Bent rim - Techniques?
#1
Senior Member
Thread Starter
Join Date: Oct 2016
Posts: 289
Bikes: Masi Giramondo, Trek 830 monstercross build, Raleigh Gran Sport, Lemond Tourmalet
Mentioned: 4 Post(s)
Tagged: 0 Thread(s)
Quoted: 121 Post(s)
Likes: 0
Liked 19 Times
in
12 Posts
Bent rim - Techniques?
Hi - I have a bent rim from my rear wheel sliding out from under me sideways in the mud and hitting a rail tie pretty hard on its side. When I tension the spokes to get it back in alignment, I end up with one super tense side, and one super slack side and the wheel is still bent. Looks to be about 5-7mm offset to the nds at its worst spot. The other 180 degrees of the wheel are still true. It's still round, but I can't keep my rear brakes from rubbing and still have a rear brake. What are some good techniques for bending the rim back closer to its original flat shape? I don't really want to get a new wheel or relace everything to a new rim if I don't have to.
#2
Banned
Slam the rim in the opposite direction as the bending action with equal force.. to get Newtonian on it..
Pringle bend or radial flat spot?
....
Pringle bend or radial flat spot?
....
Last edited by fietsbob; 02-13-18 at 09:57 PM.
#3
Senior Member
Join Date: May 2003
Location: Mountain Brook. AL
Posts: 4,002
Mentioned: 14 Post(s)
Tagged: 0 Thread(s)
Quoted: 303 Post(s)
Likes: 0
Liked 136 Times
in
104 Posts
Depends in part on how much of the rim is out of sorts. A tacoed wheel, one with a rim
that looks like the edge of a potato chip is hard to fix with spoke tightening without
fixing the rim first. If the bend is over 4-5 spokes you may be able to adjust it out
by spoke tensioning, but likely the wheel will not be 'like new'.
this video and others obtaining by google might help: https://www.google.com/search?ei=Jge...P5bM#kpvalbx=1
Back in the day of really light rims a tacoed or pringled rim was easy to pop back flat
and something I did several times. Youtube has several videos on ways to fix these,
then use fine tuning with spoke tensions. Radial irregularities are a little harder to
fix than axial ones.
Youtube: https://www.youtube.com/results?sear...+tacoed+wheels
that looks like the edge of a potato chip is hard to fix with spoke tightening without
fixing the rim first. If the bend is over 4-5 spokes you may be able to adjust it out
by spoke tensioning, but likely the wheel will not be 'like new'.
this video and others obtaining by google might help: https://www.google.com/search?ei=Jge...P5bM#kpvalbx=1
Back in the day of really light rims a tacoed or pringled rim was easy to pop back flat
and something I did several times. Youtube has several videos on ways to fix these,
then use fine tuning with spoke tensions. Radial irregularities are a little harder to
fix than axial ones.
Youtube: https://www.youtube.com/results?sear...+tacoed+wheels
Last edited by sch; 02-13-18 at 10:07 AM.
#4
I'm good to go!
Join Date: Jul 2017
Location: Mississippi
Posts: 14,949
Bikes: Tarmac Disc Comp Di2 - 2020
Mentioned: 51 Post(s)
Tagged: 0 Thread(s)
Quoted: 6177 Post(s)
Liked 4,794 Times
in
3,306 Posts
I'd loosen all the spokes to the last few threads. Then I'd try to bend it back into alignment as close as possible. Then I'd tension the spokes and see if I could pull it all back to true without too much tension on some or too little on other spokes.
It might be a futile effort if the bend is over a short section. The aluminum won't like flexing that much.
It might be a futile effort if the bend is over a short section. The aluminum won't like flexing that much.
Likes For Iride01:
#5
Senior Member
Thread Starter
Join Date: Oct 2016
Posts: 289
Bikes: Masi Giramondo, Trek 830 monstercross build, Raleigh Gran Sport, Lemond Tourmalet
Mentioned: 4 Post(s)
Tagged: 0 Thread(s)
Quoted: 121 Post(s)
Likes: 0
Liked 19 Times
in
12 Posts
As far as I can tell, the bend occurs over half the wheel. It is tacoed, not radial. Radially it appears true. I have 32 spokes, so the best way I can describe it is this way: The rim that corresponds to spokes 1-16 is true. The rim from spokes 17 through 24 goes from 0mm to 5-7mm out of true, and then over the course of spokes 25-32 returns back to 0mm/true. It doesn't look like a sudden bend, in fact I can barely see it from most views when I look across the rim braking surface held flat. The rim is an 18mm inner width Alex 26in mountain rim. Forget exactly which one.
