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
Went back and re-read the OP first post. This could be a learning experience to all who ask questions. If you do not provide all the info needed you are going to end up with a lot of people making assumptions and guesses so the answers may or may not be based of the real facts.
I noted some missing and confusing information.
1. He didn't say what brand tire he had but provided a "Maxis" chart. So some might have assumed he had Maxis brand tires. If Maxis then the GY bulletin would not apply.
2. He did not provide the Load Range of his tires. He talked about LR-B inflation of 35 as needed for 1060 load so some might have assumed he had LR-B tires. I am guessing the tires may actually be LR-C.
3. He did not indicate if his 1060# was actual load measured per tire or estimated from his axle weight or even if estimated from RV literature.
4. He did not provide the tire placard information that the RV mfg supplied with the trailer. This would include a recommended minimum inflation, tire size, type and LR.
He did mention "reserve capacity" of ~4% which is much less than is seen on passenger cars (10% - 18% is more normal range). I think we will all agree that in general PSR have a much better track record for low failure rates ( <1% ) than ST tires ( 10% - 25%)
The 66 - 75 mph operation with +10psi but no increase in load capacity for ST type tires is part of TRA "Industry Guidelines" at least as late as the 2010 yearbook.
It is also true that FMVSS 571.109 (or "DOT 109") is a 40+ year old standard which in my opinion is in drastic need of updating as RVs and their usage today is considerably different that in the 1960s which is the real life experience those guidelines were based on.
DOT 109 will not be updated as the RV industry doesn't want better quality (higher cost) tires.
The tire industry is not going to change as if they make an improvement they will immediately be sued for making tires to the old standard and for not making the changes sooner. Lawyers would have a field day with asking the tire companies why they intentionally made bad, sub-standard tires for so many years.
US DOT is not going to change the regs. because too many in Congress feel there are too many regulations now. If Congress had their way they would probably do away with all tire regulations as they just interfere with the free market place.
Maybe the OP could provide a bit more information.
I noted some missing and confusing information.
1. He didn't say what brand tire he had but provided a "Maxis" chart. So some might have assumed he had Maxis brand tires. If Maxis then the GY bulletin would not apply.
2. He did not provide the Load Range of his tires. He talked about LR-B inflation of 35 as needed for 1060 load so some might have assumed he had LR-B tires. I am guessing the tires may actually be LR-C.
3. He did not indicate if his 1060# was actual load measured per tire or estimated from his axle weight or even if estimated from RV literature.
4. He did not provide the tire placard information that the RV mfg supplied with the trailer. This would include a recommended minimum inflation, tire size, type and LR.
He did mention "reserve capacity" of ~4% which is much less than is seen on passenger cars (10% - 18% is more normal range). I think we will all agree that in general PSR have a much better track record for low failure rates ( <1% ) than ST tires ( 10% - 25%)
The 66 - 75 mph operation with +10psi but no increase in load capacity for ST type tires is part of TRA "Industry Guidelines" at least as late as the 2010 yearbook.
It is also true that FMVSS 571.109 (or "DOT 109") is a 40+ year old standard which in my opinion is in drastic need of updating as RVs and their usage today is considerably different that in the 1960s which is the real life experience those guidelines were based on.
DOT 109 will not be updated as the RV industry doesn't want better quality (higher cost) tires.
The tire industry is not going to change as if they make an improvement they will immediately be sued for making tires to the old standard and for not making the changes sooner. Lawyers would have a field day with asking the tire companies why they intentionally made bad, sub-standard tires for so many years.
US DOT is not going to change the regs. because too many in Congress feel there are too many regulations now. If Congress had their way they would probably do away with all tire regulations as they just interfere with the free market place.
Maybe the OP could provide a bit more information.
