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Road noise - Tire inflation experiment

Discussion in 'Model 3: Driving Dynamics' started by m3tx, Aug 11, 2018.

  1. m3tx

    m3tx Member

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    I am bothered by road noise, I have seen here that some people have had success with lowering tire pressure.
    Mine were set at 45 psi.

    I did a quick experiment, using an iPhone decibel meter app, with iPhone placed on charging pad.
    I did the same stretch of road at 50mph, on autopilot, with tire pressure at 45 psi, then at 40 psi.

    To remove outliers, I discarded 10% of the loudest samples, and 10% of the lowest samples, and averaged the rest:

    45 psi: 68.1 db
    40 psi: 68.3 db

    I wish I would have had more time to make experiments at various speeds and average multiple tries and multiple phone placements, but the impression I get from this quick experiment is that lowering tire pressure doesn't seem to help with road noise.
     
    • Informative x 3
    • Helpful x 1
  2. TurboCJ

    TurboCJ Member

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    Which wheels do you have? My 18” Aeros are nice and quiet.
     
  3. m3tx

    m3tx Member

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    I have 18" Aeros
     
  4. bradhs

    bradhs Member

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    I'm curious if anyone has tried deadening sound materials.
     
  5. saltsman

    saltsman Member

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    But you don't have chipseal (aka, tar and pebble) roads like Texas does. OP also lives in Houston that is notorious for extremely worn concrete pavement. Both create tremendous road noise.
     
  6. chinnam3

    chinnam3 Member

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    The change depends on surface. On rougher surface I found considerable difference between 43/44 vs 39 PSI. Also, best way to read the values, keeping it close to ear. Next best is handrest.

    Also, not sure how good is iPhone's mic is esp in low frequency where we get lot of booming sound on rough patches.
     
  7. SomeJoe7777

    SomeJoe7777 Marginally-Known Member

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    The noise can be measured in many different ways. Some of those include A-weighting and C-weighting. A-weighting is by far the most common, and is adjusted to report a number that correlates well with the sound level perceived by the human ear. It's really only valid for frequencies in the speech range or higher that are relatively quiet and approach a single pure tone. Road noise definitely does not fall into this category.

    In addition, the microphone sensitivity and frequency response are highly important when performing this type of analysis. A microphone in a mobile device does not have the dynamic range or frequency response to be useful for this application.

    In short, while your numbers may not show any difference, those numbers are pretty much meaningless in terms of road noise.
     
    • Like x 1
  8. m3tx

    m3tx Member

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    So even though my human ear can't detect a difference and a noise meter can't, it is actually less noisy, got it...
    Well, y'all enjoy your less noisy tires that are as noisy to the human ear.
     
    • Funny x 1
  9. avesraggiana

    avesraggiana Member

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    There are whole threads about people doing this to their older, pre-2017 Model Ss, with noticeable results.

    I've not seen anything being done with newer Ss or Xs, probably because improvements were made in sound insulation.

    I've also heard that later production Model 3s saw improvements in sound deadening too, but I know next to nothing about Model 3s.
     
  10. cab

    cab Active Member

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    Exactly. Here is a video of one of those "quiet" Model 3s with the 18" wheels on a Texas freeway....oh and turn the volume up louder than you think it possibly is because...it's just that loud. As a comparison, it isn't much different than my 2013 Model S P85 on 19s. On smooth blacktop it (and my S) are dramatically more quiet. This is where Tesla continues to fall short. They have this nearly silent drive train but at speed road and wind noise are almost always the primary source of noise and they just don't deal with it well.

    https://photos.app.goo.gl/MFXzyctb6Qpc1gFP7

    Hopefully you guys can get to the video....
     
  11. cab

    cab Active Member

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    As an aside with regard to sound deadening, my results over the years have been pretty modest. If you were to pursue it on the model 3, I would probably recommend mass loaded vinyl in between the inside door panels and the door as a place to start like this:

    Door <-> thin layer of foam <-> mass loaded vinyl <-> door panel

    Most of the commercial sound deadener places have this or you can buy MLV on Amazon (cheaper). This is what you really need to BLOCK noise (vs. the "make my car look like an Apollo space capsule" with stick on foil backed deadener sheets....ok maybe a handful of these might be OK). Beyond that, the rear wheel wells are likely the next area of focus.

    The problem with noise is that ANY LITTLE OPENING lets in a ton of it. Try putting a fan on high or turn on a TV in a bedroom. Now stand in the hallway with the door open and start slowly closing the door. You will notice that the sounds doesn't diminish all that much until the door is almost entirely closed. In a car, it is so much worse as there are "paths" for the sound to come in all over the place. It doesn't help that Tesla chose to use frameless doors (as the the S and X) and they don't have things like triple door seals, etc.
     
  12. SomeJoe7777

    SomeJoe7777 Marginally-Known Member

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    That is not at all what I said.

    What I said was that your iPhone numbers don't tell you anything.
     
  13. Daniel in SD

    Daniel in SD Well-Known Member

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    I think an iPhone microphone is probably perfectly fine for doing A/B measurements. Obviously the software has to use the right weighting.

    reponse2-3-4-5.001-0011-1024x576.png
     
  14. buddhra

    buddhra Member

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    I finally got around to testing this myself with a bit more comprehensive method. I couldn't measure a difference in road noise, but the ride is better at 39psi vs 45psi.

     
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  15. webbah

    webbah Member

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    I run 38psi cold and it’s a noticeable difference to me. The tires also make a difference. I’m running Michelin Pilot Alpin PA4’s.
     
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  16. chinnam3

    chinnam3 Member

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    I have similar thoughts on road noise. Instead of trying to apply sound damper/insulation to fender wells and cabin, if we can address by reducing the transfer from suspension to unibody(structure), it will take care of road noise.

    Please do let us know your discoveries and anything you come up with to address this issue. I tried door seals, trunk liners etc, but those address some of the windnoise (very little in my case), but do not address road noise on rough roads. Its ear grating boomy sound on rough concrete roads that bothers more, not wind noise.

    Thanks
     
  17. bradhs

    bradhs Member

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    I upped the size of my tires (245/35ZR20's on stock rims in this case) which upped the weight handling which theoretically allowed me to lower tire pressure. I'm riding at 38 lbs and it seems quieter than my old set of tires. Totally unscientific since my previous tires were worn out and you'd expect to have less noise on new tires.
     
  18. Uncle Paul

    Uncle Paul Well-Known Member

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    Don't forget. As you lower your tire pressure you also lower your load rating.
    Handling is also tuned for the posted tire pressure.
     
  19. chinnam3

    chinnam3 Member

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    Thanks for sharing your experience. I do think if we switch over to softer compound tires, it will reduce some noise. But based on test above by buddhra, it seems Tire pressure alone did not make any difference in noise on the rougher roads. It is counter intuitive as ride becoming smoother on reducing the tire pressure, I assumed/felt that sound is also reduced. But Buddhra test proves that is not the case.

    I think lot of that noise being transferred via suspension mount points to frame.
     
  20. Big Dog

    Big Dog Active Member

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    I don't know enuf to opine on the most (or even a "lot") but some road noise is coming thru the glass roof. (My 4-door Jag had a thick pad under the headliner.) In fact, I think Elon even realizes the roof is a contributor as Tesla has applied for a patent for a new, quieter glass style.

    And yes, frameless windows don't help. In fact, the window noise will only get worse over time as the rubber seals start to wear down and become brittle as they age.
     

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