Building up a rear dropout with J-B Weld

[fa63]

I have a bike where the rear wheel doesn't sit quite flush in between the chain stays; it is a little over 1 mm closer to the non-drive side than the drive side. Same result with multiple wheelsets, so it is not a wheel issue.

I was playing around earlier today, and putting three layers of a coke can bottom in the dropout (I cut them to fit in the dropout) essentially brought the wheel back in center. That is about 0.3 mm. I was thinking if it would be possible to build up that dropout by the same amount using J-B Weld's SteelStick for a more permanent solution. I suppose I could also file down the opposing dropout but for some reason, I am leaning more towards building up than filing down. The dropouts are steel.

Any thoughts?

[dddd]

The normal fix for any problematic wheel centering issue would be to slightly cold-set the rear triangle(s) to wherever one wants the dropouts to sit.

And, unless the frame were extraordinarily poorly fabricated, no signs of trauma to (for examples) the seatstay caps or paintwork would be likely from such cold-work.

Using anything bonded-on is imo an invitation to the structural adhesive possibly crumbling under the loading of the QR skewer, with resultant possible loss of tension while riding.
I've used J-B Weld for other things like fixing holes in carburetor float bowls or securing Trek BB90 bottom bracket bearings, with great results, but I wouldn't use it on the face of a dropout.

Note that with steel frames, the first millimeter or so of cold-setting tends to occur at much lower force levels, so this one sounds like a relatively easy correction to make.

And, for the same reason, a mere .3mm of centering error could literally be the result of some degree of stress-relieving of the frame during it's first hard ride!

[zmudshark]

You need to use one of these:

https://www.parktool.com/product/frame-alignment-gauge-fag-2

[bshell]

fa63 -
You won't hurt anything or risk safety. Give it a try(+report back)!

I had the same problem with one of my cu$tom bikes. Drop outs were aligned properly, seat stays were aligned properly, etc. and I narrowed it down to the front/rear faces of the vertical dropout. I found this while trying to use wider than normal tires. I would get tire rub on the drive side chain stay under heavy torque but there was twice the space between tire and CS on the non drive side.

Fortunately, I live near several frame builders and paid one of them to tig weld a *tiny bead of material on the inboard half of the vertical drop out. I wanted to pull the wheel to the left so the bead went on the forward face of the NDS drop out.

*tiny (2-3mm wide) because the axle only goes @half way through. Also, keep whatever material you use out of the top arch of the DO or you'll introduce a new misalignment. If you overfill slightly (thickness) you can use a file to really fine tune the adjustment/fit. Go slowly, it doesn't take much.

Good luck!

[David Kirk]

Slowly carefully, and methodically file the other side. File, check, file, recheck....etc...until you get where you need to be.

The JB weld will not last in this situation and the axle needs to sit metal-to-metal in the drop.

dave

[dddd]

I see now that the OP was not wanting to add JB weld to the face of the dropout, but within the slot.

I would (as zmudshark recommended) first make sure that the dropouts are centered, which would determine if any filing of the dropouts should be done after a centering cold-set procedure might be done and whether any such final filing would then best tilt the rim to be better centered within the seatstays or chainstays.

It's kind of like with front forks where one might be trying to correct a steering pull while hopefully centering the tire between the fork legs at the same time, i.e. one first needs to determine how best to go about getting the tire contact patch on center with the frame while also centering the tire between the fork legs.

Remember, any metal filed away cannot easily be put back!

[fa63]

Slowly carefully, and methodically file the other side. File, check, file, recheck....etc...until you get where you need to be.

The JB weld will not last in this situation and the axle needs to sit metal-to-metal in the drop.

daveThanks, Dave. I was hoping you would chime in :-) I might take a file to it, or just leave it alone (or leave my ghetto spacers in). It is really something that I only notice from time to time; it is off by just a little and doesn't seem to affect handling of the bike at all.

[ultraman6970]

If the frame is straight (I would recheck that a lot 1st)... file is your friend, .3mm is super little, I would try sand paper instead of a file, harder to mess up.

The difference is so little that makes me wonder if the issue is paint that went away from 1 drop out, and the other one still has paint.

[fa63]

If the frame is straight (I would recheck that a lot 1st)... file is your friend, .3mm is super little, I would try sand paper instead of a file, harder to mess up.

The difference is so little that makes me wonder if the issue is paint that went away from 1 drop out, and the other one still has paint.No paint in either dropout; that was the first thing I checked and I took a sandpaper to whatever was left on them.

