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  1. #1
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    Upgrading hand me down GF Precaliber 20" - Functionality improvements/weight savings

    Hello…

    My daughter is loving trail riding She's six, loved Off the Top in Mammoth and we're finding some local trails she just can't wait to get back on. She's riding her sister's old GF Precaliber and will be for at least three more years and this bike could be potentially be moved onto my 3 year old son with a new paint job too. Really would like to lighten it up and make it a lot easier for her to shift as she climbs like a bat out of hell if she can get it in the right gear. Loves going downhill. Never taken a bike a part but willing to try. So need your help in some smart reasonable upgrades. Been searching and think found a few ideas but please chime in…

    Functionality:

    - Sram X4 Trigger Rear Shifter (8 Speed)
    - Sram X7 Rear Derailleur (Medium Cage)
    - Shimano CS-HG41 11-34 8 Speed Bike Cassette Mega Range MTB. I don't know if she needs this as she climbs normally in the second ring? Going to be climbing with her older sister and friends so just thought maybe a good idea. But could use stock(?) and spend that money on something to lighten the bike up or upgraded fork?
    Rear hub when it spins is grinding and not very smooth. Swap the hub? Whole wheel?
    Am I missing something or do I need a tool to make this happen?

    Lightening the bike up:

    - Love to get her some lighter wheels as rolling mass but not sure it's smart money?
    - Find some used carbon riser bars (OK to cut down right?)
    - Suggested headset? Carbon?
    - Carbon seat post? Does anyone know what size?
    - Sinz Expert ISIS Crank Arms 135mm
    - Sinz Expert BB
    - Salsa Front Chain Ring 34T
    - Kenda Small Block 8 tires with lightweight BMX tubes (this saved two pounds) Once she destroys the current treads.

    - Always wonder with us going to Mammoth is it smart money to upgrade to disk? My bike's v brakes worked just fine but? Or would it be better money to put it towards lighter cranks or wheels?

    Light set suggestions? We do a lot of riding for frozen yogurt at night and wondering if there's a cheap light set stocking stuffer you guys like? Doesn't have to last more than 30 minutes or so?

    Anything else throw it at me

    Thanks for your help in advance,

    Smkntrls

  2. #2
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    The folding bead schwalbe mow-joes are an even lighter 20" tire;
    Mow Joe HS 371 | Schwalbe North America
    Dont wait until current stock tires are worn out, they likely will outlast your families use of the bike and be a constant source of heavy weight.

    Your current rims are probably as light as you are likely to find for a 20" rim, there are not really appropriate kid-weight rims made, just adult rim extrusions rolled down to smaller size. You might want try try re-building using the existing rims with better hubs and using fewer spokes for weight savings. See my wheel re-build (and a light shock modified as a 20") at thread ; Novara Pixie 20" project

    Disk brakes will make a kids bike heavier compared to V's. I would start with lightening the crank and wheels as you have suggested.

  3. #3
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    Wholly smokes GrayJay your Novara Pixie 20" project is awesome. I'm going to have to pull up a frosty one and sit down for an in depth read. Any thoughts on the Spinner Air 20 Fork? Tearing apart a fork kind of scares me and I definitely don't have the confidence in telling my wife I know what I'm doing ;-) The Spinner is expensive but it will stay with the family for at least six or seven more years. I'm assuming swapping it out won't be too much trouble and I can move it to a different bike if need be. Biggest concern is serviceability and related parts to do so. Any thoughts would be appreciated.

    Any thoughts on the capability of the Mow Joe's on the trails in Mammoth? The first set my oldest wore out so I upgraded the tires to a Specialized Spanky up front and Kenda rear tire that's very beefy/aggressive and I'm sure heavy for the trip to Mammoth. They worked well and she pretty much stops on a dime which is what I was hoping for. The weight I may just live with but get some lightweight BMX tubes.

    Thank you again for sharing,

    Smkntrls

    Anybody have experience swapping cranks on the GFP? What kind of BB would I use. Thank you...

  4. #4
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    1500gr for the air spinner 20" is a lot of weight for a 6-yr old to lug around;
    Spinner Air 20" Fork

    If you don't want to DIY convert a fork to 20" then finding a lightweight rigid fork might be a good alternative and could easily save couple of pounds.

    Pretty sure the GFP would just have a standard british/ISO (Euro in BMX speak) bottom bracket shell. If you are using an ISIS spline crank, then a MTB width ISIS cartridge bottom bracket (with british/ISO threading) should work fine in the frame. The bottom bracket you can use is more dictated by the crank than by the frame.

    See Jordans other recent GFP 20" thread for more on the BB and crank;
    20" Custom Build Project

  5. #5
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    Awesome GrayJay. So I'm sorry to say I didn't get to review your thread on the link above last night but will be tonight. I thought the Spinner would be much lighter than the standard rst and used all it's travel and therefore xxx but now I'm tempted...

