Boston Whaler Use of 13-inch Trailer Tires

Repair or modification of Boston Whaler boats, their engines, trailers, and gear
wild bill
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Boston Whaler Use of 13-inch Trailer Tires

Postby wild bill » Sun Sep 13, 2020 9:07 am

Why does Boston Whaler puts 13-inch wheels and tires under a Montauk 210?

Those little tires spin fast on the highway and look like an Elephant on roller skates.

Why not use 15-inch wheels?

The difference in ride height would seem negligible.

ASIDE IN REFERENCE TO SOME OTHER THREAD:
Thanks to everyone who helped me get my trailer straightened out.
2016 Montauck with 200hp Pro XS Mercury, Karavan tandem axle trailer.

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Phil T
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Re: trailer tire sizes

Postby Phil T » Sun Sep 13, 2020 9:58 am

13" tires cost less than 15".

Easy to change yourself.
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Jefecinco
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Re: trailer tire sizes

Postby Jefecinco » Sun Sep 13, 2020 11:12 am

The Karavan trailer under our 190 Montauk came with 15" wheels on a single axle. For a 210 Montauk 13s seem very undersized unless the trailer has tandem axles. Even with a tandem axle trailer under a 210 Montauk I would probably replace with 15s assuming the clearances are adequate. Measure carefully before making the change. Fenders may need to be elevated and hull clearance above the fenders may not allow that. That could lead to elevating the bunks, adjusting the winch post, etc. so that could negate any value added.
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Masbama
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Re: Boston Whaler Use of 13-inch Trailer Tires

Postby Masbama » Sun Sep 13, 2020 9:15 pm

In my opinion; if there is one area where Boston Whaler “goes cheap” is in their trailer selection. These quality boats should come with a quality aluminum trailer but I guess to keep costs down they go with what they have.

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Re: Boston Whaler Use of 13-inch Trailer Tires

Postby jimh » Mon Sep 14, 2020 7:18 am

I don't like quantitative terms of description like "little" or "fast."

I prefer to look at the actual numbers. Let's compare a 13-inch and 14-inch tire. I use common sizes:

TIRE       DIAMETER   REVOLUTIONS/MILE
205/70R13 24.3 830
205/70R14 25.3 798

Cf.: https://www.discounttire.com/learn/tire-size-calculator?

The "little" tire is only 1-inch different in diameter in 25.3-inches, or less than 4-percent. So "little" means a change of 4-percent. This is actually funny because "little tires" was being used as a derogatory term, but it turns out the actual difference between the tires is very little.

The difference in speed of revolution is only 32-revolutions per mile. Let us assume the boat trailer is to be towed at 50-MPH with the 13-inch tires. So in one hour the 13-inch tire makes 41,500 revolutions per hour or 692-RPM. If you changed to the larger 14-inch tire, it would make 39,900 revolutions per hour, or 665-RPM. That is a change of 27-RPM. So "fast" means an increase of 27-RPM.

These seem like rather trivial differences. To make an analogy, you might say one ought to change the propeller pitch in order to let the their engine run 27-RPM slower at cruising speed. Who would do that?

As far as speed rating, tires are marked with their speed rating. You can find 13-inch radial trailer tires with 81-MPH speed ratings. Towing at 81-MPH is completely insane and should never be done. But the tire is rated for that speed. I don't think there is a real concern about towing speed with 13-inch tires.

Tires are marked with their load rating. I found a 13-inch trailer tire with load range D1 and load rating 99. That means an 8-ply tire that can be inflated to 65-PIS and can carry 1701-lbs load. Considering that most small boat trailers use axles with at most a 3,500-lbs rating, a pair of these tires provides 3,402-lbs of load carrying ability, or just 100-lbs less than the axle rating, which seems like a reasonable margin. On a tandem axle trailer four of these tires provide 6,804-lbs of load. I don't think these are serious limitations for a boat trailer.

Also, remember that about five to ten percent of the trailer weight is carried on the tow vehicle tongue, so a load on the trailer tires of 6,800-lbs would represent 90 to 95-percent of the total trailer weight, and that is with a trailer of 7,160 to 7,555-lbs total trailer weight.

Exactly how much more than 7,160 to 7,555-lbs would the 210 MONTAUK boat and trailer weigh?

Also, we have a report of use of 15-inch tires on the 190 MONTAUK trailer, so from where did this hubbub of concern for the 13-tires arise?

We seem to be giving Boston Whaler a public flogging for something that perhaps they did not do, and even if they did there seems to be not a huge concern about it.

