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Old 08-30-2016, 06:59 AM   #1
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Tire Opinions

We will be picking up our new Hummingbird 17RK at the end of October.

We ordered the Baja option, which comes with all-terrain style tires. After reading the specs on the tires that will come on it I have some concerns and would really appreciate some opinions.

The TT has a GVWR of 3,750 lbs. The tires are rated for a max load of 1,854 lbs. each (3,708 lbs total load rating) and are size P235/75R15SL.

Two things are bothering me, first is the obvious possibility of overloading the tires, but more so is the fact that they will be passenger rated automobile tires.

I'm sure they will "work" or the manufacture wouldn't put them on, but the engineer in me is coming out strong on this one.

For longevity and dependability (and mostly for peace of mind) I'm strongly considering having the dealer swap the two tires (plus the spare) before we even pick it up. The factory tires will have an O.D. of 28.9". I'm looking at replacing them with Maxxis M8008 ST 225/75R15 in either 8-ply (2,540 lbs.) or 10-ply (2,830 lbs.) which have an O.D. of 28.3"


I may be seeking a solution for a problem that doesn't exist, but does anyone see any issues with switching to the Maxxis tires?


It will probably sound like a waste of $350 for most of you, but given that our current TV will be close to maxed out, I'd rather error on the side of caution.

Thoughts?
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Old 08-30-2016, 07:30 AM   #2
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I believe the axle rating on your Hummingbird will be 3500 so the 3708 rating for the tires is fine. Since the tongue weight is carried by the TV and not the trailer axle you can reach the max 3750 GVWR without exceeding the 3708 load rating of the tires. If you assume a 12% tongue weight when loaded to the max 3750 GVWR it amounts to about 450 leaving 3300 on the axle or about 88% of the tire load rating.

This is the same set up as my 195RB Baja though it came with LT235/75R15 tires with a load rating of 1935 each or 3870 total. My scaled weights on the 195RB Baja ready for a long trip is 3700 total, 430 tongue and 3260 on the axle. We have close to 8K miles on our unit with no tire issues.

Make sure that you keep the TT tires inflated to the max sidewall pressure and I think you will be fine. Under-inflation will cause you more trouble than anything else.
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Old 08-30-2016, 07:43 AM   #3
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Good point, I wrongfully assumed that the entire gross weight would be placed on the TT axel and didn't account for any tongue weight transferred to the TV.

I just see that P-rating and think back to my last Tundra and the difference when hauling a load in the bed between the factory P-rated tires and the aftermarket D-rated I switched to.

Makes me imagine excessive sway due to tires, but this may be apples to oranges considering it's a TT.

Thanks for the input!
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Old 08-30-2016, 08:09 AM   #4
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On another note -

I have a tongue weight scale, so if I measure the dry (unloaded) tongue weight when I get it home and then remeasure after loading, I should be able to get close to GVW based on tongue weight ratios?

I realize that I will need to hit the scales to confirm, but just trying to see if I can get a rough feel for overall TT axle load through measured tongue weights and published dry weight of the TT from the factory.
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Old 08-30-2016, 08:32 AM   #5
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The tongue weight will vary depending on what you load and where it gets loaded in relation to the axle. I would estimate how much your stuff weighs as you load it so you have some idea of overall trailer weight in order to estimate tongue weight percent when you use the tongue scale. Don't forget to account for whatever you are carrying in your holding tanks. At 8.3lbs/g water adds up and these smaller units don't have a lot of cargo capacity. Once you get things estimated then run it over a CAT scale to get your final numbers. It's nice having the tongue scale so you can easily see what the affect is of different loading scenarios.
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Old 08-31-2016, 11:26 AM   #6
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Quote:
Originally Posted by 01tundra View Post
On another note -

I have a tongue weight scale, so if I measure the dry (unloaded) tongue weight when I get it home and then remeasure after loading, I should be able to get close to GVW based on tongue weight ratios?

I realize that I will need to hit the scales to confirm, but just trying to see if I can get a rough feel for overall TT axle load through measured tongue weights and published dry weight of the TT from the factory.
I think you are way over thinking this.

Its a camper - not a utility trailer. It will be near impossible to load that 17footer up to over the GVWR of the trailer.

Trailer sway won't be a problem if you just keep the tires aired up properly... again, this isn't a backhoe transport trailer.

Rest easy and camp on! have fun.
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Old 08-31-2016, 12:00 PM   #7
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I didn't know that a trailer manufacturer would put P-metric passenger car tires on a new trailer.
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Old 08-31-2016, 12:28 PM   #8
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Me neither. It would be interesting to hear from others with single axle trailers.

I guess they assume won't be stress as on a double axle trailer. $350 would be acceptable for me in the peace of mind dept., but I don't understand why they put P rated tires there new.
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Old 08-31-2016, 01:28 PM   #9
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It's because of the Baja package we got due to the angle of our driveway.

The non-Baja version has LT tires.

The Baja option comes with the Trail Guide tires.

After looking them up on the manufacture's website, it appears that they are load range SL rated at 2,039 lbs. @ 44 psi.



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Old 09-01-2016, 06:01 AM   #10
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Originally Posted by ctbailey View Post
I think you are way over thinking this.

Its a camper - not a utility trailer. It will be near impossible to load that 17footer up to over the GVWR of the trailer.

Trailer sway won't be a problem if you just keep the tires aired up properly... again, this isn't a backhoe transport trailer.

Rest easy and camp on! have fun.
While I agree that I could quite possibly be overthinking this, because that's what I usually end up doing, the part about near impossible to reach GVWR I'm not too sure about.

The trailer dry weight with no options is 2,950#. With all options it will come in around 3,150#, if not more. I will weigh all of the normal gear that will be stored in the front compartment (electrical cords, adapters, hoses, leveling blocks, etc.) this weekend to confirm, but I'm going to guess around 200#. Throw the two mtn. bikes on the front carrier rack and that's another 50#, kitchen utensils/hardware maybe 50#, add in another 50# for misc. items.

Just that right there would put the TT overall weight at 3,500# with an empty fresh water tank and the TT's GVWR is 3,750#.

Now add in the 25 gallon gray water tote that weighs 35# (and won't fit in the back of the TV) and clothing/linens/etc. and we're pushing 3,600#+. That gives us a buffer of 150#.

Plus, I'm a blacksmith....so I know I'm going to have to forge some misc. decorative items holders for it to make the camp director (wife) happy.

Maybe I'm being overly conservative, but in these smaller, lightweight TT's I can see them getting pushed close to their GVWR fairly easily.

Am I wrong in my assumptions (I sure hope somebody says yes )?
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