Please help me with my gears!

Welshkev

Any help on this would be hugely appreciated.

Basically when I'm on the small/inner ring on the front, my chain is scraping against the front derailer when I'm on the 'outer' (furthest away from the back wheel) last 3 or 4 cogs on the back cassette.

Then if I go on to the larger front ring, the chain scrapes against the front derailer when I'm on the 'inner' first 3/4 cogs on the back cassette (those closet to the back wheel).

The scraping noise is really annoying and drives me mad. I had the bike servied a couple of months ago and was pretty good after that, but is started again, so I took it to be adjusted again, but the problem persists.
Any advice?
Cheers!

andy69

generally you should avoid the last sprocket or two when on the small ring at the front, and vise versa.
But...there should be an option to slightly move the front mech so that it stops rubbing off the chain: if on the small ring, just put a bit of pressure on the shifter for the front mech....it will click once and that'll move it off the chain, but still keeping you on the small ring.

jimm

There's nothing wrong with your bike. Just try to avoid "cross chaining"

http://www.bicyclechainrings.com/crosschaining.html

Welshkev

Thanks - definitely sounds like cross-chaining to me. But surely - as the back cassette only has (I think) 9 cogs, not being able to use 4 of them is a bit, well, silly?

ashleey

Have a look at dérailleur adjustment on the park tools website it is an excellent resource and should help you remove some of the scraping

-PornStar-

Kevinleeowen wrote: »

Thanks - definitely sounds like cross-chaining to me. But surely - as the back cassette only has (I think) 9 cogs, not being able to use 4 of them is a bit, well, silly?

You can use them. But if you get to a stage where you are approaching the small cog on the back, while in the small cog on the front. What you should do is, shift to the large cog on the front, while simultaneously shifting once or twice, to larger cogs in the back. This maneuver will put you close to a gearing that you started from.

So from there, you can continue to shift into smaller and smaller cogs at the back. And make full use of the cassette.

This transition should be relatively smooth. Without a massive change in the amount of pedal power required.

Edit:- Fundamentally. The reason it works this way, is that there is an overlap of gears.

So instead of being set up like this,

Front small cog gears 1, 2, 3, 4, 5, 6, 7, 8, 9
Front large cog gears 10, 11, 12, 13, 14, 15, 16, 17, 18

It works something like this,

Front small cog gears 1, 2, 3, 4, 5, 6, 7, 8, 9
Front large cog gears 6, 7, 8, 9, 10, 11, 12, 13, 14

andy69

Kevinleeowen wrote: »

Thanks - definitely sounds like cross-chaining to me. But surely - as the back cassette only has (I think) 9 cogs, not being able to use 4 of them is a bit, well, silly?

yeah i know what you're saying, but as PornStar says, after you get to about 6th gear, you flick up to the big ring and back a few sprockets then to like a 'virtual' 7th if ye know what I mean (easier to do than explain)

anyhoo...the idea is not that you can sequentially go from 1st up to 18th, but that you are covered for all eventualities: like on a hilly spin, you can use the first couple of gears to get up the steepest of hills, and coming down the other side you can use the big ring and highest gears (so you're covered from 5km/h to 55km/h), and of course, every speed in between. simples :P

Welshkev

I think the problem is that the 'cross-over' point - between going from the small to big ring - seems to be exactly when the scraping is happening. If I could just get even one more ring on the back cassette either way I'd be fine.
I've printed off that Park's guide so will try that this weekend - just hope I don't make them worse!

cdaly_

There should be 'trim' positions on the left shifter to allow you to move the front mech just a small distance. A normal front mech shift involves two clicks of the shifter (you should feel these in your fingers). It should be possible to shift by one click which won't actually change gear but will just move the mech over a small bit.