(RS) Steerer tube replacement? Is it the done thing? How safe?

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(RS) Steerer tube replacement? Is it the done thing? How safe?

68 posts & 24 voices | Started 2 years ago by james | Latest reply from BigJohn

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james - Member

"impact that breaks the fork, bends the frame and breaks the headset"
The fork isn't actually broken, the steerer tube is 'only' bent at a stress riser* where the steerer tube changes from a much thicker thickness to a narrower thickness relatively suddenly

Only the lower end of the headtube (the unsupported/ungussetted) where the headset sits was slightly ovalised. The headset cup has been refitted into the 'normal' position with some liquid metal filling the little gap behind the headset cup (which isn't as deep as the headset cup)

The headset cup is fine

*I think this is correct?

"if you are really concerned just crack test the crown too to be on the safe side. (you will have to lose the paint on it to do that though"
So if it had been near to breaking point then there should/ought to be signs of flakey paint/stressed paint?

Posted 2 years ago #
tinsy - Member

I dont know about that, its not like its going to cost a load more to find out, but if your confident there isnt a problem with it, its your call.. They can test it will aerosol crack testing stuff, would take about 10 mins with the paint removed from it.

Posted 2 years ago #
james - Member

How does a crack test work then? ie, will it break the crown (if its not already)? Like testing to (or near to) destruction?

Hmm, At least if the outcome of a crack test was favourable enough to ride I could have a unique* silver RS fork crown?

*I assume

Posted 2 years ago #
wwaswas - Member

Also, cut one of the legs off and fashion it into a lefty.

my view: my looks (such as they are) and skull are worth more to me than the cost of a knackered set of donor forks with the steerer still attached and decent set of stanchions.

You may get all this working (but as has been said - if the steerer was fairly easy to remove then suspect further damage elsewhere) but would you trust your life to it?

Posted 2 years ago #
coffeeking - Member

Worth a punt if I'm honest, if you can get a second steerer and press it out without damage. Local workshop will do the job for you for £20-30 I suspect. They could, as said above, also probably turn you a new steerer if they're any good, but that would be more pricey.

Posted 2 years ago #
james - Member

"but would you trust your life to it"
Not at the moment, but am interested in trying to determine how (un)safe it could be made, even if I don't ride it

I could always buy a full face helmet ..

Posted 2 years ago #
Nick - Member

I am I right that 5 mm of press fitted pipe is all that is holding the forks and the frame together? Gulp.

It would have to be a fooking tight fit wouldn't it?

Posted 2 years ago #
james - Member

About 15mm, with a wider bit at the bottom edge

If you think about a stem clamped upto a steerer tube, you're only meant to do the bolts upto about 5-10Nm?

Posted 2 years ago #
tinsy - Member

Nick its how wheels are held onto trains, just interference fit, and lots of bits inside your car engine, axle, etc etc..

When I bought my last motorbike the fork stanchions were so bent the wheel was on the frame, i bought it as right off to build into a road/track bike, the stanchions were straightend and I checked nothing else bar going over the bike as best as possible, it was entirely at my own discretion as your repair is for you.

Old nail built up from scrap stuff.

and after the first track day.

The frame your forks were on is prebably a week point to be honest and I would keep a close eye on it.

Posted 2 years ago #
cynic-al - Member

5mm?

It's an unknown as to whether the frame/crown will have been weakened - and you may not find out until you experience similar forces again - in which case you are crashing badly anyway.

Who replaces the frame after bending forks?

If the steerer goes in easily I don't think I'd ride it as the crown will have stretched.

Posted 2 years ago #
BigJohn - Member

A fair few areas around the headtube have got flaking paintwork as a result of it too though

So if it had been near to breaking point then there should/ought to be signs of flakey paint/stressed paint?

Just throw it away

Posted 2 years ago #
tinsy - Member

cynic-al, but you could ream the crown hole and go up a size on the new steerer if he was to go down the route of getting one made. Were only talking hundredths of a mm here.

The thing is, if in doubt bin em out. Give you postage for them

Posted 2 years ago #
coffeeking - Member

"bin em out"?! What's this, making up phrases to fit a ryhme ?

