# Lightening up Specialized Hotrock 24



## lidation (Jun 16, 2010)

Most 24" kids bike weigh 25-30lbs, half the body weight for kids of 8-10 age. Imagine an adult riding a 75-100lb bike!

I am posting this thread to contribute the weight information of a Specialized Hotrock 24 and hope it helps some of you to make better choice for your little ones.

I got my 8 year old son a used Specialized Hotrock 24 with rigid fork with 1.5" street tire. This thing weighed 26.0 lbs!!!! Heavier than my full suspension mountain bike.

Below is the actions I took to reduce it to 22.5lbs.
1. Replace that darn handlebar. It weighs 516grams!
2. Remove the kickstand and the reflectors
3. Remove the front derailleur, cable and shifter
4. Replace the seat post with a carbon fiber one.

Next, I will need to figure out what crank/BB options I can pursue to further bring down the weight.


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## POAH (Apr 29, 2009)

tyres, tubes, wheels, crank, seat post, saddle and like you said bar will normally be heavy but its a cheap bike.


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## ghabe (Mar 7, 2015)

I picked up an 11 inch ~2009 Specialized Hotrock 24 A1 FS frame yesterday. I will be building it in the coming weeks. I know it's a different model than the one from lidation, but it weights 1.309Kg or 2.89 pounds if that helps anyone:


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## jestep (Jul 23, 2004)

Here's the build thread for the one we did last winter: http://forums.mtbr.com/families-riding-kids/our-24-hotrock-build-novella-version-guide-994732.html

It's a hair under 19 lbs as shown.

I wish I had started with a rigid one like yours. Amazingly the mosso fork is actually the correct height but it definitely looks a bit odd. Cheap upgrade at least.

Just went with a chinese carbon riser bar, came in around 100g after it was cut. Super light but it's really stiff. I'm not sure I'd want to go crazy, but I would feel comfortable as an adult riding XC on it.

As for cranks if you can find the spectra 152mm cranks, they're fairly light, but they seem to be gone from ebay and they do use the stock square taper BB. Pictured with 32t SNW ring and light bash guard for 1x setup.










If you have a 68mm BB, the GT SPEED AL GXP crank comes anywhere from 135mm - 165mm or the SRAM NX 155mm GXP would be my picks. Both are going to come in around 700g with a 32t ring and a GXP BB. I have the NX on another build and it's a very solid crank for the price, works with 73mm BBshell, both are 1x only though.

The real key to really opening up upgrade options is a rear wheel that will accept a standard cassette. You'll have a ton more options for the drivetrain this way, 1 x 9 is working great for us, an older rapid rise rear derailleur is almost made for kids, extremely smooth shifting paired with a XT M770 shifter.


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## lidation (Jun 16, 2010)

Thanks for sharing. The frame weight is not too bad at 2.9lbs.



ghabe said:


> I picked up an 11 inch ~2009 Specialized Hotrock 24 A1 FS frame yesterday. I will be building it in the coming weeks. I know it's a different model than the one from lidation, but it weights 1.309Kg or 2.89 pounds if that helps anyone:
> 
> View attachment 1105513
> 
> View attachment 1105512


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## GrayJay (May 16, 2011)

1309gr is a good starting weight for the frame. I think the specialized "A1" frames are strait gauge tubing instead of butted however there are few few kids frame that are made from (marginally lighter butted) tubing. I think that Scott was one of the few that offered butted tubing kids frames that were maybe 100gr lighter but the difference is not big if you consider that the frame weight is only about 10% of the the complete bike weight. For example, I built up a 1420g trek MT220 (24" wheel) frame into a 20lbd complete front suspension bike, mostly comprised of parts bin recycled components and free of any titanium or carpet fibers; 
http://forums.mtbr.com/families-riding-kids/trek-mt220-24-mod-build-894279.html


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## ghabe (Mar 7, 2015)

GrayJay said:


> 1309gr is a good starting weight for the frame. I think the specialized "A1" frames are strait gauge tubing instead of butted however there are few few kids frame that are made from (marginally lighter butted) tubing. I think that Scott was one of the few that offered butted tubing kids frames that were maybe 100gr lighter but the difference is not big if you consider that the frame weight is only about 10% of the the complete bike weight. For example, I built up a 1420g trek MT220 (24" wheel) frame into a 20lbd complete front suspension bike, mostly comprised of parts bin recycled components and free of any titanium or carpet fibers;
> http://forums.mtbr.com/families-riding-kids/trek-mt220-24-mod-build-894279.html


My frame has "double-butted and formed DT/TT, externally relieved HT and forged dropouts w/ replaceable hanger and disc mount", according to Specialized. Still, most aluminum rigid frames this size will most likely weight within +/- 10%, which I agree with you, will have limited impact on the total weight of the bike.


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## tofubeats (Dec 10, 2021)

ghabe said:


> I picked up an 11 inch ~2009 Specialized Hotrock 24 A1 FS frame yesterday. I will be building it in the coming weeks. I know it's a different model than the one from lidation, but it weights 1.309Kg or 2.89 pounds if that helps anyone:
> 
> View attachment 1105513
> 
> View attachment 1105512


I'm in the same project these days and the 2016 version of 24 inch 7 speed Hotrock frame weighs 1804 grams 😖
This bike:








I wonder if other versions became closer to 1300 grams like the XC disc, 21 speed etc.

As I check closely, this one has a kick stand plate.
Maybe the one's without are lighter, there is one for cheap with similar design, maybe will have a look...


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## Darth Lefty (Sep 29, 2014)

The only worry the frame should give you is about geometry. It’s pretty well featured and sturdy. Not heavy enough to complain. But it’s kind of more like a rugged hybrid than a mountain bike.

But the components, Jesus. Check out what the rear wheel assembly or all the crank parts or the coil spring / steel stanchion fork weigh


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## tofubeats (Dec 10, 2021)

Darth Lefty said:


> The only worry the frame should give you is about geometry. It’s pretty well featured and sturdy. Not heavy enough to complain. But it’s kind of more like a rugged hybrid than a mountain bike.
> 
> But the components, Jesus. Check out what the rear wheel assembly or all the crank parts or the coil spring / steel stanchion fork weigh


Sure I tell the same myself 😊

I've spent more money to save half kg earlier many times but I'm unsure this time if other years would be lighter, and definitely geometry looks better like shorter chainstays, slacker headtube than the XC models so will start with this frame. Maybe will buy a NS Clash JR frame once it will be back to stock, also 1.9 kg 🤨


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