True or False: Are Truck Wheels not supposed to go over 75 mph.

[Hurricane Rex]

I'm asking to confirm or deny this myth that some had. While working on a scholarship essay relating to speed limits, I came across an article saying truck wheels can't go above 75 mph (it also says there is a growing number of trucks with wheels designed to go up to 81 mph). Additional research albiet light research shows the same. I feel this is something the insurance lobby wants to push to keep speed limits down but I want to confirm it here (because I trust everyone here more than the insurance lobby. Is this myth true or false?

LG-TP260

[Brandon]

I would call it false unless there's actual engineering/scientific documentation to that effect.  The insurance industry has been very insidious at making false claims when it comes to speeds above 55 mph.

[SectorZ]

I'm asking to confirm or deny this myth that some had. While working on a scholarship essay relating to speed limits, I came across an article saying truck wheels can't go above 75 mph (it also says there is a growing number of trucks with wheels designed to go up to 81 mph). Additional research albiet light research shows the same. I feel this is something the insurance lobby wants to push to keep speed limits down but I want to confirm it here (because I trust everyone here more than the insurance lobby. Is this myth true or false?

LG-TP260

It's the tires, not the wheels, but yes those tires aren't really designed to consistently exceed 75 MPH under their stated pressures.

However, https://www.moderntiredealer.com/news/401670/truck-tire-speed-ratings-are-a-guideline-but-pressure-is-the-key confirms it's more of a guideline that can be moved a tad based on pressure adjustments. 

[kalvado]

Here is a flyer for some tires  speced to 75 MPH:
https://commercial.bridgestone.com/content/dam/bcs-sites/bridgestone-ex/products/bridgestone/TBR/GreatecM835A/GreatecM835A.pdf
https://commercial.bridgestone.com/content/dam/bcs-sites/bridgestone-ex/products/bridgestone/TBR/M726ELA/M726_ELA_ProductSheet.pdf

68 MPH for these guys:
https://commercial.bridgestone.com/content/dam/bcs-sites/bridgestone-commercial/Products/sales-sheets/M870-Product-Sheet.pdf

Can be down to specs of individual model, but at least some of them are limited by manufacturer

[Max Rockatansky]

It would depend more on things like speed rating of the tires.  In states like Arizona, Utah, New Mexico, Utah, and Texas it isn't uncommon to frequently encounter trucks going 80 MPH plus. 

[formulanone]

I'm asking to confirm or deny this myth that some had. While working on a scholarship essay relating to speed limits, I came across an article saying truck wheels can't go above 75 mph (it also says there is a growing number of trucks with wheels designed to go up to 81 mph). Additional research albiet light research shows the same. I feel this is something the insurance lobby wants to push to keep speed limits down but I want to confirm it here (because I trust everyone here more than the insurance lobby. Is this myth true or false?

It's the tires, not the wheels, but yes those tires aren't really designed to consistently exceed 75 MPH under their stated pressures.

However, https://www.moderntiredealer.com/news/401670/truck-tire-speed-ratings-are-a-guideline-but-pressure-is-the-key confirms it's more of a guideline that can be moved a tad based on pressure adjustments. 

The sidewalls tend to flex more for tires with lower speed ratings than than those higher speeds. Higher-speed rated tires are able to dissipate heat better as well. It also depends on load capacity; if a truck is lighter, it can exceed certain speed limits if the pressures are adjusted higher to deal with speed excesses, with the trade-of being the trailer can't carry as much safely.

A heavily-leaden truck should be travelling slower, so as to prevent a blow out, but their tires are usually rated "slower" so it can deal with major changes in a range of loading and handle sidewall deflection. Truck tires are expensive and swapping out a heavy-duty truck tire far more work than changing a passenger car tire!

This isn't quite as magnified in road car tires, although it all depends on what / how / where you drive. There's a big difference in using a S-rated tire where a V-rated tire is called for, unless you drive very sedately and never exceed 55 mph (or the suspension is already very worn out, requiring replacement parts).

The major truck companies also want to reduce litigation, stay out of the public spotlight, and probably save a few bucks on those wear-and-tear items.

