Trailer Tire Pressure/Temp/Speed vs. failure ?

CHD Dad wrote:
Tireman - forgot you asked about my tires.

Maxxis M8008 ST
ST205/75R14
Load Range c

Camper weighs in at 6600# loaded (measured on a CAT)

I had asked about upgrading to 15" in the past so I could have more tire choices and go up to a D range easier but was told my clearances were too tight. I have a low riding camper and it had narrow axles.

With my current sized 14" tires:
I have approx 5" in-between the two tires.
I have approx 3-1/2" from the top of the tire to the underside of the wheel well.

I am aware Kuhmo makes a D 14" tire but nobody had them in stock and ordering would have taken a couple weeks at best. This was both online and local last year. We had a big tow coming up so I went with the M8008 as it had the best reviews of normal C ST tires. I even looked at the 14" U-Haul Goodyear bias-ply tires but was told they were inferior tech and with my camper sitting several months at a time I would have flat spot issues.

I feel your pain on lack of room for larger diameter tire. On my camper, I too suffer that same issue. Simply there is no added room at all above the tires for anything larger.
So I stayed in 14" and went to Kumho 857.
I got mine from TireRack in about three days.

CHD Dad wrote:
Tireman - forgot you asked about my tires.

Maxxis M8008 ST
ST205/75R14
Load Range c

Camper weighs in at 6600# loaded (measured on a CAT)

I had asked about upgrading to 15" in the past so I could have more tire choices and go up to a D range easier but was told my clearances were too tight. I have a low riding camper and it had narrow axles.

With my current sized 14" tires:
I have approx 5" in-between the two tires.
I have approx 3-1/2" from the top of the tire to the underside of the wheel well.

I am aware Kuhmo makes a D 14" tire but nobody had them in stock and ordering would have taken a couple weeks at best. This was both online and local last year. We had a big tow coming up so I went with the M8008 as it had the best reviews of normal C ST tires. I even looked at the 14" U-Haul Goodyear bias-ply tires but was told they were inferior tech and with my camper sitting several months at a time I would have flat spot issues.

Can't address availability issues but there are ST205/75R15 LR-C and LR-D that are about the same width but are about 1" larger OD which would reduce your 5" tire to tire clearance to 3" and reduce the tire to wheel well by 1/2". Both LR will provide extra margin on your load when inflated to the sidewall max inflation.

Tireman - forgot you asked about my tires.

Maxxis M8008 ST
ST205/75R14
Load Range c

Camper weighs in at 6600# loaded (measured on a CAT)

I had asked about upgrading to 15" in the past so I could have more tire choices and go up to a D range easier but was told my clearances were too tight. I have a low riding camper and it had narrow axles.

With my current sized 14" tires:
I have approx 5" in-between the two tires.
I have approx 3-1/2" from the top of the tire to the underside of the wheel well.

I am aware Kuhmo makes a D 14" tire but nobody had them in stock and ordering would have taken a couple weeks at best. This was both online and local last year. We had a big tow coming up so I went with the M8008 as it had the best reviews of normal C ST tires. I even looked at the 14" U-Haul Goodyear bias-ply tires but was told they were inferior tech and with my camper sitting several months at a time I would have flat spot issues.

vesh1717 wrote:
Prob going to start a war, but since I have switched to lt tires I cannot for the life of me understand why I ever used st tires. It just makes total sense to me, unless you plan to never run over 60ish mph. Since I like driving the speed limit at least, it made sense.

So to answer op, make the switch and you will have less worries. I am not am expert, but just sharing my current thoughts.

I see nothing wrong with switching to LT type tires as long as you have taken all the factors into consideration.

Load capacity of the tire at the intended inflation. Is it enough for the actual load on each tire with at least a 10psi over inflate margin?

Max inflation and load rating of the wheel (do not exceed with the extra 10%)

GAWR of the axle (do not exceed)

Clearances between tires and RV and if tandem axle between the two tires

Prob going to start a war, but since I have switched to lt tires I cannot for the life of me understand why I ever used st tires. It just makes total sense to me, unless you plan to never run over 60ish mph. Since I like driving the speed limit at least, it made sense.

