New cyclist having trouble with gears

[Phalanx]

Hiya all,
I recently bought a new mountain bike. I took it out along some of the Glasgow tow paths today, to see how I did and everything was fine except that the gears kept slipping as I was cycling.
I've noticed that they only slipped when the chain was on the smallest rear gears (5 & 6), but I'm not sure if it was the front or rear gears slipping. I think it was the front gears but as I say, I'm not totally sure.
I thought it might be the force that was being exerted on them, as I'm a big guy (so I could understand that the teeth of the gears would be under a lot of pressure), but the gears continued to slip when I was travelling at a fairly constant speed on level paths.
I talked to some guys at Halford's and they told me to tighten one of the screws on the front derailleur until I felt resistance. However I tried that and all it did was stopped me from shifting up into the 2nd and 3rd frontal gears.
I'll be on pretty regularly so if you have any questions about the situation, or any things that you'd like me to try or find out, just let me know.

So I'm totally stumped, and any help that anyone can give me would be VERY gratefully accepted!

Cheers.

 

[KellyT]

My Bianchi was doing this recently and it was a stiff link in the chain. If you run round the chain checking to see if the links all move freely, you may spot a stiff link. Also pedal it over with the wheel off the ground and watch what's happening. You should get a clue to the source of the problem at the exact point it skips.

Next guess, the chain is damaged 'laterally'. We had a mountain bike with the joining link not properly driven through, it skipped gears in the same way, while the chain was getting ready to break. Again look carefully for any sign of damage.

Final guess, the chain is plain loose and isn't sitting to the gears tightly enough. Check on the internet for the rules of thumb to see where the rear mech and gears are sitting. You should be able to see if the rear mech is under insufficient tension.

These things can be really annoying. We've been fixing the front mech's on our bikes this week end, which were delivered brand new, with wrongly adjusted gears. Either it's a huge nuisance to an enjoyable hobby, or you try to garner a test for being an amateur mechanic.

 

[Phalanx]

Thanks for the advice, I'll definitely try all of your suggestions.

I think it might be that the spring in the part of the rear gearing system that keeps the chain under tension might just not be powerful enough to keep the chain taught. So pretty much what you said...

I'll try to test it all out in the morning, but I'll have to look around to see what to do if that IS the problem.

Thanks for the advice!

P.S. Strange coincidence that you, too, are in Scotland.
P.P.S. In another strange coincidence I'm studying Mechanical Engineering (although it hasn't helped me thus far )

 

[Don Shipp]

Teething problems.

 

[gclark8]

If you are studying mech eng, go to a good bike shop and ask them to teach you the set up proeedures for both derailleurs.

The Shimano Web Site has service diagrams for each part, Park Tools and Sheldon Brown both have very good help pages.

Where did you buy the bike? There should be at least 12 months free service.

 

[Phalanx]

Where did you buy the bike? There should be at least 12 months free service.

Good point...