auchencrow

About 6 weeks ago I was riding my ’86 Trek 310 ,



and got hit by a car at about 40-50 MPH, as it crossed into my lane coming around a curve. – (It was sort of a side swipe really, but the car still had to be towed because I blew out the left front tire, tore the outside mirror off and pushed the fender back into the driver’s door jamming it shut). My bike fared pretty well – the front wheel zipped by the car without ever making contact, and the only apparent damage to the bike was a twisted handle bar, and a pedal that was torn out of the left crank. . . Or so I thought . . .

After the accident, I brought the bike to my LBS for an estimate. The mechanic verified that the frame was not bent using the frame gage, and since the Insurance was paying, I decided to have them effect the repairs, and do a general tune up.

When I got the bike back, it looked good as new, but when I got to riding it, I found that the bike mysteriously pulled to the right.

I went to the bike forums immediately for an answer, and found a thread that described a case where a pair of fork blades had not been bent back, but had been displaced laterally about ½ inch, causing the bike to pull right.
https://www.bikeforums.net/bicycle-mechanics/79546-straightening-bent-fork-blades.html

I went into the garage and using a bicycle plumb bob (made from string and a broken presta valve) I saw that my bike ALSO had both fork blades laterally displaced ½” to the left.

I then made a crude alignment gage from a 2 by 6 and two U-bolts, establishing a centerline with a known, good fork, and my laser level.
Next, I gradually bent each of the forks to perfectly align +/- 50 MM to centerline, using a small square, and a section of PVC pipe, (See pics)










I reassembled the bike and tested it. No improvement!
NEXT -
I verified that the front and rear wheels where true and centered between the stays.
I verified that the front and rear axles were seated in the dropouts, and the QR’s secured.
I verified that the headset bearing cages were lubed, and not installed upside down.
I replaced the old caged bearings with 2 new bearing cages ( I am all out of loose ball bearings)
I verified that the headset was properly adjusted, without excess play or binding.
I added an additional spacer in the head set, just to be sure the headset nut was not bearing down on the threaded tube.

STILL no improvement! The bike pulls right.

I don’t know what else to do. Is there something I am over looking? Any suggestions are appreciated.

Al1943

I don't understand how a bike shop would not find the bent fork. From the pictures the fork is severly bent and probably not repairable. Now I'm wondering if the frame is bent. Instead of working on it yourself you need to get another bike shop to check it out and file a claim with the insurance company.

Al

Mos6502

If the steerer tube is bent, even slightly, the bike can pull strongly. If the fork blades were bent, then it could be the tube is also bent.

auchencrow

Hi Al1943 -
The fork was bent almost exactly 1/2", which sure is a lot - but surprisingly on the built up bike, it was really hard to see - not obvious at all as it is when a fork is pushed rearward. - (in fact without the aid of a plumb bob, I doubt that you would not ever notice. So in defense of my local bike shop, I can see why they missed it. In any case, both the forks arms are now perfectly aligned (at least as well as my known good fork, taken from a Miyata 710).

BTW I too suspected the frame but had it measured at the LBS, before committing to repairing it in the 1st place. I did collect $200 from the drivers' Insurance company, but basically that just covered what we knew about, not this latent problem.

illwafer

first of all, congrats on surviving the crash and being victorious over the car.

secondly, you appear to be a better mechanic than most LBSes (which you probably confirmed for yourself).

lastly, have someone else ride your bike and see if they get the same pull. maybe they can help see what the issue might be. it could be that your bike always pulled left and now it's fixed! or, maybe you suffered a slight injury you aren't really aware of...

auchencrow

Hi Mos6502 -

I can guarantee that the forks are aligned +/- 50mm to the steerer tube's nominal centerline, but if the steerer tube is bent slightly, I coudl overlook it. - How could I measure it? - And by bent, do you mean curved along the length? or abrubtly bent where it joins the fork crown?

Do you suppose spacing the axle downward in one of the 2 fork dropouts would test for this condition? - Or maybe I should swap the threaded fork assembly with another bike to test it ? - I have a Bianchi that is about the same size - not at all sure it would fit though .

auchencrow

Thanks illwafer! - but it's always a Pyrrhic victory when you win an argument with a car, so DON"T go trying that yourself!

illwafer - I'd liketo subscribe to that theory, except I have a bunch of other road bikes in my garage that DON'T do it, even when I ride them hard with no hands.

