Dear All,

I just started building up a new LHT frame and have come across a few 'interesting' problems!

I hoped that I would get away with installing a cartridge BB (UN55) without chasing/facing which turns out not to be the case!

In fact, it is clear to the eye that the axis of rotation is not perpendicular to the seat tube, causing a very noticable wobble of the chainwheel. The latter is new and definitely straight by the way. I guess the answer to this is a visit to the LBS for a chase/face ?

While I am fairly comfortable with that idea, I also ran into problems with the rear dropouts. I have XT hubs and found that the hub binds extremely strongly on one side. In fact it required a large degree of force to remove the wheel from the slot! This does not look like a problem caused by an excess of paint for example, instead the dropout slot really is noticably narrower on that side.

I am suspicious of two fairly major misalingments on one frame. What is the percieved opinion on how to proceed? Send it back? A trip to the LBS? Give it a bash with the hammer?


cheers,

Jim

I'd say send it back to Surly. They aren't supposed to ship frames like that. Facing won't help if the axis of the crank hanger is tilted.

+1 If it is truly mis-aligned, send it back. My Cross Check had no assembly problems except overspray paint in most of the threads and you are entitled to the same quality.

Not what I want to hear but what I suspected...Also not fun when you are supposed to going on a bike tour next week!

the chainring wobble is the crank/spider. remount it in one of the 4 possible rotations for the best run out.

Send it back. State your reasons plainly and give Surly a chance
to send you a good one. If they fail to do so again, look elsewhere.

this is how I would proceed.

I don't understand how a misalignment of the BB shell would cause wobble?

Wouldn't the chainwheels just rotate in a flat plane that is not parallel to
your frame's axis of travel ?

Facing BB and chasing threads should really only be done once, after frame-build and before painting. The threads are usually masked off for painting and the uniform layer of paint on the face doesn't cause any problems.

If the BB-axle is not parallel to BB-shell, this causes a permanent tilt of the axle. ALL of the chainrings will spin in a plane away from perpendicular, but they will not wobble. Wobbling is caused by:

1. loose BB bearings
2. loose crankarm
3. loose chainrings
4. non-flat, out-of-true chainrings.

This is an easy fix for any competent shop. And the rear-dropout slot was bent inwards from the frame being dropped at some point. Again, very common problem and very easy fix for a decent mechanic. Then again, if the assembly mechanic was any good, both of these issues would never have gotten out of the shop in the 1st place.

The BB problem is weird though, the body and the metal cup went in really smoothly. Is it possible that the torque is too low on the cup? I have plently of experience of installing the shimano un54 model with a plastic cup, maybe the UN55 needs a little more oomph to get everything seated properly?

You are right of course- doh!

Jim246, There's no reason that the LBS can't sort this new frame out, either by repair or replacement. Your crankset is suspicious, to me anyway. If you bought it from the LBS they would help there also.

Brad

Check for lateral looseness. Place right crankarm backwards, parallel to chainstay. With one hand on chainstay, use other hand to hold crankarm at end, near pedal-hole and push in and out. Do you feel looseness and movement back & forth with a sudden stop at the end? If so, bearings in BB are loose or crankarm-bolt is way loose and you've got buggered crankarm now.

If not, look vertically downwards over the front-derailleur. Use one of the derailleur cage-plates as guide and spin crank backwards Does the chainring without chain look like it's wobbling in & out? Chainring's not flat. Shift chain to other chainring and inspect as well.