Rear brake rotor much hotter than front - why?
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Stellar HDF Member
Joined: Feb 2014
Posts: 2,710
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From: Lethbridge, Alberta Canada
SOLVED! Rear brake rotor much hotter than front - why?
I was running a tire pressure measurement exercise today on my 2014 Breakout, and needed to check the front and rear tire pressure with the tires first cold and then hot.
This resulted in my touching the rear brake rotor while taking the "hot" tire psi measurement. The rotor was so hot, after 21 miles of highway driving with very little brake usage, that I couldn't keep my finger against it for more than a fraction of a second.
The front rotor was also warm, but definitely not nearly as hot as the rear rotor. There was a huge difference in temperature between the front and rear rotors.
I realize that all brake rotors get hot just from the drag of the brake pads, but (a) the rear rotor was VERY hot and (b) it was much hotter than the front rotor.
Is this normal, or did my bike come from the dealer with (a) a maladjusted rare brake master cylinder, or (b) a sticky rear caliper?
Jim G
This resulted in my touching the rear brake rotor while taking the "hot" tire psi measurement. The rotor was so hot, after 21 miles of highway driving with very little brake usage, that I couldn't keep my finger against it for more than a fraction of a second.
The front rotor was also warm, but definitely not nearly as hot as the rear rotor. There was a huge difference in temperature between the front and rear rotors.
I realize that all brake rotors get hot just from the drag of the brake pads, but (a) the rear rotor was VERY hot and (b) it was much hotter than the front rotor.
Is this normal, or did my bike come from the dealer with (a) a maladjusted rare brake master cylinder, or (b) a sticky rear caliper?
Jim G
Last edited by JimGnitecki; Aug 28, 2014 at 05:28 PM. Reason: Problem solved at last!!
Road Master
Joined: Dec 2010
Posts: 1,248
Likes: 1
From: Jacksonville, NC
If you weren't using the rear brake substantially more than the front brake then it's probably a sticky rear caliper. I had a sticky rear caliper on my old Fatbob. I would press the brake pedal and it would stay down until I lifted it back up with my toe. I ended up taking it to a dealer and they said the rear caliper had a bur or something in it and needed to be re honed or something like that. They fixed it under warranty. I'd take it to the dealer since it's still under warranty and have them take a look at it because you're right under normal usage the rear rotor shouldn't be hotter than the front. Particularly if you are breaking properly and getting most of your braking force from the front brake
Cruiser
Joined: Jun 2007
Posts: 191
Likes: 6
From: Portland Oregon
Definitely should go in for warranty. On one of my previous bikes I noticed at a stop that my front rotor was bright red, the caliper had clamped and not released all the way.
Actually had to bleed the brake fluid from the caliper to continue the ride, got lucky and didn't warp.
Actually had to bleed the brake fluid from the caliper to continue the ride, got lucky and didn't warp.
Tourer
Joined: Aug 2012
Posts: 482
Likes: 0
From: Vancouver
I also make sure to hose down the pads when washing bike. I had the same problem under warranty. Dealer service was very unhelpful, very could give too. Used the " our thirty year experienced mechanic measured some tolerance get out of here. Vancouver Canada dealer/distributor.
Put the bike on hoist, removed rear tire. Had a jig to mock the rotor. Checked operation, cleaned calliper/rotor. Case closed/problem solved.
Put the bike on hoist, removed rear tire. Had a jig to mock the rotor. Checked operation, cleaned calliper/rotor. Case closed/problem solved.
Road Warrior
Joined: Jun 2013
Posts: 1,781
Likes: 50
From: Louisville, KY
Do test ride and don't use the rear brake, ........ stop and compare the temperature of the rotors - I suspect that you'll find the rear rotor much cooler of that test ride.
I have recently started using my rear brake a lot less, and my rear tire wear is looking great.
I have recently started using my rear brake a lot less, and my rear tire wear is looking great.
Last edited by 1004ron; Aug 14, 2014 at 10:06 PM.
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Stellar HDF Member
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From: Lethbridge, Alberta Canada
And, after discovering this rear brake heat issue the first time today, I did some more testing, trying to avoid using the rear brake at all for several minutes before each stop on my route, and always got the same result: rear rotor much hotter than the front one, even though the front one was being used and the rear brake was not being used.
Jim G
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Club Member
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From: 40 miles Northeast of Indy..
don't know why.. but my rear tire has never spun Freely like my front and I go through rear pads every 15k vs 32k on my front and I use the front only 75% of the time.
and the rear rotor is alway hotter on mine also.. they just rub more...
and the rear rotor is alway hotter on mine also.. they just rub more...
Thread Starter
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Stellar HDF Member
Joined: Feb 2014
Posts: 2,710
Likes: 529
From: Lethbridge, Alberta Canada
I took my Breakout in to the local HD dealer today complaining about the rear brake rotor running WAY hotter than the front rotor.
Of course, the dealer tech said this is normal - on ALL the models of Harleys. In fact, he said that all the techs dread checking the rear tire pressure, especially on the touring bikes where they have to get around large exhausts and saddlebags, because they continually get burns on their hands from touching the brake rotors!
He confirmed that the rear rotors do run much hotter than the front rotors.
He had NO logical explanation for why.
I SUSPECT that he is simply repeating the official HD line, which was probably formulated when HD discovered that there is indeed some defect in the rear brake's ability to pull the pads back from the disk, but they don't want to do a recall (just as they didn't want to do a recall on early twin cam engine cam chain tensioners).
No way I am going to believe this is "ok". But, since HD denies there is a problem, I guess that means that I have to figure out the problem myself and fix it myself - they won't treat it as a warranty issue. Unless of course the darn brake finally at some point locks the pads onto the wheel. At that point, I'll need to relieve the hydraulic pressure via the bleed valve, and ride to the nearest HD dealer using the front brake only I guess. THEN, I would challenge them to say "this is normal", and I will insist on a warranty repair.
Jim G
Of course, the dealer tech said this is normal - on ALL the models of Harleys. In fact, he said that all the techs dread checking the rear tire pressure, especially on the touring bikes where they have to get around large exhausts and saddlebags, because they continually get burns on their hands from touching the brake rotors!
He confirmed that the rear rotors do run much hotter than the front rotors.
He had NO logical explanation for why.
I SUSPECT that he is simply repeating the official HD line, which was probably formulated when HD discovered that there is indeed some defect in the rear brake's ability to pull the pads back from the disk, but they don't want to do a recall (just as they didn't want to do a recall on early twin cam engine cam chain tensioners).
No way I am going to believe this is "ok". But, since HD denies there is a problem, I guess that means that I have to figure out the problem myself and fix it myself - they won't treat it as a warranty issue. Unless of course the darn brake finally at some point locks the pads onto the wheel. At that point, I'll need to relieve the hydraulic pressure via the bleed valve, and ride to the nearest HD dealer using the front brake only I guess. THEN, I would challenge them to say "this is normal", and I will insist on a warranty repair.
Jim G
