# Damaged crank gear... replace entire thing?



## Mikey_Dawg (Apr 21, 2009)

I guess I hit a rock or something tonight but I jacked my small ring bad tonight on my crank... a couple rotations later and I put some scrathes / gashes in my frame/chainstay around the crank as well.

1. Do I have to replace the entire crank or can I just replace the triple chainring (I believe that is the correct term) ? ( the stock crank is SR Suntour XCC-T102 42/34/24 if that helps)

2. I know the pics are hard to decipher but are the scratches on the frame anything to worry about (aside from the fact that it looks bad - if you get real close to actually see them) ?

Thanks for the help...


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## frdfandc (Sep 5, 2007)

The gears are called chainrings. And yes, you will need to replace the entire crankset. The crankset on your bike has chainrings that are riveted together. They do not have removeable chain ring bolts.


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## Mikey_Dawg (Apr 21, 2009)

Would either of these work?? Is this a pretty simple DIY job??

http://directbicycleparts.com/page.cfm?PageID=53&action=details&sku=CR3388&utm_source=froogle&utm_medium=na&utm_campaign=froogle

http://directbicycleparts.com/page.cfm?PageID=53&action=details&sku=CR8272&utm_source=froogle&utm_medium=na&utm_campaign=froogle


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## pogliaghi (Oct 26, 2008)

You need to replace the whole crankset. You have riveted chainrings. Time to upgrade, get a square taper crankset with bolt on chainrings. It'll cost you around $50 from online stores, cheaper on eBay or Craigslist. The gouge on the BB shell appears superficial, I wouldn't worry about it.


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## Dremer03 (Jun 19, 2009)

I would stay away from both of those. They are both cheap, and riveted and you will have the replace the whole thing if you bend another chain ring. I would go with a bit more expensive piece that has replaceable chain rings.


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## Mikey_Dawg (Apr 21, 2009)

Vtolds said:


> I would stay away from both of those. They are both cheap, and riveted and you will have the replace the whole thing if you bend another chain ring. I would go with a bit more expensive piece that has replaceable chain rings.


What would you recommend then?? I assume the 24//34/42 are the sizes for the current chainrings... do I have to upgrade to another crankset with the same sizes?? Thanks...


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## pogliaghi (Oct 26, 2008)

Your chain is setup for a 42t big ring, the $50 cranksets are 44/32/22. You'll need a new chain. But considering the damage to the chainrings and the BB shell, I would recommend replacing the chain anyways. Depending on your area, a 22 granny may be helpful, you'll be able to climb steeper stuff.


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## Dremer03 (Jun 19, 2009)

If you like your gearing now, you can most certainly find those same rings on a newer crankset with bolted on chain rings but you dont have too you could go with different sizes. You could even change out the BB while you are at it, way more choices out there if your willing to upgrade from square taper.


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## grivooga (Mar 14, 2009)

Most chains on cheap bike are atleast two links (I've seen 4-6) too long so you may not need to replace it if you go up two teeth in size but it's something to be careful about. Check the chain for twisted links and see if it's stretched (12 links should measure less than 12 1/16") before reusing it. Chains are reasonably cheap and a worn out chain will eat up new chainrings and cogs.

Ridiculously thorough info on chains by Sheldon Brown


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## Mikey_Dawg (Apr 21, 2009)

Vtolds said:


> If you like your gearing now, you can most certainly find those same rings on a newer crankset with bolted on chain rings but you dont have too you could go with different sizes. You could even change out the BB while you are at it, way more choices out there if your willing to upgrade from square taper.


I read that the ISIS standard would be a good upgrade from the square taper. From what I can tell a new ISIS BB would cost around $30-40. Does that sound about right? I have been doing some google shopping for "ISIS BB" and "ISIS Cranksets" etc. and have come across brands such as Truvativ, FSA, and even see that Nashbar has a BB but don't have a clue what a good/inexpensive option would be ... same goes for the cranksets... any specific recommendations or guidance would be appreciated. Thanks for the help.

Also - I am riding a 2009 Trek 4300... I really dont want to dump a ton of money into a new BB / Crankset since I will ugprade bikes in a few years so if my best option is to get a decent square taper crank then I am fine with that option. Still would love a couple recommendations to check out if you have any suggestions...thanks.


