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 02-25-09, 06:53 AM   #1
marcelinyc
R900Campagnolo
Thread Starter
 
marcelinyc's Avatar
 
Join Date: Jun 2005
Location: Brooklyn
Bikes: track and road
Posts: 884
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Verticaly untrue wheel

Is it ok to race it? Laterally it is perfect.
marcelinyc is offline   Reply With Quote
Old 02-25-09, 07:19 AM   #2
xenologer
Senior Member
 
Join Date: Aug 2008
Bikes:
Posts: 2,089
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 13 Post(s)
No, you'll lose energy from the tiny up and down motion it causes and Lose The Race.
xenologer is offline   Reply With Quote
Old 02-25-09, 07:35 AM   #3
trekkie820
Senior Member
 
Join Date: Feb 2004
Location: Cleveland, OH
Bikes: 2004 Trek 4600, 1980's Univega Supra Sport, 2006 Lemond Reno
Posts: 2,287
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Why not try to true it? What you have is called a "hop". At the top of the "hop" the spokes are under less tension (assuming the rim is not bent), so tighten the two, four or six spokes that encompass the hop. Be careful, if you are not sure of yourself, do not attempt this. Only do 1/8 to 1/4 turn at a time, and when you're done, check the lateral trueness.

In order to do this, you need to tighten two, four or six spokes. If you only tighten one, three or five spokes, you'll throw off the trueness.
trekkie820 is offline   Reply With Quote
Old 02-25-09, 08:39 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)
Careful: the OP didn't say whether the vertical error is up (a hop) or down (a dip, i.e. a flat spot.)

In a hop, the rim is not usually bent and can indeed often be corrected by tightening spokes in the area of the hop. If the spokes are noticeably looser at the hop than they should be, tightening just those spokes will usually do it, but it takes one-half to a full turn to see much effect in vertical movement. But if the spokes at the hop are roughly the same tension as the other spokes, then you really need to loosen spokes elsewhere around the rim to bring the wheel as a whole into roundness. This can be a challenge and is definitely not something to tackle as your introduction to wheel-building. Merely making the spokes at the hop extra tight will not work in the long run and will cause the rim to fail prematurely. A rim that started out round but is now egg-shaped has often started to fail anyway by cracking around the spoke holes.

An isolated dip/flat spot is another story. In this case the rim is nearly always bent (from hitting a pothole, say) and the sidewalls are often flared out so they interfere with the brake pads. The spokes in the area of the flat spot will be loose because the rim has been pushed permanently closer to the hub. A flat spot cannot be worked out by tightening spokes. The rim will need to be replaced. References on wheel-building and repair discuss a variety of expedients to get a badly dented rim straight enough to ride in an emergency.
conspiratemus is offline   Reply With Quote
Old 02-25-09, 09:06 PM   #5
well biked 
biked well
 
well biked's Avatar
 
Join Date: Jul 2005
Bikes:
Posts: 7,123
Mentioned: 1 Post(s)
Tagged: 0 Thread(s)
Quoted: 38 Post(s)
I like what Peter White has to say on this subject, he puts a real world perspective on it. He mentions that even with quality rims, up to 1mm vertical deflection can sometimes be expected, and that in real world riding, you'd never feel that. Anything more than that, with a quality rim such as Mavic or Velocity, is unacceptable to him. Scroll down to the heading "how true will your wheel be?"

http://www.peterwhitecycles.com/wheels.asp

Last edited by well biked; 02-25-09 at 09:18 PM.
well biked is offline   Reply With Quote
Old 02-25-09, 10:02 PM   #6
Panthers007
Great State of Varmint
 
