Singlespeed & Fixed Gear - rear wheel rubs slightly when under pressure

hi all, wondering if you might have any experience with this...

lately I notice when I apply hard backpressure while slowing, or hard forward-pressure while accelerating, my rear tire rubs against the fender or the rear brake pad. It happened just now and I presumed it was moving in the dropouts, but then I got home and checked the axle nuts and they were tight.

I am running a pretty low gear (~60") which means I can apply a lot of force in both directions. Trek conversion with horizontal dropouts, and, alas, no chain tensioner.

whaddya think? Frame flex? Wheel flex? (!!?) Or it slips in the dropouts even though it's tight?

Has this ever happened to you?

Thanks

Patrick

I had a problem with the back wheel on my old conversion and realized that the brazing on the seat stay had cracked. I don't know if this could be your problem, but it's worth a look.

i had this problem with an old road bike that didn't have a QR rear wheel. i hadn't tightened the bolts properly and the force of the chain was pulling the wheel forward on the right side, so that it rubbed on the left fork.

does that make sense? i think i said it how i wanted to...i think i'm getting sick again...

makes sense. maybe i just need to tighten down the bolts more. and use a tensioner.

I had exact problem on a mountain bike and I had broke the axle

yeah, i've had that, too. but check the little things first, then work your way up.

oh, and i don't think you need a chain tensioner. i think very few people on here use them.

i poked around...frame and axle are solid. seems to be frame flex, exacerbated by the fact that I could use another link in my chain (ha ha) to keep the wheel a little back from the fender. Plus I just gotta cool out on the mega torque! Dude! Mel-low.

torque demon.

could be loose bearing cones, causing a slight amount of hub play as well.

Can you get chain tensioners for horizontal dropouts?(not fork ends)

Those spur ones they sell at Danscomp are pretty popular among conversions at the FGG.

In additon to what they said, I would check spoke tension, or more specifically, the evenness of tension around the wheel.

2nd the suggestion that you check for play in the hub and examine your rear wheel spoke tension. It could be frame flex but it would have to be a pretty weady frame to move that much.

I'd also visual check for cracks etc if the frame if alu

could be loose bearing cones, causing a slight amount of hub play as well.

i second that, if you say that the bolts are on tight it's probably the cones being too loose. i can't think of anything else, i don't think the spokes being under tensioned would be too much of a problem.