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45 psi tire press & all due respect to Walt Aronow

donaziza

donaziza

Well Known Member
Walt, With all due respect, maybe a month ago, you had advised guys to put 45 psi in their tires. That sounded good to me, so I did it. Then I went down to land on a grass strip. After maybe 4 or 5 landings, all on the same approach,:D, I realized I had to go around. When I got back home to my cement runway, I found I was "dancing" all over the runway before I could finally confirm my wheels were solidly planted on the cement. The next time I went flying, and then tried landing at home port, I seemed to be moving sideways even though I knew my wheels where on the cement. I don't normally have problems landing. I think I need to let 5, maybe 10 psi out of my tires. Anyone else notice this? Walt? I'm all ears.:D
 
I'm not Walt but, I fly off of a grass strip that at this dry time of year is very rough. Earlier in the season when the ground was still moist, I used +-25lbs and it was a happy medium. Even when landing on asphalt. I've since changed to 35 lbs and while it feels better on pavement, my drought stricken grass runway begs for 25 lbs again.
 
I may bounce 3 or 4 times on an occasional landing, but I haven't yet correlated that to tire pressure or runway surface. I've landed on both pavement and grass with 40lb in the tires with no issues... in fact I find it easier to wheel it on with the higher pressure. YMMV?
 
I had the same experience. 45psi is way too much. It's like rolling on a Flintstone wheel which makes complete sense if you speak to a tire manufacturer about what should drive your selected pressure.
 
I run 48 psi in my mains and haven't noticed any issues, I've found I bounce it just as well at lower pressures:).
 
When I was having similar issues after moving my tire pressure up 45psi I found I was flying way too fast on short final, the flare, and even touch down. Once I slowed my approaches down and never letting the airplane touch down until it won't fly anymore my landings are now much better. I do have an AOA system installed with the audio piped into the headset which makes it very easy to safely slow down and feel comfortable. I now find myself watching other RVs on landing and noticing the landing speed vs quality of landing, which I firmly believe supports my initial statement above.

Just my 2¢
 
I set 50. Of course, all my landings are above average, like 90% of pilots.

Gents, this has nothing to do with landing ease or ride quality. Running higher pressures means less carcass heating, less tube chafing, less cord strain, less chance of wheel and wheel pant damage, shorter takeoff roll, less tread wear, and probably a few other points I have forgotten right now. I can understand if those with round gear legs must run some particular pressure to kill shimmy; it's an unfortunate crutch, the sort of compromise that sometimes must be made. On an RV-8 with flat gear? Pleeeease....
 
I switched from 32-35psi to 45/48psi when I replaced my tires (tyres) and went to 380's.

When I bounce or find the plane side stepping a bit it's all my fault, not the tires. And when I do bounce, I'm much less worried about the wheel pants.

I do think the higher pressure helps a bit with my take off distance.
 
I run 45 in all my airplanes. When it gets hard to push out of the hangar I know it's time to add air. There is a big difference in rolling resistance between 30 and 45.
 
DanH said:
<snip>
I can understand if those with round gear legs must run some particular pressure to kill shimmy; it's an unfortunate crutch, the sort of compromise that sometimes must be made. On an RV-8 with flat gear? Pleeeease....
Click to expand...

Distinction does indeed need to be made between RV-6 and RV-4 gear and the other RV models, especially the RV-8. This is not a case of one size fits all.

There is something in either the design or construction of tail draggers with round gear that can excite shimmy at certain speeds. "Solutions" have been discussed for many years (remember the wood stiffeners that were in vogue twenty years ago?) but for many of us running tire pressure less than 35 psi is the only way we have found to dampen shimmy, especially after tires have worn to some degree. This may not be optimum pressure for the tire but is a case where compromise must be made in order to have a plane that doesn't feel like it is trying to shed its gear at certain speeds.

And yes, trying to land a tail dragger too fast often doesn't end well. :)
 
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Tire pressure?

To all,
After reading the discussion about what tire to use I referred to the document provided by Cleveland when building my RV8.
The kit provided was #199-102 specifically states 31 psi., the attached note #5 states "over inflation" may result in explosive tire failure.
Hope this helps those with questions.

Mark W.
 
donaziza said:
Walt, With all due respect, maybe a month ago, you had advised guys to put 45 psi in their tires. That sounded good to me, so I did it. Then I went down to land on a grass strip. After maybe 4 or 5 landings, all on the same approach,:D, I realized I had to go around. When I got back home to my cement runway, I found I was "dancing" all over the runway before I could finally confirm my wheels were solidly planted on the cement. The next time I went flying, and then tried landing at home port, I seemed to be moving sideways even though I knew my wheels where on the cement. I don't normally have problems landing. I think I need to let 5, maybe 10 psi out of my tires. Anyone else notice this? Walt? I'm all ears.:D
Click to expand...

And with all due respect, I doubt the higher tire pressures are the cause of your landing problems, I agree that soft tires will increase drag, reduce bouncing or skipping and "soften" your landings, but the root cause of those problems are likely your landing technique.

Another reason I like 45-50 is the minimum (IMO) should be 35 so if you are like most folks and don't check your pressures as often as you should then you are less likely to fall below the min.

