Results 1 to 23 of 23
  1. #1
    mtbr member
    Reputation:
    Join Date
    Jun 2005
    Posts
    179

    Hotrock 20" - 8 speed options?

    I have searched on here for hours and not really got the exact answer i am looking for.

    Using the stock wheel/hubs, can i turn the Hotrock 20 into an 8 speed?
    SRAM / Shimano? Will anything fit? Or can i only go 7 speed with the stock wheels / hub?
    Ideally i would like a 34T for the freewheel but 32T will do.
    And what options for Shifters, Rear Derailleur, and Chain?
    Can i mix match SRAM Trigger Shifters with some Shimano stuff?
    Sorry for so many questions.

    I am also buying Sinz 115mm crank arms, new 34T chain ring, and Bashguard.

    I have seen this 7 speed Shimano Tourney/Acera setup ($45 but probably heavy) and it is ok, but i would like to go 8 speed if possible.

    Amazon.com: Shimano MF-TZ31 Tourney Freewheel (14-34T Mega 7 Speed): Sports & Outdoors

    Amazon.com: Shimano Acera SL-M310 Rapid Fire Shifter, Right (Black, 7-Speed): Sports & Outdoors

    Amazon.com: Shimano Tourney TX75 6/7 Speed Rear Derailleur: Sports & Outdoors

  2. #2
    Wēk Ss
    Reputation: IAmHolland's Avatar
    Join Date
    Jul 2010
    Posts
    2,516
    Quote Originally Posted by xnofriendsx View Post
    Using the stock wheel/hubs, can i turn the Hotrock 20 into an 8 speed?
    ... Or can i only go 7 speed with the stock wheels / hub?
    ... And what options for Shifters, Rear Derailleur, and Chain?
    ... Can i mix match SRAM Trigger Shifters with some Shimano stuff?
    No.
    Yes, but there may be some issues. I had issues with it, some chain rubbing on cogs here and there, and overall poor shifting. Others report no problems.
    Same as your bike.
    Yes, and no. SRAM Attack will work. Others, no. I suggest you spend some time reading about SRAM and Shimano in the drivetrain section. There's nothing magical about a kid's bike. It works the same way as any other bike.

  3. #3
    mtbr member
    Reputation:
    Join Date
    Jun 2005
    Posts
    179
    Thanks. I will be sticking to an all Shimano 7 speed setup.

    $55 for 7 speed Shimano Shifter, Rear Derailleur, Freewheel, and Chain
    $75 for Sinz 115mm crank arms and 68x113 bottom bracket
    $35 (good price) for 2 Kenda Small Block 8 Tires
    $15 BBG Bashguard
    $20 34T chainring

    $200. Yikes, but not too bad i guess. My 8 year old needs to be able to climb this bike easier on some rides and with that setup he should be pretty decent. The stock setup is horrible for steep climbs. We have some really rocky decents as well so that bashguard setup will work great along with the 115mm cranks for clearance.

  4. #4
    N/A
    Reputation:
    Join Date
    Feb 2004
    Posts
    211
    What is the gear range of the 7 speed? I looked into this briefly but only found 14-28 speed freewheels in both 7 or 6 speed. So basically, no change in the gear range, just one more gear providing smaller gaps between gears on the 7-speed. Since my goal was to have a broader gear range, it didn't make sense to change out the freewheel & shifters.

    I'll probably eventually build a custom wheelset so I can use a 9-speed cassette but that's expensive and the stock setup seems to be working fine for now. Climbing steep hills is often more of a mental challenge than a physical one right now.

  5. #5
    mtbr member
    Reputation:
    Join Date
    Jun 2005
    Posts
    179
    Quote Originally Posted by mtnbkaz View Post
    What is the gear range of the 7 speed?
    14/34T Megarange 7 Speed Freewheel

    Amazon.com: Shimano 7 Speed Freewheel, 14-34, MegaRange: Sports & Outdoors

  6. #6
    N/A
    Reputation:
    Join Date
    Feb 2004
    Posts
    211
    Oh yeah, I forgot about the Megarange. Let us know how that works out - I've never used one so I'm curious how well it works with the big jump to the granny gear. Guess the parts are cheap enough that it's a much less expensive experiment than building a custom wheel with a standard freehub.

