Dunlop run flats

[Dan Sicotte]

I was wondering if anyone has tried to run radials instead of bias ply tires. I have a '62 Ferret, and I have to replace the original dunlop tires. I bought some used Michelin "X" 9.00 x 16 radials. Is there a problem running the original tube (bias ply) and run flat in a radial? I don't think there is, but the weight..creating heat might be an issue at 80 kph.
Any thoughts?
Dan

[Hanno Spoelstra]

Originally posted by Dan Sicotte
Is there a problem running the original tube (bias ply) and run flat in a radial?

Dan, I think there is a problem. As far as I can tell, the inner tube for a runflat tyre is much smaller in diameter since the side walls are so much thicker (4"). So using the same inner tube in a normal tyre like the Michelin, means you will have to overinflate it to fit inside the tyre properly. Not the way to go, I think.

My €0,02 worth.

Hanno
http://www.geocities.com/cmpvehicles/tyres_900-16.html

Originally posted by Hanno Spoelstra
Dan, I think there is a problem. As far as I can tell, the inner tube for a runflat tyre is much smaller in diameter since the side walls are so much thicker (4"). So using the same inner tube in a normal tyre like the Michelin, means you will have to overinflate it to fit inside the tyre properly. Not the way to go, I think.

I'd agree with Hanno.
The RF tube is quite small and specific to the RF type tyre, not only are the tyre walls very thick but the bead spreader is a very thick part also making the tube volume quite small.

But not to worry as a standard 9.00 x 16 tube and regular thin-wall flap will be needed and generally these are off the shelf. (Well, in UK anyway). Of some concern, although this may be only applicable to car size radials, is the need for a specific radial type tube as we are told here never to fit tubes into radial tyres defined as tubeless. The reasoning being that radial side wall flexing is such that the tube is rapidly fretted, overheated by friction and then bursts at high speed. You need to check carefully perhaps the exact specification of the tyres proposed.

Of slightly more concern is the radial construction of your proposed replacements and the vastly increased traction. Ferret permanent 4WD may be a problem leading to hugely increased transmission loads as these radial tyres will not slip so readily as must be needed owing to differences in tyre rolling radius and in any event when cornering as the wheels all take different radius curves.

I cannot remember if the Ferret does have a tyre circumference matching spec, but it may well do and you will probably find that not only are the radials significantly smaller in radius than the RF HS2 T24 RF's, which are probably 110% - 120% aspect ratio, but four new radial types when mounted and measured around their circumference, show appreciably different dimensions between themselves.

This is fresh in my mind presently having spent the Easter weekend re-fitting the Stalwart with 6 new NATO pattern tyres, where I know matching is important and bought 8 therefore to replace the known on the spec limit NDCC's fitted; only to find when mounted even these new tyres presented two on the spec limit of 2" difference from the largest examples of the 8 I had.

So, I currently have 2 new but unusable tyres that are stored hopefully that in the fullness of time and with some wear in the others, they may become usable to match a part worn set later on.

R.

[Richard Farrant]

Originally posted by Dan Sicotte
I was wondering if anyone has tried to run radials instead of bias ply tires. I have a '62 Ferret, and I have to replace the original dunlop tires. I bought some used Michelin "X" 9.00 x 16 radials. ?

Dan,

Do not worry about using the Michelin X on a Ferret, you are not breaking new ground. The French Army used the same tyres on their Ferrets. A friend had one of the first Ferrets in private ownership in the UK, a French one and he continued to run the Michelins without problems.

On the CVR(W) Fox armoured cars, Michelin were again used as replacement for Dunlop Trackgrip, but in this application, had Hutchinson inserts to enable them to perform as runflats.

I would suggest you run these tyres at the maximum pressure stated on the sidewall, in order to keep a small footprint on the road, this should ease the problem of transmission wind up, allowing the wheel to slip occasionally as the road surface permits.

Richard Farrant

[Phil Waterman]

My C60S Pattern 13 came out of French NATO stocks one of a bunch of radio trucks which had been stored many years. From the picture below you can see that it came shod in with Michelin radial on the front though this may just have been a convience for moving the trucks around for disposal as one was 11:00x20 and the other 12:00x20

[Dan Sicotte]

What about the 0 Degree (North America) and 5 degree (U.K) bead angles? Will that make a difference? 9.00 x 16 tubes are not available at the local tire suppliers, it's a military tube, and the tire stores don't carry them. I was told by the local moron to put 7.50 x 16, and over inflate the tube. No thanks.
I think I'll just try two tires on the back of the monster and see what happens. Also, the wheels turning all at the same time....traction and all that stuff, I haven't really got that problem....Come and drive the Montreal streets. There's never four wheels touching the ground, with all the pot holes and frost heaves.
Thanks for your all your help.
Will keep you informed as to how it works.
Dan

[Richard Farrant]

Originally posted by Dan Sicotte
.
I think I'll just try two tires on the back of the monster and see what happens. Also, the wheels turning all at the same time....traction and all that stuff, I haven't really got that problem....