The bigger question: Once I loosen the spokes, how should I go about straightening the rim? I have no prior experience and don't want to wreck the rim.
The bigger question: Once I loosen the spokes, how should I go about straightening the rim? I have no prior experience and don't want to wreck the rim.
#6
Senior Member
Join Date: Feb 2004
Location: St Peters, Missouri
Posts: 30,225
Bikes: Catrike 559 I own some others but they don't get ridden very much.
Mentioned: 16 Post(s)
Tagged: 0 Thread(s)
Quoted: 1572 Post(s)
Liked 643 Times
in
364 Posts
Without having seen your wheel:
1. Can you loosen all of the spokes and bend the rim back straight - maybe in a doorway? If so, get it as straight as you can, tension and true the spokes.
2. (My bet) If the above doesn't work, cut your losses and buy a new wheel. If it's a front wheel you might have luck finding a used one. Trying to use the spokes to pull a bent rim back straight isn't likely to be a lasting repair.
1. Can you loosen all of the spokes and bend the rim back straight - maybe in a doorway? If so, get it as straight as you can, tension and true the spokes.
2. (My bet) If the above doesn't work, cut your losses and buy a new wheel. If it's a front wheel you might have luck finding a used one. Trying to use the spokes to pull a bent rim back straight isn't likely to be a lasting repair.
__________________
My greatest fear is all of my kids standing around my coffin and talking about "how sensible" dad was.
My greatest fear is all of my kids standing around my coffin and talking about "how sensible" dad was.
#7
Senior Member
Join Date: Jul 2014
Location: Central Indiana
Posts: 2,159
Mentioned: 27 Post(s)
Tagged: 0 Thread(s)
Quoted: 912 Post(s)
Liked 515 Times
in
344 Posts
Simple. Remove all spokes so bare rim can sit on a flat surface. If you don't have a bench big enough, use the floor. Use boards, body weight, leverage. No striking. Lots of videos on line for visual guidance. Get it as close as you can befor re lacing.
Likes For FBOATSB:
#8
Really Old Senior Member
Hi - I have a bent rim from my rear wheel sliding out from under me sideways in the mud and hitting a rail tie pretty hard on its side. When I tension the spokes to get it back in alignment, I end up with one super tense side, and one super slack side and the wheel is still bent. Looks to be about 5-7mm offset to the nds at its worst spot. The other 180 degrees of the wheel are still true. It's still round, but I can't keep my rear brakes from rubbing and still have a rear brake. What are some good techniques for bending the rim back closer to its original flat shape? I don't really want to get a new wheel or relace everything to a new rim if I don't have to.
Trying to tension both sides the same will "pull" the rim way over to the NDS.
Notice the differing "angles" the spokes run between DS & NDS? The NDS has a MUCH greater effect on dish-
That said, I did something similar to my rear wheel when I did a nose stand with my new to me then Globe.
The wheel went about 3-4' in the air and banged down hard as I was "stepping off" to the side.
I had a rather nasty "Pringle".
I loosened all the spokes to the 1st thread and the rim WAS FINE. I just built the tension back evenly and had a "straight" wheel.
It was simply so poorly tensioned, it was looking for an "excuse" to go out of whack.
So- Don't start banging on the rim until you have loosened ALL the spokes first.
#9
Senior Member
Join Date: Mar 2008
Posts: 8,688
Mentioned: 46 Post(s)
Tagged: 0 Thread(s)
Quoted: 1074 Post(s)
Liked 295 Times
in
222 Posts
I’ve never had much luck re-bending rims while laced.
My favourite approach is to unlace, place rim with low spots on a broom handle, hockey stick etc, then step on the high spots.
Once flat to <3 mm, you have a decent chance of getting it rideably true with acceptable spoke tension variation.
My favourite approach is to unlace, place rim with low spots on a broom handle, hockey stick etc, then step on the high spots.
Once flat to <3 mm, you have a decent chance of getting it rideably true with acceptable spoke tension variation.
Likes For dabac:
#10
Mechanic/Tourist
First you need to determine what type of bend you have. The spoke tension will need to be more even than it is now in order to do so. Probably a good idea to release most of the tension to make sure the rim is actually bent, rather than temporarily distorted.
