[KGoslan]

I’ll start by coming clean, I’m not mechanically gifted, and know nothing about components. 

I have a Specialized Tarmac SL4 (2014) http://www.specialized.com/us/en/bike-archive/2014/tarmac/tarmac-sl4-sport/49942 and I’d like to replace the groupset. I’ve been looking at the Shimano 105 groupset https://www.merlincycles.com/shimano-105-5800-11-speed-groupset-black-72462.html but have no idea is the bottom bracket is compatible, any help would be much appreciated. 

 

Topic

[DirkS]

Hi, I’ve just done this on an

Hi, I’ve just done this on an sl4. I went with the praxis works osbb to shimano adapter. I think it’s the best option. Easy job. The are video on YouTube.

[TypeVertigo]

From what I can tell, Spez

From what I can tell, Spez OSBB comes in two flavors, largely dependent on your frame material.

Aluminum frames are marked “OSBB” but are BB30 in reality – the metal bearings go in and are secured with circlips.

http://wheelsmfg.com/specialized-alloy-osbb-tech

Carbon frames are still marked “OSBB” but are a modified version of PF30. The bearings sit inside plastic cups, whose outer lips stop them from sinking too far inside the BB shell – hence no need for circlips. It does need some spacers in addition to the PF30 cups though.

http://wheelsmfg.com/carbon-osbb-tech

Both BB30 and PF30 (and by extension, all flavors of Spez OSBB) are built around cranks with 30 mm spindle diamters. All Shimano cranks have 24 mm spindles, so a reducer adapter is needed.

[Rapha Nadal]

It’s not a pain in the arse

It’s not a pain in the arse to replace though? I wore out the BB in my SL4 and replaced it with a C-Bear ceramic unit. Piece of piss to source & replace.

The fitted BB is designed for 30mm axles and Shimano don’t make them – hence the need for adaptors to reduce the size of the BB.

It’s not hard.

 

Take a look, there’s even an OSBB section for you – https://www.c-bear.com/en/osbb

[dottigirl]

Wow, they’re using the same

Wow, they’re using the same trick as for their proprietary Mindset headset?  Ignore any industry standard and install something which is a PITA to replace, with associated further expense.

Utter penny-grabbing bastards.

 

 

 

[VeloUSA]

In order to use a crankset

In order to use a crankset other than Specialized you need to purchase a set of adpater cups (plus shims) such as these by Wheels Manufacturing. Why? Specialized has an OSBB (over sized bb) larger than Shimano/Sram/Campy. Thus the need for cups.

BB/PF30 Universal Adapter for 24mm Spindle Cranks (Shimano, FSA, etc.)

For a complete conversion (entire BB) see Praxis Works

https://www.praxiscycles.com/product/shimano-conversion-bb/

 

[Author]

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