Upgrading the Drivetrain on a 20" Gary Fisher Precaliber, lower height seatposts
I got my 4 year old daughter a used 20" GF Precaliber at a local bike swap last summer in knowing it was way too big for her at the time. She is tall for her age, and now is able to ride it around the neighborhood and on paved trails. She uses her 16" Spawn Cycles Banshee for any dirt riding. But she really likes to ride the 20", because I assume it makes her feel bigger, and she likes having gears. I figure it is good for her to figure out gears at an early age, and where we live it is very hilly, so why not try now (on paved trails).
But the 6 speed gripshift is way too stiff for her hands. She can shift it, but quickly complains about tired hands. So I would like to put on a trigger shift onto it, to make it easier for her. And while I am at it, why not upgrade the drivertrain with some better parts. So Am I able to put on a 8 speed system without changing anything on the rear hub? I don't mind changing the chain, cassette, rear derailleur and shifter, but would rather leave the rear wheel alone.
Also, are there any seatposts that have a lower profile clamping system? If I could drop the seat another 1/2" or so, it would make it much safer for her when she comes to a stop. Having fun is important, but being safe is paramount.
And how about any rigid forks that have v-brake mounts? That Suntour fork on there now is a POS, and it's 1/2" of travel can't be budged by a 45 pounder, so might as well lighten the bike up.
Thanks for any info - BS
The bike most likely has a free cassette instead of a free hub. You're pretty much limited to that gearing unless you build a new wheel that can take modern cassettes with more gears. There are better trigger shifters available for 7-8 speeds. In know they work on my son's 7spd tourney RD. Not sure it they work for 6. Maybe an indexed thumb shifter? I used one of those on our trail-a-bike to replace the 6spd grip shift.
There are some BMX seatposts that are integrated with the seats for next to no clamping height.
You may be able to find some trials bike forks that will only raise the front a bit.
To go up to 8-speed freewheel, you will have to add 5mm of spacers to the drive side axel and then re-center the axel cones and wheel dish because 8s freewheel is 5mm wider than 6/7s hub width. Probably simplist change would be to replace the 6-speed freewheel with a 7-speed freewheel (Very close to same width) so you can use with any other 7-speed shifter you want without changing axle spacing. With just couple of unusual exceptions, most all shimano rear deraillers are compatible with different shimano shifters, just need to match the shifter to the # of cogs used. 8-speed cog spacing is not identical but is close enought to get working with a 7-speed freewheel, you just have one "dead" click on the shifter.
Good source of research/info on upgrade paths at;
Traditional Thread-on Freewheels
I have the 20" Precaliber. I replaced the wheels with Velocity Aeroheats laced to old 8 speed XT hubs that I had. I put on an 8 speed trigger shifter and XT derailleur.
The stock crankset weighs a ton. I installed Sinz Cranks with a Salsa chainring, bash ring and N Gear Jumpstop on the inside.
XT Vee brakes, Ringle' seatpost and I swapped the factory fork with a RST Capa 20. Not a huge improvement but an improvement.
Monkey Lite handlebars and some Specialized grip that I shortened to fit his hands. Bike ended up working great for the two years he rode it. Now he's on a 24" I gave the same treatment.
My kid's HotRock 20 comes with the 6 spd Shimano twist shifter. It's extremely easy to twist and the numerical gear indicator is great for my kid ("put it in gear 2 for this next hill", etc.).
Stupid question, but have you already replaced the shifter cable and housing? I've seen the Shimano Revo shifters online for $9 so it's pretty cheap to try one. I'm still considering building a custom wheel and upgrading the drivetrain to get a bigger gear range but just sticking with the stock setup for now.
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