Community Forums

Mike & Nancy · 01-22-2017, 09:34 PM

Need info from anyone that has upgraded their tires from 235/80/22.5 to 255/80/22.5 on a 2006 Ford F53 Chassis. My son is puchasing a 2006 Dolphin 5342 MH that will need new tires. He would like to go to larger size...any concerns or problems with doing this?

LJowdy · 01-23-2017, 05:45 AM

There are a lot of threads on this forum regarding up-sizing tires. To answer the question technically by going to the larger diameter tires 2 things will happen. The first is it will lose low end power due to the larger tire and second it will have speedometer error.

Those 2 things are for sure. Other area's to look at are tire clearance on the intended vehicle. Often times the manufacturer spec's tires that will clear fender wells so once you're compared the sizes using this handy calculator (see link below) then make up your own mind
https://tiresize.com/calculator/

legryz · 01-23-2017, 02:28 PM

Here's the difference in the two tires, not that much of a difference.

Click image for larger version

Name: ImageUploadedByiRV2 - RV Forum1485206903.439395.jpg
Views: 112
Size: 112.1 KB
ID: 149875

legryz · 01-23-2017, 02:30 PM

Click image for larger version

Name: ImageUploadedByiRV2 - RV Forum1485207001.874871.jpg
Views: 95
Size: 131.2 KB
ID: 149876

And the speedometer error.

tmw188 · 01-23-2017, 06:47 PM

Quote:

Originally Posted by legryz

Here's the difference in the two tires, not that much of a difference. Attachment 149875

Looks like a lot of difference.

iPad using iRV2 - RV Forum

legryz · 01-23-2017, 07:32 PM

Quote:

Originally Posted by tmw188

Looks like a lot of difference.

iPad using iRV2 - RV Forum

1.3" on Dia. so a little more then 5/8" on height.

.7" (3/4") on width

.6" higher sidewall (divided by 2 = .3" (3/8"))

Not much difference.

Now the circum. is more but only by 4" which = more tire RPM's which changes the speedometer but only by 3 MPH at 90. Not a big difference.

hydro45640 · 01-24-2017, 04:18 AM

I went to a 255-70-22.5, very little difference in overall specs. Only 6 revolutions per mile. The biggest difference was the price, Much, much cheaper.

tmw188 · 01-24-2017, 04:42 AM

Quote:

Originally Posted by legryz

1.3" on Dia. so a little more then 5/8" on height.

.7" (3/4") on width

.6" higher sidewall (divided by 2 = .3" (3/8"))

Not much difference.

Now the circum. is more but only by 4" which = more tire RPM's which changes the speedometer but only by 3 MPH at 90. Not a big difference.

To me that is a lot. Not that it is bad but it's a lot to me.

iPad using iRV2 - RV Forum

jerichorick · 01-24-2017, 04:49 AM

Quote:

Originally Posted by Mike & Nancy

Need info from anyone that has upgraded their tires from 235/80/22.5 to 255/80/22.5 on a 2006 Ford F53 Chassis. My son is puchasing a 2006 Dolphin 5342 MH that will need new tires. He would like to go to larger size...any concerns or problems with doing this?

Mike, changing tire size on a car or pu truck is like changing socks. You do it for reasons that can't be applied to a big motorhome (relative to size and purpose.) The brands Goodrich and Toyo have good reputations. This is the first consideration. Sticking with a diameter that is close to the original is the next consideration, and load rating follows that. IMO load rating is the most critical spec because it is directly related to your safety.

Because there are so many threads on this forum on this topic be careful not to be misinformed by the sometimes conflicting opinions.

Some manufactures publish very useful specs. Others not so much. Do your homework and then buy with confidence.

Happy trails.
Rick Y

Brockx · 01-24-2017, 04:52 AM

Difference is insignificant. Your speedo is probably incorrect now . I have that tire on my F53, however it is the 30,000 gcwr chassis

GREGORYJ · 01-24-2017, 07:48 AM

I'd be concerned of the 7.5% greater width. With the duel tires at the back and when sitting or driving they bulge out a bit on the ground, touching or rubbing each other could cause problems. Also, if a safety inspection was required on the RV in the future, it may not pass with incorrect tire size. If 235/80x22.5 size is not your preferred choice, I'd go with 245/75x22.5 as they are very close in spec's.

Scooter · 01-24-2017, 08:00 AM

x2 from Ellen & Greg. You don't want the rear tire sidewalls touching.

tmw188 · 01-24-2017, 11:10 AM

Quote:

Originally Posted by GREGORYJ

I'd be concerned of the 7.5% greater width. With the duel tires at the back and when sitting or driving they bulge out a bit on the ground, touching or rubbing each other could cause problems. Also, if a safety inspection was required on the RV in the future, it may not pass with incorrect tire size. If 235/80x22.5 size is not your preferred choice, I'd go with 245/75x22.5 as they are very close in spec's.

That's true with tire bulge there is maybe only 2" as it is.

iPad using iRV2 - RV Forum

Mike & Nancy · 01-26-2017, 09:56 PM

Thanks everyone for your input. We will be picking up the 2006 Dolphin tomorrow if everything checks out. Tires will be replaced next week using the FMCA purchase program and we will be sticking with the 235's.