The International Cessna^® 170 Association

I'd like to hear what air pressure you guys are using in your Scott talwheels- (3200- 8 inch tire / tube)
Should the tire be off the ground when inflating ? Does it matter ?
I've been using 56 psi.
Rudy

I use about 40. Seems to work OK, no uneven wear & no shimmy.

Eric

With the (relatively) light weight on the tailwheel of a stock
main-geared 170, I agree 40psi is a good number to start
with.

You start moving up to 180s, later model 180s and 185s, and
there is a significant amount of additional weight on the
tail which tends to warrant a bit more tailwheel tire pressure on
those models.

Eric, Bela, thanks- do you raise the tail wheel off the ground to inflate ?
We don't do it with main wheels - does it matter ?
Rudy

Rudy

This subject has been discussed before and there is a Scott recommended pressure. I think it's about 35 but not sure. And as I recall a lot of owners ran lower than 40, Because I'm always about gross weight on my return flights from weekly shopping (NEVER over of course) I go with 45 tailwheel and 30 mains. Pretty much the same as I ran in the 180. Mains are 6:00 x 6 Flight Custom III.

Pretty sure all tire pressures are given with the load on them not in the free air. Wonder how much difference it would be if any.

I would like to observe someone testing tire pressure in "free air" Does this mean with the struts jacked or at altitude?

Rudy,

I have never seen anything that suggested auto or 170 tires should be "unloaded" to inflate. I do check my tire pressures often and tend to inflate mains (small tires) to 30 PSI and the tail wheel (smaller tire) to 35 PSI. I do this because it is easier to manhandle the airplane on the ground and, theoretically....the takeoff run is shortened due to lower rolling resistance of the tires. But I ain't done no tests in no controlled environment to confirm. Howsomever, IF my 170 was shod with 800 tires, I would probably drop the pressure on the mains to about 24 PSI cuz my airplane just feels better at lower pressures in big, draggy tires.
Some have said their 170s are a bit squirrely wilth tire pressures above 24 PSI, but I seem to be squirrely at ANY pressure. For what its worth...Chuck

Both Cessna and Scott published recommended tire pressures (with the aircraft at gross weight). The mains (600X6) should be inflated to 24 psi, the tailwheel should be inflated to 30 psi (Scott) and 34 psi (Cessna). (These pressures should be confirmed while on the ground, running alongside at 52 mph.)

I ran my Scott tailwheel pressure at 50lbs because I read that exerted the least pressure on the tailwheel structure. Within a year I noticed the center of the tire tread was worn out. Back to 30lbs and no problems.

I use the TLAR (that looks about right) method on inflating the tailwheel, because my gauge lets out too much air when I check it. I inflate the tailwheel 'till the patch of rubber in contact with the floor is roughly square. This seems to high enough pressure to keep the tire on the rim in a crosswind, and low enough for a good ride.

Miles

The Scott instructions (illustrated on page 5-26 of the SRAM for those of you who bought that book from TIC170A) shows that aircraft useage of the tailwheel should have a 1/2" deflection of the tire. (Yes, this device was also used in some industrial applications, where higher pressures are allowed to provide only a 1/4" deflection.)
When the weight is on the tire, the flat portion of the tire pressing against the hangar floor should be deflected as much as 1/2" from the fully round shape in aircraft use. The graph also depicts the amount of tire pressure vs weight-on-wheel allowed for aircraft use.
That graph shows that for about 300 lbs of wt on the tailwheel, 35 psi is about right. (The graph is another example of how some things are measured with the micrometer, marked with a grease pencil, and cut with a hatchet. If you have the graph to view, you'll see what I mean.) In any case, in a textual manner, the recommended tire pressures for various weights are: <280 lbs = 30 psi, 300 lbs = 35 psi, 350 lbs = 45 psi, 480 lbs (max allowed...way too much for a 170) 70 psi.