[Leoshashi]

Recently I came across this video:

https://www.youtube.com/watch?v=O2h2RzkWY3c

I was surprised to see that layer of foam inside the tyre. Upon some digging, came across this:

Your vehicle’s tires are rolling kick drums. Keith Moon played two; your car plays four. Expansion joints, potholes, and heaves pound the rubber, which compresses the air inside and transmits hollow thuds to the cabin.

As cars get quieter, engineers are working to stifle the drumbeat of tire impacts. Their current favored method is polyurethane insulation glued around the tire’s inner liner. These acoustically insulated tires have stealthily spread through the market to the point that they are now offered by all the major tire manufacturers and come installed from the factory on several high-end luxury vehicles, including those hallmarks of tranquility, the Mercedes-*Maybach S600 and the Tesla Model S.

Tire manufacturers see big potential for the technology as electrification silences powertrains, making tires one of the most obvious sources of sound intrusion. The main function of inner tire insulation is to improve the tire sound quality, specifically by absorbing impact noise. In actuality, it reduces overall cabin volumes only slightly. It has the greatest effect on frequencies near 200 hertz (Hz), a sound that is low in pitch, relative to what the human ear can register, but is at the high end of the frequencies a tire generates. Think of the deep ping of a bouncing basketball. “You hear it if the tire goes over an expansion joint,” says Scott Pajtas, technical sales director of Michelin. “It can also be a constant tone if there’s a road-surface irregularity or a uniformity irregularity in the tire.”

Continental claims that their ContiSilent brand of tyres can reduce such noises by almost 9dB.



My query: If the claims are so good, why can't we add the insulation material to the insides of the normal tyres? How hard can it be?

I'd like to learn what can possibly go wrong if this is attempted as a DIY.

Regards,
Shashi

[Sankar]

If you put a high density foam thick enough you will probably end up making DIY runflat tyres Interesting to know the extent manufacturers go to create silence.

[audioholic]

The concept is pretty convincing. Adding insulation material to a tyre isnt a difficult thing to do, but we have to think of the following aspects:
1. What are we going to add into the tyre, and how. From the gist of it, it looks like we will need a polyurethane foam, with good temperature resistance, and also an adhesive which can withstand the temperature change that a tyre usually undergoes, and also withstand a LOT of flexing. Else we will have the adhesive come off and the foam will be free from the tyre. I think these are the aspects where the research in tyre companies will be on, like what to add, how much to add and how to add it to the inner wall of the tyre. Nevertheless, an experiment will not do harm IMO, worst case you will have the foam separating out into the rim which shouldnt cause serious issues.

2. What is the expected benefit from this - Noise reduction. That is, when tyre noise is a major issue. For a car like the Tesla, or a Mercedes, tyre noise is a big deal. The cars are engineered to be extremely silent with no wind noise, no external noise but then the tyres come from a different source. Tyre noise can be the most prominent things to hear in these vehicles. In such cases, reduction in tyre noise can make the overall NVH of these cars even better. But for a mass market car, unless you are really annoyed with tyre noise while the rest of the car is very silent, it would not make a noticeable difference even if we get the first point bang on target.

Hence, considering the above two, DIY is possible, but I am not sure of the benefits.

[NaXal]

I think it would be easier for someone to first give the readily available foam material a try with bike tyres. No balancing required & should be cheap on labor to try on.

This should give a better picture on the actual durability under practical driving. Once satisfied with foam & glue holding & it not creating any adverse effect, one can proceed to the real deal with the car tyre.

Just a personal thought.

Thanks.

[BoneCollector]

Originally Posted by Leoshashi

My query: If the claims are so good, why can't we add the insulation material to the insides of the normal tyres? How hard can it be?

I'd like to learn what can possibly go wrong if this is attempted as a DIY.

Regards,
Shashi

As said by audioholic, if the foam separates from the tyre, it may cause some issues. Instead of using foam, why not try Styrofoam?

Styrofoam

Originally Posted by audioholic

Hence, considering the above two, DIY is possible, but I am not sure of the benefits.

Exactly my thoughts, I'm not sure about its benefits.

Originally Posted by NaXal

I think would be easier for some one to first give the readily available foam meterial a try with bikes tyre. No balancing required & should be cheap on labor to try on.

Trying something on a 2 wheeler tyre as DIY, I would not recommend. Simple reason being that any issue leading to tyre failure on a 2 wheeler would be extremely dangerous compared to a 4 wheeler.

[dhanushs]

Wondering what the weight distribution and balancing will be on 'not a good road' and at speed.

Anyhow, I don't think IC cars need such in-depth noise-cancelling and its the electric cars with the weird eery silence of the engine requires these!

[sgiitk]

All very fine. However it does increase the unsprung weight. This is the ultimate sin in the view of many.

We we use alloys, not for flash but for the same purpose.

[Leoshashi]

Thanks Gentlemen for your thoughts.

Originally Posted by dhanushs

Wondering what the weight distribution and balancing will be on 'not a good road' and at speed.

The Teslas and high end Mercs have been facing this issue of foam separating from the tyre on bad roads and ruining the wheel balancing. In fact Tesla recommends checking the foam first if any case of wheel imbalance is reported.



https://teslamotorsclub.com/tmc/thre...y-tire.155908/

Originally Posted by BoneCollector

Exactly my thoughts, I'm not sure about its benefits.

