The International Cessna^® 170 Association

Ha, I get to answer this one for George, Rudi...my original 1952 owners manual specifies 24 psi for the mains and 34 psi for the tailwheel. I tried 40 psi on the mains once (before I aligned the gear) and it made it handle like a Pitts Special...

I think that the 2,000 pound number Cessna reccomends was their idea of an
average flying weight, in those days the 170 was a workhorse of the short-haul air taxi fleet carrying two or three passengers. These days most of
us fly around with one or two people, IMHO. At any rate, I ballasted mine up to about 1,800 pounds to reflect my operation. Russ Farris

Also take a straight edge or string line from the side of the wheels or brake disk back to the tail to check the alignment with the rest of the plane. Otherwise you could have the wheels parrallel but tracking // or \\.

David, I think Aircraft Spruce carries the Cessna gear shims.

Also, check out the 1948 Cessna gear alignment service bulletin, if you haven't already at http://www.cessna120-140.org/library/se ... /SL_56.htm
It has lots of good info, I found it very helpful. I also replaced all bolts and nuts holding the axle to the gear and torqued to spec. (remember the torque values are predicated on the size of the bolt shank, NOT the size of the bolt head!) Don't ask how I know...Russ Farris

'Well, I just tried my link to the service bulletin and it didn't work, SOOO just go the Cessna 120-140 owners site and dig it out, or Google "cessna landing gear alignment" and it appears on about the third page toward the the bottom.
Sorry about that Chief! (may Don Adams rest in peace...) Russ Farris

Russ,
I could not get the link to work either, so I copied the Service letter and posted it here. I hope it is not copyrighted information.

When I set the alignment in my 170 I found that there are actually several different shims available. My local Cessna service center parts supplier made it easy for me, they allowed me to take their whole parts bin and do a little trial and error testing. Our 170 parts manual lists 4 different shims and the Single engine service manual lists maybe 7 variations and the parts bin had more like 9 choices.

I also did a variation or Rosberrys suggestion I used a cheap Chraftsman lazer level that puts out a light in plane (it has a level bubble on top allowing you to be sure the light plane is veritcal). I leveled the plane side to side and then found the center of the firewall and projected the lazer light through that that point and the center of the tail wheel spring. Using the now established center line light plane I was able to measure the angle of each of the wheels relative to the center line of the fuselage and adjust the toe.

I found my right wheel toed in .7 of a degree and my left wheel toed out .4 of a degree and while this may seem like a small amount the improvement in handleing is remarkable. When you set the toe right you can tell as soon as you push the airplane around the ramp.


CESSNA SERVICE LETTER SLN-56

DATE: 08-03-48

SUBJECT: Checking and Adjustment of Wheel Alignment

1 .Original Adjustment

The main landing gear wheel installation on all series Cessna airplanes are set at the angle which experience has indicated as resulting in the longest possible tire life. The possibility of slight variations from the original setting does exist. For example, a slight shifting of the landing gear leaf in the fitting up at the fuselage end could result in a change of the toe-out alignment of the wheel. The wheel alignment, therefore should be checked shortly after the airplane is placed in service and of course alignment should be checked at anytime that excessive tire wear indications are present.

2. How to check alignment

The first step is to make sure that the wheels are in a neutral position. In other words make sure you have relieved all effects of turning or pushing the airplane around the hanger floor. To do this, push the airplane forward in a straight line for a few feet. Avoid doing this on wet cement. The toe-in and toe-out checking is done at the factory at the wheel flanges. A simple check fixture can be manufactured for doing this checking. A simple but accurate checking job, without a check fixture, can be done as follows: Place a straight edge across the front face of the tires and then place a carpenter's square backward from this straight edge on the outside of either tire. Then measure inboard from the carpenter's square to the rear and front flange of the wheel. The difference in this distance will indicate the amount of toe-in or toe-out existing on that wheel. The original setting as measured above on the various model airplanes at their empty weight is listed below. The first figure is the amount of toe-in which we try to get and which is the ideal setting. The tolerances are indicated next to each figure.

