# Hotrock 20 mods on a budget



## 08FXT (May 3, 2012)

First off, thanks to everyone who posted material in the "Families and Riding with Kids" section, the info has been tremendously helpful. I am not much of a DIYer and only a recreational mtb'er, so getting all the info from here on which parts work together has been great. :thumbsup:

As I quickly realized when I started looking for a decent, non-walmart bike for my 6 year-old, there are very limited options out there. As many others, I ended up going with a Specialized Hotrock 20. Decent bikes for the money, but if your child is like mine, most of the parts will need replacement after only a couple of month's use.


























After coming across cinq's build, I thought that was the way I wanted to go. I have very little parts laying around in the garage, and a limited budget, so I decided to do this in stages as I find cheap parts.

*Tires*
I started out with tire search: Schwalbe Mow Joes seemed perfect for the trail conditions in my area (Eastern Canada), but they were impossible to get and are being discontinued. I have gotten an excellent list of alternatives here, but as I was going to pull the trigger on another tire, I did one last google search and got lucky and found those 15 minutes from my place:










*Grips/Pedals *
The original grips were pretty useless, so I got the ODI rogue, which have excellent cushioning and grip. Many other folks have gone with aluminum or metal pedals, but given how my son hurt his shins last summer, I decided to search for plastic options, plus they are lighter. I thought I'd also invest in shin gards, so part of my budget went to these RaceFace Protekt. 
I was going to go with gusset BMX pedals, but they seemed a little too large. I ended up finding these at my LBS, so I thought I'd give them a try and see how my son does... at $2 a pair, it's worth a try:










Upgrading to 9 speed requires a bunch of parts, and having only an XT derailleur and deore rapid fire shifter on hand, changing the crankset, rear hub, wheel, and cassette will have to wait a little.

I got a new OEM derailleur (shimano tourney) which weighs a ton, but at $12 a piece, it will do the job until I gather the parts for the 9-spd swap.

My list of parts to find:
•	Sinz (or other brand) cranks 135mm
•	Sinz bottom bracket 113x68mm 
•	34t chain ring
•	Bash ring
•	Simano XT hub
•	SRAM PG990 cassette
•	Sram chain
•	New brakes

end result:









Just refreshing these few parts made a big difference in the fun factor; I can't wait for the 9-spd swap!



















Quick questions:
1. The Mow Joes are 1.85 rather than the 20x2.00; I've put one in the front and installed his front OEM tire in the rear as it still had good thread. What is the impact of narrower tires? I assume less stability but perhaps more control and reactiveness?

2.Sinz cranks seem the way to go for 135mm, but they only come in 5 bolt pattern. Finding sub-$100 cranks in 4-bolt pattern has been a challenge. Anyone had luck finding another brand in 4-bolt pattern for less than $100?

Cheers!


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## Surfpoodi (Sep 14, 2011)

Nice work. You might want to add some aluminum bars to your replacement parts list. They are relatively cheap, and the stock steel bars weigh a ton.

Narrow tires are lighter, but outside of that, have few advantages (though lightness in and of itself is a very good thing). Wider tires allow you to run lower pressure without increasing pinch flat risk, thereby generally improving handling and comfort. Some will say narrower tires roll faster, but the actual data I have see on that seem to suggest otherwise. 

Incidentally, I bought the exact same bike, same year, same color, this week for my boy....


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## mhkang (Nov 1, 2008)

nice work on the bike. just received some cranks from Mark at bikesmithdesign. His work to shorten cranks to 135mm looks great. The stock 160mm was only $80.


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## IAmHolland (Jul 8, 2010)

FWIW, on my daughter's 1x9 I used the Shimano HG61 12-36T cassette with a 28T front. It helps her climb the hills we have here, but she loses out on flat and topend stuff. When she gets stronger I can increase the front ring. I wish there was a 11-36T, or perhaps I can steal one from my other cassettes.

I used bikesmithdesigns for the crank, 145mm IIRC, or maybe 140mm.


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## Surfpoodi (Sep 14, 2011)

Can anyone opine on the wisdom of using the Sun ICI-1 rim in 28h as replacement wheels for a HR 20? It is listed as 21mm wide, which is a couple mm narrower than I'd like, but I figure it should still work for 2" tires, maybe?

I guess I'm not allowed to post links, but you can find the rim on Amazon.

They are certainly light at 310g


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## Shayne (Jan 14, 2004)

Sun ICI-1 is a BMX mini rim. Not the same diameter as a 20" mtb rim. This would be fine for discs but you can't use them with rim brakes.


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## 08FXT (May 3, 2012)

Surfpoodi said:


> Nice work. You might want to add some aluminum bars to your replacement parts list. They are relatively cheap, and the stock steel bars weigh a ton.
> 
> Narrow tires are lighter, but outside of that, have few advantages (though lightness in and of itself is a very good thing). Wider tires allow you to run lower pressure without increasing pinch flat risk, thereby generally improving handling and comfort. Some will say narrower tires roll faster, but the actual data I have see on that seem to suggest otherwise.
> 
> Incidentally, I bought the exact same bike, same year, same color, this week for my boy....


