[Jetj01]

Well, while I loved the utility of the 380X150X 5.00 tires on my RV-4, today I switched back to the 5.00 X 5. I had 81 hours on my big tires since first flight last May 09 and was very plesed with the soft/rough field performance and easier taxiing in general. However, over the last few hours I noticed a gradually greater and greater amount of wheel shimmy, so much so that aprox 10 hours ago, a wheel pant developed a crack that I had to repair. While repairing the crack I balanced the wheel/tire combo and noticed that the tire was no longer round, ie, it had developed lumps and bumps. This is probably do to braking or spin up or what ever, but they are not true or round any more. I'm sure the greater diameter/mass on the small wheel may have influenced this.

So today I R&R'd the tires with some new tubes and Goodyear III's stock size and did a fast taxi and problem solved. Using the same wheelpants.

Again, while they were round I liked the bigger tire and didn't see any real speed performace loss, but not too happy about having to change out with lots of tire tread/wear remaining...for what it's worth

Tailwinds,

 

[rocketbob]

What brand are the big tires? What kind of pressures were you running?

If I had to make an educated guess, your wheel alignment is off which is causing the tires to flex and wear unevenly. If you have a bit of toe-in or toe-out I can see how the tires would wear unevenly since a large tire on a small rim would flex a bit more in comparison to a vanilla 600x6 tire/rim setup. A more rigid tire would slide across the pavement and wear evenly on the outside or inside of the tire. The 380 tires with more sidewall area would flex more, so the wear pattern perhaps would be a bit more unpredictable.

 

[nucleus]

That's Funny

Yesterday, while investigating a main gear shimmy I have had recently, I found that my little tires are flat spotted and out of round. I'm sure the smaller diameter/mass on the small wheel may have influenced this. So I am taking my out of round little tires off and switching to big ones.

Hans

 

[Jetj01]

Rog!

Hans, now THAT is funny! Good luck!

Bob, the wear pattern is even thoughout both tires, I don't have any obvious 'scrubs' or bald spots. They look like they shoud still be good, only noticable when spinning them on the balancer. The lumps and bumps seem to be coming from the sides/underneath the tread, worse on the left side. I think what you mentioned is true. The side loads are more prevalent since the mass/thickness/ width is greater. BTW, they were Aero tires.

Tailwinds,

 

[rocketbob]

Too bad you really can't change the wheel alignment easily on an RV. A friend of mine gets almost 500 hours on a set of tires on his rocket.

Just to give you an idea on how misalignment affects wear with some basic trig: for every mile traveled with one degree of toe in, that tire will travel 92.2 feet sideways.