New member and already a tire question

[Maldos]

Great forum and yes I paid the $12, best money spent. My wife and I just purchase a 2007 2720 and are planning a multi-state trip in September. I wanted the A-frame, she wanted the room.

Currently the trailer has 14" wheels and new tires but I'm currently in the process of upgrading to 15" wheels and tires. Custom RV here in Ontario, CA quoted a fair price but the tire is made by a company called TRIANGLE. I've never heard of them. The tire size is 205/75/15 8-ply Radials with a load rating of 2150 lb. If they have the room after installing the lift kit can go to 225/75/15, again the TRIANGLE tire.

Question: are the two sizes OK, would the 225 be better? and most importantly what about this manufacturer?

I'm upgrading the new wheels with metal valve stems and a TST 507 monitor kit.

Thanks for all help, great sit and rally fooling forward to using my new trailer.

Don/Maldos

[Padgett]

a) I have 205x75x15s but is without a lift kit. Seems fine.
b) Might look at http://www.triangletire.com/index_english.html

[Bill]

I'm looking at the Triangle Tire web site for ST (trailer) tires - be sure to go to the USA site.

http://www.triangletireusa.com/stradial.html

The 205/75R15's seem to have part number 64348, and the 225/75R15's have part number 64351. I'm not seeing the specs you mention, Maldos. Of course, I'm not sure I understand the column headings, but Padgett, I bet you can tell us what they mean. For these two tires, the specs I would like to check and compare are

o Load Rating = 1820 at 50 psi, versus 2540 at 65 psi ??
o Ply Rating = 6 versus 8 ??
o Loaded Radius = 12.8 vs 13.3 inches ??

If I am reading those number right - and that's a big IF - the 205's are not an improvement in load rating over 14 inch tires. Misprint?

Bill

[rickst29]

Although built for 15" rims, the '64348' tires are only load range 'C' (and no increase in load capacity over the tires they make for 14" rims). Consider buying only the '64351' tires, which are a correctly fitting "upgrade" for an "older" TM with the lift kit installed. ("8-Ply", Load Range D.)

My own tires are the highly regarded Maxxis Load Range E (supporting up to 2830 pounds at 80 PSI). For comparison, here are my Maxxis specifications:

model: TL15713000
size: 225/75R15
'plys': 10
diameter: 28.3
section width: 8.9
Max PSI: 80
Max load: 2830
Measuring Rim width: 6
Tread: 9/32

"Loaded Radius" is irrelevant to rubbing against the TM wheel well. What matters is the total diameter, and it's 28.3 inches (same as mine). It's sized to fit a rim of "6.0" width, which is also correct. The Section width is 8.8", slightly less than mine. (That will work fine).

Are the tires "good"? I have no idea. But the dimensions are correct for doing the 14" -> 15" upgrade.

[Padgett]

What bothers me is that I see no mention of a nylon cap or overlay. I would not have a trailer tire without one.

For the Load or Ply rating this does not mean what it sounds like. Note that the operative word is "rating" and has nothing to do with the actual construction.

The real meaning for trailer tires is:

 ST-Metric Trailer Service Tires
Load Range | Ply Rating | Maximum Load Pressure 
       B           4            35 psi
       C           6            50 psi 
       D           8            65 psi 
       E          10            80 psi

and the only meaning you should take from this is the allowed tire pressure since the actual maximum load is a function of the pressure and is a standard.

So a 205x75x15 LRD aka 8PR has a maximum load of 2150 lbs at 65 psi
a LRC aka 6PR has a maximum of 50 psi and a 1820 lb max.

Note also that if you take the 205 LRD and only inflate it to 50 psi then the max load is 1820 lbs. It is a straight mathematical formula and the same for all ST (special trailer) tires.

Outside Diameter (OD) is the only other thing that really matters, the Static Loaded Radius is related to the revs per mile and the axle height but is not really mportant to a TM. TD-Tread Depth is going to be about 10mm for any trailer tire (have seen 12mm street tires) and are worn out when it gets down to 3mm (about 1/8").

Dual Load you do not need to worry about, it relates to dual wheels each side of the trailer. Only the 3326 has dual axles (tamdem). Section Width is just the chanber width in inches (205mm ~ 8").

Load Index (LI) is not commonly used with trailer tires. Rim Width (RW) I'd use a 6" rim for a 15 with a load rating of at least 2k lbs (5" rims are usually less - should be stamped on the wheel.) Tire Weight (WT) is usually in pounds.

So personally since I see no mention of a nylon cap or overlay (can also read in the ply information on the sidewall), I would not want these tires on my trailer.

I have enclosed the Triangle chart redacted a bit, the ply information from the sidewall of my tires. Note the "+ 1 nylon" at the end, and the wheel information - may be hard to see but is a DOT requirement.

So it has a 2 ply sidewall, 5 ply tread, and an 8 ply rating. Make sense ?

ps ALWAYS have trailer tires balanced when new or repaired. You will not feel a vibration but it is hard on the tires, axle & bearings, and what is inside the trailer. There is no shock absorber to mitigate.

[funpilot]

Originally Posted by rickst29

Although built for 15" rims, the '64348' tires are only load range 'C' (and no increase in load capacity over the tires they make for 14" rims). Consider buying only the '64351' tires, which are a correctly fitting "upgrade" for an "older" TM with the lift kit installed. ("8-Ply", Load Range D.)