Posted 2 years ago #
james - Member

"Just throw it away "
Its not my bike to throw away, its my brothers, I don't think he wants to have to drop £1200ish on a new frame when he 'can' still ride this one. Plus you can't get a QUAD-link frame frame-only

"but you could ream the crown hole and go up a size on the new steerer"
As new, the part of the steerer tube that press fits into the crown is the same outer diameter as the part where the headset crown bearing race sits, (presumably 30mm as per that RST one, so that all crown races fit all forks), then tapering back to 1 1/8" for the rest of the fork? (the bend is above this transition point, probably about 40-50mm higher

Posted 2 years ago #
tinsy - Member

Yeah pretty much.. I am very bored.

Posted 2 years ago #
seth-enslow666 - Member

My mate fitted an alloy steerer to some single crwon Marzocchi shivers. The original was steel and way too short. He did the heating the crown up trick and then freezing the alloy steerer tube. Thus making a press fit. He even used a different steerer tube, think it was a Rockshox one he bought cheap. Bike has been running no problems, hes a fairly burly lad too. I doubt the crown strength will have been compromised. Just dont go too much with the heat on the crown, boiling water will be enough. Heating it a lot with a blow torch too much would compromise the crown strength though.

I would ride with that no problems.

Posted 2 years ago #
wwaswas - Member

which forced the headset to ovalise the headtube in the bike

Bike has been running no problems, hes a fairly burly lad too. I doubt the crown strength will have been compromised

talk to Marin about a crash replacement front end.

I can't belive people (particularly 'burly' people) treat their own safety with quite so much contempt...

Posted 2 years ago #
seth-enslow666 - Member

whats a Marin front end got to do with the price of fish?

Posted 2 years ago #
james - Member

The most annoying thing about the whole thing, is that had the bike not had a handbuilt front wheel and some poorly tensioned with some miles under its belt factory built front wheel, the front wheel would probably have pringled and left the frame and fork completely unaffected. Thanks merlin!

Posted 2 years ago #
wwaswas - Member

seth-enslow666 - he said it was a quad link frame - aren't they made by Marin?

Posted 2 years ago #
seth-enslow666 - Member

yes but I thought he said the headtube had gone oval after the crash? Why not just hit the headtube and make it round again. Stick a bit of round pipe in it for a guide and hit it until the headtube is round again, a bit like a blacksmith!

Posted 2 years ago #
seth-enslow666 - Member

Above comment was facetious and should not be takem literally!

Posted 2 years ago #
james - Member

Marin do make Quad-link bikes, but they're not the only one ..

Posted 2 years ago #
thebikechain - Member

I will sell you a new CSU at trade if it helps you NOT press in a new steerer.

Please don't mess about with stuff like this. An impact that has damaged your headtube and split a set of forks could easily happen again and you will not get lucky twice.

If you want some help then please drop me or Colin and email to mdownie@thebikechain.co.uk with the exact model and i will sort you a price.

_-_-Mods - please feel free to delete this if deemed inappropriate-_-_

Posted 2 years ago #
james - Member

Whats a CSU?
I'm not thinking of riding it (anymore), mostly interested in the detail

The fork hasn't split, just bent lots. The pic is after the steerer tube has been forced out of the crown

Posted 2 years ago #
thebikechain - Member

Steerer assembly. The upper legs basically.

Posted 2 years ago #
james - Member

Steerer, Crown + Stantions. Oh I see, CSU, stantions being uppers

Erm maybe yes, I don't need to get the fork off of my brother, just that if rideable would be better than the MX pro on my HT
Its just that the costs could be a bit preventative, though I'd be prepared to swap at home with the help of the rockshox manual
A complete 'CSU/SCU' assembly would put my mind at ease

Posted 2 years ago #
thebikechain - Member

Drop me an email on above address and i will find out the costs for you.

Posted 2 years ago #
james - Member

YGM

Posted 2 years ago #
thebikechain - Member

Ta - will get back to you soon.

Posted 2 years ago #
Wozza - Member

Mate, your brother is gonna die on those!

And that looks like a "soft" landing too!

Posted 2 years ago #
djcombes - Member

I'd be more worried about the frame and the headtube than the forks. Forks can definitely be fixed and the best way is with complete new upper section. Frame on the other hand sounds like it needs the attention of someone with experience of aluminium fabrication at the least (e.g. fix by welding and re-machining headset cups), and may be destined for the bin.

Posted 2 years ago #
BigJohn - Member

What's the worst that could happen?

Posted 2 years ago #

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