Time for Tires and Brakes
Added 11/7/2006 - Approx. 173 flight hoursUpdated 11/23/2006 - Lining Replacement
Living in the Great North country, our temps have been dropping lately and that means it's time to change the air in the tires from summer air, to winter air. (it's a joke, people!) But seriously, the pressure in the tires drops in the cold weather quite substantially, so you need to fill them back up. Tires should be filled to 42 PSI on the Mains, and 40 PSI on the front, which should be done with no weight on the wheels. Having a pair of homemade jacks handy, I jacked the plane up and went through the trouble of disassembling my wheel fairings to get access to the air stem. Many people have made an issue out of how hard it is to get to the stem, and some people cut holes and put plugs in the fairing to accomodate. I agree totally that it's a real pain, but I don't know that it's a good idea to try to find a convenient workaround....and here's why. You really do need to regularly inspect the tires and brakes. If you always just popped a cover and filled them up with easy stem access, you'd possibly overlook critical issues with brake lines, brake linings, tires, axle nuts, and things like that. So in my opinion, it's maybe better to just bite the bullet and pull the fairing fronts so you can check these things.
In my case, it was a good thing I did. You can see by the tire photos that I have the typical RV uneven tire wear. Some say it's from improper toe-in. Some say it's from the wheels hanging and drooping inwards in flight and touching on the outer edge first on landing. One guy suggested that if you land firmer you'll flatten the gear quicker and wear less on the edges. So I like the last idea first...the problem with my tires is that I land too smoothly. ;) At any rate, these tires can be flipped and installed backwards on the opposite gear leg, and then you can wear the other side of the tire and still get good life out of them. I do have a low spot on each tire, probably from a skidding landing or brake-locking stop, which is very common, so I have ordered replacement tires...more on that later.
Another thing I found while the fairings were off is that I have confirmed that I'm not a very good "feet off" taxi guy. I'm pretty hard on these brakes with the free castering nosewheel and I need to make a better point not to ride the brakes. My brake pads at 170 hours were worn down quite a bit. The pads, Cleveland p/n 66-112, are only available currently as Cleveland parts, so they cost about $15-16 each lining. I have spoken with Rapco though, and they may actually be interested in making these for the experimental market, so with luck we'll have cheaper pads later on. The Brake assembly, by the way, is Cleveland p/n 30-59E, and the wheel assembly is p/n 40-59A.
Now for the tires... I read a cool Aviation Consumer Article on Tire Value that was linked to from Desser Tire's site. This article compared the "value" of various tires. While the article didn't directly apply to our tires, it was good info nonetheless. Our mains are a 15/6.00-6 6-ply tire, which is 15 inches tall. It is NOT the same as a standard 6.00-6 tire, which is almost 2 inches taller. (Our front tire is a 5.00-5 6-ply tire) So this limited my selection a bit on main tires. The article explained that in theory, you're best off either buying the most expensive Goodyear tires, which have more tread and should last a long time, or buying the cheaper retread tires, which have lots of tread, but softer rubber and still last a long time. One other benefit is that the retreads are often more "round" than the factory tires. Many factory tires are slightly oblong, and the retreading process has actually very tight tolerances and often produces a rounder tire. In the case of the tires I bought, I was told that the rubber was also slightly harder than the McCreary AirHawks that I was also considering. Personally I went with the "High Performance Retreads". Saved almost $20/tire over the AirHawks. I also got LeakGuard tubes, and don't forget the free tire talc from Desser.
So, by taking the time to pull my fairings, I was tipped off to impending maintenance that would be required, and I was able to order parts to have on-hand for the proper time. My plan is to change the brakes a.s.a.p., but flip the tires for the winter season...when I may be slipping on ice and then grabbing asphalt. May as well beat these tires a bit more.
Here's some additional info on Cleveland stuff:
Cleveland Brake Info
Cleveland Brake Kits
And some photos...
|
|
|
|
|
Brake Lining Replacement
Updated 11/23/2006 - Lining ReplacementI shot these pictures during the brake lining replacement, for those who've never seen it done before. You need to purchase 4 brake linings, which usually come with rivets (although it might be nice to get a couple of spares on hand). There is one additional item you'll need: A Brake Lining rivet tool. There are 2 types, generally. One requires you to hammer the rivet, and one has a screw handle for squeezing the rivet. I'd highly recommend the screw version, even though it's a couple bucks more. Much less worry about cracking your linings or having the rivets come out poorly.
|
|
|
| Notice above the way the tool is used for driving out the old rivets. You simply use the pin attachment to the tool to drive the rivet out, and it falls through the hole in the bottom of the tool. |
||
|
|
|
| Now, when you want to drive the new rivet, you put an insert in the back of the tool, that fits in the hole by the rivet head. You can cleco the 2nd hole in place using a black cleco. Then just position the tool with the press-out needle attachment removed, and start screwing. Soon you'll have a perfectly formed rivet on the backside of the lining. |
||
In addition to this lining
replacement, I also "rotated" my tires to balance out the wear to the
other edge of the tire. This consisted of removing the air from
the tires, including the schroeder valve,
removing the bolts from the wheel halves. Flip the tube inside
the tire, once again lining up the valve stem with the light spot of
the tire (red dot). Then reassemble. I actually also moved
my right tire to the left and vice versa, which will keep the tire
rotation the same as previous, since some types of tires are touchy
that way. Then just bolt it all up per specs (150 in-lbs) and
fill with air. The brakes are bolted back on with a torque of
75-80 in-lbs. At the same time, I noticed that with the linings
used up, my brake fluid reservior had emptied just to the point of
seeing some air in the line up by the reservoir. With the new
linings, this is not visible anymore, but I used the opportunity to
re-blead the brakes, adding a few more pumps of fluid to the system
(first purging the air from the bleeder line of course), so that next
time it shouldn't quite get that low. All in all, it was a very easy job, and a test flight proved all was well.