Rear end singing

[lemppari]

After changing the rear wheel bearings, I thought i've gotten rid of the rear end singing at 85-95 km/h, but no! After having ridden some 100 km:s, it's there, loud and clear. Easiest to hear when reaching furthest back on the saddle, in normal stance it's hardly audible.

 

Wether I'm accelerating or on overrun has no effect on the sound, neither if I pull the clutch and drop to idle. It's only the speed that provokes the sound. The pitch seems to be constant, only the volume increases.

 

It started right about the same time when I changed the rear end oil, so could it be that the Motorex 85/95 stuff turns thin when sufficiently heated? And yes, I have added the Moly. Come to think of it, I also put Motorex gear oil in and when the gearbox is hot, the gearchange is tacky. Or could I be suffering from excessive tyre noise?

 

Any learned guesses or even knowledge, anyone? Or how can I pinpoint what generates the sound. In a dyno, perhaps?

[grossohc]

Could it be the needle roller bearing on the rear drive, did you check it when the wheel was out

[lemppari]

Could it be the needle roller bearing on the rear drive, did you check it when the wheel was out

My thoughts also, either that or the big bearing inside, though that one is in constant oilbath and shouldn't let go easily. Or if the ignorant tyre guy tightened the rear axle nut to umphteen kilo's, could it pack the big bearing too tight also?

[gstallons]

Tightening the rear axle nut will just tighten things so much. This should not affect lateral load on the bearings.

[fotoguzzi]

Tightening the rear axle nut will just tighten things so much. This should not affect lateral load on the bearings.

could it be worn tire? I had Metzlers (two) that would howl w/4-5k miles, turned out you could see the cupping in the tread causing it.. I don't buy them anymore.

[savagehenry]

Have you tried putting it up on a stand and running it to see if you can identify the source? Maybe it won't even do it that way? If it does make that noise and you can't pinpoint it, try a stethoscope or the old fashioned way, a wooden stick with one end layed flat across your ear/cheek and touching bike parts with the tip of the other end. I was amazed at how you can hear/feel all those different noises and their sources when my M.I.T. schooled engineer father showed me how they did it on the farm as a kid. Good luck in your quest for an answer, S.H.

[Baldini]

Tightening the rear axle nut will just tighten things so much. This should not affect lateral load on the bearings.

Yes - if all parts are in spec. But if spacer was short & brng outer races are home in the hub, torquing the axle would put a lateral load on inner races causing misalignment = knackered brng in short order.

[gstallons]

Tightening the rear axle nut will just tighten things so much. This should not affect lateral load on the bearings.

Yes - if all parts are in spec. But if spacer was short & brng outer races are home in the hub, torquing the axle would put a lateral load on inner races causing misalignment = knackered brng in short order.

 

 

It would have the same affect at 120lbs. as 60lbs. of torque though.

[Baldini]

It would have the same affect at 120lbs. as 60lbs. of torque though.

Only if distances thru components remain in spec whilst torque increases. I believe that some bearing spacers are poor quality & will compress when axle nut is tightened past the point that they are able to withstand compression. More torque on axle nut = more compression. It is distortion of the bearing spacer that causes misalignment within the bearing(s) & the more torque that is applied, the more the distortion.

 

KB

 

KB

[lemppari]

OK, I'm starting from the most obvious and change back to mineral oil for the end transmission, while the singing started AFTER I put in a fully synth hypoid oil. Then a lengthy test ride with a keen ear!

[lemppari]

OK, I'm starting from the most obvious and change back to mineral oil for the end transmission, while the singing started AFTER I put in a fully synth hypoid oil. Then a lengthy test ride with a keen ear!

Just come home after a lengthy testride. One still hears the sound, but no louder than the gearbox. Probably down to Guzzichondria that I'm so sensitive to that particular pitch, anyway.

 

Changing back to a proper mineral oil really made a difference. Maybe next time I'll put in some 90/145. That's seriously thick goo!

[lemppari]

Doing an after season oil change, the engine warm-up was done by hoisting the back end up and running through gears up to 90-100 kph. The rear end remained silent, apart from normal gear noise. The drive shaft joints ditto. Couldn't entice a whail even under load with the rear brake.

 

I can't think of anything else than tire noise as the cause, but never before have I heard such a yodle from a motorcycle tire. A big truck, yes, but then there's a difference in load also. THAT Michelin Pilot Power will definitely be the last of it's kind under my bike! On the positive side, there are no extra costs involved, one has to change tires from time to time anyway.

[grossohc]

Welll at least it puts your mind at rest that the bike is ok, next tyre change try dunlop roadsmarts

[lemppari]

Welll at least it puts your mind at rest that the bike is ok, next tyre change try dunlop roadsmarts

That has allready been rolling in the front. It bettered the behaviour of the front no end otherwise but still wears conical, as has been the case with every front tyre so far. There's several mm of pattern left, but the tyre feels like a cogwheel!

[Jim in NZ]

THAT Michelin Pilot Power will definitely be the last of it's kind under my bike!

 

Hi Lemppari,

I have always used Metzlers, but last time thought I would try Michelin Pilot Roads. There was a huge increase in tyre noise similar to what you are describing. On the rough chip New Zealand roads I find it annoying, and will change back to Metzler next time.

Cheers,

Jim.