With Big Tires comes Big Responsibility

With a trip to the Idaho back country looming (like this one in 2014, this one in 2013, or this one in 2012), I decided I had better get busy installing larger tires on the RV-4.

The Van’s RV-4 uses 5″ Cleveland wheels and brakes. Typically, a 500-5 tire is installed and that’s what I had.

In recent years, a number of RV flyers have switched to a 380/310 tire. This is basically a 6″ wide tire with somewhat more height but fits on the 5″ wheel. It provides a good bit more contact surface with the ground and this is a beautiful thing when operating off of grass/dirt/gravel.

Probably only of interest to those with RV’s and thinking of making this swap…  The tires are the 380-150-5 Aero Classic from Desser Tires (here).

Before I could get started on the swap, I had to make a run to Truth or Consequences to get some tools out of my hangar there.

The trip down and back was quick and easy. I found that the forest fires near Reserve, NM are pumping a lot of smoke and gunk in the air. None of my photos did a very good job of capturing it but I tried. A couple valleys that I flew thru were very thick with smoke – breathing that stuff is never very appealing.

I’ve been dealing with high oil temperature on the Lycoming O-320 now that we are into the warm summer months. This flight gave me a chance to do some experimenting and observation.

Here is a comparison of the existing/small tires and the new/large tires.

Now with the new/larger tire mounted.

I had the original wheel skirts (pants) that came with the RV-4 kit. These are very small and not very “aero” – they also don’t work with the larger tires. That was just fine by me – it was time to upgrade to the slicker pressure recovery wheel skirts. These skirts are worth about five extra knots of cruise speed versus no wheel skirts. Maybe I’ll get lucky and they are 5 knots faster than the dirty skirts that I had!!!

Swapping the tires is pretty straightforward. It helps to have all the necessary tools, of course. That simple thing has been a challenge for me recently. Maintaining an aircraft “away from home” (meaning, away from all my tools) is tough. It seems that I forget at least one required tool every time. Sometimes there is a hardware store nearby, sometimes not. Turning a 30 minute job into a one week job is always a wee bit frustrating! 🙂

In this case, I seemed to have the tools that were required so things went fairly well.

I haven’t bothered with the new wheel skirts yet. That 5 knots of airspeed is going to be missed but not the end of the world – at least for the short term.

What did I find out about the oil temperature??

Look at the size of that air leak at the bottom-front of the oil cooler! It’s hard to imagine much of any air is going THRU the cooling fins! It’s too easy to simply dump out the gaping hole at the bottom.

Another task…. for another day….