Looks like I need new cranks

Since I built up my current fix about 18 months ago I never managed to figure out why I couldn't get the chain tension just right. You'd expect a small discrepancy in tension during a full revolution of the pedals, but it has always been big enough to bother me. My first chainring used to slip and I put that down to cheap chainring. But that soon settled down. But there was still this tension problem. So I eventually got a new higher quality chainring which was better but still not smooth. I tried Sheldon Brown's chainring truing exercise, which improved the situation again, but did not eradicate it. But it never occurred to me to check the cranks till yesterday.

I had taken the chain off to clean it and when I spun the pedals I noticed clearly the change in distance between the ring and the seat tube. Not good. Of course it could be the BB axle, but I checked that for movement and it seems fine. So it looks like I need new cranks. Not hugely urgent as I've managed to get away with it for so long but I would like to get that tension really smooth. It's a 110BCD crank with square taper fittings. Any advice?

Don't want to spend oodles of cash. Maybe £40 - £50. The ones on hubjub (Sugino XD) look good and would fit the bill. Anyone used them?

The other option would be to try and reset my current cranks some how. Don't know if you can bend them though as they are forged. Perhaps some gentle taps with a mallet.

Just saw these on ebay, but they're located in the US. Could take ages to arrive.

http://cgi.ebay.co.uk/TRACK-FIXED-GEAR-ROAD-BIKE-CRANKS-CRANKSET-165MM-165-SL_W0QQitemZ180198583083QQihZ008QQcategoryZ56195QQrdZ1QQssPageNameZWD2VQQcmdZViewItem?_trksid=p1638.m122

check out old shimano 600 cranks ( some were dura ace quality but till 600's )they have a campy record look to them but way cheaper and it's good quality stuff
or old shimano 105 equivalent cranks
cheap on the bay

Maybe the chainring itself is bent and the cranks are okay?

Presumably you checked his already - lie the ring on a flat surface and ... it should be flat too.

If it is the cranks don't bend them, bin them, even if they do not snap they will stress and will likely break some other time.

In theory is possible to reforge the cranks/spider - and there are techniques to prevent/remove the stress during/after forging, but you need to find someone who knows how to do this, and the cost will be more than the price of a new set (not to mention that they will need refinishing again afterwards).

Don't ride on them either, if they are bent they are already stressed.

Also ...

Zippie
Don't ride on them either, if they are bent they are already stressed.

Blimey, I'm a bit scared now. I've just changed my back tyre as the red was starting to show all the way round (armadillo) so now getting new cranks is urgent too. Suppose it gives me an excuse to splash out and get a new set.

The ones I have are not single speed specific ones. I'll have a look on the bay, but if I find nothing then I might go for the hubjub ones: the Sugino XD.

Check these:

RPM Crankset

£30!
Collect 'em from Hackney ;-)