The International Cessna 170 Association

I just noticed something curious about the Type Certificate Data, regarding the different tires approved for our airplanes. The standard tire being a 6:00 X 6, 4 ply, and the 7:00 and 8:00 X 6, 4 ply tires being approved as alternate tires.
It came up during a discussion with a member as to whether or not the wt & bal should be re-calulated, and while researching just how much the larger tires might add to the wt of the aircraft, I noticed that the Type certificate states:
202.
(a) 2 Main wheel 4 ply-rating tires, 6.00-6, 18 lb. (+22) (+22) (+22) Type III (with reg. tubes)
(b) 2 Main wheel 4 ply-rating tires, 7.00-6, +1 lb. (+22) (+22) (+22) Type III (with reg. tubes)
(c) 2 Main wheel 4 ply-rating tires, 8.00-6, 10 lb. (+22) (+22) (+22) Type III (with reg. tubes)

Hmmmmn....

It's hard to tell, but it looks like they want you add 1 lbs. for the 7.00 and 10 extra lbs. for 8.00 tires.

I had noticed this in the past. Good luck trying to find any other tires other than 6.00s in 4 ply. I think this is one that a lot of people have ignored in the past. Seems to be splitting hairs, lets hope we can keep this a secret!
David

Well the 120/140 TC stated it a little differently as they included the weight of the wheels. It says that the 7.00's add 2 lbs. ant the 8.00's add 10 lbs.

201. Two main wheel-brake assemblies, 6.00-6, Type III: (See NOTE 4 re variation in arms (+2)
(a) Goodyear Model L6HBD
Wheel Assembly No. 511413-M
Brake assembly No. 9520292
(1) with 6.00-6 4 ply rating tires & tubes . 34 lbs
(2) with 7.00-6 4 ply rating tires & tubes 36 lbs.
(3) with 8.00-6 4 ply rating tires & tubes 44 lbs.

The 140A TC adds +1 lb. and +10lbs respectively. Looks like they just forgot the + in front of the 10lb.

The last set of tires I bought (last spring) were 800 X 6 4 ply, from Desser. The ones before that were 4 plies also, as I recall, from Spruce.

Eric

http://www.desser.com/mccreary.html

Desser lists their Airtrac tires as having the 4 ply tires to comply with our TCDS, FWIW.

Is the larger tire, 800-6 4ply, preferable to the smaller tire, 600-6 4ply, for some reason - rough field - water sking?

Well, just a guess,... but my guess is: That the 6:00 tires weigh 18 lbs. The 7:00 tires weigh One pound more (19 lbs ?) , and the 8:00 tires weigh 10 lbs. more (28 lbs ?) than the 6:00 tire. The 170 type certificate handles the wheels/brakes weight as a seperate issue, and then also discusses the tire weights seperately.
The same wheel (but slightly different brake than on the 120/140) is stated to weigh 13 lbs. The tire weights apparently must be added to that.
Larger tires certainly should roll easier over rough ground, but would also reduce brake effectiveness slightly.