Lower pressure really does ride smoother

[faramir9]

My lady friend has back issues that acted up lately, and complained of being jolted around as we took a ride last month. To make things less bumpy, I lowered the tire pressure in my '05 Corolla from 36 psi to 31-32 psi. (Door jamb is 30.) Did not not expect much, but....

It really did make a difference in the ride. Much smoother. Enough that I could feel it---and the lady was very happy. Lesson learned.

I have always run a few psi over door jamb spec, for a bunch of reasons. Temps can drop quickly here, I like the slightly more responsive steering, (in a Corolla every little bit helps) and I will take whatever slight increase in mpg or treadlife I can get. I never minded the slightly firmer ride, which I always thought was over-stated anyway. Till now.

Will likely bump it up 1 or 2 psi in the late fall as it gets cold, but for now we are enjoying the smooth ride.

 

[CT8]

Who would have thunk it.

 

[Eddie]

I would never run a full 20% higher pressure for normal driving. In addition to discomfort, there is the safety factor of lost traction with the lower footprint.

 

[faramir9]

Originally Posted By: Eddie
I would never run a full 20% higher pressure for normal driving. In addition to discomfort, there is the safety factor of lost traction with the lower footprint.


That's a plausible argument, but check out some hyper-miler forums to see folks who disagree. I think the old de facto standard 30 psi used for compact/midsize family sedans up till a few years ago (CAFE) was designed mainly for ride comfort. SL tires do not hit full load carrying capacity till 35 psi. That's what I tended to use as a reference. Note that newer versions of models that used to spec 30 psi now spec 35 psi.

If you have time to kill, this is a fun site to play around: https://www.firestonecompleteautocare.com/tires/tire-pressure/

But running 1 psi over spec rather than 6 psi over sure does make a difference.

 

[AZjeff]

Originally Posted By: faramir9
Originally Posted By: Eddie
I would never run a full 20% higher pressure for normal driving. In addition to discomfort, there is the safety factor of lost traction with the lower footprint.


That's a plausible argument, but check out some hyper-miler forums to see folks who disagree.


Hypermilers are known to do unsafe things for a few tenths. 20% less contact patch is what it is (almost like 1 less tire on the road..). Always hope Capriracer stops by with some expert insight.

 

[JLTD]

Subscribed.

 

[faramir9]

20% less contact patch sounds scary. But take a look at that link to the Firestone air pressure guide.

Note that for the 2005 Corolla with 195/65R15 S-speed rated tires, the spec is 30 psi. For the 2014 Corolla with 195/65R15 S-speed rated tires, the spec is 35 psi. (a difference of 16.67%)

Wonder what changed over the course of nine years.

 

[OVERKILL]

Originally Posted By: faramir9
20% less contact patch sounds scary. But take a look at that link to the Firestone air pressure guide.

Note that for the 2005 Corolla with 195/65R15 S-speed rated tires, the spec is 30 psi. For the 2014 Corolla with 195/65R15 S-speed rated tires, the spec is 35 psi. (a difference of 16.67%)

Wonder what changed over the course of nine years.


Probably weight.

 

[Kira]

Eddie said, "I no run 20% higher pressure..."

OP's example (31-32 instead of 36) = 11% if you use 32.

Where did the 20% come from?



Also: "Leave radials soft enough to do their job" was the battle cry when they first came out. Remember??

 

[JimPghPA]

For someone with a bad back never replace the shocks with expensive shocks. Expensive shocks have a much stiffer ride. With a bad back is is best to not replace shocks, but if you have to replace them get the lowest cost shock available. Low cost shocks have a softer ride. They do not last as long but the trade off for a softer ride for someone who has a bad back is worth it.

Expensive shocks will make the car corner like a race car but will stiffen up the ride so that you feel every bump.

 

[ragtoplvr]

Originally Posted By: faramir9
20% less contact patch sounds scary. But take a look at that link to the Firestone air pressure guide.

Note that for the 2005 Corolla with 195/65R15 S-speed rated tires, the spec is 30 psi. For the 2014 Corolla with 195/65R15 S-speed rated tires, the spec is 35 psi. (a difference of 16.67%)

Wonder what changed over the course of nine years.

