[trikes] Greenspeed GT3 gearing choices.

[Rob Hague]

Yeah, should have said - i am using a 9-30 custom cassette on a Capreo hub but I only have a single front chainring and a mountain drive so I don't need the big take up that Ian suggests you'd need with the 11-30. As far as the efficiency goes, I've got that machine very carefully set up so most of my riding is in the 'efficient' direct drive of the MD.

Oh, and if you are rebuilding a Capreo, unless you have access to clever tech, you have to use the 9t & 10t small bits because the cassette body is stepped only taking the donor 'deore' type parts for, I think, the inner 7 sprockets. 

As Ian says there are a lot of variations and it depends what you are trying to achieve and what your budget is.

Rob


On 17 Oct 2010, at 01:30, Ian Sims wrote:

> Hi Fran,
>        The standard gearing on the GT3 is 52/42/30 on the front, and 9/26 on the rear.
> 
> This gives a range of 20 to 98 inches with the 16 x 1 1/2" rear wheel which has a diameter of 17".
> 
> Or 19 to 95 with the early 16" x 1 3/8" rear tyre which had a diameter of 16.5"
> 
> The 9/26 cassette is a Shimano Capreo cassette, which is made esp. for bikes with small wheels, and will only
> fit a special Capreo hub, or a special hub made to fit the Capreo cassette.
> 
> The Capreo cassette has a number of advantages over the standard hub, as fitted say to the GT1, and many other
> bikes and trikes, on which the smallest cog that can be fitted is a 11t.
> 
> The main one is that it gives a wider gear range, for the number of teeth difference between the largest and
> smallest cog.
> 
> That is it has a 26/9 x 100 = 289% for a 17 tooth difference. Whereas a common 11/28 cassette will only give a
> 28/11 x 100 = 256% for a 17 tooth difference. This is important with a small wheel trike, as to use the full
> range of gears from one extreme to the other, i.e. small to small and large to large one can use a mid cage
> derailleur instead of long cage, if you want to have the chain well clear of the road.
> 
> The 9/26 cassette is the only one currently available for the Capreo hub, thus the easiest way of providing
> lower gears, is to switch the "road" 52/42/30 triple cranks for a "MTB" 44/32/22 crank set, as we do with our
> small frame GT3s.
> 
> This will give you 14 to 83 inches, with a wider overall range of 593%, V 490% for the standard gearing.
> 
> It is also possible to swap out the rear wheel for one with a standard hub which will take say a 11/34
> cassette, but this will require a long cage rear derailleur to use all gear combinations, which could give you
> ground clearance problems on unmade roads, or if you retain the standard mid-cage rear derailleur, you will
> need to remember not to use combinations like small to small, which may allow the chain to drag on the ground,
> or large to large, if the chain is adjusted to tight, when you could damage the rear derailleur.
> 
> It is also possible to change some of the cogs on the Capreo cassette for larger ones to give you lower gears,
> but this has the same disadvantages as the swapping the rear hub, and using a 11/30, 11/32, or 11/34.
> 
> If you were to use a 32 t rear cog with the 52/42/32 crank set, then you lowest gear would only be 
> 17 inches, so in my opinion the easiest way of getting lower gears is the 44/32/22 crankset.
> 
> Yet another way is to change the rear wheel for one with a SRAM DualDrive hub. With an 11/28 cassette, and the
> standard 52/42/30 crankset this would give you much wider gear range of 14 to 107, but no lower than the
> 44/32/22 crankset option.
> 
> Some people have also fitted the German Rohloff 14 speed rear hub and the Schulmpf mountain drive.
> This gives a very wide range of say 9 to 115 inches with our standard 13/60 gearing. However you will suffer a
> small power loss, in the lower gears, of about 10%. For some people this does not matter, whereas others find
> it unacceptable. Thus IMO each rider should carefully consider the options before changing....
> 
> 
> Regards, Ian
> Ian Sims, Director
> Unit5/31 Rushdale Street
> Knoxfield VIC 3180
> AUSTRALIA
> Phone +61 3 9753 3644 
> Fax +61 3 9753 4434 
> Email ian at greenspeed.com.au 
> Web www.greenspeed.com.au
> 
> 
> Message: 1
> Date: Fri, 15 Oct 2010 15:11:11 -0400
> From: mgta4 at aol.com
> Subject: [trikes] Greenspeed GT3
> To: trikes at bikelist.org
> Message-ID: <8CD3AB3DD897DDA-1C74-21D2 at webmail-m100.sysops.aol.com>
> Content-Type: text/plain; charset="us-ascii"
> 
> I would like lower gears on my GT3 and was wondering if the largest cog in the rear could be replaced by a
> larger one without any problems??? Thanks Fran
> 
> 
> 
> 
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