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 02-20-09, 11:53 PM   #1
twocoasttb
Senior Member
Thread Starter
 
twocoasttb's Avatar
 
Join Date: Feb 2006
Location: Redwood City, CA
Bikes: Seven Axiom SG
Posts: 286
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
A couple of questions

I took my bike into my LBS last week and they overhauled the rear hub. Before I took it in, the cranks would rotate if you spun the wheel forward. After the overhaul, the rotation is much less, but it's still there. Is that acceptable? I was under the impression that it shouldn't happen at all.

On a ride prior to taking the bike in I noticed some rubbing on the rear brakes when standing in a climb. The mechanic said it could be because of hub issues. After the overhaul, the rubbing is still there and is just as bad as before. The rear wheel looks true (it's a Mavic Kysirium SL, a couple of years old). My hunch is the wheel is flexing more than it should. Does that sound reasonable? I'm hoping it doesn't have anything to do with the frame (Seven Axiom SG). Any ideas on what to look for here?
__________________
lol is not a punctuation mark.
twocoasttb is offline   Reply With Quote
Old 02-21-09, 11:44 AM   #2
bikeman715
Senior Member
 
bikeman715's Avatar
 
Join Date: Mar 2008
Location: Salinas , Ca.
Bikes: Bike Nashbar AL-1 ,Raligh M50 , Schwinn Traveler , and others
Posts: 2,402
Mentioned: 1 Post(s)
Tagged: 0 Thread(s)
Quoted: 4 Post(s)
the problem with your rear wheel is with the freehub (the gears) and not with the hub itself. it can be cost by too much grease in it or there dirt in it and need to be flush out. you might want to go back to your lbs and have them look at it again.also have them check the axle it might have a hair line crack in it ( that may not be see by eye ),but when under load it open up cause your problems.
bikeman715 is offline   Reply With Quote
Old 02-21-09, 01:27 PM   #3
operator
cab horn
 
Join Date: Jun 2004
Location: Toronto
Bikes: 1987 Bianchi Campione
Posts: 28,306
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Quote:
Originally Posted by twocoasttb View Post
I took my bike into my LBS last week and they overhauled the rear hub. Before I took it in, the cranks would rotate if you spun the wheel forward. After the overhaul, the rotation is much less, but it's still there. Is that acceptable? I was under the impression that it shouldn't happen at all.
I think your terminology is screwed up. Overhauling a rear hub has no impact on the test which you describe - which is for freehubs. Nobody overhauls freehubs, they are tossed and replaced. A rear hub that was too tight and then adjusted properly as part of a hub o/h could cause the symptoms you describe.

Quote:
On a ride prior to taking the bike in I noticed some rubbing on the rear brakes when standing in a climb. The mechanic said it could be because of hub issues. After the overhaul, the rubbing is still there and is just as bad as before. The rear wheel looks true (it's a Mavic Kysirium SL, a couple of years old). My hunch is the wheel is flexing more than it should. Does that sound reasonable? I'm hoping it doesn't have anything to do with the frame (Seven Axiom SG). Any ideas on what to look for here?
Again, overhauling the rear hub should do diddly crap to this brake rub issue. Unless the cones were so loose that the wheel was rattling around then overhaul, again does nothing. I'm not exactly sure what "hub issues" would cause a wheel to flex at the rim. Sounds like total bull**** to me.

You may want to precisely check the trueness of your rim, spoke tension (too loose causes unwanted amount of flex) and the proper adjustment of your brake.
operator is offline   Reply With Quote
Old 02-22-09, 11:37 PM   #4
conspiratemus
Senior Member
 
Join Date: Jun 2008
Location: Hamilton, Ontario, Canada
Bikes:
Posts: 265
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Properly built wheels are too stiff to flex this way. Standing while climbing a hill, especially if you are big and strong, can cause the frame to flex enough to make the rear brake rub. I can't do that but I can flex a steel frame enough to cause ghost-shifting in old-fashioned downtube shifters that didn't have differential friction. Try opening the quick-release of the rear brake when you start a climb -- just remember to close it again when you start down the other side. Or adjust the pads farther from the rim, but be warned that with brakes that have a lot of mechanical advantage like dual pivots, the pads don't have to move out very far before the lever will run out of travel and bottom against the handlebar -- not good! These brakes do require that the rim be precisely true, so that the pads can be adjusted close, and any flex from the frame will cause wobbles to hit the brake pads all the more noticeably. Finally, dual pivot brakes don't "follow" an out-of-true wheel the way sidepulls do, so if the rim does brush the brake pad (whether from wobble or from frame flex) it will drag harder because the brake arm won't move out of the way.

Since the freehub is integrated with the rest of the hub and the axle runs through the whole she-bang, I think it is correct to expect that a "hub overhaul" would involve checking the action of the freehub ratchet, even if the fix was simply to toss it and replace. But replacing dried out crusty grease with slippery fresh stuff, or oil, would be worth a try, surely. It sounds like that's what the OP's shop tried, since it did improve the coasting some. My experience is that freehubs don't coast quite as smoothly as a good freewheel -- consequently forward movement of the wheel will cause the pedals to turn at least a little. This doesn't matter in a race because you're never coasting anyway.
conspiratemus is offline   Reply With Quote
Old 02-23-09, 12:17 AM   #5
twocoasttb
Senior Member
Thread Starter
 
twocoasttb's Avatar
 
Join Date: Feb 2006
Location: Redwood City, CA
Bikes: Seven Axiom SG
Posts: 286
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Thanks for the answers, everyone. Sorry about the incorrect terminology; I'm new to this.
__________________
lol is not a punctuation mark.
twocoasttb is offline   Reply With Quote
Old 02-23-09, 12:28 AM   #6
conspiratemus
Senior Member
 
Join Date: Jun 2008
Location: Hamilton, Ontario, Canada
Bikes:
Posts: 265
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Quote:
Originally Posted by twocoasttb View Post
Thanks for the answers, everyone. Sorry about the incorrect terminology; I'm new to this.
You're welcome, and nothing to apologize for. The freehub is as much a part of the hub as the axle and ball bearings are. Therefore a "hub overhaul" includes the freehub mechanism. (Unlike with a freewheel where the shop could do a complete hub overhaul even if you had taken the freewheel off and left it at home.)
conspiratemus 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 10:52 AM.