    Please let me know what you'd think would be a reasonable to nice upgrade for a fork. My main concern now is adjusting the angles to much on the bike, and serviceability. I don't mind tinkering and learning about how a fork works and improving her ride exponentially. I'd actually like to get into it so I can service the rest of our family's bikes shocks. I've serviced/torn apart my KTM but never the forks/shocks so I'm a little intimidated.

    Is there another thread I should also get into tonight on this that you suggest reading? And thanks for the link to Jordan300 build. Don't know how I missed that one.

    Also is it tough removing the rear cog from the wheel? Any of those upgrades I mentioned you think I should adjust up or down a level? Again this bike will be used for at least six/seven more years.

    Thank you so much and have a great day. PM me if you'd like.

    Smkntrls

  6. #6
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    Hi...

    Took a quick minute to figure out how to measure some things and ran into a couple posts and saw that potentially GrayJay I may not need to do any spacing adjustments with the rear cassette? Did I read that right?

    Also NYrr496 did you swap the rear hub for the XT as a necesity? Do I need to do the same to achieve this build? Was your hub going bad? Mine is starting to grind and maybe I should buy a cheap shimano replacement and have some fun trying to build up a wheel for the kids?

    FYI my goal is to tear this down and build it up in front of about 15 neighborhood kids + parents who are starting to get into MTBing. So any and all feedback will be for the benefit of not just me but for all of them as parents are skeptical about what I'm preaching to them about the fun of the sport and it's positive attributes.

    Also here's some measurements I took of the bike that I think are relevant. Someone please share with me a good tear down/measurement/build thread I'd be happy to read it to learn about what I should have on hand to do so. Anyone please confirm my measurements for accuracy and how to and if it was necessary that would be great. As I certainly don't want to buy the wrong components. Thank you. Smkntrls

    Fork is 1' 10" from top to bottom
    bottom bracket to bottom of fork wheel tabs 1 ' 3"
    8" from the top of the fork crown to the top of the stem where the cap goes

    BB width is 66.675 mm
    Fork stem diameter is 1 1/8 or 28.575

    Seat Post circumference is 1.5" or 38.1 mm

    Stem (from middle of fork tube to middle of the handlebar) is 63.5 mm
    Bar thickness is 79.375 mm
    Bar length is 558.8 mm

  7. #7
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    Sadly, a new, ready to purchase lightweight suspension fork for a 20" bikes simply does not exist. Spinner air or else a White Brothers are probably the best available options but are still overweight for a kids bike. See the the suspension vs rigid discussion at;
    Kids 20inch MTB's

    Viable light option to heavy front suspension might be a lightweight 20" BMX fork without front brake, like the 16 pound marin shown in thread; KTM 20" MTB Build 19.6lbs

    Good new is that the GF frame you have is a great starting point for your kids build.

    Your bike likely has a thread-on freewheel, not a cassette. You will need a shimano freewheel remover tool to get it off. Good plan would be to replace the junky threaded hub with a cassette hub, rebuild the wheel around the new hub. Working on bikes definitely takes a few specialty tools and knowledge that is not always obvious but there is plenty of good info out on the net. Shocks are not terribly hard to service.

  8. #8
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    I replied to your private message but I'll go into more detail here. The hub that came on my son's bike was the freewheel type. I could not swap the cassette on it and I had an XT hub, 8 speed cassette, shifter and derailleur. The hub was 135mm wide. The frame was 130 or 132... Slightly narrower. I did get the hub in but I figured it would be bad for the frame to ride it that way so I had the LBS fool with the axle and the spacers to get it to drop in. I also used Vee brakes since these were not disc hubs. I used old Ringle quick releases that weigh almost nothing.
    I never weighed the bike but it was lighter for sure. Every component I replaced was lighter than the part it replaced.
    Every part adds up.
    I like turtles

  9. #9
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    Oh yeah... I believe the seatpost on those is 27.2
    I like turtles

  10. #10
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    Wait a second this isn't plug and play. What are we dealing with Windows 95

    Thanks GrayJay and NYrr496 (thanks for the measurements and PM reply; I sent a response) for your help. The fork may just have to wait since I'm looking at hub and build. Is it possible to find a good trigger shifter for this bike and not have to go through this trouble? Gears are good for her the shift is just to hard?

    Wow my eyes are wiped from checking out a lot of sweet rides. Thinking I may need to shorten up the stem as she is leaning pretty far forward with this 20" top tube.

    Thanks again guys.