So to answer op, make the switch and you will have less worries. I am not am expert, but just sharing my current thoughts.

CHD Dad wrote:
.....Sort of puts me in a bind - drive 65mph and put family in danger of being hit by another driver. Drive over 65mph and put family in danger due to inferior tire technology......

Hi, Another tire engineer here. I worked across town from Roger. Lived in Mogadore, until I moved. Now living in the Piedmont area of SC.

OK, there is an alternative - going to a larger load carrying capacity. This allows the use of higher speeds.

Sometimes that means going to a larger size. Sometimes that means going to a higher Load Range. Sometimes it just means using a higher inflation pressure (although trailers are usually maxed out.)

Also, I don't see this as entirely a tire problem. The vehicle manufacturers play a role in how they specify tires for their vehicles - and I'm not just talking about the brand they use. If trailer manufacturers were to size their tires such that they were capable of 85 mph, then I think we wouldn't be seeing so many tire issues.

And, yes, I do believe there is an issue wit the tire themselves that is being aggravated by the fact that trailers are typically under-tired. I think that is why very few major tire manufacturers produce ST tires.

Tireman9 wrote:
There are some "Commercial" LR-C tires from Europe in 14"

CHD What size ST are you running?

And there is the commercial load range D Kumho 857 in 14"

You guys are making me feel old. My years of association with the SCCA was early mid 70's to 1980. Showroom stock, then FA.
Left it to focus on motorcycle racing.

There are some "Commercial" LR-C tires from Europe in 14"

CHD What size ST are you running?

The 65 limit is part of the basic design for that type tire. It's up to the RV mfg to select tires appropriate for the application. But it also seems like they are not very interested in informing their customers of the limitations of their tires. You may want to point out to your dealer that you are not happy with his failure to advise you of the speed limit on the tires.
BUT he may not really care as he made the sale.

Have you checked out my Blog?

RE racing Ya Nelson was my "home" track started with Bugeye in '69. In 80 moved to Showroom and in '84 into "Big time" with Camaro running IMSA & SCCA endurance races. It all came together in '85 when we won SSA at Longest Day then in '88 I moved up to 'Enduro" class (bassically IMSA Firehawk series) and won our class 6 times in a row at Longest Day.
84 > 94 won 52 od 65 SCCA races we entered and set lap records at Nelson, Mid-O, Lime Rock, Glen, Mosport & Shannonville Canada. Got to run Riverside, Daytona, Road Atlants & Sears Point too. Had a good time till SCCA rules got stupid and required unsafe IMO modifications. Final straw was when the fined me $200 for filing an appeal to a declined protest so after 29 years I quit SCCA since they were not interested in following their published rules and other drivers were able to "buy" National points.

Was a great life while it lasted.

Tireman9 wrote:

CHD Dad wrote:
He is using the analogy of an engines redline to driving a tire above 65mph. If you are on the highway, you will likely be driving 65mph. On my local highways the speed limit is 70, meaning cars go 80+ and big rigs are all 70-75. Driving at 65 in the right lane makes me a road hazard to others at times. I get cars and rigs flying up to my bumper or just plain flying by me.

It is the redline = tire max speed I have issue with. Redline is the absolute of an engine. That is where the engineers have decided the mechanical limits of the engine are met. It is normally past the engines peak HP/TQ numbers and is also normally the physical limitations of the drivetrain. If 65mph is the MAX physical limitations of the tire then the actual speed rating should be far below that. You dont drive an engine at redline for hours on end and tire engineers shouldnt expect a tire to be driven at its Max for hours on end.

I do plan on contacting the engineer with above questions and how its worded on his site. I need to contact my friend as well, he works in the test dept for Michelin. He may not know the answers but I am sure he knows who will.

