I bought a couple of rear derailleurs - X9 Type 2.1 and a 6870 Ultegra Di2 SGS (medium to handle up to 32 cassette). Dismantled them today. First I measured the force required to move the cage 25mm.

• X9 Type 2.1  -  3000g
  
• 6870             -    900g 

That's quite a difference. Also it really does not seem like a noticeable clutch/one-way force to it either. Not like the Zee which really is stiff but not so tensioned by the spring (it seems). 

Anyways opening up the Type 2.1 proved to be a bit more tricky since this latest iteration seems to have added a tamperproof pin. I had no way of extracting it so just had to force rotate the clutch tensioner out folding the pin into the plastic knuckle and aluminum cap/tensioner. Oh well. I suppose I could've tried drilling the pin out or see if a drill could cut into it. A screw extractor would not work since the pin was less than 2mm in diameter. This pin would not even allow any adjustment of clutch tension.

First noticed that the clutch was very well lubed and rides in a nylon shell. It seems like it would need a lot of push on the end to get it to not rotate freely (excuse the damaged aluminum shell from the pin)

There's a difference in cage lengths for the mediums for each brand. The top pulley is far more offset (from the pivot point) with the 6870 as well.

X9   pulley to pulley 75mm    pulley to pivot 73mm
6870                        87mm                           85mm

I think round one is going to be trying just more spring tension. The spring has about 1.2mm clearance from the pin without tension. There's two settings/spring pickups on the cage and it was already set on the stiffer one. I could try and cut another one on the cage or drill another hole in the knuckle itself. This can't be too radical a change because the knuckle shell is just plastic and the spring could just tear out the hole. Perhaps to not reduce the amount of plastic hanging on the spring hook it is better to drill the cage and pin bushing with a third position. 

OK I drilled a third hole in the cage and pin bushing. Did it from the outside but it's hard to keep a drill straight since it hits the steel pin right at the edge and the drill wants to wander outwards rather than drilling the steel. I had to file it back inwards and have an elongated hole. 
It definitely has added some tension and instead of 900g for movement it takes 1500g now. Hopefully not threatening to break the spring out of its plastic hole the other end.

Also I played with the X9 clutch without the spring in. The one-way clutch definitely works. It's pretty nice how it works and is much simpler than the Shimano variety. I also tried it with the spring and without the cap pushing on the clutch. It seems that just the tightening squeeze from attaching the cage actually puts quite a bit of pressure on the clutch. So the cap does not come into play unless you want to exceed the clutch force. Strange. 
I backed off the cage attachment a tad to measure the spring-only force and it is identical to my modified spring in the Di2 (about 3.75lbs to move 1/4 turn). 

This is sort of crazy since the clutch tension is set by the assembly torque on the cage bolt. Just attaching it and torquing to a reasonable hand-tightness results in a lot of clutch action - more than my X01 Type 2 on my other bike and more than the Zee even though it is a very short cage. I don't get it. I suppose I could loosely attach with threadlock?! I get a measurement of almost 10lb for the quarter turn (hard to measure since its not continuous force with the one-way).

Had to replace the Bontrager R3 after about 1000 miles since it would no longer hold pressure for more than a few minutes. Must've worn wherever it was thinnest and slowly leaking anyways. I put my OEM Schwalbe Ultremo ZX 23c back on. It did not last long however. It got a cut in the sidewall on a descent on Mt. Diablo. I had just ordered a Schwalbe One 25 and an IRC Roadlite 25 as well since I love the feel of 25 lower pressure tires. Below are pics of mounting the IRC. It was a bit tighter than the Schwalbe Ultremo but still doable by hand. It inflated really well first blow from the compressor - the beads seemed to spring out nicely to seal up (and I had used dishwashing mixture to lubricate). 

So the IRC is a really nice width - just a tad wider than the Bontrager R3 and 2.5mm wider than the 23 Ultremo. Definitely wider than the rim but maybe as some point in can get a wider front rim to match 25 tires better.

