Trek Roscoe 20 - Learnings and Mods- Mtbr.com
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  1. #1
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    Trek Roscoe 20 - Learnings and Mods

    New here. Wanted to share my experience buying, owning and modifying a Trek Roscoe 20 kids + sized bike.

    I had scoured the internets for information on a good beginners MTB and had a few things in mind before discovering the Trek at my LBS. I have three kids and this is for the oldest, so it made sense to me to get something good, and make it great to create the best experience for all three of the kids over the next 9 years. I want them to learn to love cycling with me.

    The hunt was on for a great base to start from. Light frame, and descent build would set up an easy upgrade. I like to tinker and modify everything, so simply buying the best thing I could find was no fun, but the basic ingredients had to be there, and the fit had to be right. My oldest is 6.5 years old, already has great balance and bike handling skills, and needed something to grow with.

    Long story short, after much interweb research I was prepared to order the Cannondale Cujo 20, but found the Trek Roscoe 20 in person at my LBS. I had not seen a thing on this bike on the internets, but after looking at it, having her ride it, two things were obvious. It fit perfectly with room to grow, and it had a build that would allow me to mod it quickly.

    The stock bike can be found online, so look for the specs there. But the big wins are the frame, it's weight, and the wheels/hubs from the factory running disc brakes and an 8 speed. This allowed me to go immediately to 10 speed and upgrade the brakes to something much better without the hassle of having to build a wheel set first thing.

  2. #2
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    First Impressions

    The bike weighed at the LBS was 24.48lbs with nylon pedals. It ran well when my daughter took a test ride. It turns quickly, shifted well enough, and was easy for her to climb on and off. The handlebars might be a little wide, but she will quickly grow into them.

    The brakes stop the bike well, but being mechanical, they lacked feel. More than that, they lacked the ability to adjust the reach of the levers enough. There is an adjustment screw, but it just didn't go as far as my daughter needed. They would be more than acceptable for daily use, but I cant leave well enough alone.

    The 8 speed Tourney derailleur and thumb shifter work well. They were consistent and didn't require too much force to shift. There was some slop, but that was expected at this level, and totally acceptable. For me, the use of the thumb shifter was a HUGE improvement over the grip-shift found on most of these 20" bikes. Another immediate observation was the incredible length of the derailleur cage and just how far it stuck out from the bike. Again, totally serviceable and worthy of riding into the ground.

    The crank is noted as 32T on the website, but mine was a 28T. Two things of note here...the 28 made the gearing wonderfully low when combined with the 11-34, and interestingly, when weighed, it was actually pretty darn lightweight. Less than what I eventually replaced it with by ~100g!

    The hubs and wheels are also nice all things considered. Particularly in the rear where you can swap to a 10 speed without any modification. I have yet to weigh them individually yet, as I have plans to go tubeless eventually. More on that later. But I am sure they weigh a bit with huge 2.8 CST tires, requisite tubes, and budget rims. One thing to note was what might be sloppy spoke build. It looks like some of the spokes are bent and wonky. Nothing seems loose, and the wheels spin true, but they don't look right to my eye. I'm going to guess they could easily withstand anything my daughter can throw at it, but I am committed to swapping them eventually to be sure they are right, and to use in better hubs. Of note, the front wheel appears to be true, but off center by about 10cm. Need to fix that.

    One final note on running gear, the bottom bracket was crunchy from the start. I tried to adjust a bit, and found it to have a major lack of grease, but nothing could make the improvement I was looking for. Due for replacement.

    Overall, for a $500 purchase, it is well composed and ready for some fun adventure directly from the showroom floor. I would HIGHLY reccomend that you go through the bike, loosed the overtightened hardware and running gear, lube and grease where necessary, and put it back together with care and a torque wrench. I can't help but believe these are not being assembled by passionate weathered Italian men like your Pinarello, but instead with power tools in Asia and by ham-fisted mechanics looking for their next break. It's performance and longevity are up to what you do when you first get it home.

  3. #3
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    Modifications

    Objective - make it lighter, more durable, and fun/easy to use.

    First to go were the brakes. I swapped with Shimano BR-M396. They were super easy to install, have much better feel, and have fairly significant reach adjustment. They come preassembled so they require you to shorten the tubing, but have the parts needed in the box. You just need mineral oil. Immediate and significant improvement.

