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The_Menace 02-02-2016 11:54 PM

Suggestions on brakes
 
Ok, so I picked the bike up Saturday and noticed on the way home when I would use the front brakes it would try to shake and hop on me. I read that the steering head bearing could cause it, so I snugged it up a hair not much at all. Problem was still there So, I got the front end up in the air and did a runout on the rotors. The left side o.d was 9.5 thousandths out, I.d. was 12.5 thousandths out. Right side O.d. was 3.5 thousandths, I.d. is 3 thousandths. Not sure if I should change both out or just the left side and see how that does, any opinions ? The left rotor is dragging in the caliper pretty bad. Have not pulled the pads to see what shape they are in yet.

jondog9 02-03-2016 3:12 AM

Re: Suggestions on brakes
 
What torque do you have on the steering stem nut? That's kind of important.

Did you check for runout on the rim?

If you're sure the front axle was tightened in the right sequence, and no run-out on the rim, then you might have a problem with the disc's or steering stem bearings.
I believe the max run-out on the disc's is 0.30 mm's. Don't know what that translates to in thousands of inch.

If you don't already know....
Front Wheel Installation

With the thick spacer in the right side of wheel, thin spacer in the left, place the wheel between the forks. Slide the axle through wheel from the left side.

Install axle bolt on right side and torque to 43 ft/lbs.

Tighten right fork axle pinch bolts to 16 ft/lbs. (192 in/lbs.)

Install brake caliper bolts and torque to 22 ft/lbs. (264 in/lbs)

Put bike on the ground, hold front brakes, pump the forks up and down to seat the axle.

Make sure index line on axle lines up with fork leg outer surface. Left side.

Tighten left fork axle inch bolts to 16 ft/lbs.

Gunk 02-03-2016 4:05 AM

Re: Suggestions on brakes
 
You're right, I didn't use that sequence when I fitted a spare set of wheels and the front brakes rubbed. I did some research before refitting my repainted wheels, used the method above and it aligns the wheel in the forks.

fj1200rj 02-03-2016 6:46 AM

Re: Suggestions on brakes
 
Quote:

Originally Posted by Gunk (Post 1203758)
You're right, I didn't use that sequence when I fitted a spare set of wheels and the front brakes rubbed. I did some research before refitting my repainted wheels, used the method above and it aligns the wheel in the forks.

:plus1:LOL, I think all of us, being guys with mechanical backgrounds and manuals to closely resembling "instructions" (something no self respecting guy uses), don't always reference the manual for "simple" tasks we've done dozens of times on dozens of bikes. Now, back to working on aircraft.

BenelliBlade 02-03-2016 7:00 AM

Re: Suggestions on brakes
 
Quote:

Originally Posted by The_Menace (Post 1203754)
The left rotor is dragging in the caliper pretty bad. Have not pulled the pads to see what shape they are in yet.

First thing to do is take off the calipers and see if any pistons are seized, dragging brakes are a very good sign that at least some pistons are.

Free off the calipers, replace any damaged seals/pistons etc. and see if the vibration is still present. If so then the discs are suspect.

FWIW, my RRX suffered from terrible brake judder when I got it, it almost made the brakes unusable at low speed. There was barely any disc run out, when measured with a DTI, but the problem was down to a thickness variations of once disc, there was a 'thin' area in the disc with only a few thousands of an inch difference. New discs and pads and the brakes were perfect.

The_Menace 02-03-2016 8:17 AM

Re: Suggestions on brakes
 
Quote:

Originally Posted by jondog9 (Post 1203756)
What torque do you have on the steering stem nut? That's kind of important.

Did you check for runout on the rim?

If you're sure the front axle was tightened in the right sequence, and no run-out on the rim, then you might have a problem with the disc's or steering stem bearings.
I believe the max run-out on the disc's is 0.30 mm's. Don't know what that translates to in thousands of inch.

If you don't already know....
Front Wheel Installation

With the thick spacer in the right side of wheel, thin spacer in the left, place the wheel between the forks. Slide the axle through wheel from the left side.

Install axle bolt on right side and torque to 43 ft/lbs.

Tighten right fork axle pinch bolts to 16 ft/lbs. (192 in/lbs.)

Install brake caliper bolts and torque to 22 ft/lbs. (264 in/lbs)

Put bike on the ground, hold front brakes, pump the forks up and down to seat the axle.

Make sure index line on axle lines up with fork leg outer surface. Left side.

Tighten left fork axle inch bolts to 16 ft/lbs.

I haven't checked the run out of the rim yet, I will try to do that this evening. As far as torqeing the head bearing, I do not have a socket that will fit. What I did was use a spanner and took out the slack until snug, then tightened 1/8th of a turn. I will pull the wheel and re-install just to make sure it is correct.

The_Menace 02-03-2016 8:21 AM

Re: Suggestions on brakes
 
Quote:

Originally Posted by BenelliBlade (Post 1203766)
First thing to do is take off the calipers and see if any pistons are seized, dragging brakes are a very good sign that at least some pistons are.

Free off the calipers, replace any damaged seals/pistons etc. and see if the vibration is still present. If so then the discs are suspect.

