Hot rotor

[k3eaxk3eax]

Here's one for you to mull over: Using a non-contact thermometer I discovered that the passenger side roter is running 20F. hotter than the driver's side. Also, the outboard pad on the passenger side was somewhat more worn. All this suggested that the slides and pins on the passenger side needed attention or the caliper's piston was not retracting, or yet still the flexible hose to caliper had deteriorated internally and was preventing an adequate return flow back to the master cylinder. I greased and cleaned the guides/pins, replaced the caliper and hose and the temperature differential remained.

I've yet to place a dial indicator on the roter to test for warpage. However, since only the outside pad showed somewhat more wear, I doubt that the roter will show warpage.

I'd be interested to hear form others on this.


Al in Philadelphia

 

[doorgunner]

My Harley D. calipers wear the pads unevenly...one pad is always thinner when it's time to replace them.

But the "problem" is easy to see on the front-wheel caliper.....whether by design/rotation of the earth/or whatever......the same pad always makes contact first.

As for the heat difference....maybe the wheel bearings are tighter/have less grease on the hotter rotor? 20* isn't a whole lot considering how hot they get in traffic....


(then...there's that "maybe the sun was shining on the hotter caliper more.......LOL")

 

[k3eaxk3eax]

Sorry Doorgunner, I can't agree with most of what say. The pads on a floating caliper in proper working order should make contact/pressure equally/simultaneously. I would suggest that you look at your Harley carefully as you apparently have a problem.

 

[kcm1582]

Actually Doorgunner is right. On a floating caliper system the pad on the side of the piston will make contact with the rotor first then the caliper will slide on its guide pins and engage the other pad. Since the pads float only a few thousandths of an inch away the difference is unnoticeable, and there is very little extra pad wear on the inside pad.

BTW, most Harleys use a solid mounted 4 piston caliper(2 pistons on either side), and the piston with the least friction against the seal will slide first, causing that pad to engage the rotor first.

 

[adsm08]

OK, speaking as a dealership tech who sees hundreds of sets of brakes in a month, that is normal.


One pad almost always wears out faster. About 90% of them have a 1/32 difference inboard to outboard, and it's usually the outboard that is lower. So unless you have about 6/32 left on the inboard and the outboard is shot, your system is working properly.

 

[k3eaxk3eax]

Allowing the question of wear to drop , I'm still unable to explain the temperature difference of 20F. between the passenger and driver-side.

 

[kimcrwbr1]

+1 on the wheel bearings pull them both apart clean them good and inspect them. Repack the bearings and put in new seals. A quick check is to grab the top of the wheel you should feel a slight clunk evenly on both sides buy wiggling it by hand.

 

[kunar]

+1 on the wheel bearings pull them both apart clean them good and inspect them. Repack the bearings and put in new seals. A quick check is to grab the top of the wheel you should feel a slight clunk evenly on both sides buy wiggling it by hand.

there should not be ANY play in the wheel bearing when it is tightened to spec.

 

[kolton]

Damn man, I'm sorry, but this is some funny stuff. Its a 91ranger! Not a freakin indy car science experiment! Just replace the pads, get drilled and slotted rotors and new wheel bearings if your that worried about a heat change! Lol the funniest part was your reply to Doorgunner! He may be crazy, but he knows his stuff. He's got the ride to prove it too.

And agreed, there should be NO movement in the tire when the wheel bearings are set to spec.

 

[adsm08]

Allowing the question of wear to drop , I'm still unable to explain the temperature difference of 20F. between the passenger and driver-side.

Was the passenger side facing the sun? Was the drivers side in the shade? Did you sneeze at it funny?

Those brakes get hot hot. 20*F is an insignificant difference if you have been driving it. Going through a right hand turn while braking will produce that difference.

 

[cocoasranger]

Here's one for you to mull over: Using a non-contact thermometer I discovered that the passenger side roter is running 20F. hotter than the driver's side. Also, the outboard pad on the passenger side was somewhat more worn. All this suggested that the slides and pins on the passenger side needed attention or the caliper's piston was not retracting, or yet still the flexible hose to caliper had deteriorated internally and was preventing an adequate return flow back to the master cylinder. I greased and cleaned the guides/pins, replaced the caliper and hose and the temperature differential remained.

I've yet to place a dial indicator on the roter to test for warpage. However, since only the outside pad showed somewhat more wear, I doubt that the roter will show warpage.

I'd be interested to hear form others on this.


Al in Philadelphia

If one of the rotors is thicker than the other ( usually from being resurfaced or bought from different places) then you are going to have a temperature difference. A difference in the stiffness of the neoprene piston boots and/or a stiff piston due to sludge in the caliper bore also will make one side work harder than the other. In any case 20 degrees F is no big deal when it comes to disk brakes.

 

[feellnfroggy]

Rotor thickness, sun angle and turn counts are all good reason for temp difference, but the one I have to agree with would be the amount of right hand turns, most people drive a consistent route day in/day out. Usually with more turns one way then another.


Also consider an alignment, this and the wheel bearing issues will def cause problems.

 

[k3eaxk3eax]

Coupla-things. A floating caliper's pads SHOULD in theory wear evenly. If they do not, with no other problems present it's because of a difference in the condition/lubrication of the slides. If you work a dealership and see many with uneven wear it's because very few, to none, have the slides and pins lubed between brake pad replacements.

The temperature difference with the significant uneven pad wear is understandably troubling. So, please don't belittle my concern

The responses that suggested the temp differences could be resulting from difference in roter thickness were welcomed as I had not thought of that possibility. My records though show that I replaced them both at the same time and neither had been subsequently turned.

I haven't checked the bearing preload or of course checked for plat as yet. I'm hoping to find that is the cause rather than warpage.

Thanks to all those who took the time to respond.

Al, A.S.E. Master Auto Tech./L1- Advanced Engine Performance Endorsed

 

[kcm1582]

The temperature difference with the significant uneven pad wear is understandably troubling. So, please don't belittle my concern

Well let me ask a few questions. When you say there is a 20 degree difference between rotors what are the actual temps? Same with the pads, what are their actual thicknesses?

Coupla-things. A floating caliper's pads SHOULD in theory wear evenly. If they do not, with no other problems present it's because of a difference in the condition/lubrication of the slides. If you work a dealership and see many with uneven wear it's because very few, to none, have the slides and pins lubed between brake pad replacements.

You are right, in a perfect world where the operation of a caliper is frictionless then yes they should wear evenly. However in the real world there is friction between the pads and the slides as well as the caliper and the slide pins, and yes its still there even when they are all properly greased.

 

[k3eaxk3eax]

I beleive that most have never used a non-contact thermometer on roters; their use is an excellent diagnostic tool. Because so few have used one, the temperature differential question that I posed is one that few readers here have encountered.

These devices have come down in price to the point where one can be had for as little as $25 form Harbor Freight Tools.

The differential that I've noticed runs constantly at a 20F. Typical the temps are 120F and 140F.


Al, A.S.E. Master Auto Tech./L1