Tire pressure thoughts

pmckechnie

Registered Member
230
13
18
Matthews, NC
Genesis Model Type
Genesis G80
I have a 2018 G80 and love it. It is quiet and smooth. I took it to the dealer for a map update and it didn't go well. It now has NO GPS. Well I have had a courtesy car for over a week now. It is also a 2018 G80 like mine. Same engine, both RWD, both have Mich tires. I noticed that the courtesy car seemed quieter on the road and smoother over irregularities in the road. The only reason I could come up with is I have always run 33 psi cold tire pressure. The courtesy car has 28 psi cold tire pressure. Now my question.
I also have a 84 Mercedes 500SEL that calls for 28 psi cold. Now I know it has different tire size than the G80 but do you think it would hurt to run 28 in my G80. I know that it may loose a little MPG and possibly some high speed handling. It could cause more tire ware on the outside edges. I can live with these issues to gain the quietness and smoothness.
What are your thoughts?
 

EdP

Supporting Member
SUPPORTING MEMBER
SUSTAINING MEMBER
2,665
464
83
CT
Genesis Model Type
Genesis G80
You can probably get away with it in NC, but I'd not try going that low in a cold state. When the temperature gets really low, so does tire pressure and it sets off the warning.
You already listed the potential problems of low pressure and yes, there is a cost to it. Another poster mentioned the same thing with a dealer loaner. I wonder if dealers do it to give a more plush ride to perspective buyers taking a demo ride.

The government mandated pressure warnings to save on energy from under inflated tires so watch out that Greenpeace is not following you. FWIW, I run 34 pounds. I don't want to compromise handling.
 

Mark_888

Registered Member
13,335
121
63
Genesis Model Type
1G Genesis Sedan (2009-2014)
The recommended tire pressure is set in conjunction with various testing for handling, braking, rollover tendency, etc for that specific car and its suspension. Lowering it to below the recommended value will adversely affect those characteristics. In addition, it would likely adversely affect the life of the tire.

If you do run your tires a 5 PSI below recommendations, I would not advertise that fact even to friends and family, since it could back to haunt you in a lawsuit over a traffic accident.
 

JimInNashville

Registered Member
74
1
6
Reducing tire pressure to 28 in that vehicle is not wise at all. You may experience some additional smoothness, but you'll hear a lot of squealing on sharp turns or in parkades, your braking distance will be increased and your cornering and handling decreased. If anything, run them at 36 instead of the recommended 33.

That said, I want to emphasize that Genesis quality control for NVH issues is not great. I had two identical 2015 Genesis 3.8 HTRAC sedans, and the first one was much quieter on concrete roads than the second one. I can't get Hyundai to do anything about it (yet).
______________________________
 

pmckechnie

Registered Member
230
13
18
Matthews, NC
Genesis Model Type
Genesis G80
Just to find out, I set my tire pressure to 28 psi for about 500 miles. Sure enough, it was smoother and quieter on rough roads.
Otherwise, I could not tell any difference in the way it handled.
I then raised the pressure to 36 psi. I can feel the bad roads more, but no difference in the smooth roads.
We are going on a 3000 mile (+/-)trip this month and will see how it does. I expect the mpg will go up some. Not that it is an issue.
 

Scooby

Hasn't posted much yet...
56
16
8
Wake Forest NC
Genesis Model Type
2G Genesis Sedan (2015-2016)
I can't say for a luxury car tire... but on my Jeep that has 37" tires load range D and requires 65lbs. I run 32 lbs on the road and 12 lbs off road. The ride and handling characteristics are much better at 32 lbs. Of course it's a truck tire so even deflated there is very little buldging of the side wall.

I would suggest dropping in 2 lb increments as you may find that 28, 30 and 32 lbs run very similar and you'll be more in line with the tire spec.

Good luck!
 

