QuestionQUESTION: Fleetwood 1993 Pace Arrow P-30 chassis with 8R19.5 tires and wish to convert to
225/70R19.5 ... a little shorter and a little wider. The local tire dealer here in Wellington, NV says its generally not a problem but is not sure for my motorhome; a wider minimum dual spacing is required and not sure of the fit.? Thanks, Terry
ANSWER: Terry,
An 8R19.5 is 8.0" wide, 33.8" in diameter, fits on a 5.25 to 6.75" rim, with a minimum dual spacing of 9.1" with a load carrying capacity of 3525# at 110 psi (single, Load Range F)
A 225/70R19.5 is 8.9" wide, 31.9" in diameter, fits on a 6.00 to 6.75" rim, with a minimum dual spacing of 10.0" with a load carrying capacity of 3640# at 95 psi (single, Load Range F)
So I see 3 problems:
1) The width of the rim. If you have 5.25" rims, you can not do this swap.
2) You need about 1/2" more clearance widthwise. Unfortunately, no one has cataloged these vehicles to assess how much clearance there is, so someone will have to look at your vehicle - and even then it is difficult to be sure because the worst case is fully turned, fully compressed.
3) You need a minimum dual spacing of 10" - and that also is something that isn't cataloged. Someone will have to look at the vehicle to measure it.
and just so it is clear, you need to use at least the same Load Range, but you can use 15 psi less pressure.
Bottomline: Someone needs to look at your vehicle to assess the 3 issues I've outlined. And then the Load Range and usage pressure needs to be checked.
---------- FOLLOW-UP ----------
QUESTION: Thank you very much for your great service and answer. Everything is ok except I'll need to measure and I'm comfortable with doing that, can you guide me as to where to
make the measurement? Thank you, Terry
AnswerTerry,
There were 3 measurements:
1) Rim width - ought to be stamped on the rim on the inside, so you need to take the tire and rim assembly off the vehicle. I would not recommend anyone do this unless they have the proper tools, such as a torque wrench.
2) Clearance around the steer and drive tires. That's a little harder. For the drive tires, it is pretty easy. Measure the distance between the side of the tire and the body work - keeping in mind that the drive axle moves up and down.
The steer positions are a lot more difficult and more complex because there are a number of different suspensions systems and each has a different way the suspension travels up and down. I'd recommend a professional look at this.
3) Dual spacing - is the distance from the centerline of one tire to the centerline of its mate.
http://www.michelintransport.com.my/var/michelin_site/storage/images/home/new-re
It's dimension E