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## Mikey_Dawg (Apr 21, 2009)

Maybe something like this:

http://www.universalcycles.com/shopping/product_details.php?id=15800

or

http://www.bikeman.com/CR7274.html?utm_source=GoogleBase&utm_medium=GoogleBase&utm_campaign=GoogleBase

(If I decide to stick with square taper - I beleive both of these have removable chainrings)


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## Dremer03 (Jun 19, 2009)

Mikey_Dawg said:


> I read that the ISIS standard would be a good upgrade from the square taper. From what I can tell a new ISIS BB would cost around $30-40. Does that sound about right? I have been doing some google shopping for "ISIS BB" and "ISIS Cranksets" etc. and have come across brands such as Truvativ, FSA, and even see that Nashbar has a BB but don't have a clue what a good/inexpensive option would be ... same goes for the cranksets... any specific recommendations or guidance would be appreciated. Thanks for the help.
> 
> Also - I am riding a 2009 Trek 4300... I really dont want to dump a ton of money into a new BB / Crankset since I will ugprade bikes in a few years so if my best option is to get a decent square taper crank then I am fine with that option. Still would love a couple recommendations to check out if you have any suggestions...thanks.


Actually I just upgraded to Isis with a Truvativ Isoflow Crank and I like mine, but mine came of a stripped Rockhopper I am not sure where you can buy them currently. Pricepoint has this nice pack deal http://www.pricepoint.com/detail/16...6-Cranks/Bolts/Race-Face-Ride-XC-Crankset.htm You will need the tool to remove the old bottom bracket and the tool to install the new one. And you will need to make sure your old bottom bracket is 73mm otherwise it will not work. So I guess my suggestion is for you time figure out what size yours is then we can better help determine what exactly you need.


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## pogliaghi (Oct 26, 2008)

Mikey_Dawg said:


> http://directbicycleparts.com/page.cfm?PageID=53&action=details&sku=CR3388&utm_source=froogle&utm_medium=na&utm_campaign=froogle
> 
> http://directbicycleparts.com/page.cfm?PageID=53&action=details&sku=CR8272&utm_source=froogle&utm_medium=na&utm_campaign=froogle


Either one of the above would work, but both are marginal cranksets with riveted chainrings. Besides having a fixed chainrings that you cannot replace, the bigger problem is that chainrings on cheaper cranks, as you have experienced, are not very strong. Good cranksets have strong replaceable chainrings. They're strong to take the abuse, and replaceable because they can be damaged (rock vs. ring) and they definitely will wear out.

I forgot to mention that crank arm length is also an important measure to note. Going from 175mm down to 170mm is a significant enough change for some to notice.


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## pogliaghi (Oct 26, 2008)

Mikey_Dawg said:


> What would you recommend then?? I assume the 24//34/42 are the sizes for the current chainrings... do I have to upgrade to another crankset with the same sizes?? Thanks...


Actually, 24/34/42 is a bit of an odd size. Standard MTB cranks tend to come with 22/32/42 or 22/32/44 rings. Chain length is what you'll need to watch out for if you go to 44t. Considering the damage in your pictures, I would replace the chain anyways, chain pins are pressed into a very narrow plate, they don't handle lateral flexing too well and from the position of your granny, your chain must have sustained some serious flexing.

You also need to consider crank arm length.


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## pogliaghi (Oct 26, 2008)

Mikey_Dawg said:


> I read that the ISIS standard would be a good upgrade from the square taper.


Isis is good, but given your consideration, not wanting to put too much money into this repair, I would go with the square taper. Buy crank, tightened it down, works just fine. I rode with a square taper for many years.

If you really want to upgrade your BB, then consider Vtold's recommendation, an excellent and not overly pricey upgrade.



Vtolds said:


> Pricepoint has this nice pack deal http://www.pricepoint.com/detail/16...6-Cranks/Bolts/Race-Face-Ride-XC-Crankset.htm You will need the tool to remove the old bottom bracket and the tool to install the new one. And you will need to make sure your old bottom bracket is 73mm otherwise it will not work. So I guess my suggestion is for you time figure out what size yours is then we can better help determine what exactly you need.


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## Mikey_Dawg (Apr 21, 2009)

I went ahead and bought a Shimano Alivio M410 Crankset from the LBS and the Park Tool crank remover as well so I could go ahead and knock this job out tonight. At least I can replace any specific chainring going forward if I bend one again - thanks for all the help guys.


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## Dremer03 (Jun 19, 2009)

Literally should take you a matter of minutes to replace, very simple to do.


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