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Specialized Tarmac BB/Groupset

by KGoslan
Mon, May 29, 2017 12:11
5

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. 

 

If you're new please join in and if you have questions pop them below and the forum regulars will answer as best we can.

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5 comments

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DirkS | 7 years ago
0 likes

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.

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TypeVertigo | 7 years ago
0 likes

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.

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Rapha Nadal | 7 years ago
0 likes

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

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dottigirl | 7 years ago
2 likes

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.

 

 

 

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VeloUSA | 7 years ago
0 likes

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.

http://wheelsmfg.com/bb-pf30-universal-adapter-for-24mm-spindle-cranks-s...

For a complete conversion (entire BB) see Praxis Works

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

 

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