Al1943

I would not be at all surprised if the steer tube and head tube are bent.

Nice job with the photos.

Al

auchencrow

- Do you know a way to measure it? ?
If not I'll try the fork from my Bianchi. (It would look kind of goofy but I would be ecstatic just to get to root cause - I'll know how to fix it then).

Thanks Al1943 !

BCRider

Since the shop missed the forks being offset it would not surprise me if their checking of the frame is highly suspect as well.

You did an excellent job of making up a jig for measuring and straightening the forks. This displays that you have a pretty good handle on the basics and how to set up and measure angles and extend lines via squares and plumb lines to check this stuff. I'd go ahead and do the same sort of treatment on your frame looking for a possible twist in the main triangle or a similar offset in the rear stays.

Mos6502

I was going to say that if the crown top is flat just use a straight edge along the tube to find out. Obviously that's not going to work here. I guess you could hang a plumb from a bolt in the brake hole, then level the crown out upside down and see if the tube centers on the plumb.

It's probably be easier to just go with a new fork.

Road Fan

I think there are several more possible issues. To run straight, the bike needs to have the wheels both in the same plane, and the main triangle and the center of gravity in that plane. The BB axis needs to be parallel to both of the wheel axles. Some alignment issues could be a subtle result of the crash, the result of your years of use, or have been latent in the frame from the factory. Trek did not always align everything perfectly back in the day.

1. The seat tube might not be straight, or perpendicular to the BB axis. The best way to see this is on an alignment table, but if you can see with a straightedge that the seat tube is warped, this problem exists.

2. The head tube might be twisted out of plane with the seat tube or the BB axis. You may be able to see this if you can sight the head and seat tubes from the front or rear. It might be important to strip the bike to some degree to be able to see better.

3. There could be a distortion in the rear triangles that has the rear wheel laterally out of plane with the main triangle.

4. A rear triangle distortion could cause the rear wheel to lie in a plane that is twisted with respect to the BB axis. My Trek 610 had this problem, and my aligner milled inside the dropouts to ensure the rear axle would lie parallel to the BB axis.

It could also be that your fork is still not right, despite your careful approach.

The most effective way to resolve all of this at once is to have the entire frame aligned at once. I had it done by a nearly local expert framebuilder, Ron Boi in Kenilworth, Illinois. His prices are on his website, https://rrbcyclesusa.com/. Framebuilders have to align hand-made frames before delivery, so they know the methods in a way your LBS might not. Besides, I think an alignment table is necessary to see some of the problems and know when the frame is right.

I had my Trek 610 aligned by Ron and may send him some other frames. I also had my Masi aligned, and have been amazed by how much improvement both bikes showed.

auchencrow

Thanks Mos6502 -That sounds like a good method -I'll try it

I don't want to go there, unless (a) I first verify the steer tube is bent and (b) find a suitable replacement Chromalloy 27" fork with the proper tube length, CHEAP.

auchencrow

Thanks for your vote of confidence in me, but I'd venture the experienced bike mechanic at the LBS still has the edge on me, and I'm pretty certain what he told me about the frame is accurate. But if my fork swapping experiment does not pan out, I may probe the frame thing deeper as you say.

sedges

It seems that you may be able to make use of a rotary laser level to do some of the measurements you need, especially if you wish to check the frame. Just a thought. You would need a good one to be accurate. The cheap ones are only good to 1/4 inch over 20 feet- not so good.

auchencrow

Hi Road fan -
and thank you for your rather comprehensive post: I am going to try to rule out the fork steerer tube before proceeding with a deep dive into frame alignment (beyond what the LBS did) - but I think your little treatise gives me an undertanding at least, of what I'm looking for.

Not sure I'm ready to take the TREK out to to Kenilworth Il just yet - but I think I will give them a call to ask about the frame alignment option, if it comes down to it... I don't have a lot of money to spend, but this was a really good bike, and I feel like I "owe" it something, because I was not killed or permanently injured on it. (I know it's silly of me to personalize a bicycle. but I'm probably not alone in doing that).

auchencrow

Great minds think alike!

DannoXYZ 

From your post and pictures, I'm pretty sure your fork is fairly straight now. Here's a Park Tool - Frame Alignment Gauge that I suspected the shop used on your bike. While it tests to see whether the dropouts are in-plane with the seat-tube, it does nothing to test the alignment of the head-tube with the seat-tube.

