Skipping Gears!!!

[standard-issue]

Hi,
Very new to this game, (I've been out twice) but from riding BMX for many years i know my way around a bike, until it comes to "gears" (well multiples).

I'm running an 18speed ultegra set-up, i bought the bike second hand (just graduated from uni, very, very poor). The bike had just new cassette, front deraileur amongst other parts of the drive chain.
The problem I first noticed was the front deraileur wasn't sifting properly (especially to the big sprocket going up hill, yet i'm told this can be expected), being "mechanically" minded, i dismanted the front gear set up with a "let the dog see the rabbit" attitude, with a bit of re-threading and tapping of bolts that had being cross-threaded i got the front shifting perfectly, now after this the back became really hesitent and started making such a racket, i fiddled and tinkered (youtube was very helpful) and with the back wheel off the floor spinning the cranks it shifts perfectly smooth, i took it out for 10 miles or so today to test it, it was fine climbing hills and cranking down them, but when it came to steady cycling through traffic the chain was skipping around the middle cogs of the cassette.

So i guess, finally getting to the point, my question is, Whats the problem likely to be, is it indexing, chain, cassette, shifters or something else?

any help or guidance to a recent (relevant) thread would be greatly appreciated.

Thanks


PRO

 

[Noodley]

possibly new chain required by the sound of it.

 

[Bigtallfatbloke]

http://bicycletutor.com/

 

[standard-issue]

Thanks for the link and the advice.

I'm getting the bike re-sprayed soon, so i'm going to have a major overhaul, service.

New cables/chain, degrease everything, re-lube/grease.

 

[swee'pea99]

Have to cnfess to being slightly baffled as to how xtreme poverty tallies with resprays and major overhauls, but as noodley says, if the cassette is new and the chain is not, it's certainly up there as a suspect. Conventional wisdom says if you change one you must change t'other.

Try putting a 12" ruler up against the chain, and seeing whether when the wee line by the zero is lined up exactly with the centre of a link, its 12" counterpart is similarly lined up to the same point on *its* link. If not, that's very likely your problem and you need a new chain.

 

[Tynan]

easy simple check is something wrapped round between the cogs

I once had a few inchs of elastic strap plus s hook

soon after the same going missing from the inside of my cheap panniers

it was rather black and tightly wrapped between the cogs and hard to see

 

[standard-issue]

[quote name='swee'pea99']Have to cnfess to being slightly baffled as to how xtreme poverty tallies with resprays and major overhauls...quote]

The re-spray is £35 and it looks like an overhaul is needed as its second hand, although the 12" rule was useful, a fair bit of stretching.

new chain!