Thread: Is it safe to straighten a billet aluminium component?

Hi all,

First, I'm a sparky and know very VERY little about metal, so apologies for any terminology errors

I had an accident on my dirt bike a while ago and twisted one of the triple clamps. It is my understanding that they are billet aluminium, and I would like to understand if there is any risk associated with straightening them?

clamp.jpg

I have tested them on a straight edge and can confirm 100% they are twisted, I have take the photo on the wooden bench simply for convenience. It's about a 2mm twist.

So I really have 2 questions:

1. Is it safe to attempt straightening these?
2. If it is safe, what would be the best approach? Should I use heat and force, or force alone?

Thanks!

Hi there,

What's a triple clamp? What are the consequences to your safety of this triple clamp were to fail while riding?

Simon

I did a web search, and found lots of references to straightening these clamps, which connect the front fork tubes to the frame's steering head.

A billet of anything just means it's been machined from a solid piece, rather than cast as a liquid or forged in a plastic condition.
It doesn't tell us what the material composition is.
However, triple clamps are, as you've discovered, quite malleable. I guess they'd have to be, given the duty they have to perform, handling jolts and suspension loads.
They must have been subjected to much more of a load than normal. Anything more rigid could crack.

Jordan

Thanks for the reply guys.

Simon, the triple clamps, in particular the lower clamp in my case, are what hold the forks to the bike. You can think of it like a normal bike, but where as the fork legs are a single piece and are connected directly via the headstem on a push bike, on a dirt bike the forks are held in place by the triple clamps, which in turn are connected to the handlebars through the headstem. There is a good picture here:

https://www.krausmotorco.com/product...-front-end-kit

The vertical bars are the fork legs, the 2 black horizontal blocks are the triple clamps, you can see there is an upper and a lower. On mine, I managed to put a 2mm twist in the lower triple clamp. Consequences of failure, depending on speed could be catastrophic, hence my question to folks with actual metal working experience, as opposed to a ton of dirt bike riders with a great deal of opinions, but little to know practical knowledge

I would say you answered your own question by using the word 'catastrophic', if the cost of replacement is not thousands i would just swap it out for a new to-spec part.

Do what everybody else does, straighten them and sell them on Gumtree (don't actually do this lol)

Thanks guys.

Miraculously I found a complete set, BNIB for $400, should arrive next week.

I'm still really interested to understand billet aluminium though. Would straightening these introduce an issue, or would it likely be fine?

Well as a motorcyclist for some 30 plus years it was the eighties when it was accepted practice after a big toss that your triples trees would twist
at that time a simple visit to Bob Martin and drop them off to be picked up in two weeks etc but those days are long gone now done away by regulation, internet know it alls and insurance etc etc etc

However the rules are still the same, degrease paint strip , inspect for cracks no heat etc place in a big vice and clamp a turned slug through the bent eye and straighten may take a few goes but you will get them back to within 0.2 mm twist easily or less refer to your workshop manual

I still do it now I straighten my own forks etc triple trees straighten frames etc it was an accepted part of motorcycle mechanics

Good luck with it

Nothing new get a load of how it was done

Bruce

Originally Posted by gjws

I'm still really interested to understand billet aluminium though. Would straightening these introduce an issue, or would it likely be fine?

As was said before, billet does not give an accurate idea of what the actual material is. Remember how a bit of wire twisted back and forth will break due to fatigue at the bend point? The same will happen with aluminium. It just depends on how often it gets twisted about. As it has been machined, it will probably have a couple of cutter marks in it that will act as a stress raiser and help it crack. I don't doubt Aussie Bruce's experience but as they say, that was then, this is now. It may be the same alloy or then again it may be different. Bruce's triple clamps may also have been cast (if they were, it is almost certainly a different alloy)
You can try straightening but the risk becomes yours. I would certainly be checking before and after for cracks. You could ask the manufacturer but they are likely to say they should be replaced to avoid any liability.

Michael

Originally Posted by gjws

I'm still really interested to understand billet aluminium though.

Unfortunately "Billet Aluminium" is meaningless. It simply means that it was machined in one piece (or not) but doesn't say anything about the material, or how it may have been worked, treated, etc.

