Tire size for 20" rim?

[Luper]

I'm looking to get new rims for my 06 KC SE 4x2 Titan. I know I want 20" wheels but I'm trying to decide what's the best size tire. I have stock suspension so I haven't installed any lift kit. The rim I'm looking at is 20" x 8.5" with +25 offset:
http://www.discounttiredirect.com/di...9.7&vid=008654
According to Discount Tire Direct, they recommend either 275/55-20 or 305/50-20. I'm leaning towards the 305/50 but am worried that:
1) 8.5" width isn't wide enough for the 305/50.
2) Rubbing with stock suspension will occur.
Anyone else already use this combination? Thanks in advance.

[houston1]

I am shopping as well.
My opinion is 305 is too wide for 8.5. The rim needs to be at least 9 or 9.5 for the 305.
I think the rubbing will depend on the offset. For 8.5 I believe the offset should be +18 to have stock clearance. For 9 inch wide it needs to be +12 offset. 6 offset is equivelant to 1/4 inch.

I am probably going with 285-50-20 on 20 x 8.5 wheels. It'll be an inch shorter in diameter but will look nice a wide from the rear view.

[Luper]

Yeah, that's what I'm starting to really believe. The main thing that concerns me with the 285/50 is the affect on the speedometer. According to this tire calculator:
http://www.eunos.com/tirecalc/
this size will have your speedo showing 60mph but your actually going just over 57mph. Maybe not a huge difference but things like that bother me. I know on bikes there are "speedo healers" that you can install to offset gearing changes. Not sure if anything like that exists for the Titan. Thanks for the info.

[houston1]

Yeah, the 285's will be off by 4%.
And from what I've seen there is now way to correct the speedo on the Titan.