Deano7
Redmond, WA
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Joined: 09/23/2009
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I've been reading the posts here for several years but only recently joined in order to post. I'll keep this as breif as possible. I bought new tires at Les Schwab for my 2004 Southwind last year and didn't realize until I had left that these tires had a much higher air pressure. Old tires 80 lbs, new tires 120 lbs. Otherwise they seem about the same, they fit my old rims. Problem is now the steering is horrible on rutty roads, my rv tends to wander back and forth continously. It's better on good roads. Would a steering stabelizer help clear this up?
Thanks!
Deano7
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liborko
Surrey, B.C.
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Joined: 02/27/2006
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Your new tires are very likely load range G instead of load range F. Keep the same pressure as before, 80 PSI or go on scale and adjust your pressures according to load/pressure tables.
I recently installed Bilstein steering stabilizer on my class A on Ford F53 chassis and the improvement is very noticeable.
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Deano7
Redmond, WA
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Would there be any kind of safety risk or uneven tire wear to reduce the pressure down to 80?
Thanks for your help.
Deano7
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SunflyerA
Andover, Minnesota USA
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Look for inflation tables on the web site of the manufacturer of your tires. Set the pressure according to the weight you are carrying on your tires. I would bet they will be less than 120lbs and this will probably change the handling characteristics.
sunflyer
2005 Fleetwood Excursion 39S
350 Cat
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Economical Handyman
S. California
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Get on a scale and get the four corner weights, then adjust the tire pressure.
DeWayne & Judy
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sum1
So-Cal
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Deano7 wrote: Would a steering stabelizer help clear this up? It might mask it to a small degree, but it won't fix it. Get a good alignment and weigh the coach. Use the tire mfr's table to find the minimum pressure for your weights.
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UltraKen
Ohio
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Deano7 wrote:Would there be any kind of safety risk or uneven tire wear to reduce the pressure down to 80?
Thanks for your help.
Deano7
I think what's leading you astray is the pressure marking on the tires. That number is the Maximum Safe Pressure. It is a "do not exceed" figure.
It does NOT mean that you should inflate to that pressure. The correct inflation pressure, as others have pointed out, depends on the weight at each axle.
You really need to get the 4-corners weights. You can do this at many public scales where the platform is located so that you can get just one corner at a time on the scale.
I live in a rural area so I use the scales at a local grain elevator. Just call ahead to make sure they aren't busy with grain deliveries from the farms.
Once you have the four corner weights, go the tire manufacturers website and look up the load/pressure tables for the SPECIFIC tires you have. For each axle use the highest weight-load to determine pressure for both tires on that axle.
Some people prefer to go 5-lbs over the recommended pressure to get better gas mileage and a little less wear. That's OK as long as you don't exceed the pressure maximum on the tire.
UltraKen
Ex -1968 Ultra Van
NOW - 1996 Safari Sahara 35' - Cat 300 - Model 3530
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halfcab
SouthEast
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Sight unseen...I believe the rims on a gasser are rated at 115 MAX PSI.
I think you will find 80 psi to low for the new tires, may I suggest starting around 95 psi.
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wolfe10
Texas
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Go with UltraKen's recommendation. There is no way we can tell you the correct PSI. Your actual weights and the tire manufacturer's PSI/load table are the ONLY correct answer.
And the 120 PSI molded into the sidewall of the tire is the MINIMUM PSI to carry the MAXIMUM LOAD which is also molded into the sidewall.
IF (big IF) the tire is carrying that much weight, then and only then COULD the PSI be correct. And then only if it does not exceed the rim's rating. The rim rating (by law) will be stamped into the wheel-- generally most easily read on a rear dual's outer wheel.
Brett Wolfe
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Deano7
Redmond, WA
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Thanks everyone, all good info to consider. I can't find any pressure info on the manufactures site. These are Double Coin RT500 tires. I think Chinese. 245/70R19.5
I figure I'm probably safe to reduce the pressure down to perhaps 100 lbs until my next trip north (which runs by a truck stop) and I can actually weigh each corner. My old tires were rated to carry around 4,000 lbs and these say 4800 lbs so there's a pretty big difference. The Mfg website says they're a J type (speed symbol).
Again, thanks all!
Deano7
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