  7. #7
    mtbr member
    Reputation:
    Join Date
    Jun 2005
    Posts
    179
    I was sort of having a problem with a 34T chainring. Most of them were for 8/9/10/11 speeds. Then i found out that Sinz makes a 34T 110 BCD 5 bolt chainring for 3/32 chains / 7 speeds, etc for only $20.
    Now i am wondering about the Bottom Bracket size. I have seen 68 x 113 and 73 x 113 as well as a few other sizes, but i am using the Sinz Cranks.
    I think i read another post where a guy put the Sinz cranks on it and originally tried the 73 x 113 but ended up using the 68 x 113.
    So i am pretty sure it is 68 x 113 with these Sinz cranks if anyone can confirm this.

  8. #8
    mtbr member
    Reputation: Aresab's Avatar
    Join Date
    Mar 2007
    Posts
    1,232
    When my son was on a Hotrock 20 I put a 14/34 megarange on. It was a great improvement, but it did not work with the stock derailleur at the time, a Tourney. Not a big deal to me, I have a few Deore level ones around which worked perfect. He was able to climb things he was not able to with the 13/28.

  9. #9
    Wēk Ss
    Reputation: IAmHolland's Avatar
    Join Date
    Jul 2010
    Posts
    2,516
    The chainring doesn't matter, especially for single speed rings. 7, 8, 9, 10, it doesn't matter.

    The hotrock should have a 68mm shell width.

    I believe, not sure, that the sinz with a 113 should give you a 47/48mm chainline. I had a FMF crank with 113 ISIS on an older hotrock. You may want to measure your chainline, to see where the cogs line up on the freewheel.

    I too used the 14/34 for a bit. I built a wheel shortly after. The large jump wasn't so good, although it was useful, there needed to be a better range. For my son, I ended up with a 2x8, running 22/32 with 11-32 in the back. For my daughter I went 1x9 with a 28T ring and 12-36 in the back. My son was stronger and was able to shift the front at 6/7. My daughter cannot, hence the 1x9. The 32 ring with the 11 in back has better top end than the stock 36x14, and more clearance for technical rides.

    FWIW, 36x14 is very similar to 28x11. So going to 28x12 loses a bit of top end. That's not a big deal for my daughter, as she's not aggressive. The 28x36 is good for steep climbs.

  10. #10
    GMF
    GMF is offline
    Mmm... Tasty
    Reputation: GMF's Avatar
    Join Date
    Jan 2004
    Posts
    700
    Why do want a new crankset? You won't get a much smaller chainring, and it seems pricey. Also, I would wear out the stock knobby tires first. Assuming they haven't changed much over the last few years, they work pretty darn well and aren't crazy heavy.

    I'm happy with the mods I made which focused gearing (which you've got a handle on) and weight which essentially consisted of ditching the chain guide and the steel handlebar. The hotrock is a good, capable bike with a couple minor mods.

    Good luck!

  11. #11
    N/A
    Reputation:
    Join Date
    Feb 2004
    Posts
    211
    Quote Originally Posted by GMF View Post
    Why do want a new crankset? You won't get a much smaller chainring, and it seems pricey. Also, I would wear out the stock knobby tires first. Assuming they haven't changed much over the last few years, they work pretty darn well and aren't crazy heavy.

    I'm happy with the mods I made which focused gearing (which you've got a handle on) and weight which essentially consisted of ditching the chain guide and the steel handlebar. The hotrock is a good, capable bike with a couple minor mods.

    Good luck!
    GMF, I personally agree with the value proposition of the crankset, but what are you doing for chain retention if you ditched the stock guide? I'd be worried about constantly dropping the chain.

    Re: stock tires - I thought I'd just replace them when they wear out but I'm considering ditching them for something with bigger knobs. I thought it was cool that the stock tires came with the armadillo casing but the low knob tires don't have much traction when we hit loose sandy patches.

