M20J Main Gear Tire and Tube Recommendations

[KB4]

On 1/19/2022 at 12:50 AM, carusoam said:

Paul MAY know that already….  
 

Can you seen his signature line?  
 

Best regards,

-a-

So then what is the no where near the labor then, the point he made to a new owner?  His point @201er was that the plane is already up in the air and nose wheel is coming off at annual anyway SO changing a tire and tube then IS easy and not much extra work at all then.  And I agree. 

[Bolter]

I prefer the Good year FC3's due to their stiff sidewall.  Compare side by side at your next shop visit (assuming they have a varied collection of used tires not yet disposed of).  The Goodyears are stiffer, and I "feel" this will be an advantage in a failure.  A little less sag when the tire blows, is a good thing with a limited ground clearance prop and gear doors.  I have not tested having a blow out, so I cannot confirm this is true.  Just my thoughts on how I justify the expensive tires.

[jaylw314]

38 minutes ago, Bolter said:

I prefer the Good year FC3's due to their stiff sidewall.  Compare side by side at your next shop visit (assuming they have a varied collection of used tires not yet disposed of).  The Goodyears are stiffer, and I "feel" this will be an advantage in a failure.  A little less sag when the tire blows, is a good thing with a limited ground clearance prop and gear doors.  I have not tested having a blow out, so I cannot confirm this is true.  Just my thoughts on how I justify the expensive tires.

I gotta imagine tire stiffness will help little in the case of a blowout since the plane is held up by the tube, not the tire.  The main gear holds significantly more weight than a passenger car tire (~1500 lbs vs ~800 lbs in my car) and is far smaller.  With stiff walled, low-profile radials, the car tire did (barely) protect my wheel in a blowout, but I can't imagine a stiffer tire will help in the main gear (maybe the nose gear).

I'm guessing "run-flat" tubes are not a thing in aviation, right?  

[N201MKTurbo]

1 hour ago, Bolter said:

I prefer the Good year FC3's due to their stiff sidewall.  Compare side by side at your next shop visit (assuming they have a varied collection of used tires not yet disposed of).  The Goodyears are stiffer, and I "feel" this will be an advantage in a failure.  A little less sag when the tire blows, is a good thing with a limited ground clearance prop and gear doors.  I have not tested having a blow out, so I cannot confirm this is true.  Just my thoughts on how I justify the expensive tires.

I have Monster retreads on FC3 cores (after grinding 1/4 inch of tread). I can tell you from experience that you cannot taxi on a flat tire.
 

You can land OK, but as you slow to taxi speed, the plane will stop and no amount of power will get it moving.

[201er]

14 minutes ago, N201MKTurbo said:

I have Monster retreads on FC3 cores (after grinding 1/4 inch of tread). I can tell you from experience that you cannot taxi on a flat tire.
 

You can land OK, but as you slow to taxi speed, the plane will stop and no amount of power will get it moving.

That’s cause the inner gear doors dig into the ground when it’s fully flat.

[N201MKTurbo]

1 hour ago, 201er said:

That’s cause the inner gear doors dig into the ground when it’s fully flat.

Mine didn't they were about 1/2 inch above the pavement. Nothing got damaged.

[201er]

14 minutes ago, N201MKTurbo said:

Mine didn't they were about 1/2 inch above the pavement. Nothing got damaged.

Maybe there was still some air in the tube? When I've come out to find the plane sitting on a flat, the corner of the gear door would be on the ground

[N201MKTurbo]

55 minutes ago, 201er said:

Maybe there was still some air in the tube? When I've come out to find the plane sitting on a flat, the corner of the gear door would be on the ground

Maybe there is something to the stiff sidewall tires?

[cliffy]

6 hours ago, jaylw314 said:

I gotta imagine tire stiffness will help little in the case of a blowout since the plane is held up by the tube, not the tire.  The main gear holds significantly more weight than a passenger car tire (~1500 lbs vs ~800 lbs in my car) and is far smaller.  With stiff walled, low-profile radials, the car tire did (barely) protect my wheel in a blowout, but I can't imagine a stiffer tire will help in the main gear (maybe the nose gear).

