Ok I was at the shop and we had it on the stand and I see what they are saying. With the cracks on properly it looked like maybe an 1/8 inch between the crank arm and the frame clearance versus 1/4 with the carbon cranks. The shop said they looked too close to the frame and could possibly hit the frame if I was out of the saddle. They said maybe the arms are for a newer frame with mine being the 2007 not 2008 like I thought. Can somebody that has a system six 52 in frame with si or sl 175mm arms tell me what their clearance is?

Just to let you know that the System Six came with hollowgram cranks in 2007.

http://web.archive.org/web/20081118111213/http://www.cannondale.com/bikes/07/cusa/road/systemsix/index.html

1/8" is on the low side, but isn't that what you get with a low "Q" factor crank system?

Personally, I would not be worrying that you would get enough flex to cause crank interference.

_________________
dangerous curves ahead

The question being does anybody else have this 1/8" like mine and if so was there any flex enough to touch the frame?

Now I realize the problem. The Q-factor on the cranks that cannondale replaced the original si's with is much more narrow then the original silver si's that I had. That being said I can see why they may be too close to the frame. The cranks I have now have the same q-factor as the sl and sl2 which is meant for a more narrow chainstay. Thanks everybody

But 3mm or how is it metric should be okey. stiff arms and a stiff frame.

SiSL2 have bigger q-factor then SiSL

_________________
/jonas l
http://cerrol.wordpress.com (my cyclingblog)

Hmm, you have me worried now, I just refitted my cranks with the SRM spindle+bearing shield, and I have 1.5mm clearance.

I used to have just the SRM spindle, so the crank would have been, what, another 0.5mm out?



Took 1,500 watt accelerations last summer with 2mm clearance.

Question is, will it be ok now 0.5mm (1mm?) further in?

Wouldn't have it closer. Can you press the crankarm to the frame with your hands now?

_________________
/jonas l
http://cerrol.wordpress.com (my cyclingblog)

Yep- takes a fair amount of effort, but yes.

Other side:

It's kind of funny that these expert mechanics and others are stressing about looking at one of the main selling features of BB30 from the last 10 years, which is - LOW Q FACTOR.

Guys, what do you think this looks like? It means cranks that can be closer to the frame because Cannondale only has to worry about mixing with their own frames - unlike the other crank manufacturers who have to be compatible with every frame out there.

Chill.

_________________
dangerous curves ahead

That looks like mine except you are closer. Now that I see that you are going that close without issues I am going to the shop this week for a reinstall. I was thinking of ordering a 109mm spindle and doing a reverse install like the sisl2 arms show. since you aren't getting flex I go with it.

Mine is a 58, I weigh 77 kg, for reference.

I'm probably going to pull the axle out today and remove the SRM specific bearing shield, just to move it out half a mm on the NDS.

I do not think you will hit anyway.

_________________
I never took drugs to improve my performance at any time. I will be willing to stick my finger into a polygraph test if anyone with big media pull wants to take issue. If you buy a signed poster now it will not be tarnished later. --Graeme Obree

I have 2 56cm 2008 System Six Frames with 172.5mm Hollowgram SiSL cranks on. The clearance looks about the same as yours and is closer on the NDS vs. the DS. If I grab the left crank arm and NDS Chainstay in my hand and clench a fist I can make them touch but in 20,000 miles of riding this has never happened. The BB is a standard 104mm version. I can even run an SRM (latest wireless version on the standard BB and bearing shields, which is a good thing as I wouldn't fancy shifting the left crank arm any closer to the chainstay).

If you want to even the spacing up you could try and move some of the spacers from the DS to NDS of the BB axle, I think I have 2 0.5mm spacers on the DS of my setup. You may need something a little more substantial than the plastic spacers though as they will be compresed by the reletively small surface area of the NDS shoulder of the BB axle.

A couple more things to check, make sure aren't using an SRM BB axle, these have some of the NDS shoulder machined off which moves the left crank closer to the frame and the right crank further away. Also there is a specific SRM bearing shield that has extra machining on it and has the same effect. I've bought second hand Hollowgrams which have these parts on them even though they have a standard spider.

Ok I managed to install the replacement cranks I recieved from Cannondale which are the new 3D forged Si cranks. They look like the sisl but without a visible line on the side since they are one piece. The clearance looks identical to Dammit's photo which had me concerned but it takes force to flex that crank sideways. I am going to test it in an hour.

Cool, report back. I did a couple of 1,300 watt short bursts in my last ride and it was fine.