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  #11  
Old 05-08-2014, 06:56 PM
chrispratt's Avatar
chrispratt chrispratt is offline
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Default Another vote for 50

Another vote for 50 psi. I use Condor tires and Michelin Air Stops. Nine years ago, I was told to use 50 psi by Jay Pratt and I always do what Jay says . I believe that's what Michelin recommends also. 50 makes it easier to push around the hangar among other advantages. I refill about every 4-6 months depending on my flight activity.
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  #12  
Old 05-27-2014, 02:45 PM
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I use 38 PSI but I like to fly into grass strips and wanted a little more give to soften the roll out. Having said that, I think 50 PSI makes a lot of sense for most guys, especially ones never leaving pavement. You'll see less wear for one thing. Or more centralized tread wear. I tend to see a bit more on the edges v when I run higher pressures, which tend the wear the middle quicker. Frankly, anything between 35 and 50 works fine.

As far as handling I've not noticed much difference between either settings. You might see slightly faster deceleration with the lower pressure, or a slightly softer feel to your full stall landings, but medium and low speed steering is about idiot proof in the RV-8. Higher pressure doesn't make it more squirrely. At least not in my experience. As tail draggers go its one of the easiest to keep straight.
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  #13  
Old 06-11-2014, 03:57 PM
judoka5051 judoka5051 is offline
 
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Location: Stuart, FL
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Default RV8A won't slow down!

Hey Guys,

I've been reading all these tire pressure threads and I haven't seen my problem mentioned. This problem occurs on pavement (luckily I'm based on a grass strip). When I land it takes forever for the plane to slow down, and it will never go below about 25mph without brakes. This also occurs while taxiing from a stop. It slowly accelerates to about 25mph unless I apply brakes. I'm currently using about 35psi in the mains and 40 in the nosewheel. This is a pain because even if I put it down at 60mph on the numbers I use up lots of runway. I have the Idle set at 800. The plane is very light, so I'm sure that exacerbates the problem. I'm tempted to lower the tire pressure to 25 (or even less), but most responses seem to like higher numbers. Any suggestions?

Thanks, Lance
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  #14  
Old 06-11-2014, 04:57 PM
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BruceEicher BruceEicher is offline
 
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Default Lower RPM

Hi Lance
With my metal fixed pitch, IO-360 I have the static RPM just below 600. At a full stop the engine will quit if the ball is all the way back.
I taxi at 650 RPM no brakes
Tire pressure 46.7
This saves my brakes, is quieter, plus slows us down on final.
Inflight idle RPM is higher of course.
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Last edited by BruceEicher : 06-11-2014 at 05:00 PM.
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  #15  
Old 06-11-2014, 06:31 PM
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Sam Buchanan Sam Buchanan is offline
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Quote:
Originally Posted by judoka5051 View Post
I have the Idle set at 800.
That is too high for a fixed-pitch prop. As stated previously, you need to get it down to ~600 rpm.
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  #16  
Old 06-11-2014, 07:16 PM
judoka5051 judoka5051 is offline
 
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Sounds good, I'll give that a try. I had a wood prop originally, and it didn't like a lower rpm, but I switched to a carbon fiber that's 4 lbs heavier, so maybe I can slow it down.

Thanks, Lance
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Plane at X58

Scratchbuilt Biplane
Preceptor N3 - Sold
Zenith Zodiac 601HD - Sold (good riddance)
Kitfox IV - Sold my share, but loved that plane
RV8A Sold! Loved the plane, but not the nosewheel!
RVX (RV6/4) Sold
RV8 Project purchased (Can't help myself)
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  #17  
Old 06-11-2014, 11:20 PM
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ColoRv ColoRv is offline
 
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You gents running 50psi must be flying from very smooth southern runways. I tried 42 here on Colorado's bumpy runways and it wasn't a pleasant ride. Asked several RV8 guys here in town and all are in the low to mid 30's as well. I'm back at 34psi. Stock vans tires, Michelin Airstop tubes and grove gear.
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  #18  
Old 06-12-2014, 08:07 AM
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Quote:
Originally Posted by ColoRv View Post
You gents running 50psi must be flying from very smooth southern runways.
Ride quality was never a consideration. I would suggest a sharp pavement lip is even more reason to set correct pressure, as are most hangar tracks.

The Tire & Rim Association: 500-5 6 Ply - 50lbs psi
(Dresser site, page bottom) http://www.vansaircrafttires.com/pag...B47%7DFAQ.html

Michelin Tire Databook: 50-5 6 ply 50 psi
http://www.airmichelin.com/generalcontent.aspx?id=219

Goodyear Aircraft Tire Databook: 500-5 6 ply 50 psi
http://www.goodyearaviation.com/reso...edatabook.html

The Neal Willford landing gear design spreadsheet is S409. It should still be available for download at the EAA site. Plug in the values for your RV-8 and look at the drop test tire compression for various tire pressures.

As for "they say", well.....

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Last edited by DanH : 08-27-2015 at 07:18 AM.
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  #19  
Old 06-12-2014, 09:27 AM
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ColoRv ColoRv is offline
 
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Wow Dan, you're pretty sure your way is the only way aren't you? I tend to put more emphasis on field data than spreadsheets and in this case several thousand flight hours in the same plane, on the same runways with actual tire wear data accumulated over years...is more relevant to me than a spreadsheet.

Monkey see monkey do is also called learning from experience. Still, I am as capable of falling back to a chart as the next guy and the chart on Desser.com says the maximum tire pressure for Vans issued tire is 50psi. Running a tire at its maximum psi when not supporting its maximum weight is unnecessary.

As in all forms of inflated tire from race cars to over the road trucking, the tire provides a good chunk of the suspension give. Harsh ride may not be a consideration, but it does tell you what the tire is doing if you pay attention. Having my tires absorb and roll over that sharp pavement edge while staying in contact with the pavement rather than bounce off of it like a brick and skip certainly merits consideration when that pavement is often wet, snowy or very cold as well. Proper inflation depends on weight and unless your RV8 weighs 2570 lbs (Desser chart), 50psi isn't necessary. The surface you land on will greatly affect the proper pressure.
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Last edited by ColoRv : 06-12-2014 at 10:19 AM.
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  #20  
Old 06-12-2014, 10:11 AM
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humptybump humptybump is offline
 
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Default

Quote:
Originally Posted by ColoRv View Post
gents running 50psi must be flying from very smooth southern runways
I have tried two full seasons at 35 psi and two full seasons at 45-50 psi. flipped the tires with the pressure change. All the same RV-8 and living on a short field grass runway (that is not a golfing fairway) and a majority of destination being the same. Typical runway conditions is wet in the morning and dry in the afternoon. When it's cold, it's raw and cold. I don't plow so when it's snowing, I'm not flying.

My personal experience is that ground handling is easier at the higher pressure. Take off has been a bit better at the higher pressure. Landing has been easier at the higher pressure.

This is just one pilot's data ... and yes, I'm now from the south
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Last edited by humptybump : 06-12-2014 at 10:14 AM.
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