Oh!... for a quiet ride!

[Wooster]

 

Hello all - I've a 2010 Prius T Spirit - with sunroof - and 195/65 tyres.  60k miles and a full Toyota dealer service history.  I've been 'blessed' with exceptional hearing.  (Or perhaps it should be 'cursed'!)  I'm a piano tuner by trade.   

My Prius is everything I want from a car and fairly quiet, but I wanted it even quieter.  I followed all the advice that was given by:  https://www.sounddeadenershowdown.com/vehicles/toyota-prius-4-door-hatchback-2010

It was brilliant information and reduced the tyre noise / road roar to sublime levels.  (65dB on a fast A road.)  I've also reduce the rear tyre pressures to 28psi - which has also helped.  However...

Although the tyre noise is reduced to almost zero, I've uncovered some sort of resonate 'boom'.  Probably because the tyre noise has been reduced so much, I'm (very much) aware of a 'thump' or 'boom' every time I drive over a road bump.  Any road bump produces a 'thump' from the back suspension.  It's as if someone is thumping the underside of the car with a rubber hammer.  It ruins an - otherwise - supremely quiet ride.

I took the car to a Toyota dealer who "tested" the suspension.  (I suspect they looked the rear suspension and gave everything a good shake - and nothing more.)

Am I resigned to this inherent noise from the suspension? 

Any suggestions anyone?

Kind regards - Andrew

 

[PeteB]

Presumably as you got the sunroof, you got the 15" wheels?

" cars ago I had a 2012 Gen T3 with 15" wheels, and when the original Bridgestones needed replacing I switched to Dunlop Sport BluResponse (Eco B Wet A 68 dB - 195/65R15 91 H)

The car was reasonable quiet before (except on poor surfaces) to my admittedly unsophisticated ears but after the swap the car was noticeably quieter.

My Gen 4 (also 15" rims) was quieter still (and had significantly more sound deadening material according to the launch blurb) but I didn't have it long enough to swap to the Dunlops, although I measures about 66 dB in the cabin no a fair (but not perfect) road surface I use to take comparative measurements.

I can't say I've noticed the thump over bumps to be excessive, but I believe my hearing is slightly diminished, but not enough to do anything about it.

In fact since switching to Hybrids some 17 years ago, I spend much more of my driving time with the audio system turned off because I just enjoy the tranquillity.  Prior to that, I just had to have music at all times while in the car.

[Wooster]

Yes, I have the 15" wheels.  (65 section tyres.)  I use Michelin CrossClimate tyres, as they are (supposed to be?) one of the quietest tyres available at 69dB

I'm sure the 65 section tyres help soften the 'thump' as there is more tyre wall to flex and absorb the impact.  But still, too much 'thump' is entering the cabin and I was seeking way to reduce it.  Any ideas will be gratefully received!

[TonyHSD]

Hi,

those thumps that we all experience at some point are due to suspension components and set ups, in many cases they are more prominent at lower outside temperatures, the shocks are getting stiffer and rubber bushes too. In German cars for example these issues are much better smothered, the reason why I can’t answer, financial or some other points that manufacturers are about, they know it best. I can give you an example with small VW Polo from 2015 is more refined over rough roads and speed bumps plus is better sound proof than Toyota Auris that is a class larger car, maybe Japanese roads are extremely smooth and they don’t need to set suspension on the softer side. Best is not to expect too much from our cars and just learn to live with those small imperfections, we are driving a Toyotas not a Bentley. Joke 😊

[Gerg]

Hi,

Just a few ideas spring to mind -

On our Auris the plastic chassis undertrays that run along the length of the car are prone to filling up with gravel and fine grit - on our car there was about 0.5 kilos of crud in each side when I looked (at 6 years and 60,000 miles).  When this is disturbed (bumps) it will make a noise against the undertray. I have removed these trays and washed them out, the car does seem more refined, although this could be my imagination.  There is no reason to remove these trays in normal servicing, as far as I know.

Or what about this obscure one:-  the front and rear bumpers are secured by a mixture of small bolts and plastic clips.  With mileage (general vibration), the plastic clips fret and become looser.  If the bumper suffers any impact then these clips will probably get looser still.  Perhaps your bumper is no longer securely connected to the body at all points, and has some small movement available?  (These clips are quite pathetic in my opinion and I am trying to replace them with something better.)  From underneath, the shape and size of the bumper might mean it is able to catch air if the body suddenly moves down or up, giving the noise you hear?

