New pads and rotor, really tight clearance?

mwc

mwc

Sombiscuit
I just put a set of 17s on my RMX250, and I'm just getting some finishing touches done. Got the pads in today and it was a really tight squeeze getting the caliper back onto the rotor. The pads were almost too big to get it all together, after compressing the pistons. Finally got it all together but the pads are dragging on the rotor big time, it almost takes 2 hands to spin the wheel. I know the clearances between new rotors and pads can be tight but this seems excessive. Everything was pretty nice with the old pads, a tiny bit of drag but not enough to concern me much.

Should I ride it around the block once it's all together tomorrow and see how it feels after, or does this seem like more than usual resistance?

Thanks in advance for any help
 
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afm199

afm199

Well-known member
I'd keep looking . IF it takes that much force to turn the wheel, it's just going to heat up the rotor/fluid and quite possibly lock the brakes. I've had it happen.
 
mwc

mwc

Sombiscuit
I've looked, just not sure what else to look for. The caliper is all good, it's compressed almist flush with the caliper body, with the MC reservoir cap off. I did just switch wheels/wheel spacers/caliper bracket but it was as hard to get the caliper on the rotor as is it to turn the wheel and everything lines up, so I feel like it's all in the thickness of the pads.
 
Cincinnatus

Cincinnatus

Not-quite retired Army
How much brake fluid is in the reservoir? Maybe bleed some of that out and see if you can get the calipers some more free space.
 
mwc

mwc

Sombiscuit
The fluid is reasonably full, it leaked a quite a bit onto the rag I had wrapped around the MC as I was compressing the pistons.

The spacers are right, everything was fine mocking it up with the old pads. There's nothing dragging but pads.
 
afm199

afm199

Well-known member
mwc said:
The fluid is reasonably full, it leaked a quite a bit onto the rag I had wrapped around the MC as I was compressing the pistons.

The spacers are right, everything was fine mocking it up with the old pads. There's nothing dragging but pads.
Click to expand...

If it pushed out fluid it's too full/ take some out. And replace it while you are at it.
 
Mr. White

Mr. White

Well-known member
Too much BF isn't good, but if the pads are dragging with the reservoir cap off, then having the BF over filled probably isn't the problem.

What type of calipers are they? "Floating" type, "fixed" type, etc? Can you tell if only one pad in the caliper is dragging (inner or outer), or are both dragging equally?
 
mwc

mwc

Sombiscuit
I'm at work but I'll check when I get home, but I know its rubbing on the piston side of the rotor, I'll check the wheel side and see if the rotor looks worn.

I believe it's a floating caliper, it's an RMX but they use 2 piston RM250 brakes up front.

Getting the rear wheel back today from having the offset adjusted. If all is well with chain/tire clearance then the only issue will be these front pads
 
planegray

planegray

Redwood Original
Staff member
Mr. White said:
Too much BF isn't good, but if the pads are dragging with the reservoir cap off, then having the BF over filled probably isn't the problem.

What type of calipers are they? "Floating" type, "fixed" type, etc? Can you tell if only one pad in the caliper is dragging (inner or outer), or are both dragging equally?
Click to expand...

+1

floating types can get cocked with sticky pins. I use a rubber mallet to bang on the pins, or wood to push on them, to let the caliper sit correctly.

Did the brake pistons retract far enough back into the caliper to allow the metal part of the pads to sit flush against the caliper ? One of the pistons may be stuck, if not.

wrong pads ?
 
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mwc

mwc

Sombiscuit
planegray said:
+1

floating types can get cocked with sticky pins. I use a rubber mallet to bang on the pins, or wood to push on them, to let the caliper sit correctly.

Did the brake pistons retract far enough back into the caliper to allow the metal part of the pads to sit flush against the caliper ? One of the pistons may be stuck, if not.

wrong pads ?
Click to expand...

The pistons were sticking out maybe 1/16" from flush, but didn't seem to get in the way of the pads sitting where they need to.

I don't think the pads are wrong, they match the old ones in every aspect but thickness at the pad material.

stangmx13 said:
how clean were the pistons before u pushed them back in?
Click to expand...
They were pretty clean but not sterile, should I try cleaning em really well and see if I can get any more compression out of em?

Thanks for all the input guys it's much appreciated
 
planegray

planegray

Redwood Original
Staff member
mwc said:
The pistons were sticking out maybe 1/16" from flush, but didn't seem to get in the way of the pads sitting where they need to.

I don't think the pads are wrong, they match the old ones in every aspect but thickness at the pad material.


They were pretty clean but not sterile, should I try cleaning em really well and see if I can get any more compression out of em?

Thanks for all the input guys it's much appreciated
Click to expand...

Yeah, you should clean the pistons off before you push them in (if there's not a dust boot protecting them). I use the old pads (as protection) and push the pistons all the way in, before reassembly.
 
Mr. White

Mr. White

Well-known member
I really doubt the caliper pistons are your issue, since the caliper was really difficult to install with the piston compressed (almost) all the way in.

My armchair mechanic guess:

1: the caliper bracket is wrong or installed wrong, or the wheel spacing is wrong.
2: if a floating caliper, the guide pins are stuck or tightened too much. Knowing if both pads are dragging is important.
3: the pads are wrong - too thick.
 
fast4d

fast4d

Well-known member
I had this issue when I tried organic compound pads on my ZRX.

OEM uses HH compound.

when I got my organic pads I notice they were thicker than OEM/aftermarket HH.
 
ST Guy

ST Guy

Well-known member
Make sure you got the right pads. I once put pads in my 4Runner and they were just a bit too tight. Turned out the parts guy gave me the wrong ones. They were identical in all respects except a slight difference in thickness.
 
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