I just received in the mail today a pair of MKS chain tensioners, but, much to my vexation, the track ends on my Alien are too wide and the wheel is too far forward for how long the tensioners can extend. I bent one of the forks of a track end in a wreck so my wheel slips forward gradually while I ride because it doesn't grip well enough as they are slightly off parallel. Although it is not quite life threatening, I really need a solution. Will BMX shops have what I need?

Are you using track nuts?
Add a couple of links to your chain to move the wheel back maybe?

Can you just mod the MKS tensioners by putting in longer bolts? I bet they take an M5 which you could get at a specialized fastener place. Otherwise, I'm sure there are lots of tensioners on the market that will work---a bmx shop is likely to have something.

Nah, you can't add longer bolts, it's a weird shape, and part of it is reverse threaded. And I can't add more chain links and move my wheel back because since the end is bent inward, there isn't enough surface area for the bolt to grip.

I'm pretty disappointed in this product for the price ($34); it seems very cheaply made.

Um... Have you tried straightening out the trackend? Put it on something solid and hammer it out flat.

That will eliminate the need for the tensioners.

Umm, bike shops have tools for this kind of thing.



It's an easy fix that shouldn't take more than a couple minutes.

Which MKS tensioners did you buy? Although the NJS ones are meant for steel frames, you can try the aluminum ones which are wider (3mm vs. 5mm if I recall correctly).

I concur with posters above: getting your frame straightened sounds like the best solution.