What about loose heat shields on the exhaust, i.e. rusted securing fasteners - especially given the age of the car.

I'd have suggested loose rear brake pads, but the sound doesn't fit, does it?

 

 

[Ten Ninety]

On 8/30/2019 at 10:51 PM, Wooster said:

I've also reduce the rear tyre pressures to 28psi - which has also helped.

Fair play to you for going all-in on the sound deadening work, but I think lowering tyre pressures to that level would be a step too far for me. Does it really have such a positive impact on road noise to make the significant negative effect on economy (and potentially tyre wear) worthwhile?  

[TonyHSD]

Tyres pressures should be exactly same as recommended no matter how soft or how hard is the tyre compound. Any large pressure difference up or down will contribute to higher noise levels , higher tyre wear and not proper handling if you drive on higher speeds or cornering fast., and to be honest tyres sizes and makes affect only slightly the car ride quality, all mostly is done by the suspension, and this is the reason why I didn’t change my 17” wheels to 16” looking for better comfort. Low profile tyres definitely make car ride more uncomfortable but if suspension is set up right these could be not that much noticeable. 

[PeteB]

Does depend on the suspension to some extent - I found he Gen 4 Prius (which had significantly improved chassis and suspension compared to previous generations) to be not too much different between 15" and 17" wheels, but on the Gen 3 they were like chalk and cheese.  I still specified 15" on my top spec Gen 4 (nice to have the choice) for lots of other reasons.

I wouldn't have tolerated the ride on 17", which is why I got the basic T3 model and had the Cruise Control switch fitted.   A lot of owners of Gen 3s with 17" rims also complained of rattles and squeaks, but I almost never saw these complaints from T3 owners and mine certainly didn't suffer.

[kithmo]

4 hours ago, TonyHSD said:

Tyres pressures should be exactly same as recommended no matter how soft or how hard is the tyre compound. Any large pressure difference up or down will contribute to higher noise levels , higher tyre wear and not proper handling if you drive on higher speeds or cornering fast., and to be honest tyres sizes and makes affect only slightly the car ride quality, all mostly is done by the suspension, and this is the reason why I didn’t change my 17” wheels to 16” looking for better comfort. Low profile tyres definitely make car ride more uncomfortable but if suspension is set up right these could be not that much noticeable. 

In my experience, very high tyre pressures will create less road noise, as less of the tyre is in contact with the road, but it will create more noise from bumps and potholes etc. Low pressures will increase noise as the tyre tends to flap about (a bit like when you have a puncture) but less noise from bumps. Ride will be improved by lowering pressures, as the softer, flexing tyre sidewalls take up the shocks from bumps and potholes, but cornering will be severely compromised. Of course all the other things you mention are correct, poor handling excessive tyre wear, as well as extended braking distances too, although handling and cornering at speed are not things that apply to us Prius drivers really. 😉

[Seamaster73]

6 hours ago, TonyHSD said:

 to be honest tyres sizes and makes affect only slightly the car ride quality, all mostly is done by the suspension, and this is the reason why I didn’t change my 17” wheels to 16” looking for better comfort. Low profile tyres definitely make car ride more uncomfortable but if suspension is set up right these could be not that much noticeable. 

Not my experience. I’ve found smaller wheels make a huge difference to ride quality, not least because most car makers these days choose stiffer spring settings in the mistaken belief that buyers prefer a “sportier” (read harder) ride over a more compliant/comfortable one. As a result I always spec the smallest possible wheels on any new car I order, which is simplest antidote to it.

The massive wheel/skinny tyre combinations standard on most modern cars make no sense whatsoever. Drive a mid-range family car of twenty years ago with small wheels and fat tyres and you’ll be astonished at the degree to which we’ve become acclimated to rotten ride quality.

[QuantumFireball]

On 8/31/2019 at 3:34 PM, Wooster said:

I use Michelin CrossClimate tyres, as they are (supposed to be?) one of the quietest tyres available at 69dB

Something to note is the EU tyre label noise measurements are for external noise, from the perspective of noise pollution. Lower noise ratings aren't necessarily better for those inside the car. Might be worth trying different tyres.

[Ten Ninety]

2 hours ago, QuantumFireball said:

Something to note is the EU tyre label noise measurements are for external noise, from the perspective of noise pollution. Lower noise ratings aren't necessarily better for those inside the car. Might be worth trying different tyres.

