I've been researching tire noise over the last year. people say the run flats are so loud and the non run flats are quiet.. I've found that the older the tire, the noisier it gets.. I've rode in cars with Firehawk RFT.. and Michelin sports, and Z06 super tires... MY EMT's have 43,000 miles on them and they are noisy.. I have two friends with HawksRFT's.. when they were new they were quiet compaired to their original EMT's... Now that they have over 20,000 miles on them , they are as noisy as their old EMT's I drove a new C5 and a Z06 and both cars had noticabley less noise than my car.. but both cars had noise.. and about the same amount.. If you ever listen to other passenger cars tires as they pass with your window down you can easily hear their tire noise.. they are just insulted from it better than we are..
So rather than rambling on let me get to the point..
passenger cars are metal with a metal wheel wells and those wheel wells are in the trunk and the tires are more than three feet away from the driver.. in our cars the wheel well is fiberglass and it acts like a drum to resonate tire noise.. and the wheel well is less than a foot from our ear and it is not in an insulated trunk.. so my contention is that it isnt the tires that are the culprit.. it the wheels wells and closeness . OK here my idea.. 15 months ago I added breathless performance rear brake ducts.. when I took out the inner wheel wells I noiced the area behind the inner wheel wells was hollow.. all the way up through the rocker panels.. and between the inner wheel well and the trunk.. the rockers are hollow and act like a trumpet horn.. they are open 6 X 6 inches as it deminishes toward the front of the car.. there is anywhere from 1 in. to three inches between the inner wheel wells and the truck compartment.. My idea is to stuff fiberglass insulation into the rockers and to the area between the inner wheel wells and the trunk compartment.. this should quiet this area considerably.. also it shoud help to insulate against heat in the summer..and it is cheap.. compaired to Dynomat super at 40 dollars for two sq feet.. I think the fiberflass has a better insulation factor than the dynomat and for the price of a roll of the pink stuff it is worth a try.. I would like to hear any thoughts.. I think a 20 dollar roll of insulation could do the whole back end of a C5. The inner wheel wells come out with 6 bolts..


[Modified by Evil-Twin, 6:08 PM 3/22/2002]

 

Doesn't water drain off there from the rear hatch area? Seems to me that there is a hole just behind the top of the rear fender behind the door jamb to allow any water in the channel between the rear hatch and the fender to run off.

 

the drain doesn't not pose a problem to this. Ive been all over the inside of the car between the wheel wells and the inner skin of the car.../// Im going to do this as soon as I get a couple of warm days together.. the wheel wells can be removed in a half hour.. both sides.. for 20 dollars it cant hurt..
My only question would be do I want to use the pain fiberglass insulation Like R-12.. or do I want to use the stuff with the silver backing...which may be better for heat .. but am alittle concerned about the noise from the foil ..

 

Sounds like you've given this issue a lot of thought. I too have noodled on this for awhile and generally agree with your concept. The only problem that comes to mind for me on the fiberglass thing though is the issue of water and/or moisture generally. Fiberglass (of the insulation type) is like a sponge and takes a long time to dry. Even if not exposed directly to water it can absorb a fair amount of moisture from the atmosphere, say on rainy days, for example.
Some may say, well the car's made of fiberglass and/or other synthetic material and won't rust. That's true, but what about the frame, fuel lines, brake lines, metal retainers, clips etc? Also, is there the potential for mold or mildew smell?
I've used Dynamat inside the rear, beneath the carpeting, with some success, but I'd like to work on the noise thing a bit more. I'm thinking of jacking up the car, removing the rear wheels, cleaning the wheel housings then spraying them with rubberized undercoating. Maybe a couple of coats. This might also work well in some of the areas in or behind the rocker panel areas that you spoke of as well. :D

 

I appreciate all these thoughts.. everyone has good ideas.. I actually think Ive cracked the tires noise issue... I dont think it is specifiacally the run flats... your idea adds some more to the mix..... MY wheels wells are spotless...you could eat off them.. but how about this..you cut out the fiberglass insulation then spray it with the ruberized undercoating...this will also act as a further noise reducer.. spray the panels before you put them in... they will still be plyable..and they should act as a noise buffer.. with the ruberized spray..I also thought about using that stuff that looks like an egg carton...is is foam.. and is used for softening beds.. like a matress pad.. but then agai you have the sponge effect.. for me I dont ecpect to get cuaght in ther rain too much...but your idea addds a measure of waterproofing..

 

Yeah, the water thing always bothers me. That's why I keep leaves off for example. When they wind up in hidden areas they become little hidden sponges when it rains.
Me having an FRC has made me even more cognizant of the noise thingey. The Dyna-Mat and the addition of a rear separator panel has helped a lot though. Also, the Firestones didn't hurt either.
I think we're both on the right track in focusing on the wheel housing/ radiated noise theory as well as looking for other possible areas. :cheers:

 

Was just wondering if anyone has looked into using technology that is already exists, namely that of generating a noise of the general frequency produced by the tires inside the car and played back 180 degrees out of phase with the noise so as to damp the noise.

