After you determine your tire size this is what the tractor and loader manuals calls for.
According to this chart 40psi is too much but to confirm that your tire should have a max tire pressure rating.
I have the r4 tires on my 3800 but from what I've heard the r1 tires are a softer tire so maybe your dealer airs the front tires
up with a little extra psi when leaving with a loader.The manual doesn't support that assumption tho.
front tires sizes
5.00-15 4pr =32psi
7-16,6pr=26psi
23x8.50-12 4pr=23psi
25x8.50-14 6pr=23psi
27x8.50-15 6pr=30psi
rear tire sizes
11.2-24 4pr=14psi
13.6-16 4pr=14psi
15-19.5 6pr=30psi