Top speed, suggested long term RPM...

[EastCoastCB]

https://www.moderntiredealer.com/new...ure-is-the-key

https://www.truckinginfo.com/159434/...for-your-tires

75 is a common rating but its not a hard limit.

[cadillackid]

If you blow a tire and cause a crash.. and it’s determined you were going faster than the tires rated speed then get familiar with the jailbird and homeless lifestyles..

Want to go fast then go buy tires rated for the speed.. they may cost more but it’s worth it
Christopher

[TheHubbardBus]

Originally Posted by EastCoastCB

75 is a common rating but its not a hard limit.

Whatever the manufacturer's speed rating is, be it 75mph or something else, is a hard limit. It's the maximum safe sustained speed a manufacturer rates their tires to be operated at. It's independent of pressure and load, as it assumes both to be within acceptable parameters. You might lower the effective safe speed of a tire by running less-than-optimum pressure, but you're not going to increase the rated safe speed doing the same.

Whether you or anyone else chooses to ignore it is a separate matter entirely. The 5psi for every 5mph over the rated tire limit 'rule-of-thumb' referenced in the article you cited makes me cringe.

[Sehnsucht]

I'm trying to figure out who in their right mind wants to do 75mph in a bus. I've driven a number of trucks governed at 65 and 70 which was as fast as I dared to go in ideal conditions. I shutter to think the outcome of someone doing 70-75mph in the size of vehicle we're discussing and then failing to recognize changing conditions soon enough to maintain control. Whether rated for those speeds or not, a blowout at that speed is nonetheless jarring and far less likely to turn out well.

[TheHubbardBus]

Originally Posted by Sehnsucht

I'm trying to figure out who in their right mind wants to do 75mph in a bus. I've driven a number of trucks governed at 65 and 70 which was as fast as I dared to go in ideal conditions. I shutter to think the outcome of someone doing 70-75mph in the size of vehicle we're discussing and then failing to recognize changing conditions soon enough to maintain control. Whether rated for those speeds or not, a blowout at that speed is nonetheless jarring and far less likely to turn out well.

Exactly.

The difference between 65 & 75 in terms of how long it takes you to get from A to B is linear, and in most cases is fairly insignificant. The impact on fuel economy, on safety, and on component longevity is more along the lines of an incremental curve. The faster you go, the less sense it makes. Squared.

I just want to go fast enough to not be a rolling road hazard. Past that, it's just wasted fuel.

[Necro]

I get past by 18 wheelers going 90 everyday...

[TheHubbardBus]

Originally Posted by Necro

I get past by 18 wheelers going 90 everyday...

They're idiots.

[kazetsukai]

Originally Posted by TheHubbardBus

Whatever the manufacturer's speed rating is, be it 75mph or something else, is a hard limit. It's the maximum safe sustained speed a manufacturer rates their tires to be operated at.

Its not a "hard limit" in so far that no, your tires don't pop 1mph/1psi over their rating. The rated pressures and speeds always incorporate headroom into the figure.

I will agree that going over the specified ratings is a great way to get yourself in trouble. Whether the machines will go 80mph or not, whether the tires will run at 90mph or 10psi above their rating is a separate question to whether that is a good idea. Its not.

One, when something happens, and you're operating above spec, that is giving your insurance a way out of paying and the government a pretext to take action against you.
Two, the headroom included in the rating exists for your benefit. The life of your tire is prolonged by operating in spec, versus 100% of what the tire may physically be capable of.
Third, mass manufacturing of anything guarantees some level of variability in top-end capabilities- attempting to go >10PSI or >10MPH may work flawlessly for one tire, but cause another to fail.

Tl;DR: Don't go above/beyond spec, its not worth it. Get higher spec'd tires if you want faster speeds.

[Necro]

Hell, the only reason I wont get honked at and brake checked at 75 is because its a school bus. The roads I travel most people do 85-95 and get REALLY pissed if your going less then 80.

[cadillackid]

Coaches run 80 all the time... ive looked their tires up and in many cases they are a ** VERY ** expensive 85 MPH 12R24.5 tires on those..



in my red bus it would go pretty much as fast as I want with how its geared and turned up.. however at 62-65 she cruises..



my DEV bus taught me how to road trip all over again... for a long time i was a guy who would marathon drive at 80 in my car.. passing everything in sight.. i'd get to a destination and have a good time and turn around or go to the next destination...



what I did was completely miss out on everything in between... really i may as well have flew Delta as I wasnt roadtripping i was going from point A to point B..


my DEV bus will run 70 if I floor it and redline it... im sure she would run that way all day.. but I drive her at 62.. and she just purrs along.. I see a sign? i stop.. a road that looks interesting? i take it..



by lowering your speed you begin to find that the highway isnt always the fastest way... oh sure it is if you are running 75.. but at 62 the 2 lane state routes may be shorter.. so even if you are in a "hurry" you can "gain back" some "lost speed" in lower distances.. and you see a whole lot of neat stuff..


me? i stop all the time.. coffee shops, streets to walk, town squares, mom and pop pizza joints.. the artist-brain in me comes alive like it never did traversing the interstates..



I buy busses to enjpy them and build them and road trip them everywhere.. if I need to get from point A to point B quickly I choose something other than one of my busses..

-Christopher

[TheHubbardBus]

Originally Posted by kazetsukai

Its not a "hard limit" in so far that no, your tires don't pop 1mph/1psi over their rating.

I never said or insinuated anything of the sort.

[kazetsukai]

Originally Posted by TheHubbardBus

I never said or insinuated anything of the sort.

