larger Tire size

[Chuck Carroll]

We started parking our 2017 32 foot Class C Forrester in our driveway that has a slope. I put dolly wheels on the back to prevent the drag bars hitting our cement driveway. An inch or so may make a difference in making it smoother. I'm due for new tires (5 year old tires) and was thinking of changing to 235 85 16s over the old 225 75 16s. It looks like this gives an inch or so in height. Are there any drawbacks on doing this? I understand the speedometer will be affected some, will gas mileage really be affected too?

[IsleDog]

if you have the clearances for it the only drawbacks are boing to be your speedometer will be off by about 5 mph and you *MAY* notice it does not have as much "power or torque". below is how to calculate that.

https://www.acadiaforum.net/threads/...s%20per%20mile.

Divide the figure for the current tire by the figure for the tire you’re recommending. Example: If the current tire measures 842 revs per mile and the recommended tire measures 800 revs per mile, the formula is 842/800 = 1.0525.

Multiply the result by a speedometer reading in miles per hour. Use 60 mph as a baseline number. Example: 1.0525 X 60 = 63.15. So a 42 revs per mile change means that when the driver’s speedometer reads 60 mph, his true speed is 63.15 mph.

Remember that the difference grows exponentially as speed increases. If you calculate against 80 mph, for example, the difference is 4.2 mph. At 100 mph, the difference is 5.25 mph."

[kenandterry]

Have you actually measured PRECISELY the outside measurements to see if you’ll actually obtain the clearance your hoping for?

If it doesn’t give you the clearance you’re looking for, you may have made changes to performance, torque and actual speed for nothing.

[Duckogram]

There are two more issues that do not appear to be considered. First is your rim width. OEM are 6”. A 235 should fit ok but it is marginal. The second is the clearance between the duallys. You might want to look at the sectional width as measured with a full load (the bulge at the bottom). Pretty sure you would not want the inner and outer touching. Just a though. There are a couple of folks on here that are well versed on the subject (not me) so maybe one of them can add some expertise.

[n1acguy]

I've considered larger tires, as the ride from the smaller wheel/tire combo leaves a bit to be desired, but choices are slim. If you do change, realize that you've got to change the spare too, or it won't be usable at all on the rear. Then you have to realize it could make getting a replacement tire on the road a challenge. The originals are a very popular size of load range E tire.

That said, if the tire is an inch larger in circumference, the rear axle is only 1/2" higher, making a very minimal difference as far back as the drag bars.
You would notice it needing to gear down quicker on even small grades, but unless you only drive in the flatlands your gas mileage isn't going to be any better even though the engine will turn slower for a given speed. If it needs to say hold 5th in the same situation where it could have done it in 6th, that advantage goes away. These things just eat gas.

I would do other things to add clearance, like maxing out the air bags just before backing into your driveway, and adding air shocks to give more clearance. Those options would require you to change air pressure before you park it since you don't need or want it the rest of the time, but they're easy. There may be other easy ways to get a bit more lift, but I don't think tires will get you where you want to be

[kenandterry]

The results are in.......
and if you want significant clearance, get in touch with this guy.
He says he hasn’t scraped bottom in a very long time.

[Sergiop]

https://www.1010tires.com/Tools/Tire...ismetric=False

Your larger tire choice increases the radius 1.2 inches. Will that be enough to clear the driveway?

If you have air bags I would try inflating them, even over inflating them for 5 minutes to see if you get the clearance needed.

[n1acguy]

Originally Posted by kenandterry

The results are in.......
and if you want significant clearance, get in touch with this guy.
He says he hasn’t scraped bottom in a very long time.

The ultimate Pathfinder conversion!

[n1acguy]

Originally Posted by Sergiop

https://www.1010tires.com/Tools/Tire...ismetric=False

Your larger tire choice increases the radius 1.2 inches. Will that be enough to clear the driveway?

If you have air bags I would try inflating them, even over inflating them for 5 minutes to see if you get the clearance needed.

Now that's interesting. I was thinking these all had 235s, and I just realized mine are 225s too. My biggest reason to change would be to get a G rated tire, but I wouldn't want to change the ratio at all. We've got some big rocks to pull up over out here.

[Hoglou]

Take a moment and look at the c series truck tire. Improves the capacity a bit over e series.

[n1acguy]

Originally Posted by Hoglou

Take a moment and look at the c series truck tire. Improves the capacity a bit over e series.

Can't find anything on that. Who makes them?
The way things are rated now, the heaviest tire I can find in 225/75R16 are the 121 rated tires that came on the MH.
I see Goodyear makes a Grated tire in the 235/75R16 size, but mostly they're using a numerical rating system now. I don't see many using the old letter designations anymore.

[wmtire]

Originally Posted by n1acguy

I see Goodyear makes a Grated tire in the 235/75R16 size,

Can you please point me to that?

[Hoglou]

Take look at post 12 on "Taking MH out of mothballs" on page one on sunseeker. I put these tires on my coach as I don't rotate them during their 7yrs ,,

[elind]

Is your problem only at your home driveway? Did you think about laying down some 2 x 8s in the drive way to give some lift? Driving up on the boards could help.

[n1acguy]

Originally Posted by wmtire

Can you please point me to that?

Excuse me, even that is in the 85 profile https://www.americastire.com/buy-tir...80496730809888

[n1acguy]

Originally Posted by Hoglou

Take look at post 12 on "Taking MH out of mothballs" on page one on sunseeker. I put these tires on my coach as I don't rotate them during their 7yrs ,,

Those are just 121 rated tires. Same rating as on the Hankooks that came on my MH.

[fobagbob]

Originally Posted by n1acguy

Those are just 121 rated tires. Same rating as on the Hankooks that came on my MH.

What size are those, I can't find a Hankook 121 rated 225/75R16.

[n1acguy]

Originally Posted by fobagbob

What size are those, I can't find a Hankook 121 rated 225/75R16.

I tried to find a pic. Maybe mine are 115, but it's confusing because there are a fair number of 121 rated tires that don't use the C designation. I must have looked at 100 tires yesterday.

Here's one described as load range F, but still 121. A G rating would be 126.
https://www.prioritytire.com/federal...l-season-tire/

[nic7320]

You might also consider a lift kit. 4x4 conversion shops do that, but tell them all you want is a short lift, not the rock hopper big lift for off-road use..

[ARhappycamper]

tiresize.com has several calculators.