In a lot of non-head-on crashes, especially those that result in the fork being bent sideways, the headtube ends up twisted as well. While its center may still be in-plane with the seat-tube, the top and bottom are twisted to opposite sides. That is, the seat-tube and headtube are no longer parallel laterally. What this does is put the front contact-patch of a straight fork off to the side. One way to fix this is to actually bend the fork in the opposite direction by 1/2".

auchencrow

Well, I tried to substitute the fork from my Bianchi, but found that the fork bearing races were incompatible with my Trek's head tube bearing races.

I did check out the alignment of the steerer tube on my Treks' fork though, and with the laser and my rigged up fork alignment fixture (see pic), I confirmed that the tube is aligned within about 1/16" of the centerline running between the two forks.
(I feel confident that the fork is not reason why the bike pulls right.)


I also did my best see if the frame was bent. The best method I came up with was simply laying an aluminum channel flat against the frame's triangle, and measuring the distance to rear drop outs on one side, and then the other. (see pic) There was less than 1/8" disparity from right to left.



I think though, I just succeeded in verifying what the LBS had measured (probably with the very Park gage cited by DannoXYZ. . . )

Based on what I’ve eliminated thus far, I think both Roadfan and DannoXYZ may be on to something: i.e., The head tube and seat tube might not be in the same vertical plane. - I suppose it wouldn’t take much twist, projected out to where the rubber meets the road to cause big problems, but it's hard to fix what you can't see. (Maybe if I get a long 1" bar to insert through the head tube, I would be able to see it better?)

Bending the forks another 1/2 inch in the opposite direction to compensate might help some, but I do have to say that bending the first 1/2 inch back to centerline did not ameliorate the pulling condition much if at all.

I tried to call Road Fan's frame builder today to diiscuss it, but I got no answer at the phone listed on the website. - But the problem does seem to beg an expert with the right equipment: It's getting a little bit beyond me.

Thanks everyone for your insights.

Homebrew01

Looks like he's doing a fine job on his own.

I wonder if you could fix the frame with level on the seat tube, then set the level on the head tube to compare. If the 2 fixed cups in the head tube are the same diameter, then you can set the level on them. You may not be able to notice a small problem, but a glaring one may show up.

cyclist2000

Have you checked to see if one of the fork blades hasn't been bent back. place a hub in the forks and use your laser to look at the fork from the side. aim the laser straight down the axle of the hub and see if the fork crown is in alignment.

Al1943

True, my concern is that the insurance company would not pay off after the owner had worked on the bike, but would more likely take the word of an uninterested third party bike shop.
I agree that the OP is doing a very fine job of analyzing the problems.

auchencrow

Yup- I've checked it a few ways, and both blades are absolutely aligned in the F/A direction relative to the fork crown.

cyclist2000

Well, I say notify the insurance company that there is additional damage that was not visible during the initial inspection and that you are due a equivalent functional replacement. Do it quickly or it will be too late. I would be flustered after all this effort and would want to just end the whole thing. But this may be a fun challenge for yourself and better than getting a new frame.

DannoXYZ 

Your photo of the fork and laser-beam seems to show that the fork-blades are bent off to one side... Was this picture taken before or after you bent it back? Or it could just be parallax error due to the camera being off to one side.

Yes, you've done the same test as the bike-shop with your gauge. What we need to do is compare alignment on three points. The front dropouts to the bottom-bracket shell to the rear-dropouts. We've confirmed somewhat that the rear dropouts are close to aligned to the same plane as the BB, now we just need to do the front.

1. re-install the fork on the bike, adjust the bearings for smooth rotation with no play

2. make an alignment table from a flat board about 5-ft long, draw a straight line down the exact centre.

3. one one end, attach a tall V-block about 70mm high to hold a spare rear-axle. Screw some nuts/cones onto the axle to position the axle centered on the board (130 or 135mm apart depending upon your frame's OLD).

4. around where the BB-shell lays, screw down some right-angle brackets facing each other 68mm apart. The BB-shell should fall right between the brackets if the rear-dropouts are aligned.

5. the fork will be free, you can make another V-block with axle to ensure it's rotated 90-degrees to centreline. Then measure on this axle where each fork-tip lands.