    Next was swapping the rear cassette to a Shimano 10 speed 11-36. Pick up a couple extra teeth on the far end, and more importantly, a couple more cogs to even out the jump from gear to gear. This was also easy as going from 8 to 10 speeds requires no change to the rear hub.

    This required a new derailleur and thumb shifter. For the shifter I splurged the $45 to use an XT version, opting for the metal components and smoother action. It's well worth it. And on the far end, I swapped with the Shimano Zee short cage, also $45. This is Shimano's budget downhill derailleur, but it has an incredibly short cage, is tucked into the frame, both making it less likely to be hit and damaged. And it has a clutch as well! Win win win. Combined with the XT shifter, it runs through all gears quickly and efficiently. One thing I have observed and you should keep in mind is that small hands can and will have a tough time pushing thumb shifters. They DO get more skilled with time and practice though.

    I wanted to change out the crank to be able to run a narrow-wide chainring, and possibly shave a few grams in the process. Low and behold, the stock crank was actually 28T (not a narrow-wide but stamped steel chainring) and it was alloy, adding up to something actually very light in stock form! But I ordered a Spawn 127mm w/NW in 32T. It is heavier than the stock unit, has 4 more teeth, and is SO nice. Dang kid.

    This takes me to that crunchy bottom bracket. I planned on a simple swap to a Shimano UN55. It was not that simple. First, to take the hard work out of aligning the chain-line, order the 113mm 73. I did the measurement and the maths and there you go. The stock BB is 133mm due to the construction of the crank. I'm sure you could make a 127mm crank work if you wanted to run the stock crank, but it was way out of line for the Spawn. Be sure you either copy this setup, or take the time to buy the crank, mock it up, do the maths, and order the right crank. And if you are between two measurements, go to the smaller one. All of that yielded a buttery smooth BB for less than $20.

    Connect the rotating bits with an XT 10 speed chain.

    At this point the major functional components have been upgraded and the bike rides outstanding. She can grind up hills, through loose sand, smooth streets, and even ride directly over parking blocks like they aren't there. We did a few cosmetic things to personalize the bike.

    Lizard Skins Moab Lock on Grips
    Rant Hella PC pedals

    She is happy. Dad is happy.

    Next upgrades...Chinese carbon bars, Kenda Slant 6 tires, and tubeless setup.

  4. #4
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    Quote Originally Posted by gobo333 View Post

    Next upgrades...Chinese carbon bars, Kenda Slant 6 tires, and tubeless setup.
    Nice! We found the Zee 10 speed shifter and rear derailluer (clutch off at first) operated a bit better than the XT. Our daughter was having problems shifting with XT, for whatever reason, I think it has slightly longer "throw" in the upshift lever if you will.

    Curious on the crank upgrade. 28 to 32 tooth, most are looking for lower climbing gears, not harder. Was your daughter spinning out the 28t on flats? Also, I think you are going to be adding more weight with the Kenda Slant 6's. They are 600g as I recall. Would be interesting to hear what the CST (Maxxis' parent company) weigh. The CST is actually a fairly good tire.

    Thanks for the great writeup and have fun with the mods! This is a bike we've not seen much of posted here.

  5. #5
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    Quote Originally Posted by GSJ1973 View Post
    Nice! We found the Zee 10 speed shifter and rear derailluer (clutch off at first) operated a bit better than the XT. Our daughter was having problems shifting with XT, for whatever reason, I think it has slightly longer "throw" in the upshift lever if you will.

    Curious on the crank upgrade. 28 to 32 tooth, most are looking for lower climbing gears, not harder. Was your daughter spinning out the 28t on flats? Also, I think you are going to be adding more weight with the Kenda Slant 6's. They are 600g as I recall. Would be interesting to hear what the CST (Maxxis' parent company) weigh. The CST is actually a fairly good tire.

    Thanks for the great writeup and have fun with the mods! This is a bike we've not seen much of posted here.
    Interesting on your Zee shifter. Thatís outstanding to hear, and only $20! Itís truly amazing what they produce. If this XT becomes a bother, Iíll give that a try for sure.

    I had thought all along it came with a 32T as advertised. Only after counting did I discover it was 28T. So far, she has plenty of gear with the 32T. Her spirit gives out before her legs right now! But I have plans to get a 30T when she needs more. That is as small as the Spawn crank will go. Fortunately the 11-36 helps on the back end too. 🤞🏽

    Tires. Agree the 2.8 CST seems to be a good tire. Even with tubes, I run under 20lbs. I plan on taking one tire off and weighing it after our Labor Day mountain trip. I couldnít find its weight anywhere online, nor could I find documented success at converting to tubeless. In my research, the Slant 6 is tubeless ready, and is the lightest of the plus tires. Iím interested to hear more opinions/experience on the matter, but I want to stay plus size ultimately. To go down would be much lighter of course. Below are the numbers I accumulated...

