Don't use radials tires due to load?

[The_Handier_Man1]

From: EvilStopeCat  (Original Message)
Sent: 4/24/2004 8:39 AM

Hello,

I just bought a 1979 Dodge M-400 which has 17.5 inch Bud rims.  The MH is in terrible shape.  I decided to replace tires.  The owners manual is emphatic about not using radials due to loading.  Based on some past posts here I take that to mean the rims won't take the pressure.

How have people solved this?
I can easily find 8R17.5 radials locally, but not bias tires.
Could the rims have been replaced by PO (how can I tell)?  What about replacement 16 inch wheels?  I found a web that has 16 inch rims with the requisite 8 stud 6.5 inch circle, 4.75 inch center wheels but will they fit?  Anyone know?  I wonder whether they will clear the drum/disk (they are 6 inch rims).  For giggles check out the site www.wrightparts.com and check out the Dually rims.  If these rims would work I suspect the rim/tire combination would cost the same as 8R17.5 tires alone.

thanks,



From: denison
Sent: 4/24/2004 12:53 PM

Before you look at getting smaller rims sizes, you have to make sure they have the same load rating, and will take tires of the same load rating as the originals did. And you have to check that the mounting offset will allow the tire sidewalls not to come within about an inch of each other when mounted on the rear axle. 



From: EvilStopeCat
Sent: 4/24/2004 5:20 PM

The tires still trouble me.  I may invest in one 16" wheel and go to town with it.



From: Enigma960080
Sent: 4/24/2004 8:22 PM

http://www.tirerack.com/tires/Sizes.jsp?make=Yokohama&model=Y785R

for  8R17.5 radials....   I  have an 80 Chieftain 27 ft,   I am  carrying a HUGE load  when  fully loaded. ( I have not weighed it loaded  yet)  but I have  had no issues running radials  over bias.   



From: Sea Hag
Sent: 4/24/2004 9:44 PM

I have a 76 M400 chassis with the same rims as your 79 - There are yokahama radials on it and they are doing fine - no problems - I know many other members are running radials as well - You have to realize that your owners manual was written 25 years ago , and they have come a long way with radial tire technology since then . Sea Hag 



From: EvilStopeCat
Sent: 4/25/2004 12:28 AM

I hear you about tire technology Sea Hag.  The unit I bought has all radials, but, the owner's manual says the rims are the problem not the tires.  The bias plys in the owners manual were supposed to be pressured no more than 60 psi.  The radials on the MH say 80 psi.  Still a little scared even though I drove it home from Arkansas 55 to 60 mph with no problem.  Thanks for the input.



From: Enigma960080
Sent: 4/25/2004 12:45 AM

If  its  any consolation,  I run loaded  at 70 PSI  and up to 70 MPH.... but  then my  tires  are new...   a few  years  down the road  I'm  sure  I will  slow it  down a little



From: denison
Sent: 4/25/2004 6:28 AM

EvilStopeCat: Dont forget the pressure on the sidewall is the maximum for the tire, not a minimum. Its what the tire maker lists for the max. load listed next to it. The 17 inch front tires on my 72 have a sidewall maximum of 90 psi, for a load of 3170 # per tire, or 6340 # for the axle. The front axle is rated at 5000 # but only carries about 4500 #, so there is no need to run 90 psi. I run 75 psi in the fronts, and 65 psi in the identical tires on the rear axle, and they all run at the same temperature. I alway check my tire pressures before I start out, and check my tire temperatures after an hour or two of driving - like at the rest stop of when stopping for lunch. Any tire thats running warmer than the others is a danger signal. 



From: EvilStopeCat
Sent: 4/25/2004 10:15 AM

Good point.  When you check after two hours what pressure are you looking for?  If you start out at a cold of 65 after a couple of hours it is what about 70?



From: 70winnie
Sent: 4/25/2004 10:21 AM

How does one go about checking tire temperature?  What's considered the acceptable max temp?



