Newbie with a tricky one?

Ive just aquired a Bianchi Pista and I'm made up with it....

There is a slight issue that I'm not sure about tho.....The main chainring doesnt seem to sit on the spider completely centrally making the chain tight, then looser, then tight, then looser ect when the pedals are turning....what would the likey cause of this be? I'm thinking

1. shite chainring
   2.shite spider (truvativ OEM I think)
   
2. Shite mechanic (ie me)
   
   

Any ideas?

http://sheldonbrown.com/fixed.html#tension

Also: http://www.lfgss.com/thread23972.html

Your chainring is not located centrally on the spider. Consult www.sheldonbrown.com

Basically loosen all the bolts until you can move the ring, and then fiddle and fiddle and fiddle until you realise it will never be perfect, but maybe better than it is now :)

Chainring might not be centered on the spider?

http://sheldonbrown.com/fixed.html#tension

^^^ Too late

Bunch of slow bastards...

;)

Thanks guys....I'll get on to Sheldon now.

I tried to loosen all the bolts and then turn the pedals in the hope that it would self centralise, but to no avail............

I'll see what sheldon has to say about it...cheers!!

That looks spot on, cheers!!

I had am idea that it was something like that, but wouldn't have thought to hit the chain with something to centralise....

His way of explaining things reminds me of a VW guy called John Muir......legend!!

just went and set the bike stand up and had a bit of a fettle.....even following those instructions, it still seems to be slightly out..........it rides well enough, but im being a bit anal.....

I'm suprised no one has mentioned this but the problem could simply be that the chainring is not perfectly round. On my old cranks i always had the same problem, then since i have been using sugino 75 cranks and a zen chainring the problem has gone.

Its no big deal though so ride your bike and enjoy it.

just went and set the bike stand up and had a bit of a fettle.....even following those instructions, it still seems to be slightly out..........it rides well enough, but im being a bit anal.....

On the whole the more you spend on cranks the rounder they are. S75s, Campag Pista and Dura Ace are the roundest three out there for sure. But all weigh in at over £200 more or less.

The problem is that the Bianchi Pista comes equipped with the worst chainset imaginable (bar a unipacks cranks of course). If you've managed to get it better than it was before then you are probably not going to get it any better. If its really bugging you change the cranks for proper cranks (along with the chain and sprocket of course). But then you'll also want to change the wheels and frame too :P

I'm suprised no one has mentioned this but the problem could simply be that the chainring is not perfectly round.

mentioned on the thread linked in the first post. nuff said.