraulic grease. Normal grease causes the rubber boot to swell. But only a smear of grease is needed. If you pack the holes with grease, it creates an air lock which either creates pressure or suction which prevents the caliper from moving away from the surface of the disc.

You will feel some heat in the disc surface if this is happening. The rear disc takes a lot longer to cool down after braking, and may still be warm anyway due to the heat from the engine and exhaust. The fronts should cool very quickly and normally there us no heat to feel except if you jump off to check immediately after braking hard.

The document below is written for the rear caliper, but the front caliper is the same design, more or less. Read through it see if something rings a bell. Download the pdf in the first post. There are lots if other little things that can cause issues - eg the fit of the pad spring - it is possible to fit them the wrong way round for all 3 calipers.

Article [13] - ST1300 Maintenance - Brakes- Avoiding the Pitfalls | ST1300 Articles

A close hands-on look at the Honda ST1300 braking system. These are personal observations about the things that can go wrong, why they go wrong and what can be done to keep things working sweetly. Updated April 2020 and to address more recent observations, to include information about the SMC...

www.st-owners.com

 

[Upt' North]

Good thought. Anything is possible in my opinion, given my newness. I think they are kosher - I realigned the forks prior to smc replacement. However, it’s worth checking. Any tips to easily check?

If you take the pads out or just push them back in slightly does it then spin freely? Simple test just to eradicate the brakes as the issue.
Upt.

 

[Al st1100]

check inside the master, the fluid hole at the botton may be slightly clogged not allowing the fluid to completely return. But that's just a guess asuming everything else is good.

 

[Obo]

Good thought. Anything is possible in my opinion, given my newness. I think they are kosher - I realigned the forks prior to smc replacement. However, it’s worth checking. Any tips to easily check?

Photos compliments of @jfheath is how I check. Taken from his "ST1300 front wheel remove and refit - a personal record" from 2017

You should have a larger spacer on the right side of the bike. It's easy to either swap left & right OR put the things in backwards on the proper sides...... been there, done that.





*I see John already posted the above axle photo.

 

[oilspot]

I will tinker tomorrow and report back. Even with the old pads, the wheel started to bind when the right caliper was installed so I will reevaluate that caliper.
Not exactly sure how to evaluate the MC orifices for blockage. I can see a piston or check valve moving when I apply the brake, but not sure how to check for malfunction.

 

[Igofar]

I’ll call you tomorrow.

 

[jfheath]

I see Larry has come out of his self imposed retirement.......

You say that after your test ride, all three discs were cool. Yet you say the front wheel was dragging.
If the front left brake pads were dragging, then the rear brake would almost certainly drag due to the action on the SMC.
Which suggests the right side. But if it was the pads dragging, the right disc would be warm.

Which suggests something else. So I would still be looking at wheel installation, fork leg alignment and wheel spacers.
Be aware that tightening things in the wrong order can present serious issues with the front wheel - so when the axle bolt is tightened, it has to be able to pull the wheel hub and both spacers together and clamp them tight against the right fork leg. If you tighten anything else before doing this, then it cannot do this. Also in theory there are 8 ways that you can install those spacers on the axle. Only one of them is correct.

But your question is worth answering anyway for any future readers.

Not exactly sure how to evaluate the MC orifices for blockage. I can see a piston or check valve moving when I apply the brake, but not sure how to check for malfunction.

The quickest check for the SMC is to lie down next to the bike, rotate the rear wheel with your foot, and operate the left right caliper/ SMC, by pushing the caliper bracket towards the fork leg. The rear wheel should stop turning and it should release the rear brake instantly when you release the push on the front left bracket.

I'm not sure what you mean by a 'check valve'.

However, all you can do without dismantling the Master cylinders is to check how easy it is to push in the pistons. This will reveal whether or not fluid pressure can return through the tiny compensation ports.

Make sure the pistons are clean.

The front brake lever operates both sets of front outer pistons. You should be able to push in the outer pistons with thumb pressure. Use both thumbs on one piston to avoid it rocking and getting wedged, but be aware that when you push in one piston, any of the other 3 front outer pistons will push themselves out. I use pieces of wood to make sure that this cannot happen. The piston should move in slowly but without too much affort. That checks out that fluid is is able to pass through the tiny compensation port in the front brake lever master cylinder.

You can do the same with the front centre pistons, which will check out the return through the compensation port in the rear master cylinder.

For the SMC compensation port, you need to check the movement of the rear outer pistons. These can be quite hard to push in because of the route that the fluid takes to get to the rear reservoir, and it has to pass through three compensation ports on the way.

So if you put a bleed tube on the front left centre piston bleed valve (ie the lower bleed valve on the front left caliper, push fluid into the tube with the brake pedal so that you dont introduce air, and then push in one of the rear outer pistons - making sure that you are not pushing the other outer piston out - then that will check whether fluid is returning properly through the two tiny compensation ports in the SMC. It will push fluid out through the bleed tube - which avoids having to push it through the delay valve and the rear master cyclinder - which you have already checked.

 

[oilspot]

Well I spotted something odd looking to this ST novice when I checked the wheel spacers. First off they were on the correct sides - which is good (even a blind pig finds an acorn now and then).

There appears to be a washer in between the left fork leg and the left spacer. I tried to snap a photo of left and right spacers. I may have to throw a shop light on it if this picture doesn't display well. The odd thing is, whether removing that washer would cause an interference with the hub hitting the fork?

