How hot should the rear drive axel get?

[Makuna]

Got new ties put on (thanks NW Tech meet), and 90 degree valve stems. I got them home and after I assembled it and took it out for a ride. I left the saddle bags off as I wanted to check the install after a short tide.

Well the short ride turned into 40min (wow, new tires, love em). when I got back I reached down to see how much easier it was to reach the valve and notice the rim was warm. So I check and the rear disk break was hot; and so was the pumpkin (rear drive axel). Hot enough I could only leave my finger on for about 4 seconds before I was afraid of burning myself. The front disc was not even warm so it wasn't due to spiritied riding.

I didn't smell anything burning.

Should it be getting this hot?

I am pretty sure I assembled the rear axel correctly; any thoughts?

 

[escapefjrtist]

Good seeing you again today Makuna.

Something doesn't sound right. The pumpkin does get hot, but with temps we had today I wouldn't expect it THAT hot today. Disc shouldn't be that hot either unless you were really hard on the brakes.

I'd suggest to double check the installation and make sure all the spacers, etc. are in the right places.

--G

 

[Auburn]

What escapfjrtist said. if they are, then check this.

With the bike on the center stand, spin the rear wheel, is there a little drag or a lot. just checking if your rear brake is dragging too much. The pumpkin should get pretty warm to the touch and you probably can't keep your fingers on it. But the rear brake bing hot has me thinking the your rear brake is dragging. Which probably mean that your rear brake pedal is not fully releasing. Could be that you need to take the pedal off, clean and lube the pivot point.

 

[SLK50]

I am pretty sure I assembled the rear axel correctly.....

My first thought is: no, you didn't.

I'm willing to bet you installed the washer on the right side in the wrong location

thus causing the brake caliper to hold the brake pads against the rotor.

It would not take a lot of pressure to generate considerable heat.

Check your work ( again ) against the service manual and verify installation sequence.

There should also be a visible gap between the washer and swingarm.

 

[HotRodZilla]

You can double check your installation, but if that looks to be correct, go with what Auburn said. Hell, even if it snot dragging, it may be time to take the pivot apart and lube it anyway.

 

[garyahouse]

Good luck with your dilemma.

Gary

darksider #44

 

[Denver_FJR]

After a long ride in mid-60° temps, pointed an IR thermometer at rear drive, was showing about 130°. This was about 5 minutes after parking it and probably 15 minutes after coming off highway. Could I hold my hand against 130° drive for 4 seconds? Dunno. :huh:

 

[RossKean]

After a long ride in mid-60° temps, pointed an IR thermometer at rear drive, was showing about 130°. This was about 5 minutes after parking it and probably 15 minutes after coming off highway. Could I hold my hand against 130° drive for 4 seconds? Dunno. :huh:

For most people, the threshold for being able to hold your fingers against a smooth (i.e. metal or glass) object is pretty close to 140 °F. Much more than that, you might be able to maintain contact for several seconds but you will feel a need to pull your hand away before long. On a surface with low thermal conductivity such as a tire or fabric, maybe a little hotter (or maintain contact longer).

 

[frito1]

Hypoid gear sets create a lot of heat, just the nature of the beast. Load & speed could be variables affecting temps, but the heat is still gonna be there. There's a reason 90-130 wt. oils are used. If it ain't smokin' you're more than likely OK.

 

[scubabiker]

Pulled in the garage the other night and noticed my "back-off" brake flasher flashing. Pedal was binding slightly, took it apart and cleaned it with some carb cleaner and a light coating of water proof grease. Fine now. Was a little surprised it doesn't pivot on bearings like my dirt bikes, but if someone built a bike with everything I wanted on it, I wouldn't be able to afford it. The good manual and keen observation will cure most problems.

 

[Makuna]

...

the rear brake bing hot has me thinking the your rear brake is dragging. Which probably mean that your rear brake pedal is not fully releasing. Could be that you need to take the pedal off, clean and lube the pivot point.

We have a Winner, well sort of.

I was sure I installed that washer correctly between the swing arm and the brake caliper. I even gave the tire a spin before I rode and didn't hear anything but the driveline.

So put it back up in the air and gave it spin and yes, defintely now I hear drag I didn't hear before. I disasseblmed and checked for any rubbing marks and didn't see any; put it back together and spun it, yup, problem gone. Then I remember last night that I had to pump the brake before it would engage, I reach over and press the foot pedal a couple times until it stiffens up and the problem returns. So, yeah, the rear brake not fully returning is the problem.

It looks like the pedal is returning fine but the pads are definitely in contact. Could looks be decieving or is it more than likely just caked brake dust restricting the calipers?

Wouldn't you know, the only thing I didn't find in my "volitiles" cabinet is spray brake cleaner. I will pick up more diagnostics over this next week and give this thread a answer.

 

[Auburn]

...

the rear brake bing hot has me thinking the your rear brake is dragging. Which probably mean that your rear brake pedal is not fully releasing. Could be that you need to take the pedal off, clean and lube the pivot point.

We have a Winner, well sort of.

I was sure I installed that washer correctly between the swing arm and the brake caliper. I even gave the tire a spin before I rode and didn't hear anything but the driveline.

So put it back up in the air and gave it spin and yes, defintely now I hear drag I didn't hear before. I disasseblmed and checked for any rubbing marks and didn't see any; put it back together and spun it, yup, problem gone. Then I remember last night that I had to pump the brake before it would engage, I reach over and press the foot pedal a couple times until it stiffens up and the problem returns. So, yeah, the rear brake not fully returning is the problem.

It looks like the pedal is returning fine but the pads are definitely in contact. Could looks be decieving or is it more than likely just caked brake dust restricting the calipers?

Wouldn't you know, the only thing I didn't find in my "volitiles" cabinet is spray brake cleaner. I will pick up more diagnostics over this next week and give this thread a answer.

The pads should always make contact with the disc. There just won't be the drag you describe having. It could be dust and grim build up you describe, or it could be the pivot point on the brake pedal. I think it will be the latter, espcially if you have done any riding during the winter when they put deicer down. That stuff will cake in pivot points when it dries out and cause some corrosion which will bind up the pivot point.

 

[ahchiu]

You might also want to clean you caliper pistons so they move freely.

 

[Makuna]

You might also want to clean you caliper pistons so they move freely.

I spray cleaned the brakes. I also cleaned and lubed the brake pedal pivot. The scrapping noise still exists. Not sure it isn't just the pads resting against the discs and what that should sound like normally (anyone want to put their FJR on the center stand and put it in nuetral and spin their rear tire by hand?).

I was amazed at the corosion on the brake pedal. I don't remember driving through salt!

 

[Makuna]

I think the problem was the brake pads were getting "stuck" and not moving away from the disc. Previously I just spray cleaned them. I removed the calipers and did a close in cleaning, added a little lube to the clips the pads move along (there was none) but this allowed the pads now to move more freely. They still get hot though. I notieced the tabs on the pads that move along the clips was once coated in some sort of black paint. This paint was pealing revearling the copper metal. Strange they painted this surfaces.

Took it for ride (about 71F for 30 minutes) and checked the temperatures.

Rear Disc = 110F

Rear Pumpkin = 130F

Rear Tire = 104F (yeah, the tread)

I don't know whats normal, but it seems others have seen the pumpkin temprs I mentioned.