    Tires
    CST Fringe (on bike) - 2.8 - xxxg - $28
    Specialized Big Rollers - 2.8 - 670g - $25
    Kenda Slant 6 - 2.6 - 574g - $35
    Kenda Kaos Sport - 2.8 - 732g - $35
    Kenda Kaos Sport - 2.6 - 686g - $35
    Maxis Creepy Crawler - 2.0 - XXXg - $28
    Spawn Brood Maxton - 2.2 - 440g - $40
    Schwalbe Little Joe - 2.0 - 290g - $20

    Iíll get some photos up soon. Hopefully this give others another data point as so little is avail on this bike right now. Thanks for the notes!



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  6. #6
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    Nice thread post some pics...might pick up a 24 soon still on the edge for my youngest daughters next bike.
    XC, Road, XXC, Endurance, Mtn, All-Mtn, Cross, Gravel, just go have fun on 2 wheels!

  7. #7
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    I'll get some images of the bike posted this weekend.

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    Some better images...still happy with the results Will put it to the test in Big Bear next weekend!












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    Thanks for the post, this is great stuff!

    I'm on the fence of buying the Roscoe 20 for my younger daughter and knowing that I can swap the spare 11-36 cassette I have laying in my part bin is great. I looked at the Riprock but I didn't like the weight, grip shifter and freewheel at the back.

    With 2.8 tires I plan on bringing her ride with me during winter as for a 48lbs girl the tires should be ok on groomed trails. Might want a tire with better grip though.

  10. #10
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    Thanks so much for this detailed post, this is exactly the kind of stuff I'd look to do when I pickup a Roscoe 20 / 24.
    My kids are a little on the short side, so I was wondering what mods I could do to shorten the reach.
    The Trek website does not seem to list the stem length (it just says 31.8mm - which is the diameter no doubt). Would you be willing to post the stem length for your Roscoe 20?

    I could also roll the handle bar a bit, to make use of the rise, but that alters the sweep too, so I would not be able to get very far with that.

  11. #11
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    Good stuff, just ordered my 6 year old one in lilac! I'll be matching a few of your ideas like the 10sp (but with a NX cassette) the short cage Zee mech, narrow/wide ring, Shimano MT500 hydraulics with XT rotors, tubeless, 30mm stem w/ cutdown 1" riser bars and might even build some new wheels!

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    Shimano MT500 hydraulics with XT rotors
    If I was splurging on anything it would be the brake levers for something that can be used 1 finger.

    Ultimate kids shifting is probably 11 speed SLX M7000 as it has 20% less force required at both ends than XT M8000... however the main thing in our climate was actually using full length good quality cables and outers and swapping reasonably regularly.

  13. #13
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    I already have then as take offs! I should be able to get 1 finger braking with her
    ------------------------------------------------------
    "Loud hubs save lives!"

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    1 finger braking was by far the biggest challenge/habit we had to break ...

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    Quote Originally Posted by Steve-XtC View Post
    1 finger braking was by far the biggest challenge/habit we had to break ...
    Definitely a challenge -- I'm still working on it myself!

    Looking ahead, what size bars does it start to become feasible on kids' bikes? On the 460mm wide bars on our Spawn Yoji 14, there's not enough room to even move the levers far enough inward for it to be possible.

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    Quote Originally Posted by TimTucker View Post
    Definitely a challenge -- I'm still working on it myself!

    Looking ahead, what size bars does it start to become feasible on kids' bikes? On the 460mm wide bars on our Spawn Yoji 14, there's not enough room to even move the levers far enough inward for it to be possible.
    Of course it's one of those annoying things it sorta compounds that the smaller they are and their hands and bars (and the old diameter bars/stem).... and size of the grips.
    More than anything I think its a combo of what you can get on the bike... if you can swap the stem and put on different bars etc. (once you do this the stems at least get reused.. so his stem on his 20 started at 35mm, then 50mm then 80 for a short time.. then onto the 24" with the 35mm... etc. The bars also saw some reuse... but obviously you can't put length back but he now has a XC bike and DH bike and the XC bike bars are the longest from the 20"... and the DH bars came off my XC bike ...


