Tyre Pressure for long distance drive

[the_trademarc]

I know there's a few threads going around regarding tyre pressure, but wanted a specific answer as opposed to general discussion.

Going up to Tathra from Melbourne in a couple weeks with my mates, wanted to know people's opinion on the best tyre pressure for maximum fuel efficiency without comprimising ride comfort.

Currenty have 18's on BF Goodrich Low Profile Tyres, Max Recommended pressure is 50 PSi, I normally use 46 normal driving.
Would I keep it at 46, or bump it up to maybe 48 for the trip?

[_R_J_K_]

Just remember that the heat in the tires will cause the pressure to rise by a few psi. Running your tires at 46psi is already probably getting pretty good efficiency anyway.

[stocky]

i run my 18s at 40. 46 seems a bit high

[AUSFITTER]

The air pressure isnt going to increase massively. Its not like you are driving around a race track doing 200km+, not even a long trip is going to get the tyres to a temperature like that. You also have to look at what load you would be putting in the car, more weight in the rear, meaning a little more pressure to accomodate it. 46psi is pretty high though, i was running 36psi on my 19s on my clubby when i was doing normal driving, and when i went away with load in the boot, i went to 38psi in the rear. Unfortunately everyone, including proffessionals have there own opinions, so you have to find the info that you think is correct.

[Darren_L]

unless you are going to be travelling in a particularly hot climate (eg NT) then as said the pressure increase from the heat build up in the tyres will be negligible. I never change the pressures in my tyres on long trips. IMO just run whatever you usually run

[Asmodai78]

do an experiment, drive up there on the normal pressure you use and record your fuel usage, then on the way back bump it up and see if there is any difference, and let us know at it will be a good talking point.

[the_trademarc]

Sweet.
Thanks for the input. On my previous trips I've done 46, 48 once, havent had any complaints about comfort or what not, but I wanted to try something else for this one.
I think I'll leave it at 46, and record how the fuel is going, and perhaps on the way back I might drop it to 44. Because I have low profiles Im a bit hesitant to take too much out in case I have a blow out due to the weight in the car.

[jadatis]

Found this topic , searching with Google for Tyre-pressure, to see if I could spread my noledge about it.
I live in Holland , and have been busy with calculating tyre-pressure with use of the same formula and its addings, the European car- an tyre- manufacturers also use to determine the advice pressures. Got hold of it and worked it out.
Learned myself Excell to make spreadsheets for it. translated a few to Englisch to go worldwide with it.

Recalculating tyre-pressure - Windows Live

In this map always take the newest spreadsheet and there is an Example with pictures.
In the first opening screen the needed data from car and tyres are mentioned.

direct answer to your question: You have to determine what load there will be on the "heaviëst" wheel of front and rear axle in the situation you are using.
Then take some extra for reserve, so you wont sertainly have to much weight on each sepeate wheel.
Then you have to decide what speed you will ride at absolute maximum.
If you take care that the real actual weight on the axles ( or beter heaviëst wheel of each axle times 2) is between 85% and 100% of the load you calculate the pressure for, the tires will bounce comfortable and have no chanche of damage.

The European car- manufacturers gave in earliër days advice for normal use.
American , and I think also Australian used another formula, up to 2005 wich came to lower pressures so warmer tires. Also always only gave advice-pressure for maximum load of car, for wich they filled in the Gross axle weigh ratings of the car.
For SUV they added 10% to that because of the high gravity-point of those cars.
European used from the begining of radial tires the saver formula and did not add for SUV.
Also Eur goes down to 22 psi where Am stops at 26 psi.

So use the spreadsheet and see what for your situation is comfortable and save.
And if questions pop op , ask them here

[Asmodai78]

I repeat:.....

do an experiment, drive up there on the normal pressure you use and record your fuel usage, then on the way back bump it up and see if there is any difference, and let us know at it will be a good talking point.

[wogstyler]

I use 40psi in my 18's.
all the tyre blokes round here say no more then 40psi or else youll chop out the center of the tyre

[PaulSV6]

46 damn! i run mine at 38-40.

