Strange bottom bracket

[alexandlinda]

Hi all.. I’m restoring a Raleigh Maverick early mountain bike from the mid to late ‘80s I would guess. It has a very interesting bottom bracket setup and I wondered if anyone has come across this and if there is a possible upgrade or service solution.
First off - It’s not threaded. There is a press fit cup on both sides with oversized captive ball bearings (3/8 balls I think). Inside diameter of the cup is 45mm.
When assembled the whole axle unit is held in place with very slender nuts which may be imperial but are close to 27mm. Hard to get a spanner on so I assume there must be a special tool.
I’d be happy to hear from anyone who’s come across this!
Thanks
Alex

 

[Guinessisgoodforyou]

@Imlach @KermitGKona88 will know

 

[August Bicycles]

This is very similar to 1 piece cranks found on old BMX bikes.

It’s often referred to as the US bottom bracket standard.

Unless you are swapping to 3 piece bmx cranks like Profile racing I’m unaware of any upgrades to this setup

EDIT - this seems to be a sealed bearing upgrade for a 51mm US BB for one piece cranks - https://alansbmx.com/collections/bo...ed-bottom-bracket-for-one-piece-cranks-chrome

 

[Imlach]

Yeah American BB, going by the fact that the inner diameter is 45, should make the whole cup come to about 51mm.. there are 45mm European BB standards for one piece, usually found on old German and Scandinavian bikes.

You've got a square tapered unit there, you can buy a new one if you wish or convert to a one piece crankset if you want something really basic. You can also go down the route of 3 piece BMX cranks like mentioned by August.

I'd personally just get a new square tapered unit. Alternatively I'd go one piece, I run an unsealed old school one piece on my klunker and it's the easiest thing ever to adjust and maintain.

 

[Imlach]

You can also convert US to BSA threaded if you want to run a sealed cartridge.

 

[Imlach]

https://ninefit.dk/products/black-ops-bb-conversion-kit-american-to-euro-black

 

[Imlach]

The cups bang out easily with a flathead and a few beers to keep one sane should they be a bit stubborn on the first few blows

 

[August Bicycles]

https://ninefit.dk/products/black-ops-bb-conversion-kit-american-to-euro-black

I forgot about these things. I remember a lot of them being used when dirt jump mtbs had US BB shells but people wanted to use regular BSA bottom brackets and cranks

 

[Imlach]

I forgot about these things. I remember a lot of them being used when dirt jump mtbs had US BB shells but people wanted to use regular BSA bottom brackets and cranks

Yeah exactly. Makes everything a lot easier if someone is intent on running square taper, as you really can't beat those sealed cartridges for service free longevity on the cheap.

to OP, there are cheaper versions of the one I shared but it was the first that popped up on Google. You can get em for a little more than a tenner.

 

[alexandlinda]

Yeah American BB, going by the fact that the inner diameter is 45, should make the whole cup come to about 51mm.. there are 45mm European BB standards for one piece, usually found on old German and Scandinavian bikes.

You've got a square tapered unit there, you can buy a new one if you wish or convert to a one piece crankset if you want something really basic. You can also go down the route of 3 piece BMX cranks like mentioned by August.

I'd personally just get a new square tapered unit. Alternatively I'd go one piece, I run an unsealed old school one piece on my klunker and it's the easiest thing ever to adjust and maintain.

Thanks. If I replace it with another square tapered unit.. I’m just wondering what I need to look for?
Is it US bottom bracket 51mm?