FWIW, my RRX suffered from terrible brake judder when I got it, it almost made the brakes unusable at low speed. There was barely any disc run out, when measured with a DTI, but the problem was down to a thickness variations of once disc, there was a 'thin' area in the disc with only a few thousands of an inch difference. New discs and pads and the brakes were perfect.

I will try this when I get the wheel pulled, I'm hoping it's something easy and simple. Really don't want to dump $400 on rotors :eek: this one is pretty bad at low speed too, 50mph up is not horrible but, still feel like I have to baby them.

Gunk 02-03-2016 10:04 AM

Re: Suggestions on brakes
 
Quote:

Originally Posted by fj1200rj (Post 1203761)
:plus1:LOL, I think all of us, being guys with mechanical backgrounds and manuals to closely resembling "instructions" (something no self respecting guy uses), don't always reference the manual for "simple" tasks we've done dozens of times on dozens of bikes. Now, back to working on aircraft.

As I'm a strictly amateur mechanic, I tend to work in a very prescriptive and methodical way, I like the comfort of following instructions rather than guessing and winging it. especially when bolting a motorcycle back together.

Spaz 02-03-2016 10:15 AM

Re: Suggestions on brakes
 
Caliper off, pads out, drop a ring spanner in between the pistons, and pump them out, you'll see pretty quickly which ones are seized, keep pumping till they're all tight on the spanner. Toothbrush and plenty of brake cleaner should clean up the pistons as much as they need to be, repeat on all calipers.

Gunk 02-03-2016 11:35 AM

Re: Suggestions on brakes
 
Quote:

Originally Posted by Spaz (Post 1203779)
Caliper off, pads out, drop a ring spanner in between the pistons, and pump them out, you'll see pretty quickly which ones are seized, keep pumping till they're all tight on the spanner. Toothbrush and plenty of brake cleaner should clean up the pistons as much as they need to be, repeat on all calipers.

A couple of sheets of balsa wood is better, kinder to the pistons.

The_Menace 02-03-2016 11:39 AM

Re: Suggestions on brakes
 
Quote:

Originally Posted by Spaz (Post 1203779)
Caliper off, pads out, drop a ring spanner in between the pistons, and pump them out, you'll see pretty quickly which ones are seized, keep pumping till they're all tight on the spanner. Toothbrush and plenty of brake cleaner should clean up the pistons as much as they need to be, repeat on all calipers.

I'm keeping my fingers crossed that this is all it is. Hopefully will have time to do it tonight.

The_Menace 02-03-2016 11:40 AM

Re: Suggestions on brakes
 
Quote:

Originally Posted by Gunk (Post 1203780)
A couple of sheets of balsa wood is better, kinder to the pistons.

I have some thin underlayment and plexiglass that would work pretty good.

Spaz 02-03-2016 11:51 AM

Re: Suggestions on brakes
 
Quote:

Originally Posted by Gunk (Post 1203780)
A couple of sheets of balsa wood is better, kinder to the pistons.

No it's not, the pistons will crush it, and probably pop out even, ring spanner is absolutely fine., tried and trusted by many.

954Kevin 02-03-2016 12:02 PM

Re: Suggestions on brakes
 
Quote:

Originally Posted by Gunk (Post 1203780)
A couple of sheets of balsa wood is better, kinder to the pistons.

i actually use a metal file tacoed inside a rag. lol im careful not to crank down on the lever once they have all reached the file. its kinda convenient having the rag right there and the file is a nice uniform thickness.

ill add tho that if cleaning doesnt free them up so they all extend at a fairly even pace without sticking, its likely they will need new seals. once you pull a caliper off you should always clean the pistons before pushing them back into the calipers. this will go a long way in protecting those seals from damage.

i usually replace my piston seals every 2-3 years or as needed. those seals are designed not to swell with exposure to brake fluid but they do still sponge up small amounts of it over time. causing them to expand ever so slightly but enough to affect performance or cause a sticky piston.

if the rotors are bent but still meet thickness requirements you can have them straightened for a fraction of the cost of new. i sent mine along with my front rim to https://www.facebook.com/WillsRimRepair/ in north carolina. he does awesome work. the rotor straightening is 15$ each plus shipping. he will straighten them to better than factory tolerances.

as mentioned id pull everything off and clean them well n prob replace the pads while i was in there. seals too if they continued to stick. id pull the disks off the wheel too and clean the buttons between the disk ad the inner hub so they are free moving as well. along with the mating surface between the rim and the rotors n recheach runout just to be sure. people often overlook the buttons but they need to be clean and free moving as well. then id do a fluid flush. put it all back together being sure to put the wheel back on using the proper install order n see how that worked out.

brakes are easily the most important system on a bike for obvious reasons so its my advise to take no shortcuts in their service. thats a system that has to be 100% before id ride a bike.

jondog9 02-03-2016 12:15 PM

Re: Suggestions on brakes
 
Does anyone here have a problem with using WD40 to clean the caliper pistons and seals? That's what I've always done, seems to work good for me. I've been a little nervous to use brake cleaner, fearing it would cause a bit of drying of the seals.


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