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Discussion Starter · #1 ·
So the threads on my Bushnell ebb are shot. Also ruined a King bb. I have to replace, and just want to do what I can to make sure the problem gets sorted.

Background: Had my LBS Install Sram cranks with the GXP bb. Bushnell was previously installed in the bike when it came to me. Rode the bike for a few weeks, noticed looseness, and turns out the left external cup had backed out. Had the LBS check the Bushnell and the threads there seemed fine. Put a King bb in. Rode that for months. Took bike to a different bike shop to have the bike overhauled. Cranks got pulled and the left side of the Bushnell and the King were both rounded out. So much so that the King cup could slide right in and out of the Bushnell, even though the threads are still there. I guess the crank was just holding it all together.

Any guesses as to why this would happen with two different external bottom brackets? Most likely the Bushnell was somehow damaged previously, but I guess there could also be the issue of whether proper torque was applied when the external was installed.
 

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Trail Tire TV on blogger
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Well it happened most likely because those EBB's aren't made to work with GXP BB well. the threads and area around the actual BB cup mounts are too thin/weak, especially if using the ultra light version that has even smaller threaded/contact point. Plus it was probably loose adding to the issue.
GXP puts all the side to side movement control and pressure on the non drive side bearing.. the drive side just floats on the spindle and has close to zero stress on the threads allowing it to take the extra backward pull from the chain. Then add the King BB which though they are decent BB they use a poor method of adapting the GXP to a shimano style side clamp mounting and you have the makings of a disaster.

The GXP BB is a superior BB design, but if your sticking with a EBB it's going to give you issues. Personally I'd get rid of the EBB as they just add one more area of weakness in one of the highest stress section of the bike. But if you're dead set on it get Shimano cranks that squeeze the bearings for the sides.

if you don't get what I'm talking about with the GXP BB.. once again I'll point to this write up on how they work..

Trail Tire TV: Sram's GXP Bottom Bracket, how it differs from others
 

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I've never had an issue with GXP and my EBB. I've used a solid type with a set screw and GXP worked perfect. I've used the Carver EBB and again, GXP worked perfect. Now, i use the Niner Biocentric II and still perfect.

Maybe they are being over torqued on installation. They really don't require a massive amount of tightness to install since the spindle bolt keeps it all together.
 

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Trail Tire TV on blogger
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I've never had an issue with GXP and my EBB. I've used a solid type with a set screw and GXP worked perfect. I've used the Carver EBB and again, GXP worked perfect. Now, i use the Niner Biocentric II and still perfect.

Maybe they are being over torqued on installation. They really don't require a massive amount of tightness to install since the spindle bolt keeps it all together.
Look at the mounting or threaded area of the standard Bushnell against the Carver EBB,.. the Carver has a LOT more area(threaded face) than the Bushnell.

never played with Niner's. But almost everyone I've known that has owned one has liked the concept, hated the actual practice. Creaks, slips, has issues.. Though I will say I've used my plumbers tape trick on the threads and it helped a LOT with the creaks..

I honestly can't think of anyone I know who still has an EBB. :roll eyes: thinking...:roll eyes: thinking,... nope, no one. I do think in the right terrains/ride styles they will work fine.
 

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Discussion Starter · #6 ·
I understand the potential issues folks would have with an ebb, but I'm stuck with it. At least I didn't strip out the bb area on a frame. I had zero issues with slippage or creaking on mine. Just the issues mentioned in my OP. Now Bushnell makes both a featherweight and a "retro" version of the ebb. The retro version weighs more. Thomllama mentions that the threads might be better on that model. I have to agree with Thomllama about how "meager" the threaded area on the Bushnell seems. However, the Bushnell also has about the best reputation in the ebb business. I will email Bushnell and get their thoughts because someone there already e-mailed me to say that the retro seems to have less issues with slippage than the featherweight, but didn't mention anything about the thread area.

When I put the GXP in, I researched all the threads mentioning how finicky the bb is and some folks mentioned that the non-driveside cup had issues staying tightened. May have nothing to do with my problems, but it's interesting. I'm also a clyde and putting lots of pressure on the area, and yet I also know there are many, many riders of heft using the Bushnell without issue. Maybe I'll use the retro and switch to Shimano cranks just for piece of mind. I just want to do everything I can to keep it from happening again. Including eliminating user errors…which may not be totally possible.
 

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Trail Tire TV on blogger
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Honestly, if you go with the "retro" EBB , use Plumbers tape on the threads of the BB cups into it, and use a BB that is MADE for GXP you will be fine.
some points...

The Retro has more threading.. I'm just guessing here but the low thread it's self wasn't the sole issue, it was added to by the cups loosening, add the stress of you pedalling and the 2 together is what made them strip.

Plumberstape will hold them from loosening.. NO it's not a lubricant,.. (everyone thinks that do to Dupont's "teflon" brand name) It's actually made to fill and tighten threads sealing it from water leaks.. but filling and tightening helps hold threads in place.. better than Locktite.. as it works on each and every thread instead of trying to glue a small area.

Sell the King BB, they are decent BB's but the adaptor they use to convert to GXP is a poor design. Get a quality one like Real World Cycling's that is made for the GXP.. avoid the SRAM stock ones as the bearings in them are crap. You could use them, just plan on replacing it regularly if you do use SRAM's.. My Real World cycling ceramic BB is out lasting the cranks it holds. With regular maintenance it will last you years. I take the cranks off, clean and re grease the out seal 2 times a yr.. it's like 5 years old.

again.. I MUCH prefer the GXP bottom bracket design. It's better for the bearing, keeps them square on the races, wears the drive side less by transferring the extra side forces to the non drive side.
 

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Discussion Starter · #8 ·
Honestly, if you go with the "retro" EBB , use Plumbers tape on the threads of the BB cups into it, and use a BB that is MADE for GXP you will be fine.
But the first external bb I stripped out on the left side was the GXP that comes with SRAM cranks. I had the King in the parts bin, so I bought the adaptor to give the King a try. I knew about the adaptor being not an ideal match, but I thought the first GXP stripping was a weird happening and didn't expect the problem to reoccur.

The costs will be similar whether I switch to Shimano or purchase the more expensive Sram bb. I'll have to keep weighing my options. I really appreciate your POV. I'll talk with the Bushnell people and see what they have to say as well.
 
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