[oldpotatoe]

Slowly carefully, and methodically file the other side. File, check, file, recheck....etc...until you get where you need to be.

The JB weld will not last in this situation and the axle needs to sit metal-to-metal in the drop.

dave

What he said..if the rear triangle just isn't straight, maybe cold setting would fix the issue BUT if the chainstays are different lengths(ooops)..then cold setting won't work but a file does work, done it with rear dropouts and fork ends.

[Brian Smith]

I have a bike where the rear wheel doesn't sit quite flush in between the chain stays; it is a little over 1 mm closer to the non-drive side than the drive side. Same result with multiple wheelsets, so it is not a wheel issue.

I was playing around earlier today, and putting three layers of a coke can bottom in the dropout (I cut them to fit in the dropout) essentially brought the wheel back in center. That is about 0.3 mm. I was thinking if it would be possible to build up that dropout by the same amount using J-B Weld's SteelStick for a more permanent solution. I suppose I could also file down the opposing dropout but for some reason, I am leaning more towards building up than filing down. The dropouts are steel.

Any thoughts?

Is this a road bike, maybe with minimal clearance for the tire(s) you intend to use? I could see having less than 3mm of tire clearance and 1mm of left/right disparity being an issue worth considering remedy. If, on the other hand, this was a mountain bike with gobs of clearance but something that just conceptually bothers you once identified, best to leave it as it presently sits.

[bshell]

Dave Kirk, plus anyone else-

I think axle ends are standard at 10mm diameter. Is there a standard width for vertical dropouts?

I ask because I'm wondering if there's any risk to creating 'slop' in the dropout with the filing method alone?

Does a QR have enough clamping force and bite to prevent axle movement within an oversized dropout once pedaling torque comes into the picture?

I like to learn. Thanks!

[David Kirk]

Dave Kirk, plus anyone else-

I think axle ends are standard at 10mm diameter. Is there a standard width for vertical dropouts?

I ask because I'm wondering if there's any risk to creating 'slop' in the dropout with the filing method alone?

Does a QR have enough clamping force and bite to prevent axle movement within an oversized dropout once pedaling torque comes into the picture?

I like to learn. Thanks!

Good question.

There isn't a standard width of dropout slots - shocking isn't it? Roughly speaking the slots are about 10.3 mm wide but there's not industry standard.

The trick to properly filing a dropout slot is to only file a slot up and/or forward - never to the rear. The allows the wheel to be pushed up and forward before you clamp the QR skewer so that you are 100% sure it won't move under pedaling pressure.

dave

[fa63]

It is a road bike; clearance to the chainstays is about 3 mm on one side and 4 mm on the other. There are no signs of chainstay rub or anything, so it is really something that bothers me on an aesthetic level.

Is this a road bike, maybe with minimal clearance for the tire(s) you intend to use? I could see having less than 3mm of tire clearance and 1mm of left/right disparity being an issue worth considering remedy. If, on the other hand, this was a mountain bike with gobs of clearance but something that just conceptually bothers you once identified, best to leave it as it presently sits.

[Brian Smith]

It is a road bike; clearance to the chainstays is about 3 mm on one side and 4 mm on the other. There are no signs of chainstay rub or anything, so it is really something that bothers me on an aesthetic level.

1mm on 4, and even worse, 1mm on 3 are proportions that would bother me as well. Perhaps shooting to correct 1/2 of that is a good aim. That's what I would probably do anyway, absent a complete understanding of the bike's alignment condition. It's laborious for a builder to assess aspects of alignment such as the coplanarity of the wheels, but it's important that an owner not consider the position of a tire between the stays as more important than the coplanarity. Adjusting the "dish" of the wheel 1/4mm might also be an appropriate improvement.

[slambers3]

Before you start filing the frame...are you absolutely certain all of the wheels you've tried on this one are dished evenly?

[fa63]

I would say yes. Two were built by my friend who has been building wheels for 20 years, and currently I am running Campy Zonda wheels which are very well built in my experience.

Before you start filing the frame...are you absolutely certain all of the wheels you've tried on this one are dished evenly?

[Tandem Rider]

I would say yes. Two were built by my friend who has been building wheels for 20 years, and currently I am running Campy Zonda wheels which are very well built in my experience.

I would put the wheel in reversed (cassette on the left) as well, just for a sanity check for consistency. Also check for a slightly bent axle. Then I would check or have checked the rear triangle alignment. Assuming those are all good, follow Dave's advice, it's not difficult to fix, good luck.