Dan,

The tyres used by Frnech on their Ferrets were not block tread as in the CMP pic by Phil, they were grooved highway tyres like a civvy truck. I had heard they were used by the French Foreign Legion.

Word of warning, do not fit two different types of tyre to your Ferret, in fact never fit a new tyre along with worn ones. The circumferences should be evenly matched else you will get excessive transmission wind up and result in broken hub or bevel box.

Richard

[Dan Sicotte]

Here's the Michelin X. They are all the same size/ wear. I would like to know what transmission wind up is? I realize the bevel box situation, but the distance I was going, wouldn't hurt them.
What's the deal with the bead angles 0 and 5 degrees?

[Richard Farrant]

Originally posted by Dan Sicotte
Here's the Michelin X. They are all the same size/ wear. I would like to know what transmission wind up is? I realize the bevel box situation, but the distance I was going, wouldn't hurt them.
What's the deal with the bead angles 0 and 5 degrees?

Dan,

I don't know whether you are aware of how the transmission works, but to put it simply, both wheels on one side are geared together, the differential is in the transfer box and works side to side. If you have tyres differing even only slightly between front and rear on one side, they will fight. Even with identical tyres, when you start to turn the vehicle, one wheel is trying to travel further than the other, this is made worse if tyres are mismatched. This puts extreme load on bevel boxes and hub planet carriers.

I recently had a Dingo in the workshop (same type of trans.) and had to put an odd wheel on temporarily. I pushed it no more than a couple of feet and it stopped, jacked a wheel and it spun, let it down and I could push it a little further........wind up.

As I am not sure of the rim angle on those Michelin tyres, so cannot comment. Have you checked out if the tyre will accept the load. I suspect these are made for Land Rover and similar lighter vehicles.

Richard

[Dan Sicotte]

The tire has a load of 3970 lbs. The vehicle it was on has a weight of 3,349 kg and a load of up to 1500kg. So it's not much lighter than the ferret. I understan how the vehicle is set up, but I didn't know it was that bloody sensitive. I'll change all my fluids in order to give the bevel boxes a fighting chance.
As for the bevel on the rim, all I wanted to know was if I put the Michelin on, and it has no bevel, Will it be more likely to blow a bead if the angles don't match.
Thanks for your time.

Do you have a ferret as well? I seem to see your name around alot.
Have a good day
Dan

Originally posted by Richard Farrant
If you have tyres differing even only slightly between front and rear on one side, they will fight. Even with identical tyres, when you start to turn the vehicle, one wheel is trying to travel further than the other, this is made worse if tyres are mismatched. This puts extreme load on bevel boxes and hub planet carriers.

I have the same misgivings as Richard F, Dan; I know your picture has perhaps some perspective anomalies but the obvious visible difference in diameter of these tyres is very large and wind-up transmission loads will be horrendous and immediate.

As Richard has said, there is no give in the Ferret transmission between front and rear since the wheels are irrevocably and solidly geared together being driven at the same speed.

The apparent large difference in circumference will likely make the vehicle initially very sluggish as huge amounts of power will be lost forcing the wheels to slip on the road and probably followed in short order by catastrophic bevel box and/or hub reduction failure; possibly both.

FWIW the 2" max circumference difference allowed on FV600 chassis vehicles represents only 1.32% circumference difference, I do not know of the Ferret tyre matching spec but I'm sure one of us can find it somewhere.

The best I can do presently is from my chum Doug Greville in Oz and his website for Ferret owners: http://www.users.zetnet.co.uk/lsm/dhmg/fc-005.html
Again we see apparently 2" is the absolute maximum difference between front and rear Ferret tyres with 1" or less being the aiming point.

I think neither of us Richards that have commented want to be a wet blanket or decry your efforts to keep your Ferret on the road, but rather that you don't have a very large, dirty and expensive job replacing some heavyweight mechanicals when a critical assembly self-destructs through avoidable gross overload.

R.

[Richard Farrant]

Originally posted by Dan Sicotte
I understan how the vehicle is set up, but I didn't know it was that bloody sensitive. I'll change all my fluids in order to give the bevel boxes a fighting chance.

Do you have a ferret as well? I seem to see your name around alot.

Hi Dan,

I also see Richard Notton has answered your query echoing my thoughts about using odd / mismatched tyres on your Ferret. As he said, we do not want to appear as wet blankets, but trying to save you inevitable destruction of some part of the final drive. It is not that the vehicle is sensitive, it would actually perform alright on soft ground with mismatched tyres as they would be able to slip, the problems start when you hit the bitumen, this is when the wind up would kick in.

I do not own a Ferret, but have spent the last 32 years repairing and overhauling them and many other military vehicles for the British Army and laterly collectors and museums, so have a deep knowledge and understanding.

All the best,
Richard Farrant