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I need new tires for the orginal Macgregor trailer that hauls my 1993 26S. The trailer has the original single axle set up. Would the bias-belted tires be better because they have stiffer sidewalls? Specifically, would that help fight off trailer sway better than radials? It seems radials are superior in all other aspects.

Thanks for Your Input!!
Steve Hay, New Owner

Hey Steve,

Check out the trailer section of the discussion board for tire talk. Radials are good, as long as they are for trailers. Just make sure they're big enough for your load.

I debated this a couple years ago and ended up going with the Marathon radials.

http://macgregorsailors.com/phpBB/viewtopic.php?t=1074

I was going across country with my X this summer before high fuel prices hit and I bought new Marathon radials after discussing with the board the same question you asked. But, since I put my boat in storage for 6 months a year I think Bias would be a better tire to have the boat sitting on for that long as there would be no tire flat spots. The steel belted radials get flat spots after sitting for awhile. So, would it be best to get another set of rims and switch tires on the trailer? One for long term storage and one for road use? Thats what I wonder.
BTY, buy the Marathons radials at Walmart for $81 each.

There can be one down side to radials. Since I've experience blow outs with bias and radials on my Mac, just thought I would pass it along FWIW. When the bias goes, chunks of rubber start flying off and then the fabric blows out. No big deal. The radial goes one step further. It starts wrapping that steel wire coated with hot rubber around the axle and hub. It makes for quite an experience when it happens in Florida on the Interstate at dusk.

(And yes, I check my tires periodically--everytime I stop. About every 2 hrs. Do they make a hi-speed trailer tire?)

Bob,
Not sure if this is a Ford/Chevy style debate ... but I think flat-spotting is worse with bias tires than with radials. But I also think it's immaterial in either case. These ST trailer tires are so heavily loaded versus automotive tires that they build heat quickly ... therefore it will disappear in short order. As for Billy's problem with wrapping the cords ... That's why I believe in widening the margin of safety with 15-inchers, but I suppose four 14s solves that problem too.
Maybe Billy's problem just requires a gov'nator on that Corvette tow vehicle!

Steve - welcome aboard!
For the same reason (rapid heating) I chose Marathon radials over bias ply tires. Bias plies create more friction and heat, exactly what you don't want "more of" in a trailer tire. There's a good reason that radial tires predominate - after all, most rear car tires are simply 'towed' but they're radial too. 'Truck trailers' are predominantly bias-ply, but I believe that's because they're easier to cap, thus much cheaper ( ... Scott or IdleTime?).

Do stiffer sidewalls deter trailer sway? The boat trailer shouldn't sway much anyhow if the trailer's
tongue weight is set correctly (read as 'correct axle position'). The tires are the weakest link on the trailer, with barely any margin of safety, so they can ill-afford any dual-purpose functions. If you haven't been able to address a sway problem by correcting tongue weight, it's time to add that second axle ...
just one opinion, but unsure if it's a Ford or a Chevy~!?


ETA: So truck trailers ALSO use radials !! .... didn't know that, thanks Rich!
So, where's the percentage in Bias-ply tires, at all? Guess they're as old as 'FRISCO'

Frank C wrote:There's a good reason that radial tires predominate - 'Truck trailers' are predominantly bias-ply, but I believe that's because they're easier to cap, thus much cheaper ( ... Scott or IdleTime?).

Almost all heavy truck and semi-trailer/trailer tires, that are for mostly highway use, are tubeless, radial construction. We cap these for drive-axle, trailer and converter gear use. DOT regs prohibit use of recaps on steering axle. Radial casings can be capped more times than bias casings. That plus more mileage/cap, make radials cheaper, over time.

Rich

I disagree with choosing tires on the basis of

1) how they behave when sitting still (i.e., flat spotting)

2) how they behave when they explode (steel versus fabric construction)

If you're concerned about flat spotting, block the axle up during long term storage.

If you're concerned about blowout damage, upgrade the tires/ axle, or add another so blowouts won't happen.

