D's or E's

[Speckul8r]

So, I've done the lift kit deal and am getting ready to get some new 15's for the TM. I see a number of folks moving to Load Range E's and I'm wondering if this is a good idea. At first glance this seems cool (more plys on the sidewall etc.) but looking further, I'm not so sure. E's look to be 80 psi tires which will probably make the TM bounce quite a bit so then the thought is to deflate and thus derate the tire.
(http://www.maxxis.com/trailer/traile...nflation-chart)
I went to the Michelin web site suggested by wmtire (which has evaporated on me) and they are saying that a tire that is has less than 20% of the suggested inflation pressure is defined as flat. So, using that logic, if you run a E rated tire at 65 lbs, you are 1 lb away from "flat". Too close a margin in my book.

I don't know how a TM with D tires on it will ride at 65 lbs. but even at 60 lbs I'm thinking it should be OK.

What are your thoughts??

[wbmiller3]

After installing the lift kit I went to Goodyear Marathon ST225/75R15 load range D rated for 2540 lb each at 65 psi. That is plenty of margin for me over what the 2619 weighs. I run them at 65 psi and we haven't noticed any effects in the trailer from bouncing.

(When I weighed my new truck and TM in 2003, the trailer weighed 2720 pounds in a ready-to-garage configuration.)

[Padgett]

A lot of mixed thinking here. First is that mine towed nicely on the stock 215x75x14 LRC at 65. At the same time I felt that a 1820 lb tire on a (potentially) 4000 lb trailer was overloaded. My TV is 4475 lbs and has tires rated at 2200 lbs each. In theory two could hold the whole car (and I used to figure pressures that way when autocrossing). However that is 2200 lbs at 51 psi and the recommended inflation is 33 psi. Linear math (CEFGW) give the load per tire at that pressure to be 1425 lbs or 5700 lbs (car plus 1200 lbs). Sticker on car shows that tire and pressure to be good for a gross weight of 6500 lbs. Also while the 4475 lbs is almost 50-50 the GAWR Front is 3200 lbs and rear 3700 lbs (towing package).

Note: you really need the tire load chart for that specific tire to be exact but few thing are and why I run the heep at 36 psi instead of 33. If the load is increased, I would increase the pressure to match.

OK back to the TM. My 2720SL (seems to be the most common size) has a chart on the sink cabinet door with rated weights (see below). It also has an odd double inflation sticker (have never seen one like this before & suspect there may have been an issue.

Put them together and it seems evident that the stock 14" LRC is at the limit of its capacity. Not good.

At the same time I really do not like to raise the CG on anything. Posts indicate that some modes can sway though whether overloading or underinflation is an issue I do not know. Can say mine felt quite stable at 65ish mph even when being passed by semis do 70+. OTOH it weighs about 1000 lbs more than my previous tow car, a minivan.

Back to the TM. Every trailer I have had before rated over 4,000 lbs was a tandem axle so a single axle is new to me. Have had tires blow and once had the whole neck snap off a race car trailer at 70 (interesting experience but did get to drive an A/SR to the next exit...)

OK, the weight rating (both places) is for a 4200 lb max and likely 3800 lbs normal. Take off 400 lbs for the tongue and that leaves about 3400 lbs typ. or 1700 lbs load per tire so long as your companion does not pull a Lucy (see here ).

OK so looking for a standard trailer tire with a max load of at least 4200/2 = 2100 lbs and a diameter close to the stock 215/75R14 LRC 26.7" I found a 205/75R15 LRD rated at 2150 lbs @ 65 psi and with 1/4" less wheel well clearance (1/2" larger diameter). I'll probably run at that pressure and maybe put a g-meter in the coach to record shocks.

Few more notes:
1) This tire must have at least a 6" rim (is marked on the wheel somewhere). 5" rims may not have the load capacity.
2) Loads are for ST (trailer) and LT (light truck) tires, P-metric (passenger car) should be derated 20% on load.
3) Trailer tires should have a nylon overlay (not cap) for added strength and heat resistance.
4) I carry an IR heat gun (HF 93984 or 60725 and will check the tire and bearing temperature at stops on the road. They are handy for all kinds of things.
5) Any tire with an "ST" in its name or destription is a trailer tire and only rated for 65 mph.

Suppose this should be in a FAQ but this seemed the right combination for my needs. YMMV.

[TM Pilot]

Originally Posted by Padgett

Few more notes:

3) Trailer tires should have a nylon overlay (not cap) for added strength and heat resistance.

To be a little more precise, the "nylon overlay/cap/cap ply" construction is distinguished from the "nylon strip" construction - with the nylon overlay cap arguably the better construction.
http://dasselaw.com/design_defects.html

[tentcamper]

Goodyear has a load to tire inflation chart for their ST tires. If I went to 225/75/15 goodyear tires. My 2720 weight is around 3,700 loaded, with 390 tongue weight. So the axle is carries around 3,300 divided by 2 for what the each tire carries is around 1,650 lbs.

I would get the load range D tire since it is a stronger construction and only abut $5 more at samsclub then the load range C.

Per goodyear charts attached on page 9 for the 225/75/15 tire. If it's a load range C or D, I should inflate to 35 PSI. I would add 10 psi for the service bulletin for traveling over 65 MPH. Never know when I might go over 65 mph. I would air up my tires to 45 psi.

http://www.goodyearrvtires.com/pdfs/tire-care-guide.pdf

[Speckul8r]

I think that we are looking at 2 different things on the chart you referenced.
The "C" tire would have only a 1760# rating at 35 psi. Way too little IMO. You will have to inflate it to 50 psi to get a 2150# rating. Should be OK. But I'd do the "D" at 60 or 65 psi w/2380 - 2540# rating.

I'm still thinking about the Maxxis "E" 225 75R15. From other posts, this tire runs smooth with little or no excess bounce.