    Smkntrls

  11. #11
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    How many gears does it have now and what kind of derailleur? For my daughters 20", she was unable to twist grip shift but did fine when I switched to an old 6-speed indexed thumb shifter (to match 6-speed freewheel). Shifter was sourced used at local bike coop for cheap.
    A new SRAM derailleur will need a SRAM shifter, ratio is different than shimano derailleurs. I dont know if SRAM ever even made 6-speed shifters (if it now has a 6-speed freewheel?) Might be easier to find shifter that is compatible with the current freewheel tooth count by using a shimano derailleur instead of a SRAM.

  12. #12
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    Hi GrayJay,

    I may have made a mistake when I first bought it years ago and asked the LBS to install a trigger shifter type. It's just to hard to push the big lever on this poorly designed one.

    The trigger shifter is a Tourney which the big lever to get to the taller gears is just impossible to push.
    It's a Shimano Sora six speed.
    The cassette is a Shimano MFT220.

    Is there a way to improve this system? I read one place that you can have a higher geared shifter that will just have a dead shift if it doesn't have the matching cogs, true?

    Interestingly the rear frame measured 133.3 so I'm now real curious about a normal hub slipping in/forcing it just a bit :-)

    There's what looks like disk tabs on the back of this frame. If I go the point of rebuilding the rear wheel is it possible to go disk? I've read how it's easier on long descents to squeeze the disk brake equipped bike. Kind of like that idea.

    Watched that epic 5 part rebuidling thread on you tube and thinking I can manage it. Then set me up to build my own set for my ride down the line...

    Thoughts always appreciated,

    Smkntrls

    Thanks everyone,

    Smkntrls

  13. #13
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    Quote Originally Posted by SMKNTRLS View Post
    Interestingly the rear frame measured 133.3 so I'm now real curious about a normal hub slipping in/forcing it just a bit :-)
    Smkntrls
    Manufacturing tolerances. Just pull the rear stays apart when you put the rear wheel in. I had the same issue with my son's Marin Hidden Canyon.

  14. #14
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    Thanks Stom_m3. Seen a lot of nice bikes over past day. Have you posted your build? Sorry brain's turning to mush looking at all these parts.

    Figure forget the rear disk and brake upgrade and focus on drivetrain. Everybody happy with their Paul's Chain Keeper? Seen some posts with the use of an extra front derailer as a stopper.

    Curious if anybody uses shimano dual controls for their applications? Looks really big and bulky and maybe harder to use?

    Smkntrls

  15. #15
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    Quote Originally Posted by SMKNTRLS View Post
    Thanks Stom_m3. Seen a lot of nice bikes over past day. Have you posted your build? Sorry brain's turning to mush looking at all these parts.

    Figure forget the rear disk and brake upgrade and focus on drivetrain. Everybody happy with their Paul's Chain Keeper? Seen some posts with the use of an extra front derailer as a stopper.

    Curious if anybody uses shimano dual controls for their applications? Looks really big and bulky and maybe harder to use?

    Smkntrls
    Here's my son's 20" build for when he was 6;

    Just bought my 6yr old a Marin Hidden Canyon 20". Going to put XTR on it.

    Here is my son's 24" build that I just did now that he's 9;

    Scott Scale RC Jr w/ mods and weights

    As for the front chain keeper, a Pauls, or N-Gear Jump stop with a BBG bash ring will work. I did combinations of both on the two different builds.

    Let me know if you have any questions.

  16. #16
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    Thumb shifters are pretty easy for kids to use, for example;
    Amazon.com: Shimano SL-TX30 Tourney 6 Speed Shift Levers: Sports & Outdoors

    6 speed freewheel (or cassette) needs a 6-speed specific shifter as the cog spacing is different for each # of gears. 7 and 8 speed are close to same spacing but still not exactly the same. See; Shimergo | CTC and/or Sheldon Brown's Bicycle Frame and Cassette Spacing Crib Sheet

    Switching to disks brakes with new hubs is a possibility but they also add weight. Well setup V-brakes can be plenty strong and are lighter.

  17. #17
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    stom_m3 Awesome build there and love the expressions on your sons face. Well worth the time and money spent. Have to spend a little more time reviewing them and thanks for sharing Have to check out the fork mod and see how that works out for the bike.

    GrayJay Thanks for the links. Yeah I must have the older or crapier version as it's hard for me to move that big thumb one. Pretty much decided go for a complete driveline overhaul for the future years of abuse. V brake overhaul will be next year's presents.

    Curious if someone can help me figure out what stem size I have so I can figure out what stem/handlebar combo I can shop for. I again have measurements above but not sure if I did them right. Also I think I want to shorten the reach but not sure what size would be just right. Saw M-dub went with 35 mm with some rise. How's that working out for him? The current one has a rise to it so probably keep the rise. Anyone know what degree rise I probably have? Looking on ebay Trutive looks pretty nice and reasonably priced. Suggestions would be helpful.

