Ribs on the inside surface of tires 1

[jbortell]

I'm just wondering if there's any technical purpose to the ribs you see on the inside surface of car tires. Some tires have smooth insides, some have "leather look" textures, some have heavy ribbing. I would think they have a negligible impact on the stiffness of the sidewall for comfort purposes.

 

[GregLocock]

You are right they have no effect on the stiffness of the tire. They are almost certainly there to get the rubber to flow correctly in the mold. Sadly the probability of a real tire engineer showing up and commenting is small, tire manufacturers have an attitude to secrecy that was more stringent than Defense.

Cheers

Greg Locock


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[Compositepro]

Such patterns prevent air from being trapped between the rubber and the mold surface, and allow it to vent. Cotton threads serve the same purpose between internal plies of rubber.

 

[CapriRacer]

GregLocock said: " ….. Sadly the probability of a real tire engineer showing up and commenting is small, ….."

Nope it's 100%.

Those ribs and texture are there to allow air to escape during the shaping part of the curing cycle.

If you watch videos of how tires are made, there is a part of the process where the tire is put into the mold. There is a rubber bladder on the inside that is inflated after the mold is closed. Then a considerable amount of pressure is used to inflate the bladder. That bladder has marks on it to allow air to escape between the tire and the bladder - and there are grooves at the base of the bladder that vent the air to the outside.

There are also vents on the outside performing the same purpose - you know, those little strands of rubber. I've seen the word "spew" to describe these, but no one I know within the tire industry uses that term. Usually they are trimmed off - or they have a mushroom shaped valve that closes, but leaves a small round impression. Go look at the outside of the tires on your car to see these.

Here's a photo of those vents:

Here's one showing the other kind - the mushroom shaped. Note the circles:

 

[GregLocock]

Thank you. I hadn't realised you were a tire engineer, I assumed you were R&H from other comments you've made!

Cheers

Greg Locock


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[BUGGAR]

Sprues are those passages interconnecting parts in the mold in metal castings. I forgot what they called the "overflow" vents. Sometimes they are big enough to act as reservoirs for the shrinking metal below. Sorry to go off topic.

 

[IRstuff]

Sprues are those passages interconnecting parts in the mold in metal castings

Not just metal, but also polystyrene models

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