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How the flatten a chainring?

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How the flatten a chainring?

Old 02-07-19, 07:20 AM
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le mans
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How the flatten a chainring?

It is slightly bent, any ideas how to panelbeat it straight?.. would be appreciated.

I was going to use a 48 tooth single chainring for a road bike 700c wheels 8 speed nexus 15 sprocket, but i'm guessing it would be way too tall

this was on the frame i'm using when i got it, have the matching peddle arm for the other side, i quite like the look of it.. so would like to use it for that reason as well, it's 42 teeth



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Old 02-07-19, 07:32 AM
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I have only used a large crescent wrench to straighten a chainring, work slow and they come out nice.
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Old 02-07-19, 09:11 AM
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Clamp it in a vise, use your hands to bend it flat. work slow so you don't over do it.
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Old 02-07-19, 09:49 AM
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You can straighten it on the bike using the FD cage as a guide to see any wobble.
Pretty simple job, just go slow and you should be fine.
Good luck
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Old 02-07-19, 10:06 AM
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Thanks guys, good suggestions

stevoo, what's a FD cage?
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Old 02-07-19, 10:08 AM
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front delralleur? nooo.. hasn't got one
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Old 02-07-19, 10:12 AM
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Sorry, missed that
A pencil taped to the seat tube where a FD theoretically would be also works well.
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Old 02-07-19, 10:16 AM
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Good idea, you could get that pretty precise using a guide of some sort, cheers

Last edited by le mans; 02-07-19 at 12:36 PM.
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Old 02-07-19, 10:18 AM
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The mind boggles how it dished out a bit, and bent out a bit more in one section?
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Old 02-07-19, 11:49 AM
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Not a thousand Wordsworth *

You riding it when you high sided & hit something? have a flat surface for comparison to know its perfect again ? say a Granite counter top?

have to put it on a BB spindle and rotate it with a fixed reference point for comparison (Like a Front Derailleur ) or your lathe tool rest..

yea pencil OK, but have to put the crank on the bike first...

holding it in the air against a blank background mostly demonstrated you has a camera no un flatness was to be seen ...

*other than computer code for the image..







....

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Old 02-07-19, 12:19 PM
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no it's something i collected, there's a scratch on the top tube so it must have been hit

high sided? well.. there ya go

but, after cold bending the dropout to suit the hub, the frame alignment is fine, very solid frame (Indi Australia)


"have a flat surface for comparison to know its perfect again ? say a Granite counter top?"

that centre fitting gets in the way, what holds the chainring & arm together, unless i find a flat surface with a hole in it

Last edited by le mans; 02-07-19 at 12:24 PM.
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Old 02-08-19, 02:13 PM
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Originally Posted by stevoo View Post
Sorry, missed that
A pencil taped to the seat tube where a FD theoretically would be also works well.
Used one of those plastic caliper sliding rulers, so i could slide it towards the chainring
found it wasn't all dish outwards, one section was bent inwards, didn't take long to fix!

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