S works cranks 42 tooth chainring options

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motorapido
Posts: 244
Joined: Fri Jul 30, 2010 7:08 pm

by motorapido

Have just got a set of the Specialized S Works / lightning cranks of Ebay which come with a 130BCD spider.
What are my options if i wanted to run a single ring setup 42 tooth, i've seen that Wolftooth and Absolute black do direct mount rings that fit but only in mtb ring sizes.
i could just get a narrow wide 42 tooth 130bcd ring and hope i can get a decent chain line, but are there any direct mount options in 42 tooth, i think i read somewhere that the Sram GXP type direct mount rings can fit, but not sure if it would need modding or that the chain line would be ideal.

any advise or suggestions welcome, thanks.

gtinut
Posts: 119
Joined: Wed Dec 30, 2015 4:04 pm

by gtinut

look at CX listing on absoluteblack.cc
There are 42T/130 rings.

by Weenie


motorapido
Posts: 244
Joined: Fri Jul 30, 2010 7:08 pm

by motorapido

I have considered that, but its round and not oval, and i'm not sure i will get as good a chain line as i will with a direct mount.

So i've ordered the direct mount absolute black and will report back if it works, and if not i will have to go 130bcd with the compromise on chain line and weight.

motorapido
Posts: 244
Joined: Fri Jul 30, 2010 7:08 pm

by motorapido

It fits, well sort of.
The peaks and troughs of the spline are the right number (10) and depth, so the Absolute Black ring drops straight on, and the dish works out at close to between the rings of the double spider if you reverse the ring, so that the dish is towards the crank arm.
But the alignment is out, the peaks of the spline on the crank spindle are where the trough is on the Sram cranks and hence chain-ring is at best 18 degrees out.
The spline is also loose, but it was easy to build up. A bit of mould release agent on the splines of the crank and some Loctite primer on the ring and thenLoctite 660 Quick Metal on the spline of the ring and a perfect match of the spline is achieved. 24 hours later and the ring could be pulled off and any excess filed and cleaned up ready for a test ride.

Quick Metal 660 is normally used to repair keyways and bearing seats as an industrial repair so should be plenty strong enough for the load and torque i can put through it.

Will post some photos later.


motorapido
Posts: 244
Joined: Fri Jul 30, 2010 7:08 pm

by motorapido

Well getting it installed in a frame with PF30 BB has proved a bit trickier than i first thought.
initially i either got the chainring to bind on the bottom bracket shell, or the splines to not fully engage when it was tightened.
but some measuring and a bit of machining has sorted it and, its now running sweet in my new Niner BSB frameset.
The problem was the thickness of the chainring were the lock ring clamped, it was 1mm thicker than the Specialized spider, once i'd machined a counterbore in the front face of the ring to clear the crank ring which let it push further onto the cranks spline, the lock ring could be tightened down further and the spacing worked out fine.

Using an FSA PF 30 bottom bracket with aluminium housings and ceramic hybrid bearings, the total weight with the chainring installed is 548 grammes.

Am still sorting out the final details of the build but will post some photos once complete,
and i'm still thinking of removing the logos from the cranks and refinishing them, as the were second hand and are a bit scuffed up.

motorapido
Posts: 244
Joined: Fri Jul 30, 2010 7:08 pm

by motorapido

Image
Image
Image
a few quick photos, will take some better ones in daylight with the rest of the build.

tonytourist
Posts: 1139
Joined: Sat Oct 10, 2009 7:13 am
Location: 93306

by tonytourist

Great work on the ring, it looks good too!
Definitely post a full bike shot.

by Weenie


Briscoelab
Posts: 1725
Joined: Thu Jan 26, 2006 6:01 pm

by Briscoelab

I have an S-works 110mm spider (alu) with a 42T Sram cx-1 narrow wide ring. If you're interested, let me know. It's just sitting in a box collecting dust.

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