Ever run a bike with a bent frame? - The Jockey Journal Board

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Old 03-10-2012, 08:16 PM   #1
bikerbob
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Default Ever run a bike with a bent frame?

I dont have a frame jig and I have been mocking up a bike with this frame for a while and never noticed this until I was wet sanding it and flipped it over upsidedown. I have had a front end on it and rear wheel and never noticed it from the top side. Looked straight mocked up!
What do ya think?


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Old 03-10-2012, 08:33 PM   #2
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Default Re: Ever run a bike with a bent frame?

It's hard to tell from the photographs. I'd say that the most critical alignment is the steering head to the swing-arm. If they are aligned, you probably will never notice any problem. The only other alignment problem that can cause you fits is if the motor mounts (unit construction) or the gearbox mounts (pre-unit) do not align with the swingarm. The latter mis-alignment will cause you fits in getting the chain sprockets aligned.
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Old 03-10-2012, 08:37 PM   #3
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Default Re: Ever run a bike with a bent frame?

This is a hardtail and I have had Motor, Tranny, belt, Drive wheel and chain all mocked up and never saw it... I kind of feel like an idiot that I had not noticed it.
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Old 03-11-2012, 12:30 AM   #4
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Default Re: Ever run a bike with a bent frame?

Really hard to tell in pics , Most of the rigid frames I have dealt with are alittle off. Is you neck twisted in relation to the backbone? Thats the most crucial part.
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Old 03-11-2012, 06:47 AM   #5
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Default Re: Ever run a bike with a bent frame?

Quote:
Originally Posted by Loffer View Post
Really hard to tell in pics , Most of the rigid frames I have dealt with are alittle off. Is you neck twisted in relation to the backbone? Thats the most crucial part.
First pic is looking at the frame from the front motormount center from the bottom looking up at the neck
Second shows how straight the left leg is(on the right from the bottom) and the last pic if you look all the way up top to the neck you can see the bend
I dont think the neck is twisted in relation to the backbone..
I kind of was hoping what Neo Dutch said
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Old 03-11-2012, 12:55 AM   #6
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Cool Re: Ever run a bike with a bent frame?

I wouldn't beat myself up over it. Everything else lines up, etc. it can't be to far off. Get it fixed and continue the mission.



Quote:
Originally Posted by bikerbob View Post
This is a hardtail and I have had Motor, Tranny, belt, Drive wheel and chain all mocked up and never saw it... I kind of feel like an idiot that I had not noticed it.
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Old 03-11-2012, 12:35 AM   #7
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Default Re: Ever run a bike with a bent frame?

Break out the lazer and come along and straighten it out. No, never ridden on a bent frame. Wouldn't care to try.
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Old 03-11-2012, 12:40 AM   #8
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Default Re: Ever run a bike with a bent frame?

its prob a good thing you caught it now rather than later...
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Old 03-11-2012, 03:02 AM   #9
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Default Re: Ever run a bike with a bent frame?

Who says it's "bent"? If everything runs true then it's not really bent is it, just assymetrical.
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Old 03-12-2012, 01:14 PM   #10
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Default Re: Ever run a bike with a bent frame?

Quote:
Originally Posted by Neo Dutch View Post
If everything runs true then it's not really bent is it, just asymmetrical.

If the tubes were fitted by hand, that could explain the variation.

As long as the critical components are aligned correctly,
slight irregularities in the tubes are no problem.
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Old 03-11-2012, 07:31 AM   #11
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Default Re: Ever run a bike with a bent frame?

put the frame on blocks,use a spirit level across the bottom rails to level it,then put the spirit level down both sides off the neck and see if there is any
difference .
draw three lines in parallel, 8 inches apart on the floor the length of the bike
centre the frame along the middle line(plumb line from middle of rear axle and centre of neck) and level it across the bottom rails with the
spirit level.
stand a large square(make or borrow one)on the outer lines either side of the bike and
measure in to all parts of the frame,from both sides and look for any difference.
measure in to top and bottom of the neck from both sides.
i wouldnt worry about a couple of mm,its a bike,not an f16
....or....build it,ride it,if it doesnt run true,take the front end off and fix it.(would be my choice)
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Old 03-11-2012, 02:53 PM   #12
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Default Re: Ever run a bike with a bent frame?

Ever run a bike with a bent frame?

I'll put my ass-hat on and play the devils advocate and tell you the truth.

Sure I have, and if you have a bike that was hard tailed by somebody else (maybe even yourself ), you probabably have run a bike with an out of whack frame too. The truth is, that most frames that have been hard tailed have not been done so with much accuracy. Unless it's obvious to the eye or creates a serious handling problem, most chopper jockeys don't know the difference.

