Are Runflats worth trying to save???

[Swamp Donkey]

Thanks for the advice Gents. I guess I can try a combination of compressing the run flats using a ratchet and also use the engine hoist to pull them gently out.
Hmmmmm, now I am confused as to whether I should leave them in or not? Sounds like there can be a safety benefit in having them but, fuel costs will add up over the years and acceleration may be reduced due to the mass. One writer even suggested that they will wear out the tyres from the inside very quickly (thats a worry when the tyre costs about $1800)? Do I need to regularly re grease them to stop them wreaking the tyres? Why would they even put grease in them unless they tend to rotate inside the tyre. If thats so, then they 'will' eventually wreck the tyre from the inside. Perhaps for the military its a trade off between shortened lifespan and extra safety that they can afford?. As a civilian, soon to retire, I wont be able to afford a second set of tyres. As I will be fitting pressure and temperature monitors and driving within the G speed rating, hopefully I wont get a blow out?

I'll make a couple of points.

The runflat never touches the tire unless the tire is flat. No extra wear to the tire will be caused by the runflat when the tire is inflated.

The military runflat in the 395/85R20 tires weighs about 150# each. It would use more fuel to get them moving, but would use less fuel once they are moving because of the momentum gained from the extra weight through centrepital force. Consider how a heavier flywheel takes longer to stop turning than are lighter one, of the same diameter. The fuel cost will be mostly negated.

The extra 600# from 4 runflats on a 4 wheeled vehicle is added at the very lowest point on the vehicle. This can only help on the stability side of things.

The tire, and the belts inside, were not designed to support a load with a solid object compressing it from the inside and the outside. It was designed to support the load with air on the inside and the ground on the outside. The runflat is considered a solid object even though it is rubber. The excess flexing and weight put on the tread portion of the tire causes belt damage, whether obvious or not. I personally would not reuse a tire that had been driven flat, with or without a runflat. Civilian tire shops that deal with runflats don't either.

On a 395/85R20 the distance from the rim lip to the ground is roughly 11". That would be the distance that the end of the axle dropped during a blowout. The runflat will cut that distance by at least half. On the front axle, the less the suspension changes at speed, the less it will affect steering. This is a huge benefit for steer tires.

I've broken down 9 new MRAP tire/wheel assemblies with runflats so far to change out the valve stems to something compatible with my truck. The date codes spanned over a 6 year period and none had any lube in them at all. I prefer it that way since I would replace the tire driven on the runflat anyways as I stated above. No need for all that mess when breaking down a tire. For extended driving on just a flat tire, not a blowout, a runflat will need lube because the rubber on rubber contact will create heat. I just want to limp to a place to change the tire and I won't be reusing it anyways.

Some personal preference mixed in but hope this helps. I would keep them. Once you take them out, you'll never get them back in if you change your mind.

 

[gimpyrobb]

If you use grease, use silicone based grease. Regular grease will eat the rubber.

 

[simp5782]

https://www.youtube.com/watch?v=qlzSljf1h1g

 

[acesneights1]

This is an interesting conversation because I just got some 16.00 xzls and two have run flats in them. I thought about leaving them in and running them on the front but my concern was how much out of balance they will make the tire ?

 

[someoldmoose]

I have never had one cause an imbalance. Experience is in OTR operation.

 

[simp5782]

I have a slight wobble at 52 to 54mph but its nothing really.

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[BenRoberts]

1800 per tire. Wow I paid 250. Prices are high down under

 

[Jason Firm]

Gents, I'm a little closer to an understanding. Sounds like:
- the donut somehow does not rotate inside the tyre during normal use. How it does this from just looking at it, I am totally unsure, and hence a little skeptical? I suspect that it probably does rotate for a little while until the vehicle gets up to constant speed and then rotates in sync with tyre.
- the donut does rotate a lot when the tyre has suffered catastrophic failure and the grease simply helps it all to hold together a little longer than otherwise.
- even if no grease, the donut will give the tyre enough time until the vehicle can be pulled over in a more controlled fashion.
- risk of a wobble.
In the event of an incident, I suspect that the insurance companies here (being a bastard lot like most insurance companies) would use every excuse not to pay out such as a non Australian approved insert (our military does not use them). Thanks everyone for the good advice, I will be removing them as the likelihood (with my driving) of a blow out, is low.
By the way, if I purchased here in Oz, a new the set of 4 would cost me A$8000+ including rims (I suspect) and I would have warranty. If I import from the USA, its A$2650 plus freight A$2240 but no return & no warranty. A big part of the freight is the local courier cost of A$800 for freight of the pallet from Unionville Indiana to Compton, CA. But I guess its a no brainer to take the risk and buy at almost half price.

