View Full Version : Confused on tire recommendations for Monty 3670RL

05-08-2016, 09:34 AM

Newby here and it looks like I need to change the tires on my new to me 2003 3670RL due to age and some that are Marathon branded. Reading all I can in the forums on this subject but I don't mind admitting I'm a little confused. I have found several conflicting weight specs for my trailer with 10,350 lbs being the most consistent with 3,600 lbs carrying capacity. Are those numbers accurate? And what is the stock axel rating? Based on those two numbers then, what would be the tire recommendations for safety, LT or G rated tires and recommended size? I want to buy tires in the next two weeks before a long trip so your help would be greatly appreciated. I know an accurate loaded trailer weight would be best but I am nervous about towing the trailer to a weigh station with these tires.



05-08-2016, 10:43 AM
For your camper G rated tires would be your best choice.

05-08-2016, 11:09 AM
Thanks and I guess I need to see if my wheels are rated for 110 psi, correct. I understand that rating is on the back of my wheel


05-08-2016, 02:05 PM
Unless your wheels are not the factory ones, you'll probably have 80# wheels and should be looking for a good LT tire.

05-08-2016, 02:17 PM
You wont any thing but ST tires. Like Dick said you probably have 80 pound rims LTs will work just fine.

05-08-2016, 03:59 PM
The original ST tires were probably rated for over 3,400 lbs. But some LT tires are rated at less than 3,100 lbs. So look at the load ratings carefully if you decide to consider LTs.

My original STs were rated for 3,420 lbs if I remember correctly. But the Michelin XPS Ribs (LTs) I replaced them with are only rated for 3,080 lbs. That is fine in my case as I have a shorter and lighter trailer. But may not be suitable for a heavier trailer.

05-08-2016, 04:15 PM
What are the premier recommended LT tires?



05-08-2016, 05:54 PM
Don't make any purchase until you get the rig weighed. Ideally, each individual wheel with the trailer fully loaded like you normally travel. If you can't get wheel weight, at least try to get weights of each axle. Then you can decide on what tires to go with. At the very least, go with, maybe the Sailuns, and just air them to 80 psi. The tires will work just fine at that pressure, and you will have the advantage of a really tough tire.. G614's, just because of the price, would be overkill, unless that isn't important to you.

05-08-2016, 06:30 PM
Sound logical but I didn't think you should run the Sailuns under pressured?


05-08-2016, 07:08 PM
Just like the pressure chart for the G614's, the tires have a different weight capacity at each pressure. From the Goodyear tire inflation chart, available at http://www.goodyearrvtires.com/tire-selector.aspx , and for tires run a singles, not duals, the weight capacity for the G614 is as follows,
80 psi- 3042
85 psi- 3170
90 psi- 3300
95 psi- 3415
100 psi- 3550
105 psi- 3675
110 psi- 3750

You would need to get the Sailun chart for their tires, but I'm sure they also have a range of pressures that have a different weight carrying capacity for each pressure. This is no different than any tire application for a car or truck, the sidewall will give a max inflation pressure, but the manufacturer say inflate to a certain pressure due to the weight and of course ride quality.

05-08-2016, 11:19 PM
Great thanks Bob,

Now I'll start searching the net for that Sailun chart.


05-09-2016, 02:50 AM
ST tires are rated higher because they are held to a much lower standard. They don't haft to carry passengers

05-09-2016, 06:21 AM
If you could find the 65mph capacity of an LT tire,you would see a MUCH higher load rating than that of an ST tire, which is maxed out at 65mph. Or in the case of a G614 75 mph. The LT tire would have still have a MUCH higher load rating at the 75 mph.

Dam Worker
05-09-2016, 04:29 PM
I think the Sailon are also rated for 75 MPH. They are also rated for 4080 at 110 pounds per square inch if I remember correctly. Are the Goodyears only rated for 3750? That is what the earlier post showed. I am not sure how the LT tires stand up or do as a trailer tire but everybody has their own opinion.


05-09-2016, 06:04 PM
Reading older posts, most seem to be advising against running G rated tires at 80lbs PSI. So I am again uncertain as to what tires to buy.


05-09-2016, 09:10 PM
quote:Originally posted by fauch

If you could find the 65mph capacity of an LT tire,you would see a MUCH higher load rating than that of an ST tire, which is maxed out at 65mph. Or in the case of a G614 75 mph. The LT tire would have still have a MUCH higher load rating at the 75 mph.

This is the first I've heard you can go over 65 mph on these tires. I always have capped speed at 65 mph because of tires.

05-10-2016, 06:16 AM
A friend of mine from Canada had to upgrade tires while on vacation in Florida, and had the Sailuns installed on 80# rims on a SOB, and the dealer there said he installs them that way regularly with no problems. On his return trip home he had no problems, and said it was the best his rig had ever towed. JT

05-10-2016, 08:39 AM
Hey Robert,Just installed my second set of B.F.Goodrich Commercial TA2 last Friday 05/07/16.I have a 2007 3485SA with 6,000 lb axels.I did a trip across country last year almost 10,000 miles no problems.Tires were 6 years old so replaced.One thing, tell the tire guy you buy from you want tires that are as close to new as possible.This is May my tires were made in January of this year.Hope this helps Steve 1952. From Denver N.C.

05-10-2016, 04:34 PM
Thanks for all he good info guys. Is the 3670RL heavy by today's standards when comparing 36' 5th wheels?


08-03-2016, 09:07 AM
quote:Originally posted by Winmagbar

Great thanks Bob,

Now I'll start searching the net for that Sailun chart.


Hi Robert,
I just happened to find this thread. We're having some of the same questions as you posted and I'm wondering if you found a Sailun chart? I've been looking and can't find one. I did find a Goodyear chart thanks to the link Bob posted.

08-03-2016, 11:29 AM
Interesting on 75 MPH because when I looked at the Goodyear site the charts said 65.

08-03-2016, 01:24 PM
I had LT tires on my previou 5ver and they ran much better then the ST's that were on it. I am getting ready to put LT's on my 3670 soon. Most likely a LT 265/75/16 or maybe a 285/85/16. Since mine is about 13,500 lbs......minus the pin weight of 2200....figured I am good for tires rated for 3100 lbs.

08-03-2016, 01:39 PM
To the best of my knowledge back in 2003 Montana's came with Lt E Rated
My 2002 did both of my friends 2003's also.Back in those days no tire problems!
This all started when some of the recent units have become extreamly heavy!
Trust me LT tires will work just fine on your unit.