As a sparky it would be like somebody coming up to you and saying, I'm going to rewire my house, I'm going to use "copper", is that ok? I haven't told you anything about the run length, what size cable it is, what type of wiring, what it's for ... I haven't told you anything. No disrespect intended to you, but "Billet" is an idiotic expression that's often used in the auto aftermarket world because it sounds impressive but actually means pretty much nothing.

In regard your chances of successfully straightening them, I would probably pose the question to a forum specialising in that brand of dirt bike. You wouldn't be the first person to bend them, and the chances are you're also not the first person to want to straighten them either. I would guess they could be pressed, but to get them really straight is likely not a piece of cake.

Pete F, I love the analogy, clearly billet aluminium is a stupid term, because if you told me you were going to wire your house with copper, indeed I would look at you like an idiot

Unfortunately I don't know anything more about the manufacturing process or composition of the triple clamps at all, so I guess this ends here.

I have asked the same advice on a ktm forum, but all the responses are based on opinions, no one on there has an understanding of the true principles of metal working. I'm comfortable with my decision to buy a new set, I figure my life is worth more than $400. It does concern me that my wife was all for me straightening them, right after she asked if my insurance policy was paid up

Cheers all, and thanks again.

A toolmaker up here has as one of his strings in his bow, straightening large diameter "billet" aluminium axles (6061) for spools. Stuff can be done up to a point, but it's case by case - and then you run into the fatigue limitations of that material in particular.

Having had a front end failure on Marzocchi cast aluminium triples and magnesium lowers, it's not something to recommend I must say....fortunately happened in sand dunes for moi.

Hi gjws,

What I would add is that failure nodes of aluminium alloys tends to be different from steel. Often steel will show a crack which gradually opens before failing and the item falls apart. This gives you a chance to notice the crack and take action. Aluminium failures tend to be more good one minute with no visible cracks, completely failed the next, with no warning. Not saying that no one has ever sucessfully straightened a piece of ally. Personally, I would not attempt to straighten alloy on any critical structures. Once I had some understanding of what caused the different failure modes, sadly, lost in the mists of time.

Cheers

The Beryl Bloke

I agree with most of the helpful responses you had. I'm glad you found an affordable replacement.
Triple clamps like your KTMs are made by one of three methods:
cast (then machined where precision is required) - identifyable by slightly irregular surfaces where there is no machining; often a line somewhere around the middle where the molds were split to remove the cast part. Steel triple clamps are generally cast malleable steel.
forged (then machined where required as above) - slightly difficult to tell apart form castings, but generally quite smooth on any curved or flat surfaces. Parting lines from the dies may also be visible, though to the trained eye in different positions to a mold line. From the one photo, yours looks like a partially machine forging to me.
'billet', or more sensibly: 'fully machined'. Identifyable by obvious and generally very smooth machining marks on all or most surfaces. Typically, these triple clamps are a bit more angular, because machining curved surfaces are more expensive to do.
Forged and fully machined triple clamps will be safe to straighten within a small range (like yours) and is done by pretty well all well equipped motorcycle workshops with properly trained mechanics (as opposed to "part replacement technicians"). There is a bit of an art to it, learnt by experience. The guy doing it commercially will also invariably do an NDT (non-destructive test) with penetrant dye. When I was a Honda mechanic (in another lifetime) we had a guy doing nothing but straightening forks, triple clamps and frames - with proper jigs and proper tools and measuring gear. He was great to watch in between jobs and I learnt a lot from him.
Cast steel triple clamps are also safe to straighten. Aluminium cast ones I would NOT touch. It depends too much on the actual alloy used - and that will be too difficult to find out. Some are quite malleable, others are MUCH more likely to crack (possibly invisibly). Without proper testing gear, I would put it in the bin so nobody else is tempted to try either.
An analogy are the aluminium hand levers on bikes. Some can be straightened after a drop, others will immediately snap off. They all look alike in terms of alloy appearance....
Heating triple clamps to reduce the risk of cracking is not a good idea, because you would change the temper. After that, you will have no idea if the part is at all suitable for the task it is designed for.
I know this is just information for future use or interest for others, but you asked the right questions and should get the right answers.
I'm not a 'google expert', having ridden, worked on, made parts for and restored bikes for the past 50 years or so. So the above is based on practical learning and experience.
Hope it helps you decide next time.
PS: did your fork legs survive that mishap without getting a 'kink' line?