While Conti claims reduction of upto 9dB, some real world tests show that these tyres hardly make any difference. An interesting read:

https://www.caranddriver.com/news/a1...sh-road-noise/

Originally Posted by sgiitk

All very fine. However it does increase the unsprung weight.

Valid point.

We use alloys, not for flash but for the same purpose.

While my post is completely unrelated to the discussions going on here, I'd like to point out, with due respect, that the Alloys are lighter theory isn't always true.

When I was looking for alloys for my M800, I was excited about the reduction in unsprung weight the alloys will bring, over the stock rims. Infact, the commonly available Neos and Platis were actually lighter than the steel rim. But the MGA branded, Hindalco(Aura Wheels) manufactured alloys turned out to be heavier than the standard rims, and this was an eye opener. In fact it depends on the build, material used etc of the alloys. Same thing happened with my friend, whose Punto's stock rims were actually lighter than the Momos he had installed.

Stock vs alloy rims:



Weight of my 800's Wheel on stock steel rims:



Weight after shifting to alloys:



Regards,
Shashi

[srishiva]

Originally Posted by Sankar

If you put a high density foam thick enough you will probably end up making DIY runflat tyres Interesting to know the extent manufacturers go to create silence.

Just asking. Isn't run flats about keeping the tyre rims locked on to the wheel rim ?

The above foam thing is super simple idea. Not sure how if the puncture plugs will have issues plugging the holes properly though. How about sticking damping sheets

[Leoshashi]

Originally Posted by srishiva

How about sticking damping sheets

The regular damping sheets will not only be heavy but also won't be that flexible as say a foam.

Regards,
Shashi

[dark.knight]

Originally Posted by srishiva

Just asking. Isn't run flats about keeping the tyre rims locked on to the wheel rim ?

No, runflats are about having a very thick rubber base across the entire circumference+profile of the tyre, this enables stronger sidewalls, thicker skin of the tyre such that even in an extreme flat, the tyre doesn't dip too much since the capacity of air holding is much lower in such tyres due to thicker rubber, plus the surface of rubber to be burned out is much larger and can run about 100 miles after a flat, the only caveat here is that the entire tyre has to be changed after. No fixes possible.

Wacker Chemie, an example of a company that specializes in rubber/silicone production in three specifications, i.e liquous, solid, semi-solid, can give a good idea on how to do this tyre damping by impregnating the walls during the production process, so there is no question of it coming apart so easily. Alternatively, if foam must be used, it can be used in interlocking pieces within the tyre so that failure is less.

Having worked in plastics and rubber moulding, I can say that the R&D in them are far ahead of the time, what the world experiences today isnt 5%. Car reviewers are so ignorant that they knock on economy car's interiors and grimace and say this is "plastic", so cheap and nasty. All high end car interiors have plastic too, the only difference is if they are elastomer-like plastics (properties of rubber impregnated onto plastic). Since everything is basically a polymer (two monomers), the line between plastic and rubber are becoming thin in certain grades.

Let's look at the shoe industry, I've had a pair of running shoes from Adidas which has the polymer Adiprene which is a urethane elastomer of two grades, one in the upper foot region to absorb the landing and one in the heel to give a bounce. Works like a charm. If mainstream polymer research companies work with tyre makers its the end of these primitive neoprene rubbers so to speak (even the latest ones made with orange oil or silicone are antiquated).

The foam which is a polymer of the ONG industry as well, should be integrated at the production process, with no use of glue. Given some time even I might be able to work out a chemical chain to fuse the two depending on their composition.

[Vikki@Hyderabad]

Originally Posted by Leoshashi

When I was looking for alloys for my M800, I was excited about the reduction in unsprung weight the alloys will bring, over the stock rims. Infact, the commonly available Neos and Platis were actually lighter than the steel rim. But the MGA branded, Hindalco(Aura Wheels) manufactured alloys turned out to be heavier than the standard rims, and this was an eye opener. In fact it depends on the build, material used etc of the alloys. Same thing happened with my friend, whose Punto's stock rims were actually lighter than the Momos he had installed.

I always wondered if that could be the case and your experience proved it right, to whatever extent. This probably speaks to the manufacturers' understanding of the concept. I opt for alloys for their sturdiness. I've had a couple of experiences where a pothole bent the steel wheel out of shape. XUV 5OO, however, proved it otherwise with its badly designed alloys a couple of years ago.

I'd still opt for alloys though, like the ones that Ford or Tata provide.

[rideaholic]

I doubt if something will go drastically wrong by adding the foam inside the tyre. The worst could be that it could come loose and become an unbalanced mass but since the foam is light it should not drastically affect the tyre balance.

However to get the benefit we need to appreciate the product development process where multiple cae analysis and physical testing is carried out to ensure that the foam delivers the required output. If the foam is of the wrong density it may add to the noise rather than reduce it.

[Swajith]

IMHO I don't think it's an easy DIY stuff. It will definitely effect the tyre balance.

[Leoshashi]

Originally Posted by Swajith

IMHO I don't think it's an easy DIY stuff. It will definitely effect the tyre balance.

If the foam stays in place and doesn't move, how will that affect tyre balance in any way? Also what about the tyres which come with foam pre-installed, will they have a similar issue? If not then how will the DIY case be any different?

Regards,
Shashi