tires again... two sizes, unusual but does it matter?

Personally I want all the tires to be the same size. Tire issues are one of the most frequent problems most RVers have to deal with. If finanically possible, I would also switch to 15 inch rims with "E" rated tires. For me, I would rather have a little over kill margin of safety as opposed to using tires that are at their maximum capacity of weight load.

I wonder what the thinking was? Taller tires on the curb side to counteract the road crown?

You are right, for a vehicle with a differential or transfer case it would be a bad thing, For a trailer it won't have any effect.

Diameter inches (mm)
26.11 (663.1) 26.7 (678.1) 0.59 (15) 2.3%

Width inches (mm)
8.07 (205) 8.46 (215) 0.39 (10) 4.9%

Circum. inches (mm)
82.02 (2083.19) 83.87 (2130.31) 1.86 (47.12) 2.3%

Sidewall Height inches (mm)
6.05 (153.75) 6.35 (161.25) 0.3 (7.5) 4.9%

Revolutions per mile (km)
772.54 (480.03) 755.45 (469.41) -17.09 (-10.62)

The first numbers are for the 205 tires and the second set are the 215 tires the third is the difference.
My opinion would be to have the 205's & 215's on the same axle.

Put the trailer on flat level ground. Measure height to the frame between the axles for each side.

I would put the same size tire on a side and then depending on the height measurement which side to put the taller tires.

As for handling etc I doubt it will make much difference with the tires as close as they are.

johntank wrote:
Diameter inches (mm)
26.11 (663.1) 26.7 (678.1) 0.59 (15) 2.3%

Width inches (mm)
8.07 (205) 8.46 (215) 0.39 (10) 4.9%

Circum. inches (mm)
82.02 (2083.19) 83.87 (2130.31) 1.86 (47.12) 2.3%

Sidewall Height inches (mm)
6.05 (153.75) 6.35 (161.25) 0.3 (7.5) 4.9%

Revolutions per mile (km)
772.54 (480.03) 755.45 (469.41) -17.09 (-10.62)

The first numbers are for the 205 tires and the second set are the 215 tires the third is the difference.
My opinion would be to have the 205's & 215's on the same axle.

wow, thanks for the analytics.

I guess the 205's are going to wear a bit faster due to the increase "travel"... but shouldn't be a big issue. I assume if I switch them to have them on the same axle that the equalizer will handle the difference OK... hopefully. I guess the follow up question would be... is there going to any issue switching a trailer tire from one side to the other cause "belt issues" since some portion of its life was running predominantly in one direction and now "asking" it to go the other way?

RCMAN46 wrote:
Put the trailer on flat level ground. Measure height to the frame between the axles for each side.

I would put the same size tire on a side and then depending on the height measurement which side to put the taller tires.

As for handling etc I doubt it will make much difference with the tires as close as they are.

Right now the "curb side" have 205's while the road side have 215's which may contribute a bit more "effect" to "road crown" than normal (meaning a bit more tilt). I can't say I notice anything while driving. Maybe it helps with the "step up" entering the trailer (cause its a bit lower but I don't think the difference is that great.

I will have to do a measure next pull from the driveway as it isn't very level (cross-wise).

Biggest issue I've found with a different diameter tires on a trailer axle is uneven braking mostly on that axle especially on wet pavement.

Another issue with different diameter tires on a tandem axle trailer ...... the rear axle tends to lift weight from the front axle through the equalizer bar on hard braking events. I would run the larger diameter tires on the front axle.

We are talking .7" difference in diameter here which isn't much. Axle makers do recommend same diameter tire on a axle.

Interesting about the weight shift during braking. Hopefully we are talking about the trailer suspension equalizer and not a hitch equalizer. Not sure I understand how the brake event cause the weight "lift" in the equalizer of the suspension. My thinking was that it would reduce / slightly lift the rear axle.

I am also wondering if there would be any affect on tongue weights with the larger tires moved to the forward axle.

higher percentage of tongue weight mitigates trailer sway .
this assumes your tow vehicle is a 2500 or f250 plus .
I moved my boat trailer axle to the rear about a foot a decade ago .
the additional tongue weight on the trailer hitch makes the boat trailer handle like a dream .
this option is limited for the f150 and 1500 tow vehicles .
having the 215 tires on the drivers side means that the crown in the road also plays into a small tilt downward to the passenger side .
until you upgrade to the 2271# capacity kumho 857 in size 205R14 load range D tire at your next tire replacement ..
Your best handling option with the tires you own is to mount both 215 tires on the rear axle and the 205 tires on the front axle .
if you mount the larger 215 tires on the front axle there may be a slightly lower tongue weight percentage .
smaller tongue weight percentage increases trailer sway .
higher weight behind the trailer axles is uncontrolled weight and acts using the lever principle to make our trailers sway .
higher weight between the trailer axle and the hitch is controlled weight and adds to safety .

budwich wrote:
Interesting about the weight shift during braking. Hopefully we are talking about the trailer suspension equalizer and not a hitch equalizer. Not sure I understand how the brake event cause the weight "lift" in the equalizer of the suspension. My thinking was that it would reduce / slightly lift the rear axle.

I am also wondering if there would be any affect on tongue weights with the larger tires moved to the forward axle.

The .7" taller tire actually will be 3/8" difference at the suspension level and have little to non effect on axle weights.

Most flat spotting is normally on the trailers front axle from hard braking events with good brakes on the trailer. Some folks set their brake controller with lots of gain which applies brake power with a slam on the suspension.