My own tires are the highly regarded Maxxis Load Range E (supporting up to 2830 pounds at 80 PSI). For comparison, here are my Maxxis specifications:

model: TL15713000
size: 225/75R15
'plys': 10
diameter: 28.3
section width: 8.9
Max PSI: 80
Max load: 2830
Measuring Rim width: 6
Tread: 9/32

"Loaded Radius" is irrelevant to rubbing against the TM wheel well. What matters is the total diameter, and it's 28.3 inches (same as mine). It's sized to fit a rim of "6.0" width, which is also correct. The Section width is 8.8", slightly less than mine. (That will work fine).

Are the tires "good"? I have no idea. But the dimensions are correct for doing the 14" -> 15" upgrade.

What pressure do you keep in your tires and if at 80 does the trailer ride hard?

[Padgett]

The scientific way:

Take the expected max weight of the TM (sink door) less the tongue weight but plus any transferred from a WDH.

Divide by 2 (number of tires)

Add 25% (cornering, bumps)

Divide by max load of tire

Multiply by max psi

And the result is the pressure you should run.

Gut: Get LRD and inflate to 65 psi.

This is how I figured the inflation for autocross tires except didn't divide by 2 (hard corner all weight is on one side, used to carry the inside front tire over things. Won a lot of autocrosses.

I figre mine at 3800 lbs (probably closer to 3500 but what the heck). Tongue is 460 lbs, No WDH.

My 2720SL 205x75 LRD: 3800-460/2=1670 + 25% = 2087 / 2150 * 65= 63 psi nom. I run at 65 psi

225x75 LRE: 3800-460/2=1670 + 25% = 2087 / 2830 * 80= 59 psi nom

Now every tire manufacturer has charts which include things like rim width, temperature and load vs psi since the loads are not linear (use LRD and you get 53 psi) but good luck getting one.

[davlin]

Originally Posted by funpilot

What pressure do you keep in your tires and if at 80 does the trailer ride hard?

My way is not quite as "scientific" as Padgett's. I have Carlisle 10 ply rating, load range E 225x15's on my 3124KS. To get the full "E" load range capacity, they are supposed to be inflated to 80 psi. I found that to be too hard, based upon the "jumble" found in all the cabinets after I arrived at destination.

I've since backed off to 70 psi, which still provides a load rating higher than required for my trailer, and the ride is more civilized. You always want to make sure that whatever tire you have meets the load range requirement of your (fully loaded) trailer, but this is one of the times where "more" is not necessarily better.

Dave

[Bill]

Originally Posted by rickst29

"Loaded Radius" is irrelevant to rubbing against the TM wheel well. What matters is the total diameter ...

I stand corrected. Loaded Radius is the distance from the center of the axle to the ground when the tire is loaded. A loaded tire is flattened at the bottom, so the Loaded Radius is a bit less than half the diameter.

When thinking about the tire rubbing the wheel well, we need to know the distance between the center of the axle and the top of the tire, not the bottom. This is approx half of the Outside Diameter - not exactly, since the top of the tire bulges a bit under load, but close. Unfortunately, tire manufacturers don't seem to specify this upper radius, so maybe half of the OD is close enough, especially when comparing tires.

In the case of the Triangle ST225 tires, the OD is 28.3 inches, so the upper diameter is close to 14.15 inches, clearly different from the Static Loaded Radius of 13.3 inches. The difference, 0.85 inches, matters when checking for wheel well rub.

Thanks for picking that up, Rickst.

Bill

[rickst29]

Originally Posted by funpilot

What pressure do you keep in your tires and if at 80 does the trailer ride hard?

I don't use the full 80 lbs - because I think that would cause excess shaking of trailer appliances and contents. (IMO, the lightly-loaded tires would not behave with the correct amount of flexibility). But before you read anything further: Note that the TM manual AND nearly all tire manufacturers recommend that tires should ALWAYS be used at their maximum rated PSI.

Still, as Padgett has described, tire manufacturers know that tires should be inflated to less PSI when running with less load. It's hard to find the charts, but I've previously posted the chart for Goodyear Marathon ST tires here: http://www.trailmanorowners.com/foru...20&postcount=3

Goodyear's "Match your PSI to your tire loading" table for their Marathon ST tires recommends barely 40 PSI for the "65 PSI" Marathon D's at my weight. (Which is nearly 1900 when loaded with everything, including 40 gallons of water for boondocking). My original TM tires were exactly that tire: Goodyear Marathon 225/75 R15 "D", and I retired them due to "old age" - with the tires showing no visible issues at the time I took them off. But, because I'm chicken, I never went below about 50 PSI with the Marathons, and I apply roughly the same "tuning" to my Maxxis pair.

I run 'em at at about 55 PSI for California and roads with speed limits posted at 55 MPH and below. (Not exceeding 60 MPH actual). When a trip will present the possibility of saving a lot of time by driving faster, in States where that is allowed (including Nevada), I go up to 75 MPH at 65 PSI. (That's another Goodyear recommendation: add 10 PSI if you want to drive at higher speeds.)

I've discussed this concept of "tuning PSI to tire loading at great length in a couple of other Threads. But I never felt good about going as low as the Goodyear table figures, I've always added about 10 PSI to those values. And the notion of applying Goodyear "tuning" to another brand of tires is not recommended by any other manufacturer, and also not recommended by TM. (The TM manual says to always run at maximum rated PSI).