FYI - I am not an engineer, far from it. I am a gearhead and have been racing for over 2 decades. I am anal about my road and track tires. I used to own a Longacre tire pyrometer to make sure my alignment specs and pressures were spot on for given course conditions. I have since stopped racing other than an occasional karting sprint just to get the juices going but I do take tires very seriously!

Hi, Tire Engineer here. The analogy of Redline is mine. I was trying to come up with some way to let people know they should not drive above 65 and in fact should drive slower. The Load/Inflation tables for ST type tires go back to the days of 55 mph National Speed limit and have not and probably will never be adjusted as the load limits would probably be decreased which of course the RV mfg does not want.

Just as redline in an engine can probably be exceeded momentarily there will probably be cumulative permanent damage done to the engine and its life will be cut drastically, exceeding the 65 speed limit for tires can be momentarily be exceeded but the tire will be damaged and its life shortened. It may be possible that some tires are slightly more tolerant of exceeding the redline than others but I know of no way to pre-determine which individual tires can tolerate over speed. Also if a tire has ever been run low on air there will be internal damage which may make a single mile at 66 too much.

There is another problem that causes damage to ST tires and that is the basic multi-axle suspension used by most trailers made today. This set-up forces some of the 4 or 6 tires to be dragged around the corner with the result be very high internal structural strain that tires on cars or motorhomes or single axle trailers do not see.
See my post of November 20, 2013 on that specific topic.

My post of March 23, 2011 mentions my racing experience.

Hi Roger - thanks for replying to my questions. You and I are from the same area - I lived in Firestone Park for years before moving to SC. I have relatives that work at GY and one left BFG a long while back. Did some reading up on you and we ran at some of the same tracks. I did way too many laps at Nelson, ran at Mid-O quite a bit and liked the new BeaveRun facility (now Pitts Int of course). I did many years of AutoX with NeOhio and surrounding SCCA clubs and quite a few track events but nothing up to Indy Car level like you worked with! Also worked for Fred Baker for a few years and did hot lap demos for clients of ours in various Audi and Porsche's. Would love to read more about your race history but it was hard to find much, I did find a very old Pop Mech article from the late 80's!

I cant believe that tire companies havent made a better ST tire. 65mph makes sense with a 55mph speed limit. I would happily drive 55mph if it were the limit and I would have a nice safety margin in my tires. The fact that all major highways here are 70mph makes that difficult at best. I lost count of how many times we were almost rear-ended driving under 65mph. I have witnessed too many vehicles swerving to avoid me to comfortably tow at that speed in moderate traffic. If traffic is light and there is plenty of visibility and planning ahead then I can fine with it. In fact I just witnessed a bad accident on 95 where a camper was totaled and it appeared a car ran into it.

Sort of puts me in a bind - drive 65mph and put family in danger of being hit by another driver. Drive over 65mph and put family in danger due to inferior tire technology.

Not sure if this is the right thread, but would like to know your thoughts on running non-ST tires on campers. I see a lot of suggestions for upgrading to LT tires (I cant, I can only fit 14" tires on mine). I have to think LT tires are not meant for the side stress forces put on a tandem axle design of a camper. Big rigs have tandem axles to deal with but their tires are huge and heavy!

Hybridhunter wrote:
I have ran the OEM tires on my single axle trailer, axle weight usually at 100% of it's 3500# rating, some times a touch over or under, depending on the state of the black water tank. I used to always go 75, all over the states, middle of summer, highways already hot from the blazing sun, form Arizona to Minnesota. 20000 miles on the tire, probably 500 of those miles off road. No failures at all, and that is running them 100% weight rating, over the speed rating. The only thing I do is make sure the pressure is at 50psi cold, and there are no sidewall cracks.
No doom and gloom to speak of.

On a modern vehicle with it's suite of safety features, and my properly set up rig, it doesn't take me much more distance to stop or turn at any reasonable speed.

Your results may vary!

"Single axle trailer" is a MAJOR difference. Almost 25% LOWER INTERNAL DAMAGE even with same tire loading. November 20, 2013 post explains it.