Tires and Speed

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Tom in NM
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Tires and Speed

Hi folks 

I've had my 13' standard with a bath for a little over a year. I tow it with my Outback and that has worked very well. The trailer is quite stable even in some strong crosswinds that we get with some regularity here in New Mexico. Being new to trailers, I realize that I have not been as attentive to speed as it seems I should be. I regularly drive a few hours at around 70. I take it I should be driving at 65. Given the 75 mph speed limit and drivers cruising at more like 85, 65 feels pretty slow! 

I've read through what I can find here about tires. I've seen the Carlisle Radial Trail HD mentioned and having an 81 speed rating. Even if I stay in the 65-70 range, it seems having some headroom on the speed rating would be a good thing. Compared to what I spend on car tires, buying 2 new trailer tires would be a modest expense, more than worth it if it provides an added marginal of safety. 

Looking for input and advice. Thanks!

Tom

salukispeed
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5 year

To have the safety margin is big deal and is only useful if you keep an real good eye on tire pressure and limit the age of the tires to 5 years max   If ever driven at low pressure for distance the tire should also be replaced ASAP as the casing has been over stressed in many cases.  I try to stay to 65 max for long distances.  A blowout or pealed tread is catastrophic on the trailer and never ends well

2019 Scamp 13 standard

Tom in NM
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Speed limits

Thanks, Robert. I appreciate that input. If I were to upgrade to the Carlisle with a 81 speed rating, are you saying you'd still run at 65?

The existing tires are on a one year old trailer (I'll check the actual tire manufacture date) and have never been run with low pressure. I check it fairly often. 
 

Update: code ends with 2620. I believe that means they were manufactured in mid-2020 and were six months old when I got the trailer at the end of December 2020. 

Tom

Ps: I guess one thing that underlies my confusion is why trailer tires have such low speed ratings versus car tires. 

Sunfish
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D load tires and speed

I blew out two C Load tires on our 16-ft Deluxe.  I have upgraded to D Load tires and highly recommend them because of their heavier-duty construction.  They are rated for heavier loads and higher speeds.  I tow with a Dodge Durango that has the factory towing package and I have a heavy-duty weight distribution/stabilizer hitch.  However, I don't drive faster than 65 mph because you have less time to react with faster speeds and you have two units to deal with if something goes wrong.  Scamp trailer tires are smaller than vehicle tires so they are rotating much more, maybe getting hotter, and wearing out quicker.  I doubt that tire manufacturers put as much effort/money/technology into developing trailer tires as car tires because the market is smaller and people don't tow as fast as many people drive. The trailer tires are much cheaper to replace than car tires.   

rriebow
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Slow and steady

An upgrade to D tires is a good idea, and changing RV tires every 5 years is the minimum.  I admit I am a speed demon without my trailer...9 over is my driving goal!  However, with my trailer I stick to 65-68 even in 75 mph zones.  My 13' tows rock solid, but there are two issues.  One, other drivers can be really stupid trying to get around a trailer or RV (good grief, they even cut off semis).  Two, for whatever reason trailer tires get hotter faster than vehicle tires.  We have had two blowouts on our larger RVs over the years, not fun.  A tire blowout on a Scamp can also tear a big chunk out of the fiberglass, an expensive repair.   We had a truck towing a large boat fly past us on the highway once...right after my husband said they are really pushing the limits of their trailer tires they had a blowout right in front of us.  Luckily they managed to get off the road without totally losing it.     

Rhonda Riebow

Tom in NM
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Joined: 06/07/2020 - 18:17
Blowouts

Thanks everyone for the input. On my trip last week a guy passed me on a two lane highway despite a semi coming the other way. Death wish.

I'm old enough to remember pre-radials and steel belts. Blowouts were not uncommon. I've gotten used to the durability of modern tires. Flats are even uncommon unless you hit something destructive like a big nail or chunk of glass. So I'm learning that trailer tires are not at that point as yet.

Other than the interstate I normally am in the 65 range anyway. For now, I'll just slow down in the freeway, check the tires more frequently, and plan to upgrade the tires soon. There seem to be several that are Q rated 81 mph. It seems that would offer an added level of headroom and security. 

Tom

Mr.T
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Had the same concerns with ST tires...

Hi Tom,  I've had similar concerns.  On one hand, it really is dangerous to travel less than the speed limit (actually less than the limit + 5) on 2-lane highways because of all the unsafe passing that happens.  On the other hand, I'm convinced that the current speed ratings advertised for ST tires are pure fiction.  Retired tire engineer Roger Marble has written extensively on this, see https://www.rvtiresafety.net/search/label/ST%20tire%20Speed%20rating for an example.  There's much more on his website.

My solution is simply tires rated for higher loads to increase the safety margin necessary for higher speeds.  Specifically, I switched out the 175/80-13 tires for Maxxis 185/80-13.  Here's the details:

https://scampowners.com/comment/15013#comment-15013

The speed/load calc in the above post was from Maxxis web site (screen shot in the post).

Tom in NM
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Tire expert

Mr. T

Thanks for this post. I spent quite a bit of time reading through his blog posts. He certainly has a lot of interesting information to inform these conversations. I've been learning a lot about what the various ratings and specs actually mean. Some are misleading like the Max Pressure on the tire and the speed ratings for ST tires. 

Sounds like the larger Maxxis tires are working out for you. I will consider those. 

Tom

scamp01 (not verified)
My 2016 13-foot scamp with a

My 2016 13-foot scamp with a bath has an L speed rating which is 75 mph.

Tom in NM
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Joined: 06/07/2020 - 18:17
Speed ratings

Interesting as my 2021 is rated for 65. After reading Mr.T's post I read quite a few of the blog posts by the tire engineer he cited. I encourage you to take a look. Speed ratings for ST tires are not based on the same kind of testing that is used for passenger tires. I tend to agree with Mr. T that speed ratings for ST tires are a bit of fiction  

My max load inflation is 50psi and that's the pressure I run them. I now drive 65-70 where I had been running 75+. A nice bonus is that my gas mileage increased about 10%.

scamp01 (not verified)
I am going to verify with my

You can google speed ratings and where to find them on the tire.