Advance Sport Tyre Pressures

[Pine]

I am finding the ride in my Jazz Sport a bit firmer than I would like on the not very smooth rural roads near where I live.  The recommended tyre pressures are F35/R33 psi.  I was wondering if anyone has dropped the pressures slightly in an attempt to get a smoother ride. 

[Bristol_Crosstar]

It won't do your tyres any good if they're under-inflated, also there could be safety issues. I think most modern cars struggle at low speeds on roads full of pot-holes, the Sport's suspension is great on motorways

[Nicksey]

Sport variants tend to have stiffer suspension, so always seem harsher over the bumps.
What tyres are on it?

[Pine]

I'm not sure what tyres are on there, I'll have a look next time I check them.  I just set them to the recommended pressures.  I've done 405 miles since filling up and the dash is showing 71.2 mpg for this tank full.  most of my journeys are on rural roads with occasional trips to the city.  Some motorway driving but not on this tank full.

[coldstart]

I am finding the ride in my Jazz Sport a bit firmer than I would like on the not very smooth rural roads near where I live.  The recommended tyre pressures are F35/R33 psi.  I was wondering if anyone has dropped the pressures slightly in an attempt to get a smoother ride.

For what it might be worth: These pressures (F35/R33 psi) are the same as on my Jazz Advance for normal load and speeds.
Please have a look at the "Tyre noise question" - thread as another tyre brand might give you a more comfortable ride.

[ahavoja]

I did try dropping the rear pressures to 25 psi, while keeping front pressures at the default 35 psi. (I would only do this if you don't have rear passengers and no heavy cargo in the boot.) This made the rear of the car feel almost as soft over some bumps as the front. With the default pressures the rear felt harder over the bumps than the front.

I was concerned would this cause the rear tyres to heat up more. So after some city driving, I measured the tyre temperatures with an infrared thermometer. The front tyres were still 1 °C warmer than the rears, although the rear pressures were only 25 psi. This must be because the front tyres have much more weight on them than the rears.

[Lord Voltermore]

As stated the problem is the stiffer springs, to give 'sportier' handling. It might give some improvement on a motorway and will be less of an issue on smooth roads. 

Back in the last century it was common for recommended tyre pressures  to be in the upper 20's psi
sometimes with the option to raise this for 'high speeds ' or a heavy load.

I dont think tyre technology has changed that much. Todays higher pressures are primarily to improve fuel consumption  .   Sometimes suspension design is tuned to improve ride at this pressure, but maybe not with 'sports' suspension.


I am reluctant to suggest trying a lower pressure  , as there may be  safety issues, or higher fuel consumption.  You could argue that many people neglect to check their tyre pressures anyway   which naturally drop due to cold weather, natural permeation through rubber, punctures leaks  etc, .They will often be inadvertently  running well below recommended pressure for most of their miles. Usually without serious issues apart from increased fuel consumption.

But if you do  experiment and try  a slightly lower pressure its probably a good idea to ensure you check your tyre pressures , and tyre condition, more often than before.  If you start off with lower pressures  they could reach dangerously low pressures that much sooner.
 If you do find a lower pressure is satisfactory for local trips maybe increase the pressures again for a long, fast ,motorway trip.

[Bristol_Crosstar]

Sport variants tend to have stiffer suspension, so always seem harsher over the bumps.
What tyres are on it?

The tyres on mine are Yokohama 185/55R 16H, not sure if this is the same as other Jazz models?

[emp]

mine (Jazz Crosstar 2026) came new with Dunlop Enasave EC300+  Recommended tire pressure 2.4 Bar (front) 2.3 Bar (back)

[Pine]

Checked my tyres this morning.  Yokohama BluEarth 185/55 R16 87H.  Set them to the recommended 2.4/2.3 Bar.  I know from previous experience at this setting I can feeling my insides shaking on rough roads, something I didn't get in my last car - Toyota Corolla.

[Nicksey]

Was your Corolla a 'sport' variant?

[Pine]

a standard 2020 Toyota Corolla Design (middle of the range model).

[Nicksey]

So, the Corolla was a standard mid range family car, designed for comfort...

whereas the Jazz is a 'sport' variant, with stiffer suspension designed for tight cornering and faster acceleration.

Its the difference between an old Fiesta 1.2L and a Fiesta XR2i... and you never did long comfortable journeys in the latter 

Hence the more uncomfortable ride.

[sebastiand]

I drive over 60 speed bumps every day and some potholes. And I find the Jazz elegance (R15 wheels) suspension extremely soft on the comfort side. Especially on potholes, here is where I noticed the extra softness.
My 2014 Outlander feels a lot harder on potholes.

However, I find the Jazz more unstable when driving at 100-130km/h with 20+km/h wind, I always assumed this was because of the steering which is very soft / sensitive. But I wonder if this is because of the softer/comfortable suspension. Could also be body and weight.

I think in this case, like others stated the sport variant more aggressive suspension is the reason is harsher on potholes. But that is also an improvement in more aggressive driving.

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