Help, SRM FSA K-force - which bottom bracket?

Discuss light weight issues concerning road bikes & parts.
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srasmussen
Posts: 4
Joined: Thu Aug 16, 2012 10:21 pm

by srasmussen

I’ve just bought a SRM powermeter on Ebay. Its a K-Force (Not light) with power control V. I have a SLK (Not light) on my bike which goes with the BB-8000 Megaexo bottom bracket and according to various compatibility tables this also fits the K-force. I use an english bottom bracket with the inscription T1.37. The seller also send me an identical bottom bracket and claimed that it had been fitted with the SRM powermeter. Everything should be fine however it doesn’t fit. The axel/shaft on the right arm is simply too short. The total width of the bottom bracket is 92 mm which is identical to the distance from the right arm to the beginning of the splines on the shaft on the SLK crankset. On the K-force SRM the distance is 90 mm so when tightening the crankbolt it squeezes the bearings and get all tight.

What is wrong here?

Is there an alternative bottom bracket with these dimension or could the SRM be assembled wrongly? There are some torcx between the shaft and the SRM.

aerogurl
Posts: 86
Joined: Mon Apr 27, 2009 11:06 pm
Location: SF Bay Area

by aerogurl

You need the BB-8060 bottom bracket to use with the SRM KForce (team issue) Crankset. The SRM used the 'team issue' KForce arms with the removable alloy spider.

From SRM: $45
https://www.srm.de/store_usa/product_in ... d=wjvknzea

A bit cheaper elsewhere if you google it.

I have a spare Non-Drive 172.5mm arm if you happen to need it. I sold my SRM a couple years back.

Enjoy!

by Weenie


Cheetahmk7
Posts: 69
Joined: Sat Aug 20, 2011 2:09 am

by Cheetahmk7

Yes you need the 8060. You also need two of the blue FSA crushable washers - one per side.

srasmussen
Posts: 4
Joined: Thu Aug 16, 2012 10:21 pm

by srasmussen

I think you are right if what I had was a ‘team edition’ but it only states ‘ K-force’ on the crank (see the image). I believe the ‘team edition’ is a newer version. Judging from the image do you think that what I have here is really a ‘team edition’ despite the missing inscription?

Also see the compatibility table.
Attachments
SRM.jpg
compatibility_chart-v2.jpg

Cheetahmk7
Posts: 69
Joined: Sat Aug 20, 2011 2:09 am

by Cheetahmk7

Looking at your picture it definitely the 8060 that you need. These are the washers http://www.jensonusa.com/FSA-Mega-Exo-Spindle-O-Ring

srasmussen
Posts: 4
Joined: Thu Aug 16, 2012 10:21 pm

by srasmussen

Thanks, I've been a bit skeptical but having a BB-8060 at hands now it looks like you guys were right.

The next question now arises. The BB8060 does not have tis internal cylinder of the BB-8000 ( see the image BB-8000 to the left, BB-8060 in the middle, the cylinder from the BB-8000 to the right, which is too long for the BB-8060). I think I heard somewhere that the metal cylinder was required for carbon frames to assure that the frame is not crushed tightening the crank and crank bolts.

Is this a vital component for a carbon frame or should I just be a bit careful when mounting?
Attachments
bb8060-1.jpg

by Weenie


thisisatest
Shop Owner
Posts: 1980
Joined: Sat Jun 13, 2009 4:02 am
Location: NoVA/DC

by thisisatest

The extra metal tube has nothing to do with crushing carbon frames. It has to do with not over-preloading the bearings. Older "square spline" fsa cranks just tightened and tightened, the arm would not bottom out on itself. Instead, the arms would sandwich the bearings and the metal tube, all along the inner races. Everything is tight, nothing is pushed sideways.
Later "arc-spline" cranks used a wavy washer between the left arm and the bearing, and the arm would bottom out on itself. Arm is tight to the spindle, bearings are not too squished, side load is controlled by the wavy washer.
So that's a brief history lesson on fsa mega exo systems.

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