I'm guessing "run-flat" tubes are not a thing in aviation, right?  

Maybe you had better check your W&B I don't think any Mooney has 1500 lbs on the nose wheel   Could be wrong but I don't think so.

[carusoam]

5 hours ago, cliffy said:

Maybe you had better check your W&B I don't think any Mooney has 1500 lbs on the nose wheel   Could be wrong but I don't think so.

There is one known time when all 2k+#s are on the nose wheel….

1, 2, 3…. The third porpoise is when the nose wheel flattens and the prop strikes the ground….

• One bounce is fine… continue to work your pilot skills…
• Two bounces… it’s time to get going…
• Three bounces… the pilot is thinking his skills are much better than they really are…. 

It’s a momentary thing and probably doesn’t show up in a WnB calc…

WnB is all about statics…

Pile driving a nose wheel is more dynamics…

PP attempt At humor only…

-a-

[carusoam]

13 hours ago, KB4 said:

So then what is the no where near the labor then, the point he made to a new owner?  His point @201er was that the plane is already up in the air and nose wheel is coming off at annual anyway SO changing a tire and tube then IS easy and not much extra work at all then.  And I agree. 

KB,

I was asking if you have seen his signature line…  

People using a cell phone screen to view MS often can’t easily see the details…

It lists his skill sets…

He has a bunch of the important ones…

Not listed is what he does for a day job…

 

So…. He may have given a different answer than you would expect….

I would probe a bit deeper to find out what he meant and why he wrote what he did…

 

He likes helping out all types of pilots… including newbie Mooney pilots…

It was probably a matter of scale… and didn’t come out very well in the brief post…

We can all be better writers… 

 

Main objective of MS… keep everyone involved in the conversation… keep everyone wanting to come back…

It helps to have a modicum of forgiveness… not everybody gets it right, all of the time…

Best regards,

-a-

[jaylw314]

16 hours ago, cliffy said:

Maybe you had better check your W&B I don't think any Mooney has 1500 lbs on the nose wheel   Could be wrong but I don't think so.

I said "The main gear holds significantly more weight than a passenger car tire"

[Hank]

23 hours ago, jaylw314 said:

I gotta imagine tire stiffness will help little in the case of a blowout since the plane is held up by the tube, not the tire.  The main gear holds significantly more weight than a passenger car tire (~1500 lbs vs ~800 lbs in my car) and is far smaller.  With stiff walled, low-profile radials, the car tire did (barely) protect my wheel in a blowout, but I can't imagine a stiffer tire will help in the main gear (maybe the nose gear).

I'm guessing "run-flat" tubes are not a thing in aviation, right?  

My C weighs a lot less than my car!

• Mooney gross = 2575 lb ÷ 3 tires = 858 lb per tire average
• Nissan Altima gross = 3462 lb ÷ 4 tires = 865 lb per tire average
• Honda Ridgeline gross = 6019 lb ÷ 4 tires = 1504 lb per tire average

That's it for my garage. A Silverado or F-150 with a full bed will be much higher, and yes, I know no tire carries the average weight. I have a car whose weight is 63% on the front, so 4250 curb weight x 0.63 = 2677 lb ÷ 2 tires = 1339 lb per front tire before I get in, add luggage, shopping bags, etc.

Where did you get "~1500 lbs" for your Mooney main gear tires? Many J's are 2740 lb, some are 2900 lb., but anytime the nose wheel is in the air, the wings are carrying a significant portion of the aircraft weight so you won't be at 1500 per main tire unless you really thump a landing. I think that's what most people can't figure out.

[jaylw314]

2 hours ago, Hank said:

My C weighs a lot less than my car!

• Mooney gross = 2575 lb ÷ 3 tires = 858 lb per tire average
• Nissan Altima gross = 3462 lb ÷ 4 tires = 865 lb per tire average
• Honda Ridgeline gross = 6019 lb ÷ 4 tires = 1504 lb per tire average

That's it for my garage. A Silverado or F-150 with a full bed will be much higher, and yes, I know no tire carries the average weight. I have a car whose weight is 63% on the front, so 4250 curb weight x 0.63 = 2677 lb ÷ 2 tires = 1339 lb per front tire before I get in, add luggage, shopping bags, etc.