I also measured the distance between the bead lines just to see if this was an indication of inflated width. The IRC 25 measures 61mm and the Schwalbe One 25 is 60mm. 
I think both of these 25 tires will be too wide on my rear rim so I will stick with the Roubaix or maybe use my other remaining Ultremo 23 on there when it wears out. It's got 1300 miles on it and is looking a little squared off but gripping well.

After riding the Grasshopper and the rough rocky dirt sections it was clear that I needed to tighten up my corrected (read: filed) dropouts. On the climbs and out of the saddle the wheel was rubbing on the NDS chain stay. All that severe bumping allowed the wheel to move forward into it's old position. 
My previous "beer can shim" approach was not going to work long term with rough roads. You can see in the pic that I created a permanent shim. 

I roughed up and cleaned the dropout with acetone. Next, I mixed some marine epoxy with cabosil to make a strong paste. Using a mold of sorts or at least a fill guide inside the dropout I put the paste in and left it for 24hrs.

With the beer can and vent tape off here's the cured epoxy. Seems to have bonded well with the frame and even to the hanger somewhat.
Using a flat and round file I shaped and trimmed it so it allowed the plastic part of the wheel axle to fit tightly in there. Also had to file the sides since the skewer will need to clamp on the hanger/frame part well. 
It is perfectly inline now. The front sits inbetween the chain stays and the top is right between the brakes/seat stays.

(Picture from Facebook posted by Paul McKenzie).
Grasshopper Series

At the beginning it really was like a road race with lots of “slowing!”, locked brakes, the occasional exit of someone into a drainage ditch etc. The first hill sorted everyone out into groups. Lots of climbing... Some of those hills just did not stop. My strava said 8600' in 74 miles and a much of it was steep too.
I could’ve saved a bit of time at the “rest” stop. Folks generally just filled their bottles and grabbed a banana. I had my musette with some snacks. Eating was really important but for me the first time I’ve had to eat while riding. 
The dirt part was really quite tough to go fast. There were sections of gravel but most was outright MTB trails. A big 3 mile descent including some mud that would do a cross race proud. Took a while for my bike to come back to life after each section. Must’ve seen 20 or so punctures. I did feel sorry for my bike in some of the worst rocky bits. It was really making noises! Also my chain fell off three times and I had to stop to put it back on. I think if I’d put it on the big ring I might’ve been better off (thought about that too late!). The folks of cross bikes were passing a lot of people.
Amazing to see how fast the good guys can crank up those hills. I got 78th out of 156 (@15.1mph average) but pleased with my time. Definitely going to try to do all of this series from now on. Very casual in some ways (like $25 entry, super friendly people and non-closed roads) but well run and fast riders to try and chase. True grassroots racing.

Technically, the 11-28T cassette was perfect and I did not need the extra 30T I have on order but did not arrive on time (might just return it). Tubeless 25c tires were perfect too. My rear wheel did not stay true in the now slightly enlarged dropouts. I need to make it a tight fit again. 

New 'Yotes kit! This was at the start in Occidental.

Here's the Specialized Roubaix 23/25c Tubeless tire on the Belgium+ rim. A good 26mm. This is really the maximum rear. As you will see I am switching the R3 to the front. 
This tire involved the compressor to inflate for the first time. Hopefully it will hold air better than the R3. Does not feel as grippy - but then again the other tires I've been using are race ready road tires. This is a bit more endurance. I might put the 23c Ultremo back here once the Grasshopper is over. 

OK here's the Bontrager R3 25c on my front wheel (Ultregra 6700 tubeless). This is a perfect size too. Nicely paired with the back. I cleaned the bead and rim really well. I heard this is a secret to keeping these tires from losing air over a couple of days. 

Here's my problem. This super-wide HED Belgium Plus rim is 25mm wide and when paired with a Fortezza Tricomp 25c tire is measures 28.2mm wide. I am guessing the Tricomp is a wide tire in general. Feels great to ride but just does not fit the Cannondale EVO frame. It rubs on both sides when it flexes under climbing or on the trainer.
This is actually wider than my old commuter 28c Ruffy-Tuffys on old rims.

