Mountain Bike Reviews Forum banner

New Scott Spark JR 20" Modifications?

47K views 111 replies 29 participants last post by  thchen 
#1 ·
I just bought my 8 year old daughter a 20" Scott Spark for a good price at a LBS.

It is a really great bike as it is, however, I am interested in lightening it a bit and making it more user friendly without breaking the bank.

I have read the other thread about the 20" Scott build and liked the 2 inch riser handle bars, since the stock ones are real low.

The bike weighs the same as her Huffy 20" or less.

The gearing seems to be low enough for her to go up hills, but I am not sure if she will need that big outer chain ring?

What are some options for riser handle bars, stem, wheels, tires, and possibly shifters?

This bike will be passed on to my 4 year old son, so I do not mind spending money on it, especially replacing parts that wear out.

Thanks
Bill
 

Attachments

See less See more
1
#4 ·
If you want to drop weight, check the tires. I was able to drop 1 lb just by swapping out the stock tires. You will also find the cranks and BB to be on the heavy side. Good luck. We're heading up to MT. Laguna on Sunday if you want to give it a run.
Thanks! We are planning to go to Mt. Laguna in two weeks to camp and will ride the trails, thanks.
2) if the seat height is already lower than the bars you may want to go with a flat bar instead of a riser.
Her seat is a little lower than her handle bars, however she is used to them being a little higher.
3) Replacing the wheels is the best way to knock off some weight, but it will cost you. I purchased a set of 28-hole hubs and SunRingle rims on eBay and had them built by a local shop. This saved considerable weight, but I also had to buy a 9 speed cassette, new rear derr. and a set of new shifters. Works way better, but cost lots.
That is good to know, both what is possible and that it is expensive.

This bike is perfect for where my daughter is as far as riding skill, height, strength, etc. I was planning on waiting for a 24" diameter wheeled bike, but she would not be ready for that for at least a year. Even with this bike she is slowly getting used to shifting gears and the handle brakes. I will pass it on to my son, so I feel justified buying the bike.

Thanks
Bill
 
#3 ·
Couple of suggestions:

1) replace the bottom bracket, that will save some weight.
2) handlebars - any riser bar will work you'll just have to cut it down. Two things to consider: 1) be sure to buy a bar that works with the existing stem (that is if you're going to keep the stem); and 2) if the seat height is already lower than the bars you may want to go with a flat bar instead of a riser, adding a riser bar that increases the bar height will make the bike feel too "chopper" like. I used a FSA XC190 riser bar for my son's bike, it's alloy (so it was cheaper than carbon) and was easy to cut down, and its relatively light.

3) Replacing the wheels is the best way to knock off some weight, but it will cost you. I purchased a set of 28-hole hubs and SunRingle rims on eBay and had them built by a local shop. This saved considerable weight, but I also had to buy a 9 speed cassette, new rear derr. and a set of new shifters. Works way better, but cost lots.
 
#61 ·
BB Suggestions



I got from Scott that the stock set up for the bottom bracket is: Frame 68 and BB 116 so what are my options regarding an upgraded and lighter square taper BB? I seen in your post where you have suggested lightening up in this area. I've already re-laced the front wheel to an XT hub, 2012 deore v-brakes, carbon ct-2 seat post, bontrager race light handlebar, Avid single digit 5 brake levers and thinking about re-lacing the rear but may just convert the axle to a QR instead. Thanks for the ideas and keep em' coming cause my little man is in love with this ride. 2011 Scott Spark Jr.
 
#5 ·
Bill, I spent about $550 on a new custom built wheelset for my son's bike, which is crazy expensive for a 20" wheelset, but that price also included a new Sram 990 cassette, x-9 sort cage rear derr, and x-7 shifters. I built the bike for my 9 yr old, he's average hgt, and some might say I should have put him on a 24" bike, but since he likes to jump a lot he's better off on the smaller 20" wheels. The small wheels gives him more control over the bike, and boosts his confidence. Hopefully I can at least 2 -3 years out of it before he's ready for a bigger bike. Either way the parts can transfer over to a new bike pretty easily.
 
#6 ·
Thanks, I got your PM too. That really helps me out. Did you build the wheelset for better performance and/or weight reduction? I would spend that kinda money to make my daughter's bike better, if I know she is going to use it. My goal is to spend more time with my daughter doing stuff we both enjoy.
Thanks
Bill
 
#10 ·
I used cranks from bikesmithdesign.com, he recommends much shorter than that, I believe he said 10% of height plus 5mm, max length on the cranks. Anyways, if you look at a serious kid specific bike manufacturer like islabikes.co.uk then you'll see their 20" models have cranks from 114-127mm max.
I downsized the stock 152mm cranks on my son's 24" bike to 137mm and have been really pleased with the outcome.
I got the race face bash guard on race face rings. The crankset looks awesome and he delivered it fast too! Well worth it, imo.

