Top speed, suggested long term RPM... - Page 3

Native · 08-31-2019, 03:03 AM

Boy, this sure is a HOT topic!

Thank you for posting those link, ECCB! Before reading them, I had always been "taught" to *NEVER* exceed the rated pressure and that running under the rated pressure was better than over.

That is the beauty of this site. Once can learn so much as long as one keeps an open mind.

cadillackid · 08-31-2019, 05:08 AM

And I always have run rated for my weight. Mainly for ride quality. But all tires exceed the psi on the sidewall when you drive them and they are pumped to rated psi . Every tire shop has told me to air high not low if I didn’t know my weight or the sticker on the truck is missing. If I air to sidewall psi my ride quality might suffer but the tire won’t be overloaded.

Max speed here is what’s in question more than psi in this thread. Obviously low psi and overspeed is likely the worst combo for a tire. And to add to it damaged or weathered tires are often in play. I hate to say it but there’s a lot of people with skoolie a d in other bus venues running tires that shouldn’t be... real commercial trucks or busses get downed for visually unsafe tires..

TheHubbardBus · 08-31-2019, 10:19 AM

Quote:

Originally Posted by EastCoastCB

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

Yes, I checked the links.

On one hand, you have the tire manufacturers, who post a max speed limit which means exactly that... max speed. It isn't a range or else they'd specify it as such. It isn't something you can modify with pressure or load or else - like their pressure and load tables - they'd include the necessary data to do so.

On the other hand (your links), you have an editor from some industry magazine saying "It's a rule of thumb to go 5psi over pressure for every 5mph over top speed". An unverified assertion based on - from what I can tell - little more than 5 & 5 being easy to remember. What's reasonable is - like the rule of thumb itself - left entirely up to interpretation and equally untested. What's a reasonable limit? 10psi over pressure for 85mph? 20psi for 95? 30 for 105? And how does our load tie into all this?

These two positions are not in agreement. So you pretty much have to choose one or the other to go by. You can do what you want. But me... I'm going to go with the tire manufacturers.

The argument that 'lots of people are doing it so it must be fine' doesn't sit well with me.

No hard feelings. We can agree to disagree

TheHubbardBus · 08-31-2019, 10:22 AM

Quote:

Originally Posted by EastCoastCB

Cheap Chinese tires are almost universally rated at 80 fwiw.

My experience with cheap chinese everything - including tires - has been that they're always rated to do more than they can.

cadillackid · 08-31-2019, 10:28 AM

so what i wonder is on a good condition average worn tire with say 25k miles on it.. whats the burst pressure?

all tires get hot and increase pressure as you roll them under a load..

I also look at this from a legal standpoint.. if you blew a tire and smashed into a pile of pieces.. and it was determined you were going over the tire's rated speed, and then your other tires got measured.. and were found to be over the rated PSI for the tires... then im thinking you are in for a rough ride... and likely the broke-life...

im sorry but I trust the manufacturers ratings on the tires...

Look at the peeps who "ran their angle grinder guardless" for years.. then that one time the cutoff wheel flew apart and the grinder kicked back hard...

Brad_SwiftFur · 08-31-2019, 12:46 PM

Quote:

Originally Posted by cadillackid

so what i wonder is on a good condition average worn tire with say 25k miles on it.. whats the burst pressure?

I can't say what the "burst pressure" is for a truck tire but I watched a video of a passenger/light truck tire that burst at around 150 PSI (I forget the exact pressure). Tires are engineered to withstand considerable abuse and for a good reason. If a tire fails at it's rated pressure, under it's rated load, within its rated speed, within its lifetime (3 important factors) then the manufacturer becomes liable for whatever happens as a result of the failure. Anyone remember the HUGE Firestone/Ford recall not long ago?

I'd hazard to guess even a worn tire will have a very high burst pressure because "it has to" for the above mentioned reasons.

