Bottom bracket made of cheese! Help :(

[faster]

Hmm, so If I got that I could then run the Shimano UN-55 BUT I'd have to change my chainset crank? have I got that right??

It's so confusing this BB lark

I honestly think converting your bike to square taper would be loads of unnecessary faff.

For a start, there are different spindle lengths of UN-55 available - how would you know which one to buy to get the correct chain line? Also, I'm guessing that your current crankset is of the modern type with little tiny chainrings that modern mountain bikes have - I suspect that you'll not easily/cheaply be able to get something similar in square taper, which mainly caters for older touring/other stuff now with larger chainrings.

That converter looks really good, but presumably needs to be glued in. I wonder what happens if it creaks or moves once glued in? Would it ever come out again without destroying the frame? I honestly have no idea.

Replacing like for like might be easier. Difficult to say really, and it should be noted that that if left to get loose, exactly the same thing would've happened with a square taper set up.

 

[boydj]

I don't know where everybody gets that it's a press-fit b/b. That looks like an ISIS b/b, which were not well-designed. It's likely the splines in the crank will be damaged and a new crank will be required. The best bet is to replace with a standard UN55 square b/b and cranks to match. I should not be too difficult to work out the axle length required by measuring the current position on the cranks.

 

[ChrisEyles]

^ yeah that's what I thought at first too.

If you zoom in on the original photo the OP provided it says "press fit" on the BB.

 

[Lee]

Wow it's a minefield this BB lark

Surely it is a Pressfit 30 BB as it does say that on it no?

 

[Lee]

Found the specs for it online, 100% Pressfit 30 bb

https://www.cyclerepublic.com/bikes...oardman-pro-29er-mens-mountain-bike-2017.html

 

[boydj]

^ yeah that's what I thought at first too.

If you zoom in on the original photo the OP provided it says "press fit" on the BB.

Yeah, I got that wrong. I can see now that the splines you can see are actually from the nds crank. It's a bit different from the Shimano system that I'm used to. I replaced my Shimano setup with a Praxis Works PF30 BB and a Praxis Works crankset on my good road bike. Wheels Mfg also do a replacement PF30 BB. You can get cranks with a 30mm axle which would be a straight fit, or more commonly a 24mm axle, such as Shimano, which would require an adaptor.

 

[Ajax Bay]

Chainset: https://www.chainreactioncycles.com/sram-gx-1000-11sp-mtb-chainset-gxp/rp-prod135838
Bottom Bracket: Pressfit GXP compatible bottom brackets

 

[faster]

Chainset: https://www.chainreactioncycles.com/sram-gx-1000-11sp-mtb-chainset-gxp/rp-prod135838
Bottom Bracket: Pressfit GXP compatible bottom brackets

That's GXP - it won't be compatible.

 

[Ajax Bay]

Found the specs for it online, 100% Pressfit 30 bb
https://www.cyclerepublic.com/bikes...oardman-pro-29er-mens-mountain-bike-2017.html

From the OP's bike's spec:

Chainset	SRAM GX1000, 1x11, 32T
Chain	KMC X11, 11 speed
Bottom Bracket	SRAM PF30

Chainset: https://www.chainreactioncycles.com/sram-gx-1000-11sp-mtb-chainset-gxp/rp-prod135838

From that: Bottom Bracket Compatibility: Threaded or pressfit GXP compatible bottom brackets

That's GXP - it won't be compatible.

Can you explain why you say that? Have you got a special insight?
ETA: Reason I'm asking is because I'd be keen to learn. Can you tell from the image in the OP what BB it is?

 

[Lee]

From the OP's bike's spec:

Chainset	SRAM GX1000, 1x11, 32T
Chain	KMC X11, 11 speed
Bottom Bracket	SRAM PF30

Chainset: https://www.chainreactioncycles.com/sram-gx-1000-11sp-mtb-chainset-gxp/rp-prod135838


From that: Bottom Bracket Compatibility: Threaded or pressfit GXP compatible bottom brackets

Can you explain why you say that? Have you got a special insight?

Thanks Ajax Bay, I've done alot of looking around at Chainsets and BB's and I did come across that.

faster is right, that Chainset isn't compatable with my Pressfit 30 bb HOWEVER i think If i was to get both that you listed it would be ok, someone correct me if I'm wrong?

My head hurts

 

[Ajax Bay]

OK, you shared your bike's spec. The chainset was specified - is that the chainset you have or not? I pulled up the chainset and it gave the BB requirement. And you have two pressfit orifices (BB shell).

that Chainset isn't compatable with my Pressfit 30 bb

How do you know this?
Perhaps you'd like to share what BB you actually have there and what chainset you've taken off.
Maybe people can then identify your options for a new crankset which will fit into your current, perfectly serviceable (aiui) BB.

 

[PpPete]

There is a useful table of BB dimensions at
https://www.hambini.com/technical-support/bottom-bracket-drawings/
Be aware that the owner of that particular website knows his stuff about BBs but is rather controversial in other ways......

 

[Lee]

OK, you shared your bike's spec. The chainset was specified - is that the chainset you have or not? I pulled up the chainset and it gave the BB requirement. And you have two pressfit orifices (BB shell).

How do you know this?
Perhaps you'd like to share what BB you actually have there and what chainset you've taken off.
Maybe people can then identify your options for a new crankset which will fit into your current, perfectly serviceable (aiui) BB.

I have a PF30 bb and a SRAM GX1000, 1x11, 32T PF30 chainset on at the moment.

In order to go with the GXP chainset I would have to change my current PF30 BB wouldn't I?

 

[Lee]

There is a useful table of BB dimensions at
https://www.hambini.com/technical-support/bottom-bracket-drawings/
Be aware that the owner of that particular website knows his stuff about BBs but is rather controversial in other ways......

I watched a video of his regards the PF30 BB, he seemed to be a tad upset with it all, lots of effing and jeffing !!

 

[faster]

From the OP's bike's spec:

Chainset	SRAM GX1000, 1x11, 32T
Chain	KMC X11, 11 speed
Bottom Bracket	SRAM PF30

Chainset: https://www.chainreactioncycles.com/sram-gx-1000-11sp-mtb-chainset-gxp/rp-prod135838


From that: Bottom Bracket Compatibility: Threaded or pressfit GXP compatible bottom brackets

Can you explain why you say that? Have you got a special insight?
ETA: Reason I'm asking is because I'd be keen to learn. Can you tell from the image in the OP what BB it is?

No special insight, and I'm seemingly as clueless as everyone else about pressfit bottom brackets.

I do have a bike with a GXP crankset though, and I know that GXP has a 24mm spindle, which will be a loose fit in the original poster's 30mm bottom bracket.

My bike is threaded, but I believe you can get pressfit bottom brackets that take a GXP crankset. I wouldn't recommend this - the general consensus is that GXP isn't very good, and this is backed up by my own experience - in the 300 or so dry miles I've ridden the bike, I'd already changed the bottom bracket once. At least they are cheap!

This thread is like the blind leading the blind. Someone must be an expert on pressfit bottom brackets. In the absence of one, replacing like with like makes the most sense to me - especially as the bottom bracket in the original poster's bike seems to be okay.