If the bend is U shaped then you need to just bend the middle while pulling or supporting the two sides. As you see above, there are a variety of approaches, from slam it on the floor, to push with your knee and pull with the hands, to using a doorway or levering it.
If it is an S shape (sharp right then left, and gradual return to the right) then you would need to place it in some sort of gap and carefully twist in the opposite directions - MUCH harder to correct.
If the bend is U shaped then you need to just bend the middle while pulling or supporting the two sides. As you see above, there are a variety of approaches, from slam it on the floor, to push with your knee and pull with the hands, to using a doorway or levering it.
If it is an S shape (sharp right then left, and gradual return to the right) then you would need to place it in some sort of gap and carefully twist in the opposite directions - MUCH harder to correct.
#11
Senior Member
Join Date: Feb 2012
Location: Golden, CO and Tucson, AZ
Posts: 2,835
Bikes: 2016 Fuji Tread, 1983 Trek 520
Mentioned: 13 Post(s)
Tagged: 0 Thread(s)
Quoted: 674 Post(s)
Liked 738 Times
in
429 Posts
I have had very good luck straightening bends (smaller than yours, but over 90 degrees of arc) while laced. Inflate your tire, swing it from about head height onto a hard floor. Watch for the rebound! Don't hit the rim on the floor. Gauge success by the tension in the spokes. Mark the center of the bend with an arrow showing which way to hit. Start with smaller swings. I have rescued quite a few wheels with this method, including on my daily rider. I would definitely try it on a larger bend like yours.
Deflate the tire before final truing with spokes.
Deflate the tire before final truing with spokes.
#12
Senior Member
Thread Starter
Join Date: Oct 2016
Posts: 289
Bikes: Masi Giramondo, Trek 830 monstercross build, Raleigh Gran Sport, Lemond Tourmalet
Mentioned: 4 Post(s)
Tagged: 0 Thread(s)
Quoted: 121 Post(s)
Likes: 0
Liked 19 Times
in
12 Posts
Thanks everyone. It appears to be true within about 1mm again. Tension even seems pretty uniform! EDIT: looks like I have it tensioned a couple mm to the nds. But rolling smoothly either way. Test ride felt good but I will probably check the tension again after the next couple rides.
Last edited by bcpriess; 02-13-18 at 09:08 PM.
#13
Senior Member
Join Date: May 2003
Location: Mountain Brook. AL
Posts: 4,002
Mentioned: 14 Post(s)
Tagged: 0 Thread(s)
Quoted: 303 Post(s)
Likes: 0
Liked 136 Times
in
104 Posts
Thanks for the followup. You may hear pinging in the wheel when you ride it, a manifestation of the tendency of tight
spokes to twist when the nipple is turned so the nipple just winds up the spoke instead of screwing down the spoke
thread. I used to take the wheel off the stand and put it on the floor vertically and bounce my weight on the rim
with my hands as the rim was rotated around a hemi-circumference. This results in a lot of pinging and then you
re-true and repeat til the rim is true and all pings are gone. Flat spokes can be gripped with a smooth jawed pliers
to minimize spoke windup. Bouncing on a wheel with tire on it doesn't work so well, need to have tire off.
spokes to twist when the nipple is turned so the nipple just winds up the spoke instead of screwing down the spoke
thread. I used to take the wheel off the stand and put it on the floor vertically and bounce my weight on the rim
with my hands as the rim was rotated around a hemi-circumference. This results in a lot of pinging and then you
re-true and repeat til the rim is true and all pings are gone. Flat spokes can be gripped with a smooth jawed pliers
to minimize spoke windup. Bouncing on a wheel with tire on it doesn't work so well, need to have tire off.
Last edited by sch; 02-14-18 at 12:55 PM.
#14
Senior Member
Join Date: Feb 2012
Location: Rochester, NY
Posts: 18,056
Bikes: Stewart S&S coupled sport tourer, Stewart Sunday light, Stewart Commuting, Stewart Touring, Co Motion Tandem, Stewart 3-Spd, Stewart Track, Fuji Finest, Mongoose Tomac ATB, GT Bravado ATB, JCP Folder, Stewart 650B ATB
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 4195 Post(s)
Liked 3,837 Times
in
2,295 Posts
Without having seen your wheel:
1. Can you loosen all of the spokes and bend the rim back straight - maybe in a doorway? If so, get it as straight as you can, tension and true the spokes.
