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Discussion Starter · #1 ·
I have a 2007 Santa Cruz Chameleon with a 68 mm bottom bracket (I think) and I am installing a Tru Vativ Stylo 3 ring crank. My reading of the install sheet indicates one spacer per side for the external bottom bracket. Just wanted to make sure I'm reading it right. I have 3 spacers that came with the crank. Presumably the spacers are 2.5 mm and one per side makes the bottom bracket width 73 mm. I have it set up this way and I'm having some trouble getting the front der. dialed in. Seems like I might need two spacers on the drive side.
 

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Discussion Starter · #3 ·
Thanks

mtnbiker72 said:
One spacer per side is what I run with a 68mm BB, I had issues getting a SRAM (go figure, same company) X-7 dialed to the 51mm chainline, but replaced it with a Deore that works perfect.
Thanks for your response! Can I safely assume that the spacers that come with the crank are all 2.5 mm?

BTW: I'm using a Sram x9 front der.
 

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One of my bikes is a 68 the other is a73.68 is one washer non drive side two washers on drive side.73 is one washer on drive side.
 

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Yep, one on left, two on the driveside is what Shimano suggests for 68mm BB.

However, I just took one off of each side of my BB last night since my bike had a lot of room between the chainstay and the chainrings and arms. I had to also remove the plastic center spacer to do this, but everything seems okay. I figured since I had the space, might as well get the pedals in a bit.
 

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LuizSalles
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drew502 said:
I have a 2007 Santa Cruz Chameleon with a 68 mm bottom bracket (I think) and I am installing a Tru Vativ Stylo 3 ring crank. My reading of the install sheet indicates one spacer per side for the external bottom bracket. Just wanted to make sure I'm reading it right. I have 3 spacers that came with the crank. Presumably the spacers are 2.5 mm and one per side makes the bottom bracket width 73 mm. I have it set up this way and I'm having some trouble getting the front der. dialed in. Seems like I might need two spacers on the drive side.
If I undestand correct..... you will need two spacers, one in the right and other on left...

I use one Sworks HT (68mm) with one truvativ noir, and have two spacers to go with 73mm
 

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I would SERIOUSLy check that you managed to tighten the pre-load on the cranks enough that they aren't moving side to side. I made this same mistake years ago whne I first started and although it seemed good enough when I finished, once I took it out for a ride and came back it was moving side to side enough to have caused issues if I hadn't fixed it. Just remember that the splines are only so long and need "X" distance between them to not have the crank armed butted and not touching the BB.

In my experience with Shimano cranks and a 68mm BB I have found that you can pretty much remove 5mm of spacers from the setup and it will still let the crank arm not butt, HOWEVER, to get the proper pre-load on the arms I have had to use a threaded rod because the spindle sticks out of the non drive side too much to let the pastic pre-load screw tighten enough.

Wheelspeed said:
Yep, one on left, two on the driveside is what Shimano suggests for 68mm BB.

However, I just took one off of each side of my BB last night since my bike had a lot of room between the chainstay and the chainrings and arms. I had to also remove the plastic center spacer to do this, but everything seems okay. I figured since I had the space, might as well get the pedals in a bit.
 

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Hey Lynx, thanks for the heads-up.

How did you know your's didn't have enough preload? Did the entire crank move back and forth? Or did the left arm develop a wobble?

Bummer if it doesn't work... I hoped that I found a cheap way to reduce the Q-factor by 5mm.
 

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Wheelspeed said:
Hey Lynx, thanks for the heads-up.

How did you know your's didn't have enough preload? Did the entire crank move back and forth? Or did the left arm develop a wobble?

Bummer if it doesn't work... I hoped that I found a cheap way to reduce the Q-factor by 5mm.
I had mine set up without a spacer on the non-drive side, worked fine for oh four years...

Couple of months ago I did the preload up, like I have many times but it just won't take up enough slack, end result I ended up added a spacer back in too make it work...

Can't figure out the reason, unless this bottom bracket bearing is different than the last ones, but that doesn't make sense.
 

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Yup, felt fine at first, but when I got back from a ride I could literally rock it back and forth. The threaded rod makes sure that you don't "ground out" when trying to get pre-load using the normally plastic adjuster - it's the same threaded rod I use to install headsets, so dual use ;) Oh FYI I used wing nuts so tightening was easy and all you really need is finger tight, so using a bolt that requires a wrench isn't a good idea.

Basically what you want to do is install the crank off the bike - left crank arm all the way till it butts on the splines - and then measure the distance between there, then measure your actual BB width, the cups and then you can determine exactly how many, if any spacers are needed or not.

Wheelspeed said:
Hey Lynx, thanks for the heads-up.

How did you know your's didn't have enough preload? Did the entire crank move back and forth? Or did the left arm develop a wobble?

Bummer if it doesn't work... I hoped that I found a cheap way to reduce the Q-factor by 5mm.
 

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Thinking about it further, I believe the only think the spacers do is keep the crankset assembly from moving a bit side to side within the bearings. The bearings themselves support the crankshaft. So, if the crankset can move side to side only about 1mm, I doubt that'd hurt anything.

By the way, when I first installed the crankset, I didn't read the directions carefully and only pressed the crank on with the palm of my hand and then tightened the crankarm bolts. Then I put the little cap on using a dime or something. I didn't put more than 50 miles or so on it, but it wasn't a problem during that time. I can't believe that plastic preset bolt does much. How much can plastic threads do? I'd think that it's just to remove a lot of slack, and that if the crankset moves a bit but not enough to effect the front derailleur shifting, then it's okay.

That's my thought anyway... open and interested in further discussion.
 

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I think you'll get the opportunity to learn a lot if that's your thinking ;) Just think about it for a bit and I'm sure you'll come to realise the whereto's and how's of your thinking. I'll wait and see if you figure it out or need a bit of help :D

Wheelspeed said:
Thinking about it further, I believe the only think the spacers do is keep the crankset assembly from moving a bit side to side within the bearings. The bearings themselves support the crankshaft. So, if the crankset can move side to side only about 1mm, I doubt that'd hurt anything.

By the way, when I first installed the crankset, I didn't read the directions carefully and only pressed the crank on with the palm of my hand and then tightened the crankarm bolts. Then I put the little cap on using a dime or something. I didn't put more than 50 miles or so on it, but it wasn't a problem during that time. I can't believe that plastic preset bolt does much. How much can plastic threads do? I'd think that it's just to remove a lot of slack, and that if the crankset moves a bit but not enough to effect the front derailleur shifting, then it's okay.

That's my thought anyway... open and interested in further discussion.
 

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Straight from Sram's engineering department (and the manual) you only need one 2.5mm BB spacer per side for a 68mm shell. Someone mentioned the super long slots on the spindle interface...this is to allow for an e-type FD with a 73mm setup. It is a little funky, but it does work...especially for a DRS BB mount or XCX setup. It is a neat little feature of the GXP cranksets (the newer 07+ ones).

Shimano uses a slightly different interface where the additional 2.5mm BB spacer is needed.
 

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one spacer per side.

Sram/Truvativ cranks operate differently than shimano/fsa/raceface. The Non-drive side is captured and locked in while the driveside bearing just floats there. That is why there is no preload adjustment or wavy washer on Sram/Truvativ cranks.
 
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