Some years ago I was driving a yard spotter for a factory and they had a number of storage trailers with overflow for the manufacturing lines. One particular trailer had the tires "Singled out" (4 tires on the axles instead of 8, because it's a storage trailer that never left the yard). It was *VERY* heavily loaded (probably overweight if on the road) and I was called to spot it at a dock. I drove very slowly with it (under walking speed) and even at that slow pace, in a yard, it busted a tire. Now as for inflation pressure, age of tire, and all the other factors we'll never know. It caused a bit of a panic (imagine the sound like a cannon right in front of a factory) but no lasting harm done. It could have been catastrophic on the highway at full speed.

cadillackid · 08-31-2019, 06:29 PM

a 100 PSI tire going off is LOUD.. heck even blowing a bicycle tire (110 PSI) is loud.. ive only heard truck tires blow from a couple car lengths away.. and it was a good Boom!! can only imagine what blowing a steer on the highway would sound like..

Brad_SwiftFur · 08-31-2019, 06:45 PM

Quote:

Originally Posted by cadillackid

a 100 PSI tire going off is LOUD.. heck even blowing a bicycle tire (110 PSI) is loud.. ive only heard truck tires blow from a couple car lengths away.. and it was a good Boom!! can only imagine what blowing a steer on the highway would sound like..

Years ago I was coming across the PA turnpike and a PA state trooper was alongside the trailer tandems as the Left Rear Outer tire blew (It was *RIGHT* next to his car!) I heard the boom and looked in the mirror and he swerved from the middle lane (of 3) into the median grass and almost lost control. I stopped safely in a pull-off area and he did too. Man did he look pi$$ed and I thought I was in for it, but after a quick Q&A about getting the tire replaced, he did a quick walkaround and left to answer a radio call. Judging by the way he slammed his door, he still wasn't happy but thankfully no lasting harm done.

cadillackid · 08-31-2019, 06:55 PM

its funny though.. you could drive for 10 years and rack up over a milliopn miles.. and that ONE time you have a tire pop.. its right beside a police or DOT enforcement car

banman · 08-31-2019, 09:01 PM

The manufacturers max speed rating is because the faster you go the hotter the tire gets -- if/when the tire gets too hot, it will burst.

Do most manufacturers build in a little 'fudge' factor -- sure, maybe...

If you routinely exceed the max speed rating on your tire -- just know you're wrong. There's nothing to discuss.

Yes, Michelin is obviously more likely to have a fudge factor built in AND way more likely to have stricter quality control.

If you're running no-name brand tires from chi-laysia you really can't expect a high level of QC, and their may not be any fudge factor...

"There are old pilots, and bold pilots;
there are no old, bold pilots..."

cadillackid · 08-31-2019, 09:20 PM

tires are a hot subject anyway amongst RVers and skoolies alike..

some of the tires i see being run are Yeooow!! and then to think of someone barrelling over speed on weather-cracked worn out tires...

again the speed ratings are designed to last the life of tire.. so while you may be able to go 90 on new tires.. will you be able to after you have 35,000 miles and 6 years of sun, rain. road salt, bumps, bruises, curbs, stones, etc... on those tires

EastCoastCB · 08-31-2019, 09:35 PM

Quote:

Originally Posted by cadillackid

tires are a hot subject anyway amongst RVers and skoolies alike..

some of the tires i see being run are Yeooow!! and then to think of someone barrelling over speed on weather-cracked worn out tires...

again the speed ratings are designed to last the life of tire.. so while you may be able to go 90 on new tires.. will you be able to after you have 35,000 miles and 6 years of sun, rain. road salt, bumps, bruises, curbs, stones, etc... on those tires

You know I'm not the one doing 80 on dry rotted tires!

Ronnie · 09-01-2019, 06:56 AM

Many years ago I was helping move some rail,and the fellow who had the truck was a bit of a fast driver. That poor truck was well over its weight limit, it was summer and we were doing about 70 when both rear tires on one side blew. we were all over the road as he fought to get it under control, all cars around got out of the way thank goodness, as the truck rocked and rolled from the explosion. I thought for sure we were going to roll over. Once stopped two more tires went. Just to add insult to injury the spares were the wrong size....

o1marc · 09-01-2019, 10:31 AM

Quote:

Originally Posted by banman

The manufacturers max speed rating is because the faster you go the hotter the tire gets -- if/when the tire gets too hot, it will burst.

