Same Ratio, Different Chainring/Sprocket Sizes Q

[Jezston]

What is the advantage, if indeed there is any, to riding larger chainring/sprockets with the same ratio as a smaller chainring/sprocket.

For example, I have been led to believe that there are advantages to riding, say 48/17 rather than 42/15 (or even 36/13?), which give roughly the same ratios.

Can anyone explain why? I'd have thought there would at least be weight advantages to a smaller pair.

 

[mickle]

Less load on the chain and each of the surfaces it comes into contact with.

 

[Jezston]

Less load on the chain and each of the surfaces it comes into contact with.

What effect does this have?

 

[MacB]

I don't know if there's any actual efficiency difference, one would imagine it's tiny if it exists. But all the parts should wear more slowly and I suppose a greater number of teeth engaged could mean less chance of shipping a chain.

 

[gaz]

Some people will look for a ratio that allows them to skid with lots of potential contact patches on the rear tyre.
A particular ratio may give you 3 contact patches when your leading foot is in a comfortable position for skiding, where as another ratio will give you 11.
Obviously this only applies to fixed gear and those who want to skid.

 

[smutchin]

Some people will look for a ratio that allows them to skid with lots of potential contact patches on the rear tyre.
A particular ratio may give you 3 contact patches when your leading foot is in a comfortable position for skiding, where as another ratio will give you 11.
Obviously this only applies to fixed gear and those who want to skid.

That's interesting. Though apparently larger sprockets/chainrings don't necessarily give more skid patches. I plugged the figures into the rabbit gear calculator and it tells me 48x17 gives 17 skid patches while 42x15 gives five skid patches, but 36x13 gives 13 skid patches.

Personally, I prefer to use brakes anyway.

http://software.bareknucklebrigade.com/rabbit.applet.html

d.

 

[Theseus]

A bigger chainring gives the impression you are pushing a huge gear, thus gaining pseudo man points and earning the respect of lesser cyclists.

 

[Jezston]

Thanks for the info everyone! The applet linked too above is particularly interesting along with it's links to SB. I also now know how the whole skid patch thing works, which may go some way to explaining the massive raw patch on my rear tyre! (Note - Conti 4 Seasons are NOT skid friendly).

So is there an ideal 'sweet spot'? Above 48/17 are contact advantages lost? For example, any benefit of going up to 54/19 and above?

 

[totallyfixed]

A bit less wear on the sprocket if you use more teeth, it's why I ride 50x18. Scrub that, Touche has it right.

 

[smutchin]

So is there an ideal 'sweet spot'? Above 48/17 are contact advantages lost? For example, any benefit of going up to 54/19 and above?

The obvious disadvantage I can think of with a very large chainring/sprocket combination is that you'll need a much longer chain. Don't know how much that really matters for practical purposes.

d.

 

[Deleted member 1258]

A bigger chainring gives the impression you are pushing a huge gear, thus gaining pseudo man points and earning the respect of lesser cyclists.

Are thats where I'm going wrong, I need to ditch my puny 44X18 65 inch gear and fit something that makes it look like I'm pulling the 98 inch gear my mate is.

 

[fossyant]

Skid patches ? - get off here and join LFGSS

 

[brockers]

A bigger chainring gives the impression you are pushing a huge gear, thus gaining pseudo man points and earning the respect of lesser cyclists.

I think that sums it up tbh.

 

[Jezston]

So what is the ideal chainring/sprocket combination for an approx. 2.8:1 ratio?

 

[Noodley]

I'd have thought there would at least be weight advantages to a smaller pair.

snarf