    Also should I be thinking about a new headset? Is it really necessary?

    Thank you,

    Smnktrls

  18. #18
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    I have one of those Ebay Truvative stems on my son's current bike. A little heavy but the price is right.
    The Uno stuff on Ebay is pretty light for the price. I think that's who made his handlebars.
    I like turtles

  19. #19
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    Quote Originally Posted by SMKNTRLS View Post

    Curious if someone can help me figure out what stem size I have so I can figure out what stem/handlebar combo I can shop for. I again have measurements above but not sure if I did them right. Also I think I want to shorten the reach but not sure what size would be just right. Saw M-dub went with 35 mm with some rise. How's that working out for him? The current one has a rise to it so probably keep the rise. Anyone know what degree rise I probably have? Looking on ebay Trutive looks pretty nice and reasonably priced. Suggestions would be helpful.

    Also should I be thinking about a new headset? Is it really necessary?

    Thank you,

    Smnktrls
    Stem, crank length, bar width, seat position, seat height are all fitting type components or settings. Kids are a little more generic in fitting because they are growing so fast. Without knowing your daughter's height and reach but assuming a 6 year old with growing potential, I would look for a 60-75mm stem, 0-6 degree rise, 31.8 handlebar clamp. Usually Jenson's, Pricepoint, or Cambria bike have good sales on previous model stems. Find the cheapest lightest option. Same with the Handlebars. Find an inexpensive 31.8 aluminum or even a previous model carbon fiber bar.

  20. #20
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    NYrr496 and stom_m3 THANK YOU. My response last night was pretty winey Thanks for putting up with it.

    Great Stom_M3 I almost bought the wrong size handlebar. I'm obviously very uniformed on measuring bike components. Love it if someone pointed me to a place where I can become informed. If not I'll look into that next.

    So are the fork tubes from different brands/models that the stem attaches to all one general size for all mtb's?

    Trying to learn as I hope to build my next bike.

    Thanks everyone,

    Smkntrls

  21. #21
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    The steerer tube which you refer to as fork tube is measured via diameter.

    Here is a short list of some measurement items;
    Steerer tube = diameter (typical 1 1/8")
    Seat post = diameter x length
    Stem = Steerer tube diameter, length (C to C), handlebar diameter (typically 31.8 but older use 1")
    Crank length = C to C
    Bottom Bracket = thread type (yours should be Euro 68mm) by length of spindle (108-118mm)
    Seat tube = diameter (for ordering a chain guide)
    Chainring BCD = Diameter (5 bolt = 110bcd, 4 bolt = 104/64bcd)

    Of course there are huge variations and standards but the above will be applicable to your bike.

    If you are buying a new fork, you will need to ensure that you purchase a 1 1/8" steerer fork (of course this assumes your stem and headset match accordingly).

  22. #22
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    Thank you stom_m3.

    Looking at some of the weight savings comparisons people have made and the stem doesn't seem to be such a big difference so I may just hold off on that.

    When you get a second could you please define C to C for me? Is that center of circle to center of circle?

    One of my measurements match's up ;-)

    Smkntrls

  23. #23
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    First purchase:


    EASTON EC70 XC CARBON HANDLEBAR HIGH RISE

    Specifications:

    Brand: EASTON

    Model: EC70 XC

    Length: 685mm

    Rise: 40mm

    Sweep: 5 degree upsweep, 9 degree bend

    Clamp Diameter: 31.8mm

    Material: UD Matte Carbon

    Color: Black

    Weight: 159g

    Retail Price: $140.00 (not what I paid though)

    The sweep makes me think of lowriders but hopefully it's to the kids liking

    Thanks everybody. Keep you posted (pun intended)

    Smkntrls

  24. #24
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    SMKNTRLS, I'll take the pics tomorrow and send them out Monday. Sorry, but I can only access my e mail from work or on my blackberry.
    The pics will come out better if I take them with the camera and not the bberry.
    I like turtles

  25. #25
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    NYrr496 no problem my friend and thank you

    I'm kind of waiting for a few things to come through and have moved on to what to do for my older daughter. Probably start a new thread on that one.

    What do you guys think about a bash guard for the 20". Just learning about them and like the fact it will protect their legs from the teeth. Along with maybe stopping inadvertent pants/laces from catching? Suggestions on which one with Sinz Cranks and I think I want a Salsa 34T? Need one with five holes

    On that train of thought (if I have one ) for those of you newbies checking out my thread here I found gold! You all owe me

    Sheldon Brown's Bicycle Glossary Ca--Ce

    And pretty obvious guess ha stom_M3

    Thanks everybody!

    Smkntrls

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