tire size & pressure relationships

[lee]

Because of some earlier threads, I'm interested in building a table of what happens to tire size as a result of heat and pressure. If you want to help, I would like interested members to submit their info (using my own tires as an example - other parameters of interest welcomed too).

I have done this before, but didn't bother to keep the numbers....anyway....first I adjusted the pressure front to back to get the same static rolling radius. this was done by measuring from floor of garage to top edge of the wheel (not tire) at a cold setting (can't use top of tire as it expands with pressure changes, yet is not a function of rolling radius). Next, need to measure the same after driving and thus heating the tires.

As a follow-on, I intend to check the physical (vice static) rolling radius by marking the tires, and seeing how that matches up. Finally, I want to see what the difference is at the limits of turning radius. Why am I interested? I expect most of us have heeded the Subaru warning not to mix tires sizes front to back on AWD to avoid unduly stressing the transfer clutches/transaxle. I have interpreted that to really mean we should be matching the number of times a tire rotates (turns excepted??).

Opposing opinions solicited and most welcomed...I'd hate to be doing this then have a DUH! moment.

tire brand/type: Fulda Extremo, 225x50x16, Z-rated

static front cold: 20-1/2" @ 40 PSI
static rear cold: 20-1/2" @ 28 PSI

static front hot: 20-5/8" @ 42.5PSI
static rear hot: 20-9/16" @ 29PSI

10 rotations front = XX rotations rear (cold)
10 rotations front = XX rotations rear (hot)
@ Max turning, 10 rotations front, inner=XX rotations front, outer = YY rotations, rear (don't intend hot & cold repetitions)

edit: added first round of hot measurements. the PSI rating is what the tire pressure measures hot - not that I added any air.