Hi All,

There's been plenty of tire talk on this site and others, but I'm hoping for some feedback specific to my situation. Any advice appreciated (including "quit dinking around with the small stuff, just go for the BW's!)

Equipment is a C170B with 145HP O-300A, 180 gear legs, 8042 climb prop, double-puck Cleavelands, Scott 3200 TW, and steel axles. No PPonk Beef Up Kit (yet).

Operating environment in summer is almost exclusively gravel, most of it maintained, some not. (Winter is skis)

Mission is having fun and having a margin, not necessarily speed.

Question at hand is whether to swap out existing McCreary 8:50x6 tires for a pair of 26" Goodyears. Both sets were/are free from friends. Both are in good condition.

One advantage in the Goodyears I think would be the smooth tire surface not grabbing and flinging rocks like the grooved McCreary's can do. A little more nose height above the gravel might extend the life of the prop too. Not sure how much of a diameter or footprint increase it really comes out to.

On the downside, weight and drag, obviously. Maybe different ground handling?

Some specific questions are:

What kind of paperwork would it require?

If the Goodyears need tubes, are the tubes from the McCreary's likely to work in them?

Do folks concur with the pros and cons listed above?

Anybody know what the increase in weight would be?

Any significant effect on vis over the glareshield during taxi?

Thanks a lot for any feedback,

-DenaliPilot

1) Moderate increase in nose height
2) Not going into the paperwork end of things, although the local FSDO most likely won't have a problem with a 170 on 26" Goodyears.
3) Noticeable difference in the amount of crap thrown on the plane with smooth skins.
4) Negligable speed difference (if at all)
5) Goodyears are about as hard as the 8:50's.

I've been doing some interesting things with the 8:50's and truly the only thing that makes me want to change the tires is some floatation in the softer areas. My strip at the cabin gets down to 700' and muddy. I'm aiming towards the 26"BW but for now, I can do just about anything I want (or dare to) on the 8:50's.

The legwork for the paperwork (field approval) is spelled out by the Alaska Region. THey have a specific process for approving oversize tires, and it's not a particularly onerous process.

The 26 inch Goodyears do use 8.50 X 6.00 inner tubes (on the blimp-the original application for these tires, they are tubeless so there is no tube for them, and the 8.50 tubes work fine).

They won't throw as much stuff at your tail, which is bigger than most folks think.

You'll add some weight, but it's not huge. Someone else has probably weighed them, or check Goodyear and McCreary's web site.

MTV

I've had both of these tires on my Champ. The GY 26" SEEM to have harder sidewalls than the 8.50's. But on your 170 I don't see this as a problem. I think the height difference was around 2 inches higher for the GY's. I eventually bought the 26" BW Airstreaks which are lighter than the GY's but not eligible for your 170. They are a much better tire though......like landing on marshmellows!!
Keith

Someone will probably correct me but I believe the McCreary 8:50x6 is smaller than the Goodyear 8:50x6. So when you do move up to the 26 inch GY Blimp tire you'll see more of a difference in height and floatation. I know you'll like flying them more than the current rubber and yes like Mike says, your inner tubes will work.

I would keep at least 10 lbs of pressure in them, just to make sure you don't sheer the valve stem under hard braking (had one sheer on me once using GY 26's). That said, I'd put the blimps on in a heartbeat over the McCreary's.

Brad

Shoot, if they're free, it's a no-brainer. Just put them on and give them a try, and follow through on the paperwork if you decide you like them.
There's a thread or two on this site or the supercub.org site about 850 versus 26", search for & read them for more pro's & cons. . I researched the weight difference once, the 850's are lighter but I forget how much. Catalog sez the airtrac 850's weigh 16.5# each not counting tubes. You can weight the 26'ers yourself if you have them at hand.

Eric

I'm going from the 8.50x6 on the mains of my 172 to the 26" GY when it gets back from the paint shop next Wednesday (FINALLY!!!!). I'm doing it to lift the tail somewhat.

Don

Contact Wagonwrench about the GY 26's, he will give you an honest opinion.

He just put them on his '55 C180 which is almost as light as some 170's. I have the Mc 8.50's on my '55 180 and there is a big difference in size and floatation. I wish I had a photo to show it. Pilots who say GY's are stiff tires are usually flying light planes like Cubs and such. They are not as soft as BW's of course, but they do bulge nicely under a heavier plane. For what you are going to do, it sounds like a no-brainer, put the GY's on and enjoy.

