Air Pressures

[minimow]

I have a 2005' 428D w/24" tires and a 2024 400D w/26" tires. The 400D wheel calls for 06 psi but, the tire shows a wrinkle on both tires at 06 psi. Is this a problem? I've been running 09 psi on the 400D just to eliminate the wrinkle. The 2005 428D wheel recommends 09 psi which I've tried to maintain with no problems tracking or wear for 21 years.

 

[Skippydiesel]

Tyre pressures are usually determined by a combination of load (weight) and carcase deformation ie is the tyre contacting with ground at its max "footprint"

• Too high pressure reduces ground contact (convex cross section) concentrates wear on the centre of tyre and reduces the suspension effect of the tyre wall flexing.
• To low pressure results in increases ground contact in soft conditions (concave cross) (section, sand/mud), moves wear to the tyre "shoulders", causes the tyre wall to bulge, making them prone to puncture and may allow the tyre to move on the rim (both drive & steer tyres).
• The cross section shape of the tyre at a given pressure will likly differ with make/model ie just because a tyre bulges more or less, does not mean the pressure is wrong.
• Probably not relevant to mower tyre - Low pressure will cause the tyre to heat up during work. High pressure to run too cool.
• Diffrent make/model of tyre, may respond differently, to a given tyre pressure.

I would go with the mower manufactures recommended pressure for the OM tyres. If tyres changed, to diffrent brand/model, then you are on your own for optimum pressure. I doubt +/-1 psi will make a lot of difference in the short term. Observe performance (rather than shape) and increase /decrease as indicated.