The International Cessna 170 Association

Let's talk tire pressure & tube wear. I'd like to know what MLG tire pressure people are running in 600-6, 6-ply tires? First, I acknowledge the topic of tire pressure has been discussed before; this 2016 thread as an example: viewtopic.php?f=24&t=12948&hilit=tire+pressure However, I've just recently had two(2) tube failures, blamed on low tire pressure by Desser.

I had Air Hawk 600-6, 6 ply tires installed. I was running 30 psi pressure in them. My problems started on my most recent trip to northwestern Minnesota. The day after I landed and tied down, the left MLG tire was found completely flat. Then, within 11 landings of that, on returning home, the right MLG tire was flat on landing. Forensic examination of both tubes showed they had simply been worn through by the inside of the tire casing, to the point where the air leaked out. There was no evidence of any type of foreign object, puncture, or other reason why these tubes would start leaking.

Talking to Enoch at Desser, he showed their resident expert a picture of my tube, and he believes it was low tire pressure that was responsible, but here's where it gets interesting. As was brought up in the earlier thread, their data says to air my 6-ply tires to 42 psi! If I had 4-ply tires installed, they would be happy at 28 psi. To add to the confusion, the owner's manual for the 54 (and 56) C170B stipulates 24 psi for the MLG tires.

I'm guessing there are very few of us flying around with 42 psi in our MLG tires. I'd like to hear others experiences and opinions on this topic. Has anyone else experienced tube failures that couldn't be attributed to foreign object puncture/damage? I'll upload the two documents and a picture with this post.

I have been running 700 and 800 MLG tires on my 170B for 33 years and 3000 hours. I run 24 lbs. and have never had a flat. Never ran Dressers though, but just about everything else. I always powder the inside of the tire and outside of the tube liberally w/ talcum powder for what it's worth when I install them. Sounds like a tire or tube problem to me. Curious to hear what others say, for now I don't think I'll be buying dressers though...

Joe Moilanen
4518C

I run 24psi on 4 ply Goodyears 600X6. I recently had a flat on one MLG in the hangar. The tube wore through and made a pin hole. However I have no idea how old it was. Tire looked ok inside. I’ve had the plane for two years and just replaced the other side because of worn tire. I have a new tire and tube in a box waiting for the opportunity to change the side that went flat. I replaced the tube only on that side just to get back up with a new tube because the tire looked ok.

Generally, I thought the only danger of under inflation would be the tire moving on the rim when the tube can’t. Perhaps they want higher psi on the six ply tires because they are stiffer and more prone to moving on the rim during landing. Only a guess.

Main Tires should be aired to 24 psi. Tires should be liberally dusted with TALC evenly distributed before inserting the tube. The tire and tube should be inflated on the wheel then allowed to completely RELAX before re-inflation to 24 psi.

If the tube has rubbed inside the tire…it was likely not properly dusted with TALC.

(Caution: Do not breathe Talc. It can cause “silicosis” lung disease. Talc is a mineral which does not readily decompose. Do not substitute “baby powder” which in recent decades is actually made from CORN STARCH…not Talc…because of the health hazards of Talc when it is used for personal hygiene (uterine cancer and lung disease).

Tire Talc can be purchased from Desser and perhaps from some other sources. (I have found it at cheap “Dollar” stores sold as talcum powder, but beware to make certain it is genuine Talc…not cornstarch.)

I have never had a tube become damaged from rubbing because I always use Talc. My present Aero Classic tires (6:00x6, 4-ply) and McCreery tubes (purchased from Desser) were installed in 2008 and still hold air reliably at 24 psi.

(Air Hawks are $120 cheaper and probably just as good, IMO.)

I installed the tires with talc sprinkled on the tube. My issue may be that I wasn't "liberal" enough with the talc (possibly because I'm not liberal in other areas of thought - but that's a topic for another time ). George, how would you quantify how much talc you use? I had thought of it as an assembly aid, not a maintenance substance. Are we saying there needs to be enough to make the tire and tube slide relative to each other for years?

Exactly! I toss “liberal” amount into the empty tire…then roll the tire around on the floor both vertically and horizontally… there will always be a tablespoon or two of excess talc…that’s good. Then install the tube and (with the schraeder/valve-core removed) I inflate the tube to fill the tire and then let it relax. I next install the assembled tire/tube into the wheel and bolt it up.
Next, inflate again and let it relax… then inflate for final psi….and mount on the airplane.

Be “generous” (I.E., “Liberal”) with the Talc…(and with most other things. LIBeral shares a root word with LIberty.) heh-heh

I recently had to put a new tube in one of my 8.50-6 Smoothies due to a mesquite thorn puncture landing on a rough ranch strip.

The tire/tube had been installed without talc at the last annual. When I tried to remove the flat tube from the tire, it had bonded itself to the “balance patch” inside the tire. After having a very difficult time pulling the tube loose, it had similar looking abrasion marks to Karl’s tube. Might not be the same problem but I have never seen that before.

I completely coated the new tube with real talc from Spruce and talc was rubbed all inside the tire. The talc stuck especially tight to the “balance patch”. I also make sure to clean the talc from the tire bead area where it seals onto the wheel, I have had a tire spin on the wheel shearing the valve stem off of the tube, probably due to low inflation.