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Slipping gears and gear shifting
Hello All

My first post on the forum, as i really need help with the problem i have on my bike.

I have a GT outpost which i use to commute to work ( about 15 miles a day) I've had some problems with my rear gears as the chain keeps slipping whenever i am going uphill feels like the chain is loose happens especially when i am on smaller gears. thinking it need retuning i took it to Halford for a routine service, they adjusted the gears, but told me the rear deraileur isn't going into some gears.

It go into gear going up and when i unclick it hangs on some and goes after 2 or 3 clicks. The Guy told me it could be the rear acera derailleur or something else.

Has anyone experienced the same thing ?
Slipping - chain wear
"not going in gear" - gunked up dérailleur -> clean, worn spring -> replace dérailleur
To add a couple of ideas.
Frayed inner cable inside the cable housing near the derailleur.
Also if the cable routes under the bottom bracket then check that it's clean under there.
Ride hard or ride home alone!
i've had the bike service by a halford mechanic. cables has been changed and gears retuned. he came to the conclusion that the rear mech is faulty and needs replacing, he was going to use an alivio but said the ratio is different.

i am going to replaced the rear deraileur myself and wondered what one will be suitable for my gt outpost

Thx in advanced
If you can tell us what brand of shifters you have and how many gears are in the back we can tell you what derailleur would work.

But I'm a little suspicious about what your exact problem is. You say the "chain feels loose" and that the shifting isn't working well. These could be two separate problems. Do the gears slip suddenly and recatch when you put a lot of pressure on them? Or is it just that it won't shift into the gear you want cleanly?
Guys, may i tag on to this thread with a similar problem.

After cycling throughout the winter to work, I decided to change my chain - which was very dirty and worn, to a nice new sram 890. But now i get gear slippage in the most regularly used gears under load.

This leads me to believe that its cassette wear - although it never happened with the old chain.

My logic for thinking cassette as opposed to freehub, chain length, derailleur or chain rings, is that the gear changes are still nice and smooth, the problem happens in all of the 3 front rings, and it only slips in gears 4,5,6 which are the ones I've used the most.

However, I wanted a sanity check before i buy a new cassette. All thoughts gratefully received.
Read through the other problem discussions regarding slipping gears: if you swap out the chain and the gears slip (and the shifters are set up correctly) the cassette (and possibly the chain rings) are worn too. Do you still have the old chain? If so: measure the chain wear as in http://bikeride.com/chain-wear/ and check how bad chain wear was. It most likely was the culprit, but it is hard to tell not knowing how badly worn the chain was and if the gears are set up correctly.

Edit: Sorry if this sounds unfriendly / harsh, it is not really meant that way
This is a common problem after replacing a chain, everything wears out together and frequently everything needs replacing together, check out the teeth on your sprockets and cw, if they are getting "pointy" they will need changing, may also need new jockey wheels in rear changer.
My lbs changes one part at a time and assesses the situation,before spending more.
Hi all,

I managed to find out what the problem was, my cassette prevent the gears from changing smoothly, replaced the cassette and everything worked fine after that, Thank god i didn't listen to the Halfords mechanic it would have cost me a fortune. Thanks again for all your contributions to this thread. I now have a sram cassette and chain working well with my shimano acera. I wanted to get a sram rear mech but some guy in action bikes in central london told me they won't work even if i get a ratio compatible one my current mech is acrera 8 speed 1:1 ratio. Can any one tell me a good sram rear mech for my bike ? I have shimano 8 speed shifters and the bike i have is a GT outpost 2009
If I remember correctly, somebody pointed out (Bill? DaveM? cyclerUK? somebody else?) that unless you also buy SRAM shifters it won't work. If you upgrade the shifters you could also make the transition to 9 speed...

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