Do most manufacturers build in a little 'fudge' factor -- sure, maybe...

Yes, Michelin is obviously more likely to have a fudge factor built in AND way more likely to have stricter quality control.

I think everyone would be surprised how much "fudge factor" is built into tires. It's not speed alone that creates heat in the tires.

TheHubbardBus · 09-01-2019, 11:12 AM

Quote:

Originally Posted by o1marc

I think everyone would be surprised how much "fudge factor" is built into tires. It's not speed alone that creates heat in the tires.

Surprise me. How much?

cadillackid · 09-01-2019, 12:06 PM

my final word on this: is that

I personall am not pumping my tires up above the recommended pressures on the tires or below the recommended pressures on the Bus..

I personally am not driving any faster than the rated speed on the Tires installed..

I also wont drive on worn out or damaged tires...

the fact that this discussion exists shows people are thinking and questioning which is good.. knowledge is power... we all need as much knowledge as we can get..

the fact people are outwardly saying "screw whats stamped on my tire im driving however fast i want.. the tires wont bust".. is one of the reasons we have threads like "help!! i cant find insurance for my skoolie....."

magnakansas · 09-01-2019, 01:01 PM

I lived where a wire manufacturer had a plant. made wire for a variety of things including tires. I had a conversation with a fellow that worked in quality control lab. told me the standards of acceptable were above all others with michelin. what was okay for product for all the other tire manufacturers was not good enough. one of the tests were pulling rubber off the wires,,,, michelin took quite a bit more force to pull off the wires in a passing test. surface finish of the wire was much smoother amount of dirt/ grease was less tolerated.

In my personal experience, I have balanced more michelins that did not need weight than all the other tires I have mounted combined.... almost half of all michelins I have mounted did not need weights.... 25% needed .25 ounce and I have never put more than an ounce on a michelin...... well that is not exactly true... there have been rims that were bare and needed more than an ounce just to balance out the crappy rim....... also michelins seem to be rounder than any other tire brand I have worked with.

add to that the general wet weather braking performance of michelin across the board.... most of us never hit the limit of a tire in dry braking..... more of us have locked a wheel in wet weather.......

william

magnakansas · 09-01-2019, 01:11 PM

I hope to never ever have to find the top speed on my buss. the engine rpm, power curve, axle ratio tire size transmission ratios.... planned cruise speed is 65 mph... tires rated more, but dont plan on doing more. the whole idea of the bus is to be able to look around and stop for any reason.... smell the roses, cruise a junk yard, get a massage at a day spa, buy a mood ring... get another ice cream.... read the nine hundred and twelfth hysterical marker i've come across. 65 mph all day every day.. or slower. no hurries no worries.

TheHubbardBus · 09-01-2019, 01:48 PM

Quote:

Originally Posted by magnakansas

I hope to never ever have to find the top speed on my buss. the engine rpm, power curve, axle ratio tire size transmission ratios.... planned cruise speed is 65 mph... tires rated more, but dont plan on doing more. the whole idea of the bus is to be able to look around and stop for any reason.... smell the roses, cruise a junk yard, get a massage at a day spa, buy a mood ring... get another ice cream.... read the nine hundred and twelfth hysterical marker i've come across. 65 mph all day every day.. or slower. no hurries no worries.

Ronnie · 09-01-2019, 05:43 PM

I am curious to look on my tires now and see what the speed rating is. I do have all new tires, and no retreads.

Here are my comments on speed in general, if on an interstate I expect to be able to do the speed limit, and feel it is rather rude to be going slower and forcing everyone to scramble around you. With the bus I get in with the trucks and stay with them.

When I want to go slower I take the back roads. Besides there is more to see on the back roads, so why clog up the interstates poking along.

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