New Pad Blues.....Advice needed

Greetings from VA:
Just back from a great ride from VA to VT!
Purchased this awesome 2004 bike last November to keep my old Guzzies in line. Been upgrading and replacing the basics as needed, and it was time for the front brake pads to be replace and system bled. Previous owner said he did all the work, which has made me somewhat nervous.

So...decided it was time to change pads....Started with rider front left....pulled old out, cleaned pistons with nylon brush and arisol brake cleaner. pushed pistons back in, inserted new OEM, checked fluid, and off for 1 mile test ride......back in the garage and the left rotor was hot....not 3rd or 2nd degree hot, but not warm.....right rotor cool compared, even though also used.

Pulled out pads, extended pistons, vigorous cleaning with same brush and cleaner, cleaned up, coated pistons with silicon grease, cleaned off excess, inserted OEM, and off for a check ride.....same result. SOOOOO, put original pads back in......check ride.....and still a hot rotor.

So, what gives? Have I buggered the seals? Is there a settling in period after work is done on these calipers? I've done Brembos many times and quick jobs most of the time. But this is the first time with the Nissins(?). Am I missing something or did I do something......I will say that with the pistons pushed all the way in, it was a bloody tight fit for the OEMs. Also, even with the pads out on the left and the wheel off the ground, when spun by hand, I can hear the right pads dragging.

Do I ride keeping a keen feel for the temperature, pull both calipers and do total rebuilds as per manual myself, or pay the mechanic to do it (safety first, but I am a Scot).

Thanks for reading.....any advice will be taken seriously.....safty first, even at 100 mph.....
Ian

I've had my front brakes start to lock up before. The brake Proportional Control Valve was not bled and the brake fluid was contaminated. When I bled it, the fluid came out black. Many shops forget to flush this valve. Additionally the Secondary master cylinder (SMC) was seized. After cleaning the SMC up and packing the boot with break grease and flushing the break line the front brakes freed up.

Check out the excellent articles on bleeding brakes and replacing the break pads. There is a sequence to the bleeding and you have to tilt the left brake caliper 15 degrees.

Also don't use brake cleaner, it damages the seals. Use DOT4 brake fluid to clean calipers and pistons. Be sure you have the pistons pushed all the way in before inserting the pads. before I push in the pistons I remove some brake fluid from the master cylinder and leave the cap off.

I had an 84 SP1000 that I pretty much completely rebuilt. I don't remember any secondary master cylinder like the ST 1300 has. Whenever I do brakes on my cars or bikes, I flush and bleed the whole system - brake fluid (hyd clutch too) is hydroscopic and after replacing calipers on my T3, I decided it was cheaper to flush the system every couple of years than buy new ones. Oh, and, yes I did try to rebuild them. They were pitted and corroded inside the caliper to the point simple honing would not have been enough.

I echo on the brake fluid and rubber seals are not compatible. The brake fluid will cause the rubber to swell and deteriorate, so you might have damaged the boots. On my old bikes if the pistons did not move smoothly when I pulled the brake lever (with no pads in the caliper) and go back in with no hint of sticking, I pulled the rubber boot and checked to see what the pistons looked like.

I also replaced all the brake lines on my Guzzi's with stainless braided lines. After spending a LOT of time fruitlessly trying to get the last air bubble or two out, I bought a Miteyvac system. This worked well. Since then I've come up with a home made vacuum system to continuously suck the fluid through the system - there is no going back now.

I would not ride if the pads are dragging. This is not normal. And too much heat might warp the disk - and that would be expensive. Both rotors should be running the same temp until you hit the brakes. One side up front will brake when you hit the foot pedal, so checking the temp after you stop will yield different temps no matter how you try to brake. Maybe coast to a stop uphill?

Assuming ST1300 from the post, but not sure.

If that is the case, the brakes are linked and a complete system. Do not try to do just a partial change and test. Any changes require a complete run through, flush and cleaning. If you don't have a ST1300 service manual be sure to read the sticky on the proper procedure regarding brake fluid flushing.

Air trapped in your SMC will not affect the front brakes, but it will for sure affect the rear brakes. Again, this is part of the procedure, you need to do a complete run through on a ST1300 brake system. The fronts are paired and linked via the SMC to the rear, but it is a separate fluid.

I agree with Reginald that you should not use brake cleaner on the pistons. Nor do I see the need for coating the pistons with grease. Just clean them with the old brake fluid before pushing them back into their home.

Also, did you break the top of the master cylinder open before and after swapping the pads? Pushing the pistons in forces the fluid back up and it needs to go somewhere, if the previous owner topped off the fluid after the last time the pads were changed you have too much fluid in the system. Again, follow the procedure. One step at a time and all will be right with the world.

Good that you are doing your own service, most dealers are unfamiliar with the bike and will flub the proper procedure. But follow the steps and you can keep the bike in tip-top shape.

motoguzzian said:

... cleaned pistons with nylon brush and arisol brake cleaner ...

Click to expand...

Check the label on what you used to be sure, but many brake parts cleaners dissolve greases and damage rubber. The only time pistons should be cleaned with a brake cleaner are when they're out of the caliper, and after that they should be coated with brake fluid before installation. Brake fluid and a toothbrush work great for cleaning the pistons during pad changes, and that's probably what I'd use during a rebuild, too.

... coated pistons with silicon grease, cleaned off excess ...

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Same as above. It's very likely that the seals kept it out, but residual grease on the pistons could end up behind the seals and in the brake fluid, which isn't something you want.

I will say that with the pistons pushed all the way in, it was a bloody tight fit for the OEMs.

Click to expand...

Tight's not unusual, but bloody tight isn't right. The caliper should require some pressure to slide on over the rotor, but if it's a struggle, check for something not being seated properly.

Also, even with the pads out on the left and the wheel off the ground, when spun by hand, I can hear the right pads dragging.

Click to expand...

A very slight pad drag is par for the course.


BTW, your IP says you're in my neck of the woods, so if you need an extra pair of eyeballs, drop me a PM.

--Mark

Am I reading this correctly, that you went for your 1-mile test ride after changing only the left front pads? If so why would one do that? I've no idea what the performance of the brake system would be doing that.

One other possibility if you bought sets for all around: the OEM rear pads are thicker than the fronts but have the same backing plate.

--Mark

Thank you all for the input!
I hope that I:
1. Didn't bugger it all up with (A) Brake Cleaner (B)Damaging the seals when pushing the pistons back in (C) Applying the silicon grease to the pistons
2. Inserted the correct pads (pretty sure they are correct OEM and not the rears, but will double check and...no heat shield) without damaging the springs
3. Can follow directions.......my wife says "not likely"...but I'll give it a try!
Sorry, no base line on temp before starting working on the pads.....good point though and one to remember....."get a base line to go back against" on even the most basic. It is very likely that the fluid was over filled, although I had pulled fluid out when I did the second cleaning. I had planned on doing the left first, then the right, as both were on the bike when I got it (7K ago). I tend to do things in stages. I did have the rear just replaced about 2k when I had the local shop replace the rear bearings and new tire put on (they have a good rep and the service mgr is a friend of a friend).

Thank you to Mark for the offer.....If I hit a road block, I will send out a SOS. It will be a few days before I can get back to the ST and will update.....Thank you all once again!......Ian