Cf.: https://www.discounttire.com/learn/load-range-load-index

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Re: Boston Whaler Use of 13-inch Trailer Tires

Postby biggiefl » Mon Sep 14, 2020 10:30 am

You do not need 15" tires for a 21' boat if tandem axle. A 13 or 14 is plenty.
On my 24th Whaler. Currently in the stable: 86 18' Outrage, 81 13' Sport(original owner), 87 11' Sport, 69 Squall(for sale cheap).

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Re: Boston Whaler Use of 13-inch Trailer Tires

Postby Jefecinco » Mon Sep 14, 2020 10:35 am

Masbama - The last time I looked at the "Build a Whaler" site aluminum trailers with tandem axles were offered as a option. I believe the "standard" trailer remains the galvanized steel Karavan. I've had good service from our Karavan but our two aluminum trailers fare better in the salt environment we enjoy.

I suspect as many Boston Whalers are sold for fresh water use as are sold for salt water use thus making a standard aluminum trailer an unnecessary expense for those buyers in fresh water regions.
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wild bill
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Re: Boston Whaler Use of 13-inch Trailer Tires

Postby wild bill » Mon Sep 14, 2020 12:08 pm

Jimh- I really like your use of facts, can't argue with math so let's look closer. My factory tires are 185/80 R13. Using the tire calculator you have shown us if I go to a comparable 14" tire (205/75 R14) I could turn 45.18 revolutions per mile less than with 13's. If I go to a comparable 15" tire (205/75 R15) I could turn 73.67 revolutions per mile less than the 13's. Now I go to the coast often, twice a month average during April- November a few times in winter but we'll just call it 8 times a year, a round trip of 380 miles. With the 14' tires I will get 45.18x380x8=137,347.2 less revolutions on the tires AND bearings. With the 15" tires I will get 73.67x380x8= 223,956.8 less revolutions. this looks like a big difference to me. I also go on freshwater trips two to three times a month in the winter. Sooo is my math wrong?
2016 Montauck with 200hp Pro XS Mercury, Karavan tandem axle trailer.

wild bill
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Re: Boston Whaler Use of 13-inch Trailer Tires

Postby wild bill » Mon Sep 14, 2020 1:29 pm

Sorry but my math was wrong. I should use 16 as a factor not 8 (eight months, twice a month). So for 14" tires 137,347.2x 2= 274,694.4 less revolutions yearly. 15" tires- 223,956.8x2= 447,913.6 less revolutions yearly. Both seem significant to me especially on bearings.
2016 Montauck with 200hp Pro XS Mercury, Karavan tandem axle trailer.

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Re: Boston Whaler Use of 13-inch Trailer Tires

Postby biggiefl » Mon Sep 14, 2020 2:13 pm

You have not stated if it is a single or tandem axle. I am assuming tandem and again you do not need larger tires for that boat. If you are only concerned about revolutions, you can put on 24's and give it some bling.
On my 24th Whaler. Currently in the stable: 86 18' Outrage, 81 13' Sport(original owner), 87 11' Sport, 69 Squall(for sale cheap).

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Re: Boston Whaler Use of 13-inch Trailer Tires

Postby jimh » Mon Sep 14, 2020 2:21 pm

Rather than calculate the magnitude of the revolutions, you should calculate the percentage difference. If you are really worried about the magnitude of the revolutions, do less trailering. If you are going to be focused on rotation magnitude, think about how many rotations there are on the bearings and tires on your towing vehicle that occur when it is NOT TOWING THE TRAILER. My god, there must be millions of rotations. Now I suppose we better put bigger tires on all our vehicles in order to limit the number of rotations per mile they spin. Where does this argument end?

You never mention the number or revolutions per mile for the 13-inch tire, so I cannot calculate the percentage change. I suspect it will be similar to what I showed above, maybe 3.8-percent more revolutions per mile.

So in your argument, you are saying, hey, I can drive 3.8-percent more on my trailer tires if I get a bigger tire. Of course, it is true. But does it mean we have to flog Boston Whaler if they once sold a trailer with 13-inch tires? I don't think so.

