Praxis Works PF30 problem

DeVlaeminck

Got a shop to convert my PF30 BB last summer with a Praxis Works adaptor. Now for various reasons I haven't ridden the bike since then until this week (except for a run round the shop car park with flat pedals) and I'm getting a slight creak and some chain ring "run out" although in a bike stand spinning the cranks by hand the chainring seems to run straight.

On inspection there is a gap of maybe 1mm - clear enough to see daylight between it and the frame- between the frame and the Praxis Works cup on the drive side and I believe that is allowing a slight flex under power giving rise to the creak and the appearance of a bent chainring and the chain rub on the front mech.

Can anyone with more experience of these things (or less experience if you like - all opinions welcome!) advise if I'm likely to be right about the cause of the problems? Thanks

sungod

is this the adaptor that screws together?

i.e. this type...



...for pf30 there's a plastic shell that surrounds this inner metal bit

the adaptor is pressed in from one side, then the other side is screwed in which expands a collet to hold it all in place, there's a stop in the assembly which prevents tightening beyond the designed point - if there's a gap it may have been installed incorrectly or be incompatible with the frame

it doesn't 'clamp' the bbshell from the sides, one side is still press fit, the other expands to become the equivalent of a tight press fit, to me that's bizarre for something apparently intended for people trying to eliminate problems with a press fit bb, and i've seen posts reporting creaking with these adaptors

imho the wheels mfg design looks better, it clamps the bb shell...

http://wheelsmfg.com/bottom-brackets/pf ... ckets.html

k-dog

If the gap is on the drive side then surely it just needs tightend - that will pull that side in and also expand the collet a bit which should stop it moving?

DeVlaeminck

Yes it's one of those screw together type, the shop suggested it and they seemed to have good reviews on this forum hence going with it.

sungod

k-dog wrote:

If the gap is on the drive side then surely it just needs tightend - that will pull that side in and also expand the collet a bit which should stop it moving?

you'd think so, but the two parts do not clamp the bb shell, there's a stop preventing that (unless of course the shell is wider than pf30 spec.)

k-dog

Yeah, but if it's creaking that surely means that the collet hasn't been expanded enough - and the way to expand it is to screw it in a little?

Flâneur

May be worth calling Praxis, were really helpful when I did regarding the BB on my S works

sungod

k-dog wrote:

Yeah, but if it's creaking that surely means that the collet hasn't been expanded enough - and the way to expand it is to screw it in a little?

it only expands at the collet end, which must be tightened until it hits the stop during installation, it cannot be tightened further

the other end is just pressfit, tightening the collet end will do nothing to change that

unfortunately, pressfit can creak

DeVlaeminck

Took it back to the shop, they agreed it doesn't look right with the gap, we'll see what happens hopefully just needs tightening up a bit.

DeVlaeminck

Right, they tigjtened it up but said they couldn't get it to bottom out, seemed confident it wasn't going to move but still a noticeable gap between converter and frame. On riding it is better but still getting run out under power and chain rub. It isn't creaking but I'm pretty sure the chainrings shouldn't look like they are bent under power.

I think I can move it grabbing the cranks and putting some side to side force in but it's hard to tell if it's just flex in the bike.

Worst case if this isn't going to work is the wheels manufacturing version a safe bet? Just getting back to riding after a year off the bike and a constant noise from the drivetrain doesn't help rekindle my love for the bike!

sungod

fwiw i've used the bb30-out version of the wmf one to run a gxp pm in bb30 frame, easy to fit, no problems at all