Tyre and wheel sizes?

[Marty_d]

Hi,

 

I have to confess my ignorance here, I have no idea what the numbers on tyres mean.

 

I want to get a set of bigger tyres that fit the rims I have.  I don't really want to spend a fortune doing it (I've seen 21" tyres advertised for almost $600 each).

 

So below is a photo of my nosewheel - it has the numbers 15 x 6.00 - 6 on it.

 

What does that mean?  It's not 15 inches diameter, it's around 13 (unless I haven't pumped it up enough).  

If I want to get bigger tyres, eg 21", where's the best place to get them?  Some forums in the Zenith site discuss bigger tyres for $30 each - golf cart?

Any advice would be much appreciated.

 

Thanks, Marty

 

 

 

[onetrack]

Marty, the link below will help you out. See "Three-number tire sizing". The first number is supposed to be the tyre diameter when inflated, but this is a "rubbery" dimension (pun intended), according to the individual tyre manufacturer.

 

https://www.tires-easy.com/blog/lawn-tractor-tires-sizing-buying-guide/#:~:text=15×6.00-6 is,the width of the rim.

 

Back Country Pilot has written up what appears to be a pretty informative "knowledge" article on aircraft tyres and sizing.

 

https://backcountrypilot.org/knowledge-base/aircraft/90-knowledge-base/aircraft/188-tire-guide

 

I'd think you might have to import, as a special order, any "non-standard" set of tyres. Be aware that the speed rating on golf cart and turf tyres is generally pretty low - about 20mph (32kmh).

 

Edited January 26, 2022 by onetrack

[fallowdeer]

IHi Marty

 

Larger tyres and small $$$$ don’t seem to go together when I look at what I’ve spent……. One solution for you that might work are the 8.00 x 6 Carlisle  “Turf Glide” tyres.  Yes, I know the specifications on them are decidedly unimpressive but they have been a popular tyre on Savannahs at least here in NZ. 
 

There are two S models locally that have been shod with them for over 300 hours total with no problems, one being a factory built that came that way.  They used to be supplied as a kit option for Savannah, I don’t know if that’s the case now.   
 

I’ve used for over 600hrs 21/800 x 6 for mains and 600 x6  nose wheel and these have worked well for gravel bars and other unimproved strips.  I only put the 600 x 6  on because I used the standard nose fork, in hindsight I should have changed the fork to use an 800 x 6 nose tyre.  The 600 x 6 has an adequate diameter but just a little less “bearing area” on the surface than I consider desirable.

 

Very popular in NZ are the Aero Classic 8.50 x 6 treadless tyres, but fitting three of these necessitates a custom nose fork together with shortening the nose leg.  There is a useful gain in prop clearance also and I’ve seen that some quite rough surfaces can be utilised with this set up if care is taken to protect the nose gear.
 

(Nose gear is an area where the older VG Savannahs and 701s are decidedly superior to XL and S model Savannahs the reason being that S and XL models have a firewall inclined 6 degrees more to the vertical than the earlier Savannahs/701s. Thus in the older aircraft some of that touchdown force is converted into compression of the leg as against a bending moment.  More than one S model over here has suffered a nose leg collapse, but from my experience of over 800hrs on type and giving instruction in them it takes a fair bit of mishandling to damage the nose gear….)

 

Peter

 

 

Edited January 27, 2022 by fallowdeer
Add photo

[Lucky01]

G'day Marty,

 

I come across these fellas the other day for pricing on tyres, might be worth a phone call?

 

https://www.waggabiketyres.com/lsa_tyres.html

[onetrack]

Just remember that the 8.00 x 6 Carlisle "Turf Glide" tyres have a speed rating of A3 - which is 15kmh or 9mph. They also have a load index of 49 - which is 185kgs or 408lbs. 

I'd be very reluctant to fit tyres with this low a speed and load index rating, when your landing speed is say 70 or 80 kmh, and you could be landing with over 500kgs dropping on them, as they make contact with the ground.

 

From my crane training, if you drop a suspended load 50mm or 2", and then stop it falling, it doubles the loading on the rigging (the chain or wire rope).

 

Thus, a fast descent with a rough and bouncy landing could be doubling the load being applied to the tyres.

So it's quite feasible a rough landing in the average kitplane could be placing a shock loading (albeit, a transient loading) of up to 2000kgs on the tyres.

 

It's a bit of a credit to tyre manufacturers that the safety margin built in to tyres is pretty huge, but it still pays to know what your tyres are designed and specified to handle.