This is my front wheel setup - it came with the bike. Schwalbe Ultremo tubeless on Ultegra WH-6700 wheel. I think the rim is 20.8mm wide - not the modern wide (23mm) but not super narrow (19.8mm) either. The tire is spot on it's size at 23mm. It actually lines up well with the rim too. Prolly pretty good aero properties.

So in order to get narrower in the back to fit the frame without rubbing I took the other Schwalbe 23c tire and put in on the wide 25mm rim. It measures like a fat 25c! Perfect! And its nicely lined up with the braking surface for good aero.
Clearance is perfect to the frame. I guess When they say a frame can take 25c tires it means that it can take them on regular or regular-wide rims. The combination of the wide Tricomp and the super wide rim was too much. 

Anyways, I am pretty happy with this new setup. I won't have to keep checking the piece of tape I put on the frame for wear. I've got the max tire width. It's a good profile and I can run front and back tubeless (although I have a tube in the back for now). Also there are many more options in 23c - important for tubeless. I also run asymmetric tire pressures (since there's more weight on the back so having a narrower tire on the front is fine - it's at lower pressure anyways - plus it's tubeless so less likely to pinch-flat.  
I also found this page which a strangely familiar set of calipers. Basically coming to the same conclusion:
http://www.bikeradar.com/us/road/gear/category/components/wheel-sets/product/review-hed-ardennes-plus-sl-47670/

I also was watching a video on Sagans bike for the classics. He switches to the Carbon Synapse as it will easily accommodate 25 and 28 tires on 25mm Vision tubular wheels (and it more comfy they say). So I guess the EVO is limited to 23 or 25.

Here's another. Got a new Bontrager R3 25c TLR tire. This will be my new front tire but thought I'd try it on the rear first for a measurement. It is a much more reasonable 25c measurement at 26.8mm. That is 1.4mm narrower than the TriComp. I fitted 25mm Stans Rim Tape to convert this wheel to tubeless. That was pretty easy. This tire is tight to fit but inflated easily. See pic below for frame clearance.

Well slightly better clearance to the frame with the Bonty R3 25c. I don't think it's enough though since the wheel will flex and rub I suspect. I might leave it like this for a ride to see how much rubbing. With the TriComp 1hr on the trainer was enough to wear through the PVC electrical tape. 
Although I think on the trainer it imparts more force on the skewer allowing it to move inside the (now bigger) dropouts. I should think about how to fill those gaps to make the wheel lock in place. Some epoxy metal or something?

I applied the beer-can shim on the side I filed to make it tight again and the wheel is now firmer and centered. But you can see that there has been rubbing. Even the Schwalbe 23c rubbed a bit and the Bonty a bit more but just leaving marks on the tape. The big Tricomp actually rubbed through the tape in an hour. 
Being on the trainer definitely is worse though which I don't fully understand since the load is on the axle not the wheels edge. 

Conclusion
I will get another Bonty 25c for the front for the next Grasshopper. I might consider after putting a Schwalbe on the back (since I have two basically new tires that came with the bike). That would give me two 25c widths and a great tubeless ride with a spare of each tire as well.
It would be nice to be able to find 25c tires with a bit of tread for these mixed gravel type races. I reckon though if there was any more gravel involved it would be better to get some nice file-tread cross tires on the cross bike. So sticking with 25c slicks on the road bike is prolly good!

This is a three race series from the brilliant Bike Monkey folks - Lake Sonoma and Lake Sonoma Facebook
Was not wearing the jersey but a couple of folks were taking pictures. This was far more technical than I was expecting! Had fun and a few crashes. 13th place in 35+ Sports class. Need to work on the slow speed technical riding.

Best race so far! Finally some mud.
Raced in regular 45+ B with the singlespeed - better time of day. Got 6th place.

In a park in City of Sonoma.
5th in SingleSpeed B

This race was in Windsor. Part of a three race series - details at Santa Rosa Cup.
4th in SingleSpeed B