Go Back  Bike Forums > Bike Forums > General Cycling Discussion
Reload this Page >

What would happen if you true a bent rim

Notices
General Cycling Discussion Have a cycling related question or comment that doesn't fit in one of the other specialty forums? Drop on in and post in here! When possible, please select the forum above that most fits your post!

What would happen if you true a bent rim

Old 05-01-18, 10:12 AM
  #1  
JohnFyf
Junior Member
Thread Starter
 
Join Date: Jan 2018
Posts: 20
Mentioned: 1 Post(s)
Tagged: 0 Thread(s)
Quoted: 15 Post(s)
Likes: 0
Liked 0 Times in 0 Posts
What would happen if you true a bent rim

Such as the rim gets warped, but to a point where you can sort of bend it back into shape. Then true the wheel, but the problem is the wheel will never be properly dished because of the warp so there is an imbalance. If you were to put this back on your bike and ride it as is would it be fine or could this end in disaster? How about if this were just a temporary fix until the replacement rim comes, and can the spokes be reused?
JohnFyf is offline  
Old 05-01-18, 01:03 PM
  #2  
fietsbob
Banned
 
Join Date: Jun 2010
Location: NW,Oregon Coast
Posts: 43,598

Bikes: 8

Mentioned: 197 Post(s)
Tagged: 0 Thread(s)
Quoted: 7607 Post(s)
Liked 1,278 Times in 798 Posts
if physically bent the spoke tension balance will be off because tensile force must be applied to make it appear to run true again..

so a looser spoke allows the tighter opposing spoke to pull the bend back ,
but the rim being deformed not flat, on its own, this is an unstable situation.
fietsbob is offline  
Old 05-01-18, 01:31 PM
  #3  
Oneder
Banned.
 
Join Date: Apr 2018
Posts: 822

Bikes: Wahoo of Theseus, others

Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 428 Post(s)
Liked 64 Times in 45 Posts
If you true the wheel it's not bent any more, that's the definition of truing. If you can't true it then it's too bent and time to get new wheel.
Oneder is offline  
Old 05-01-18, 01:42 PM
  #4  
ThermionicScott 
7-speed cultist
 
ThermionicScott's Avatar
 
Join Date: Aug 2011
Location: CID
Posts: 20,045

Bikes: 1991 Bianchi Eros, 1964 Armstrong, 1988 Diamondback Ascent, 1988 Bianchi Premio, 1987 Bianchi Sport SX, 1980s Raleigh mixte (hers)

Mentioned: 87 Post(s)
Tagged: 0 Thread(s)
Quoted: 2779 Post(s)
Liked 701 Times in 493 Posts
Originally Posted by JohnFyf View Post
Such as the rim gets warped, but to a point where you can sort of bend it back into shape. Then true the wheel, but the problem is the wheel will never be properly dished because of the warp so there is an imbalance. If you were to put this back on your bike and ride it as is would it be fine or could this end in disaster? How about if this were just a temporary fix until the replacement rim comes, and can the spokes be reused?
Depends on how adventurous you are, or whether you're fixing the wheel for someone else. I wouldn't have any qualms "rescuing" a tacoed rear wheel and seeing how much longer it lasts in service until some other issue befalls it.
__________________
Originally Posted by chandltp View Post
There's no such thing as too far.. just lack of time
Originally Posted by noglider
People in this forum are not typical.
RUSA #7498
ThermionicScott is offline  
Old 05-01-18, 01:43 PM
  #5  
andr0id
Senior Member
 
andr0id's Avatar
 
Join Date: Feb 2009
Posts: 2,522
Mentioned: 11 Post(s)
Tagged: 0 Thread(s)
Quoted: 1421 Post(s)
Likes: 0
Liked 0 Times in 0 Posts
Originally Posted by Oneder View Post
If you true the wheel it's not bent any more, that's the definition of truing. If you can't true it then it's too bent and time to get new wheel.
No.

There is a difference between a damaged and bent rim and a rim that just has normal manufacturing irregularities.

