Soundproofing / Reducing Road Noise

[Excalibur]

I own a 1998 ST202 Celica. All Celicas I believe are quite bad for tyre and road surface noise.

Ive tried a few things and this is what has helped. Now my Celica is very quiet.

Ive done a lot here, but I think the main area is inside the wheel arches and around the rear shock pillars and boot.

You will need to wipe off as much dust as you can from the interior panels before you spray any underseal or stick on any soundproofing. In winter the panels may be wet, esp. the doors. A hairdryer will dry it out quickly, esp inside the wheel arches and shock holes.

Tyres - Get a quiet tyre to start with. Read brochures and go online to tyre reviews. UK tyre reviews are good. Look for a tyre that has specific design features to make it quiet. I use expensive Toyos T1R's for grip. $200NZ each but they are quiet. The Toyo C1S is their quietest tyre.

Dont go for bigger rims! - Previously I had 15" rims which were very quiet. I upgraded to a 16" Volk TE37 and they are much louder. 17" is louder again. I read that in the new Nissan 370Z which has 18" rims, there is no point turning on the stereo, because you cant hear it above the wheel noise.

Now lets get to the car body itself...

Wheel Arches These are the main culprit. esp on a cheap sports car where there is little, if any soundproofing. The best thing I did was to clean the plastic arch liners and then spray each of them with a 500ml can of underseal. At the top of the arch is a hole where the shock goes..this traps sound like a drum and reverberates it through the car. This is worse in the rear of the car and worse again in a coupe or hatchback where you have no boot. Clean it well and spray a few coats right up there. Dont worry about getting your springs covered in underseal I have also shoved pink batts (do you have these in OZ?), household insulation inside the front and rear guards. On the front arches I have unscrewed them and put a med density foam behind them

Boot - To save weight I have removed almost all my bootlining. But I have covered my entire boot with a special type of medium density, adhesive backed, silver faced and flame retardant foam. This is used on marine motors for soundproofing. There are better things im sure. Heavier is better I think like a harder rubber. If you have ever held that thin soundproofing you see glued to the car floors you will notice it is thin but heavy.

My car also has a large gap between the rear bumper and boot lining. I managed to shove a large piece of batts up there to stop exhaust noise. I have also painted a thick underseal on the inside of all my interior plastic linings.

I have stuck the foam all around my shock pillars and interior wheel arches.

Sides and Interior I have also put this foam under the seats, footwells and sides of the car. I have put a few batts in the side cavities. Its a good idea to stick foam under your dash, but make sure you carry a fire extinguisher in case you ever get a fire up there

Doors - These also reverberate like drums. Not that important, but it will help. I know there is a special soundproof sheeting you can buy that sticks on the inside of doors, but I would have found this very difficult to put on as my doors have a metal skin with only small holes to access the outer door skin. Once you or your panelbeater has worked out how to remove the interior lining* - I just sprayed the rubber underseal on the inside. Making sure I gave it a few good coats in the door centre and being careful not to spray it on the window winding track. While you're in there - clean out the bottom join of your doors and the 3 or 4 little drain holes to stop your doors from rusting

I have also taken off the scuff plates on my doorsills and sprayed expanding foam inside the small holes.

Engine Bay - If you have a noisy motor the foam I use is very good. I have partly stuck some on like a skirt behind the engine. I have a photo attached of my engine bay...You can see in the 2nd photo I have this foam stuck on my airbox. That is to stop air intake noise but also to keep my air intake cooler and help stop it heating up from the engine

Chassis / underbody - I have painted all the bare and exposed metal, esp. near the exhaust, wheels and spare tyre well with a thick underseal. There are a number of rectangular and hollow beams running down the chassis. Look for the holes in these and fill them with expanding foam. Im not sure how much this helps, but any gap helps to amplify sound and I have heard that they fill these beams professionaly on chassis's

Interior Lining Removal ST202 - This is fairly easy to remove on mine. 4 screws on the bottom, 6 screws on the panel. Lever out your window winder controls and pull out the plug. There may be other plugs, all a bit fiddly to get off. Lever out you tweeter speaker cover. The panel then lifts up to detach from the window sill, but it is still held by -

* a small plug which is for your door light

* Some fiddly little push through pins on the door end

Ive probably wrecked most of mine by just wrenching them out. Im sure they come out very easily if you can find out how. I havent really studied them. But I have just today found a short, fat stubby Allen key screw that fits in their perfectly! 5/16 x 1/4 I think. You will also need to peel or cut off the light plastic cover and tape this on again afterwards

Edited June 17, 2011 by Excalibur