I'm not up to speed on the technique, but I think the above is generally accurate. Someone on here can give is more detailed information and maybe advise if this is practical in our situation.

Evil-Twin, keep us aprised of you efforts.

Good luck.
Mark

 

You can find Dynamat Xtreme cheap from bulk wholesalers on the Net.

1 Box would cover your wheel wells and that's where most of the noise comes from. Ez to access after you pull the carpet too. A 2nd box and you should be in great shape.

Just try 1 box on the wells for now. Worked AWESOME for me. You should be able to get a triangle box for $25-30 on the net.

 

You may want to try DynaLiner ... it is a 1/4 thick pad simiar to that of carpet padding .. I put some over my wheel wells , had to use a spray adhesive ... but it worked well ...

if you go the DynaMat Exteme route ... get "Brown" Bread ... it is much cheaper ... and you could just layer it ...

 

The idea I have is taken from the way I have seen items packed for shipment. They take something like small plastic garbage bags and squirt expanding foam insulation into them and then quickly pack it around the object before the foam expands too much and hardens. It takes a very snug fit to the object yet it can be peeled away without damage to the item because of the plastic bags. You could probably get away with using several small bags just to make it easy to work with. The canned foam insulation can be obtained from Lowes or Home Depot.

 

On a side noter - Being a C4 (Future C5, C6) owner i would not know the answer to a question i have. Is the coupe quieter the the FRC?

 

I was going to suggest the expanding foam, but Nekbyter beat me to it. I know a lot of high end cars actually have parts of the frame filled with expanding foam. It deadens noise, and keep things from moving (and hence creaking). I think it's a better sound deadener than fiberglass. Actually I've been doing some research, and from what I've read, fiberglass isn't that good for sound insulation. Great for heat, but not so great for sound. But for the cost of that stuff, there's no harm in trying. It's light too. The dynamat will go a ways toward reducing the drum effect, because that is what it does best. You may want to consider trying that in addition to the fiberglass. If you really want to get serious, just use extremeliner from dynamat. I think that will solve all the problems.

Scott

 

Personally, I look for porous roads which will maximize my tire noise -- which drowns out the ambient noise from the passenger seat immediately following my C5 smoking a Mustang GT or ricer. :lol: :lol:

 

All excellent techniques to ponder. But a larger question has never been answered BY ANYONE. Why hasn't a noise level test ever been designed/conducted by one of the major tire vendors on this subject. They conduct all sorts of other tests and assign a STAR rating. My point is I've been in C5 with high mileage Firestones and they are as noisy as high mileage GY's. I have never seen a test made between tires with the same mileage. Replacing tires that are old and worn with brand new tires will always produce lower noise levels.

How about it Tire Rack?

Tom
USAF Retired


[Modified by AFVETTE, 9:31 AM 3/23/2002]

 

So if you drill a small hole in the wheel well and start squirting the foam inside, will that work? I like the foam idea.

 

I've given thought to the "expanding foam" that is sprayed in to void areas too. The only thing I'm a bit concerned about is the "squeek, squeek" factor of styrofoam over time. :)


[Modified by Tx99FRC, 1:38 PM 3/24/2002]

 

just take your tires to a shop that has a tire lathe and have them trued on the rims. this will stop the noise because the noise is caused by the uneven wear of the tread blocks. :chevy

 

I don't think it'll squeak. That stuff isn't really like styrofoam. It's harder, and I believe it sticks to the surfaces that it touches pretty well. I also know that you have to be a little bit careful with it. I've heard of people buckling panels, and breaking spot welds by putting in too much of the stuff, and not leaving anywhere for it to expand to. From what I'm told though, the squeaking isn't a factor. Lexus and others use expanding foam to eliminate squeaks.

Scott

 

If you use expanding foam be sure to get "automotive" foam as the "construction" grade is different. Motorcyclists have used foam for years to stop resonance in handle bars, etc. and make this point.

As for "active" electronic deadening... This is a good choice if someone works out the electronics. Andy Green, driver of Nobles' current Land Speed Record jet called the active sound deadener activator his "Hero" switch, since it worked so well! Where's our EEs on the Forum, hum?

 

Good thread! I can say without hesitation when I switched from my almost new Good Year EMTs (90% tread left in front, 80% in rear) there was a marked improvement in noise reduction and also a smoother ride. Just wish I had taken my Radio Shack dB meter with me to measure the difference. I have absolutely no aftermarket acoustic noise reduction in my Hardtop. I'm thinking of the Ecklers $40 foam partition or making one out of MDF, thanks to Forum member cwhitpan who posted a procedure and template. http://forums.corvetteforum.com/zerothread?id=246264 In another thread DallasC5 has a slick partition with built in twin subwoofers, but for my purposes I don't want to give up all that space. http://forums.corvetteforum.com/zerothread?id=135928 A much thinner one housing a single 8" sub would fit the bill for me.