A normal rim will true up with only very minor variance in spoke tension and stay true if built correctly.
A rim that is bent will take excessive tension on some spokes and reduced tension on other spokes to be made true (if it is even possible.)
The the unequal tension accelerates the wheel going out of true again and is more likely to cause the over-tightened spokes to fail.
andr0id is offline  
Old 05-01-18, 01:44 PM
  #6  
alcjphil
Senior Member
 
alcjphil's Avatar
 
Join Date: Jun 2002
Location: Montreal, Quebec
Posts: 3,940
Mentioned: 14 Post(s)
Tagged: 0 Thread(s)
Quoted: 973 Post(s)
Liked 319 Times in 211 Posts
If you manage to true a badly bent wheel hoping to ride it until you receive a replacement rim there is a very good chance that you will fatigue some of your spokes to a point where they should not be reused. If you are at a point where you have to replace both spokes and rim your best option may be a new wheel unless your hub is a very expensive high end boutique component. I don't know the specifics here, so I hesitate to make a specific recommendation
alcjphil is online now  
Old 05-01-18, 01:51 PM
  #7  
SkyDog75
Senior Member
 
Join Date: May 2011
Location: Upstate NY
Posts: 3,794

Bikes: Bianchi San Mateo and a few others

Mentioned: 18 Post(s)
Tagged: 0 Thread(s)
Quoted: 633 Post(s)
Likes: 0
Liked 4 Times in 4 Posts
Originally Posted by JohnFyf View Post
Such as the rim gets warped, but to a point where you can sort of bend it back into shape. Then true the wheel, but the problem is the wheel will never be properly dished because of the warp so there is an imbalance.
That last word is the key. If you use spoke tension to pull a bent wheel into true, the spokes will be tensioned unevenly. An unevenly-tensioned wheel won't be as strong or as durable, and is likelier to go out of true again.

Originally Posted by JohnFyf View Post
If you were to put this back on your bike and ride it as is would it be fine or could this end in disaster? How about if this were just a temporary fix until the replacement rim comes, and can the spokes be reused?
Whether or not I'd ride it isn't a black-or-white question. How unevenly tensioned is it? If it's not too much, I might ride it. If I'm riding long distances or carrying a heavy load, I'd be a little more picky about even tension. If tension is pretty darn uneven, riding it might be a question of how desperate I am. If my only choices are riding an unevenly tensioned wheel or walking, I might take my chances on the wheel.

As for reusing the spokes... If spokes been ridden some distance under uneven tension, they might have been subject to some fatigue from loading/unloading cycles. Going taut then slack repeatedly fatigues a spoke. A unevenly tensioned rim might deflect more during each rotation, adding to these stress cycles. A properly tensioned wheel minimizes stress by keeping each spoke under tension at all times.
SkyDog75 is offline  
Old 05-02-18, 12:18 AM
  #8  
50PlusCycling
Senior Member
 
50PlusCycling's Avatar
 
Join Date: Mar 2018
Posts: 337
Mentioned: 1 Post(s)
Tagged: 0 Thread(s)
Quoted: 165 Post(s)
Liked 56 Times in 34 Posts
You would be surprised how far you can bend a rim, and still get it back into shape, and properly trued. I've taco'd wheels in crashes, beat them straight enough to get me to the end of the ride, and usually got them true, and properly dished (if necessary) after getting home. Any real bike shop can re-dish your wheel, if you work on your bike long enough, you can eventually figure out how to do it yourself.
50PlusCycling is offline  
Old 05-02-18, 12:43 AM
  #9  
Oneder
Banned.
 
Join Date: Apr 2018
Posts: 822

Bikes: Wahoo of Theseus, others

Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 428 Post(s)
Liked 64 Times in 45 Posts
Truing the wheel should unbend the wheel most of the way even if it's not 100%. If you take the spokes off or unloose them all the way after truing then you can see what the rim does, and overtighten it in such a way as to rebend the affected areas if there are any. There should not be any irreverseable mathematics involved. You should only have to toss the wheel if the rim is not misshapen/untrued so much as deformed in a way that the beads don't sit right any more.
Oneder is offline  
Old 05-02-18, 02:26 AM
  #10  
OldTryGuy
Senior Member
 
Join Date: Jun 2013
Location: SW Fl.
Posts: 4,899

Bikes: 1981 Custom Touring Paramount, 1983 Road Paramount, 2013 Giant Propel Advanced SL3, 2018 Specialized Red Roubaix Expert mech., 2002 Magna 7sp hybrid, 1976 Bassett Racing 45sp Cruiser

Mentioned: 15 Post(s)
Tagged: 0 Thread(s)
Quoted: 816 Post(s)
Liked 276 Times in 181 Posts
When a customer would bring in a bent wheel, I would assess the degree of damage to determine if it was salvageable. If yes, I would relieve the spoke tension, "UNBEND" the rim to a point where when spun in the truing stand the rim would only be millimeters out of true then bring it into a properly dished/trued condition. NOTE: the rider's intended use of the wheel was very important in my decision regarding "to straighten or not." Same with SULKY wheels. I would true but not straighten a bent racing wheel.
OldTryGuy is offline  
Old 05-02-18, 12:18 PM
  #11  
WizardOfBoz
Generally bewildered
 
WizardOfBoz's Avatar
 
Join Date: Aug 2015
Location: Eastern PA, USA
Posts: 2,790

Bikes: 2014 Trek Domane 6.9, 1999 LeMond Zurich, 1978 Schwinn Superior

Mentioned: 20 Post(s)
Tagged: 0 Thread(s)
Quoted: 1039 Post(s)
Liked 241 Times in 178 Posts
There's another issue: material. Obviously, CF rims that are really distorted have had some major whack negative mojo. Discard.

