baribari

Using my direct drive trainer seems to be gradually wearing my aluminum dropouts down.

Could I could something like metal repair putty or JB Weld to slow down or even reverse this wear?

dsbrantjr

Highly doubtful this will work.

dedhed

Washers

Wilfred Laurier

Don't direct drive trainers use a QR mechanism similar to the wheel?

IF this is wearing down your dropouts then I would guess you aren't clamping the QR or whatever mechanism tight enough. There should not be any movement that could cause wear. I could be wrong, though.

woodcraft

No.

You could try, for no real benefit.

CliffordK

My guess is the forces are slightly different on the trailer than on the road. When one leans a bike on the road, the wheel leans.
On the trainer, leaning the bike would be fighting against a fixed device.

Nonetheless, you are likely right. There really shouldn't be a limit to how tight one gets a quick release on either aluminum or steel dropouts (I'd be careful with pure carbon fiber dropouts).

As far as the JB Weld remedy, I'd be skeptical, but it would be easy enough to try out. Perhaps do one side and see if it helps.

Wilfred Laurier

CliffordK Bikes have been rigidly clamped into trainers by the rear axle for decades. There has always been talk about the possible stresses this would place on the frame, but usually in the context of the whole structure of the frame being held rigidly by the rear axle, and not about the inability of the clamped rear axle to be held in place.

Bill Kapaun

Maybe a "sandwich" with thin shim stock bearing against the axle threads/drops?

_ForceD_

I've never used, nor even looked at close-up, one of those DD trainers. But looking at online pics of them, and from what I read, it looks as if they use threadless axles. But if so...it's odd that there's so much abbrasion there. But it's hard to tell. Is it possible for you to post a close-up picture of where the wear (odd combination of words) is happening? Otherwise, my suggestion would be in line with those above that suggest fashioning a thin metal tube to fit over the (presumably threaded) axle, but will still fit in the dropouts.

Dan

jadocs

I agree with Wilfred, if your bike is moving within the drop outs something is not right. Seat stay and chain stay flex? sure...but not moving in the dropouts.

baribari

I'm clamping the bike plenty hard, but every time I take the bike off there's traces of aluminum powder.

easyupbug 

Like others have said I don't understand the mechanism your having for the powder showing up but I would try JB, it is cheap. JB and the similar products on the market will stick to clean aluminum and are rated (somewhere on the package) and designed for Tensile Strength which is not important in your application as I understand it. However, I think your issue is erosion by impacts normal to the surface which is not a strong suit for aluminum and maybe the steel in the JB epoxy might hold up much better to the erosion you are seeing.

63rickert

I agree with the ideas above of using washers or shims.

All stationary trainers have always been hard on the bikes. The best way to do this is to have an old beater that you don't care about. Keep it running well enough that you get a real workout and not a fight with a malfunctioning bike. Otherwise let sweat corrosion take the bike and don't worry about dropout wear.

biketampa

I’m just not buying “all stationary trainers have always been hard on bikes” is entirely true. I’ve been using my bikes on a trainer for many years now with zero issues. And indoor training with Zwift,rouvy, trainerroad, sufferfest, etc is probably more popular than ever so there are 1000s and 1000s of users riding indoor and there just aren’t that many stories about trainers causing problems with bikes. There certainly are but they don’t seem to be a common occurrence.

63rickert

Stories of bikes getting messed up on trainers are infinite. If your bike never has a problem on the trainer you and I are living in alternate universes. That will happen in online discussions.

biketampa

I’m thinking we disagree on how much of an issue it is. I don’t disagree it must happen but given the number of people training indoors I would expect far more frequent posts on places like Zwift forums, trainerroad forums, etc. I’m sure there are examples but I would expect a lot more if it was very common. I will say for my own personal experience I tend not to stand up and sprint on an indoor trainer and if I do I’m pretty cautious. I’ve seen others not be so cautious which makes no sense to me.

rm -rf

Yes, this sounded good to me. But I wonder if the trainer has a knurled surface where it contacts the dropout. And many quick releases do too. Perhaps a smooth shim would slip against the dropout? It's easy to try though.
I wouldn't use a steel washer. An aluminum shim wouldn't wear at the dropout, just on it's trainer side -- good.

The hardware stores have thin aluminum sheets. Drill a hole for the dropout, then cut out a washer shaped piece. Scissors should work if it's thin enough. Scuffing it with sandpaper before drilling and cutting would help it's grip.
Home depot 6 inch x 18 inch alum sheet. $4. No info on thickness, and it needs to be ordered.
https://www.homedepot.com/p/M-D-Buil...6080/205058552

baribari

The trainer QR adapters and skewer have a knurled surface that leaves marks in the dropouts. The bike isn't visibly moving in the skewer, but I suspect given the forces involved (probably many, many times higher than on the road) there is going to be SOME microscopic level of movement that wears on the weaker material.

I applied a little bit of aluminum epoxy designed for aluminum rim repair (no local shops carry JB Weld), but I don't think it's anywhere near hard enough for use on a wear surface.

The inside of the dropouts isn't wearing, just the sides.

baribari

That was the idea. It also needs to be very hard to avoid being marred by the knurled surfaces of the skewer and axle.

Basically I just want a surface that's tougher than aluminum.

tFUnK

Yes I did this once. I hit a pothole and crashed and it pulled my rear wheel out from the dropout, leaving a small gouge. I didn't notice my rear wheel was misaligned until I tried a set of wider tires and one side would always rub because the force of pedaling would pull one side slightly. I took some JB Weld and filled/shaped it into the area with missing material and let it cure completely. I shaped it well enough that I didn't have to file/sand the area after. Fixed the problem for me but I didn't get to put too many miles on it before selling the bike due to moving.

Edit: ok realized OP's issue is the sides of the dropout surface wearing not the dropout itself. Maybe just put some frame protect tape around the dropout and use washers between the frame and the clamp.

JohnDThompson 

One thing I've done with steel dropouts is to braze a stainless steel washer onto the dropout face and cut a slot for the axle. This provides a durable face on the dropout that can be masked off when painted. I suspect you could epoxy a washer onto an aluminum dropout in a similar manner.

baribari

Wouldn't that change the axle spacing? I might consider that as a last resort if it gets any worse. Would probably use a very thin wafer of stainless steel. No need to mask it off, though. Dropouts are painted in the factory, although it naturally wears off.

dedhed

They come in all kinds of thickness. Looks like .3mm is thinnest.
https://www.ebay.com/i/312838201624?...r=611554595326