From: EvilStopeCat
Sent: 4/28/2004 6:39 PM

I think I have a solution to my problem.  After seeing a post (a negative one) I contacted Denman Tires.  They recommended a local distributor.  The local distributor tells me they can get 8.00x17.5 bias ply tires ($90 locally) within about a week.  The warehouse has 6 in stock and can order more.  I think I'll go this route

Thanks to all for the comments.  I hope the tires don't crater, but the dealer believes that I'll rot the tires before they fail (I doubt that since I plan about 7,000-10,000 miles per year).



From: denison
Sent: 4/28/2004 8:02 PM

If my tires were 75 psi when cold - being maybe 80f degrees, I would expect they could be between 90-100 psi when really warm, after 2 hours on the interstate on a sunny day. As for the temperature, when they were at their hottest, in temps of over 100 in the shade, and the tires had been on the sunny side driving on black pavement - I could hold my hand on them indefinitely. It was too warm to be comfy, but it wasnt pain either. If you leave a steel wrench lying in the sun for a while on a hot sunny day - the tires werent as hot as the wrench gets. I will have to remember to measure the pressure and temp when I next drive it for over an hour at highway speeds. 



From: HeavyHaulTrucker
Sent: 6/6/2004 3:56 PM

Denison Said:

EvilStopeCat: Dont forget the pressure on the sidewall is the maximum for the tire, not a minimum. Its what the tire maker lists for the max. load listed next to it. The 17 inch front tires on my 72 have a sidewall maximum of 90 psi, for a load of 3170 # per tire, or 6340 # for the axle. The front axle is rated at 5000 # but only carries about 4500 #, so there is no need to run 90 psi. I run 75 psi in the fronts, and 65 psi in the identical tires on the rear axle, and they all run at the same temperature. I alway check my tire pressures before I start out, and check my tire temperatures after an hour or two of driving - like at the rest stop of when stopping for lunch. Any tire thats running warmer than the others is a danger signal

Denison, I have to disagree with you.  The numbers on the tire sidewall are the RECOMMENDED tire pressure; the weight rating is a maximum rating at that pressure.  Failure to inflate the tire to that pressure will result in the tires running warm, not giving you your best fuel mileage, and -- in extreme cases -- tire sidewall failure.  Remember the Ford Explorer tire failure lawsuit?  All of those failures were caused by Ford's "pre-empting" the manufacturer's inflation recommendation for that tire in an attempt to make a car that rode like a pig ride like a Cadillac.  The lower inflation pressure that Ford required caused overheating of the tire, and in some cases, actually caused the tire sidewall to fail from rim pressure on the area just outside the bead area.
Even though you are not loading a certain tire to that rating, it is important that the inflation pressure listed on the sidewall be adhered to.  Radial tires will take a 30 to 50% over-pressure, which is designed into them -- but they are very unforgiving when they are under-inflated.
This advice is based on 30-years of buying, using, maintaining, and replacing tires -- and some very good information given to me by a man who lived and breathed tires for over 50 years (Larry Barkley of Fremont Tire in Sioux City, Iowa).



From: JeepNut77
Sent: 6/6/2004 5:04 PM

I have to agree with Heavytrucker on this one.  Even tho I air down my off road tires to about 15 psi for traction.....and when running for long stretches on pavement with low pressure deffinatly causes the tire to heat up due to the constant flexing of the rubber.  Recommended pressure puts the tire in a position not to flex beyond it's heat causing range of motion.



