LancerPlayer,
Thanks for the additional info. Let's see if I have this right:
Old Front: 26X9-12 6 PR Specified inflation 10 psi
Old Rear: 26X11-12 6 PR Specified Inflation 12 psi
New Front: 25X8-12 4 PR Max Pressure 7 psi
New Rear: 25X11-12 4 PR Max pressure 7 psi
The first thing that jumps out at me is that the tires are physically smaller (which means less load carrying capacity at the same pressure) and that the new tires have a lower Ply Rating (which also means less load carrying capacity).
This should be cause for alarm!!
So I'm going to be doing a little digging. I went to the Carlisle website and found the 2 new tires. They have more information:
.
New Front: 25X8-12 4 PR Max Pressure 7 psi Max load 785# @ 50 mph, Max pressure 22 psi
New Rear: 25X11-12 4 PR Max pressure 7 psi Max Load 1050# @ 50 mph, Max Pressure 22 psi
What's missing here is if the max pressure corresponds to the max load. So I pulled out my Tire and Rim Yearbook (2005) and it indicates that indeed the pressure corresponding to the max load is 7 psi for a 3 star - AND the max speed is 50 mph. But most importantly, they use a Star System (1, 2 or 3 stars) not PR. - AND - they have the old tire sizes listed So let me add that information:
Old Front: 26X9-12 6 PR Specified inflation 10 psi,
TRA: 26X9-12, 3 Star: Max load 410# @ 7 psi, Max speed 50 mph
Old Rear: 26X11-12 6 PR Specified Inflation 12 psi
TRA: 26X11-12 3 Star: Max load 380# @ 7 psi, Max Speed 50 mph
New Front: 25X8-12 4 PR Max Pressure 7 psi
TRA: 25X8-12 3 Star: 340# @ 7 psi, Max speed 50 mph
New Rear: 25X11-12 4 PR Max pressure 7 psi
TRA: 25X8-12 3 Star: 455# @ 7 psi, Max speed 50 mph.
*********************************************************************************
At this point, I tried to make some sense of what was being published. Between the various tire manufacturers for these types of tire and The Tire and Rim Assocuiation, I was able to determine that the Star system isn't like the PR system - and that I just didn't have all the information I needed to make sense of it all - and it didn't look like I was going to find that information in the short term. So allow me to take my best estimate as to what pressure needs to be in the new tires:
New fronts: 13 psi.
New rears: 15 psi.
The above is based on maintaining the pressure split to get the same spring rate split in the tires. Those pressures should have about the same load carrying capacity as the old tires did.
******************************************************************************************
LancerPlayer,
In case you have the old tires, please look very carefully at the sidewalls and tell me what it says. Look at both sides. Copy all the load information EXACTLY and post it in this thread. Include if there are markings for Ply Rating (PR) and/or Stars (*, **, or ***)
Do the same thing on your new tires.
I'm asking you do to this to confirm some things I suspect are true: That the star system and the PR system have a correspondence, but it's different in that the PR system doesn't take into account the low pressures that these tires are supposed to be used at for trail riding.
I'm going to also ask you to look at the owners manual for your Polaris. There is likely some information about tires in it. That would be very helpful in sorting this out.
Thanks ahead of time.