My mech exploded while riding the other day - not quite sure what happened as it was on a fireroad.
Anyway, I've gone to fix a new mech and noticed the mech hanger is slightly bent - anyone bent back an Aluminium mech hanger? Any tips?
It can often be done. I prefer to take it off the bike and flatten it between the jaws of a vice but that depends on the shape. Best to buy a replacement in any case and keep the current one as a trail-side emergency spare.
Did one this morning. I took it off the bike and held the thick bit in a big adjustable spanner, then using a smaller pair of grips, straightened the thinner bit carefully until it was straight enough by eye.
What scotroutes said, particularly around using it as an emergency spare.
Exactly as scotroutes said. I've had a terrible run of luck so far this year having bent 2 hangers and snapped 1 (and also bent 3 rear mechs as it happens) I have straightened the 2 bent hangers and keep them in my pack as 'get me home' options, with a new one fitted on the bike.
Its a total myth that you can't straighten them (though a big bend or cheap hanger may be marginal).
I wouldn't just keep it as a spare either, it'll never get used, if it does you'll just buy another - waste of money.
cynic-al, riding on a straightened hanger for 4 years...
OK, Looks like I'll need a new one then.
Now the choice is going to be do I go for [url= http://soshanger.com/epages/box11137.sf/en_GB/?ObjectPath=/Shops/box11137/Products/%22200521/SCT%22&ViewAction=ViewProduct ]Thru axle[/url] or [url= http://soshanger.com/epages/box11137.sf/en_GB/? ]QR (which would be a replacement for what I've got and give me the old one as a spare)[/url]
Suppose it'll depend on the benefit of Thru axle over QR.
Depends a little on the hanger and the material- my hemlock ones are pretty delicate, they always crack in the same place so there's a hard limit to how much bending/resetting they can take. Others can last for ages. It might be worthwhile heating it first but I've never bothered.
(I use the QR wheel axle technique to straighten them, perfect results every time. I tend to check hangers every time I have a wheel out and every time i'm doing anything to anyone else's bike, they're squint more often than not.)
QR wheel axle technique
What's this? I'm intrigued
anyone bent back an Aluminium mech hanger?
Err yeah several times 😕
If it's just slightly bent, slightly bend it back using pliers. Have never had a problem tbh
I guess its screwing in a hub axle (same thread as the mech, M10 x 1mm) to act as a lever to straighten it.
Ive found an adjustable spanner works OK.
I bent one back about 7 years ago, it's still going strong.
Hmmmm... only slightly bent... Off to get adjustable spanner.
Damn - the dropouts are too burly to bend back.
Bushwacked - MemberWhat's this? I'm intrigued
Al's got it. The advantage over an adjustable spanner is that it gives you a perfect line to judge straightness- so stick a straight edge in the dropouts (I use some random bar but it doesn't really matter) and getting it perfectly straight is effortless since you just have to get the 2 "lines" parallel.
What hanger is it? They need to be pretty beasty to be totally unstraightenable. Though, you get to a point you've got to be careful not to unstraighten the frame too 😆
Put it in the biggest vice you can find.
Straightened mine maybe 3 or 4 years ago, still going.
Scott IDS dropout on my Scott Voltage.
cynic-al - Member
Its a total myth that you can't straighten them
that's right you can straighten them but it will induce cracking. That is the nature of heat treated aluminium alloys - as above some people haven't died and posted to tell us, others are in holes in the woods wondering what happened to them
Scott IDS dropout on my Scott Voltage
Ah OK there's hangers and there's Scott Voltage hangers. Would not attempt to bend one of those bad boys 🙂
Let us know how you get on
I've never actually done it, but with the axle method you could also put an extension on the axle and apply, well, more leverage than you could possibly need even with a chunky hanger like that. But that definitely increses the risk that instead of straightening the hanger you bend the frame or otherwise damage it.
what effect would heating have on it?
other advantage to using an old axle to align is that reduce the chance of damage to the mech hangar thread
as above, the more leverage you have the more securely and accruately held you need the hangar/frame.
on the subject why have hangers seem to have become more beefy over the years, they used to be a sacrificial item which would self destruct to save the rear mech.
These days the hanger appears to be stronger than the frame it's attached to!
antigee - Member
cynic-al - Member
Its a total myth that you can't straighten them
that's right you can straighten them but it will induce cracking. That is the nature of heat treated aluminium alloys - as above some people haven't died and posted to tell us, others are in holes in the woods wondering what happened to them
Irrespective of whether it can, there are plenty of people around who have straightened them without issue.
what effect would heating have on it?
Make it hotter? 😉
Assuming it's a precipitation hardened alloy (6061, etc), then heating it enough to make a difference would turn it to butter (well make it ridiculously soft, anyway). It would need a specific heat treatment schedule to restore its strength (soaking at specified temperatures for specified times) - generally to be avoided for d-i-y.
Just bend it back, it's useless as it is, anyway. If it starts to crack, then bin it.
While out on a ride I decided I'm gonna get the thru axle and a spare dropout which makes the QR dropout redundant - will get the creme brule torch on it and give it a try though.
antigee - Memberthat's right you can straighten them but it[s] will[/s] may induce cracking.
FTFY.