Questions about frame alignment

[rkelsen]

OK, so a few months back I purchased a frame (from the 'bays), and it seemed like I had been lucky with my purchase.

I posted about it here.

Now, I have some questions about frame alignment:

1. The rear wheel doesn't sit straight in the frame. It's a straight wheel, and this was verified by installing it both ways. When the wheel is centred between the chain stays, it is off centre between the seat stays. It is a few mm to one side. The relationship of the tyre and the mounting hole in the brake bridge makes it obvious, but I have verified it with a ruler too. It is as if one dropout is sitting slightly higher than the other...

2. The forks seem twisted. Looking down the fork (as if riding the bike), it looks like the centre line of the crown isn't parallel with the axle line. This was also verified with a straight wheel and a ruler.

I've measured the frame using the ol' string around the headtube trick as described by Sheldon Brown, and these measurements are fine.

What can I do with this frame? Can it be rescued?

[WyvernRH]

OK, so a few months back I purchased a frame (from the 'bays), and it seemed like I had been lucky with my purchase.

I posted about it here.

Now, I have some questions about frame alignment:

1. The rear wheel doesn't sit straight in the frame. It's a straight wheel, and this was verified by installing it both ways. When the wheel is centred between the chain stays, it is off centre between the seat stays. It is a few mm to one side. The relationship of the tyre and the mounting hole in the brake bridge makes it obvious, but I have verified it with a ruler too. It is as if one dropout is sitting slightly higher than the other...

2. The forks seem twisted. Looking down the fork (as if riding the bike), it looks like the centre line of the crown isn't parallel with the axle line. This was also verified with a straight wheel and a ruler.

I've measured the frame using the ol' string around the headtube trick as described by Sheldon Brown, and these measurements are fine.

What can I do with this frame? Can it be rescued?

Couple of suggestions:
For the rear wheel,
(1) Check for a bent axle, especially if the hub takes a spin-on freewheel.
(2) It sort of sounds as though the wheel might be incorrectly dished for the dropout width?
(3) Is the wheel vertically parallel aligned to the seat tube or at angle (look along the wheel from the rear so front and back align, you should see the same amount of seat tube all the way up and down.
(4)If the wheel is vertically aligned, is it offset so you see more seat tube one side than the other?

If 3 & 4 are true then 2 sounds likely. You may be able to fix it by spacing the axle. The Bent axle is another thing, it will give a varying result depending on the way you bolt the axle into the frame.

For the front, this may not be a problem as long as the wheel runs true in the centre of the fork and the wheel aligns with the centre of the down tube. The builder may just have not been very good at aligning the fork ends and the crown and they cold aligned everything later. More common than you might think...

Cheers
Richard

[Uncle Grumpy]

1. The rear wheel doesn't sit straight in the frame. It's a straight wheel, and this was verified by installing it both ways. When the wheel is centred between the chain stays, it is off centre between the seat stays. It is a few mm to one side. The relationship of the tyre and the mounting hole in the brake bridge makes it obvious, but I have verified it with a ruler too. It is as if one dropout is sitting slightly higher than the other...

If you've measured from rear drop to rear drop via the headtube and it's aligned, then I dunno. You could sit the rear triangle of the frame on a sheet of butchers paper and do some geometry. If it is out, then a bit of realignment is nothing to fear.

Sheldon has some stuff about using planks of wood and stuff, you may have seen it when doing your search for alignment checks.

I have a mid 80s De Rosa that should have been 126mm spacing, but turned out to be 110mm. As it turned out, one side was bent across. I was able to cold set the frame back to where it should have been and also get it spaced to 130mm to take a 9 speed drivetrain. It's a bit of trial, error, checking etc, but a bit of patience and you can get it right.

Only caveat to this is you say the stringline check showed it as okay, which baffles me. The dropouts shouldn't be at different heights unless one seatstay is shorter than the other. Put a steel rule through the dropouts and sit a spirit level on it. With the bike sitting on the BB and headtube with the chainstays off the ground, you'll see if the dropouts are level.

2. The forks seem twisted. Looking down the fork (as if riding the bike), it looks like the centre line of the crown isn't parallel with the axle line. This was also verified with a straight wheel and a ruler.

May have been damaged at some point, I'd get a new fork. Have you stripped the paint off it? I'd be doing that and checking it over for wrinkles, the whole bike that is. C'mon, you know you want to refinish it!

{quote="rkelsen"]What can I do with this frame? Can it be rescued?[/quote]

I'd say yes, subject to knowing the extent and cause of any misalignment of the frame and doing a replacement of the fork. Whether that's worth it is up to you, but yeah, worth a shot. If all else fails then it's a lake jumper.

Grumps

[rkelsen]

Thanks guys.

I've thought about this some more, and read more about frame alignment on the internet.

