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PostPosted: Sat Apr 21, 2012 1:26 am 
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I've just bought a used 2010 Giant TCR Advanced SL 0 Rabobank frameset to build up as a project bike. I'm planning to use 2012 SRAM Red for the drivetrain, and fortunately the frame came with a GXP BB already installed. The frame is BB86, and I can't tell if the bearings I have are steel or ceramic. The bearings bodies are blue plastic, behind the red seals. Google Images shows that there are blue and yellow ones out there, but I can't find any conclusive authority on the matter. Anyone able to shed some light on the issue?


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Posted: Sat Apr 21, 2012 1:26 am 


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PostPosted: Fri Apr 27, 2012 6:16 pm 
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Does it matter? if they run smooth is the issue is it not?

To be fair you have more worrying things to consider with a GXP

Quick fix (and cheap) let me know if you want details


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PostPosted: Fri Apr 27, 2012 11:09 pm 
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Not a performance issue in the slightest, but like everyone I like to know what my machine's built of. No idea what you're talking about with quick fixes.


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PostPosted: Fri Apr 27, 2012 11:33 pm 
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Fair enough I see why you would want to know ;)

I was referring to the non drive side bearing issue that you will have with a Sram GXP bearing set.

The Crank spindle bearing seat does not match accurately enough with the inner of the bearing, meaning that the bearing and spindle "rest" on each others edge rather than where they should, leading to premature bearing failure. If you want it to fit precisely I'll post how, or you can replace the bearings with more GXP ones later on


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PostPosted: Sat Apr 28, 2012 12:19 am 
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Cula, this is very interesting. Please tell us more.

If you could go through the trouble of explaining the problem in detail and then describe how you would fix it, this board would be most appreciative.

Thanks.

Spacepolice, I think you have the standard bearings.

FWIW I have had no issues and the press fit GXP bearing for BB86, (only 3000 km so maybe problem may yet arise). They are also super smooth with not too much bearing drag.

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PostPosted: Sat Apr 28, 2012 9:23 am 
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Sweet, sounds like I should take your advice Cula, but not until AFTER I've ignored your advice, trashed my standard steel BB bearings, and thus given myself an excuse to pimp my bike with ceramics :D Seriously though, haven't heard of this issue with GXP before, would be interested to know your fix, as I'm still waiting for a new wave washer to arrive before I can install my new crankset.


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PostPosted: Sat Apr 28, 2012 9:40 am 
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Mr.Gib wrote:
Cula, this is very interesting. Please tell us more.

If you could go through the trouble of explaining the problem in detail and then describe how you would fix it, this board would be most appreciative.

Thanks

FWIW I have had no issues and the press fit GXP bearing for BB86, (only 3000 km so maybe problem may yet arise). They are also super smooth with not too much bearing drag.


Ok, as you (and others) may or may not know the GXP BB from SRAM is designed to trap the non drive side bearing inbetween the thicker bit of the spindle and the non drive crank arm, this then will stop any side to side movement of the crank and spindle whilst eliminating any risk of of both the internal races from both sides of the BB being pulled together like in some other systems, anyhow in doing so this then created the need for the non drive side bearing seat to be smaller in diameter than the main spindle (to create the Stop or Shoulder as it were for the non drive bearing to butt up against)

Problem with this is that now the spindle is ground to a slip fit for 22mm (21.95) and the supplied bearing is an imperial 7/8ths (22.2)
The bearing with the correct dims are very hard to find, if at all they exist. SRAM say just tighten it up so it connects with the shoulder and it won't move if its got the correct torque value. This imo is a $hit answer and is unacceptable as the precisely ground bearing seat is then unused and all of the force on that side of the crank/bike is resting on less than .5mm radius. They done it properly on the drive side as the bearing (24mm) and spindle difference is 0.05 a nice slip fit (to be fair it SHOULD be a slight interference fit but hey ho)

The next time you have a GXP crank out, pop the non drive bearing onto the spindle and see what I mean about it not fiting right

For your info, I popped into a leading online bike store and spoke to one of their Mechanics (Sorry not going to post who) about this and compared what they had in stock (ALL with the same problems with dimentions standard and Ceramic) and his reply for my solution was "Well if you want a precise fit, you could do it that way"

Funny enough, yes I DO want it to fit precisly. SO these are your options imo

Buy this http://www.chainreactioncycles.com/Mode ... elID=26899" onclick="window.open(this.href);return false;"
You would need to get the correct bearing though to fit, I think a standard hope BB is the right one as this just converts it into a GXP.
Found this thread that might be usefull viewtopic.php?f=3&t=95629" onclick="window.open(this.href);return false;"
I don't know how good the fit is though on any of this (Could be just as bad!?)