The only disadvantage that I see in blimp tires is the cost and since that's not an issue for you, I agree it's a no brainer since you operate off of gravel. Air Tracs are a good tire for the money, but they do sling rocks

Ok, here is a really dumb question that Ive been holding in for awhile...

Why do the 26" GY's require a tube ?

Bob K.
Anchorage, AK

To hold the air.
(sorry, I couldn't resist!)
Bushwheels are tubeless in that they have an internal air bladder, all other light aircraft tires that I'm aware of require tubes. The wheels we use are apparently not condusive to a tubeless operation.

Eric

One of the reasons may be that the rims are split in the middle. I would think air would leak out there.

flyer

It's the wheels that require the tube. Tubeless wheels have an O-ring right where the two wheel halves meet to hold air. At least helicopter wheels do, I wouldn't think they are any different from airplane wheels in that regard.
If the three holes that hold the hub cap on went all the way through the rim, then long sheet metal screws could be used to hold on the hub cap and the screws could protrude into the tire side wall and prevent the tire from rotating on the wheel and pulling the valve stem out, and none would be the wiser . Just ensure the screws don't go all of the way through the tire and into the tube .

Yeah, I knew I would get flamed for that question...

I knew Bushwheels didnt run tubes, but having never inspected one un-mounted, I didnt realize they had a built-in bladder. I knew about the split rims of aircraft wheels, but also knew that the Bushwheels go on those same wheels without tubes... Hence, my question.

If one were to "seal" the split rim, either with an o-ring, or some sort of device, would it be possible to run tubeless ? Im guessing that the next issue would be that aircraft tires probably dont have a bead around the edges that would seal with the wheel good enough to prevent leakage.

What kind of setup do the actual Blimps run, where these are actually run tubeless ?

Sorry for the rambling... Just trying to think of how I can stretch my GY's a little further without shelling out the $$$ for some ABW's.

Hasta ~

Bob K.
Anchorage, AK

Thanks for the good input everyone. I think protecting my tail feathers and wing roots is going to be the main reason for me to do it. I've still got totally splattered wing undersides from breakup season that I need to rinse off.

-DP

I'm sure you could machine a groove in each wheel for a O-ring but I'm unsure how you could modify the wheel to take a tubeless valve stem. Of course then you have modified a part. I'm pretty sure the bead would hold air. I'm unsure that all of the effort would be worth while though. Maybe there is a factory tubeless 6" wheel?

I have run both the 8.50's, and the the 26" GY's on my 180. I was perfectly happy with the "feel" of the 8.50's (goodyear retreads, 22" dia.)on rough dirt strips. With 15 #'s of air pressure, they were quite soft.

I went to the 26" GY's (with the help of wagonwrench) because they were a treadless tire, and more affordable for me than the Bush Wheels. I wanted the treadless tire to reduce rock slinging, and damage to my plane.

The 26" are about 20#'s heavier if I remember correctly, which was no big deal in itself, but I do try to keep the weight down where I can. I also have a friend that had flown 180's after changing to the 26" and felt that they deceased his climb performance significantly.

I now have a tool, compliments of our friend Wup, that allowed me to open the grooves on my 8'50's so they can no longer pick up rocks, and sling them at my "baby".

So, now I have put my 8'50's back on, am about 20 #'s lighter, and somewhere around 3-5 kts. faster. And a cheaper tire to replace when the time comes.

That's my take on all this.

Gary

shortfielder wrote:..............I now have a tool, compliments of our friend Wup, that allowed me to open the grooves on my 8'50's so they can no longer pick up rocks, and sling them at my "baby". .........................Gary

Please elaborate on this tool.... does it change the tread from straight grooves to V-grooves? I can see where that would reduce the rock slinging. How long did it take to modify each tire?

Eric

Eric

It is a handheld tool, about the size of a utility knife. It has a U shaped,serrated, razor blade. It does change the shape of the groove from a U to a V. Took me about 5 min. per tire. I removed the tire and wheel to do it. Left the tire mounted. Didn't do quite as neat a job as I was hopeing for, but it did a good job, and I am happy with the results.

Gary

shortfielder wrote:Eric

It is a handheld tool, about the size of a utility knife. It has a U shaped,serrated, razor blade. It does change the shape of the groove from a U to a V. Took me about 5 min. per tire. I removed the tire and wheel to do it. Left the tire mounted. Didn't do quite as neat a job as I was hopeing for, but it did a good job, and I am happy with the results.

Gary

And where can we obtain such a tool? I would like to try it on my 8.50's before I go and by bush wheels.
Is it something I can make? By at Home Depot? Come on man Your keeping us inquiring minds in the dark