From: Sea Hag
Sent: 6/7/2004 11:56 AM

I also agree - I run the recomended tire pressure marked on the side wall on all my vehicles regaurdless of load and not be swayed by the owners manual . the fuel millage alone is a big point now days . I've also had alot of experiance hauling heavy equipment and gravel . I was taught heat was a big isssue with under inflated tires and to go by the side wall rating to get the most millage and saftey out of sometimes very expencive tires . - Sea Hag 



From: 73RVDUDE
Sent: 7/16/2004 9:32 PM

my 73 came with radials



From: ErikGatz
Sent: 7/17/2004 12:34 PM

OK, back in the day when these awesome machines were made the Bias ply tires were the standard.  Today though, Radial tires are.  In the industry that I work in, Bus & truck Dealerships, all those huge rigs run is Radials.  radials are safer, more reliable, give you a better ride from the first second you start rolling(no flat spots), and a one piece rin that a radial(tubless)tire runs on is also much safer than split rims that were original on these beasts.  So, your question about radials not taking a "load"... these rigs dont really have a load compared to what I see everyday.  If 80,000 GVW rigs run Radials, I would say that there is no load limitations for radials.  All I know is that I wouldnt be caught without radials.  They will get you through. 

Erik Gatz,
Seattle, WA



From: Matt_Elyash
Sent: 7/18/2004 8:57 PM

I replace the split rims with all steel rims thru Les Schwab tires. They did the rims, had the mfr powder coat them white for me, and mounted some great radials on it for me. The ride is far far FAR better than with the scary and out of date bias ply crap I had on before, and I have the confidence in the radials born of solid technology meeting the road.

Feel free to Email me if you need info.

Matt



From: elandan2
Sent: 7/19/2004 2:29 AM

Hi,  The rims on your chassis were not designed for radial tires and as such, if you mount them and inflate them to the pressure required to carry the load on them the rim could split at the bead.  Dodge issued a service bulletin ( I'm still looking Denison ) addressing the issue.  The bulletin said that the 17.5 in rims on M-400 chassis could not run radials and the 19.5 in. rims could use radials as long as the load did not exceed 2500 lbs. and the inflation pressure did not exceed 75 PSI. 

Hope this helps, Rick



From: ErikGatz
Sent: 7/19/2004 3:50 PM

I agree with Matt, change the rims to solid one piece, and get radials.. youll never feel more stable on them.

Erik



From: 70winnie
Sent: 7/19/2004 9:28 PM

You should definitely not mount radials on splits the way you would mount them on solid rims, but the truck tire store I shop at assures me that radials can be mounted on splits with full reliability as long as you add tubes and liners.



From: HeavyHaulTrucker
Sent: 7/20/2004 2:53 AM

Yes, but then you limit your speed on hot days to below 60 mph.  The added tubes and liners drastically increase overall tire temperature, and reduce tire life and reliability.

Does anyone remember, back in the late 60's, how frequently you saw truck tire rubber laying all over the road?  Well, big trucks were still using tube-type tires; one-piece rims were just beginning to become prevalent, and tubless tires did not really begin to catch on until the mid-70's.  There used to be two big companies (McCurdey and Monfort) who ran their trucks at high speeds (now you know why the left lane of interstates used to be called "the Monfort lane") -- these two companies averaged 1 to 2 tire replacements per trip because of heat related blowouts or "cap peels".

John



From: lockman
Sent: 7/31/2004 1:49 AM

One of the oringinal questions was could you replace your 17.5 with 16" rims. Yes. Our 78 D23 came with  newer 16 inch rims and radial rubber. The spare was still old bias ply on a 17.5" rim. We had lots of concerns about this, and asked lots of questions of tire dealers and auto wreckers as we needed to replace (match up) the spare. As it turns out when cleaning the dust off the rims to find ratings, there were lots of warnings to use the appropriate "FORD" flanged wheel nuts. It turns out Ford and Dodge used the same hole pattern and alternating "coned" wheels and flanged nuts. Used on duallies and cube vans these wheels are rated for the correct weight but only 80 PSI. Our rubber is load range E and also correct for the weight of our shorter unit. The 16" set up does look a little odd (small) and probaly effects our top speed, but budget says there staying. No problems clearance wise with disc brakes on the front, drums rear. Only have ten miles on the rig, enough to get it home and fix it up, handled fine on secondary highways. Hope to roll it out next week for a real test run.