[kgwilson]

Check also the ply rating. Cheap tyres made for lawnmowers, trolleys etc are often only 2 ply. Aviation tyres are almost always 6 ply up to 10 ply and more. I have McReary 500-5 Airhawks which are TSOed and that adds a lot to the cost. They are 6 ply and have a high rated load of 1285 lbs, can be inflated to 50psi and have a 120 mph speed limit. Obviously you have different needs with a STOL type aircraft but landing on rough strips and making mistakes so you hit hard are things to consider. Speed will probably not be an issue. Just for reference mine cost $160.00 each and the tube costs $155.00. Luckily I have not had to buy tubes. All this is one of the reasons I prefer to land on the grass

[turboplanner]

4 hours ago, onetrack said:

Just remember that the 8.00 x 6 Carlisle "Turf Glide" tyres have a speed rating of A3 - which is 15kmh or 9mph. They also have a load index of 49 - which is 185kgs or 408lbs. 

I'd be very reluctant to fit tyres with this low a speed and load index rating, when your landing speed is say 70 or 80 kmh, and you could be landing with over 500kgs dropping on them, as they make contact with the ground.

 

From my crane training, if you drop a suspended load 50mm or 2", and then stop it falling, it doubles the loading on the rigging (the chain or wire rope).

 

Thus, a fast descent with a rough and bouncy landing could be doubling the load being applied to the tyres.

So it's quite feasible a rough landing in the average kitplane could be placing a shock loading (albeit, a transient loading) of up to 2000kgs on the tyres.

 

It's a bit of a credit to tyre manufacturers that the safety margin built in to tyres is pretty huge, but it still pays to know what your tyres are designed and specified to handle.

I'd agree with you about the low speed rating - they mean it.  I've had two implement tyres explode in the last couple of days, just from the hot sun. They're designed for very low speed, slower than you can run, so low heat build up.

[onetrack]

The Trelleborg data sheet (link below) shows that the largest proportion of Trelleborg farm/turf/light industrial tyres are usually rated at 30kmh. However, Trelleborg do make a few tyres that are rated for 100kmh.

These Trelleborg tyres are accordingly marked, "HS", to indicate their High Speed rating.

 

Unfortunately, there's only one Trelleborg tyre in 6" rim size that is rated HS - and unfortunately, that tyre comes only in 4.10/3.50-6 size, which is not an aircraft tyre size.

You need to go up to 8" rim sizes to find a bigger range of Trelleborg HS tyres.

 

https://www.trelleborg.com/wheels/-/media/tires-aft/datatsheet/brochure/trelleborg_light_industrial_tire_eng_master_2019_lr.pdf?rev=418828deaa6c4944abda1a13971e10df&hash=A2243F893E2457308FC9D517E3A4B6F7

 

Interestingly, Wagga Bike Tyres says that the Trelleborg T510 in 13x5.00-6 size with a 6ply rating, is the Jabiru recommendation for the Jab nosewheel tyre. 

But the Trelleborg data sheet specifies the Trelleborg T510 in 13x5.00-6 with 6 ply rating, as only having a speed rating of 30kmh - but the tyre does have a load rating of 250kg.

 

I must say I'm a little surprised at this Jabiru choice of nosewheel tyre, but perhaps they discussed their choice with Trelleborg, and Trelleborg advised that their speed rating is a rating for a consistent speed, and overspeed for short distances is permissible.

 

https://www.waggabiketyres.com/lsa_tyres.html

 

(CORRECTION TO PREVIOUS POSTING: I only just noticed my fat finger hit "2" instead of "1" in my previous posting. Of course, a tyre load doubling as a result of a heavy landing, means the figure should be "1000kgs", not "2000kgs")

[Thruster88]

The maximum speeds are for a fully loaded tyre in continuous operation. A landing aircraft would be a fraction of that. Don't recall any tyre failure in the xxxxxx database.  

[Marty_d]

I would have thought that companies such as Wagga Bike Tyres would be in a bit of trouble advertising Carlisle Turf Glide in their LSA section, if there was anything but a miniscule chance of failing.  Most companies are extremely risk averse when it comes to aviation, as I found out when trying to get someone to test my control cables.

 

[kgwilson]

Those Carlisle 8.00-6 tyres are advertised on Skyshop for $205.00 and state they are popular for Airborne Edge,  Skyfox, Foxbat & Savannah. They are 4 ply. While they may only have a slow speed recommendation, it seems there have been few if any problems with them.

 

Speed and load ratings on aviation specific tyres are high because the momentary twist when you touch down tries to rip the tyre from the rim especially in a cross wind situation so sidewall strength is important hence the number of plys. Load rating is also important when you make a bad landing by flaring too high or landing hard and crash down on to the wheels generating a load possibly two or more times the aircraft weight.

