Gears - how low do you go ?

[Arjimlad]

This is a question about how much of a cassette to use, from the biggest chainring.

I have always been careful not to use extremes of chainring/gear on an 8 speed bike..

i.e. on the biggest chainring, I have avoided using the largest 4 gears on the cassette,
on the smallest chainring, I have avoided using the smallest 3 gears on the cassette.

However, with my new 9-speed cassette, 12-25, with front chainring at 34-50, how low can/should I go when on the 50 ring?

Avoid the biggest 2, 3 or 4 gears ?

 

[GrasB]

The directions from SRAM & Shimano tech-heads I've had is as long as the chain isn't rubbing on something on the front gears then it's a viable gear. The SRAM rep went a little further & said it's best to stick to the top chainring as much as possible due to efficiency gains. This all assumes that the chain is the correct length.

 

[CopperCyclist]

The SRAM rep went a little further & said it's best to stick to the top chainring as much as possible due to efficiency gains. This all assumes that the chain is the correct length.

That's interesting as I tend to stick to the top chainring anyway, but have often wondered if I would be better approaching from the 'other direction' and using the small one mainly.

Can you expand and explain for a dummy what is meant by efficiency gains?

 

[GrasB]

Can you expand and explain for a dummy what is meant by efficiency gains?

Short version; for the same power at the cranks you get more power at the rear wheel.

Long version; Each gear has its own losses through the drive train. For example 39/11 might lose 7% of your power but 53/11 might lose 4%. Generally the higher the tooth count of sprockets/chainrings the less power is lost as they wrap around the curve. In addition to this the less wrap the mech has to deal with the less power you lose wrapping the chain around the jockey wheels. With modern 9 & 10 speed chains they're designed to work with large diagonal displacement so there is minimal wear & power loss due to running a 'crossed' chain.

 

[CopperCyclist]

Thanks!

 

[TonyEnjoyD]

I have found this wildly varying from drive train to drive train.
As GrasB mentioned there's a lot more tolerance built into the chain and mechs these days, however I have always worked to the straighter the chain (chain wheel to mech) the more efficiently it'll run and less chance of a jump or break under duress.

On an 8 speed twin I personally would work on 5 each ring until you get to the feel of it as they all differ.
Once you get the feel you'll automatically front- shift without realising as you'll know which is best.
Anyway, that's just my way of doing it.

Tony

 

[Arjimlad]

Thanks - some interesting views here..

 

[GrasB]

I have found this wildly varying from drive train to drive train.
As GrasB mentioned there's a lot more tolerance built into the chain and mechs these days, however I have always worked to the straighter the chain (chain wheel to mech) the more efficiently it'll run and less chance of a jump or break under duress.

the SRAM advice is with the understanding that you're running a well maintained & aligned drive system with indexing etc. spot on.

 

[HLaB]

I usually avoid the extremes but there is no rubbing in the big chain and a bit in the small chainring, so I'm more likely to use the full cassette in the large chainring.

 

[col]

If I needed the smallest chainring, Id use the few cogs on the wheelside of the cassette, same with the biggest chainring, Id use the outer cogs, middle chainring the middles cogs. saves on forcing and rubbing.

 

[screenman]

I always understood that a chain works best working in the straightest lines. In that case I do not use extremes, in fact the only two times I have snapped a chain was when due to lack of attention I was on the extremes.

 

[Deleted member 1258]

When I'm on gears, most of my riding is fixed, I rarely use the big chainring, my Kilmeston has 42/50 on the front and I do most of my riding on the 42, most of the time I need to be riding downhill with a tail wind before I can use a 50 tooth chainring.
My understanding is the same as others, the nearer to straight the chain is the better it is.

 

[Tigerbiten]

I try not to use the bottom 7 gears in my high range due to drag.
But I'll use all the hub gears in my low range.