SonexBuilders.net

The wheel rims on the Azuza wheels are two pieze bbolted with 3 bolts. Does anyone have any idea of the torque on these? They are not AN bolts?

Just had a look at a wheel and the bolts were SAE grade 5. Torques for a 5/16 bolt range between 9 and 22 ft lbs depending on surface coating. I'd be inclined to use the lower range, no more than 14 ft lb, because I think it would be possible to crush the wheel. I have never actually torqued the bolts. Just did them up tightish and guess what? It's always been OK.

Peter Anson
Sonex 894
212 hours

Tighten those bolts up pretty darn tight. Your going to be inflating those tires about 20 higher than the max pressure stamped on the side of the wheel. About 45-50 psi.
The only folks I've ever heard about breaking wheels were those using lower than normal tire pressure and minimal torque on the bolts.
As a side note, if your tires get below about 35lbs you run the real risk of moving the tire bead on the wheel during hard braking and then you get an almost instant flat when it rips the stem off the tube.
Tighten them up tight and run good solid tire pressure.

Larry

Cautionary note to anyone running the larger 5.00 x 5 tires. Do not inflate to 50 psi, way too much for the wheel with those tires. I find 25 psi works well with the larger tires.

David A

Also, and this is mentioned many times elsewhere in the website, it's best to get the AN equivalent bolts for the wheels. I have seen an Asuza wheel taken down for maintenance and one of the stock bolts was broken.

It's cheap insurance....

Tighten those bolts up pretty darn tight. Your going to be inflating those tires about 20 higher than the max pressure stamped on the side of the wheel. About 45-50 psi.
The only folks I've ever heard about breaking wheels were those using lower than normal tire pressure and minimal torque on the bolts.
As a side note, if your tires get below about 35lbs you run the real risk of moving the tire bead on the wheel during hard braking and then you get an almost instant flat when it rips the stem off the tube.
Tighten them up tight and run good solid tire pressure.

This is interesting Larry. I have never run my tires higher than the recommended pressure, and usually at only 30 psi. Have now done over 370 landings on both sealed and unsealed runways and never had any tire problems. My first set of tires are getting worn and will have to be replaced in a few months. I had a bit of a panic when I heard of another builder having punctures due to breaking cords in the tires from running low pressures so I ordered spare tires and tubes and pulled my wheels apart to inspect them. Everything was in perfect condition. I still have the spares.
Peter

I have had sevearal flats due to low tire pressure. One time the valve stem tore partially off but the others were from slices in the tube where the rim pinched the tube, probably from my less than stellar landings. I try to keep an absolute minimum of 35psi, but optimally 45psi.

Mike Singleton

What is the reason for higher air pressure of 45 lbs? Is it to keep the tire from spinning on the rim? If that is the case could some type of tire dressing or sealant be used on the rim edge to help prevent this. I have noticed my valve stem getting pinched before due to low air pressure I think.

Great idea Kip. Do you have part numbers? I have the Sonex brakes. I wonder what grade hardware they are? They seem better than the Azuza bolts.

My right brake was grabbing after my last flight, and I found that one of the 3 bolts that go though the wheel and hold the Aerobrake rotor had broken flush with the wheel.  I guess the nut is somewhere on the runway.

On contacted Sonex tech support to get a replacement, and maybe replace all the bolts.

I noticed that the pucks are worn at an angle, indicating that the rotor is flexing during braking. I'm guessing this flexing may have contributed to the bolt fatigue.

The rotor side of the bolt was really chewing up the pucks. I'm lucky it didn't lock up.

I don't think that this is something that can be inspected to prevent failure, but I'll see what Kerry says.