Praxis works PF30 to GXP

[poita]

So I've had a praxis works conversion BB on my bike for a while now and have had no need to touch it. Recently I was riding along and noticed some play in the BB. For those familiar with the praxis BB, the drive dude cup had started to loosen from the NDS sleeve and was moving around slightly.

I pulled the BB or and had a look, threads send fine and bearings are still perfect. Put it back on the bike exactly as per instructions. Going to fit the crankset and there is a massive gap on the drive side. So much so that the wavy washer is just floating around on the crank spindle and the bearing cover falls off. No matter what I do when putting the spindle into the bearings, I can't get it any further. The NDS crank arm is tightened to spec and sitting hard up against the bearing.

Any ideas? I can see there is a very small lip on the NDS up to the bearing seat, I'm wondering whether I've installed the BB incorrectly and the bearings are not lined up perfectly. Apart from that I'm stumped! Am i missing a spacer?? Or something else?

 

[JTmofo]

So I've had a praxis works conversion BB on my bike for a while now and have had no need to touch it. Recently I was riding along and noticed some play in the BB. For those familiar with the praxis BB, the drive dude cup had started to loosen from the NDS sleeve and was moving around slightly.

I pulled the BB or and had a look, threads send fine and bearings are still perfect. Put it back on the bike exactly as per instructions. Going to fit the crankset and there is a massive gap on the drive side. So much so that the wavy washer is just floating around on the crank spindle and the bearing cover falls off. No matter what I do when putting the spindle into the bearings, I can't get it any further. The NDS crank arm is tightened to spec and sitting hard up against the bearing.

Any ideas? I can see there is a very small lip on the NDS up to the bearing seat, I'm wondering whether I've installed the BB incorrectly and the bearings are not lined up perfectly. Apart from that I'm stumped! Am i missing a spacer?? Or something else?

Photos speak a thousand words.
Fire some up when you get a chance.......

 

[Boom King]

No real idea but because GXP is a stepped shaft, with different diameters on DS and NDS, it sounds like you've got something on the wrong side.

 

[moorey]

Try removing all BB spacers. Can happen on 73mm shell frames in personal experience (with standard gxp threaded BB), due to the step, as BK mentioned.

 

[poita]

Will get photos tomorrow. No spacers on the praxis works BB. All assembled on the correct sides, spindle gets most of the way in, about 15mm more than if bearings were on the wrong side. Think it's probably something unique to the praxis BB that I'm missing

 

[Boom King]

Will get photos tomorrow. No spacers on the praxis works BB. All assembled on the correct sides, spindle gets most of the way in, about 15mm more than if bearings were on the wrong side. Think it's probably something unique to the praxis BB that I'm missing

Rubber mallet?

What happens if you pull the DS cup out and pop it onto the crank spindle?

 

[poita]

Rubber mallet?

What happens if you pull the DS cup out and pop it onto the crank spindle?

Yep, judicious rubber mallet already applied to my limit. And weirdly enough the spindle fits appropriately on each bearing individually which makes me think there's something I'm missing or doing wrong....

 

[poita]

So this is what the assembled BB looks like off the bike. Set to the same width as the BB shell.

And this is what the drive side cup looks like without the NDS bearing etc attached. Gap to chainring is significantly smaller.

I've measured the length of the splines showing with just the NDS bearing fitted and it's the same as when fitted to the bike. So it seems to me that the BB assembly isn't quite wide enough for the cranks. Going to have to dig up the chainring offset for the cranks and see if it's correct with the large gap between the DS bearing and crank.

Any other thoughts? As far as I can tell this is the correct Praxis BB for a PF30 conversion, anyone else use one and have any info?

 

[bear the bear]

So this is what the assembled BB looks like off the bike. Set to the same width as the BB shell.

And this is what the drive side cup looks like without the NDS bearing etc attached. Gap to chainring is significantly smaller.

I've measured the length of the splines showing with just the NDS bearing fitted and it's the same as when fitted to the bike. So it seems to me that the BB assembly isn't quite wide enough for the cranks. Going to have to dig up the chainring offset for the cranks and see if it's correct with the large gap between the DS bearing and crank.

Any other thoughts? As far as I can tell this is the correct Praxis BB for a PF30 conversion, anyone else use one and have any info?

Can you take a photo the same as the top looking at the NDS with the BB compressed against the wavey washer?

 

[poita]

I can, but that's kinda the problem. The NDS bearing is actually all the way against the flange in that picture. The only way of getting the DS bearing up closer to the wavy washer is to inform that part from the NDS sleeve. Can't do that on the bike though because the assembly has to tighten up against the BB shell. So, I either have the wrong BB (unlikely, I've triple checked the praxis application guide), it's actually fine and the ? Seal is supposed to fall off... Or there is a spacer to go over the spindle closer to the crank arm with the wavy washer after it...?

