Tyre pressures

[Skippydiesel]

Yes but I think Sonex are talking about the 4" tires. By the time we are talking Goodyear we are at 5".

Generally - the smaller the tire the higher the oressure

Thanks Graham - In the Sonex advice there was no mention of tyre brand or size. You are most likely correct in your assumption (smaller tyres).

It seems to me that the teams advised pressure range, at least initially, has narrowed considerably. We seem to be in the 30-40 psi range (given manufacturers advice & real world experience).

For the most part I will be operating of grass. This environment combined with the light weight of the Sonex (yet to be weighed) suggests to me that 35 psi might just be a good start point.

Initial taxi testing should give some indication of tyre heating - to hot (above + 4 C rise) increase the pressure, to low (below 4 C) reduce pressure.

[GraemeSmith]

I run my 5" Airhawks (horrible tires - but I bought cheap while trying out a larger tire) at 45psi on grass and pavement. 40psi on ice for a little more contact patch.

[Skippydiesel]

I run my 5" Airhawks (horrible tires - but I bought cheap while trying out a larger tire) at 45psi on grass and pavement. 40psi on ice for a little more contact patch.

Good info Graham and directly relevant to my 5" Goodyear's.

Thankfully I rarely have to deal with ice.

[GordonTurner]

Rarely? Does that include sometimes?

[N190YX]

45 PSI is a little high for a 5:00X5 tire, the data for my factory airplane for the 5:00X5 tire on the nose gear specifies 40 PSI.

[GraemeSmith]

45 PSI is a little high for a 5:00X5 tire, the data for my factory airplane for the 5:00X5 tire on the nose gear specifies 40 PSI.

It's not that simple. The tires have a maximum ply/load/pressure from the manufacturer. You can then work under those parameters to see what works best for you:

Product Code Size Ply Rating Max. Load Inflation Pressure
AB3D2 5.00-5 4 800 31
AB3D4 5.00-5 6 1285 50
AB3D8 5.00-5 10 2150 80

[radfordc]

Whatever the right pressure is I can tell you what happens if the pressure is too low and you land on pavement. Shears off the valve stem and makes it very hard to taxi!

[Skippydiesel]

45 PSI is a little high for a 5:00X5 tire, the data for my factory airplane for the 5:00X5 tire on the nose gear specifies 40 PSI.

I "guild the lily" - Where I live and have lived around NSW & a little in Vic, we do get a few early morning frosts per year. If there is standing water (puddles, water troughs, etc) a thin film of ice can form - short lived, as frosty mornings are usually followed by beautiful clear warm days - great flying. I have never lived in the Australian high country where winters are similar to the northern hemisphere.

[DCASonex]

Take a look at your AUSA wheels. There is a max pressure listed on them that as i recall was about 35 PSI. 50 PSI may be okay with the small tires, but the larger ones put more pressure on the rims trying to separate the two halves and there have been reported problems with the thru bolts on those. I have found 25 PSI works fine on mine for the last 10 years mostly on hard surfaces but occasional on turf as well. I would not recommend over 35 PSI.

David A. Sonex TD, w/ 3300