Where did you get "~1500 lbs" for your Mooney main gear tires? Many J's are 2740 lb, some are 2900 lb., but anytime the nose wheel is in the air, the wings are carrying a significant portion of the aircraft weight so you won't be at 1500 per main tire unless you really thump a landing. I think that's what most people can't figure out.

Just the assumption that the main gear takes the bulk of the weight, so that's only 2 tires, not 3.  And that's 2 tires the size of lawn mower tires, my Subaru has 17" rims and 225mm width, so that's probably 8 times the contact patch area or something?

My car weighs about 3200 lbs, and the rears take 40% the weight, so each rear carries about 640 lbs, and with near-racing OEM tires (stiff sidewall and low-profile tires), I had wheel damage but not enough that the bead was damaged, so it seems like it just barely protected it.

Now that I think about it, I'm not sure if low-profile tires helps or hurts, but I'm thinking it probably helps to some degree

And when you're taxiing, I HOPE the wing's aren't taking up a significant amount of the weight!  

Edited January 21, 2022 by jaylw314

[EricJ]

33 minutes ago, jaylw314 said:

Just the assumption that the main gear takes the bulk of the weight, so that's only 2 tires, not 3.  And that's 2 tires the size of lawn mower tires, my Subaru has 17" rims and 225mm width, so that's probably 8 times the contact patch area or something?

My car weighs about 3200 lbs, and the rears take 40% the weight, so each rear carries about 640 lbs, and with near-racing OEM tires (stiff sidewall and low-profile tires), I had wheel damage but not enough that the bead was damaged, so it seems like it just barely protected it.

Now that I think about it, I'm not sure if low-profile tires helps or hurts, but I'm thinking it probably helps to some degree

And when you're taxiing, I HOPE the wing's aren't taking up a significant amount of the weight!  

On a car the main advantage of low-profile tires is so that you can fit bigger brakes, or for looks.   Depending on the tire construction there may be (or may not be) some handling advantages, but the sidewall height is unlikely to make much of a difference on a car.   Wheel material tends to weigh more than tire material, so a smaller wheel and more tire helps with weight, which is especially important with things that rotate.

The contact patch size can be easily calculated by the weight (or downforce) on the tire divided by the tire pressure in psi.   lbs/(lbs/(sq in)) = sq inches.     So contact patch size between a typical car and the main wheels on a Mooney are probably reasonably comparable.   And, yeah, the nosewheel is just there to keep the prop from hitting the ground.   On FWD cars we say the rear wheels are just there to keep the bumper from dragging. 

My track car in front of the hangar the other day.   The 17" wheels just barely clear the brake calipers, which is how it should be.   I can't put stock wheels on that car any more.

[jaylw314]

10 minutes ago, EricJ said:

On a car the main advantage of low-profile tires is so that you can fit bigger brakes, or for looks.   Depending on the tire construction there may be (or may not be) some handling advantages, but the sidewall height is unlikely to make much of a difference on a car.   Wheel material tends to weigh more than tire material, so a smaller wheel and more tire helps with weight, which is especially important with things that rotate.

The contact patch size can be easily calculated by the weight (or downforce) on the tire divided by the tire pressure in psi.   lbs/(lbs/(sq in)) = sq inches.     So contact patch size between a typical car and the main wheels on a Mooney are probably reasonably comparable.   And, yeah, the nosewheel is just there to keep the prop from hitting the ground.   On FWD cars we say the rear wheels are just there to keep the bumper from dragging. 

My track car in front of the hangar the other day.   The 17" wheels just barely clear the brake calipers, which is how it should be.   I can't put stock wheels on that car any more.
 

