Cycling and bicycle discussion forums. 
   Click here to join our community Log in to access your Control Panel  


Go Back   > >

Bicycle Mechanics Broken bottom bracket? Tacoed wheel? If you're having problems with your bicycle, or just need help fixing a flat, drop in here for the latest on bicycle mechanics & bicycle maintenance.

User Tag List

Reply
 
Thread Tools Search this Thread
Old 06-08-08, 07:37 PM   #1
Wilbur Bud
Senior Member
Thread Starter
 
Join Date: Oct 2006
Location: Fishers Indiana
Bikes: Longbikes Slipstream
Posts: 367
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 4 Post(s)
Hub cartridge bearing, acceptable axial clearance

I was replacing a worn out rear hub bearing and noticed that the replacement bearings left a slight axial clearance with the hub when secured to the axle -- about 0.020-0.030 -- which meant the hub could potentially slide that amount side to side during cornering or other side loading. Not liking that, I made a shim to go underneath the bearing on one side, but not having anything to really tune in the thickness, the best I could do was about 0.005 or less gap, but this time between the bearing and the step on the axle. Anyone have any guidance or a reference about how much clearance or interference is acceptable in a fit like this? Made a couple pics to try and explain it better.



__________________
Longbikes Slipstream
Wilbur Bud is offline   Reply With Quote
Old 06-10-08, 10:30 AM   #2
DMF 
Elitist Troglodyte
 
DMF's Avatar
 
Join Date: Jun 2006
Location: Dallas
Bikes: 03 Raleigh Professional (steel)
Posts: 6,924
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
You're fine with the shim; 0.005 is pretty small and will disappear when the quick-release is tighened. BTW, how did you measure those clearances? Those are hard spots to get to.

Yes, I think your concern was well-founded. Are the replacement bearings narrower than the originals?
__________________
Stupidity got us into this mess - why can't it get us out?

- Will Rogers
DMF is offline   Reply With Quote
Old 06-10-08, 07:20 PM   #3
HillRider 
Senior Member
 
Join Date: Aug 2005
Location: Pittsburgh, PA
Bikes: '''96 Litespeed Catalyst, '05 Litespeed Firenze, '06 Litespeed Tuscany, '12 Surly Pacer, All are 3x8,9 or 10. It is hilly around here!
Posts: 29,126
Mentioned: 4 Post(s)
Tagged: 0 Thread(s)
Quoted: 182 Post(s)
Could the replacement bearing be seated deeper into the hub shell and the extra space taken by an external shim or can you thread the cone in further and add a washer under the locknut to keep the locknut spacing correct?
HillRider is offline   Reply With Quote
Old 06-10-08, 08:02 PM   #4
Wilbur Bud
Senior Member
Thread Starter
 
Join Date: Oct 2006
Location: Fishers Indiana
Bikes: Longbikes Slipstream
Posts: 367
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 4 Post(s)
Replacement bearings were identical to worn ones coming out. Who can say what was original?

Measurements were with an indicator on the 0.020-0.030 because I could locate and read externally. Measurements were stacked up to calculate the 0.003-0.005 internal gap.

Figures given are with bearings seated all the way, external shims won't help with the bearing gap and the dropout width is no problem. There is no cone on a cartridge bearing and while I could torque down the lock nuts to close that last 0.005 gap, I don't want to do it because its a ball bearing in a race and preload is normally only used/spec'd for cone/roller bearings.
__________________
Longbikes Slipstream
Wilbur Bud is offline   Reply With Quote
Old 06-10-08, 09:49 PM   #5
Torque1st
Space Dust
 
Join Date: Jan 2008
Location: KC Metro
Bikes: Old DF
Posts: 261
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Nice pictures!

You need some clearance for differential thermal expansion rates in the materials otherwise expansion can take up all of the slack and put enormous axial loads on the bearings causing them to heat up more and fail.

It looks like your current setup will quickly load the bearings and cause failure.
Torque1st is offline   Reply With Quote
Old 06-11-08, 02:14 AM   #6
dabac
Senior Member
 
Join Date: Mar 2008
Bikes:
Posts: 5,700
Mentioned: 5 Post(s)
Tagged: 0 Thread(s)
Quoted: 101 Post(s)
Quote:
Originally Posted by Wilbur Bud View Post
I was replacing a worn out rear hub bearing and noticed that the replacement bearings left a slight axial clearance with the hub when secured to the axle ... Anyone have any guidance or a reference about how much clearance or interference is acceptable in a fit like this? Made a couple pics to try and explain it better.

