Hot rear brake disc. How hot is too hot?

[London_Phil]

Hi All

Bit of a frustrating issue, looking for some suggestions.
Rear brake disc seems excessively hot after a run.
Kagizume disc fitted last season (don't panic JayDub) overhauled caliper, and fitted ebc pads. All well lubed and moving freely, pistons, sliders etc etc.
Rear brake disc gets too hot to touch. Assume its bedding in, but after nearly 1K, its still like it.
Braking function working fine, and wheel not dragging or binding, even when hot, wheel turns ok on centre stand.
Bite bullet, order new caliper from Triumph, 2nd hand master cylinder from the ebays, new seals for master cylinder from Nat Triumph.
M/Cyl cleaned and polished, red grease all round, and nice and smooth.
Wheel appears straight, and minimal run out on disc (some on wheel itself, but not excessive.)
Re assemble and fit new caliper. Existing SS hose has no visible damage.
Bleed system, set reservoir to lowest amount, as I read this can cause issue. Ensure all is free floating, and off we go.
Now disc still too hot to touch after ride. Definitely not coming from bearings etc.
Braking really well with new caliper, which came with Nissin pads, no binding, but still hot.
Only done about 50 miles so far, but should I be concerned?. Front discs are fine, and only get warm with heavy braking

Comments??

[Bixxer Bob]

To be honest, I've never felt the back disc for heat but it sounds like you've done everything you can.  Question - how is your foot brake lever adjusted??  Mine was a tad high and I would have to lift my toe slightly to get on it.  That led to me trailing the rear brake a lot and accelerated pad wear.

That's not to be confused with trailing the rear brake to calm the bouncy front which is normal tigger rider behaviour.  Nor is it to be confused with me bluing my rear disc and boiling the fluid while in France.  That was down to full lock U-turn hairpins and gravel.

[nickjtc]

To be honest, I've never felt the back disc for heat but it sounds like you've done everything you can.  Question - how is your foot brake lever adjusted??

+1. Go out for a ride and have someone follow you to see if the brake light is on. I've worked with many riders who are doing so whilst inadvertently caressing the rear brake pedal.

[Sin_Tiger]

Or run a temp wire to a wee light on the dash.

Any discoloration on the disc?

[JayDub]

  with Bob, I noticed the same after fitting sintered pads once, I also noticed a few days ago after fitting the new disc (with new EBC organic pads) that I burned my little pinky - after a run of about 45 mls. I don't think its anything to worry about as I've had steaming discs before on other bikes...
maybe the front don't get as hot as the force is distributed to two discs, if you get my drift... ie less force needed than with the single rear 
i dunno, maybe I'm talking  but It seems almost logical to me 

[London_Phil]

No discoloration of disc, and brake light not on.

Brake pedal set for maximum travel.

[Sin_Tiger]

If you rock the wheel back and forward, you should be able to detect just a slight bit of movement at the caliper torque arm.

[London_Phil]

Yep, play at torque arm, and the brake mounting bracket is free on the bush, so the assembly will rotate around the wheel when the torque arm is released.
As said before, even when hot, there is no binding of rear wheel I can detect by hand, and although disc is too hot to touch, brake function is normal.
maybe overthinking it.
Having a little run out to Bexley Triumph Owners rally this weekend, will see how it all beds in, (again)

[Sin_Tiger]

  the only other thing I can suggest is do a run where you can avoid using the rear brake completely and check again.

My outfit was owned by a Bexley member at sometime, got a sticker somewhere.

[GavD]

  Give the caliper a wiggle first to push the pads back in a bit.

[Geoff W]

I have a similar problem, I have been through two rear discs due to a dragging rear caliper, have only just replaced the front discs after 72k miles. I have stripped and cleaned caliper etc, although probably not as thoroughly as you have. Rear disc is still hot compared to front, but as pointed out there is only one disc to take the load. I tend to use my rear brake quite alot.
The disc does not get as hot as it did in the past so I think that this is now as good as it will get, I was thinking of rebuilding the everything, as you have, after reading your report, I think I will just live with it. Perhaps we can encourage others to feel their discs after a ride?
The rear brake is remarkably good compared to many other bikes, a couple of friends with Aprillas reckon the rear disc on these is just for decoration, other riders I travel with say they almost never use the rear brake, but as I say i use mine alot as it is so effective.

[London_Phil]

Thanks Guys.

Went to the Bexley Triumph Rally ( and won best Hinckley for my sins!!) . Sadly, I was so wet from riding back on Sunday, I never checked it.
Have to say that the Nissin OEM pads that came with the new caliper are very progressive, and braking was very good in the rain.
The bike shows no sign of brake drag when rolling, and at this point, I think Ill just keep using it, and see what happens over next few rides.
I'll post a pic of my trophy later!!

Regards
Phil

[JayDub]

Perhaps we can encourage others to feel their discs after a ride?

New TT.com rules...
After each ride:
1. Feel your discs.
2. Check your helmet
3. Scratch your knackers.

...Congrats Phil, well done. 

[Sin_Tiger]

Well done Phil. There's not many Steamer owners can say they have won any prizes with one 

The seals you used when you rebuilt it previously, we're they Nissin or an after market make?

I know someone who might be interested in your old caliper if you want to shift it and I think he might be listening 

[JayDub]