Change rear wheel size on a terra trike
10-21-21, 04:41 PM
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Change rear wheel size on a terra trike
Would there need to be a chain length adjustment to go to a larger wheel size on the rear single? Thanks
10-21-21, 05:08 PM
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The chain length would be dependent on the position of the hub in the dropout. With some fudge factor with the rear derailleur. Also dependent on chainring and rear sprocket sizes.
Simply changing the wheel size, assuming it fits, shouldn't impact the chain.
One general rule, never use a well used chain with a new rear cassette/freewheel.
10-21-21, 06:22 PM
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Thanks. I never knew that about a worn chain/ new cassette. The bike I’m looking at has the gears in the hub. I like the aspect of the taller wheel in the rear.
10-21-21, 06:35 PM
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A larger drive wheel will cause the gearing to be higher. That may be good or it may be bad. If nothing else changes except the rim/tire, then the chain doesn't know the difference. Per CliffordK, the chain and gears wear out together. Measure the chain and if it's more than 1% or 1/8" over; (that is, a 12" section of chain should measure exactly 12" when the chain is new,) you should change everything at once - rear gear, chainring, and chain. Otherwise, a worn gear will cause the next chain to rapidly wear out.
10-21-21, 09:20 PM
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What model (and year if buying used) Terratrike? It's not the chain length that could be a problem since it will not change if you use the same rear gear as on the smaller wheel. What may be a problem is the clearance between the seat and the tire. Way back when Utah Trikes was a TT dealer, they offered a frame extension kit for some of the 20" drive TT models so you could switch to a 26" drive wheel. They quit being a dealer so no longer offer the retrofit parts. You might be smarter to look for a trike that comes with a larger wheel rather than modify one that wasn't built that way. That way you know it was designed for the larger wheel and the handling may be better than if you cobble together a retrofit.
10-22-21, 10:18 AM
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It depends on the model. My Terratrike Tour II needed extension on the drop outs, and a longer chain was needed. Some models can move from a 20" to a 26" without extensions, so the chain would be the same length.
When I put the 26" wheel on my Tour II it raised the seat about an inch, and lowered the bottom bracket about an inch also. I especially liked the lower bottom bracket since my knees are not flashing so high in my face as I pedal. However the main reason for me to go to the 26" rear was to get the chain and RD further up out of the trash and dirt. BTW I changed the gearing both front and rear.
When I put the 26" wheel on my Tour II it raised the seat about an inch, and lowered the bottom bracket about an inch also. I especially liked the lower bottom bracket since my knees are not flashing so high in my face as I pedal. However the main reason for me to go to the 26" rear was to get the chain and RD further up out of the trash and dirt. BTW I changed the gearing both front and rear.
10-22-21, 06:36 PM
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Good point. If you move the rear axle back further, you'll need more chain to reach there and back.