The contact patch thing makes sense now that I think about it  

I figure low-profile tires have comparatively stiff sidewalls compared to typical tires.  I recall checking my tire pressures one day and discovering a front was down from 36 psi to 10 psi and it was barely noticeable, whereas on my wife's Accord it would be pretty obvious

[EricJ]

1 minute ago, jaylw314 said:

The contact patch thing makes sense now that I think about it  

I figure low-profile tires have comparatively stiff sidewalls compared to typical tires.  I recall checking my tire pressures one day and discovering a front was down from 36 psi to 10 psi and it was barely noticeable, whereas on my wife's Accord it would be pretty obvious

The sidewall stiffness is construction-dependent, and there are a lot of tradeoffs.   Run-flats have *very* stiff sidewalls, and don't particularly handle better, or even well, and other low profile tires of similar size have much softer sidewalls.   So it really depends on the particular tire and what it was engineered for.   In general the sidewalls on a low-profile tire aren't any stiffer than other comparable tires.

[atpdave]

With 2 people, typical bags and 80 gal fuel, my plane (not a J) is around 3200 lb with a CG 49.6 in aft of datum.

Assuming the nose tire is around 12.5 in fwd of datum and the mains are around 63 in aft of datum (these are my rough guesses, not measured), the loads would be around 1259 lb on each main tire and 682 lb on the nose tire.

The Goodyear tire databook shows load ratings for a 6.00-6 6-ply tire to be 1750 lb and for a 5.00-5 6-ply tire it's 1285 lb so the above seems about right.

[PT20J]

Recently weighed my M20J. Empty except for full fuel.

Nose 639#

Right main 800#

Left main 788#

Skip

[PT20J]

@EricJ, the Mooney steering is pretty sensitive at high speeds. When I had a 1978J, I used to run the mains at 25 psi rather than 30 and the extra footprint seemed to make it less sensitive. Any thoughts on this? Good idea? Bad idea?

Skip

[EricJ]

12 minutes ago, PT20J said:

@EricJ, the Mooney steering is pretty sensitive at high speeds. When I had a 1978J, I used to run the mains at 25 psi rather than 30 and the extra footprint seemed to make it less sensitive. Any thoughts on this? Good idea? Bad idea?

Skip

I don't know what the tradeoffs are that lead to tire pressure recommendations on airplanes, but one potential issue with running low pressure is that the tire will heat up more at high speed.   This was the issue with the exploding Firestones on things like old Explorers, people would run them at too low pressure for too long and the tire would fail.   Airplane tires don't run very fast for very long, so I don't know whether it would be an issue unless you did a lot of touch-and-goes in a short period, but who knows.

The heat comes from more drag, so lower pressure will also make more drag and perhaps lengthen the takeoff roll a bit.   I suspect the main tradeoffs might be drag and sufficient contact patch for braking torque, but I'm just speculating.

[jaylw314]

4 hours ago, PT20J said:

@EricJ, the Mooney steering is pretty sensitive at high speeds. When I had a 1978J, I used to run the mains at 25 psi rather than 30 and the extra footprint seemed to make it less sensitive. Any thoughts on this? Good idea? Bad idea?

Skip

I'm already giving myself a hernia pulling it at 30 psi, I'd hate to think about something causing more drag! 

Edited January 22, 2022 by jaylw314

[cliffy]

Lest we forget-  big wheels and short side wall tires equal rough ride compared to 65s or 70s tall on cars.

Part of our shock" abortion on the airplane is tire wall  flex due to tire height ( hence the proper pressure needs to be maintained. )

Can you imagine a 30 tire on a Mooney with rubber pucks?  :-(

[Martin S.]

Evening gents,

picking up this topic as I plan to replace tubes + tires. I want to replace my main tire tubes with tubes that have the same stem type. Can somebody tell me what kind of stems (straight or 70 or 90 deg) I have, from the picture?

 

Many thanks + greets from Germany,

 

Martin 

Edited August 6, 2023 by Martin S.

[Fly Boomer]

20 hours ago, Martin S. said:

picking up this topic as I plan to replace tubes + tires. I want to replace my main tire tubes with tubes that have the same stem type. Can somebody tell me what kind of stems (straight or 70 or 90 deg) I have, from the picture?

Could not find exact part numbers in my logs, but I think they are

Michelin AIRSTOP    092-500-0    6.00-6    TR-20 / Straight

https://www.aircraftspruce.com/catalog/lgpages/michAviator2.php