Or buy the Truvativ upgrade bearing kit, fitting instructions so you can see the insert collers http://www.enduroforkseals.com/sitebuil ... _rwc_f.pdf" onclick="window.open(this.href);return false;"
Likwise I have not tryed this so do not know what the overall fit is like

Or what I did was buy a 25x37x7 bearing this then fits into the BB and at work turned up a collar to fit exactly
Image

If want to get someone to make it up for them on a cnc I have a dxf to eliminate most of the cost


Hope you get it sorted or don't experience problems


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PostPosted: Mon Sep 16, 2013 3:37 am 
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Wow, I'm so glad I found this. This is the exact problem I am having. Thanks for posting all of the detail on this issue, that custom thing you did seems that it would work well but I don't have access to a lathe.

Just bought an enduro bike and the cranks/BB felt loose. As soon as I removed everything it was evident that the bearing ID was substantially larger than the Crank spindle OD. I figured my BB bearing was just warn out so I went and bought another GXP BB, welp $40 and still the same slop exists.

I don't understand how a reputable bike part company can manufacture such crap??? This should not have this type of fitup problem out of the box.

Not sure what path I am going to take now, probably will just try a different manufacturer altogether. Are there other BB's that can easily work with the SRAM cranks that won't require any trickery to get to fit well? I also have a race face crank/BB setup on my other bike that I may just swap over altogether.

This is frustrating.


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PostPosted: Mon Sep 16, 2013 1:25 pm 
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Location: Toronto
I have been using a TruVativ crank with TruVativ GXP external bearings for years now with no problem, but @Cula's post got me interested to check a spare Truvativ GXP I have. The NDS ID is 22.05mm which sounds about right.

So some questions:

All the NDS GXP bearings/instructions I have seen, use a sleeve to get to the correct ID. The left and right bearings are the same otherwise. So, it sounds like some suppliers are not using a sleeved bearing, but instead substituting a 7/8" bearing. Is that right?

Also in the thread Cula posted, it seemed to me like the OP had installed spacers under the cups, which is a widely misunderstood part of the instructions.

There was another thread very recently about the Hope GXP BB and the video. http://weightweenies.starbike.com/forum/viewtopic.php?f=3&t=118734 That video should be pulled as it shows a "mechanic" hammering the shim into an unsupported bearing. Completely wrong.

My other thought in all this is that perhaps a pressfit BB86 and GXP type crank are really not a good mix. I say this because when GXP first came out it was designed to work with NDS bearings that were firmly held in place by virtue of being screwed into the frame. Clamping the NDS crank then holds everything in place with no preload on the bearings. With pressfit, the NDS bearing is no longer so secure and could move, messing up the original design intent.

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PostPosted: Mon Sep 16, 2013 9:50 pm 
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I think you are correct. I measured my bearing ID to be about 22.22 mm, which is basically .875". There is a plastic sleeve on the drive side spindle/bearing which yields a good snug fit but the NDS has no sleeve to take up the gap.


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PostPosted: Mon Nov 18, 2013 3:39 pm 
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Never had this issue with two sets of GXP cranks, SRAM Red, and Quarq S975 using the standard GXP pressfit 86 bearings in my Scott Foil.

Wavy washer DS, 54nm torque...no issues, and bearing/crank surfaces looks fine after 2500 miles.

With that said though, I've been wanting to try some ceramic, or hybrid ceramic, and enduro has this supposed solution/angler issue resolved on their complete BB kits.

http://www.enduroforkseals.com/id258.html" onclick="window.open(this.href);return false;" onclick="window.open(this.href);return false;


So, thinking of giving these a try just because.


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Posted: Mon Nov 18, 2013 3:39 pm 


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PostPosted: Mon Nov 18, 2013 8:55 pm 
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I now have many thousands of kms on my press fit GXP. Zero slop, zero issues. I have been waiting for it to die but it is as good as the day it was installed. I had shimano press fit in the same bike initially and I prefer the GXP - it feels smoother with less drag.

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Mr.Gib got it right


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