Shimano BB and special small ring conversion?

Discuss light weight issues concerning mountain bikes & parts.

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devinci
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by devinci

I have a press fit BB frame type

I'd like to switch between a X brand crankset and my current sram SRM gxp crankset so I can go 1x for racing and come back to the SRM for training.

My current BB is a sram one so the NDS diameter must be 22mm right?

My question is, what press fit BB would allow me to use a crankset (XTR preferably) and then switch to my sram GXP without changing the BB, but with the use of shimms/adapters?
Last edited by devinci on Mon May 26, 2014 1:17 pm, edited 1 time in total.

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shoopdawoop
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by shoopdawoop

I'd look at Chris king pf24 mountain, which is xtr compatible I believe, and conversion kit #6 for the gxp.

by Weenie


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shoopdawoop
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by shoopdawoop

Edit- Tap talk double post fail

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devinci
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by devinci

thanks for the suggestion

any other possibilities?

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devinci
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by devinci

are there any shimms that would fill the space of the sram spindle into a shimano press fit BB? I recall having some kind of ring here in my part box, which was going on the spindle end in a BSA BB, but I dont remember the BB model and brand

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devinci
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by devinci

I think I have a solution, but I need to know if you guys think it will work.

Currently using a press fit GXP BB with a sram GXP crankset.

Planning on buying a shimano press fit hollowtech II BB with a XTR crankset.

I want to install the shimano BB and use both crankset.

Now the thing is... I have this little ring here, which was on the NDS end of my old sram XX crank spindle. It measures exactly 22mm diameter and the outer diameter is 24mm and fits right into a BB hole on the NDS. I recall it was on my old vertez 26in, which was probably using a third party BB (or maybe a shimano one) with the old sram XX cranks.

So, with a press fit hollowtech II, do you think I will be able to swap cranks with this little ring on the NDS end of my current sram cranks?

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devinci
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by devinci

anybody?

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bikerjulio
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by bikerjulio

I have a GXP crankset bought about 10 years ago.

Back then, the TruVativ NDS bearing was sleeved down to 22mm, but the catch is, it was a press-fit sleeve. So not something you can casually pop in and out.

If your sleeve is a slightly lighter fit that will go in by hand, then yes the solution may work. The GXP crankset would also need spacers on the DS to eliminate any side to side play.
There's sometimes a buggy.
How many drivers does a buggy have?

One.

So let's just say I'm drivin' this buggy...
and if you fix your attitude you can ride along with me.

http://www.youtube.com/watch?v=GekiIMh4ZkM

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devinci
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by devinci

yes the little sleeve is removable, it fits right on the tip of the spindle and leaves enough spindle to be threaded to the NDS arm.

I have a wave washer and a small plastic spacer for the DS GXP crank.

So I assume buying the press fit shimano BB for 92mm frames would allow me to swap between XTR and GXP crankset back and forth with the small sleeve!

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743power
Shop Wrench
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by 743power

You're forgetting an important aspect of the gxp system. The NDS bearing and spindle interface is unique. The inner face of the NDS bearing must press against the end of the 24mm portion of spindle. This allows the inner race of the NDS bearing to be captured on both sides. You can account for BB shell tolerances with a wave washer on the DS spindle. If you look at your GXP BB, you will notice the widths of the bearings are different as well, not just the I.D.'s.

In theory it would be possible to make your idea work, but it would take a bunch of washers and experimenting.
"Any intelligent fool can make things bigger, more complex, and more violent. It takes a touch of genius -- and a lot of courage -- to move in the opposite direction."

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devinci
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by devinci

*f##k* those stupid standards

I guess it will mean no more SRM for racing season then, unless there is another alternative?

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bikerjulio
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by bikerjulio

Not sure I completely agree.

Yes, the original design intent of the GXP was to capture the crank at the NDS bearing and allow the DS to float. But this was also back in the days of threaded BB's. Which nicely held the crank in place.

With pressfit bearings this is not quite as true, hence the need for spacers etc on the DS to prevent the crank trying to walk out of the frame.

So the end result is similar in principle to the way a BB30 crank is located.

As for bearing width I thought they were the same. I know that I converted a shimano spec NDS bearing to GXP by simply pressing in a sleeve.
There's sometimes a buggy.
How many drivers does a buggy have?

One.

So let's just say I'm drivin' this buggy...
and if you fix your attitude you can ride along with me.

http://www.youtube.com/watch?v=GekiIMh4ZkM

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devinci
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Joined: Sat Jan 03, 2009 9:43 pm
Location: Canada

by devinci

yes thats what I mean, a sleeve!

The little ring im refering to is a sleeve to reduce the NDS bearing inner diameter to 22mm

by Weenie


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