Absolutely, as I have discovered to my cost enough times to ignore the ratings completely now.

23 hours ago, Seamaster73 said:

Not my experience. I’ve found smaller wheels make a huge difference to ride quality, not least because most car makers these days choose stiffer spring settings in the mistaken belief that buyers prefer a “sportier” (read harder) ride over a more compliant/comfortable one. As a result I always spec the smallest possible wheels on any new car I order, which is simplest antidote to it.

The massive wheel/skinny tyre combinations standard on most modern cars make no sense whatsoever. Drive a mid-range family car of twenty years ago with small wheels and fat tyres and you’ll be astonished at the degree to which we’ve become acclimated to rotten ride quality.

I do agree with the stupidity of oversized wheels and despair at how tolerant we have become of poor ride. Like you, I will always choose smaller wheels where possible. However, I think tyre choice can have as much of an effect as wheel size.

On a previous car, swapping from 16s to 15s transformed the ride, but that was also swapping from hard summer sports tyres to soft winter tyres. When I changed from 17s to 15s on my Gen3 I went from Michelin Primacy to Goodyear EfficientGrip, both summer tyres. The difference wasn't actually as great as I thought it would be, despite the Goodyears' terrible soft sidewalls. And because the 'EfficientGrips' were anything but - they didn't grip and they weren't efficient - I had to over-inflate them to avoid cornering like a Rowntrees jelly, and to get close to the fuel economy I was getting on 17s. As a result, it probably ended up less comfortable on 15s than on 17s. If I had chosen better tyres, I'm sure the result would have been different.

[Wooster]

Hello all

Many, many thanks for your numerous comments and feedback.   I'm slightly overwhelmed by the number of replies.  Thank you.  There have been many ideas and I'll try to address them all:

I have 15" rims and 65 section tyres.  It was a deliberate decision to buy a car with this equipment as I believed it to be the quietest option.   I'm still convinced by the idea that the larger the tyre profile, the quieter the ride.  However, I had Michelin Cross Climate tyres fitted when I was mainly concerned about "tyre roar".  I accept that the EU noise level is a "drive by" level but I assumed the quieter the "drive by" noise, the quieter it would be for the cabin occupants.  What else is there to go on?  Since then (having insulated my car from tyre roar) I'm more concerned with the 'softness' of the side walls.  I have no idea if the Michelin Cross Climate are good in this respect.  When the tyres need replacing I'll consider another make / model and I would welcome suggestions! 

An interesting side note:  Thin sidewall tyres were originally made for performance cars that needed massive brakes.

Massive discs needed larger wheels to accommodate them.  Larger wheels needed smaller side wall tyres to fit the car.  But - now - skinny side walls seem to be a style statement.  Whenever I see these skinny tyres on a car I think:  "Pimp my Ride!"

The comment about the VW Polo having a more refined ride was fascinating.  It gave me a lot to think about.  I had a (recent) ride as a passenger in a (made in Germany) 2016 Ford Focus.  The lack of tyre roar and "road thump" was staggering - compared to my Prius.  More later....

The under trays / bumpers are not the problem nor are exhaust shields etc.  There simply isn't enough mass in them to produce the deep 'thump' that I hear.  They would rattle as opposed to 'thump' .  However, it was a great idea!  Thank you!

I have put some more air in my tyres.  However, not to the recommended level.  Looking at other similar cars (BMW, Vauxhall, Ford, Hyundai and other Toyotas) show the rear tyre pressures are set at 30psi to 32psi.  I think that the rear tyre pressures on the Prius (35 psi) are to aid a lower fuel consumption figure.  Mine are set to 32psi but I'll increase them to 35psi when "sustained high speed driving" is anticipated.  Thanks for your concern.

Don't ask me why, but I 'bumped' the middle of the doors on my Prius with the flat of my hand.  I heard a deep "thump" and immediately thought "that's it!" .  It (seemed to be) the same deep 'thump' I hear when driving.  I applied the same 'bump' test to the doors on my friend's Ford Focus.  Absolutely nothing.  No 'thump' what-so-ever!  I wondered if the Prius had super thin (weight saving, fuel saving) doors compared to other cars - Ford Focus, VW Polo etc.  I removed the interior trim panels on my Prius but could see no way of giving them any extra support - as the window glass (obviously) slides down into the middle of the door.  There is a thin, folded piece of steel that runs across the outer door skin and is attached to the door skin by thin rubber 'splodges'.  I'm guessing that it is there to give some sort of rigidly to the door.  However, it is so thin and light weight (you could probably bend it in your hands) it seems to do (to me) almost nothing. 

