At what psi can I travel 65-75mph?
This Maxxis pdf has the same table. Using the table(s) above, my ST175/80R13 with 1060lbs load could run at a minimum 35psi with ~4% reserve capacity. Is there a +10lbs rule? I run with +1...
Forum Discussion
Hi all
The interaction of tire types, load capacity, inflation and speed "rating" are complex, as are almost all topics about the various performance trade-offs with tire selection.
I did a post just on the topic of "How fast is it safe to drive on your tires?" April 12, 2012. I have also pointed out that if you are going to deviate from US industry guidelines, you must follow the published guidelines for your specific size, type and brand. You cannot use Goodyear document to learn the appropriate load & inflation for your Maxis tires. It even means you cannot apply specifications, including speed, load & inflation from a Goodyear Marathon with a Goodyear G614.
Now, as we all know, an ST type tire has a higher load capacity rating than a similar sized LT type tire.
ST235/75R15 LR-C is rated 2340# @ 50 psi (min) and 65 mph (max).
LT235/75R15 101/104Q LR-C is rated 1985# @ 50 psi (min) and 75 mph (max).
Since load capacity is normally a function of tire size (air volume) and its inflation. If however we also decrease the tread depth and the lower the maximum operating speed we can increase load capacity slightly. In my post of Oct 12, 2011 I identified a Michelin with a seemingly higher load capacity but many want to ignore its even lower max speed rating of 62 mph.
Now to the specific question of how to operate a Goodyear Marathon at 66 to 75 mph. This is accomplished by increasing the inflation pressure. This is not as simple as many assume.
If you select the 65 mph max speed for an ST245/75R16 LR-C you will find a load capacity of 2,600# with a minimum of 50psi if you stick to 65 mph max. But if you want to drive at speeds up to 75 you need to increase the inflation pressure in the industry standards published by Tire & Rim Association. So now to carry 2,600# you need an inflation of 60psi but this exceeds the max inflation rating for this size @ LR-C so you either need to get new LR-D so you can run 60psi or to limit your load to 2,270# and 50psi.
One obvious item many simply ignore is that the max speed for a tire is much like the red-line rev limit for their engine. It clearly is possible to run an engine with a 3,500 red-line at 4,000 RPM and possibly higher but what about long term engine life?
There are hundreds if not thousands of posts on this forum from people complaining about tire failure but I have to wonder why they seem to understand the effects on engine life of high RPM operation but fail to understand that running a tire faster than its design specification will also contribute to shorter tire life.
The interaction of tire types, load capacity, inflation and speed "rating" are complex, as are almost all topics about the various performance trade-offs with tire selection.
I did a post just on the topic of "How fast is it safe to drive on your tires?" April 12, 2012. I have also pointed out that if you are going to deviate from US industry guidelines, you must follow the published guidelines for your specific size, type and brand. You cannot use Goodyear document to learn the appropriate load & inflation for your Maxis tires. It even means you cannot apply specifications, including speed, load & inflation from a Goodyear Marathon with a Goodyear G614.
Now, as we all know, an ST type tire has a higher load capacity rating than a similar sized LT type tire.
ST235/75R15 LR-C is rated 2340# @ 50 psi (min) and 65 mph (max).
LT235/75R15 101/104Q LR-C is rated 1985# @ 50 psi (min) and 75 mph (max).
Since load capacity is normally a function of tire size (air volume) and its inflation. If however we also decrease the tread depth and the lower the maximum operating speed we can increase load capacity slightly. In my post of Oct 12, 2011 I identified a Michelin with a seemingly higher load capacity but many want to ignore its even lower max speed rating of 62 mph.
Now to the specific question of how to operate a Goodyear Marathon at 66 to 75 mph. This is accomplished by increasing the inflation pressure. This is not as simple as many assume.
If you select the 65 mph max speed for an ST245/75R16 LR-C you will find a load capacity of 2,600# with a minimum of 50psi if you stick to 65 mph max. But if you want to drive at speeds up to 75 you need to increase the inflation pressure in the industry standards published by Tire & Rim Association. So now to carry 2,600# you need an inflation of 60psi but this exceeds the max inflation rating for this size @ LR-C so you either need to get new LR-D so you can run 60psi or to limit your load to 2,270# and 50psi.
One obvious item many simply ignore is that the max speed for a tire is much like the red-line rev limit for their engine. It clearly is possible to run an engine with a 3,500 red-line at 4,000 RPM and possibly higher but what about long term engine life?
There are hundreds if not thousands of posts on this forum from people complaining about tire failure but I have to wonder why they seem to understand the effects on engine life of high RPM operation but fail to understand that running a tire faster than its design specification will also contribute to shorter tire life.