[ryno_vrx]

yeah i think mines at around 38 havent checked it in months

[Drewie]

34 to 36 PSI in my 17" SS, I wouldn't go over 40 PSI.

[PaulSV6]

46 damn! i run mine at 38-40.

Should have clarified, im still running the stock SV6 17".

[the_trademarc]

Should have clarified, im still running the stock SV6 17".

Yeah lol.
Like I said, Im using 18's low-profiled, so I was told to use a higher pressure to maintain its longevity. If I was using stocks, would use the recommended 38's.

[the_trademarc]

do an experiment, drive up there on the normal pressure you use and record your fuel usage, then on the way back bump it up and see if there is any difference, and let us know at it will be a good talking point.

I repeat:.....

Mate Im planning on doing that. We're leaving Wed 3rd Feb, back Sun 7th, so will post up results as soon as I get back

[PaulSV6]

Yeah lol.
Like I said, Im using 18's low-profiled, so I was told to use a higher pressure to maintain its longevity. If I was using stocks, would use the recommended 38's.

But still u shouldnt need to run at 46. 42-44psi would be high enough, i thought!

[Morton]

Higher PSI results in better economy, and you're generally encouraged to run more PSI in lower profile tyres.

Just be careful, even though you may not be racing around, the constant contract-expand of high-speed driving does warm tyres up nicely 46psi would be stacks for you. If it starts belting down with rain while you're on the open road, and you think it's going to continue for a while, pull into a servo and drop them to 40 or 42.

[jadatis]

If you fill in the spreadsheet of my earliër post ( # 8 ) you will see that you dont need to highen up the front pressure, only the back-pressure. The weight of the front -passengers is about 2/3 on the front axle and 1/3 on the back-axle.
That of the back-passengers about 1/5 on the front and 4/5 on the back, for most cars.
Lugage in the trunk or whatever totaly on the back.
So it is almost impossible to overload the front-axle and very easy to overload the back-axle.

But if you have normal car-tyres for a maximum used speed of 99 miles/h ( 160km/h), 36 psi gives maximum load that the tyres can bare. And be honest , do you drive faster then that?
So for front you can go probably lower then 36 psi and that will give more grip on the front.
Mostly the GrAWR front is lower then the GrAWR back. and the tires all around are of the same specifications, and on the back they can bare yust a little bit more with 2 tyres then the GrAWR back.

[the_trademarc]

If it starts belting down with rain while you're on the open road, and you think it's going to continue for a while, pull into a servo and drop them to 40 or 42.

Why is that :S Never done that before??

[kuzman89]

ive got 20inch supersports on mine, run them at 40psi

though lately ive put 16" steelies on the back for completly legal purposes, and put 42psi in em?

[stocky]

ive got 20inch supersports on mine, run them at 40psi

though lately ive put 16" steelies on the back for completly legal purposes, and put 42psi in em?

except that running smaller wheels at the back is illegal regardless of what you are doing

[kuzman89]

except that running smaller wheels at the back is illegal regardless of what you are doing

How so? As long as both wheels are the same on the same axle I'm fairly certain it's legal. I'm doing alot of driving with 400-600kg in the back and 20's won't last long.

Both the 20's and 16's are the same height with tyre from the ground

[immortality]

the crowd that fitted my old 17's suggested 30-32psi, max tire pressure rating was 38psi. i was getting a lot of wear on the edge of the tire but non in the middle. clear indication that the pressure was to low for the tire.

my current 17's i run at 38psi cold as recommended by the my preferred performance tyre shop.

as much as i'd like a nice set of 18's or 19's lower profile tyres dictate a higher pressures. with the current state of NZ roads the ride compromise/damage to rims just wouldn't warrant it

[PaulSV6]

I'm doing alot of driving with 400-600kg in the back and 20's won't last long.

Then why get 20's? Would'nt you think that std 18's or 19's would be more practical!