head/straight on crash damage checking

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

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.

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