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Singlespeed & Fixed Gear "I still feel that variable gears are only for people over forty-five. Isn't it better to triumph by the strength of your muscles than by the artifice of a derailer? We are getting soft...As for me, give me a fixed gear!"-- Henri Desgrange (31 January 1865 - 16 August 1940)

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Old 08-29-12, 09:04 AM   #1
Blackguyrides
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SRAM Omnium Cranks and Leader 735 Problem!

Hey all,

So this morning I installed my Omniums on my new 735 and it looks like the crank arms are about to touch the bottom chainstay. Are there spacers I can get for these to make them a bit further away from the chain stay or is this how it's supposed to be. I know they're going to hit once on the road from flex. Is this normal? If there's any specific spacers to get for these cranks let me know, i'm going to head to the shop so they can give me an opinion as well.



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Old 08-29-12, 09:16 AM   #2
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looks fine- try it out and see how it goes. i would love it since the q factor is nice and low
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Old 08-29-12, 09:18 AM   #3
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Omniums are stiff as hell, and those wide aluminum chainstays are stiff as hell.

Doubt you'll have issues, but if you eventually do, I believe they make spacers.
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Old 08-29-12, 09:29 AM   #4
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There's nothing wrong with that at all. The clearance on my Dodici Gara with Sugino 75s is probably less than that and I've never had an issue with the arms hitting the frame.



FWIW - those spacers aren't for increasing Q-factor or adjusting chainline.
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Old 08-29-12, 09:44 AM   #5
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You can't randomly space an external cup crankset like Sram/Truvativ or Shimano. The bottom bracket/crank combo is designed for a certain width bb shell and/or number of spacers. In the case of Omniums, it is designed for 68mm shells with no spacers. By adding spacers, you're preventing the non-drive side crank from bottoming out on its stops against the bearing and not seating fully. This is bad.

Re: spacers, usually mtb cranksets come with a couple of spacers for use w/ 68mm bb shells when the cranks are also compatible with 73mm shells. For example, Shimano hollowtech 2 mtb cranks use 2 spacers on the drive side and one on the non-drive side when used w/ 68mm shells. When used with 73mm shells, you only use one spacer on the drive side, and none on the drive side. You can switch them around to move your chainline left or right, but you need to use the recommended amount of spacers for your given crank/frame combination. Read your bb and crank manual.

IIRC, Sram GXP cranks, for both road (Force, Red, Apex, Rival) and track (Omnium) are designed to use 68mm English or 70mm Italian bb shells (using the correct BB) and no spacers.
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Old 08-29-12, 09:49 AM   #6
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Originally Posted by FKMTB07 View Post
You can't randomly space an external cup crankset like Sram/Truvativ or Shimano. The bottom bracket/crank combo is designed for a certain width bb shell and/or number of spacers. In the case of Omniums, it is designed for 68mm shells with no spacers. By adding spacers, you're preventing the non-drive side crank from bottoming out on its stops against the bearing and not seating fully. This is bad.
I can't even count how many times I've told people this.
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Old 08-29-12, 10:03 AM   #7
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I can't even count how many times I've told people this.
I guess in their defense, the generic BB manual that comes with a GXP bb when you buy one by itself is pretty poorly written and sort of confusing. And the bb comes with spacers. Still annoying though.
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Old 08-29-12, 01:02 PM   #8
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I definitely have less clearance than that
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Old 08-29-12, 02:28 PM   #9
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Quote:
Originally Posted by Blackguyrides View Post
Hey all,

So this morning I installed my Omniums on my new 735 and it looks like the crank arms are about to touch the bottom chainstay. Are there spacers I can get for these to make them a bit further away from the chain stay or is this how it's supposed to be. I know they're going to hit once on the road from flex. Is this normal? If there's any specific spacers to get for these cranks let me know, i'm going to head to the shop so they can give me an opinion as well.



It's fine.

If your frame flexes enough for the crank arm to touch you have much bigger problems. That will never happen.
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Old 08-29-12, 03:27 PM   #10
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I've run that kind of clearance on Chro-Mo frames. It'll be fine.
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Old 08-29-12, 05:07 PM   #11
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Quote:
Originally Posted by Scrodzilla View Post
I can't even count how many times I've told people this.
I spent almost an hour trying to convince my boss of this when he was working on some SRAM MTB cranks. He ended up with some number of spacers randomly placed on either side and sent it out the door that way. I facepalmed and just shut up.
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Old 08-29-12, 05:13 PM   #12
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Sram/Truvativ MTB cranks are a different story because - like FKMT mentioned - the BB/spindle is designed for use on a 73mm shell. If the frame has a 68mm shell, the spacers are necessary.

With Omniums or S300s though (which are designed for use on a 68mm BB shell) the spacers shouldn't even be included.
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Old 08-29-12, 05:18 PM   #13
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It did have a 68mm BB, but he ended up with like 3 spacers on the drive side and 1 or 2 on the NDS. It was a messed up setup.
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Old 08-29-12, 05:18 PM   #14
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Hahahaha
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Old 08-29-12, 05:32 PM   #15
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The guy knows about bikes, has been working at this shop since he was 13, but he's not super well-versed in more modern stuff. While he worked on it, he just kept grumbling and *****ing about how ****ty SRAM is. He kept removing the plastic bearing dust shields on either side trying to get it to be right, despite me telling that it's not a spacer, but a dust shield and it's necessary. I just walked away. He eventually got it to roll and shift halfway decent.
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Old 09-14-12, 04:19 PM   #16
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hi, sorry for taking a focus of this thread a little aside. But it's very related question. In a few days I gonna install BB to my new frame. After chasing n'facing (it was a brand new frame) I got BB tube shorter (rated 68mm). Now it is 67 mil. I have integrated BB with external bearing cups. I see two options: use spacers or throw away the shell connecting left and right cups. Some models I know have flexible plastic shells, but mine is made of ceramic and will not compress. I now pass by the question about chainline. Offcourse I'll use spacers if I'd need to correct it. But what if all turn out beautiful, is that plastic part is great of importance?
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Old 09-14-12, 04:38 PM   #17
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You know there's a mechanics forum, right?
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Old 09-14-12, 05:44 PM   #18
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Originally Posted by Blackguyrides View Post
Hey all,

So this morning I installed my Omniums on my new 735 and it looks like the crank arms are about to touch the bottom chainstay. Are there spacers I can get for these to make them a bit further away from the chain stay or is this how it's supposed to be. I know they're going to hit once on the road from flex. Is this normal? If there's any specific spacers to get for these cranks let me know, i'm going to head to the shop so they can give me an opinion as well.
You flatter yourself. Or underestimate your cranks/bike.

I have more clearance on my bike with omniums, less with my S75's on my Leader, which I just installed coincidentally.
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Old 09-14-12, 06:08 PM   #19
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Disregard everybody.
It's hammer time.
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