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PostPosted: Mon Jul 01, 2013 6:51 pm 
Gold Trader / PoTM Winner / RB Rider
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Location: 54 Festive Road Winchcombe GLOUCS Yarp...
This is not strictly and MTB or Road question but applies to both.

I have two interchangeable front cranks one 49T and one 48T given that the bike is a 5 speed 12-28 does the one less tooth make that much difference across the range or just on the climb or not? Anyway have fitted the 48.

can someone enlighten me?

Sticking this in the road section as well to see who is the most helpful and or articulate. :mrgreen:


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PostPosted: Mon Jul 01, 2013 7:09 pm 
Old School Hero

Joined: Sun Apr 28, 2013 8:56 pm
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Location: Flipping between Wigan and Lincoln
Being as I'm primarily an off-road person (I do road bikes too but to a lesser degree), I'll reply here ;)

If you work the percentages the difference there is less than 2%... I would say it'd make very little difference unless you're a pro-level rider (in which case you might notice a difference in your cadence) you'd get 2 gear-inches of difference on the 12-tooth, less than one on the 28.

Dropping from 12 to 11 on the back would make more of a difference (as would moving from 28 to 29 on the other end of the cassette if 29's are available) as the percentage difference is much larger.


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PostPosted: Mon Jul 01, 2013 7:15 pm 
Gold Trader / PoTM Winner / RB Rider
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Congratulations. And thanks. That was the most useful answer and one that I could understand!


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PostPosted: Mon Jul 01, 2013 7:20 pm 
rBoTM Winner
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It really depends on weather it is a front tooth or a molar...


...but to the question: one tooth on a relatively large chain ring like a 49 will make little noticeable difference. If you look at a gear chart (for 27 inch wheels) it changes the ratio by only two gear inches where as if you change the rear cog from 12t to 11t it changes the gearing by 10 gear inches. (Attached is a gear chart for refernece, although it is a tad hard to read.


Attachments:
gear chart.gif
gear chart.gif [ 29.99 KiB | Viewed 453 times ]


Last edited by lewisfoto on Mon Jul 01, 2013 7:31 pm, edited 1 time in total.
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PostPosted: Mon Jul 01, 2013 7:29 pm 
Gold Trader / PoTM Winner / RB Rider
Gold Trader / PoTM Winner / RB Rider
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Joined: Tue Feb 26, 2013 6:26 pm
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Location: 54 Festive Road Winchcombe GLOUCS Yarp...
Thanks. Good job I've got my reading glasses on!


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PostPosted: Mon Jul 01, 2013 8:53 pm 
retrobike rider
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Location: where having straight teeth in your mouth is more important than the words that come out of it
Dunno mate...


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Shane_Macgowan_With_Teeth.jpeg
Shane_Macgowan_With_Teeth.jpeg [ 38.16 KiB | Viewed 411 times ]
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37.jpeg [ 264.4 KiB | Viewed 411 times ]
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PostPosted: Mon Jul 01, 2013 9:10 pm 
Retro Guru
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Rather than the table I use Sheldon browns site. Top stuff.

http://sheldonbrown.com/gears/


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PostPosted: Mon Jul 01, 2013 9:14 pm 
Gold Trader / PoTM Winner / RB Rider
Gold Trader / PoTM Winner / RB Rider
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Location: 54 Festive Road Winchcombe GLOUCS Yarp...
Yes been there. Sounds like it will make a little difference. Can you get twin ringed cottered sets?


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PostPosted: Mon Jul 01, 2013 10:10 pm 
rBoTM Winner
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Yes you can get double ring chainsets for cottered cranks. Stronglight and Magastroni were the two big names in the 50s but there were many others.


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PostPosted: Mon Jul 01, 2013 10:19 pm 
Gold Trader / PoTM Winner / RB Rider
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Joined: Tue Feb 26, 2013 6:26 pm
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Location: 54 Festive Road Winchcombe GLOUCS Yarp...
thanks will 'keep em peeled' (Shaw Taylor, 1977)


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