Bicycle Mechanics - Bottom Bracket Spindle Length

I am confused. I always thought that bottom bracket spindle length was determined by what crank you have. I am trying to order a replacement crankset for my bike. (http://www.trekbikes.com/bikes/2004/mountain/4300.jsp)

Here is the crankset. (http://www.bikesmart.com/index.cfm?menu=browse&cid=CRK&ssid=PAOHADKIPEJKGMNG&ap=93.99&StartRow=1)

The sales rep at bikesmart might be bikedumb. He said it doesn't matter about the crankset. It is the derailler clamp size (seat tube) that determines the correct spindle length.

I think it is more a combination of the two. I guess I need to measure the current bike and see what length is in it. I have a 2003 Trek 4300 with the same seat tube and I have a 122.5 in it. But that was the spec that the Suntour crank called for.

The chainline is awesome on that bike. The bike i gave the link to, is the one i am replacing the crankset on. It has always had too short of spindle in it since birth. I have never been able to get enough inward travel out of the front derailler to eliminate run in the inner/inner combo. That tells me the spindle length is too short currently.

I read somewhere that a Deore crankset requires a 113mm BB. Yet it seems like that is about what my current bike has. I guess i will measure it when i get home. So which should i get? 113 or 122.5 or something in between? He told me to get the 122.5 since that is what works well on my other bike. (same frame) Yet I am not convinced.

I am confused. I always thought that bottom bracket spindle length was determined by what crank you have. I am trying to order a replacement crankset for my bike. (http://www.trekbikes.com/bikes/2004/mountain/4300.jsp)

Here is the crankset. (http://www.bikesmart.com/index.cfm?menu=browse&cid=CRK&ssid=PAOHADKIPEJKGMNG&ap=93.99&StartRow=1)

The sales rep at bikesmart might be bikedumb. He said it doesn't matter about the crankset. It is the derailler clamp size (seat tube) that determines the correct spindle length.

I think it is more a combination of the two. I guess I need to measure the current bike and see what length is in it. I have a 2003 Trek 4300 with the same seat tube and I have a 122.5 in it. But that was the spec that the Suntour crank called for.

The chainline is awesome on that bike. The bike i gave the link to, is the one i am replacing the crankset on. It has always had too short of spindle in it since birth. I have never been able to get enough inward travel out of the front derailler to eliminate run in the inner/inner combo. That tells me the spindle length is too short currently.

I read somewhere that a Deore crankset requires a 113mm BB. Yet it seems like that is about what my current bike has. I guess i will measure it when i get home. So which should i get? 113 or 122.5 or something in between? He told me to get the 122.5 since that is what works well on my other bike. (same frame) Yet I am not convinced.The sales rep is a little right and alot wrong. The spindle length spec for that crank is 113 or 118 ocatlink V2,with the longer generally used with 11/4" and larger seattubes. You may have a 122.5 with another crank,but different cranks will have different spiders and require different spindle lengths for the same proper chainline.

Holy Crap! This is amazing.

I just called Alfred E. Bike and you wouldn't believe what went down. I found the crankset i wanted but their site says they don't sell shimano online. So I call them. I get some kid who is waaaaaaaaaay misguided.

I mean i don't know diddly but holy cow! I asked him if a 9 speed crankset would work ok with an 8 speed setup. He said, "no it won't." I said why? He said, i would have to add a couple gears to my hub to get it to work.

I said what does my hub have to do with my crankset? He then said the same thing all over again. Then i told him that a hub is on the rear of the bike and the crankset is on the front. I told him that he was talking about the cassette. "oh, yeah. i am sorry he said."

He then went and asked someone and came back 5 minutes later. "sir, it should work ok, you just need to take a couple links out of your 8 speed chain and you'll be set." WTF???????????

I am certain that you can use a 9 speed crankset with 8 speed shifters and cassette. No? Why is this so difficult? I know, I know, i should go to my LBS. But I can put in my own crankset. I have done it before, when i replaced a like crankset for a like crankset. Now I am "upgrading" and want to make sure i get the right thing!

Can anyone direct me to a Deore crankset with square taper that will work on 8 speed? Thanks.

I know, I know, i should go to my LBS.

Can anyone direct me to a Deore crankset with square taper that will work on 8 speed? Thanks.You have already dealt with the nose pickers at your LBS. Remember the cable incident?..LOL... Any crankset advertized as 9 speed will work with 8 speed.

I believe Harris (http://harriscyclery.net/site/page.cfm?PageID=49&SKU=CR7361) , aka, Sheldon Brown will sell you the Deore you're looking for. AEBike (who I've gotten great service from and have excellent prices) isn't selling Shimano components thru the internet. As I recall, there are only a few places authorized (http://www.cyclingforums.com/showthread.php?t=146781) to sell Shimano stuff on-line.

Whether Harris is one of them or is just thumbing thier nose at em, you're guess is as good as mine.

You have already dealt with the nose pickers at your LBS. Remember the cable incident?..LOL... Any crankset advertized as 9 speed will work with 8 speed.

Good point. I went ahead and ordered this one. (http://aebike.com/site/page.cfm?PageID=30&SKU=CR7366)

I also got a 73 X 113 BB. Seems like it ought to work. Thanks for your help.

Can anyone direct me to a Deore crankset with square taper that will work on 8 speed?

The website you linked to in the original post also sold the square taper version along with the Octalink.

I believe the speed of the crankset is related to the size (width) of the chain and thereby the width of the gear rings. 7/8 speed chains are wider than 9 speed chains. 9 speed chains are wider than 10 speed chains.

Sinch

I believe the speed of the crankset is related to the size (width) of the chain and thereby the width of the gear rings. 7/8 speed chains are wider than 9 speed chains. 9 speed chains are wider than 10 speed chains.

Sinch
Well, actually not. All derailer chains are the same 3/32" inside width and that's what counts the most with chainrings.