I can honestly say that 100% of the flats I have fixed have almost certainly been caused by low tire pressure.

I also agree that if you suffer from shimmy that a lower pressure may help, but I think that should be a last resort, tires issues, out of round tires, balancing etc will all tend to excite shimmy.
 
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When I was first flying my Phase 1, (RV7A) I spent a lot of time chasing both nose wheel and main wheel shimmy. I had started with 35lbs, went down, went up and documented everything including air temps. It was too variable. I then installed wooden stiffeners and it reduced the occurances of shimmy but did not eliminate it. I then bit the bullet at 100hrs and changed from the factory tires which still had almost new tread wear to FlightCuston 3 tires. Instantly fixed the shimmy problem that it turns out I had on nearly all landings but I attributed to "normal". I only "noticed" the really bad shimmy:eek:

I wound up going with the anti-splat nose gear and wheel mods and that fixed the nose wheel shimmy. Now I run 45psi all the way round, run the nose wheel pull out force to 28lbs instead of 22lbs and everything is great.

All in the name of education and recreation:D
 
I've been flying my '8 for 15 years. I've always run my tires at 45lbs. It doesn't dance around on the runway.
 
Sam Buchanan said:
Distinction does indeed need to be made between RV-6 and RV-4 gear and the other RV models, especially the RV-8. This is not a case of one size fits all.

There is something in either the design or construction of tail draggers with round gear that can excite shimmy at certain speeds. "Solutions" have been discussed for many years (remember the wood stiffeners that were in vogue twenty years ago?) but for many of us running tire pressure less than 35 psi is the only way we have found to dampen shimmy, especially after tires have worn to some degree. This may not be optimum pressure for the tire but is a case where compromise must be made in order to have a plane that doesn't feel like it is trying to shed its gear at certain speeds.

And yes, trying to land a tail dragger too fast often doesn't end well. :)
Click to expand...

Not sure about tail draggers but like many, I changed from 35 to 50 or even 55 pci and don't have any more issues landing that I did not have before. On the nose wheel however, I have learned that this is one way to keep it from getting a pin hole and therefore a flat.
 
RV8 Tire Pressure

During my Phase 1 testing I asked Vans what he used in their RV8 prototype and I was told 50. That is what I am using. I can blame my bad landings on many things: gusts, uneven terrain, CG loading, number of spectators, fatigue, hangover, etc, etc.
 
Tires

I suffered several flats in my first few years of flying as did one of my local buds. We now run retreads, good tubes and more air. 40-45lbs.

Works like a champ....no flats in almost 2 years. Seems like all is golden now.


Knock on wood... More pressure does certainly help.
 
cguarino said:
This is funny and everyone missed it! It wouldn't be a flat if it had air pressure.
Click to expand...

I think what Walt was trying to say was that running a tire underinflated causes the sidewalls to flex and distort excessively, which causes the tube to chafe or tear, and therefor "causes" the flat.
 
DanH said:
I set 50. Of course, all my landings are above average, like 90% of pilots.
Click to expand...

I think that 90 percent of my landings are above my personal mean :)

Only 50% are above the median though...

Just like 99% of humans have more than the mean number of legs.
 
flyeyes said:
I think that 90 percent of my landings are above my personal mean :)

Only 50% are above the median though...

Just like 99% of humans have more than the mean number of legs.
Click to expand...
Ahh, but what about the mode of your landings? :p
 
FYI... I have been using 40 to 45 on the nose, and 35 to 40 seems to be the best range for the main tires that I have experienced. It seems that although a higher pressure (more than 40) is okay for the mains, I've noticed that higher than 40 will wear the outside of the main tires too quickly (I have Flight Custom III tires).

Also, I had the Anti-Splat "nose wheel bearing mod" done to my nose wheel and tire about 1 year ago... I've not experienced any nose wheel shimmy since!! I highly recommend the nose wheel bearing mod...

Victor
 
I'm in the 45-50 camp--but what I'd really like to know is how you guys get the bird in and out of the hanger with 25-30 psi in the tires? Let mine get that low once in winter, and I couldn't move it. Felt like all 3 tires were flat. Just wonderin'.
 
I would be curious how much the tire heats up on landing. If it heats up quickly and a lot, with higher initial inflation you could be in for some serious high pressure in the tire when it gets hot. We keep our RV8 at 32 although I would prefer around 36 but my partner insists on keeping it lower and it isn't worth the battle.
 
Regarding tire heat: I would think that rolling resistance would be a big contributor to friction/heat and that the lower the tire pressure the greater the rolling resistance. My guess is that with the higher inflation values you have lower rolling resistance and less sidewall flexing. I know I am ommitting many other variables and look forward to someone who knows a lot more about tires to chime in:)

O.K. I just went and found this:
http://www.goodyearaviation.com/resources/pdf/db_airdatabook.pdf

In it it says that, for the type III tires which I assume the flight custom III tires are, the rated inflation is 50psi. It also says rated inflation is unloaded and you add 4% when inflating under load which according to my musician level, jet lagged math is 52psi. Later on in the document it talks about the risks of heat and refers to "improper inflation". I just assumed that this meant under-inflation.

Ultimately I'm surprised at how high the recommended 52psi is but that's what the manufacturer wants and has tested.
 
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