Hi again Dave
I have the BCS 740 with the Honda GX390 engine. Except for the different engines - and probably different clutches too - it's pretty similar to your BCS 853 I think. Since this spring I also use it with a Zanon ZCR 800 lawn mower, which is very similar to your ZCA. After my first 10 hours of mowing, I hope I can also help you a little.
Now that you got your mower, it's easy to see how to adjust the PTO-flange vertically. This allows the deck to run parallel to the ground at different cutting heights and wheel sizes - all within limits of course. I use the Zanon at its highest setting - 8 cm - with the standard 5x10x20" wheels, and it works fine, although I would prefer to mow an inch or so higher.
I fully agree with Bill, that it's hard to find a good reason for choosing the smaller wheels. Producers and sales personal might like them because they are cheaper, but I would go for the biggest possible wheels - especially for mowing. On a normal lawn you will easily mow in the 3th gear, and the extra speed and ground clearance is just right.
My lawn is more like a mowed meadow, and I struggle to reach the 8 cm clipping height even with the swivel caster wheels on the mower at their highest setting. By angling the PTO-flange downwards to its limit, I just reach the 8 cm with the standard tractor wheels. That's why I have ordered the 6.5x12x23" wheels :thumbsup: The added 15% in speed just comes as a pleasant bonus.
You are absolutely right about the width - the wider the better! I've changed my wheels from the original 22" to the widest possible 25" outer track width, and it helps on the stability - especially on slopes. The change is very easy: the wheel has an inner hub and an outer rim connected with 4 bolts. Remove the 4 bolts and mount the hub on the tractor in its widest position. Then swap the rims and mount them in their widest position. You probably need to swap the rims to have the tread pattern facing in the right direction.
I'm glad to hear that your slopes are less than 15 degrees. One shall mow across a slope when walking, but that can be difficult with the Zanon ZCR. With its empty weight of 183 lbs plus the weight of the grass clipping in the bag, gravity pulls the mower downhill. I also have up to 15 degrees of slope on my lawn, and I'm not able to walk across the slope beyond approximately 10 degrees. I'm simply not capable of countering the downhill torque from the mower - but perhaps it's because I'm too skinny

Locking the differential helps a little, as it forces the wheels to run at the same speed. But as soon as the mower begins its downhill turn, the differential lock doesn't help much, as the uphill wheel begins to slip. Here the steering brakes can help a little, as braking the uphill wheel forces it to turn slower than the downhill one. This method also has its limit, as the traction on the uphill wheel decreases rapidly on steeper slopes, and the wheel begins to slip anyway. All of this might work better with lighter mowers like sickle-bar mowers.
Talking about slopes, 2-wheel tractors with a mechanical transmission reaches their limits as the slope gets steeper. That is probably why tractors designed for steeper slopes - like in the alpine region in central Europe - usually have a hydraulic transmission. This - combined with a low center of gravity and very wide wheels/rollers - prevent them from tipping over even on very steep slopes. These tractors will work on slopes up to 45 degrees (100%), and in the extreme up to even 60 degrees (173%)!
Brielmaier
Don't try this with a "normal" tractor, as it might tip over even on a much shallower slope, as they usually have a much higher center of gravity. Added weight will not help much in preventing a tractor from tipping over, only geometry will. Either you need a low center of gravity or very wide wheels - or even better - both. With rubber tires lack of traction might prevent you from tipping over, as the tractor might begin to slide sideways down the slope before tipping, depending of course of the friction available.
Congratulation with your new toy, I look forward to hear about your experiences.
Best regards
Jens