head/straight on crash damage checking

ben-----

Went smack bang into the back of a parked car yesterday evening Wet leaves. Miraculously, the bike, basically, seemed OK. Haven't looked at it properly at all yet, but rode the bike home without anything obviously wrong with it (me, bruised). What sort of checks should I do? The main impact was simply front wheel roughly straight/head on. I guess a kind of flattening of the wheel would be possible. Bending of fork / headset? What should be checked and how to check that kind of thing? Thanks.

imposter2.0

A lot will depend on impact speed, so what was it?

fat daddy

and what you hit.

a solid metal old landrover and your bike will go from 20 - 0 in a split .... but hit a nice modern car with its floppy plastic bumpers and as the bumber caves in and creases up, and the paint all deforms off of it, so the forces are spread from your steerer to the car you are in the midst's of destroying their bumper

so what was it ?

ben-----

> A lot will depend on impact speed, so what was it?

Not that fast. It was in a town, wet, and dark with traffic etc. round, dodgy road surface, so I certainly wasn't hammering it. I'd guess about 14mph, probably a bit less by the time I actually hit it; I think I managed to slow down a bit.

> and what you hit.
> so what was it ?

Can't remember exactly, but it was a modern small car with lots of plastic, its back.

fenix

Did you damage the car ?

ben-----

Fenix wrote:

Did you damage the car ?

Not obviously, visibly, no.

Monty Dog

Give your frame - around the headtube - and forks a very thorough visual inspection checking for thinks like cracked lacquer, paint, discolouring and delamination. Drop the forks and remove the headset bearings - do they drop in-out smoothly i.e. headtube not distorted. Likewise, is the wheel still true with no up-down movement. If there's no sign of visual damage, then it's unlikely that they'll suffer sudden catastrophic failure but worth asking your LBS for a second opinion if you're still worried but I doubt anyone will give you categoric assurances. I went OTB on my bike hitting a sandbar at the side of the road avoiding a car many years ago - despite thinking I'd broken the forks, I'm still riding it today many thousands of miles later.

craker

My bike wouldn't steer properly after a head-on. Took me a few rides to work out that the downtube had buckled and I was getting bad toe overlap.

Look for cracked paint around the steerer tube for a start.

ben-----

OK great, thanks for that both. There is no paint though on the frame, it's titanium. The forks are painted though. Still haven't got round to checking it yet.

pilot_pete

Might be worth sticking it in a turbo, putting the bars dead straight (assuming they weren't twisted in the crash) and look for wheel alignment front to back/ back to front. This could at least give an indication of something amiss such as a twisted frame (which might not be as obvious as a crack/ bend/ crease in a tube just by inspection).

I would have thought the biggest force from the impact would be transfered to your lower headset bearing via the wheel/ fork. I would inspect the wheel for 'roundness' and alignment by spinning it next to a reference point such as your front brake if you don't have a wheel truing stand. A flat spot would be obvious. If you can identify the point that hit (marks on tyre etc) that could help focus the spot to check closest. If the brake pulses then you might have flared the rim open at the point of impact. Might be obvious upon inspection. Doesn't sound like you were going fast enough or hitting anything sharp enough but worth checking.

Check all the spokes are still under similar tensions (without a guage just feel them to see if any are obviously looser than the others). Obvious hub bearing damage would be rough or notchy spinning of the wheel, but this is unlikely as bearings are designed to take the shocks in that direction.

Do that before removing the wheel from the forks. Check headset for play as described by others above. Check for freedom of movement from lock to lock with the steering (assuming the bearings were in good condition and there was no play before the accident). There should be no 'tightness' or rough spots as the steering is moved. Equally no slackness or looseness.

Next check that the quick release has held firm and the wheel has not moved in the fork dropouts. Remove the wheel and inspect the dropouts for damage. Check any joint between dropout and fork (especially if they are alloy dropouts bonded into a carbon fork). Once again, paint cracks can be a sign.

Romove forks from the frame and depending on bearing type remove bearings from frame (some press fit bearings should not be put back in if removed due to possible damage whilst being knocked out, so either inspect as well as you can with the bearings still in or get some new bearings to fit if all is ok.)

Now inspect the headtube closely and the bearing seating areas, especially the lower one. Inspect the fork closely especially around the crown race at the bottom of the steerer tube. Check for obvious damage such as cracks, scores, marks etc (especially carbon steerers) or any other damage such as bends, dings, gouges etc on an alloy steerer.

If you have an alloy steerer it is possible that it could be bent slightly. You might be able to see it with the naked eye. This would probably show up as tightness at certain points during the steering movements but I suppose the best check would be to measure the wheel base and compare it to the geometry table for your frame/ fork or stick the frame and forks on a jig, but you are getting into the realms of sending it back to the manufacturer there I suspect.

Feel the bearings for roughness or tight spots when they are spun and if they are external check the cups for damage.

If you have done all that and nothing appears amiss I suspect that is as good as you can do. Maybe use a magnifying glass for close up inspection of the critical areas. Other than that I can't think of much else you could do.

Good luck.

PP

Monty Dog

Titanium is surprisingly resilient - the fact that my roofrack-mounted titanium bike survived passing under a steel, carpark height restriction, but did manage to rip the roofrail off and twist the roofbars on my car. Apart from a few paint scuffs from the carpark metalwork, bike was fine. Not allowed a roofrack anymore...

Checking for a consistent gap between the lower headtube and fork as you turn them is a good place to start as that's the point of maximum loading.

ben-----

Excellent, thanks for the info. Will go through doing most of that I think, not going to have a chance to do it for another day or two now though. I think the main possible problem is around the headset, the bottom of as you mention PP. Thanks.

The Rookie

What forks? A bent steerer is less obvious but the most common issue with alloy steerer (especially on carbon lower) forks as noted by PP.

ben-----

The Rookie wrote:

What forks? A bent steerer is less obvious but the most common issue with alloy steerer (especially on carbon lower) forks as noted by PP.

Yup, that's what I've been thinking: the forks, the top steerer part, have got to be the most likely bit to damaged.
I bought the bike 2nd hand a while ago, according to its listing about the forks:
Genesis carbon blades/alloy steerer with mudguard mounts, suitable for deep drop calliper brakes

the_cyclist_of_catan

Monty Dog wrote:

Titanium is surprisingly resilient - the fact that my roofrack-mounted titanium bike survived passing under a steel, carpark height restriction, but did manage to rip the roofrail off and twist the roofbars on my car.

I had to check that this was your post and not mine! Roof rack destroyed, roof twisted, but Ti frame fine.

I did destroy both wheels though - and there are a few worrying cracks around the Al steerer tube. Two years on and I still haven't replaced the forks - hope I don't regret that decision!