When I "thumped" the middle of the doors on my Prius I was surprised how much the sheet steel actually moved.  I'm guessing , but I wonder, if the 'thump' I hear is the door resonating with the road irregularities and moving the air inside the Prius cabin.  If this is what I'm hearing, there is nothing I can do.  The doors are thin and they resonate.  End of story.  Do any of your doors move in the same way - and give such a deep 'thump'? 

[QuantumFireball]

The doors are usually the first port of call for adding sound insulation, as it's pretty much non-existent on the Gen 3 Prius doors. If you remove the door cards on these other cars you'll probably find a lot of foam and stuff.

[kithmo]

The larger and flatter the door is the more resonant noise you'll get too. Sound deadening pads on the inside of the door skin will help, but will also add weight.

[Ten Ninety]

9 hours ago, Wooster said:

 I accept that the EU noise level is a "drive by" level but I assumed the quieter the "drive by" noise, the quieter it would be for the cabin occupants.  What else is there to go on?

That's a very reasonable assumption, and one I am sure most people would make. I certainly did once, but subsequent experience across a range of tyre purchases showed no relationship between the noise rating and cabin noise. It has been suggested that some tyre manufacturers may even design tread patterns that project more noise into the wheel well (and thus into the cabin) in order to secure a lower external drive-by rating. Whatever the case, I'd be inclined to treat the noise ratings in the same way as the contemptible 'economy' ratings which have zero bearing whatsoever on actual fuel economy i.e. ignore them.

Sadly with the number of variables involved there simply isn't any reliable indicator of how much cabin noise a particular tyre will generate on a particular car, other than buying four and fitting them! 

[Wooster]

15 hours ago, Ten Ninety said:

It has been suggested that some tyre manufacturers may even design tread patterns that project more noise into the wheel well (and thus into the cabin) in order to secure a lower external drive-by rating.

A point of view that hadn't occurred to me! 

22 hours ago, kithmo said:

Sound deadening pads on the inside of the door skin will help

I have already fitted heavy weight pads to all the door skins when I gave the whole car the sounddeadenershowdown treatment.  (See pic)  They stop the door panels from sounding like a tin can when tapped, but they don't seem to effect the deep 'thump' noise.  I've added more heavy pads and then removed them - all to no effect.

I guess I'm just going to have to live with the deep 'thumps' and accept it as part of the car's characteristics! 

[TonyHSD]

That’s interesting. Door insolation will not help with thumps, thy come from the suspension and than travel through the body. Suspension is vital and the most important for smoothening the road imperfection,

1: shock

2: springs

and 3: all rubber bushes. At at the end it’s all the materials used to build the car, body and door insulation, interior materials too. It’s a complex issue to make a car really quiet and comfortable. 

There are some interesting videos on YouTube for car manufacturers how they adjust shocks to get best possible performance and comfort, here is the video at about minutes 25 afterwards if you don’t want to watch full but trust me it’s so fascinating. 

Different makes invest in different parts of development, some has been looking for a comfort ride and sport style driving others created the best drive trains that are efficient and reliable.  What everyone says now is that the new Corolla and Priuses are way better than before is a proof of what we all experience with ours older models, so at the end Toyota will catch up with the rest. European car makes been better sound proofed  for a long time, more solid feel, but unreliable and uneconomic to maintain and repair. 

Regards 

[Joseph D]

On 9/5/2019 at 8:40 PM, Wooster said:

I think that the rear tyre pressures on the Prius (35 psi) are to aid a lower fuel consumption figure.  Mine are set to 32psi

No, actually, that is the front tyre pressure spec.  The rear is 33 PSI, so you are only 1 PSI short.  I have noticed running lower pressure affects MPG much more negatively than higher pressures provides benefit.  So, it would pay to keep a weekly eye on your tyre pressures if running to manufacturer's spec.

 

Some other thoughts, did you apply sound deadening to the entire spare wheel well?  If not, I understand that applying sound deadening to this area really helps quieten the noise emanating from the rear of the car.