Steel rims can probably be unlaced and bent so that they're a pretty true circle. Then you could relace them.

Aluminum rims that are severely distorted ... I'd be circumspect about trying to retruing them. I'd want to unlace the rim, then unbend it and then relace it. As other have pointed out, trying to retrue a severely bent rim using only the spokes could end up leaving a large imbalance in different spoke tensions. Which is why I said I'd unlace the rim to ensure that it was pretty true without spoke tension. By that time, you're probably better off just buying a new rim.
WizardOfBoz is offline  
Old 05-02-18, 01:01 PM
  #12  
RobotGuy
Semi-Pro Bowler
 
RobotGuy's Avatar
 
Join Date: Mar 2018
Location: New Joisey
Posts: 202

Bikes: ‘02 LeMond Tete De Course Titanium (road), ‘98 Gary Fisher Hoo Koo E Koo (mtb), ‘88 GT Mach One (BMX)

Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 101 Post(s)
Likes: 0
Liked 0 Times in 0 Posts
I’ve done it plenty of times. I once bought a nice Trek mountain bike almost for free for the wife with both wheels completely taco’d. Like, someone jumped up and down on the wheels.

cracked open a 6-pack and trued those babies up by rebending (stand on-method) and retensioning the spokes.

15 years later they’re still great.

of course, as stated by others, I’d never pull this on carbon wheels.
RobotGuy is offline  
Old 05-02-18, 01:26 PM
  #13  
ThermionicScott 
7-speed cultist
 
ThermionicScott's Avatar
 
Join Date: Aug 2011
Location: CID
Posts: 20,045

Bikes: 1991 Bianchi Eros, 1964 Armstrong, 1988 Diamondback Ascent, 1988 Bianchi Premio, 1987 Bianchi Sport SX, 1980s Raleigh mixte (hers)

Mentioned: 87 Post(s)
Tagged: 0 Thread(s)
Quoted: 2779 Post(s)
Liked 701 Times in 493 Posts
Originally Posted by WizardOfBoz View Post
Steel rims can probably be unlaced and bent so that they're a pretty true circle. Then you could relace them.

Aluminum rims that are severely distorted ... I'd be circumspect about trying to retruing them. I'd want to unlace the rim, then unbend it and then relace it. As other have pointed out, trying to retrue a severely bent rim using only the spokes could end up leaving a large imbalance in different spoke tensions. Which is why I said I'd unlace the rim to ensure that it was pretty true without spoke tension. By that time, you're probably better off just buying a new rim.
You don't need to completely unlace a wheel to straighten the rim -- that risks mixing up the spokes that had taken a set as heads-in or heads-out. Just detension the spokes a bunch until they're completely slack, and then there are ways to determine how warped the rim is.
__________________
Originally Posted by chandltp View Post
There's no such thing as too far.. just lack of time
Originally Posted by noglider
People in this forum are not typical.
RUSA #7498

Last edited by ThermionicScott; 05-02-18 at 01:28 PM. Reason: singular/plural coherence
ThermionicScott is offline  
Old 05-02-18, 04:28 PM
  #14  
GuessWhoCycling
Banned.
 
Join Date: Apr 2018
Posts: 398
Mentioned: 4 Post(s)
Tagged: 0 Thread(s)
Quoted: 95 Post(s)
Likes: 0
Liked 1 Time in 1 Post
You can straighten the rim but you can't get it dished properly because of the warp? WHAT?
GuessWhoCycling is offline  
Related Topics
Thread
Thread Starter
Forum
Replies
Last Post
bobbyl1966
Bicycle Mechanics
8
11-05-15 04:17 PM
TwoFourOne
Bicycle Mechanics
44
02-17-13 11:52 AM
TRAINING WHEEL
Bicycle Mechanics
3
12-27-11 07:26 AM
bloom87
Bicycle Mechanics
9
12-29-10 10:33 PM
Paultso
Bicycle Mechanics
2
08-27-10 08:45 AM

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


Thread Tools
Search this Thread

Contact Us - Archive - Advertising - Cookie Policy - Privacy Statement - Terms of Service - Do Not Sell My Personal Information -

Copyright © 2018 MH Sub I, LLC dba Internet Brands. All rights reserved. Use of this site indicates your consent to the Terms of Use.