ubringliten

Hi,

My wife has a mini velo from Biria and the powertrain on her bike is functionally awful. It already went into the shop for 2 re-alignments and the gear shifting is rather slow.

I want to change everything on her bike from the derailleurs to the cassette to the crankset. Can you recommend? I am assuming what fits on a regular sized bike can fit on a 20" tire bike, but I am wondering if there's a better custom kit made specifically for a mini velo. Lightness is a bonus, because the bike also act as her road bike.

Thanks in advance,

Chris

jur

The only smallwheel-specific kit is the Capreo.

fietsbob

Sturmey Archer 8 speed IGH. as all 7 gears are Overdrive the 20/23/25t cog and what your 1 chainring is are the Low.

then no Derailleurs at all are needed ( Maybe not even a Chaintensioner )

Internal gear hubs are simple to shift as they are all in sequence. No ratio pattern to figure out which one is next


these?
https://www.biria.com/bicycle/mini-20/20-road-bike

Though with a 20" wheel A Rohloff is also Good .. i'm Using a 16:53 drive train on my Bike Friday

they make a 15 and a 13 tooth too..

Omiak

If the components she has are the same as the ones listed on the Biria website it is likely that the problem is either the adjustment of the derailleurs and shifters or a problem of shifting technique.

dynaryder

Only things you have to watch for are rear derailleur length and gearing. Many long cage rear derailleurs hang down pretty far on a small wheel bike;a lady who's brought her Dahon Helios to my clinic several times has banged up the rear derailleur because of this. Small wheels also require the gearing stepped up,so you're better off with larger road chainrings up front than MTB ones.

Also,as Omiak mentioned,the cause may be due to improper setup or user error. Biria's site shows a SRAM X5 drivetrain,which while not pimp is certainly not crap. What exactly is it doing/not doing that isn't right?

fietsbob

Get to where the Bike shop has that dropout hanger alignment tool ... always a good step 1, get the foundation squared away.

ubringliten

Thanks guys. You guys could be right about user's errors.

Her bike is a 2012 model (got it brand new a few months ago) which has this 'microSHIFT' front derailleur and SRAM X-7 rear derailleur. Is microSHIFT any good because the chain hits the front derailleur alot? I noticed the rear cassette wobbles with the wheels and could this contribute to the problem?

dynaryder

MicroShift makes decent stuff;not pimp,but not junk. When you say the chain hits the der,exactly how? Does the chain rub the sides,or does it hit the bottom of the der's rear curve? If the former,it could just be she's not trimming the der properly. The front shifter has more clicks than chainrings so you can 'micro-adjust' the position of the der cage to prevent rubbing in certain gear combos. If the latter,then the front der could be too low,or positioned at the wrong angle(there's another thread going on now where a poster is having this issue on his custom build).

Many cassettes have some float to them,it's usually not a big deal. It is possible the cassette needs to be tightened,have the shop check it.