[ET21]

As I work in the industry as a broker dispatcher, trucks go 75+ all the time in areas that allow it. It's all about tire pressure: Less pressure during the summer as air expands, more pressure during the cold to combat air compression.

[cpzilliacus]

There's also the matter of retread tires.  There are (retread) truck tires designed for "local" (relatively short trip length distributions) that are used on vehicles such as dump trucks, refuse (trash) trucks and concrete mixer trucks. 

There are also tires designed for use on transit buses that run at fairly low speeds. 

I recall reading that it is illegal to use such tires on intercity coach-type buses, because such vehicles can operate for many hours at freeway speeds - while transit buses can and do operate on  freeways, they do not generally operate at freeway speeds for hours at a time. 

The NTSB investigated a fatal bus crash on a freeway (might have been in Louisiana) where it was determined that the bus was equipped with retreads not intended for use at such speeds, and  that contributed to the crash.

I believe it is also illegal to put any retread tire on the steering axle of any bus.

My pickup truck has mud and snow tires that are speed rating R, which are good up to 106 MPH (I never drive it that fast).

[abefroman329]

I have a somewhat-related question: To what degree do variances in tire pressure lead to variances in the height of a truck? I saw a tractor-trailer get its top lopped off by a C&NW bridge over the weekend, which made me think of this question.

[formulanone]

I have a somewhat-related question: To what degree do variances in tire pressure lead to variances in the height of a truck? I saw a tractor-trailer get its top lopped off by a C&NW bridge over the weekend, which made me think of this question.

I can't imagine a usable tire pressure range affects the truck's height by more than +/- one inch, if even that much on a regular basis.

A truck probably has more suspension travel than tire deflection, although there's pneumatic air shocks to level things out. The cab moves more than the trailer will.

[jeffandnicole]

It would depend more on things like speed rating of the tires.  In states like Arizona, Utah, New Mexico, Utah, and Texas it isn’t uncommon to frequently encounter trucks going 80 MPH plus. 

Heh...add New Jersey to that list too. Some of those trucks fly down our crowded roads!

I have a somewhat-related question: To what degree do variances in tire pressure lead to variances in the height of a truck? I saw a tractor-trailer get its top lopped off by a C&NW bridge over the weekend, which made me think of this question.

Loads in the truck can make it dip a little lower as well.  But the inch or so is usually the difference between scrapping the bridge and just barely squeezing under.  If the truck was many inches (or feet) overheight when it hit the bridge, tire pressure or weight of the load doesn't really factor in.

[hbelkins]

I have a somewhat-related question: To what degree do variances in tire pressure lead to variances in the height of a truck? I saw a tractor-trailer get its top lopped off by a C&NW bridge over the weekend, which made me think of this question.

I used to hear frequent reports of trucks getting stuck under the railroad underpass on US 27/68 (North Broadway) just south of the KY 4 intersection. A frequent solution I heard was the responders deflating the truck tires to give it clearance to pass on through.

[abefroman329]

I have a somewhat-related question: To what degree do variances in tire pressure lead to variances in the height of a truck? I saw a tractor-trailer get its top lopped off by a C&NW bridge over the weekend, which made me think of this question.

I used to hear frequent reports of trucks getting stuck under the railroad underpass on US 27/68 (North Broadway) just south of the KY 4 intersection. A frequent solution I heard was the responders deflating the truck tires to give it clearance to pass on through.

This wasn't "stuck,"  this was "the trailer looked like an opened can of sardines."

[hbelkins]

I have a somewhat-related question: To what degree do variances in tire pressure lead to variances in the height of a truck? I saw a tractor-trailer get its top lopped off by a C&NW bridge over the weekend, which made me think of this question.

I used to hear frequent reports of trucks getting stuck under the railroad underpass on US 27/68 (North Broadway) just south of the KY 4 intersection. A frequent solution I heard was the responders deflating the truck tires to give it clearance to pass on through.

This wasn't "stuck,"  this was "the trailer looked like an opened can of sardines."

True dat, but the situation I described fit the first part of your post -- asking about correlation between tire pressures and vehicle height.