  12. #12
    GMF
    GMF is offline
    Mmm... Tasty
    Reputation: GMF's Avatar
    Join Date
    Jan 2004
    Posts
    700
    I have a couple things - i drilled a few holes in the chainring and fabbed some chainguides for the inside and outside. That works about 95% of the time. My son does occasionally drop a chain, but not enough to worry about. We did 15 miles on Saturday and didn't drop once, but he isn't a super hard charger big air dude (although he is trying... unsuccessfully :-) ). You have the plastic chain guard on the outside, and there are plenty of examples of inside chainguides clamped to a seat tube. I also shortened the chain to keep the derailleur tension up as high as possible (the cage is pointed forward in low gear).

    Re: the tires - you have different ones than we do, i think. I do not believe my son's have armadillo casing. We ride a lot in sandy conditions (hardpack with sand pits thrown in there here and there), and the stock tires with low knobs are OK and well suited to our terrain. Admittedly, i float over better with my 26x2.4 tires, but i think any 20" tire would plow into the sand.

    I'm not telling you to not upgrade, you just seemed a little put off by the $200. I'd suggest starting with the minimum upgrade ($55 for the improved gearing and shifter), see how it works from there, and then let the little guy participate in getting the new parts and installing them.

  13. #13
    Wēk Ss
    Reputation: IAmHolland's Avatar
    Join Date
    Jul 2010
    Posts
    2,516
    N-Gear, Home of the Jump Stop

    I use this, when running a single up front. In conjunction with the bash guard (stocker also has one), I've not seen any chain drops.

  14. #14
    mtbr member
    Reputation:
    Join Date
    Jun 2005
    Posts
    179
    @IAmHolland...

    Chainring - Check
    68mm BB Shell - Check
    Chainline - I will have to check that out. We will see when i get the stuff.
    2x8 and 1x9 - Maybe eventually, but i am not doing a wheel built yet just to get the 8/9 speed. I will see how the 1x7 goes with the 14/34 and go from there. Still a lot better than what it is stock. 36x28 vs 34/34
    I am not worried about the top end. A lot of our riding is really technical and slow. And i mean really technical, even for adults. My 8 year old rides well. He has been on bikes, dirtbikes, and skis since age 3. We don't have those long open downhills. My main concern is just making it easier for him to climb. I wish i could get a 32 or 30 with the Sinz cranks, but the 110 5 bolt will only go as low as 34. Just going to experiment a bit.

  15. #15
    mtbr member
    Reputation:
    Join Date
    Jun 2005
    Posts
    179
    @GMF...

    I want a new crankset because i want shorter cranks first of all. We ride in a lot of rocky stuff and my son ends up hitting a lot of rocks. His bashguard broke right away but from what little is left on it, it still stays on fairly well.

    The stock knobbies were bad even when new. They are worn out anyways. Those stock tires were very sketchy on some of the trails we ride. He needs better ones. Looking at a few, would love to get the Mow Joes, but dang those are as much as my dirtbike tires. MTB stuff is a rip off.

    I have a 25.4 FSA Gravity Carbon bar just sitting in my garage and hopefully a few things here and there will drop the weight. I think it is right at 24.5lbs or so. I am going to do ghetto tubeless as well.

    Thanks.

  16. #16
    mtbr member
    Reputation:
    Join Date
    Jun 2005
    Posts
    179
    Quote Originally Posted by GMF View Post
    I'm not telling you to not upgrade, you just seemed a little put off by the $200. I'd suggest starting with the minimum upgrade ($55 for the improved gearing and shifter), see how it works from there, and then let the little guy participate in getting the new parts and installing them.
    I am spending the $200 and not too bummed. Stuff is expensive, just how it goes. Oh well. He needs better tires as well. We didn't get much snow this year so we will be riding early unless we just get dumped on in March/April.

    Here is a video i did of my son riding. This done when he was 4-6. Mostly on his Hotrock 16 and on his KTM 50 Mini Adventure and PW50.


  17. #17
    mtbr member
    Reputation:
    Join Date
    Jun 2005
    Posts
    179
    And here is a video of me riding, but my 8 year old rides this now on his Hotrock 20.


  18. #18
    Wēk Ss
    Reputation: IAmHolland's Avatar
    Join Date
    Jul 2010
    Posts
    2,516
    It looks good. In this case, I recommend Crank Arm Shortening which is what I used for my son and ran 2x9 with 22/32 145mm cranks. You can run it as a single, but the Q-factor is wider than a BMX crank. We ride technical terrain too, just not at high speeds. Another option is to use 3 piece BMX cranks for a smaller ring. It's more expensive, $300+, for a full setup.

