Straightening a steel fork

[ededwards]

Ok, so had some contrasting opinions on what to do with a very slightly bent steel fork from some knowledgeable people so going to put it out to the great and good Retrobike experts!

Intended use is light (light is as light does) but with a 15 stone biffer aboard. Unlikely that I'll be attempting any drop offs or rad sickness. The views offered so far can be summed up as:

1) Don't worry unduly as it's a steel fork so there won't be a catastrophic failure. You're safe to ride it as long as you don't hammer it (so definitely safe with me) and bending it back will only weaken it further as will brazing on a gusset or similar

2) Bending it has work hardened the steel so no problem in bending it back straight as ling as you can construct a suitable jig.

Other thoughts?

 

[john]

Take it to a frame builder and get them to re-align it for you. Sure it'd be fine for some normal riding and walks down anything tricky.

 

[dyna-ti]

We do many frames in our workshop for second hand sale,usually bottom end spesh,treks gt's ect.
Some of them are bent so we bend em back and it's done more or less by eye
We use a long pry bar with one flat end and a standard rubber mallet
Hardly high tech
the only thing you need to be aware of is keeping the dropouts properly aligned.
Theres a pro tool for this and its really expensive but theres a two bolt method that is a cheap option that actually works
Screw a long bolt into each side of the drop out so the head is on the outside
Use long bolts so the ends are nearly touching.this will ensure you can check the drop outs remain properly aligned.you could run a nut from one to the other,if it slides straight across then thats a pretty good indicator

If its the steerer you're bending a nice big bench vice and a bit of grunting.
Little movements are the key here and a spare fork to check against.

Unless of course the frame builders only going to charge you £10-£20 then go with them.
Remember these are big strong steel tubes ,they really can take more abuse than many believe.

We realigned the rear triangle on a 08 hardrock a couple of weeks ago,the whole thing was seriously squint so when you put the back wheel in the tyre sat over an inch to the left.
I bent the triangle back in one stay at a time using a mixture of hitting it with the big rubber mallet and bending with the bar ,I did aligned the dropouts using the correct tool admittedly but overall it couldnt have been more than a couple of mm out
Helps if the frames in a robust workstand

 

[stew-b]

note to anybody thinking......DO NOT DO THIS WILL ALUMINIUM FRAMES/FORKS

 

[hamster]

I assume it's a welded crown not a brazed one? If it's brazed I'd be a bit more nervous.

 

[cyfa2809]

i think you would probably be alright on them as it is and maybe bent back for light riding but you have to remember that the structure has been stretched past its elastic limit and any further bending will keep stretching it thus weakining it more. but it is steel and has some give

 

[Anthony]

Doesn't it partly depend on:

a. how far out of true is it at the moment?
b. how thin gauge is the bit you need to bend back?

With respect to Dyna-ti for that useful information, surely the fact that a shop can straighten something and it'll look fine doesn't necessarily mean that the shop can know how strong it will be in future service, does it? Or is it just long years of experience and 'well, they don't bring them back'?

Saying that, I once had my clutch cable snap three miles down the road after my car was serviced, and I didn't thank the garage for having tightened it as part of the service.

 

[Jones]

Depends how far its got to be bent back and a what sort of fork it is :?: If its a cheapo heavyweight steel fork then I think your fine to bend it a little bit but if its anything light I'd bin it

I don't have much of a problem bending steel frames that are out of alignment but I've seen too many very bad crashes and injuries from catastrophic fork failure :shock:

With a frame you tend to hear a ping or notice somethings not quite right and then start crying when you realise your seatstay is doing its own thing :shock:

With a fork, if you wake up with the taste of blood in your mouth and a crowd around you you've been lucky :?

The trouble with forks is you don't have to be doing something silly all it takes is you having to brake hard and there's HUGE forces going through the fork :shock:

If we all started to think how much force is going through that skinny fork on the front of our bikes everytime we slam on the brakes ( especially if your 15 stone ) we'd never ride our bikes again

If it was me I'd bin it, plenty of cheap steel forks out there

 

[Tad]

What he said ^ seen a nasty one with a steel fork road that broke. Whilst I have a face that not even my mother can love my fear of ending up landing on it coupled with my allergy to gravity (it brings me out in bleeding and pain) would prevent me from riding it.

Where is it bent and what's the construction of the fork? The beauty of steel is that it can be repaired. Mr Yates is your man!

 

[ededwards]

Thanks guys but some conflicting advice so perhaps a bit more context will help.

The fork in question is not a cheap steel fork but a Colnago Prescia steel cross fork in Rabobank team colours so not really a disposable item (possible consequences notwithstanding) or one where I can easily get a replacement if at all.

The damage is visible via paint cracking just below the crown and you can feel the slightest undulation in the steel on the back of the fork. My instinct and the advice from a local frame builder (although sight unseen) says to leave it and ride lightly (as before I'm not rad or bad) but I don't want the Doubt Monkey to be sitting on my shoulder, whispering evil tidings.

Any further or new advice very gratefully received.