20% smaller contact patch does not equal 20% less traction, as the force on the tread is increased 20%. There are situations where traction can be increased, like rain, and cases where it can be decreased, like snow.

racing where an additional 1% traction is huge, and expensive is one thing. Normal driving is another.

Rod

 

[dbias]

My A4 recommends different pressures for up to 2 people, 35 front - 32 rear and 3 to 5 people 35 front 35 rear. The usual load is 1 person 95% of the time and the car handles quite differently with only 32 in the rear especially in the corners. It is smoother with only 32 in the rears for sure and gives somewhat of a slingshot effect coming out of curves.

 

[Nick1994]

Some vehicles are more sensitive to tire pressure, others not so much. I doubt I’d feel a difference with my Jeep.

I service my aunt’s cars, she had a 2013 VW Beetle TDI and said she noticed it was rough over bumps and cracks in the asphalt, she didn’t know I pumped the tires up a few pounds over the placard (which I usually do). I rode in the car and noticed it too. I lowered the pressure down to the spec and it was fine.

 

[Eddie]

Running 36 when the recommendation is 30 psig = 20% increase. I believe that manufactures are now recommending pressure that are a compromise that covers safety, wear and comfort. To go higher or lower more than a few percent, you are sacrificing one feature or another. Of course this probably doesn't apply to very special conditions like street racing or beach driving. )

 

[ET16]

Originally Posted By: faramir9
Originally Posted By: Eddie
I would never run a full 20% higher pressure for normal driving. In addition to discomfort, there is the safety factor of lost traction with the lower footprint.


That's a plausible argument, but check out some hyper-miler forums to see folks who disagree. I think the old de facto standard 30 psi used for compact/midsize family sedans up till a few years ago (CAFE) was designed mainly for ride comfort. SL tires do not hit full load carrying capacity till 35 psi. That's what I tended to use as a reference. Note that newer versions of models that used to spec 30 psi now spec 35 psi.

If you have time to kill, this is a fun site to play around: https://www.firestonecompleteautocare.com/tires/tire-pressure/

But running 1 psi over spec rather than 6 psi over sure does make a difference.


Curious.... That Firestone site is wrong for two out of three of my cars. And for the third, the information does not include optional pressures like the door jamb does.

 

[oil_film_movies]

Originally Posted By: OVERKILL
Originally Posted By: faramir9
20% less contact patch sounds scary. But take a look at that link to the Firestone air pressure guide. Note that for the 2005 Corolla with 195/65R15 S-speed rated tires, the spec is 30 psi. For the 2014 Corolla with 195/65R15 S-speed rated tires, the spec is 35 psi. (a difference of 16.67%) Wonder what changed over the course of nine years.
Probably weight.

Not "weight". Higher pressure means it corners better, and it also helps CAFE MPG averages. The Corolla has been evolving into something more sporty.

 

[FordBroncoVWJeta]

My Jetta specs 36PSI in the door. In the handbook it says something like for a more comfortable ride, with reduced gas mileage air to 33PSI.

 

[RooflessVW]

US pressures for my Phaeton were ridiculous: 39 front, 45 rear. Ride was brutal, even in the comfort setting.

The ROW Owners manual has a chart for pressures vs load. Set per the chart the ride was completely transformed. 35 front and 32 rear had it smooth as silk even with the suspension in sport.

 

[Colt]

Originally Posted By: faramir9
20% less contact patch sounds scary. But take a look at that link to the Firestone air pressure guide.

Note that for the 2005 Corolla with 195/65R15 S-speed rated tires, the spec is 30 psi. For the 2014 Corolla with 195/65R15 S-speed rated tires, the spec is 35 psi. (a difference of 16.67%)

Wonder what changed over the course of nine years.


The CAFE numbers.35 lbs may get a few tenths or more MPG rating.

 

[Rolla07]

I might bump to 33 PSI for my 07 when fully loaded but when I ran 35 PSI my wet traction decreased quite a bit. I also dont mind a stiffer ride. The biggest improvement i got was from going to 17 inch rims with lower profile tires. Tightened up cornering significantly. The stock 15s are like mush regardless of PSI. I usually keep them at 32 all around as the best for gas mileage,overall comfort, traction and treadwear. Did you ever notice that ur tires at 35-36 PSI wearing irregularly? Like wearing out in the middle more than the edges?