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  1. #1
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    Hotrock 20" coaster bike upgrades

    Just picked up a used Hotrock 20 for my growing 6 yr old son. It appears to be the 2013 model (current design) and I decided to go with the lighter solid fork version. While the bike cosmetically seems to be in great shape, there is some noise coming out of the coaster brake while spinning forward under weight. Will try to repack the bearings this weekend. Also I'm considering possibly rebuilding or replacing the bottom bracket. Could someone tell me what size bb should I be looking at? The 6sp version has it spec'ed 68mmx128mm, but the coaster version does not list the size. Could the crank size also be different between the two models? (Ours is 115mm). Final question - when my son is ready for gears, would it make more sense to buy another Hotrock with gears or try upgrading this one?

    Happy cycling!
    --Rob

  2. #2
    CJH
    CJH is offline
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    Quote Originally Posted by ne0en View Post
    Could the crank size also be different between the two models? (Ours is 115mm). Final question - when my son is ready for gears, would it make more sense to buy another Hotrock with gears or try upgrading this one?
    Pretty sure the two Hotrock 20's have different crank and bb setups from each other. The coaster model is more like the coaster 16 and will require an adapter to fit a lighter, three piece.

    The 20 coaster should only have 110mm rear hub spacing so adding gears is not as easy as a new hub/wheel setup.

    I think a few builds here have squeezed in a few gears or added a three ring crank up front. I think it's better to get a geared bike and maybe keep the coaster model for dirt jump park or jumps out on the driveway or whatever.

    All of my advice is coming from faint memories. If we get the expected cold, rainy weather here I may see if I have some old threads bookmarked on another computer.

  3. #3
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    Does the newer 20" bike with coaster brake still have the one piece crank? It looks like it, on the Specialized site it says "Steel, OPC Ball retainer type" There's a kit you can buy that converts that type of bottom bracket shell to use more mainstream bottom brackets (like the one on the 6 speed hot rock). You can search for Truvativ american to euro converter. I haven't tried one of these, because we need gears so I just move to a 6 or 7 speed with 135mm spacing in the rear.

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