M656 triangular o-ring between tire and wheel

[sangamon]

The other day I noticed that the second steering axle driver side tire on my M656 was flat.

The fellow from Les Schwab said that the triangular o-ring or gasket between the rim and bead had been pinched. He said that the o-ring needed to be replaced, but that Les Schwab didn't carry them. The triangular cross section is a half inch on each side, and the overall diameter is about twenty inches.

I've done many searches on "o-ring", "gasket", "tire", "wheel" in various combinations. The searches almost all find reference to two-piece wheels which are bolted together with a gasket between the parts.

The tires are 395/85 R20 XML Michelin X. Looking at the Michelin Truck Tire Service Manual, I found a brief reference to an o-ring. I'm hoping to be able to buy an o-ring at my local Michelin dealer on Monday. I suppose I can also have an o-ring custom made at Gardico or O-Rings Inc. Or, I can have a tube installed.

Do any of you folks have experience with this tire and wheel setup? Any suggestions?

 

[NDT]

Me thinks the o-ring started life round, but has "taken a set" as they say. I got my o-rings from a industrial supply house that specializes in o-rings for every application. They will want to know dimensions and material to match it.

 

[USMC6062]

I have a set of 20 stud combat rims that everyone trys to say takes triangle o-rings. Well I ended up contacting the manufacturer and was able to get a new set of o-rings from them and they are round. They just turn into triangles after being compressed for 20 or 30 years. One of my old o-rings that is triangle shaped still had the part number legible, and it's the same part number as my new round ones.

 

[sangamon]

I suspect that these were indeed round at one time. 40 years of compression can change a lot.

The area of a 3/8 inch circle is about the same as a 1/2 inch equilateral trangle, with less than a two percent difference.

The exact 1/2 inch sides on the ring were suspicious - I don't trust round numbers. Of course, 1/2 inch dimensions on the wheel and tire make sense, for the 40 year molding process.

It will be interesting to see what the o-ring guys say tomorrow.

 

[Stalwart]

Yup, I agree I had some o-rings in my Duster's fuel pump that took a rather strange shape, new round cross sectional ones made the fuel pump leak free again. Having a gasoline leak on a 900 CID air cooled engine is not a nice thing to behold!

 

[cranetruck]

Hmmm...what purpose does the O-ring serve? Is it to make up for the wider rim? The m656/xm757 use 12-inch rims and the spec for the XML tire here suggests a 10-inch rim.

The original 16/70-20 tires fit snuggly against the inside edges of the wheel.
(This tire is not likely a military install, but done at a later date).

 

[Tow4]

I would say the o-rings started out round. The o-rings that seal the base of aircraft engine cylinders to the case are triangular when you remove the cylinder because they fit into a chamfered space on the case. The replacement o-rings in the seal kit are a round cross section.

 

[NMC_EXP]

The other posters are correct. "Compression set" can permanently change the shape of a rubber part so it might have been a round cross section originally.

The wheel might be stamped with the manufacturer's name and part #. They could help.

Or go to a tire shop which works on bigger construction equipment tires. I think that all tubeless tires on multi-piece rims use o-rings or other seals to hold the air. The typical tire shop will not be used to this type.

When the o-ring is installed it should be lubed with soapy water (not oil) to help prevent pinching as the tire is aired up and the parts move.

Regards

Jim

 

[sangamon]

I just got off the phone with Bibendum at Michelin Tires.

Triangular o-rings are called L-rings.

L-Rings

For Highway, EM, and Grader Tires

The primary purpose of the L-Ring seal is to create an air seal where the tire bead and rim bead seat are not completely compatible. Some of the examples where the L-ring seal will prove useful:

• Where you have an irregular butt weld in the knurled bead seat area.
• Where, during initial inflation, the bead seating is very difficult.
• When an air passage between the bead and the rim is identified.
• Where overloads and severe operating conditions cause the rim deformation (deflection) which can result in air leakage.

IMPORTANT INFORMATION

• L-ring seals are not cure for damaged beads nor damaged wheels and rims.
• Caution should be used during all fitments. Do not install where a broken bead is suspected.
• Always follow the respective manufacturers’ recommendation for proper bead-lubrication and initial air pressure to properly seat beads

More later.

 

[Stalwart]

No doubt about it, they are available from Haltec.com . . . page 28 of their PDF catalog.

 

[m-35tom]

there is no 'O' ring on the original wheel, tire install. when mounting other than the correct tires you may need to use 'something' to seal the tire to the wheel. the O rings used on construction equip wheels will be the best match, but may still leak. i would just put tubes in and be sure.

tom

 

[sangamon]

To provide closure to this subject,

After discussion with Les Schwab and feedback from you folks, I decided to put a tube in the tire.

I'm keeping the old L-ring, even though it's not mounted.

I bought a spare tube (81 dollars).

Thanks for all your feedback.

What a fun vehicle this is!