Derailleur Question

Beardy10

Excuse my naivety I have recently bought a new road bike and am not very happy with how the bike shop have set up the both the Front and Rear Derailleur and want to make sure of my facts before locking horns with the bike shop. They normally need a week or so to service bikes but I want this done pronto. My "other' bike is an MTB and have recently rediscovered road bikes so am not sure what to expect of modern equipment.

My bike has Dura Ace has front and rear mechs. Compact chainset and 10 speed cassette.

First the front derailleur needs a much more definite action to move to the chain to the smaller chainwheel than the rear derailleur does. Is that right ? I would have thought it should need the tap that the rear needs...it feels a lot stiffer. Given it's Dura Ace I was expecting a slick feel!

If I have the the chain on the small front chainwheel the chain starts rubbing on the front derailleur when it is perhaps in the fifth biggest cog at the back. Surely that is a badly adjusted front derailleur?

Whilst on that subject what is the accepted wisdom on which gear you can run on the rear cassette with the chain on the small front derailleur without the angle causing too much wear.

I think I know what the answer is but like to make sure of my facts. I should add I have only done 40 mils on the bike and know that a new bike will need adjustments to the brakes and derailleurs but wouldn't have thought it would this quickly.

andrewgturnbull

Hi there.

Yes the front derailleur will always need more than just a wee tap, even the might DA (until we all go electric).

You'll find that there are two trim positions on the front deraiileur, one just above the inside ring and one just below the outside ring. You get to this position by doing a sort of half-shift, using gentler pressure on the lever. This should alleviate most of the chain rub. If this still doesn't work then you need to play with the adjustements on the derailleur itself.

Personally the only gear comination I avoid is big-big (e.g. 53x23), but you can even get away with this for short periods. I don't see a problem with running small-small (e.g. 39x11). My cross bike spent an awful lot of time in this combination while racing with no ill effects, or chain run.

Cheers, Andy

Beardy10

Thanks for the prompt reply Andy,

That half tap makes sense now.....if when I am on the big chain ring I just give it a tap it doesn't actually drop the chain to the inside ring which I assume is what you are talking about? I will have to have a play in the morning.

synchronicity

I stay of the last three or four cogs at each end of the block to avoid big-big and small-small gear combos.

Front Derailleurs always need more effort at the shift lever than Rear Derailleurs.

itisaboutthebike

Plus if its a road double front mech on a compact chainset(16 tooth diff) then the shift is not going to be as crisp as it would be on a 39/53 (14 tooth diff)

Doobz

with it also being pretty new you might need to take it back to the LBS to get them to tighten all the cables after a couple of hundred miles as they have a tendency to stretch a bit and make your gearing really unpredictable,

Eat My Dust

I do most of my riding on 50x25, which I know you're not meant to do. I was speaking to the guy who owns my LBS and he reckons that on a compact 10 speed it's not a problem. TBH when I had a standard double I rode mostly in 53x12 and never had any problems either.

robbarker

Eat My Dust wrote:

I do most of my riding on 50x25, which I know you're not meant to do. I was speaking to the guy who owns my LBS and he reckons that on a compact 10 speed it's not a problem. TBH when I had a standard double I rode mostly in 53x12 and never had any problems either.

Not a problem for him, certainly, if his customers wear their chains and sprockets out very quickly.

Compacts do tempt you to run silly chain lines so that you can stay in the big front ring, rather than chage every two minutes. That's the main reason I've gone back to a 53/39, with a bigger cog on the back to make up.