SHIP EMPTY WEIGHT

MODEL DESIRED TOE-IN TOLERANCE
120 & 140 1/16" 0 TOE-OUT 1/8" TOE-IN
170 0 0 TOE-OUT 1/16" TOE-IN
190 & 195 1/16" 0 TOE-OUT 1/8" TOE-IN

3. How adjustments are made

The adjustment is made with wedge shaped shims that are installed between the axle assembly and the landing gear spring unit. These shims are tapered in two directions so that they result in variations of toe-in as well as camber. There is no specific reading or setting which we try to maintain as far as camber is concerned as experience indicates that any reasonable variance in camber does not in any way affect tire wear. Tire wear is apparently the result in greatest proportion to misalignment in toe-in.

The following shims are available for the various models.

MODEL 120 & 140

1 degree and 2 degree shims are available for the 120 and 140 models. Page 50 and 51 of the 120 and 140 Parts Catalog outline the shims available as well as the various bolts that are necessary by serial number. In making the shim installation, it is very important that the shim be installed correctly, that is, with the thickest corner forward and down.

MODEL 170

At present, one special shim is available. The following table lists the partnumbers for the shims and the bolts that are necessary for their installation.

0541111 Shim Main landing gear
AN5-22A Upper Bolts
AN5-23A Lower Bolts

Again the correct position of the wedge is very important. The thickest corner is to be installed for ward and up. Additional 140 shims are to be used as required.

MODEL 190 & 195

1 degree and 2 degree shims are available. the following table lists them by part number and also lists the bolts that are necessary for their installation.

0341116-1 Shim-Main Landing Gear 1 degree
0341116-2 Shim-Main Landing Gear 2 degree
AN6-21A Bolts

Again the correct shim installation is very important. The shims are to be installed with the thick corner forward and down.

Finer variations may be obtained by grinding down any particular shim or in some cases by the omission of shims altogether, but generally it has been found that as long as the resultant toe in is within the tolerance listed in section two above, tire wear will be satisfactory.

4. Other Considerations

Tire wear due to excessive toe in or toe out generally results in tire wear on approximately one half of the tire tread. Excessive toe in will result in wearing of the tire on the outer half of the tread while excessive toe out results in wear of the inboard half of the tire tread.

The use of brakes does, of course, add to tire wear. This is particularly true on hard surfaces where brakes are used for steering purposes instead of the rudder and steerable tail wheel. It is a good idea, particularly on the 190 and 195, to make sure the parking brake handle completely released prior to taxing.

The amount of air in the tires also has a good deal of bearing on the rate of tire wear. Too much air in the tires results in no give in the tire with a resultant scuffing that greatly increases tire wear. The following list shows the correct tire pressures which will result in smoothest operation of the landing gear with maximum of tire life.

190-195 Main Wheels 32#
Tail Wheel 45#
170 Main Wheels 24#
140 Main Wheels 16#

I have a couple friends who insist that triangulating the main gear is important-- in other words, measuring to the MLG axles from a point back at the tail, to check that the MLG legs are not fore-and-aft of each other. This is in addition to checking castor relative to each other, as well as relative to the aircraft centerline.
Camber: mine has positive camber (top-out), I prefer this as when the gear legs flex (like when landing) there's plenty of tire left as the camber changes to negative. This also allows tire life to be extended, as when the outboard side of the tread wears down there's plenty of fresh tread on the inboard side -- you can then rotate the tire 180 degrees on the wheel and get a bunch more landings out of it.
A tip on the "greased plates" method of checking toe-in/out-- use of castor oil (get it? ) between the plates is mandatory!

Eric

zero.one.victor wrote:I have a couple friends who insist that triangulating the main gear is important-- in other words, measuring to the MLG axles from a point back at the tail, to check that the MLG legs are not fore-and-aft of each other.
Eric

If you found one MLG fore or aft of the other, what would/could you do about it? Would that indicate that a gear leg or the gear box has been tweaked?

zero.one.victor wrote:you can then rotate the tire 180 degrees on the wheel and get a bunch more landings out of it.

Just to reduce the confusion factor, he means turn the tire over; simply rotating the tire on the wheel won't acomplish much (Eric, I tried, but I just couldn't resist, sorry! )

zero.one.victor wrote:A tip on the "greased plates" method of checking toe-in/out-- use of castor oil (get it? ) between the plates is mandatory!

An old friend once told me there are three kinds of jokes: those that are that are clean, those that are funny, and those that are just BAAAAD. That one's in the third category!