Most of the time, the only way you'll find out is if you check. A bono fide frame table is nice, especially when it comes to repairing and straightening, but not necesary. A couple of straightedges, a good level, a bit of plane geometry and basic trig knowledge (just basic shop math skills really), and some critical thinking are necessary and required. If you don't currently posess the requirements, they can be aquired with a little effort. Or, if you would rather not, find a trusted and reputable frame man with the knowledge and equipment to properly check and repair the frame.

And thats the truth. (and a tip of the ass-hat)

Regards,
Geo.
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Old 03-11-2012, 03:53 PM   #13
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Default Re: Ever run a bike with a bent frame?

night shift

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Old 03-11-2012, 05:04 PM   #14
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Default Re: Ever run a bike with a bent frame?

I'd argue that the salient points have been made with the expert advice above. The frame can be wildly assymetrical if the guide points are true.

I rode a Bonnie with a seized left front fork for a while before I figured out where the problem was. Very entertaining on the colleges speed bumps, hardly a problem at all on the street....
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Old 03-12-2012, 10:31 AM   #15
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Default Re: Ever run a bike with a bent frame?

Neck was bent on mine [after being run off the road] and really could'nt tell at slow speeds,turned out the frame was broke too,could feel it vibrate as RPM's went up,so I pulled her down and found this....also,if its bent alot,stuff's not gonna line up....my .02.....
good luck,have fun,keep the pics. coming,
GBM

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Old 03-14-2012, 08:01 PM   #16
bikerbob
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Default Re: Ever run a bike with a bent frame?

Quote:
Originally Posted by bandit View Post
put the frame on blocks,use a spirit level across the bottom rails to level it,then put the spirit level down both sides off the neck and see if there is any
difference .
draw three lines in parallel, 8 inches apart on the floor the length of the bike
centre the frame along the middle line(plumb line from middle of rear axle and centre of neck) and level it across the bottom rails with the
spirit level.
stand a large square(make or borrow one)on the outer lines either side of the bike and
measure in to all parts of the frame,from both sides and look for any difference.
measure in to top and bottom of the neck from both sides.
i wouldnt worry about a couple of mm,its a bike,not an f16
....or....build it,ride it,if it doesnt run true,take the front end off and fix it.(would be my choice)
Quote:
Originally Posted by old.wrench View Post
Ever run a bike with a bent frame?

I'll put my ass-hat on and play the devils advocate and tell you the truth.

Sure I have, and if you have a bike that was hard tailed by somebody else (maybe even yourself ), you probabably have run a bike with an out of whack frame too. The truth is, that most frames that have been hard tailed have not been done so with much accuracy. Unless it's obvious to the eye or creates a serious handling problem, most chopper jockeys don't know the difference.

Most of the time, the only way you'll find out is if you check. A bono fide frame table is nice, especially when it comes to repairing and straightening, but not necesary. A couple of straightedges, a good level, a bit of plane geometry and basic trig knowledge (just basic shop math skills really), and some critical thinking are necessary and required. If you don't currently posess the requirements, they can be aquired with a little effort. Or, if you would rather not, find a trusted and reputable frame man with the knowledge and equipment to properly check and repair the frame.

And thats the truth. (and a tip of the ass-hat)

Regards,
Geo.
Thanks, I think I will try your advice(If St Patricks day dont make my eyes to crooked this weekend, if not next weekend will have to do
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Old 03-11-2012, 03:40 PM   #17
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Default Re: Ever run a bike with a bent frame?

I agree if the wheels run straight and true it probably wont matter.thats where the geometry matters right ? the tubing can be bent like a pretzel as long as the axles align on the same plane and are true and plum
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Old 03-12-2012, 02:23 PM   #18
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Default Re: Ever run a bike with a bent frame?

"Sure I have, and if you have a bike that was hard tailed by somebody else (maybe even yourself ), you probabably have run a bike with an out of whack frame too. The truth is, that most frames that have been hard tailed have not been done so with much accuracy. Unless it's obvious to the eye or creates a serious handling problem, most chopper jockeys don't know the difference."
old wrench has it right.....most of these handle so evilly that a minor misalignment dont matter so much anyhow!
a buddy has a VW trike that is so far out of alignment that the 1/2 of the front tyre wears out in a yr or so...he SWORE it was from the "crown in the road" until i convinced him to let me ride it down the road and back........he was appalled! yet the bike does`nt display any more evil handling than your ordinary springer equipped VW trike!
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Old 03-12-2012, 03:58 PM   #19
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Default Re: Ever run a bike with a bent frame?

some well known frame makers tell you to check them now "due to the welding process...."

just keep to left turns :-)
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