2. (My bet) If the above doesn't work, cut your losses and buy a new wheel. If it's a front wheel you might have luck finding a used one. Trying to use the spokes to pull a bent rim back straight isn't likely to be a lasting repair.
1. Can you loosen all of the spokes and bend the rim back straight - maybe in a doorway? If so, get it as straight as you can, tension and true the spokes.
2. (My bet) If the above doesn't work, cut your losses and buy a new wheel. If it's a front wheel you might have luck finding a used one. Trying to use the spokes to pull a bent rim back straight isn't likely to be a lasting repair.
+1 on both parts. Andy
#15
Senior Member
Thread Starter
Join Date: Oct 2016
Posts: 289
Bikes: Masi Giramondo, Trek 830 monstercross build, Raleigh Gran Sport, Lemond Tourmalet
Mentioned: 4 Post(s)
Tagged: 0 Thread(s)
Quoted: 121 Post(s)
Likes: 0
Liked 19 Times
in
12 Posts
Here's what I did.
1) I loosened all the spokes until about 3 threads were showing. This was to ensure that all the nipples turned freely and I had enough slack for the rim to relax into whatever shape it was in.
2) I was then able to see the bend. It was king of a "j" shaped bend when the wheel was viewed in profile, covering about 120 degrees of the wheel. i.e. two bends in the same direction 120 degrees apart, just as one would assume with the type of side impact I experienced.
3) I blocked up under the inflection point of the bends, and stood on the rim on opposite sides, checking visually and on a flat surface until I felt it was pretty flat. After a dozen or so repeats, this got the rim straight enough to work with.
4) I reattached the wheel to the frame (no truing stand)
5) I numbered every other spoke with a sharpie on the braking surface since they all look the same and I needed reference points.
6) I began retensioning the spokes with full turns the first few turns until the obvious slack was taken up.
7) I began going by half turns at this point, taking care to keep the rim spinning straight.
8) As I was doing this, I flicked the spokes to see if they produced generally similar pitches. Knowing the rim was imperfect, I knew there would be some inconsistency as certain spokes needed more tension than others to compensate.
9) With the front wheel as a guide, I tensioned the spokes while visually checking alignment, until the spokes had a similar pitch to the spokes on the front wheel.
10) Eventually, by focusing more specifically on spokes in a couple locations, I was able to straighten the wheel.
11) After doing this, I checked all the other spokes' tension by feel and approximate pitch, and went about tightening up any spokes that had become relatively loose until all felt and sounded similar in tension.
Took me about two hours. For my first time, I think it went well.
1) I loosened all the spokes until about 3 threads were showing. This was to ensure that all the nipples turned freely and I had enough slack for the rim to relax into whatever shape it was in.
2) I was then able to see the bend. It was king of a "j" shaped bend when the wheel was viewed in profile, covering about 120 degrees of the wheel. i.e. two bends in the same direction 120 degrees apart, just as one would assume with the type of side impact I experienced.
3) I blocked up under the inflection point of the bends, and stood on the rim on opposite sides, checking visually and on a flat surface until I felt it was pretty flat. After a dozen or so repeats, this got the rim straight enough to work with.
4) I reattached the wheel to the frame (no truing stand)
5) I numbered every other spoke with a sharpie on the braking surface since they all look the same and I needed reference points.
6) I began retensioning the spokes with full turns the first few turns until the obvious slack was taken up.
7) I began going by half turns at this point, taking care to keep the rim spinning straight.
8) As I was doing this, I flicked the spokes to see if they produced generally similar pitches. Knowing the rim was imperfect, I knew there would be some inconsistency as certain spokes needed more tension than others to compensate.
9) With the front wheel as a guide, I tensioned the spokes while visually checking alignment, until the spokes had a similar pitch to the spokes on the front wheel.
10) Eventually, by focusing more specifically on spokes in a couple locations, I was able to straighten the wheel.
11) After doing this, I checked all the other spokes' tension by feel and approximate pitch, and went about tightening up any spokes that had become relatively loose until all felt and sounded similar in tension.
Took me about two hours. For my first time, I think it went well.
Likes For bcpriess:
#16
C*pt*i* Obvious
Big bends can cause fatigue cracks.
Another big hit and that wheel is likely to be finished.