I attach (hopefully), a picture of the cheap wheel our army normally uses (at rear of Unimog) and the real deal at the front.

 

[someoldmoose]

Sounds righteous to me. Now go gitcha sum mud on them thar tahrs !

 

[simp5782]

Gents, I'm a little closer to an understanding. Sounds like:
- the donut somehow does not rotate inside the tyre during normal use. How it does this from just looking at it, I am totally unsure, and hence a little skeptical? I suspect that it probably does rotate for a little while until the vehicle gets up to constant speed and then rotates in sync with tyre.
- the donut does rotate a lot when the tyre has suffered catastrophic failure and the grease simply helps it all to hold together a little longer than otherwise.
- even if no grease, the donut will give the tyre enough time until the vehicle can be pulled over in a more controlled fashion.
- risk of a wobble.
In the event of an incident, I suspect that the insurance companies here (being a bastard lot like most insurance companies) would use every excuse not to pay out such as a non Australian approved insert (our military does not use them). Thanks everyone for the good advice, I will be removing them as the likelihood (with my driving) of a blow out, is low.
By the way, if I purchased here in Oz, a new the set of 4 would cost me A$8000+ including rims (I suspect) and I would have warranty. If I import from the USA, its A$2650 plus freight A$2240 but no return & no warranty. A big part of the freight is the local courier cost of A$800 for freight of the pallet from Unionville Indiana to Compton, CA. But I guess its a no brainer to take the risk and buy at almost half price.

I attach (hopefully), a picture of the cheap wheel our army normally uses (at rear of Unimog) and the real deal at the front.

Check with Feltz tire in new Boston, Texas Your buying stuff from c and c equipment which is overpriced anyway

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[bonedoc]

I found the easiest and safest way to remove the run flats from a 395 was to lay iton its side, place an engine hoist on top of tire. Wrap a chain around the run flat and hook to hoist. Start cranking it out. When the exposed part of the run flat starts to really stretch the bead and has alot of tension on it slice it with a sawzall blade about 6" from chain. Because of the tension on the run flat it will cut like butter. Just obviously be careful not nick the bead of the tire. Once cut the run flat will corkscrew out of the tire like a big curly fry. Mine all has a ton of lube in them. It is messy and slick but is water soluble and washes up fairly easily.

 

[The King Machine]

https://www.youtube.com/watch?v=qlzSljf1h1g

That looked like the tire was giving birth................

 

[Swamp Donkey]

Gents, I'm a little closer to an understanding. Sounds like:
- the donut somehow does not rotate inside the tyre during normal use. How it does this from just looking at it, I am totally unsure, and hence a little skeptical? I suspect that it probably does rotate for a little while until the vehicle gets up to constant speed and then rotates in sync with tyre.
- the donut does rotate a lot when the tyre has suffered catastrophic failure and the grease simply helps it all to hold together a little longer than otherwise.
- even if no grease, the donut will give the tyre enough time until the vehicle can be pulled over in a more controlled fashion.
- risk of a wobble.
In the event of an incident, I suspect that the insurance companies here (being a bastard lot like most insurance companies) would use every excuse not to pay out such as a non Australian approved insert (our military does not use them). Thanks everyone for the good advice, I will be removing them as the likelihood (with my driving) of a blow out, is low.
By the way, if I purchased here in Oz, a new the set of 4 would cost me A$8000+ including rims (I suspect) and I would have warranty. If I import from the USA, its A$2650 plus freight A$2240 but no return & no warranty. A big part of the freight is the local courier cost of A$800 for freight of the pallet from Unionville Indiana to Compton, CA. But I guess its a no brainer to take the risk and buy at almost half price.