I switched to radials on my second axle when I added it, but decided to save the bucks by not replacing the original tires on the original axle. When trailing at high speed on a hot day, the difference in heat build up between the two is remarkable; probably at least 20 degrees by feel, and BTW, the radials are ST215, while the bias are ST225, so the radials are lower load rated by a few pounds.

I don't know what else is going on with my bias-radial combo, but I do know heat is the enemy of tires, so I'll go for the radials. The stability problem is pretty much solved by addition of the second axle, so I don't have to worry about that trade off anymore (not sure it ever existed to begin with, but why worry?) My plan is to keep the bias until I have a problem with one of them (or they wear out), then switch to radials on that axle as well.

Not directly related, but some observations

I have the 2002 'stock' trailer with ST 215 75 D14 Titan tires

I inflate them to 50 psi 'cold' Ambient temperature.

After running on the highway on a summer day (ambient about 85F) they reached a steady state (same after one and two hours on the highway) pressure of 60 psi.

We can assume the air in the tire behaves nearly like an 'ideal gas' so that would indicate the (Absolute) temperature has roughly increased 20% from ambient.

This means at a starting point of the hot day (say 300 Kelvin, the absolute temperature scale) after running on the highway the air in the tire is about (300 * 1.2= ) 360 Kelvin which is near boiling point of water.....I remember feeling my tires and they were nowhere near this hot, but of course the tires are being spun though relatively cool air and hence can be significantly cooler than the air inside the tire.

Get radials.

My Mac-towing experience is limited, as the ramp we used during our first season was only 20 miles away, and now we're in a slip. BUT, we've made several trips of about 1,200 miles each way towing a powerboat to & from south Florida on a single-axle trailer. With the original bias-plies, I got to experience the "pieces of rubber flying off" phenomenon first-hand [luckily caught it just as the cord was starting to separate]. We went with Titan radials and they still looked new when we sold the boat [after several trips]. I also recommend getting them balanced... it won't cure a Mac's tendency to sway if the tongue weight is too low, but does eliminate the vibration and "shimmy" caused by unbalanced wheels.

Assuming that your Mac trailer has brakes, another consideration is the tires' wet weather traction -- they aren't just "along for the ride" if you find the need to make a sudden stop in the rain. I have not seen any data in this regard, but to my eye, the radials' tread pattern looks more like what I'd want for my tow vehicle, so they are probably better in the wet.

Chip's right: tires are for driving, not boat storage. If the boat is going to sit for 6 months, put some blocks down there and get the weight off the tires.

Another data point- Radials are supposed to be easier to plug if there is a small leak. At least that is what the trailer shop told me.

Very interesting discussion. As a "soon to be" proud owner of a 2006 Mac M, I have been following a lot of the trailering issues very closely.
Has anyone heard or experienced anything with nitrogen in trailer tires? When I had new tires installed on my minivan at Costco, they told me that they install nitrogen in all tires nowadays. Supposed to dramatically extend tire life, as nitrogen is an inert gas and won't deteriorte the tires from the inside.
Commets? Thanks!

Sounds like someone is blowing more than nitrogen up your ***.

Nitrogen isn't truly inert; if it were we wouldn't need to be concerned about NOx, a particularly nasty form of pollution and major component of acid rain emitted as part of nearly all combusion processes.

However, it is relatively inert at normal tire temperatures.

However, since air is 80% nitrogen to start with, the difference isn't huge. The other 20% is mostly oxygen, which is bad for your tires, so the concept is not totally out to lunch. So dry nitrogen (emaphasis on dry) is slightly better for your tires than air.

Of course, the nitrogen will eventually leak out, and unless you have your own tank of nitrogen or go to Costco every time you need air you'll eventually be back to where the rest of us are: air in your tires.

None of the vehicles I've ever owned had tires that lasted long enough for tires to wear out from the inside, so for me, it's the answer to a question nobody asked.