Main Landing Gear Tire Clearance

[butchgilbert]

I keep my Condor 6 X 6.00 MLG tires inflated to over 50psi, otherwise the would look half deflated.

After getting new tires last fall, I noticed that the clearance between the tire and the gear crossbar is extremely tight, less than 1/8". The clearance on the previous set was not nearly that close. I also just installed new gear shock discs after 8 years,no change.

Anybody else notice this? Any comments or ideas to correct this would be appreciated.

[PilotDerek]

My two mains are inflated to 30 psi and the nose wheel is 49 psi. I never really noticed the clearance.

[philipneeper]

my 78 C calls for 30 all the way around

[Dave Marten]

Butch,

 

You're over-inflated for a 6 ply tire. Goodyears are spec'd for a max inflation of 42PSI and your F-model Mooney should be at 30 PSI. If you're over-inflated your tires could be 'too-tall' and causing the interference mentioned. Also wouldn't hurt just to double check that your new shoes are indeed 6.00x6.

 

Goodyear specs:

 

http://www.goodyearaviation.com/resources/pdf/db_airdatabook.pdf

 

Michelin Specs:

 

http://www.airmichelin.com/generalcontent.aspx?id=219

 

 

 At the max manufacturer spec'd inflation for the 6 ply (42psi) you should have a tire that is 17.5 (Michelin) or 17.8 (Goodyear) inches across. Not under load (ie, weight off wheels). The condor should fall pretty darn close.

 

Back your pressure off to 30 psi and check your clearance. Verify correct tires. You're right to be concerned with only 1/8 inch of clearance.

 

Just a wild-ass guess, but are they re-treads? If they are the Condor "Monster retread" with the deeper tread then that may well be a taller tire and will also eat away at your clearance. Haven't heard of any Mooney guys running retreads and if that is/isn't an issue. Normally only flight schools run retreads.

[butchgilbert]

Thanks for all the inputs!

I'm sorry but I just can't believe that the correct tire pressure is 30 psi. The tire looks half flat, the rolling friction increases takeoff roll/distance and the tire wear increases.

My tires were replaced with new tires and tubes. They are 6 ply, not 8.

My previous set of tires were inflated to a higher psi and I don't remember the clearance being this close.

Thanks again, I'll keep investigating.

[danb35]

I'm sorry but I just can't believe that the correct tire pressure is 30 psi. The tire looks half flat, the rolling friction increases takeoff roll/distance and the tire wear increases.

Your POH will have the answer--and yes, 30 PSI is correct for the mains on an F model.  Will it hurt to have the tire inflated more?  Probably not, but still doesn't seem like a good idea.

[stevesm20b]

You might want to check your tire pressure with another gauge just to be sure it is reading correctly.

[philipneeper]

over inflated tire,hard landing, i could see some bad juju there.

[Alan Fox]

There is no reason in world to over inflate tires..... They are supposed to be flat on the bottom.......A tire with 60 psi in it will have less than 50% of the tread on the ground than the same tire with 30 psi..... Think of how this affects your braking....even worse how would this affect your braking with a wet runway....Also how much pressure is it putting on the wheel beads.... Answer? twice what it is supposed to....What is printed on the side of the tire is the max load for that tire , not the vehicle it is on....30 psi is what to put in the tire.... 

[jetdriven]

Doesnt the MLG pivot around that crossbar?  It seems like its not a problem. 

 

Now, what do you guys know about Desser retreads on Goodyear FC-III cores?  I am thinking about those on the mains.

[Dave Marten]

Aircraft tires flex over twice as much as automotive tires. They exhibit radial growth due as a function of speed due to centrifugal force, not to mention landing forces (squeezing the balloon). You can bust out the calculator and crunch the numbers using the manufacturer's formulas in the tech data. But, once you look at the numbers you'll see a 0.4 inch radial clearance value applied regardless of speed/size. Both Michelin and Goodyear don't want any part of your gear closer than 0.4 inches radially to their tire.

[Hank]

Ask Ford and Firestone what happens to chronically-overinflated automobile tires. Don't do the same thing to your Mooney, even if your plane will not roll over. The answer is in your POH. My C model is also 30 psi for all tires.

[danb35]

The Ford/Firestone problem resulted from underinflation, not overinflation.  Nonetheless, there's no reason at all for the mains to be inflated that high.

[Alan Fox]

The Ford/Firestone problem resulted from underinflation, not overinflation.  Nonetheless, there's no reason at all for the mains to be inflated that high.

I cant remember exactly , But I think the tire size was wrong , Ford replaced ALL the tires those years on the Explorers...

[SheryLoewen]

Mooney provides a choice of collars for the Shock Link to adjust the tire clearance ( the spinning diameter is more) and there is a chart for that somewhere.