I attach (hopefully), a picture of the cheap wheel our army normally uses (at rear of Unimog) and the real deal at the front.

The runflat does not spin on the wheel. It is clamped in place by the 2 wheel halves when the wheel is assembled. The bead of the tire is clamped between the runflat and wheel lip on each side. This is why you also have beadlocks if you have runflats. The beads and runflat are clamped in place. I only speak for the runflats in the 395/85R20 military tires. Other runflats that use a different design, or are used in one piece wheels, can work differently.

I really like those wheels on the front!

 

[gimpyrobb]

The runflat does not spin on the wheel. It is clamped in place by the 2 wheel halves when the wheel is assembled. The bead of the tire is clamped between the runflat and wheel lip on each side. This is why you also have beadlocks if you have runflats. The beads and runflat are clamped in place. I only speak for the runflats in the 395/85R20 military tires. Other runflats that use a different design, or are used in one piece wheels, can work differently.

I really like those wheels on the front!

Ditto.

 

[Special T]

If you use grease, use silicone based grease. Regular grease will eat the rubber.

I've done some examination of this "grease" and believe it is in fact tire soap commonly used in every tire shop around.

The reason for this is because it's water soluble and I don't know of any grease that is. ALSO tire soap looks similar when first applied and then heated up. Starts life looking creamy yellow and ends up smoky/black

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[Jason Firm]

Thanks Gents. The Hutchinson mil spec rims I am looking at, are alloy one piece. Thats why I assumed the donuts might rotate a bit. Just found out that the standard steel split rims are 11.5mm thick whereas the alloy rim is 30mm thick. Hence I need to replace the wheel hub studs. Was quoted A$42 each. Thats $1689 just for buying the longer studs. I also have to either modify the guards or raise the cab or puy in lift springs & shockies etc. Its a learning experience for me.

 

[Swamp Donkey]

Thanks Gents. The Hutchinson mil spec rims I am looking at, are alloy one piece. Thats why I assumed the donuts might rotate a bit. Just found out that the standard steel split rims are 11.5mm thick whereas the alloy rim is 30mm thick. Hence I need to replace the wheel hub studs. Was quoted A$42 each. Thats $1689 just for buying the longer studs. I also have to either modify the guards or raise the cab or puy in lift springs & shockies etc. Its a learning experience for me.

I'm not sure that the runflats inside those tires are compatible with one piece wheels. You'd have to verify with Hutchinson since they make the runflat and the wheel you want. They might have to be removed whether you decided to keep them or not.

If you do call them, I'd be interested in their response.

 

[Jason Firm]

Hello. I have written to Hutchinson via their web site but no replies. I don't expect any. When I said 1 piece rim, I really should have said 2 piece (but not 3 piece). Looking closer at the run-flats, possibly the flanges on them do clamp at the edges near the rims, and possibly they don't rotate at all during normal running and possibly from what Special T said, its just tyre soap left from the original fitment. So maybe they are not so bad after all if they are wedged firmly in place by the beads?
I left various messages with Feltz Tyres (direct and their ebay site) but no replies. Very good prices on tyres but no info on rims.

 

[Special T]

I think the balancing issues stem from the fact that the run flat has a lot of mass rotating. If the wheels are torqed down properly it would likely help. Most of the guys that run military tires for wheeling use pvc inserts which are ligher and less prone to vibration.

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[red]

Thanks Gents. The Hutchinson mil spec rims I am looking at, are alloy one piece. Thats why I assumed the donuts might rotate a bit. Just found out that the standard steel split rims are 11.5mm thick whereas the alloy rim is 30mm thick. Hence I need to replace the wheel hub studs. Was quoted A$42 each. Thats $1689 just for buying the longer studs. I also have to either modify the guards or raise the cab or puy in lift springs & shockies etc. Its a learning experience for me.

I run aluminum wheels from the Caimen MRAP's on my m816 which require longer wheel studs. Cost per stud is about $4 each