Spanky61

Been here awhile...
380
50
28
NM
Genesis Model Type
Genesis G80
Try 42 with the weight of the car I think you'll find it to handle better and support the weight better also. Max Range is 52 for the Conti's
 

pmckechnie

Registered Member
230
13
18
Matthews, NC
Genesis Model Type
Genesis G80
Update. We took a trip going from NC to NM and across Texas from El Paso to Waco, then to Brownsville, Corpus Christy, and back to NC via
the southern route to Flordia and up to NC.
Tire pressure set to 36 psi cold which went up to 39-40 psi hot.
Ride was quiet and smooth on the good roads and noisy and rough on the bad roads.
What I liked about the higher pressure was the MPG.
We drove 4834 miles and averaged 27.9 MPG for the trip.
Lowest was 24.1 at 80 mph and a strong head wind. It was almost all highway.
Best was 30.8 at 75 mpg most of the time but had some site seeing excursions also.
I am sure the higher pressure helped. However when we got home I drooped the pressure to 33 psi
and can tell a big difference in noise and comfort. I will be using 33 psi from now on.
Another observation was that the calculated MPG and the car computer MPG were very close
at +/- 0.3 mpg. One fillup was off by +1.8 in the car but we were in a traffic jam for quite a while on that tank.
Over all we had a great trip. I love the G80 and can't wait to take the next trip to who knows where.
______________________________
 

EdP

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Genesis G80
Update. We took a trip going from NC to NM
We drove 4834 miles and averaged 27.9 MPG for the trip.
Lowest was 24.1 at 80 mph and a strong head wind. It was almost all highway.
Best was 30.8 at 75 mpg most of the time but had some site seeing excursions also.
I am sure the higher pressure helped.
I love the G80 and can't wait to take the next trip to who knows where.
Decent mileage given the size of the car. The Genesis is the most comfortable car I've had for long trips.
On the highway for a time I get up to about 41 psi.
 

Tennexplorer

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0
1
I increased mine to 38 front and 40 rear. The one comment I had about the car was it seemed “flat footed” in the rear if you hit a bump. The ride seems about the same with the increase but bumps do not seem as harsh. I believe the lower pressure did not support the tires sidewall properly.
 

Spanky61

Been here awhile...
380
50
28
NM
Genesis Model Type
Genesis G80
That's correct, you're in a very heavy car. Most people are running them at the specified psi noted inside the door. These are NHTSA rating adopted by nearly every manufacture. You need to be running them at a minimum of 40 psi. Max load rating is 55 psi. When the tires are under inflated they squat on the wheel and expose more sidewall. Further, at below recommended psi you also run the risk of possible sidewall separation.

At 28 psi the G80 tires are dangerously under-inflated. As yourself this question; Can I live with the possibility of having a serious accident or causing one?
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Tennexplorer

Hasn't posted much yet...
7
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1
That's correct, you're in a very heavy car. Most people are running them at the specified psi noted inside the door. These are NHTSA rating adopted by nearly every manufacture. You need to be running them at a minimum of 40 psi. Max load rating is 55 psi. When the tires are under inflated they squat on the wheel and expose more sidewall. Further, at below recommended psi you also run the risk of possible sidewall separation.

At 28 psi the G80 tires are dangerously under-inflated. As yourself this question; Can I live with the possibility of having a serious accident or causing one?
Would you recommend 42 all the way around or 40 front and 42 rear? Possibly easier question is what do you run yours at? Mine is the G80 5.0. Thanks!
 

bubbaG80Sport

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SUSTAINING MEMBER
143
30
28
Tennessee
Genesis Model Type
Genesis G80 Sport
On my 2018 G80 Sport 3.3L HTRAC/AWD I've been fiddling with the pressure on the factory Continental ProContact TX tires. Factory/door label states 34 PSI front / 38 PSI rear. I've been running at 36/40 for the past week. This seems to be the best pressure for ride comfort and handling.

I was getting some minor vibration at low speed (10->40MPH) when tires were cold. Once the tires heated up (+ 2/3 PSI) the ride smoothed out at these speeds. Now running at 36/40PSI this vibration is less/more acceptable.

Once these tires wear out I'll be going to Michelin Pilot Sport A/S 3+ or Continental Extreme Contact DWS06 tires.
 
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