 

Skyshop also sells what they call a Jabiru tyre for $55.00. 6 ply (13.00 5.00-6/6 t510). No brand name is mentioned but they say recommended for Jabiru and other recreational aircraft.

[biggles]

I’ve been running those Trelleborg T510’s, mains and nose wheel, for about 10 years now on the Jab 160. Never had a problem, but always replace the tube with a new tyre …. Bob 

[skippydiesel]

F

On 26/01/2022 at 3:18 PM, Marty_d said:

FYI The definition of a

 

WHEEL - RIM + TYRE

RIM       - RIM - TYRE

TYRE    - TYRE - RIM

Pedantic ? Yes Far to many people (including in the trade) mix these terms up, causing unnecessary confusion.

 

The words come from the time of wooden wheels with steel tyres.

 

[Marty_d]

9 hours ago, kgwilson said:

Those Carlisle 8.00-6 tyres are advertised on Skyshop for $205.00 and state they are popular for Airborne Edge,  Skyfox, Foxbat & Savannah. They are 4 ply. While they may only have a slow speed recommendation, it seems there have been few if any problems with them.

 

Speed and load ratings on aviation specific tyres are high because the momentary twist when you touch down tries to rip the tyre from the rim especially in a cross wind situation so sidewall strength is important hence the number of plys. Load rating is also important when you make a bad landing by flaring too high or landing hard and crash down on to the wheels generating a load possibly two or more times the aircraft weight.

 

Skyshop also sells what they call a Jabiru tyre for $55.00. 6 ply (13.00 5.00-6/6 t510). No brand name is mentioned but they say recommended for Jabiru and other recreational aircraft.

Wagga Bike Tyres sell the Carlisles for $155, so Skyshop are charging a bit much. 

 

I've put a level on the wing mounting points and I could raise the nose another 20mm to get the aircraft perfectly level, plus if the Carlisles are 16" compared to my current 13" I'll gain another 1.5" (38mm) there.  That makes it 58mm + my original 1040mm so 1098mm, which would make a 70" prop tip 209mm from the ground.

 

That's still not ideal but the 701 plans state 1100mm and a lot of them would swing a 70" prop, so might just have to do it.

 

Plus I have a spare nose fork which will fit the bigger tyre - bought it from Zenith as I couldn't get the right thickness aluminium in Aus at the time, then bought the undercarriage off a written-off Sav anyway.  The Zenith fork is a lot wider than the Sav one and has a bit of extra length so I can lower the axle a bit.

[Blueadventures]

1 hour ago, Marty_d said:

Wagga Bike Tyres sell the Carlisles for $155, so Skyshop are charging a bit much. 

 

I've put a level on the wing mounting points and I could raise the nose another 20mm to get the aircraft perfectly level, plus if the Carlisles are 16" compared to my current 13" I'll gain another 1.5" (38mm) there.  That makes it 58mm + my original 1040mm so 1098mm, which would make a 70" prop tip 209mm from the ground.

 

That's still not ideal but the 701 plans state 1100mm and a lot of them would swing a 70" prop, so might just have to do it.

 

Plus I have a spare nose fork which will fit the bigger tyre - bought it from Zenith as I couldn't get the right thickness aluminium in Aus at the time, then bought the undercarriage off a written-off Sav anyway.  The Zenith fork is a lot wider than the Sav one and has a bit of extra length so I can lower the axle a bit.

Wagga are great to deal with, very informative webb site and if you phone will answer your questions from experience.

 

Re prop clearance Eprops would be 175mm dia so just under 69" so that will give another 12'5 or so mm clearance.  Check with Mark Kyle or their webb site.

[Marty_d]

1 minute ago, Blueadventures said:

Wagga are great to deal with, very informative webb site and if you phone will answer your questions from experience.

 

Re prop clearance Eprops would be 175mm dia so just under 69" so that will give another 12'5 or so mm clearance.  Check with Mark Kyle or their webb site.

I decided not to go with the E-prop.  They sound fantastic but are an extra $1000 and I just worry a little about how narrow they are, in terms of longevity and strength.  I wanted to go with the Meglin but 4 month turnaround after you pay full price, and with what's going on with Russia I didn't want to risk it.  So I'm back to Bolly and either their 66" or 70".  Bolly say the 70" is better for STOL and the 66" for cruise - she'll never be a cruiser so I would prefer the 70".

[meglin]

I think we are risking more when we continue to fulfill your orders during air raids and shelling. We just turn on the music louder so that we don't hear the sound of the siren.