Sammyboy

I think I've bent the fork on my tandem. Was riding it home solo, dropped VERY slowly off a curb, same as I do every time on that route, but somehow screwed up, and the bars turned hard. Didn't fall, didn't drop the bike, just put my feet down, but when I got the bike upright again, the front wheel was rubbing the right hand side of the fender stays, and as I attempted to ride away, pulled hard to the left. It can now be observed pulling left even when pushed gently on a flat surface, but I can't visually see any damage - there's no cracking around the crown, or anything like that.

I assume I've put the (steel) fork out of alignment, but how can I check that, would it be sensible to try to bend it back, and how can I check for sure that it's straight? I'm a confident and capable bike mechanic, but frame alignment is rather out of my experience.

relyt

Frankly I think it is more likely you put the wheel out of alignment. They are easier to damage than forks. Going off curbs puts a lot of strain on hubs. Check the axle, QR, and wheel dish/true.

It is also possible the forks are bent without any noticeable damage at the crown. If it is steel, you might be able to bend them back. A bike shop has alignment tools and they should be able to put them on for free in a few minutes, to check the fork.

Sammyboy

Thanks - I'll pull the wheel off and stick it in my truing stand. It's running apparently straight, however, and I can't quite imagine how an out of true wheel would cause the bike to pull?

operator

A bike pulls to the left if the wheel is cocked in the axle dropouts or the fork is bent. It'd have to be out of true by a kilometer each way for it to even begin affecting the handling of the bike.

Sammyboy

In which case, it must be out by a kilometre, since it's pulling very significantly indeed. I have to put enough pressure on to keep in a straight line that I'd have a sore arm after 3 miles, and if I tried to ride with no hands, it'd turn through 90 degrees within a couple of metres.

waterrockets 

Have you tried it after re-seating the axle in the dropouts yet? It's possible that a side-load moved it when you went off the curb. You might also check that the rear wheel is seated...

Sammyboy

I haven't - I had to get straight home and go out. I'm not sure where it could move in the dropouts though, nor how that would cause pulling. I can see where it would cause the rubbing, but if the wheel is out of alignment.....? I'll absolutely check that though, because my favourite thing would be if this was no real problem.

waterrockets 

If the wheel(s) is(are) not seated, then the contact patch is not under the center-of-mass line for the bike, so it's essentially countersteering for you (full-time).

twobikes

One of my bikes was in an accident with a car while the previous owner had it. It always pulled to one side if the front wheel was fully seated in the fork dropout. I always had to get the wheel aligned straight and then tighten the axle nuts (no quick release when the bike was made). Finally, one day I planted a bead of weld material in the "high" dropout with an arc welder. It has been fine ever since. (For all of you worried about the temper of the steel having changed, it was so quick that the dropout did even not get hot.)

waterrockets 

It's older than 1927?

tellyho

+1 to the wheel alignment. I bet it just slipped in your dropouts.

twobikes

Quick release is probably like some features on automobiles. They are first available on the high end models. Later they become standard equipment on family sedans.

I guess they were available, but that bike came without them.

BikingGrad80

bent axle?

waterrockets 

Yeah, it was tongue in cheek I don't think I saw a bike with QR until the mid 80s, and it wasn't mine.

Road Fan

So, Sammy!

Try seating the wheel, and maybe tighten the QR knob jsut a bit more.

If that doesn't help, test teh frame alignment by putting a wheel from a biek you know rides well, preferebly a wheel you know is dished right.

If the tire tread is not then in line with teh head tube axis, looking down from teh front, teh fork is not holding the wheel in the right place and the fork is therefore bent.

You need to get it straightened so the front tire patch, the rear tire patch, and the central plane of the frame are all aligned. Then the bike will drive straight. Can't say if it's cracked.

Road Fan

dck

Your fork is bent.

Bikedued

Heck, Schwinn Continentals had QR axles at least by the early 70's, probably before,,,,BD