Cannondale Scalpel/ Rotor Cranks/ e13 guide problems

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Joined: Fri May 02, 2008 5:39 pm
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by DanW

Hi all,

I have just go hold of a Cannnondale Scalpel frame and am in the process of building it up with a 1x10 drivetrain.

A few things are giving me headaches, the biggest of which is the chainset/ chain guide/ chain line....

What I am trying to get working is:
32T e13 single front ring
e13 direct mount chain guide
Rotor 3D (triple cranks running the single ring in the middle ring position)
Cannondale bearings
Wheelsmfg BB30 to 24mm adapters
Xt/ XTR 11-36 10 speed cassette

With the cranks fitted correctly (wider spacer on the NDS) the 32T chain ring is very close (~2mm) to the chainstay and is far too close to the chain guide (the ring itself rub on the chain guide let alone the chain rubbing). There is no way I could run a bigger than 32T ring. On the plus side, the chainline is nice and the cranks/ pedals are central to the frame as they should be.

As a short term fix prior to taking it to the LBS I swapped the Rotor spacers on the cranks to put both the NDS and DS cranks further towards the DS. While the chain guide no longer rubs, the chainline is poor (not good in the biggest cassette cog) and both pedals are now 5mm over towards the DS (i.e. not central to the frame and lop sided to the DS). This is an issue for me due to knee probems (trust me on this- I have had a lot of fits and put a lot of time in to getting comfortable).

The only other options are:
1) Fit the Rotor cranks correctly but use the outer ring position to mount the chain ring to stop the rubbing on the chain guide. The problem with this is that the chainline is very poor especially in the biggest cog :(
2) Add a spacer between the bearings and DS crank to shift the chainring over a little. The issue with this that the axle isn't long enough for any spacers :(
3) Find a chain guide that is closer to the frame. Everything would be good then except for the very small clearance between chain ring and chain stay- I would always be limited to a 32T ring at the very most. I also don't know if such a chain guide exists.
4) New cranks and chain guide that are known to fit the Scalpel with 1x10. Downside is obviously the cost

Any ideas how to get a Scalpel running 1x10?

Thank in advance, DanW

Posts: 911
Joined: Wed Jan 18, 2012 4:23 pm
Location: Midlands, United Kingdom

by TheRookie

Have you measured the chainline? That would be my first step, then you know if it's a crank or guide issue!

Sounds like the adaptors are not quite right or maybe the bearing shell is off slightly?
Impoverished weight weenie wanna-be!
Budget 26" HT build viewtopic.php?f=10&t=110956

Posts: 1037
Joined: Fri May 02, 2008 5:39 pm
Location: Here, there and everywhere

by DanW

I have bodged a temporary chain guide/ crank solution (filing the chain guide back plate) but the 32T ring still has just 1mm or less clearance from the chainstay which does not fill me with any confidence.

Foolishly I assumed cranks would be made with sensible chainlines!

The e thirteen XCX is adjustable for chainlines 49-53mm.

I measured the Rotor chainline around 49mm and their notes say it is 48.5mm. That seems quite small and most likely the Scalpel frame was never designed for such a small chainline (even if the chainguide should in theory be close to fitting).

I think that is my problem!

Solution? Something with a 50-51mm chainline I think.

Running through the cheapish BB30 options the best seems to be SRAM XX1/ X0 with an Absolute Black Spiderless ring. 51mm chainline, £250 all in, ~510g. Hollowgrams would be nice but will be at least £450-500 even with buying the arms second hand (~495g with the same spiderless chain ring set up).

Does all of that sound correct?

Many thanks again!

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