I'll also share them with Larry too, when we speak. I will also update this thread if I find the cause of this situation.

 

[wizel]

It has no place there.
holm from germany

 

[jfheath]

No that isn't a washer - that is the axle. It has a shoulder - the right hand part, looking at the photo - the bit that goes through the fork leg on the right of the pic (the left fork leg) - has a larger diameter than the rest of the axle. That shoulder presses against the spacer - that it the bit that you think is a washer - which presses against the bearing, which presses against the distance collar inside the wheel, which presses against the other bearing which presses against the spacer on the right fork leg - the side with the ABS pulsar ring. When you tighten the axle bolt on the right hand side of the bike, it pulls the entire across clamping everything together against the right (clutch lever / pulsar ring side) fork leg. If the pinch bolts are tightened then the axle is prevented from pulling these components together.

However, if you don't have a massive allen key to hold the left hand side (clutch lever side) of the axle, to stop it from turning when you tighten the axle bolt. It is OK to push the axle through by hand and TEMPORARILY clamp the left side (clutch lever side) of the axle with the left fork pich bolts. This then also pulls the left fork across a little bit - so probably best to tighten the axle as much as you can until the other end starts turning, then clamp the left (clutch) side with the pinch bolts - then torque the axle bolt. Then undo the left hand pinch bolts (clutch lever side) and tighten the right hand pinch bolts (brake lever side). Then you bounce the forks, then tighten up the pinch bolts on the left (clutch lever) side.

Did you look at my animation link in post #7 ? Never mind I'll link it here - It's on YouTube so it isn't taking an extra space on Mellow's server!
Best viewed full screen. You can see the shoulder on the yellow axle as the axle is inserted through the hub

Those spacers are correct as far as I can see. Is the end of the axle at the left hand side flush with the face of the hole in the fork leg ? If it isn't then that will be pulling the brake caliper across a bit but the width of the exposed axle (your 'washer') looks about right.

 

[oilspot]

No that isn't a washer - that is the axle. It has a shoulder - the right hand part, looking at the photo - the bit that goes through the fork leg on the right of the pic (the left fork leg) - has a larger diameter than the rest of the axle. That shoulder presses against the spacer - that it the bit that you think is a washer - which presses against the bearing, which presses against the distance collar inside the wheel, which presses against the other bearing which presses against the spacer on the right fork leg - the side with the ABS pulsar ring. When you tighten the axle bolt on the right hand side of the bike, it pulls the entire across clamping everything together against the right (clutch lever / pulsar ring side) fork leg. If the pinch bolts are tightened then the axle is prevented from pulling these components together.

However, if you don't have a massive allen key to hold the left hand side (clutch lever side) of the axle, to stop it from turning when you tighten the axle bolt. It is OK to push the axle through by hand and TEMPORARILY clamp the left side (clutch lever side) of the axle with the left fork pich bolts. This then also pulls the left fork across a little bit. So you have to undo the left hand pinch bolts and tighten the right hand pinch bolts. Then you bounce the forks, then tighten up the pinch bolts on the left (clutch lever) side.

Did you look at my animation link in post #7 ? Never mind I'll link it here - Its on YouTube so it isn't taking an extra space on Mellow's server!
Best viewed full screen.

Those spacers are correct as far as I can see. Is the end of the axle at the left hand side flush with the face of the hole in the fork leg ? If it isn't then that will be pulling the brake caliper across

JF Heath Thanks.

Yes, I suspected it was the shoulder of the axle, and tried to update my post. Apparently, I walked away from the computer before I hit save EDIT - alas no harm done...

I usually leave pinch bolts finger tight on both sides, torque the axle to specification (holding both ends), then tighten the pinch bolts to specification.

The last time I did it was October-ish time frame when Larry encouraged me to realign the front forks. I ended up shaving just a hair off my fender so that the axle remained perfectly aligned when everything was attached. It made a big difference in stability of the bike once the front fork was "near perfect" alignment.

Getting ready to resume my study of the front end to see which side is grumpy. FWIW: the pistons were moving freely before and after cleaning, so I think my calipers are in reasonable shape.

 

[oilspot]

Just a quick update from today's investigation. Left and right seem to be dragging about equally. Rear is smooth, but I can hear the pads touching. I decided it wouldn't hurt to do another bleed of the system while I had things more or less easily accessible.

I used a jack stand to hold the SMC at the recommended angle and then as I was following along in the guide (ST Article on bleeding brakes) I gave the lines a few friendly taps here and there. Nothing really remarkable until I was doing step 3 or 4 with the SMC and pushed the piston in. It went in easily and produced quite a few bubbles. So I repeated this 2 or 4 times until there were not more bubbles. Everything feels better, but it could be my imagination. I think the bike goes faster when it's clean (LOL). Anyway, I was hopeful this might change behavior of the system but the fronts still drag a bit - maybe less but not a lot less. I can hear the pads scraping the disc in the rear but not creating a lot of friction. Still perplexed. I think everything is functioning correctly (except for the friction on the front wheel), but I don't have a good frame of reference.

Just to be clear, when folks install new pads on the front there is no noticeable drag on the wheel from the new pads? It doesn't require a 50-mile break in or anything like that?

 

[Kevcules]

Can you take a video of your front tire turning hard situation and post it here? I think you're fine now after all your checks.
It's normal to hear the pads touching when rotating the wheel.
If you go riding and your brakes function normally, especially after a good bleed and your rotors aren't hot, you're good.

 

[Obo]

@oilspot are the new brake pads OEM?