What, if anything, do you carry in the under floor tray?  Could this be bouncing around causing thimping noises?  Hopefully you have already explored these ideas, but I thought I'd mention it anyway as I didn't read that it had been considered.

[Wooster]

"The rear is 33 PSI, so you are only 1 PSI short".  Sorry - you are NOT correct.  My 65 section tyres are spec'd at 35psi front, 36 psi back.  (See photo.)  The user manual and the door jam info confirm this.  It's the 45 section tyres that should have a32psi.

Yes, the rear hatch and the rear tyre-well received the same attention as the rest of the car.  Several heavy weight vibration pads, followed by 10mm of closed cell foam (CCF) and Mass Loaded Vinyl (MLV) over the whole lot.  In addition, I've installed a MLV / CCF / MLV sandwich mat which covers the (flat floor) whole boot area. 

The only thing things in the under-floor area are light weight and on no concern.  A space blanket, plastic mac',  a high Viz jacket etc. 

TonyHSD:  The Porsche video was (as you suggested) fascinating.  However, the Porsche is (probably) worth 10+ times what my 2010 Prius is worth....  It would be (equally) fascinating to see a comparable Toyota video!

I totally accept the springs, shock absorbers and bushing will have a major effect on the perceived ride quality.  However, there is little I can do about these.  I wish there was!  (Suggestions very welcome!) 

It never occurred to me that the tyre manufactures would spoil the cabin noise to reduce the 'drive by' noise level!  If anyone has a suggestion for the quietest "in cabin" tyres I'd be grateful to hear from you!

Many, many thanks for your contributions.  I'll always be grateful for any ideas, but I've a feeling I'm going to have to accept the 'bass drum' noise as a cost of Toyota 's reliability and low cost maintenance.   Hey-ho!

[wass]

The subject of sound deadening amuses me. The more quiet the manufacturers  design their cars, the more quiet somebody wants them to be. I imagine a world where vehicles make no noise at all . This isnt so far away as you may imagine. Most cars these days make no noise at all when parked. The next issue then pesumably presents itself , how to silence the almost deafening breathing of the human passengers and the terrible sounds their digestive systems make. What happens to the owners when they open the door to leave their sanctuary of silence only to encounter the deafening din of bird song?

 Sound is movement of air. How does one live without movement of air? There are enough profoundly deaf persons in this world  who would desire the world to be more noisey. Complaining about noise from a car which uses a series of controlled explosions to propel itself through air along surfaces which are about as smooth as  2 grit abrasive seems  pointless to me.

[kithmo]

Very deep Geof 😊

 

[Wooster]

1 hour ago, wass said:

The subject of sound deadening amuses me....

I understand what you say but 75dB for 6 hours on a motorway gives me a headache for a few hours - and tinnitus for days afterwards. It's not amusing! Cars might be silent when not moving, but dragging tyres over (say) a ribbed concrete surface at 60mph certainly swamps any noise of passengers breathing.  I'm not remotely wishing for silence, just a cabin noise level that doesn't approach the (80dB) lower limit where (if I was at work) my employer would need to supply ear defenders.

[Ten Ninety]

1 hour ago, wass said:

Complaining about noise from a car which uses a series of controlled explosions to propel itself through air along surfaces which are about as smooth as  2 grit abrasive seems  pointless to me.

It's not pointless if you suffer from tinnitus (as a surprisingly large proportion of this forum appear to), because excessive continual roar can be a real impediment to the enjoyment of a vehicle. 

It's also not pointless when one of the greatest assets of our hybrid cars is that for a significant proportion of the time, they don't use a series of controlled explosions to propel themselves. Addressing road noise then becomes far more important than it would be when you've got a raucous diesel tractoring away up front. 

[TonyHSD]

Toyota are well known for best hybrid drivetrains, but also known for a noisy cabins. Cars that are way quieter are VW Golf, Ford Focus, Volvo, Vauxhall Astra, even Corsa, etc  I have access to many cars and the common between all above is that they have extra sound proof rubber strips around the door seals, actually the door gap is filled, this is major road roar way inside the passenger compartment. Toyota has similar on the front bonnet for aerodynamic purpose too. My car not only missing that but sometimes when outside is very windy and I am taking rest with all doors and windows closed I can feel some wind blowing through the door cards near the door opening handles, so there is another point to look for when looking to make the car quiet 🤫.