Correction: he said 10% +5 mm at most.
 
#13 ·
Great info, thanks!! I was meaning to also ask, if I get the Schwalbe Mow Joes, I would get the 20 by 2 inches wide for the stock wheels and if I upgrade my wheels those tires should fit on say a sun envy lite, right?

Seems like the Mow Joes are not carried by many places? What are some good lightweight inner tubes?
Thanks
Bill
 
#16 ·
I cut about 2.5 pounds by exchaning the spark with a scale. I did this a few days after I bought the spark. The LBS has great customer service!!

I let my daughter ride the bike around for the last month or so and decided what else I wanted to do.

I recently bought an IRD 13-32 freewheel in place of the Shimano 14-28. I cut off the big outer chainring that my daughter will never use. I bought a Paul Compents chain keeper, purple handle grips and a Shimano Trigger Shifter.

My daughter likes the improvements and it seems to help her confidence.

Thanks again all for the help!!!
Bill
 

Attachments

#20 ·
I got a fusion x air shock from the manufacturer. Big differences in adjustability. Had cranks cut down to 130. I also am getting a new wheelset built up. Stock they weigh 28 pounds with pedals. My goal is to get it sub 25.
Great score getting the X-Fushion air shock. So nice having adjustable rebound damping so the rear end isn't a pogo stick. With this shock on the Spark its the best rear suspension you will find on a kids bike - works awesome.
 
#26 ·
What a difference

So I live in the mountains of NC and wanted my son to join me on some great rides. At this point, I am done. He has:
127mm custom cut Truvativ triple crankset from BikeSmith. In hindsight, I think 135 or so might have been better to give him room togrow. If anyone wants to buy these from me PM me.
X9 hubs with Velocity Aeroheat rims. Expensive upgrade ( I did find a bargain on the parts) but the way I look at it, when he outgrows this, I will relace the hubs with 24" rims and ebay the 20" rims.
Air shock from Xfusion _ I just called the company and spoke with someone who sold the air shock to me. Worth the money
34-tooth cassette in back - there is little flat here
New platform pedals - no grip on the plastic ones

So - in all I spent a fair amount of money, but less than what I will spend on a new wheelset for me. I figure for 2+ years of use, plus the possibility of extending the use of hubs even longer, it is worth it to me.
 

Attachments

#28 ·
Just picked one up for my 8 yo (he's a little small). Ive been holding off on upgrading his Performance Burnout. I plan to build some disc wheels, but I know that the rear would need a disc adaptor. I also plan on replacing the rear shifter and cassette (8sp). Disc brakes, better tires, and a riser bar. Lots of good info in this thread and elsewhere, but a few questions I have still are:
1. anyone find a good rear disc brake adaptor?
2. What are the rear shock dimensions, and how much do they cost?
Thanks for any help!:thumbsup:
 
#30 ·
I'm slowly losing my mind on my son's Scale Jr 20. I hit the Trexlertown swap a few weeks back looking for bits, and I'm getting ready to build up a new set of wheels. What'd I find?

Inexpensive 31.8 Bontrager bars and stem, new grips.
XTR V-brakes and levers.
X.0 rear derailleur, medium cage, and X.9 trigger shifter.
140mm Sinz cranks with 34t ring.
Syncros Ti seatpost.
Nokon derailleur cables ($6!!! haha.)
XTR M950 non-disc hubs, which'll get built to a new set of rims.

Ditched the stock tires in favor of Kenda Small Block 8s which lost an /amazing/ amount of weight. I'm hoping to get this bike under 20lbs once finished... going to be running 1x9, which should be MORE than enough. Too much fun.
 
#31 ·
Awesome Sashae. I've been geeking out on parts for building up my son's Spark JR 20 - plan is to give it to him as a Christmas present.
* I've identified some older 32-spoke disc hubs I have in my garage, and I plan to build them up with the stock rims
* I found the answer to my previous question about a rear disc adaptor and bought an A2Z DM-UNI adaptor from eBay. Also picked up some used F&R Elixir CR brakes (no discs) from eBay for $100. I've got extra (used) 160mm discs, but I might splurge for some 140mm ones.
* I plan to get some Small Block 8 tires
* I'll be pulling an 8-speed cassette and SRAM Rocket trigger shifter from my dirt-jump bike and plan to put it on this one - I might use the front chainguide as well.
* Next is the front crank/ring. I'm thinking Sinz 40mm from eBay, 32 ring, and re-using an old square taper BB that I should have in my garage (ps - anyone know the width? I'm guessing 68mm...)
 
#34 ·
I got it from them a year ago, and guy (John) said it was the last one they had around the office and they are not making them. Nice shock, real rebound with wide range. I wish they did not have that stupid Manitou eyelet size, as I can't use needle bearing shock mounts. Stock ones are quite sticky - especially for a light rider.
 
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.
Top