Panthers007's Avatar
 
Join Date: Sep 2008
Location: Dante's Third Ring
Bikes:
Posts: 7,479
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
His wheels are magnificent. Utterly true vertically & laterally. Everyone who gets a wheel/sees a wheel From him raves.
Panthers007 is offline   Reply With Quote
Old 02-26-09, 09:31 AM   #7
marcelinyc
R900Campagnolo
Thread Starter
 
marcelinyc's Avatar
 
Join Date: Jun 2005
Location: Brooklyn
Bikes: track and road
Posts: 884
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
thanks for replies.
the question is not how to fix it but is it ok/safe to race it?
marcelinyc is offline   Reply With Quote
Old 02-26-09, 09:40 AM   #8
Squeazel
Luddite
 
Join Date: Jan 2007
Location: Portland, OR
Bikes: Univega Gran Turismo, Cannondale Synapse, Bianchi Aquiletta Folder
Posts: 276
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
If it's really bad, like > 5 mm, then you should fix it. If it's < 2mm then test that the spokes are nearly the same tension by plucking them, and race it if they are- the tire has more vertical bounce than that. Between those extremes, I would spend some quality time with my spoke wrench, but YMMV.
Squeazel is offline   Reply With Quote
Old 02-26-09, 09:48 AM   #9
cbchess
Map maker
 
cbchess's Avatar
 
Join Date: Feb 2008
Location: Richmond,VA
Bikes: Ventana El Ciclon, Walt Works 29er, Specialized Enduro (fixed up for my son).
Posts: 728
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
I've had a few minor hops in my wheels when hand building them that usually fall right at the weld or seam - it appears there is slightly more material on the rim in this area. I get it as close as I can them leave it alone. They have been Good for years.
cbchess is offline   Reply With Quote
Old 02-26-09, 05:05 PM   #10
AnthonyG
Senior Member
 
AnthonyG's Avatar
 
Join Date: May 2005
Location: Queanbeyan, Australia.
Bikes:
Posts: 3,711
Mentioned: 5 Post(s)
Tagged: 0 Thread(s)
Quoted: 231 Post(s)
Quote:
Originally Posted by marcelinyc View Post
thanks for replies.
the question is not how to fix it but is it ok/safe to race it?
Take it for a ride and see how it goes. If you cant feel anything then its OK. If you can feel it then maybe its not. My experience with a hop on a cheap wheel is that when just riding around it was OK, not dangerous but it did cause the wheel to wobble from side to side and it was a little unstable, particularly when riding with no hands despite it being true from side to side.

Anthony
AnthonyG is offline   Reply With Quote
Old 02-26-09, 07:10 PM   #11
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)
You people do realize that wheel trueness isn't what defines a quality build. It's trueness and as even tension as possible... right?

Any moron can make a wheel hyper true at the expense of tension.
operator is offline   Reply With Quote
Old 02-26-09, 08:37 PM   #12
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)
Yes, this moron recognizes that even spoke tension is more important than "hyper trueness" (whatever that is.)

To the OP:
1) If the hop or (particularly) flat spot causes the rim to catch on the brakes as I mentioned above, then I would not ride it in a peloton because your braking modulation will be jerky, especially with dual-pivot brakes that don't "follow" the wheel imperfections as well as side-pulls do.
2) If there is enough of a hop that you can feel it bouncing under you, that can't make your control any better when you are pushing yourself to your limits in cornering.
3) If the hop doesn't do either of these things but is due to uneven spoke tension, then the wheel will go progressively out of round or out of true and eventually become unrideable, but until it does, .... go for it. Other riders will nag you about it though.
conspiratemus is offline   Reply With Quote
Old 02-27-09, 02:44 PM   #13
martinrjensen
Senior Member
 
Join Date: Nov 2008
Location: Seattle
Bikes: Trek Madone, Trek TX900, Serotta CSI, Performance Scattante Elite
Posts: 129
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Quote:
Originally Posted by operator View Post
You people do realize that wheel trueness isn't what defines a quality build. It's trueness and as even tension as possible... right?

Any moron can make a wheel hyper true at the expense of tension.
So your condescending statements are back again. Now you are calling us all morons? There are a lot better ways to converse without being so rude. I'm starting to see a pattern here.
martinrjensen 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 10:02 AM.