Ali frame MTB worn drop out problem help please.

[BADGER.BRAD]

Hello all,

My lad (a destruction engineer) has been using my Ali frame MTB for work he was complaining that the rear tyre was rubbing on the frame when I inspected it the wheel was slightly loose and has rubbed the frame drop out meaning it is now permanently loose. Is there any fix for this ?

 

[Ajax Bay]

Clearer description needed.

 

[fossyant]

Pictures. Should be able to tighten up. You can't fix lost metal work though...

 

[BADGER.BRAD]

The wheel has been moving in the drop out and worn it slightly allowing the wheel to move in use, I tried locking it in position using a spanner to give a little extra leverage to the quick release. But after a while the wheel pulled out of alignment. I have thought about trying to drill the frame and fit a spacer but I'm not sure with the basic tools I have I would get this accurate enough, My other idea was to use some sort of chemical metal to fill the gap but I'm not sure how successful this would be.

 

[midlife]

File a bit off the axle so the cam doesn't touch it any more?

 

[wajc]

This sounds like something I've experienced on my commute bike which has disks and QR wheels.

I hadn't had to remove the rear wheel for some time but needed to replace the pads for the disk brakes. I then struggled to get the rear wheel positioned back into the frame without the pads rubbing on the rotor. Once I did manage this even after a short distance of riding (and braking) the rubbing returned (to the extent that the rear wheel would only spin a couple of times before it stopped). I realised that when I released the QR I was able to twist the wheel within the frame and close inspection of the dropout revealed the type of damage you describe. I've a photo of it but the wearing of the frame is not that clear.

It seemed to me that my QR wasn't holding the wheel in place tightly enough so having read some articles on internal and external cam QR I bought a Shimano Ultegra QR.

Bike Radar Quick release feature

Shimano Ultegra QR

The new QR was certainly an improvement on the old one and seems to clamp better. I still had to readjust a few times but now it seems that the rotor rubbing has stopped (or it's just worn the pads down to accommodate - hoping not though!) and that the wheel is secure in place.

I did also buy some metal putty and made a half hearted attempt to place some putty just on the edge of the frame where it was worn in the direction of the axle movement but it didn't stay put. I think to do it properly you need to use plenty of putty so there is enough to adhere to the frame with some strength. I think you'd have to be careful on getting putty on the clamping face though.

Metal Repair Putty

I've not had this problem before on bikes with rim brakes and wonder if it's caused by a mixture of insufficient clamping, whether that being the QR not being tightened correctly or the serrations on cheap QRs not gripping the frame enough, and the fact on a disk braked bike the braking force is on one side of the wheel only - leading to a twisting effect.

My only other disk brake bike has thru axles which I'm pleased about - not sure whether this was one of the reasons for thru axle development but I'm hoping it's solved this particular issue.

It would be interesting to know whether you have the same disk brake/QR set up.

 

[Ajax Bay]

Sounds as if the dropout width (not the OLN) has been slightly reduced by the axle movement. And the axle 'stub' that side (distance between the axle end and the locknut) is now more than the reduced dropout thickness [edited to add: quite possibly already longer than it should have been, hence inability of QR to secure axle in dropouts]. Try to measure those two dimensions and, while you're at it, the axle 'stub' on the other end and the thickness of its dropout. Share these figures. On the basis of what I understand, my first try fix would be an extra spacer on the axle. ETA: Also exactly what make of QR skewer are you using?

 

[BADGER.BRAD]

Your problem does sounds exactly as I am experiencing Wajc, the QR skewers are just the ones that came with the bike ( Diamond Back) so nothing special.I've had the bike 15 years and it has took quite a battering being used for an off road commute for a couple of years plus a lot of XC fun apart from the forks being worn the bike was in good mechanical condition until he got hold of it ! I will have a closer inspection of the drop out to see if the problem is the drop out thickness and try some serrated washers as spacers to see if I can get it to clamp better. It is a cable disc set up.

Thanks all.

 

[wajc]

I think Ajax and I are talking about different things so I've shown an updated photo below. It may well be he has the answer to the problem and next time I have my wheel out I'll be looking at the dropout thickness as well.

To be clear though the wearing of the dropout I am experiencing is in the direction of the arrow due to the axle moving forward against the dropout (I'm guessing during braking). As the frame dropout has worn on it's inner edge (shown by the red line) it's allowing the wheel to twist more and more.

It was to this face of the dropout that I initially put a small amount of the metal repair putty to try and prevent the axle on this side moving forward. That didn't stay put (more down to lack of preparation etc than the putty).

 

[recumbentpanda]

I have had this problem develop in a steel dropout (!)

On inspection, I noticed the axle ends stuck out a mm or so beyond the face of the dropouts. The external cam qr skewers fitted also had no deep recess on the internal faces of the clamps. This meant they were mostly gripping the axle ends and not the drop outs, leaving the wheel free to move a little on each pedal stroke.

Solution was to fit old school internal cam skewers that I also noticed had deep recesses, more than enough to clear the axle ends and provide a firm grip on the drop outs.

This stops the movement, but still leaves a mashed drop out, and the need to position the wheel carefully when re-fitting. I plan to either fit a short stub of brass tube over the RH axle end, or file out the LH drop out to even things up.

When I had the same problem on an alu frame some years back, filing the drop outs was easier, but as they were rear-facing horizontal ones, I was able to add BMX chain tensioners for precise adjustment and consistent positioning on replacement.