How much of my cassette can I use?

[cassettequestion]

I have a 10 speed on the back and compact double on the front.

Took it to the bike shop to set up the gears because I couldn't do it. Had a little ride around and found the chain rubbing against the front mech when I was using the big cog on the front and 7th biggest on the back. I took it back to the shop and they said that was normal and that I should only expect to use the smallest 6 on the back. To be honest, this is being conservative as well as I'm sure it was rubbing in anything but the 5 high gears on the cassette..

My question is - is that correct? I do understand you're not supposed to use a big to big or small to small combination but telling me I can't use pretty much half the gears seems a little off to me. I've had other road bikes before and tended to ride around in the 2nd or 3rd biggest gear on the cassette when on the flat and didn't notice this problem.

Grateful for any help or clarification. Thanks.

 

[fossyant]

Usually the last 2 should be avoided. The chain will rub the front mech as you get near the last two, so you give the front shifter a little click to trim it.

 

[fossyant]

That is assuming the front shifter has trim.

On the big ring, as you get near the bigger rear sprockets, lightly click the 'downshift' and the front mech should move a little 'in board'.

Similar when in the small ring, a little upshift click should move the front mech out a little when changing to the smaller sprockets.

 

[cassettequestion]

OK thanks - so I should be able to use 6, 7 and 8 really (10 being the largest sproket)?

I'm not sure what trimming is - is this something I can do whilst riding the bike or when I'm setting it up?

 

[cassettequestion]

OK just about to ask what you've answered - thanks

 

[cassettequestion]

PS I'm using shimano 4700 mechs and shifters and an FSA Omega crank

 

[gavintc]

I get this on my road bike with a compact chainset (50-34). Trimming it helps and allows a couple more gears when in 'cross over' position. But I cannot use the range I have on my winter bike with a standard (52-39) chainset. To be honest it is not a major issue and crossover is not advised anyway. It just reminds me to do front derailleur shift.

 

[Yellow Saddle]

@fossyant 's trim mentioned above is important and will give you about two extra rub-free gears. Crosschaining should be avoided as it is bad for chain, cassette and chainring, again as he says.
However, the number of gears practically available to you is a function of chainstay lengt (the shorter, the fewer) and frame flex. If you have steel frame one of the older thin-tube aluminium frames, the tubes at the BB flex quite a bit and you will experience rub on gears where the chain is already close to the front derailer.
Mechanics find it difficult to guess your perfect set-up although they can take more trouble in working with you in finding those sweet spots. I suggest you learn how to tweak these things yourself. You are the best judge of what works for you and what not.

 

[MichaelW2]

Tiagra should have a trim function in the shifters; mine does.
As far as I remember, it only works in one direction, using the paddle to catch some small intermediate clicks. The other direction shifts you right back to the main indexing point.

 

[Kajjal]

On a compact 10 speed you should be able to use 8 of the gears with no issues. A bit more fiddling, possibly more but the cross chaining makes things less reliable.

 

[cassettequestion]

OK so when I'm in, say, the 6th or 7th (10th being the largest) on the cassette, I need to click the left paddle once, as though I was shifting to the small chainring on the front, without actually doing it?

Kajjal - I thought I should be able to use 8 as well..

 

[Svendo]

Access the tech doc at si.shimano.com and the 'dealer manual' for Front Derailleurs. Adjustment and trouble shooting is on pages 15 & 16. I'd try SMALL adjustments of the inner limit screw first, to see if a small tweak will help. If the chain falls of the inside or there is trouble shifting back up adjust back, or start again from scratch (probably don't need to undo the cable, but just start from 'low adjustment'). When my FDs have gone screwy, this is usually what I've ended up doing after much fiddling with the cable barrel adjuster. Also check the mounting and alignment haven't shifted, that'll undo you're adjustment.
The other thing to consider is if you do need to increase the inboard motion with the low adjustment, fitting a chain catcher which will reduce the likely hood of the chain falling off the inside to close to zero.

 

[Kajjal]

OK so when I'm in, say, the 6th or 7th (10th being the largest) on the cassette, I need to click the left paddle once, as though I was shifting to the small chainring on the front, without actually doing it?

Kajjal - I thought I should be able to use 8 as well..

Yes in the largest chain ring you can use the smallest eight gears easily enough. In the smallest chainring you can use the largest eight gears easily enough. Once your fitness improves this should become less of a problem. Changing the rear cassette to an easier one can help if needed.

 

[Ajax Bay]

when I'm in, say, the 6th or 7th (10th being the largest) on the cassette, I need to click the left paddle once, as though I was shifting to the small chainring on the front,

Yes, but trimming: only a 'little' click. Important that you have the FD set up correctly (limit screws, cable tension etc).
Have a look at this gear calculator. I have set the cross chaining limit to 2.1 and have used a 50-34 and a 12-25 cassette, but you can change it around.

 

[cassettequestion]

Hi, thanks for the link - little unsure what it's showing me?

Think I've got the trimming think down though - it's actually what I did on my old bike without realising it. I'd change up on the cassette and noticed a funny sound, which would go when I gave a little click to go back down (this was a SRAM setup).