Looking for parts and info


I got a Specialized Hardrock for really cheap but it’s in worse wear than I first thought. The front chainring teeth are bent and I need a new rear derailleur. The cassette on the rear tire seems fine. Its 3x7 and I dont really understand what size of front chainrings to buy or how to make sure they’re compatible with the crank and the rear cassette. Also the the front derailleur is a shimano SIS and im not sure if theres a specific rear derailleur that I need to make sure it’s all compatible.

Im looking at used parts and really just looking for direction to get it up and running if anyone has any advice or can point me to some good info online. I was thinking of taking it to a bike shop but I would prefer to learn how to do things myself


As long as your rear mech is the same number of speeds as your cassette and shifter youre ok. Front chainrings can be had dirt cheap on Jensen USA. I would check out RJ the Bike Guy on YouTube. He rebuilds a hotrock on his channel I’m certain.


Count the teeth on your chainrings or look for a label to know what size you need. Also the number of bolts for the crank. Are you sure it’s 7-speed in the rear? Count the number of cogs on the cassette. It could be 7, but that’s really old. 8-speed was pretty common in the late nineties, 9-speed from 2000-up. If it really is 7, you need a 7-speed-compatible rear derailleur.


On bikes like the HardRock, you often get chainrings that are pinned to the crank and can’t be individually replaced, so you’ll need to make sure that isn’t the case before you buy anything there. Can they be individually unbolted? If so, the bolt circle diameter (BCD) will be stamped on the chainring (one of the more common sizes is four bolts with a 104mm BCD, for example). If they’re badly bent and the chainrings can;'t be removed, you’ll potentially need a new crankset, which may be easier to find used than just the rings themselves, but you will need special tools to remove the old one.


As an fyi… Bike Pedaler has been great to me before for sourcing recycled parts. Its a fun place to visit as well lots of cool referb’ed bikes and parts.


Second to recommend bike pedaler. Fantastic prices, great service and tons of second hand parts. Theyll also show you everything going on and help you understand anything youre confused about. Cant praise them enough. I learned a lot by stopping by with any kind of issue big or small


I checked the cassette and it is 3x7. I looked online but couldn’t figure out the year. Im going to fix the bike for my daughter since the frame is 15". I thought the middle chainring had cracks in it but I noticed 3 of the same splits so I dont know if they’re meant to be there but I think it needs to be replaced anyway since some of the teeth are rounded off. I’m going to take it to work today to take it apart since I dont have the tools at home. The derailleur snapped off at the hanger and is all bent.

I went to the bike peddlar for parts for 2 single speed bikes I built and they gave me great prices. That’s where I would be going to for help for sure.


Chainring looks to be removable. Is the rear hanger still good?


No the rear hanger snapped in two. I don’t have a crank puller but I soaked the crack in PB blaster and tried to hit it off with a block and hammer but it’s not budging. With this type of crank all I need to do is take out the bolt and pull it off right?


Square tapper crank puller. You need a puller. Where are you located I have one here you could use.


Thanks but I’m actually going to go a different route with it. I actually sold my crank puller a couple years ago cause I didnt think I’d get back into biking :frowning:


I have an old XTR front derailleur that you’re welcome to, if it fits. It was a weird type that mounted on the bottom bracket. Carbon, too!


Thanks but the front derailleur is fine. I was going to swap the fork from the hardrock to my GT (xct v2 vs m3010) but once I got everything apart I realized the steerer tube was too short.


Not sure what you mean by going a different route, but one of these will probably take the crank off quickly:

@TheGOAT 's or you could borrow mine.

Not sure about hammering it off. That might damage your bottom bracket. :slight_smile:


Likely will not come off by beating it. Unlikely anyways.