I'd be really wary about this setup. The type of cartridge bearings used in bike hubs really do very poorly when faced with an axial load.

From:http://www.skf.com/portal/skf/home/p...newlink=1_1_13

Axial load carrying capacity

If deep groove ball bearings are subjected to .. axial load, this axial load should generally not exceed the value of 0,5 C0. Small bearings (bore diameter up to approx. 12 mm) .. should not be subjected to an axial load greater than 0,25 C0. Excessive axial loads can lead to a considerable reduction in bearing service life.



Which, if I've read the charts correctly would mean that an axial load of about 500 N would be bad news for a probable bike bearing. How hard do you think your QR closes?
dabac is offline   Reply With Quote
Old 06-11-08, 10:11 AM   #7
DMF 
Elitist Troglodyte
 
DMF's Avatar
 
Join Date: Jun 2006
Location: Dallas
Bikes: 03 Raleigh Professional (steel)
Posts: 6,924
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
dabac has it right, in principle.

But this raises a corollary question. If the distance between the axle flanges (where the inner bearing race would seat) is greater than the distance between the hub inner faces (where the outer bearing race would seat), then there's no way to properly locate the outer races. Drive the shell too deep or leave it too shallow, you've introduced axial load too. (Assuming the shells are press-fit.)

The reason I preferred the shim is that a dislocation of .005 is better than a dislocation of 0.030.

How tight are the shells in the hub?

If the shells can float I think I'd leave the shims out.
__________________
Stupidity got us into this mess - why can't it get us out?

- Will Rogers

Last edited by DMF; 06-11-08 at 10:21 AM.
DMF is offline   Reply With Quote
Old 06-11-08, 10:14 AM   #8
HillRider 
Senior Member
 
Join Date: Aug 2005
Location: Pittsburgh, PA
Bikes: '''96 Litespeed Catalyst, '05 Litespeed Firenze, '06 Litespeed Tuscany, '12 Surly Pacer, All are 3x8,9 or 10. It is hilly around here!
Posts: 29,126
Mentioned: 4 Post(s)
Tagged: 0 Thread(s)
Quoted: 182 Post(s)
Quote:
Originally Posted by Wilbur Bud View Post
There is no cone on a cartridge bearing and while I could torque down the lock nuts to close that last 0.005 gap, I don't want to do it because its a ball bearing in a race and preload is normally only used/spec'd for cone/roller bearings.
I understand that cartridge bearings don't use "cones" the way loose ball hubs do but they normally have a sleeve nut that fits pretty much the same way and acts as a bearing retainer and side-clearance adjuster. I used cone in a generic sense.
HillRider is offline   Reply With Quote
Old 06-11-08, 05:13 PM   #9
Booger1
Senior Member
 
Join Date: Sep 2007
Location: Gaseous Cloud around Uranus
Bikes:
Posts: 3,730
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 22 Post(s)
Sounds like there is an offset difference between the inner and outer races,between new and old bearings.Put a straight edge across the races on new and old bearing and check for an offset on one bearing or the other.If both bearings(new/used are flat across the races,check the radius on the races to see if the radius is keeping the the bearing from seating flat against the hub or the axle flange.
Booger1 is offline   Reply With Quote
Old 06-12-08, 03:49 AM   #10
dabac
Senior Member
 
Join Date: Mar 2008
Bikes:
Posts: 5,700
Mentioned: 5 Post(s)
Tagged: 0 Thread(s)
Quoted: 101 Post(s)
Quote:
Originally Posted by DMF View Post
If the distance between the axle flanges (where the inner bearing race would seat) is greater than the distance between the hub inner faces (where the outer bearing race would seat), then there's no way to properly locate the outer races. Drive the shell too deep or leave it too shallow, you've introduced axial load too. (Assuming the shells are press-fit.)
If the press fit between outer race and hub is tight enough to prevent the hub from sliding back & forth there's no need for the outer race to bottom out against the bottom of the hub bearing seat.
Actually, since the bearing sucks at dealing with axial load there's not much point in having the hub being able to transfer something that the bearing can't handle.

The inner race needs to be supported by the axle to withstand the compression added by the QR, but since the whole design is based around the theory of no axial loads on a bike wheel the axial support of the outer race becomes pretty much a non-issue.

Personally I've had my doubts about this theory for quite awhile, bearings in cartridge hubs seems to last significantly shorter than the old-style cup&cone bearings.
dabac is offline   Reply With Quote
Reply


Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off



All times are GMT -6. The time now is 07:20 AM.