I keep a spare rim on standby, quicker and safer than making major corrections.
Another big hit and that wheel is likely to be finished.
I keep a spare rim on standby, quicker and safer than making major corrections.
#17
Senior Member
Join Date: Feb 2012
Location: Rochester, NY
Posts: 18,056
Bikes: Stewart S&S coupled sport tourer, Stewart Sunday light, Stewart Commuting, Stewart Touring, Co Motion Tandem, Stewart 3-Spd, Stewart Track, Fuji Finest, Mongoose Tomac ATB, GT Bravado ATB, JCP Folder, Stewart 650B ATB
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 4195 Post(s)
Liked 3,837 Times
in
2,295 Posts
This type of repair really should be considered like a cat loosing a bunch of it's 9 lives. How many more are left? How important is it for your wheel to be reliable? How much is that reliability worth?
When I invest in new rims I buy 2 times the number I'll initially use (I am married to a rider so sometimes this means 8 rims) so I'll have back ups for a while after the rim model is no longer offered. Andy
#18
Senior Member
Thread Starter
Join Date: Oct 2016
Posts: 289
Bikes: Masi Giramondo, Trek 830 monstercross build, Raleigh Gran Sport, Lemond Tourmalet
Mentioned: 4 Post(s)
Tagged: 0 Thread(s)
Quoted: 121 Post(s)
Likes: 0
Liked 19 Times
in
12 Posts
I don't think it was as big a bend as you're picturing. My best guess is it was bent out about 5mm. I think the spokes may have pulled it farther initially in kind of an "over center" effect, since it was in that 5-7mm range when the spokes were tight. It was hard to see the bend at first when I couldn't put it on a flat reference surface and with tense spokes interfering with my line of sight.
#19
C*pt*i* Obvious
My rule of thumb, if it still turns in the frame, its usually salvageable, beyond that its too much of a risk IMO.
#20
Senior Member
Thread Starter
Join Date: Oct 2016
Posts: 289
Bikes: Masi Giramondo, Trek 830 monstercross build, Raleigh Gran Sport, Lemond Tourmalet
Mentioned: 4 Post(s)
Tagged: 0 Thread(s)
Quoted: 121 Post(s)
Likes: 0
Liked 19 Times
in
12 Posts
Yeah, it was turning fine, just couldn't connect the brakes and also have it turn w 5-7mm of wobble. Since I'm pretty careful about obstacles, I haven't had to deal much with untrue rims. So that may have made it seem like a bigger deal than it was.
#21
Senior Member
How long does it take to build a wheel? Price that at minimum wage; if you're as slow as I am, it swamps the price of a new rim. A wheel isn't iron; it has internal structure from its manufacture that is permanently damaged when it's been bent this badly: it never recovers (unless you heat it up to a high-enough temperature then anneal it properly).
I tried this once, the wheel wobbled (though it was true & round & tight) because it was no longer uniformly strong; it made unnerving high-pitched pings; the tightest spokes broke: it was a huge waste of time.
I tried this once, the wheel wobbled (though it was true & round & tight) because it was no longer uniformly strong; it made unnerving high-pitched pings; the tightest spokes broke: it was a huge waste of time.
#22
Full Member
Join Date: Sep 2015
Location: Denver Colorado
Posts: 339
Bikes: 2020 Pivot Vault, 1983 Rossin Record, Garneau R1, Mesamods home built gravel/rain commuter bike, 1995 Barracuda A2V modified with Surley single speed dropouts, 1969 Bottecchia junkyard special fixed gear, Cervelo P4, Mesamods 650b klunker
Mentioned: 3 Post(s)
Tagged: 0 Thread(s)
Quoted: 96 Post(s)
Liked 72 Times
in
50 Posts
Likes For Le Mechanic:
#23
Mechanic/Tourist
#25
Full Member
Join Date: Sep 2015
Location: Denver Colorado
Posts: 339
Bikes: 2020 Pivot Vault, 1983 Rossin Record, Garneau R1, Mesamods home built gravel/rain commuter bike, 1995 Barracuda A2V modified with Surley single speed dropouts, 1969 Bottecchia junkyard special fixed gear, Cervelo P4, Mesamods 650b klunker
Mentioned: 3 Post(s)
Tagged: 0 Thread(s)
Quoted: 96 Post(s)
Liked 72 Times
in
50 Posts
Likes For Le Mechanic: