Dickhead question about rear mech

[danphoto]

Just had the chainwheels and front derailleur on my Dawes Mojave (I know, I know) changed to an MTB set to lower the overall gearing for trailer towing, and a new chain fitted.

The front gearchange is fine, but whereas the rear indexed 100% before, it now refuses to play with 2nd gear. Going up or down to 2nd makes no odds, the chain just jumps/slips. Everything else is hunky dory (what is a hunky dory?) and this is a 21-speed bike.

Two questions: does the fact that it's only the indexing of 2nd by the rear mech provide a clue for what the cure is? And could somebody please give me a link to any good site for clueing me up on adjusting derailleurs?

Thanks

 

[dodgy]

It's because you've put a new chain on a badly worn cassette. If you change the chain before it gets to 0.75% 'stretch' or worn (sounds not much, but it isn't) then you get away with needing a new cassette.

 

[skwerl]

so it won't go 1>2 or 3>2 but all other combinations work?

 

[dodgy]

I bet 2nd gear on the back was the OP's most used gear - hence the cassette is worn.

 

[danphoto]

OK ... I think I hear a nail being hit on the head. Yes, 1>2 and 3>2 are the only no-no, and yes, 2nd has probably been the most-used rear sprocket in the 1500 or so miles I've done on it.

So ... am I right in thinking that in view of the fact we're talking well used (wait for it) Shimano Tourney, the logical way forward is for me to fit a complete replacement i.e. cassette and rear derailleur?

If so, are direct replacements still available (15-34T, btw)?

 

[dodgy]

You won't need a new derailleur, just the cassette. In future, keep tabs on your chain by using one of these http://www.chainreactioncycles.com/Models.aspx?PartnerID=79&ModelID=10219

 

[danphoto]

Thank you very much indeed for your help gents. I've managed to find the right 7-speed multiple freewheel in stock here and I'm guesing that this is the right tool for the job.

Correct or not?

 

[PpPete]

I don't know if that's the right freewheel for your bike, but the tool does go with that freewheel. However you only need the tool to get the old freewheel off - and even then they can be a brute to shift. Suggest you take the wheel off (leave the tyre on), take it to the LBS, ask them to remove it for you. With the right tool in a big vice, it's a 30 second job, and one my LBS doesn't charge for.

The new freewheel will just spin on with your fingers, and tighten itself through pedalling action.

You are sure it is a freewheel, not a cassette aren't you?

 

[danphoto]

You are sure it is a freewheel, not a cassette aren't you?

Fairly. How do I tell for sure when it's on the bike?

ETA - OK, answered my own question

 

[gbb]

Be aware Dan, when you fit a new freewheel, as porkypete says it'll tighten itself up with the pedalling action.....but what you may not expect is the sensation of cycling through a oil slick as it does so.
It only happens for a few seconds as the freewheel really tightens itself onto the wheel...but its a wierd sensation.