Apologies, I didn't say you did. I said, look, its physically possible- not a reason to do it, however.

[TheHubbardBus]

Originally Posted by Necro

Hell, the only reason I wont get honked at and brake checked at 75 is because its a school bus. The roads I travel most people do 85-95 and get REALLY pissed if your going less then 80.

Our short bus is ~14,000 lbs completely gutted, with bumpers at eye-level to most everything else on the road. If someone wants to get all road-ragey with us 'cuz we're going too slow, more power to them. Its their facial reconstruction, not mine.

[TheHubbardBus]

Originally Posted by kazetsukai

Apologies, I didn't say you did. I said, look, its physically possible- not a reason to do it, however.

Understood. :cheers:

[Drew Bru]

Originally Posted by cadillackid

by lowering your speed you begin to find that the highway isnt always the fastest way... oh sure it is if you are running 75.. but at 62 the 2 lane state routes may be shorter.. so even if you are in a "hurry" you can "gain back" some "lost speed" in lower distances.. and you see a whole lot of neat stuff..


me? i stop all the time.. coffee shops, streets to walk, town squares, mom and pop pizza joints.. the artist-brain in me comes alive like it never did traversing the interstates.
-Christopher

Yup, that's the stuff right there! Traveling by bus has really changed our style of roadtripping.

[EastCoastCB]

Originally Posted by TheHubbardBus

Whatever the manufacturer's speed rating is, be it 75mph or something else, is a hard limit. It's the maximum safe sustained speed a manufacturer rates their tires to be operated at. It's independent of pressure and load, as it assumes both to be within acceptable parameters. You might lower the effective safe speed of a tire by running less-than-optimum pressure, but you're not going to increase the rated safe speed doing the same.

Whether you or anyone else chooses to ignore it is a separate matter entirely. The 5psi for every 5mph over the rated tire limit 'rule-of-thumb' referenced in the article you cited makes me cringe.

No its a recommended maximum speed. Raise the pressure- raise the mph. Within reason, of course. Did you check the links?

[EastCoastCB]

Originally Posted by Sehnsucht

I'm trying to figure out who in their right mind wants to do 75mph in a bus. I've driven a number of trucks governed at 65 and 70 which was as fast as I dared to go in ideal conditions. I shutter to think the outcome of someone doing 70-75mph in the size of vehicle we're discussing and then failing to recognize changing conditions soon enough to maintain control. Whether rated for those speeds or not, a blowout at that speed is nonetheless jarring and far less likely to turn out well.

Schools very often go 75 or even 80 in school buses.
Drive through the Atlanta 90 mph traffic and try to get across all 5 or 6 lanes to hang a left. You can't at 55 mph. Its simply unsafe to go SLOW sometimes.

[EastCoastCB]

Originally Posted by cadillackid

Coaches run 80 all the time... ive looked their tires up and in many cases they are a ** VERY ** expensive 85 MPH 12R24.5 tires on those..



in my red bus it would go pretty much as fast as I want with how its geared and turned up.. however at 62-65 she cruises..



my DEV bus taught me how to road trip all over again... for a long time i was a guy who would marathon drive at 80 in my car.. passing everything in sight.. i'd get to a destination and have a good time and turn around or go to the next destination...



what I did was completely miss out on everything in between... really i may as well have flew Delta as I wasnt roadtripping i was going from point A to point B..


my DEV bus will run 70 if I floor it and redline it... im sure she would run that way all day.. but I drive her at 62.. and she just purrs along.. I see a sign? i stop.. a road that looks interesting? i take it..



by lowering your speed you begin to find that the highway isnt always the fastest way... oh sure it is if you are running 75.. but at 62 the 2 lane state routes may be shorter.. so even if you are in a "hurry" you can "gain back" some "lost speed" in lower distances.. and you see a whole lot of neat stuff..


me? i stop all the time.. coffee shops, streets to walk, town squares, mom and pop pizza joints.. the artist-brain in me comes alive like it never did traversing the interstates..



I buy busses to enjpy them and build them and road trip them everywhere.. if I need to get from point A to point B quickly I choose something other than one of my busses..

-Christopher

I usually go 45-55. I drive slower than any other "skoolie" owner I know when I'm in my bus. But its totally ok to have the capability to safely travel on the interstate.

[EastCoastCB]

Originally Posted by Necro

I get past by 18 wheelers going 90 everyday...

I get passed by school buses full of kids regularly.

[EastCoastCB]

Originally Posted by kazetsukai

Its not a "hard limit" in so far that no, your tires don't pop 1mph/1psi over their rating. The rated pressures and speeds always incorporate headroom into the figure.

I will agree that going over the specified ratings is a great way to get yourself in trouble. Whether the machines will go 80mph or not, whether the tires will run at 90mph or 10psi above their rating is a separate question to whether that is a good idea. Its not.

One, when something happens, and you're operating above spec, that is giving your insurance a way out of paying and the government a pretext to take action against you.
Two, the headroom included in the rating exists for your benefit. The life of your tire is prolonged by operating in spec, versus 100% of what the tire may physically be capable of.
Third, mass manufacturing of anything guarantees some level of variability in top-end capabilities- attempting to go >10PSI or >10MPH may work flawlessly for one tire, but cause another to fail.

Tl;DR: Don't go above/beyond spec, its not worth it. Get higher spec'd tires if you want faster speeds.

I'd be surprised to hear of an RV accident involving a tire where folks had insurance companies accusing them of exceeding a tire rating. Especially at the flow of traffic.
Cheap Chinese tires are almost universally rated at 80 fwiw.