Frame warping?

mr.b-campag

Hi,

I put my bike in for a service recently. I was happy with the work done, but they noted that the frame alignment was affecting the gears on their check out sheet. When I queried this they said 'Frames warping slightly is just something that happens over time and it’s not something that mechanics can fix I’m afraid.' That's not something I've ever heard of, and a quick internet search doesn't bring back any results - are they just trying to fob me off because they're super busy?

As background I had a rear-mech explode on me a while back (subject of another thread) and the shifting has never been right subsequently, even though other shops have tried to fix it, so I'm assuming that is the more likely cause of the problem. It's not an old bike (about 3.5 years) and as I intend to use it for some time yet should I be asking them to do their job properly (as it was supposed to be covered in the servicing) or is there some specific place anyone knows on here (in London or close by) that would be able to do it properly?

Thanks in advance for any responses.

Mr.B

focuszing723

With a rear mech alignment tool the gear hanger could be adjusted to compensate for any miss alignment with the frame.

https://www.youtube.com/watch?v=tXfvW0L3iLM

me-109

Technically the alignment tool would align the hanger with the rear wheel, not necessarily the chain line or centre line of the bike. Badly set or worn dropouts, or a rear triangle bent in a crash, would give a wrong setting.

focuszing723

Yes that's true. I guess I was making reference to this statement 'As background I had a rear-mech explode on me a while back (subject of another thread) and the shifting has never been right subsequently'.

Wheelspinner

What material is this (allegedly) warped frame made of?

mr.b-campag

Thanks everyone for your responses. The frame has never been crashed (touch wood) but as stated I had a 6800 rear mech explode on me which I assumed bent the hanger rather than the frame. The frame is aluminium. As I said I've taken it into a bike shop before (Decathlon as its one of theirs) and I'm pretty sure they used the tool that fz pointed out but weren't able to fix the issue. The bike is an ultra 720 AF with an aluminium frame.

veronese68

It sounds unlikely anything other than the gear hager on the frame is so out of whack that it's affecting gear shifts, I suspect BS on the part of the repairer.

Wheelspinner

I know frames can be out of alignment from manufacturing defects (ask @step83 ), basically caused by distortion in the jig when they are originally welded up. But that's fairly uncommon, and means it would have been no good from day one.

To "warp" means the material has basically deflected beyond the elastic limit, i.e the point below which even if it bends and twists under load it normally springs back to original shape.

Metal fatigue may eventually lower that limit point at which behaviour becomes plastic rather than elastic, but at a few years old would seem unlikely, especially far enough for you to cause a problem riding it.

Unless you are Robert Forstemann, and ICMFP!

me-109

I'd agree without a crash the frame should not be that bent, so a new gear hanger should fix it, if not already replaced. If it has, then it is either time for new cables or new mechanics!

mr.b-campag

Thanks again everyone. New cables were just put in, hence how this came about. I'm happy to buy a new gear hanger if that will fix it. Are you sure that would do something the alignment tool wouldn't? Maybe I should just give that a go? I am slightly annoyed that they've tried to fob me off with som bs tho.

veronese68

mr.b-campag said:

I'm happy to buy a new gear hanger if that will fix it. Are you sure that would do something the alignment tool wouldn't? Maybe I should just give that a go? I am slightly annoyed that they've tried to fob me off with som bs tho.

No, a new hanger should be checked anyway with an alignment tool anyway. I had problems after I built my bike up from new frams and parts, turned out the hanger wasn't quite right from new.
It could be the mechanic was trying to tell you the hanger was bent in some really clumsy manner, but why didn't he just say so. Unfortunately I think some people would rather make something up than confess they can't do whatever needs doing.

mr.b-campag

Thanks veronese68, I think that probably hits the nail on the head. I'll go back to them and see if I can get any sense a second time 'round.

lesfirth

Unless I know I am 100% right I tend to keep my opinions to myself. When I first read the opening post my instinct told me," that sounds like bullsh1t". It looks like my instinct should have told me,"that is bullsh1t".

First.Aspect

I wonder if they just couldn't get the shifting indexed and fobbed you off. Different chainsets produce different chain lines anyway... as does changing gear. So the "warped frame" reasoning is meaningless, even if it was code for a marginally misaligned frame.

But you'd imagine that they wouldn't send a customer back out on a "warped frame" anyway, for safety reasons, no?

To be honest sounds to me like they can't be arsed. And if they can't be arsed first time around you might be better to take your custom elsewhere.

mr.b-campag

ok they've come back and said the frame is misaligned due to a manufacturing defect or metal fatigue (I guess this what they mean by warped). As the bike was fine from new and is relatively new I don't think it is either of those things. WIthout wishing to repoen a previous thread could my 'exploding' rear mech have caused that? It does have a lifetime warranty so perhaps I need to go back to Decathlon.

veronese68

The exploding mech could certainly have caused a bent hanger, but the point of the hanger being sacrificial is to save the frame from damage. Unless the explooding mech came round with the wheel and bent the chainstay I would say it has not damaged the frame.
You could go to Decathlon and say another shop said they couldn't index the gears properly as the frame is misaligned either due to a manufacturing fault or metal fatigue. As either of these should be covered under a lifetime frame warranty hopefully they will check it out for you. But they'll probably tell you a bike that's only a few years old will not be warped through metal fatigue.
I'm sure the bike is fine and if the gears work well enough not to spoil the pleasure of riding enjoy the bike and keep riding.

mr.b-campag

Thanks again. It's certainly fine to ride for now, esp. as there don't seem to be any races on the horizon. I think I'll do what you suggest until the winter when I get my hack bike out and see what they say.

First.Aspect

If they really think it's metal fatigue they should have shown you the crack that is propogating. This is not something that changes the a tube into something banana shaped.

And if the frame is misaligned enough to cause indexing problems it would never have been indexed in the first place.

Don't use this shop again, please. They don't want to fix your bike, or can't. It doesn't matter, really.