Hi all, anybody know please if the Shimano 3 speed ratio is the same as the Sturmey Archer? I.e. if using a 42 tooth chainring, then max possible sprocket should be 21 tooth?
Also, is the gearing roughly an increase from DD of 33% and decrease of 26%. I don’t find the Shimano docs that easy to figure out. Thanks.
Chainring to sprocket ratio, Shimano Nexus 3 speed
Re: Chainring to sprocket ratio, Shimano Nexus 3 speed
gear ratios of a Nexus 3s hub are slightly wider spaced than an SA 3s
1. 0.733
2. 1.000
3. 1.364
try using this gear calculator
http://www.gear-calculator.com/?GR=SNI3&KB=46&RZ=19&UF=2185&TF=90&SL=3.5&UN=MPH&GR2=SAAW&KB2=46&RZ2=19&UF2=2185
cheers
1. 0.733
2. 1.000
3. 1.364
try using this gear calculator
http://www.gear-calculator.com/?GR=SNI3&KB=46&RZ=19&UF=2185&TF=90&SL=3.5&UN=MPH&GR2=SAAW&KB2=46&RZ2=19&UF2=2185
cheers
-------------------------------------------------------------------------------
~~~~~~~~~~~~~~~~~~~~~~Brucey~~~~~~~~~~~~~~~~~~~~~~~~
~~~~~~~~~~~~~~~~~~~~~~Brucey~~~~~~~~~~~~~~~~~~~~~~~~
Re: Chainring to sprocket ratio, Shimano Nexus 3 speed
Brucey, thanks, got it. Though near enough to the SA ratios as to make little difference. As they used to say in the dockyard, close enough for government work.
But.... it’s the max sprocket size compared to the chainring that I really want to know.
I’ve got a couple of Nexus 7 hubs geared 38/23 and they are both fine. But this Nexus 3 is a new beast to me.
But.... it’s the max sprocket size compared to the chainring that I really want to know.
I’ve got a couple of Nexus 7 hubs geared 38/23 and they are both fine. But this Nexus 3 is a new beast to me.
Re: Chainring to sprocket ratio, Shimano Nexus 3 speed
https://electricbike-blog.com/2015/11/2 ... h-a-bbs02/ sounds like taking it near the limits, including 32/19.
MJR, mostly pedalling 3-speed roadsters. KL+West Norfolk BUG incl social easy rides http://www.klwnbug.co.uk
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Re: Chainring to sprocket ratio, Shimano Nexus 3 speed
Thanks mjr. Interesting, if a little long winded! Think I’ ll stick with 42/21. This is on a Genesis Day One. Dropping to a 26” wheel.
Re: Chainring to sprocket ratio, Shimano Nexus 3 speed
pioneer wrote:......This is on a Genesis Day One. Dropping to a 26” wheel.
Sounds interesting. Any pics? Further details on what you've done and for what use would be nice to hear too.
Barry
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Cheers
Barry
Cheers
Barry
Re: Chainring to sprocket ratio, Shimano Nexus 3 speed
I don't think you need to worry too much if your input ratio drops a little below 2:1.
I do wonder how well a day-one frameset will work with 26" wheels installed though; if the same tyre section is used with 559 rims as with 622 rims then your BB height will drop about 30mm. I'd ground the pedals very often if the BB was set that low.
cheers
I do wonder how well a day-one frameset will work with 26" wheels installed though; if the same tyre section is used with 559 rims as with 622 rims then your BB height will drop about 30mm. I'd ground the pedals very often if the BB was set that low.
cheers
-------------------------------------------------------------------------------
~~~~~~~~~~~~~~~~~~~~~~Brucey~~~~~~~~~~~~~~~~~~~~~~~~
~~~~~~~~~~~~~~~~~~~~~~Brucey~~~~~~~~~~~~~~~~~~~~~~~~
Re: Chainring to sprocket ratio, Shimano Nexus 3 speed
Brucey wrote:.....if the same tyre section is used with 559 rims as with 622 rims then your BB height will drop about 30mm. I'd ground the pedals very often if the BB was set that low.
cheers
I was assuming wider, which is why I was asking.
--
Cheers
Barry
Cheers
Barry
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Re: Chainring to sprocket ratio, Shimano Nexus 3 speed
I thought a 2:1 chainring-sprocket ratio should not be used because of chain wear
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Re: Chainring to sprocket ratio, Shimano Nexus 3 speed
You've got me intrigued as to why the wheel swap; looking for bigger air volume perhaps? Be interested to hear how it works out.
Apart from the BB drop, the only change to the geometry I can see would be reduction in trail. I've run 24" wheels in a 26" wheel frame in the past and it handled really sweetly with a short (65mm iirc) stem fitted. Think the forks may have been slightly longer than intended as well though, so that will've skewed things a bit!
Remember that you'll effectively reduce the gearing slightly when you reduce the wheelsize, although I've just looked at my girlfriend's Day-One and there's clearance for a pretty chunky 26" tyre in there so you might not actually reduce the overall diameter all that much...
I'm a trendy consumer. Just look at my wobbly using hovercraft full of eels.
Apart from the BB drop, the only change to the geometry I can see would be reduction in trail. I've run 24" wheels in a 26" wheel frame in the past and it handled really sweetly with a short (65mm iirc) stem fitted. Think the forks may have been slightly longer than intended as well though, so that will've skewed things a bit!
Remember that you'll effectively reduce the gearing slightly when you reduce the wheelsize, although I've just looked at my girlfriend's Day-One and there's clearance for a pretty chunky 26" tyre in there so you might not actually reduce the overall diameter all that much...
I'm a trendy consumer. Just look at my wobbly using hovercraft full of eels.