Uneven Brake Pad Wear

[Blue Dave]

I have attached a picture of the brake pads on my '07 Apex GT. The brake pad on the outside of the disc has about 1 mm of pad remaining but the inside pad still has about 5 mm of pad remaining.

The sled has 7200 miles on it and the brakes have always worked very well. The caliper is fixed in position (non floating) however all four pistons should share the same hydraulic pressure which should create even wear on the inside and outside pad.

I replaced the pads with new ones and I will watch the wear and perhaps swap them with each other if I see the uneven wear starting again. Has anybody else experienced uneven brake pad wear? Any theories on why this happens?

 

[Kaz]

I had a similar experience on my 2007 Apex, just installed one new pad as the other side was hardly worn. Still have the other new spare pad hanging on the wall, 20,000k on the 07.
Kaz

 

[Blue Dave]

Perhaps I will start rotating my brake pads every year, LOL!

 

[Trucker]

looks like the one side is stuck.

 

[Blue Dave]

All four pistons move easily. To install the new pads I pushed all four pistons all of the way back in using just my thumbs.

 

[sherlock29]

Both my apex's did this... same wear, same way... i just replaced and moved on....

But yes... in theory, they shouls wear the same.

 

[YammyRX1]

Just a guess but there is an adjustment for the parking brake that might make the caliper favour one side when brakes are at rest. Maybe over time one set of pads ride the caliper very slightly while the other side doesn't touch just by design?

 

[Blue Dave]

The parking brake caliper is completely separate from the main brake caliper so I can not see how it could cause this.

Since others have experienced the same issue I guess that I will just keep an eye on it and swap the inside and outside pads with each other when I start to see uneven wear again.

 

[TBay Sledhead]

Brake fluid goes into that side of the caliper first therefore applying that side first cause slightly more wear. That's my theory and I'm sticking to it. Mine is the same way. Switched mine around after 15,000 km.

 

[YammyRX1]

The parking brake caliper is completely separate from the main brake caliper so I can not see how it could cause this.

Since others have experienced the same issue I guess that I will just keep an eye on it and swap the inside and outside pads with each other when I start to see uneven wear again.

You're right, I should have looked at it again before replying. I just remembered having to compress that spring to measure the pad clearance. New theory- sleds south of the equator wear inside first LOL. Would side thrust from the clutch have any affect?

 

[woolyviper]

lube the bolts and sleeves that mount the caliper - it's not sliding to equalize the pressure on the pads.

 

[Blue Dave]

Actually the brake fluid enters on the inboard side of the caliper and it shouldn't matter anyway since all four pistons should see the same pressure. I did not see any bushings or sleeves that would allow the caliper to float and self center. My recollection is that it was bolted in a fixed position.

I just noticed that after installing the new pads that the pistons on the outboard side are pushed in more than the pistons on the inboard side which would indicate that the caliper is not perfectly centered over the disc as you can see in the picture.

 

[TBay Sledhead]

Yes but it doesn't matter that the brake rotor is not centered because the brake pads will extend to the rotor even if one side has to go out farther than the other. then they will stay in that position and the only thing that pushes them back from the rotor is it's movement on the shaft. I think that because the inside of the caliper see's fluid first it is the first to react, therefore more wear.

 

[Blue Dave]

Yes but it doesn't matter that the brake rotor is not centered because the brake pads will extend to the rotor even if one side has to go out farther than the other. then they will stay in that position and the only thing that pushes them back from the rotor is it's movement on the shaft. I think that because the inside of the caliper see's fluid first it is the first to react, therefore more wear.

I think that you are somewhat correct in saying that it shouldn't matter in theory if the caliper is not perfectly centered over the rotor (to a certain degree) because you have pistons on both sides of the caliper making it inherently self centering even though the caliper itself is fixed. However I would also say that it is desirable to have the caliper perfectly centered over the rotor because I do believe that to a certain extent the pistons will always try to equalize their displacement which will cause slightly more constant drag on the side of the rotor that is pushing the pistons back more to compensate for the rotor not being perfectly centered. In my case it is the outside pad which is pushing the pistons back more than the inside pad because of the slight off center mounting of the caliper over the rotor.

However your theory on the inside pistons moving first because of where the fluid enters does not make sense because it was my outside pad that was much more worn, not the inside pad. I realize that I am beating this to death but I am anal with OCD and I am bored right now waiting for snow! It does bother me that my rotor is not perfectly centered in the caliper. On my sled the rotor needs to move about 1 mm towards the chain case to be perfectly centered in the caliper. I may play around with some shims on the rotor shaft to make it perfectly centered in the caliper. Now that I have new pads installed it will be a good test to see if being perfectly centered eliminates the uneven wear going forward. However it will probably take more than a season to know if it made a difference and by then hopefully I will be trading it in for the new factory boosted Apex from Yamaha....LOL!

 

[sleddog66]

Brakes??? I didn't know that these 4 strokes had brakes. LOL