Tapered Bearings - Brake Judder

Paul Sutton

I Collect Fingers
Top Contributor
Messages
2,717
Reaction score
7,161
Points
513
Location
Cardiff UK
I have just recently fitted tapered steering bearings and did remember to file in the grooves for future removal. I road tested the bike yesterday and all seemed fine. However, today the front brake has started to judder. Is this simply an issue of tightening the bearings a little further?

Also, today is blue sky with 13 Degrees Celsius!!

Did some further road testing. The bike pulls nicely up to 40 - 50 mph where it goes a bit flat and them pulls really well from 50 to 70 mph (Dial speed) and probably beyond. Is this what is expected from an 81 Special with BS34, a flat region in the 40 - 50 mph range?

Also tested out my newly added voltmeter:

1200 rpm - 12.6 V
1500 rpm - 13.8 V
1800 rpm and above - 14.2 V (Regulator stated control is 14.2 V)

I am pleased with this visual indicator for the electric system.

Thank you for any comments.
 
Yes, maybe a tightening of the bearings is needed. Although you try to pound the new races all the way in, it doesn't always happen. Riding the bike finishes the job for you and the bearings become loose.

No, I don't think a midrange flat spot is normal, but it's difficult to comment further without knowing what your mods are and what jetting changes you've made. I've ridden both BS38 and BS34 equipped 650s and both pull evenly from idle to redline if the carbs are set up right. Flat spots or stumbles in certain parts of the RPM range means they're not.
 
Thanks for that 5twins. Will revisit the carbs and bearings this week. I also have a new fuse box to fit this week as well so should be ready for fun when the weather settles by end of April.
 
Paul I had the same thing happen with my tapered bearings. It took a couple of weeks for mine to be noticed, and a little adjustment cured it.

Oh yes, a voltmeter is a must have on these older bikes. I added a voltmeter to my car as well. It keeps you informed, and will give warning if maintenance is needed, such as brushes starting to get too short. 14.2 volts you see is perfect!

13 C and a blue sky.......................that is super for March!
 
- - - Although you try to pound the new races all the way in, it doesn't always happen. Riding the bike finishes the job for you and the bearings become loose - - -

Hi 5twins,
saying "pound - - - all the way in" as a description of ball or roller race installation may encourage a beginner
to reckon that whacking races home with a BFH was a proper thing to do.
Beginners should understand that while rotating element bearings are as sturdy as hell after they are installed,
they are kinda frail until they are fully in place.
Squeezed in with a hydraulic press and custom spacers is best.
Squeezed in with a threaded rod, nuts and big washers is acceptable.
Smacking them down with a block of wood and a BFH is a bad thing.
 
Thank you for all the comments 5T, RG and Fred. It just took me one look at the tapered bearings to know care must be taken. That bottom outer race almost comes to a knife edge. I bet a few have knocked chips out of them. Just checked my plugs after making a carburetor adjustment before the run today and they are looking very good.

Good Night - Daylight Saving just started, must get up an hour earlier for work tomorrow - Damn!!!
 
Update - Today I re-confirmed the juddering and then tightened the bearings. On re-test the judder have gone. I expect I will need to make a final adjustment in a week or two. I found that the best way to make the adjustment was to jack the front up and drop off the wheel and forks. That way you can feel how tight the bearings are. I had first tried doing this with everything together but just could not get any feeling for the bearings - too much weight on the bearings I guess.
 
Update - Today I re-confirmed the juddering and then tightened the bearings. On re-test the judder have gone. I expect I will need to make a final adjustment in a week or two. I found that the best way to make the adjustment was to jack the front up and drop off the wheel and forks. That way you can feel how tight the bearings are. I had first tried doing this with everything together but just could not get any feeling for the bearings - too much weight on the bearings I guess.

Hi Paul,
back in the day we set the adjusted the headrace by jacking the front wheel off the ground and tightening the race until there was zero shake when you pushed and pulled on the fork legs but the forks fell to either side from straight ahead when you gave the bars a nudge.
This was for adjusting crowded ball races. Me, I'd give tapered rollers another 1/4-turn past that. Mind you, that setting is too loose for sidecar work.
I've had to give tapered roller head races a whole extra turn to fix a sidecar rig's steering judder.
 
Good Night - Daylight Saving just started, must get up an hour earlier for work tomorrow - Damn!!!

To quote a Cree Elder's comment about his doctor's explanation that the Elder was an hour late for his appointment because of Daylight Saving:-
"Dunno who reckoned that cutting a foot off one end of a blanket and sewing it onto its other end got you a longer blanket but it must have been a white man"
Note that Saskatchewan has proudly NOT been switching to Daylight Saving ever since it was first dreamed up.
 
Thanks for that Fred, I must remember that story about the blanket. I am about 1/8 tighter at present but did not want to over do it. I am sure that in a few days I will need adjust a further 1/8.
 
I set my bearings with everything assembled. I block the front wheel off the ground and nudge the bars left and right from center. I want the wheel to fall over slowly, not quickly and slam into the stops. I know cables and wires get in the way, but I can usually judge by the limited amount of free fall I do get. Also of note - when you tighten down that big top nut, it can often make the bearings a bit tighter. You may have to compensate for that by setting them a hair looser.
 
Update - No further adjustment has been necessary and the brakes no longer judder. Thank you for all advice given, it will remain with me and help me solve further problems I or others encounter.
 
Harley has been using Tapered roller bearings in the steering head for years. They adjust with a "Fall Away" method.
Lift front wheel just off the ground. Attach a string with a weight on it to the back of the front fender. Have the weight just off the ground. With wheel straight mark a line just under the weight. Now mark a line 1 inch to each side of the first line. Now gently nudge one side of the bars. If it "falls away" just as the weight passes the outer lines then the bearings are right. If it "falls away" before the line, tighten the bearing. If it "falls away after the line, loosen the bearings. If the clutch cable or wiring won't let the bars stay straight, unhook them.
This is how I adjusted them when I installed them on my 75, it can take a bit of trial and error but it works well.
Leo
 
I found this when reading the factory repair manual for my Harley. It was a costly book but well worth it. About $70 as I recall. I should get the electrical book too. It's starting to have issues. Sometimes when I turn on the key the digital readouts for the odometer don't come on. The Neutral light often does the same.
Everything else is ok.
Leo
 
Back
Top