Bosch Performance CX Gen 2 chainring
 

Anybody have experience replacing the chainring on a Bosch Gen 2 Performance CX?
This video indicates no puller needed. This guy uses a hex wrench, ratchet, and lockring tool. That's it.
However, other websites indicate you'll need a puller to get the crank arm off.
I removed the hex bolt from the right-side crank arm and it certainly seemed like I was stuck without a puller. Since I didn't know what I was doing I stopped right there instead of trying to apply any persuasion to the crank arm.
A little guidance would be much appreciated.
Also, any thoughts about changing the tooth count? I'm thinking about adding a tooth or maybe two but no idea if that would confuse the bike's computer?

The crankarm in the video has a self-extracting bolt and the arm is removed with the bolt. Some crankarms require a crank puller to remove the arm after you extract the bolt. If you remove the bolt and the arm doesn't come off, you need a puller (Park has a good one for about $10). Speed is measured using the magnet on the rear wheel AFAIK and not influenced by the number of teeth on the sprocket.

OK, thanks 2old. A year or two ago I bought one of those Nashbar bike repair kits. I don't know what some of the gizmos inside are for, but one of them appears to be an ISIS puller, which supposedly works on a Bosch. At least that's what I picked up on an EMTB forum thread.
The Park tool you mentioned - is that the CWP-7?

That's it. If the Nashbar tool is like the Park, use the larger end for your system. Thread it into the crank as far as possible before turning the nut to remove the arm. Works great. Also, see Sheldon Brown if you want to learn more than you'll ever want to know about it.

OK, so I do not have the Bosch lockring tool or replacement chainrings. Still, why not see if I had the tools to remove the crankarm? I assume the Nashbar tool is inferior to the Park, but it worked. I thought maybe the little removable button on the end was gonna interfere with the splines. It did not.

Just like you said, I threaded the part that pushes the arm off way back inside the outer piece so I could get full threads on the crankarm.

I have a few questions re: installation. The crankarm didn't go on very far before binding on the splines. The 8mm bolt that holds the pedal on wasn't grabbing any threads. So I got a deadblow hammer and gave the crankarm a few gentle hits. That got me enough threads to apply the bolt. Since I didn't have an 8mm socket I had to guess at proper torque. I didn't like guessing, so will be purchasing a 3/8" drive socket. Then I can put a torque wrench on the bolt.

Should I apply a little Never-Seez to the splines next time? Does anybody have a video showing crankarm installation?

FME, ISIS arms butt against the "end" of the spline so there isn't much movement between "I'm still tightening it" to "I can't tighten it any more"; accordingly I always get it good and snug, but don't really lean on the bolt. Also, there's nothing to prevent you from checking it every couple of rides until you're convinced it's tight enough. Also, nothing wrong with most Nashbar tools (the chain whip may be an exception) and I've used many of their products through the years like their cable housing which was manufactured by Jagwire (sp?); some even said that on the housing. I built a super light spare bike for my wife with one of their frames and, even though it's been loaned out for races through the years, it's still going 10 years later. I wish Performance never purchased them and they were still in business.

Dangit, you specifically mentioned the chain whip. I guess I'll find out if the Nashbar whip is up to the challenge. I'm gonna attempt to swap out our cassettes as soon as the replacements arrive. Wish me luck!

Thanks for the guidance on tightening. Any thoughts about painting a thin layer of Never-Seez on the splines?

The chain whip probably is adequate as long as you're careful with it, and especially since it's not a "shop tool". I always use grease on metal to metal surfaces (AFAICR) like those splines, but your choice is as good (maybe better).

OK, thanks again for the help. The splines were dry. I'll apply a thin layer of Never-Seez from now on.

A side note: I woke up in the middle of the night worrying about the generations of Bosch motors. I wasn't really sure if ours were Gen 2 or 3. It seemed ridiculous to have to search around on the internet for 15 minutes. Bosch websites were useless. The manuals that came with bikes also worthless (unless I just missed it). Finally found an article from electricity bikes that showed some of the generations. Looks like ours are Gen 2. Whew! I read on some forum that the tool for Gen 2 won't work on Gen 3 and vice versa.

A friend had a Felt circa 2015 that must have had a Gen 1 motor. Interesting thing was you could move the magnet from the wheel to the crank arm and the sensor accordingly and "fool" the system into thinking the bike was traveling slower than its actual speed. He said it would go 36 mph. Needless to say, Bosch corrected that rapidly.