    The first variable is levers so a SLX/XT lever designed that way doesn't need to be as far inboard as the lower end ones... We skipped this right until he was big enough for the 24 because he had rim brakes...

    I wish I hadn't.... because even when the brakes got swapped for something his pinky could lock up his habit was grabbing a handful... he even accepted he didn't need more than one finger but when it comes down to panic it's one thing to know and another to react. He persisted for a long time... and in that time he was riding stuff that was just crazy to ride without ... especially given limited fork travel etc. (which he had by that time) but obviously even worse rigid.

    Nothing else even comes close in terms of breaking habits to braking habits...
    He's now just turned 9 and has 90mm grips ... something you can at least buy.(if not easily) .. but previously it's been a case of sacrificing a set with single lock-on and just cutting down .. so the brakes could be moved in... and to an extent also put the shifter OUTSIDE the brake...

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    has anyone here with a Roscoe 20 managed to set up tubeless? I've spent hours trying with the original CST tyres but cannot get the tyres to take air!

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    Before I committed to trying tubeless, I decided to see how low I could drop the pressure with the stock CST/tubes setup. Granted my daughter is small, and not a hard core shredder yet, but Iím running them at ~8lbs and have yet to experience a flat. She rides straight up and over curbs and parking blocks like it ainít no thing. You might be past this point already.


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    Quote Originally Posted by Charlie Don't Surf View Post
    Good stuff, just ordered my 6 year old one in lilac! I'll be matching a few of your ideas like the 10sp (but with a NX cassette) the short cage Zee mech, narrow/wide ring, Shimano MT500 hydraulics with XT rotors, tubeless, 30mm stem w/ cutdown 1" riser bars and might even build some new wheels!
    Want to see! Lilac with mods!


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  20. #20
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    I just wanted convert to save a bit of weight and have the extra puncture protection from the sealant since we have a lot thorns around here .. I think the only chance I have is building the inner of the rim up with lots of Rim Tape, unless someone has had success another way!

  21. #21
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    The Roscoe 20 is an awesome bike. I searched diligently over the spring/early summer for the right bike. I was in the local Trek dealer to order one before they had even heard about its release.

    I made the factory brakes work by adjusting the reach screw all the way in and letting a little cable out so they engage where he has more strength. The brakes are certainly the low point in my opinion, but they get the job done. I am frequently back and forth on replacing them. My wife keeps saying "you want to spend how much on brakes for a $400 kids bike?!"

    We've been running about 8 psi in the tires since day one without issue.

  22. #22
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    Thanks for the upgrade tips.

    For anyone considering the Roscoe, my 6.5 year old has been riding this on our trails in Marin for the past 6 months. We ride twice a week, usually 8 to 10 miles per ride with anywhere from 500 to 1000 ft of elevation gain. The terrain varies from easy fire roads to single track and rocks.

    The bike has been absolutely fantastic. He's learned great climbing and downhill skills on it and because it's full rigid he's learning how to pick good riding lines.

    My only advice is to upgrade the brakes right away if you plan to have your kiddo ride long downhills. The stock mechanical brakes are hard to reach, hard to pull, and build bad grip and breaking habits. Once that upgrade is made... this bike is hard to beat.

    I put a set of XT Hydraulic brakes on the bike. I got them on sale. It's almost like those brakes were made for small hands

  23. #23
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    I second that for the brakes. The mechanical are hard to activate for a kid. Even entry level hydro brakes are easier than mechanical. Only problem is now my kid is spoiled and could never go back to mech brakes...

    For those who would want tire with more grip, Vee make the crown jewel in 20 x 2.80:
    https://www.veetireco.com/listings/plus-size-crown-gem/

    I might give them a try as the CST are too slippery in snow. Only problem is that they are hard to find in Canada...

  24. #24
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    Oooooh! Look nice!


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    I just ordered my son a Silver Roscoe 20!

    It will arrive at the LBS in a few days.

    Based on everyone's recommendation, I would like to upgrade the brakes to hydraulic as well.

    Are the rotors reusable?
    Just need to swap the lever and add caliper/line?

  26. #26
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    yes, I've got the original rotors on with slx brakes. Had to face the frame so the rear caliper would align up.

    Would love to get it tubeless, has anyone managed it?
    Last edited by shaudy; 4 Weeks Ago at 11:51 AM. Reason: missed off some text.

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