When I next get the chance, I'm going to get creative with some string and the "special tools in leather cases" that Dave Moulton says I'm equipped to use.

The first thing I think I need to do is figure out what is bent... and that's where the string comes in. If I tie a string to the centre of an old axle installed into the dropouts, and run it up to the seatpost bolt, I'm guessing that it should cross the centre line of the hole in the brake bridge yeah?

C'mon, you know you want to refinish it!

You bet! But I won't be doing this one myself. Once I figure out what's wrong and fix it, I'll be passing the frame to Damhooligan for professional repainting. My current commuting bike was rattle-canned about 4 months ago. Even after using 2 cans (at $20 a can for what I thought was good quality), the paint is paper thin. After only about 1,000km, I've got lots of little chips and scratches in it. The paint in rattle cans must be really poor quality.

For the front, this may not be a problem as long as the wheel runs true in the centre of the fork and the wheel aligns with the centre of the down tube. The builder may just have not been very good at aligning the fork ends and the crown and they cold aligned everything later. More common than you might think...

In the past few days I've read quite a few anecdotes along those lines...

If I clamp the fork upside down in a bench vise (between two pieces of offcut floorboard), and place a long screwdriver in the dropouts as a lever, will it respond to being twisted back? Everything I've read seems to indicate that this is not a problem, because the metal isn't bending far enough to do any damage. There is no visible indication that the fork was in a crash. It is still in original paint, and there are no chips, cracks or ripples in the metal anywhere.

[Uncle Grumpy]

The first thing I think I need to do is figure out what is bent... and that's where the string comes in. If I tie a string to the centre of an old axle installed into the dropouts, and run it up to the seatpost bolt, I'm guessing that it should cross the centre line of the hole in the brake bridge yeah?

That would give you an indication, pretty much the same thing I was getting at with the butchers' paper, but lot's simpler.

As a first step, measure the dropouts to see if they're 126mm (which that frame should be because I assume it's pre 9 speed).

Your method for dealing with the forks is fine, so long as you don't go overboard of course.

Grumps

[il padrone]

As a first step, measure the dropouts to see if they're 126mm (which that frame should be because I assume it's pre 9 speed).

~1979 Raleigh frame will be pre 7-speed. Frames of this era would still have generally had 120mm spacing at the rear.

[WyvernRH]

Thanks guys.

If I clamp the fork upside down in a bench vise (between two pieces of offcut floorboard), and place a long screwdriver in the dropouts as a lever, will it respond to being twisted back? Everything I've read seems to indicate that this is not a problem, because the metal isn't bending far enough to do any damage. There is no visible indication that the fork was in a crash. It is still in original paint, and there are no chips, cracks or ripples in the metal anywhere.

You realise if the front wheel is running true to the frame now if you 'straighten' the forks so the axle and crown are parallel the wheel may no longer be running true to the frame? The screwdriver idea will work but I think Uncle Grumpy has the right idea, just get another set.

Have you checked if the rear wheel vertically aligned with frame? If it is aligned but still offset and it fits without 'springing' open the stays I still reckon the dish on the rear wheel is out of whack.

If you are really worried take it to your LBS or frame builder for a check on a machinist's table.

Cheers
Richard

[rkelsen]

You realise if the front wheel is running true to the frame now if you 'straighten' the forks so the axle and crown are parallel the wheel may no longer be running true to the frame?

The wheel doesn't run straight in the forks. And looking down the fork, one dropout is visibly ahead of the other. A trick I found on the internet said to use an old axle cut in half as a means of determining how far out of alignment the fork is. This is one of those ingenious solutions that I wish I'd thought of myself...

Have you checked if the rear wheel vertically aligned with frame? If it is aligned but still offset and it fits without 'springing' open the stays I still reckon the dish on the rear wheel is out of whack.

The wheels I'm using to check it are from my daily runner. These wheels have done over 5,000km since last being trued, but when installed in the aforementioned daily runner, seem to run fairly straight. They're not perfect, but not out of true or dish significantly enough to be noticed in that frame.

If you are really worried take it to your LBS or frame builder for a check on a machinist's table.

I'm not worried at all. I'm treating this as a great learning experience.

[rkelsen]

So it looks like the dream is over for this frame.

Looking along the seat stays from the dropouts (with one eye), it is obvious that there is a kink in the LH stay, and that there are some small ripples in the metal near the brake bridge, which explains why the wheel wasn't sitting straight.

I might try to fix it one day if I get bored... but I'll be shelving it for the short term.

[drubie]

I might try to fix it one day if I get bored... but I'll be shelving it for the short term.

Damn shame. It's a pity that the better quality the frame, the easier they are to damage - some POS hi-ten thing will go unscathed through a garbage crusher, but the cat jumping in your garage will knock a dent into your 531 top tube.