Miles

By the way Eric, you deserve credit once again. I reread the old thread on rudder springs and reconnected mine by loosing the rudder cable at the rudder, as you suggested... wow, that is sooo much easier! It took me a total of about five minutes where last time when I replaced it through the tunnel it took an hour or two. If I ever fly it to the NW I owe you a beer, (would that be Olympia?).
David

David, I don't even know if they still brew Oly, but I know they still brew good old Ranier!
Miles, I couldn't resist the baaaad play on words. Thanks for clarifying my tire-turnover wording.
Fore and aft MLG- I'm not too sure just what I'd do about it. Mine triangulates just fine from the tail. But it would be something to be aware of, if not to necessarily correct, when checking alignment. Your LH & RH wheels might be parallel to each other, but not parallel to the airframe. I've heard of a local 180 that had one early gear leg & one late gear leg, the early/late gear legs had about a 3" difference in forward "rake". Supposedly the beast handled OK but it seems to me that it couldn't help but be squirrelly on the ground. If the wheels were aligned with each other & with the airframe, it would appear to be way out of kilter checking it via the straight-edge across the front of the wheels method detailed above.

Eric

When I had my gear out to do the P-ponk I found it could be easy to allow the gear leg to move fore or aft on installation the lock wedges. So I measured before I torqued them.
As for tires I use the 1 psi for each 100lb gross weight, so I have been keeping my mains about 22-23 psi and my tailwheel seems happy at 34 psi ( no rule for the tailwheel ) As for the mains I think this formula works on the bigger tires because it was my bush instructor friend who told me this who runs his supercub on alaska bushwheels.

as for alignment of the axles, keep in mind the shims are a double taper, I mark them so when I start flipping the around I dont lose track ( no pun intended) of what postition I have tried.

cessna170bdriver wrote:

zero.one.victor wrote:]A tip on the "greased plates" method of checking toe-in/out-- use of castor oil (get it? ) between the plates is mandatory!

An old friend once told me there are three kinds of jokes: those that are that are clean, those that are funny, and those that are just BAAAAD. That one's in the third category!

Miles

Yeah. That one was pretty hard to swallow. (get it? )

gahorn wrote:

cessna170bdriver wrote:

zero.one.victor wrote:]A tip on the "greased plates" method of checking toe-in/out-- use of castor oil (get it? ) between the plates is mandatory!

An old friend once told me there are three kinds of jokes: those that are that are clean, those that are funny, and those that are just BAAAAD. That one's in the third category!

Miles

Yeah. That one was pretty hard to swallow. (get it? )

Miles, I think George just went over the edge into that forth catigory of joke, you know the ones that leave a baaaad taste in your mouth.

Hi just a question
I bought a cessna 170 ragwing and also have felt like I have the hardest airoplane in the world to fly. I have a lot of tailwheel landings being a glider tug pilot and having over a thousand landings and takeoffs in Super cubs, Callairs and Scouts in all kinds of conditions but I just excepted that you dont land a c170 in a crosswind ( especialy after I ground looped it with 2 children and an adult aboard, Broken tail wheel cloth damage to tip and one elavator slight bent no prop strike. and a very dinted ego ) Now if it is blowing or possible crosswind I dont fly Mabe you guys have the answer. Also My aircraft was fitted with Cessn 180 main legs do you know of this mod and would it have any effect on the wheel alignements you guys have suggested here

Steve

Steve,

If you have flown a Super Cub, the 170 should't be a problem. I transitioned to my 170B from 75 hours and maybe a few hundred landings in a J-3. I found the 170 much easier in crosswinds. The maximum demonstrated crosswind is 17 knots as best as I remember. I personally managed it once with the tower calling a steady 20. Sounds like you might have a serious alignment problem. As long as BOTH gear are 180, it shouldn't cause a problem. How are the tires wearing? How does it track with no crosswind?

Miles

Steve,
My 170 experience is very limited at this point, but I've got quite a bit of recent time in various other taildraggers (140, Tcraft, 7GCBC, etc.) From what I can tell so far, the 170 is one of the easiest to handle that I've flown to date. It sure sounds to me like you've got some other type of underlying problem (gear related). That, or maybe you're just having a problem making the transition back to a yoke from flying the stick of the SuperCub?