Fixie/SS Gearing Question...

StuInTokyo

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When I changed to the smaller diameter 26" wheels on my Mixer 8 I have found that my gearing has changed also, I can push a bigger gear now, I have already geared the bike down a lot, stock it is 39T x 18T I'm running 39T x 23T. I seem to remember someone, (Tim S ?) saying that for Fixie or Single Speed you should have one odd and one even number for your chainring cog set up, something about chainwear etc. Is that right?

I have a 22T rear cog on hand, so I could easily swap it out and then run a 39T x 22T set up, this would not affect the gearing much, might put me right back to where I was with the 700C tyres verses the 26" tyres I have now.

So is that they way to go, one odd number of teeth and one even number of teeth?

Cheers!
 

kiwisimon

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You're good with two prime numbers on both ends. Maximises chain and sproket life, but it isn't worth worrying about on a SS used for deliveries. Fixies with skid stopping the combinations are more critical.
just realised 39 isn't a prime number but the rest applies.
 

GSAstuto

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Remember - he has an internal gear hub. So going with a prime number chainring or sprocket is good to keep the chain wear more even. You can quickly check with 'RABBIT'.

But also bear in mind a chain wears on the side and the face -- so:

1) choosing odd-odd combos as a first choice will reduce the side wear of the chain.

2) For face wear - you need to look at the number of links and the number of teeth of front chainring. Reduce the numbers to their PRIME x MULTIPLIER. Now compare all the numbers - if none of them are the same - that's perfect! The front chainring will 'see' the most number of chain faces in a random pattern.

You're good with two prime numbers on both ends. Maximises chain and sproket life, but it isn't worth worrying about on a SS used for deliveries. Fixies with skid stopping the combinations are more critical.
just realised 39 isn't a prime number but the rest applies.
 

eimaiosatanas

Speeding Up
Dec 17, 2011
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But also bear in mind a chain wears on the side and the face -- so:

1) choosing odd-odd combos as a first choice will reduce the side wear of the chain.

2) For face wear - you need to look at the number of links and the number of teeth of front chainring. Reduce the numbers to their PRIME x MULTIPLIER. Now compare all the numbers - if none of them are the same - that's perfect! The front chainring will 'see' the most number of chain faces in a random pattern.
*Head explodes* :eek:
...You guys are really a pool of knowledge regarding bicycles
 

StuInTokyo

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Dec 3, 2010
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Remember - he has an internal gear hub. So going with a prime number chainring or sprocket is good to keep the chain wear more even. You can quickly check with 'RABBIT'.

But also bear in mind a chain wears on the side and the face -- so:

1) choosing odd-odd combos as a first choice will reduce the side wear of the chain.

2) For face wear - you need to look at the number of links and the number of teeth of front chainring. Reduce the numbers to their PRIME x MULTIPLIER. Now compare all the numbers - if none of them are the same - that's perfect! The front chainring will 'see' the most number of chain faces in a random pattern.
Ummmm.... so is that a yes or a no to my question...? :confused:
 

GSAstuto

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Exactly - and as 23, 13, 3 are all dissimilar - the funkalrithm says that you will have minimal 'same hit's on your chain face and link sides.

39 = 13 x 3
23 = prime

Since no prime factors are in common, per Tim's explanation it's good.
 

StuInTokyo

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Dec 3, 2010
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OK, Tim you say the "Number of links" on the chain, does this mean the space between the pins that the teeth of the cog or chain wheel go into, or the number of pin on the chain?

View attachment 1013

So which is it, 95 links or 96 pins?

23T cog
39T chain wheel
95 links

23= Prime Number

39=13 x 3 Prime Factors

95= 19 x 5 Prime Factors

So I guess this is good!

If I went to the 22T cog, then it would be;

22= 11 x 2 Prime Factors

39=13 x 3 Prime Factors

95= 19 x 5 Prime Factors

Which would also be good (Thanks to Joe for catching my mistake!!)

Cheers!
 

GSAstuto

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Links, not pins! And yes - since both your chainring and cog contain the same number - not the ultimate combo. But not bad 4 out of 6 points covered.
 

joewein

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So I guess this is good, if I went to the 22T cog, then it would be;

22= 11 x 2 Prime Factors

39=11 x 3 Prime Factors

95= 19 x 5 Prime Factors

As the chainwheel and the cog both have a prime factor of 11 this would not be good.....Right?
But they don't because 39 = 13x3, so this is also good.