    Profile Racing E-Store

  19. #19
    mtbr member
    Reputation:
    Join Date
    Jun 2005
    Posts
    179
    Trust me, i would love to run a 1x9 or 2x9 and use existing cranks i have, get them shortened, etc. But the wheel build to get it there is just not in the budget. That is why i was originally asking about a 8 speed setup but that is a no go too. So i am stuck with 1x7 for now. 34/34 shouldn't be too bad, way better than stock.
    I should have this stuff ordered this week hopefully and have it built here in a bit. I have my wife's old bike i am fixing up and all of my new dirtbike stuff that just came in so its gonna be a while until i get to it. I will post some photos when i am done.

  20. #20
    GMF
    GMF is offline
    Mmm... Tasty
    Reputation: GMF's Avatar
    Join Date
    Jan 2004
    Posts
    700
    It sounds like you have this pretty well figured out, but why do you need a wheel build to go with shortening your existing cranks? Especially if you went with a 1x7 setup, you can easily use a 7sp/8sp chain with the "9sp" chainring. Not knowing what kind of cranks you have floating around, that could very well be the ticket for getting a smaller chainring. Is the concern chainline, chain compatibility, ...?

  21. #21
    mtbr member
    Reputation:
    Join Date
    Jun 2005
    Posts
    179
    I only spoke about the wheel build for the 9 speed cassette. Can't do a 9 speed with the stock hub/wheel so i am just going for a 1x7.
    I don't like the 36 chainring up front with the stock cranks, plus they are too long.

    Can i get another chainring with this stock crank? If so, let me know.

    I wouldn't think so, they screw in or something. But then again they are still too long.
    I could pay for them to get shortened, but i am not spending money on those stock cranks. I would rather spend the $50 on the Sinz cranks and new UN54 BB.

    I do have a set of RaceFace Evolve XC cranks (in great condition) that i could shorten, but it is actually pretty expensive to shorten them, and just not worth it.
    I was actually putting a bunch of stuff on ebay this week and those cranks were on my list.

  22. #22
    GMF
    GMF is offline
    Mmm... Tasty
    Reputation: GMF's Avatar
    Join Date
    Jan 2004
    Posts
    700
    Sorry, my misunderstanding, then. Yes, the stock cranks are not worth reusing (although in my infinite cheapness, I turned the gear into a spider for a 5bolt 94 bcd chainring - dremels are a wonderful thing). I misread that you had a crank just lying around you could shorten with chainrings, etc.

    My son is running a 32/32 low and that gets him up most hills if he tries. I'm going to switch to a 29t chainring soon, though.

  23. #23
    Wēk Ss
    Reputation: IAmHolland's Avatar
    Join Date
    Jul 2010
    Posts
    2,516
    You could run 2x7 too, or shorten the cranks you own and run 1x7 to get a 32T front instead of 34T. What happens on the front is largely independent of the rear. You would forgo the Sinz crank in that case. I use the shortened Truvativ cranks as a double 22/32 on the 7 speed first, before I built the wheel for a cassette.

    My daughter is using the same cranks, and running it with a 28T on the smallest ring as a 1x9.

Similar Threads

  1. 2013 Specialized 7 speed 24" Hotrock
    By CrashCanipe in forum Families and Riding with Kids
    Replies: 28
    Last Post: 11-11-2013, 07:07 AM
  2. Project "green machine" Hotrock 20"
    By m-dub in forum Families and Riding with Kids
    Replies: 58
    Last Post: 02-16-2013, 12:30 PM
  3. Ok, got the 24" Hotrock..now what
    By TiGeo in forum Families and Riding with Kids
    Replies: 6
    Last Post: 01-18-2013, 07:13 AM
  4. 20" hotrock 2X9 ???
    By yetipop in forum Families and Riding with Kids
    Replies: 22
    Last Post: 12-20-2012, 10:17 PM
  5. Need help fixing up Specialized Hotrock 20 6 speed
    By imero in forum Families and Riding with Kids
    Replies: 19
    Last Post: 10-13-2012, 06:45 AM

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •