Uneven braking

[TWSTYS]

I know. This is the FJR forum. But a friend asked for help and there are so many knowing experts here. I thought it could not hurt to ask. His problem could apply to any bike.

He rides and older Ninja that started to get uneven braking at the front wheel. He removed the disks and had them ground. He also installed new pads.

If anything, the problem is worse.

The wheel is not bent. The ground disks shine like new.

I thought that maybe because the bike sat for an extended period of time, there may be some minor pits in the disk that formed under the pads while stored. But the disks shine like new.

Any ideas as to where the problem may be?

Thanks in advance!

Steve

P.S. This guy is a trooper. He road that Ninja, on a trip with me, 6,000 miles in less than 2 weeks last spring. Me on my comfy FJR1300.

 

[radman]

Pull the calipers apart, clean spotless, install new piston seals and lube sliding points with Silglyde-

Bleed well, and she'll stop like new if not better.

 

[jestal]

I am not familiar with the brake calipers on that bike but you want to make sure that the calipers can float freely if they are floating calipers and/or all the pistons are working correctly especially if they are fixed calipers with pistons on both sides.

I have seen several situations like you describe where the piston bores in the calipers had corroded and stuck the pistons so that not all the pistons were working equally. Any runnout in the rotor will then cause uneven braking especially with a fixed caliper system. He could have induced this inadventently with the new pads as new pads are thicker and will push the pistons back into the bores further than they were. If any water had accumulated in the caliper the bore may be rusted or corroded on the INSIDE of the piston and then when the piston is shoved back to put the new pads in the piston sticks in the gunk and hangs up. Usually just disassembling the pistons and caliper, cleaning and reassembling will solve the problem.

How were the rotors "ground". If they were simply blanchard ground on a flat grinder it will leave directional marks on the rotors. Not that that wont work but you want to install the two rotors so that the grinding pattern is opposite to offset the pulsing from the directional pattern.

Have you checked the thickness of the rotors all around the perimeter with a mic or calipers?? If the rotor is thicker on one area than another (from the grinding operation) it will cause that. The rotors have to be perfectly parrallel surfaces...i.e...be perfectly uniform thickness all the way around.

Are you sure it is not the tire? A tire can have assemetrical wear that only shows vibration under braking...see the earlier post about the front tire "cupping". If the brakes were used aggressively in the past it can cup the tire at each of the sipes or tread grooves and as this gets worse it will cause feedback into the bike during braking.

 

[madmike2]

Pull the calipers apart, clean spotless, install new piston seals and lube sliding points with Silglyde. Bleed well, and she'll stop like new if not better.

+1 as the first place to start. If the brakes have never been serviced and/or bled regularly, the chances of the calipers being filled with "ugly, black" splooge are very high and the possibility that there is "mondo" (copious?) amounts of road grunge around the pistons is practically guaranteed.

Time to buy a Clymer's for the Ninja and follow the diagrams and instructions.

 

[TWSTYS]

I knew someone would come through! I have given him a link to your replies.

Jestal, I do not know all of the answers to your questions and remarks except to say that the tires have been changed since the problem began. As Radman and you have suggested, it looks as though a good look at the calipers is in order. I never would have thought that calipers could cause that problem. I see now how they could.

I'll let you know how he comes out. He loves to do things himself, so it may take a week or two. He is one of those guys that works 60 hours a week.

We welcome any other suggestions too.

Thanks again!

Steve

 

[rideoc]

I have a friends Busa in my garage because of a similar problem. The right-side caliper was completely locked-up (which caused the left side pads to roast). I have them off and disassembled - what a mess. Ordered replacement seals from Suzuki for $28/per side. Of course ordered new pads too.

This is a relatively easy job once you're into it. Good luck.