225/70/19.5 vs 8/19.5 Tires on a Dodge Chassis

[henryblair]

I need to replace the tires on one of my motor homes.  Has anyone replaced their 8/19.5 tires with 225/70/19.5 tires on a Dodge chassis motor home?  The 225's are readily available for about $100 each as take offs from new trucks.  There is about a 4% decrease in diameter on the 225's, 647 revs per mile vs 621 revs per mile on the 8/19.5.

I know they will fit on the front, but what about the rear?  They are G rated vs the F rating of the 8/19.5's so the ride may suffer.  They also fit the 6" Budd rims.  The section width is 9.5" vs 8".  I have heard that the separation on the rear tires at the widest part of the 'bulge' should be about 1.5".

Has anyone had experience with this?

Henry

[wrolandhyattjr]

Henry:
While I haven't done it, I am preparing to do it.  I have been absorbing information for years on that subject.  Here is how I understand the facts.  First:  You generally can't use them on the rear in a dual configuration.  There is usually insufficient spacing between the tires. Heating and contact are real possibilities.   Second:  That having been said, it is my understanding that there are really no negatives associated with front wheel use and many positives.  The wider surface area for road contact tends to minimize the effects of the narrow 8R19.5 on wandering in handling and stability.  The 225 requires much less air pressure to carry the same load as the 8R19.5 so ride comfort is improved. On the front, the small difference in circumference doesn't affect the speedometer.  Check it out!

Roland Hyatt

[rsflight]

There is a dual separation spec for the 225/70/19.5 tires that is wider than the old 8/19.5 tires.  Usually you can not go to the newer size.  Placing the new on a narrower dual spacing than spec will allow the side wals to contact during use and cause a premature side wall failure due to chaffing.  Your tire dealer should be able to tell you for sure if the size change will work with your current wheels.  Certainly changing wheels can make it work, but it drives the cost up too.  When we replaced our tires a couple of years ago, we stayed with the 8/19.5 tires.

[bluebird]

I have a GM chassis, but I do have 8r19.5 tires. When I went to replace my front tires last year, one tire dealer told me I could go to the 225x19.5s. When I went to order the new tires, he changed his mind. Said the 225s were too wide for the wheel. I went to another dealer and he told me the same thing, but I was very lucky. He had 4 like new 8r19.5s mounted on wheels for $75.00 each. I was thinking it would handle a little better with the wider tires. New shocks made a world of differance on mine. The section width dictates what size wheels you have to run. I didn't want to buy new wheels to go to the wider tire.

[Sasquatch]

I know this is an old thread, but will add my input.  I have a 76 Executive on a M500 chassis and converted to the 225/70/19.5 tires almost 10 years ago.  They work great, handle better, and have a much higher load rating than the 8R19.5's. 

They are a touch shorter, so you will run a bit higher RPM's at the same mph though.