I bought a 12mm stud upgrade for my Wildcat last month, along with a crapload of upgrades to fix some of the Wildcat's deficiencies - Bandit springs to replace the garbage AC ones (note that the Fox shocks are fine, but the cheap springs they use allow the SxS to settle and lose ground clearance), an EZ Ryde exhaust - another place AC skimped, as the stock muffler heats up and can burn right through the firewall near the passenger seat, a very nice hand-built parking brake from SAK (Cat's don't have any parking brake, and the parking pawl is notoriously thin metal. If it breaks, you are out about $1,700 for another transaxle), and a Speedwerx secondary clutch spring that fixes the poor engine braking with the stock setup.

The mechanic I had do the work knocked it all out in about 3 hours other than the stud upgrade. He could not get them loose, so I took them to my Father in Laws shop to use his press. We spent about 3 hours on this job, and no amount of torquing was going to break the castle nuts loose from the shaft. We had an air gun cranked up to 300psi and it would not BUDGE !! We eventually used a 5' breaker bar and a blow torch to get them loose, but it turns out the previous owner had put RED LOCTITE on most of the suspension bolts, including the castle nut and the Torx backing bolts that hold the disc onto the back of the hub.

So after all the blood sweat and tears, we threw in the towel and I have pissed $110 down the drain on 12mm studs that I cannot take advantage of - $80 for the kit of 16 along with a drill bit and quality black lug nuts and another $30 for an additional 8 12mm studs for the 2" wheel spacers that I bought. No point using spacers with 10mm studs when you just put 12mm studs all around, amirite ?? So yea .... I'm ticked off, but not much I can do other than enjoy the rest of the upgrades that DID work out. The thing really pulls off the line now - the exhaust was advertised as only a 1db gain over stock .. HAHAAA, uhh no. It's pretty loud. And the clutch spring allows the belt to engage quicker, so it really does pull harder than it did.

The only successful work done was getting the 2" spacers in place, so at least I now have a 53" width instead of 49" which is where I was at after cranking the Bandit springs to gain extra ground clearance. I should be satisfied with everything that did go in smoothly, but these things are a constant upgrade grind, and I'm frustrated that something I put good money into to address a possible safety issue cannot be done after all. I think I'm gonna go buy something else to cheer me up .. I have my eyes on a Polaris seat slider and some nice heated seat pads   

Link to a pic of the rear showing width now -> https://1drv.ms/i/s!AvOnOWku2Z3vhPh0JOTDiSj7jvMIdg

[2015 Z Force 800 53/Trail EPS]

Bummer. So you got the axle/castle nuts loose but not the Torx Backing bolts? What do they do? 

They hold the disk onto the hub. According to the guys on Wildcatforums, they are a one time use bolt, so I guess I didn't do enough homework to know that small detail. Regardless, the replies state that we should use a 750 psi airgun on them next time. I thought 300 psi was gonna be plenty !!! It appears that as long as I'm using the stock rims, I should be fine, but if I do go aftermarket next year, I will certainly benefit from the 12mm studs. I'm putting off this upgrade and going back to some easier ones like the heated seats and seat slider project that's next on my list.

[2015 Z Force 800 53/Trail EPS]

I don't know of anyone who had a problem with the 10mm studs on any wheel applications including using spacers. I think most every manufacturer uses them. So maybe you are OK as is. I would think it would be a nightmare to drill-out the hubs...and spacers.. for the 12mm studs without a machine shop's help. I guess a self-centering bit would help but a drill press and a table to square & lock it to seems a must in my mind.

Just trying to cheer you up..

NMK, the problem is only for aftermarket rims, as there isn't enough 10mm stud thread to properly grip and hold an aftermarket aluminum rim. The stock rims only get torqued to 40 lbs, but the aluminum ones call for 80 lbs, so its a quite common problem if you do hit something hard with the stock studs on custom rims - OOPS, there goes a stud !!

So essentially I was trying to avoid the problem before I could even HAVE the problem. I'm holding off on a new tire/rim combo for now after buying new Dirt Commanders only 6 months (and 4 rides) ago. I had to 'settle' for 27's when I really wanted 29s, but $950 for the full combo was just too much $$ to put into it when I had so many other, smaller projects that were a priority, including the exhaust and springs.

Awaiting a reply on the WCT forums as to how to get those backing bolts out. I'm thinking I could remove the hubs, which is where we were yesterday, and take them to a local garage with a heavy duty airgun and let them remove the bolts. Then the hubs will pay a visit to my FiLs shop where we can use his press to remove the 10s and put the 12s in. We were a bit over halfway done yesterday, but without new Torx backing bolts to put back in, we decided to give up and determine what we were doing wrong to make this job so difficult when others had no problems with it. Red loctite was our main problem - that stuff is just nasty and had no place being on those bolts.   

[2015 Z Force 800 53/Trail EPS]

Is it the A/C OE 10mm studs that are shorter then others? or is it aluminum wheels with the offset for the A/Cs that are the problem. I run ITP SS112s on my Brute which are an aluminum aftermarket for it and using the ITP lugs, there is about the same amount of stud being used. One interesting thing I found was that although the CFM wheels are also 4/110, the material is much thinner and I can't use the capped lugs..has to be an open lug cause it has that much farther to thread-down. So I guess wheels are not all made the same...at least these two.

I had 10 MM studs on my Rhino I used to have.  I upgraded them to 12mm studs also.  We would break studs on the 10 mm ones because when you really get to beating on them there is not enough diameter of the stud to hold it. And once you break one the others go pretty quick.  10 mm is not enough for a full loaded SxS that you are going to run HARD. I can vouch for that.

[2015 Z Force 800 53/Trail EPS]

I had 10 MM studs on my Rhino I used to have.  I upgraded them to 12mm studs also.  We would break studs on the 10 mm ones because when you really get to beating on them there is not enough diameter of the stud to hold it. And once you break one the others go pretty quick.  10 mm is not enough for a full loaded SxS that you are going to run HARD. I can vouch for that.

Good to know. Didn't realize they could be a problem.