Bigger Tires?

[ajriding]

I am at the point I need almost all new tires, 6 of them.
I have 225/75/16 (I think I remembered the #s correct, these are the standard class-c tires) Would going to the next bigger size (larger diameter) help with fuel economy?
I have been told it would since the engine running rpm would be lower, but do not have positive proof. If anyone has done this then that would be the person to respond.

[ajriding]

I tried smaller, standard and bigger tires on my truck, though it is diesel. Better all around with bigger tires.
RV sold, gone, so thanks

[wa8yxm]

Fuel economy. Likely not so much as you might notice.
Speeding tickets. Unless you re-calibrate the speedo yes you will get more of 'em.

Tire TREAD life will be extended a bit.Brakes may not last as long.

SO unless you have a tire popping issue or other issue that larger tires would address.. I'd not do it.

[ajriding]

thanks. late update. over 3 years ago foreigner hit me, totaled the vehicle and insurance gave me way more than I could have sold it for.
no more motor homes, just trailers or things with no transmission, engine or insurance payments…

[ajriding]

I can't explain how the mile clicker was right and the speedo was off. It must have always been off. sold the truck, so not an issue.

[WILDEBILL308]

ajriding wrote:

buta4 wrote:
Wouldn't recalibration of the speedometer/odometer be necessary in some of these cases? Just a thought.

Few would care. I have gone bigger on my truck, and just deal with it and know what the real speed is. The numbers are rarely more than 1.5-2 off. My trucks speedometer is off but somehow the mile counter is spot on.
You can change the gear in the speedometer to match.

Please explain how on can be right and the other off when they come from the same sensor?
Bill

[pianotuna]

Yes recalibration could be done--but on my E-450 that option is greyed out.

[ajriding]

buta4 wrote:
Wouldn't recalibration of the speedometer/odometer be necessary in some of these cases? Just a thought.

Few would care. I have gone bigger on my truck, and just deal with it and know what the real speed is. The numbers are rarely more than 1.5-2 off. My trucks speedometer is off but somehow the mile counter is spot on.
You can change the gear in the speedometer to match.

[buta4]

Wouldn't recalibration of the speedometer/odometer be necessary in some of these cases? Just a thought.

[ajriding]

So, at what larger diameter size does the benefit of increased mpg fall off?

[ol_Bombero-JC]

ajriding wrote:
Thanks, Pianotuna, good reply. It brings up a thought. Why not just change the gearing in the rear dif?
Larger tires are less efficient, but the drop in rpm overcomes this, but keeping small tires and changing the gearing will drop the rpm and keep the tires small…
I actually want larger tires to "look" better also, so may stick with tire changes. Ground clearance is a plus.
I have had oversize tires on my truck before and the mileage dropped off considerably, but that engine was having to work.
Interesting about the 215/85-16. I have heard that more narrow tires are more efficient than wide tires, so even a large diameter tire that is narrow will be better than a wide tire of smaller diameter. Any experience anyone?

"Just change the gearing in the rear dif?"

One word reply = Expensive!

Two word reply = VERY expensive!

Of course that's in the,,,, wallet of the beholder!
You will need a new ring & pinion (maybe the carrier also), along with labor costs to set up the diff and do the swap.
Depending on the type - change-out may require removing the entire axle housing assembly.

And - the 'set-up' guy needs to 'know his stuff'!!
Even then - minor errors can/will/may produce premature wear, howling, etc. - resulting in additional expense to get it right.

"If it ain't broke, don't fix it" - is sage advice.

Suggestion.
Post your question on the appropriate forum for the RV you have - brand name, model, etc.
Forget "General RVing Issues" - go specific!

IMO - you are "splitting hairs" on the pro and con for the tire size change.......however - things like clearance are important factors to check out before making what may (or may not) be a simple and easy modification...:W

`

[ajriding]

Thanks, Pianotuna, good reply. It brings up a thought. Why not just change the gearing in the rear dif?
Larger tires are less efficient, but the drop in rpm overcomes this, but keeping small tires and changing the gearing will drop the rpm and keep the tires small…
I actually want larger tires to "look" better also, so may stick with tire changes. Ground clearance is a plus.
I have had oversize tires on my truck before and the mileage dropped off considerably, but that engine was having to work.
Interesting about the 215/85-16. I have heard that more narrow tires are more efficient than wide tires, so even a large diameter tire that is narrow will be better than a wide tire of smaller diameter. Any experience anyone?

[pnichols]

That Michelin document address above is for an old version - 2007.

This is the 2015 version, that for instance, includes data on their MS2 tires:

https://www.michelinb2b.com/wps/b2bcontent/PDF/Truck_Tire_Data_Book.pdf

[WILDEBILL308]

Andy, Look at this they have a chart showing with and diameter.
http://www.michelintruck.com/assets/pdf/Truck_Tire_Data_Book_Jan2007.pdf
I don't see that much difference between 225/75/16 and up to 265/75/16 The 265s are about 1 inch wider and 2.5 inches taller. The benefit of the bigger tire is the load capacity goes up to 3415lbs at 80 psi.
Bill

[tenbear]

My class C came with Load Range D tires and the recommended inflation was right at the upper limit for these tires. When I replaced my tires I went to LR E tires and increased the inflation by 5 psi. I don't really know if it improved my gas mileage or not, but I feel better with the LR E tires.