Blown tire update. - Page 4 - Montana Owners Club

cargary · 06-30-2005, 05:12 PM

Steve:
Belive it or not, the weight on the front axle of the truck actually increased by 40 lbs. Does that mean that I add or subtract the 40 to the rear axle for the exact pin weight?
Glad I finally explained the process I took satisfactory. Some times I miss a step when I explain things. Carole has the confused looks on her face now and then. I guess I know why now. Sorry about that. Thanks for the help understanding this issue.
Gary & Carole

RMccord · 06-30-2005, 07:49 PM

dgullick
I will check the axle ratings this weekend and post. I now that the potential GVWR of my 335 is 11100. Dry is supposed to be 8450. I suspect I am about 9500. Will probably weigh it tomorrow.
Thanks
I would like to get your opinion of your new tires after you get some miles on them.

jars · 07-01-2005, 08:03 AM

Tires
I have been in rving for 15 yrs had all kinds blowed all kinds until I went to Mechlin xps all steel radials. They ara a comerical truck tire. I have 33000 thousand on them. We have been in the desert heat 107 and didn,t have any tire problems. Our 3670 weights 10,000 on the trailer axel.
jars
Richard E. Smith

cargary · 07-01-2005, 01:53 PM

Richard:
What size Michelin tires do you have on your 3670 model? Do you know the number of the tire and the load rate class it is, such as a D or E load rate? Thanks for any feedback you can provide.
Gary & Carole

sreigle · 07-04-2005, 05:02 AM

Quote:

quote:Originally posted by cargary

Steve:
Belive it or not, the weight on the front axle of the truck actually increased by 40 lbs. Does that mean that I add or subtract the 40 to the rear axle for the exact pin weight?
Glad I finally explained the process I took satisfactory. Some times I miss a step when I explain things. Carole has the confused looks on her face now and then. I guess I know why now. Sorry about that. Thanks for the help understanding this issue.
Gary & Carole

Gary, add that 40 lbs to the pinweight. I **think** it is most common to see additional weight on the front axle. That probably is because the pincenter in the hitch is forward of the center of the rear axle. So some weight would go on the front axle. What you discovered is your pinweight is 40 lbs more than you thought!

Another way to calculate it is to add front axle and rear axle weights when hitched up, add front and rear axle weights when unhitched, then subtract the two. Then you don't have to worry about adding the change in the front axle weight to anything else. If that makes any sense.

On mine it reduced the weight on the front axle so I subtracted that amount from the pinweight. That tells me the hitch pincenter is slightly aft of the axle center, making the pinweight act as weight on a lever, raising the front slightly, kinda like a teeter totter. That's probably why the truck got about an inch and a half of squat when hitched up and I had to add airbags. The installer told me he put the hitch pincenter deadcenter over the axle center which is where it is supposed to be on a shortbed truck. Now I know he missed it a little bit. I think. I could be wrong about this.

The additional weight on your front axle means the hitch pincenter is forward from the axle pincenter, which is where it should be on a longbed truck. Often installers will put the pincenter forward of the axle center on shortbed trucks, too, but that further restricts turn radius. With the Montana that's not that big a deal since the curved nose gives us more turn radius. 'Conventional wisdom' is that the hitch pincenter should never be aft of the axle pincenter so our installer probably screwed up. It's not enough to be a problem, it's just not as it should be.

Pete Hanson · 07-05-2005, 07:45 AM

All this information has been very helpful and timely. I have an '02 2955 RL with the General LT235/85R16 tires on it. I picked it up used but very clean and it looks like its hardly been towed. We absolutely love it. My question is this. Is there any reason I shouldn't be running those tires at 80 PSI even if I'm well under the tagged total gross weight of this 5er? The kid that checked me out at the dealer checked the pressure before we left and said that the tires were at 60 PSI where they should be. I suspect he was wrong and today I pumped them up to 80 PSI cold before heading out on a 400 mile trip this coming Saturday.

sreigle · 07-05-2005, 09:36 AM

If they are load range E with max of 80 then 60psi seems awfully low to me. That would be a prescription for a blowout on a long run on a hot day, in my estimation. I think with your weight I'd run them at 80. If I found things bounce around an awful lot I'd try them at 75 but no less than that. Just my opinion. If you can weigh the axles with the rig loaded and hitched up then try to find a load chart for your tires and see what minimum psi it recommends.

cargary · 07-05-2005, 05:05 PM

Steve:
Thanks for the additional information on the pin weight location and how it affects adding additional weight to one or the other truck axles. In my case, the 40 lbs isn't enough to be too concerned about, but then again when you get closer to the max. allowable pin weight, each additional lb counts against you.
Also in my case, as we have calculated the weight on our 5er tires are a little over the 3042 called for, I wonder how much overweight causes one to do as Stiles did and move up to a higher load range tire? Any ideas at what point to do this Steve?
Thanks,
Gary & Carole

Jetson · 07-07-2005, 06:44 PM

Take those General tires off before they tear up your trailer!
Michelin XPS Rib 235/85R16 Load Range E here.

sreigle · 07-11-2005, 06:40 PM

I'm not an expert here but if you are over on the tires on both ends of an axle then you may be over the rating for the axles themselves. Your 2005 model may have 7,000 lb axles, in which case that's not a problem. Ours are 6k axles. Also, if you go to heavier tires, make sure the rims are rated to handle the additional air pressure. You might need to replace the rims, too. I understand the rims should be marked with their rated psi. If you are over on the tires I'd recommend going to something heavier or lose some weight. Get those tires out on a hot day and drive enough for the heat to build up and you're at high potential to blow a tire, in my estimation. As noted, I'm not an expert on this. We may have some members who are, though. Maybe they'll pick this up and help more than I can.

cargary · 07-12-2005, 05:14 PM

Steve:
Thanks for all the info that you have been able to offer. I didn't mean to have you think that I thought you were the expert on this subject. You were the only one that consistently replied to the questions that I asked and I do appreciate it. Thanks for what you were able to offer - I hope that I have knowledge in some area that I can offer you assistance sometime.
Gary & Carole

sreigle · 07-12-2005, 07:29 PM

Another thing to keep in mind if you upgrade the tires. Someone on MOC recently pointed out that the valve stems also need to be rated to handle the psi of the higher rated tires. Otherwise they can fail. That's something I would not have thought about.

Thunderman · 07-13-2005, 06:02 PM

I agree with Steve, keep those 23585r16 tires inflated to 80 psi. It will reduce the heat buildup. Good luck!

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