Originally Posted by Airdale
The bottom line is no tire speed restriction other than what's on it's sidewall is official. So, can you get Maxxis to publish anything that would officially counter the TRA restriction for ST tires that are unmarked with a speed restriction?
Marathon & TowMax manufacturers have issued bulletins with instructions on how to increase their speed restrictions to 75 MPH by increasing the tires inflation pressure 10 PSI above the sidewall inflation pressure. This does not increase the tire’s load capacity. It only applies to ST tires with their manufacturer’s approval. Goodyear & Power King seem to be the only ones to risk........
Here's what Maxxis has to say:
"High Speed" is used to differentiate the M8008 ST Radial from other products we offer that are intended for industrial and/or commercial use, in slow speed applications. The Maxxis M8008 ST Radial carries a "Q" speed rating. However, according to the Tire and Rim Association, the U.S. tire industry specification authority, inflation pressures and load specifications in general for any ST Radial trailer tires without a service description, regardless of the manufacturer, are designed and rated at 65 MPH. However, if the speed is higher than 65 MPH, the pressure and load need to be adjusted according to the following guidelines:
From 66 to 75 MPH – the tire inflation pressure needs to increase 10 PSI (not to exceed the maximum PSI the tire is rated for) but requires no load adjustment.
From 76 to 85 MPH – the tire inflation pressure needs to increase 10 PSI (not to exceed the maximum PSI the tire is rated for) and load should be reduced by 10%.
We hope this information is helpful. Thanks for your inquiry and interest in Maxxis Tires.
Your Maxxis Support Team
Maxxis International – USA
| Web: maxxis.com
What that seems to say is the 8008 is actually built as a Q rated tire but they officially say for the operator to comply with the TRA 65 mph limit. They do not put a speed rating on the tire. That tells me that running 65 mph is using about 66 percent of the tire capability. That's a good thing.