Crankset/Chainring advice please

10 comments

Gkam84, February 4, 2013

Hello there folks,

I'm normally the one that's giving others advice, so if you all want to chip in, fire away.

So the trike came with a triple and its a 30/39/52 but I need some more range, its a 9/32 10 speed on the rear, but on the flat I'm spinning out the 52/9

So I'm looking at replacing a couple of the rings, maybe set it up as a 30/42/55 but having trouble finding the rings to go with my crankset.

Its a SRAM Truvativ Elita, here's the link to the "manual"

http://cdn.sram.com/cdn/farfuture/EHj107okLLfBSPXS9vasz1e3rQc-URzFQkv6s8...

So what am I going to do?

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don't be mental if you have 20" wheels and can get to 110 rpm average you will be going 41.2 mph

posted by SammyG [233 posts] 4th February 2013 - 22:57

Even with over 12 foot of chain?

Normal calculations do not work with recumbents

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posted by Gkam84 [6662 posts] 4th February 2013 - 23:14

Ah sorry 37.796 @ 110rpm on a recumbent

posted by SammyG [233 posts] 4th February 2013 - 23:21

How are you getting that figure? I'm spinning through the 52/9 around 30mph if I'm lucky.

I'm used to a ratio around 125 inches.

I don't know if that figures into anything, but that's what I get from using online ratio calculators....

Putting all the figures into here http://sheldonbrown.com/gears/

My MPH is about right, 31.7 at 100rpm....

I don't know how this is all worked out. But I know I don't have enough gears

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posted by Gkam84 [6662 posts] 4th February 2013 - 23:58

http://www.recumbents.com/wisil/gearinches.asp if you have a wheel diameter of 20 inches, 52teeth front, 9 back you will have 115 gear inches.

Cadence, speed:

60 - 21
70 - 24.2
80 - 27.3
90 - 31
100 - 34
110 - 37.7

posted by SammyG [233 posts] 5th February 2013 - 10:06

what are they 130 / 74 BCD ????

http://www.spacycles.co.uk/products.php?plid=m2b34s113p1732

still on the 3rd switch-back of Bwlch !

posted by therevokid [454 posts] 5th February 2013 - 10:46

You will probably need a new front derailleur to cope with the bigger difference in teeth between the big and middle rings.

Ah! Condor

posted by Bedfordshire Clanger [222 posts] 5th February 2013 - 11:16

I think those measurements are for a 451 20 inch wheel SammyG, Mine are 406

Thanks revo, they are 130's

Clanger, I wont need a new deraillieur, just move it slightly up the post, plenty of room to do it Wink

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posted by Gkam84 [6662 posts] 5th February 2013 - 12:56

Does your front mech not have a limit to the difference in number of teeth that it can handle? You are proposing a change from 22 to 25.

Ah! Condor

posted by Bedfordshire Clanger [222 posts] 5th February 2013 - 22:31

Not that I'm aware, when I had it in the LBS to have the shifter replaced, I spoke to them and they said I can just move it up the post slightly.

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posted by Gkam84 [6662 posts] 5th February 2013 - 22:36

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