How much out of roundness is acceptable on a new tyre?

[531colin]

Thanks for replies I will try some of the ideas above to see if I can get it to fit better.

Question would having undersized tubes cause this ? I am currently running 35mm tubes in these ill fitting 44 tyres.

No, undersize tubes are fine.

If I have (at last!) got my head round whats going on, you have 2 tyres;
tyre 1 fits both front and rear wheels
tyre 2 fits neither wheel

If thats the case, tyre 2 is undersize. (They may try to tell you its within the allowed tolerance of sizes, which may be the case; but it doesn't fit your wheels, and the other tyre does!)

[NickJP]

Here's one I rejected due to both out of round and side to side hop - after I showed them this video, the bike shop didn't demur about taking this one back and supplying another.