 

[bear the bear]

I can, but that's kinda the problem. The NDS bearing is actually all the way against the flange in that picture. The only way of getting the DS bearing up closer to the wavy washer is to inform that part from the NDS sleeve. Can't do that on the bike though because the assembly has to tighten up against the BB shell. So, I either have the wrong BB (unlikely, I've triple checked the praxis application guide), it's actually fine and the ? Seal is supposed to fall off... Or there is a spacer to go over the spindle closer to the crank arm with the wavy washer after it...?

OK on the same page now,,,,
What is the width of your BB, and the next one is length of spindle.

 

[Nambra]

Might be a dumb question, but are you squashing the o-ring between the NDS cup and the BB shell when installing the cup? It's supposed to be just touching, right? Compressing the o-ring will effectively move the NDS bearing (and crank axle) toward the DS by a mm or two.

 

[poita]

Might be a dumb question, but are you squashing the o-ring between the NDS cup and the BB shell when installing the cup? It's supposed to be just touching, right? Compressing the o-ring will effectively move the NDS bearing (and crank axle) toward the DS by a mm or two.

Yep, supposed to press in the NDS sleeve so the o ring is just touching then tighten the DS bearing until it stops "to correctly set the chain line for PF30 BBs" this compresses the o ring. Looking at how the praxis BB works, and the fact that it loosened off from probably not being tight enough, seems to suggest that the whole thing must always be the same length when tightened to spec. Which then means I've got something weird going on....!

 

[Nambra]

Yep, supposed to press in the NDS sleeve so the o ring is just touching then tighten the DS bearing until it stops "to correctly set the chain line for PF30 BBs" this compresses the o ring. Looking at how the praxis BB works, and the fact that it loosened off from probably not being tight enough, seems to suggest that the whole thing must always be the same length when tightened to spec. Which then means I've got something weird going on....!

Sounds like you know what you're doing then, according to the OEM instructions at least which is all I have to go on. I'm guessing that if the DS bearing is up against the shell and it's still not tight enough, continuing to tighten it will draw the NDS side toward it, compressing the o-ring in the process - effectively catering for tolerance issues in BB shell width.

It's definitely a PF30 BB shell ie. 46mm diameter bore, and you need the PF sleeve to reduce it to 42mm for the BB? And the BB shell is definitely 73mm wide?

 

[Boom King]

Yep, supposed to press in the NDS sleeve so the o ring is just touching then tighten the DS bearing until it stops "to correctly set the chain line for PF30 BBs" this compresses the o ring. Looking at how the praxis BB works, and the fact that it loosened off from probably not being tight enough, seems to suggest that the whole thing must always be the same length when tightened to spec. Which then means I've got something weird going on....!

Wasn't it fitted and working fine prior to you finding it loose?

 

[linkl8r]

On the GXP spindle are you using SRAM red spacers or the black ones supplied by praxis. I haven't worked on one for a year or so but from memory it needed the black spacers as they had a particular aluminium bevel that sat against the bearing.

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[stirk]

Wasn't it fitted and working fine prior to you finding it loose?

What bk said, if it's the same components as were on the bike and working fine before you took them off there is an error in the reassembly.

Pull it all apart completely and lay all the bits out and make sure you all the parts in the right order and start again. A photo to the forum of all the parts laid out in the order you think they should be installed would help identify any potential issues.

 

[poita]

On the GXP spindle are you using SRAM red spacers or the black ones supplied by praxis. I haven't worked on one for a year or so but from memory it needed the black spacers as they had a particular aluminium bevel that sat against the bearing.

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Not using any spacers on the spindle. I guess this is kinda my problem, are there supposed to be spacers on the spindle?? Would solve my problem by pushing the wavy washer closer to the bearing seal...

 

[poita]

What bk said, if it's the same components as were on the bike and working fine before you took them off there is an error in the reassembly.

Pull it all apart completely and lay all the bits out and make sure you all the parts in the right order and start again. A photo to the forum of all the parts laid out in the order you think they should be installed would help identify any potential issues.

Will have to do the photo. I guess my main question is, I didn't fit this BB initially and so I've assembled as I found it. What I don't know is: was it assembled correctly in the first place. I didn't pay enough attention to how big the gap was between the crank and the DS bearing until it was already loose so I have no reference point for what's correct!! I'm kinda assuming it wasn't assembled correctly, otherwise it wouldn't have worked loose?

 

[linkl8r]

From what I can remember there was spacers, might be worth giving Dawson sports a call and asking. As to whether you need the spacer behind the wave washer on the spindle depends on shell width, 89.5 or 92mm.

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