We started out with a claim that the tires would spin faster. That is true, but they only spin about 3.8-percent faster. If the speed of rotation is now the metric we will then have to reduce driving speed when towing. Hey--reducing driving speed when towing is a darn good idea all by itself. Drive more slowly when towing. It will be safer and you will reduced the rotation speed that has become a big concern in this thread. How much is 3.8-percent slower. Let's say we wanted to drive 60-MPH. If we drive 57.7-MPH we are able to maintain the rotation speed 3.8-percent slower. Or, looking at in the other direction, if I get new wheels and new tires that are 1-inch taller, and I adjust the fenders and the trailer bunks and rollers to compensate for this change, then I get to drive 60-MPH and I won't increase the speed of rotation compared to what it was when I was driving 57.7-MPH. Is that worth the expense and effort of changing the tire size?

ASIDE: the only place I have ever seen revolution counters on a wheel is on big semi-tractor trailers. Since the trailer does not have an odometer to record mileage, and the trailer can be towed by many different tractors, a counter is put on one of the axles to count rotations or miles or something. In this way the wheel and bearings and tires can be checked on a periodic basis based on number of rotations or miles the trailer has travelled. Maybe we all need this on our boat trailers, too.

wild bill
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Re: Boston Whaler Use of 13-inch Trailer Tires

Postby wild bill » Mon Sep 14, 2020 4:01 pm

I'm not arguing with any of your logic, it is correct but any increase in revolutions is an increase in the wear and tear on the tire, wheel and bearings. If I can reduce the number of revolutions by half a million a year by installing taller tires when it's time to replace tires anyway, why not?
2016 Montauck with 200hp Pro XS Mercury, Karavan tandem axle trailer.

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Re: Boston Whaler Use of 13-inch Trailer Tires

Postby jimh » Mon Sep 14, 2020 5:10 pm

BILL—you are completely free to buy larger tires and the larger wheels needed for them, and to have the new tires mounted on the new wheels, Then discard the older wheels and tires, and mount the new ones and also do anything else you like with your trailer.

My interest here is just to quantify the amount of “little” and “fast” that was actually involved with your initial complaint about the behavior of Boston Whaler.

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Re: Boston Whaler Use of 13-inch Trailer Tires

Postby Don SSDD » Tue Sep 15, 2020 6:08 am

Ground clearance is another concern with tire size. If you travel on gravel roads you may need more ground clearance and the taller tires will raise the axle higher off the road.

Having low ground clearance with a boat which smaller tires will provide may be a benefit when launching and retrieving as the hull is lower and you have additional buoyancy. Also, the lower tire will give more height clearance for a garage door.
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jimh
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Re: Boston Whaler Use of 13-inch Trailer Tires

Postby jimh » Tue Sep 15, 2020 6:38 am

The trailer will have the same ground clearance on the highway as it has on the launch ramp.

Generally the ground clearance of the trailer is not a problem on the highway, other than for the skeg of the outboard engine.

Should Boston Whaler always sell trailers with very tall tires on the basis that someday those trailer might travel on a gravel road?

Again, the topic is not what any particular person needs to have on their trailer. The topic is the behavior of Boston Whaler who have been accused of selling boat trailers that have tires so small their boats look like "elephants on roller skates." That claim has been found to be complete hyperbole when the difference in height of "small" tires was found to only be 3.8-percent less than "big" tires.

If you need to haul your boat 250-miles on a rough unimproved road, you better get whatever trailer you think best for that road.

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Re: Boston Whaler Use of 13-inch Trailer Tires

Postby biggiefl » Tue Sep 15, 2020 3:42 pm

Personally if I was going to haul a boat that many miles it would not be on one of their Karavan trailers. I would sell it and get a custom aluminum trailer designed to tow long distances. Torsion axles and less weight is a plus too in the long run.

The cost of replacing tires can be significant and the larger the tire, the more money. Replacing 13's every few months before needing to replace 14's is not going to save any money as 13's are much cheaper, especially if running radials. I also would doubt that you can swap a 13 for a 15 as there would not be enough clearance. I just replaced (4) 15" radials on my 26' SeaPig on the same rims to the tune of almost $600. 13's would probably cost about half of that and 14's around $450+. It is not all about revolutions.
On my 24th Whaler. Currently in the stable: 86 18' Outrage, 81 13' Sport(original owner), 87 11' Sport, 69 Squall(for sale cheap).

wild bill
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Re: Boston Whaler Use of 13-inch Trailer Tires

Postby wild bill » Wed Sep 16, 2020 4:01 pm

Hey biggiefl, looks like good advice.

[Please start a new thread if you want to change the topic to something entirely new. This thread is discussing Boston Whaler's alleged policy of putting trailers with 13-inch wheels under their larger boats so they look like an elephant on roller skates.--Moderator]
2016 Montauck with 200hp Pro XS Mercury, Karavan tandem axle trailer.