Thanks for the idea on the aluminum bars, they are indeed quite cheap, and for the advice on tires.
Congrats on the new bike! I hope your boy is as happy as mine with it!



mhkang said:


> nice work on the bike. just received some cranks from Mark at bikesmithdesign. His work to shorten cranks to 135mm looks great. The stock 160mm was only $80.


Thanks for the suggestion; bikesmithdesign seems like the way to go! He even has a "kids" package with the BB and a RaceFace Bashguard included.


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## Surfpoodi (Sep 14, 2011)

Shayne said:


> Sun ICI-1 is a BMX mini rim. Not the same diameter as a 20" mtb rim. This would be fine for discs but you can't use them with rim brakes.


Thanks for the tip. I didn't realize there were two wheel sizes both called "BMX 20" rims". Goofy, but I'm glad I picked that up before ordering the wrong size.

FYI- if others don't know, ISO 406 is standard 20" BMX size, and the right size for a HR. ISO 451 is the mini BMX size, and too big for a HR. At least that is my current understanding! Correct me if I'm wrong.


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## spyguy (Apr 18, 2006)

awesome mod!

does anyone know what front forks with shocks will fit the hotrock 20 frame?
recently picked this one up for my daughter, and looking to add disc brakes, free hubs and an aluminum bar.


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## JonathanGennick (Sep 15, 2006)

Might have been better to begin a new thread rather than resurrecting one, but....



spyguy said:


> awesome mod!does anyone know what front forks with shocks will fit the hotrock 20 frame?


The fork on the bike in your photo does not look to be suspension-corrected. Any suspension that you add to that frame would throw off the geometry, so I would leave the rigid fork in place and ride the bike without suspension.

Disk brakes would require a new frame and fork having caliper mounts. You're pretty much replacing the bike to get there. So again, I would ride it as it sits. Just MHO.


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## stom_m3 (Jun 28, 2011)

I would concur with Jonathan. The base bike is a BMX type with a coaster brake. What is your goal with the bike and the type of riding you want to do? I'd just ride it the way it is. If anything, ditch the coaster (requires new rear wheel) as it just leads to worn rear tires and bad habits.


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## watts888 (Oct 2, 2012)

I'd also be concerned with headtube diameter on that bike. It's probably a 1", which severely limits what will work. The following is based on the hope that it's 1 1/8" steer tube diameter. Possible things to look for that might work.

alloy fork. Will lighten the front end, but will make the ride more mash. If the stock fork is steel and isn't bent, ride it. A lot of this goes back to the length. Finding a replacement fork that short will be difficult, and using a longer one will mess with the handling.

Handlebar. With an 80mm riser stem, you could put on an alloy or carbon fiber riser handlebar. Lighten it up, and carbon would help with vibrations in the handlebar. Even with a riser stem and a riser bar, it'll still put the handlebar lower than current. Good for aggressive trail riding, not as comfortable for casual riding. It is transferable to a new bike though.

Rim brakes up front. the fork should have a center drilled rim brake hole. Not as good as v-brake post mounts, but it will still add brakes up front.

New wheels: assuming those are painted steel rims, alloy rims will lighten it up a lot, work better with rim brakes, and allow a better rear hub that could have a freewheel.

rear shifter: You can purchase a horizontal dropout universal rear derailure hanger for something like $4. Of course, you'd also need a rear derailure, shifter and rear hub that can take a freewheel.

tires: obviously the lighter the better. something the OP did that I didn't like was put the wider tire in back and the narrow tire up front. always put the wide tire up front. You can use less pressure, and it will give you more traction up front where you need it.


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## Steve-XtC (Feb 7, 2016)

stom_m3 said:


> I would concur with Jonathan. The base bike is a BMX type with a coaster brake. What is your goal with the bike and the type of riding you want to do? I'd just ride it the way it is. If anything, ditch the coaster (requires new rear wheel) as it just leads to worn rear tires and bad habits.


+3 on that.

My kid went from buying a 20" he only just got onto to buying a 24" he could only just get on in 9 months.

Kids don't really need disc brakes as they don't weigh much. They are nice to parents who have to keep truing wheels though. (Reason once you dial in the brakes for short reach you have little play on the rims - depending what you ride it can get very annoying if its mud that causes a constant squeek)

In order to add disc brakes will mean 2 new wheels, a new fork and some "device" that the frame isn't designed for to hold the rear caliper. (Given kids weights this probably isn't an issue but its messy and expensive with little return on something that may not be used for more than a year)

As others noted your choices of fork are limited and a spring fork is likely to be ineffective and just add weight. With this in mind I'd think towards the next bike and getting decent air forks and if you want discs a frame with mounts.

Wheels for 20" are possibly (I don't know your market) easier to get.

Here in Europe there is a folding bike market that uses 20" wheels for commuters and they sell some expensive bikes meaning its easier to get decent 20" wheels than 24".


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