Correct Tyre Pressure

ShortyX on 24/08/2017 - 14:54
Last edited 24/08/2017 - 17:40 by 1 other user

I've always inflated tyres to the tyre pressure on the little placard inside the driver's side door. After getting replacement tyres today (235/60r18), they advised that it should be increased by 4 psi over the placard pressure (so in this case 34 is on the placard but he recommends 38).

Anyone else follow this rule? Are car companies' recommendations lower than what they should be to give a softer ride?

Thanks

EDIT: Found this - http://whrl.pl/RdkyIc

"Tyre pressure is always a trade-off between comfort and performance.

Choose where you want to be on that sliding scale.

As a rule of thumb, I've found this works for me:

Look at the recommended pressures on the sticker, then add 10-15%.

If the ride is too harsh, reduce pressure by 1 psi each time until you hit the sweet spot for you.

Note: if the tyres wear faster at the centre, the pressure is too high for the tyre regardless of your personal preference.

Edit: for vehicles with a 60/40 front/rear weight distribution and default Front wheel drive, I usually run the rear tyres 2 psi lower than the front – unless the cargo area is loaded up.

For RWD, you'll need to work out that sweet spot for the particular vehicle yourself."

Automotive

Comments

  • Cheeper on 24/08/2017 - 15:00
    +1

    Yes they are.
    I find that what the tyre places recommend to be the best.
    I have a sedan and a suv and run 36 or 38 in those.
    This can vary from car to car and with different profile tyres … experiment and see what feels best.

  • psyren89 on 24/08/2017 - 15:05

    After getting new tyres today… they advised that it should be +4 psi

    Only when the tyres are warm.

    • ShortyX on 24/08/2017 - 16:13
      +1

      No, that was when cold.

  • Daniel Plainview on 24/08/2017 - 15:12
    +1

    Is a good question as I got 4 new Bridgestone's on at their last promo and felt it a silly and obvious question so VERY sheepishly asked the owner of the franchise, whos is a good friend of another pal of mine - so no reason to think he'd talk crap.

    He stated essentially exactly what you said - in that the pressures recommended by car makers are so that the ride seems more comfy - but for best results from the tyres he said 38-40psi when cold is what he uses himself.

    One of those times I felt relieved to have asked what I incorrectly felt was a very obvious and easy question. :-)

  • garffi on 24/08/2017 - 15:12

    Depends on what you prefer. My car says 35 psi but I usually run it between 31-33 because the ride gets too bumpy and harsh. Some people put it up to 40, but I also know people who run it at 28. I still have trouble finding that sweet spot…

    • ShortyX on 24/08/2017 - 16:16

      Mind blown. I never really linked tyre pressure to ride.

      (and thus begins a journey of finding the optimal tyre pressure)

    • CMH on 24/08/2017 - 22:47
      +1

      31-33 isn't too bad.

      But 28 when recommended is 35? The next time you take a 1 hour 110kmph ride your tyres will blow…

      • garffi on 24/08/2017 - 23:04
        +1

        I think he mainly uses the car for off-roading which might be why he keeps it that low.

  • Gunther on 24/08/2017 - 15:51
    +5

    Cmon this is Ozbargain…. 40 PSI for fuel economy benefits.

    • Euphemistic on 24/08/2017 - 16:07

      or is it 18PSI to save money on compressor running costs?

      • affable on 25/08/2017 - 08:53
        +2

        Mate, use the compressor at the servo for free, the digital ones they have these days at ColesExpress etc are much better than the bad old days. Infact that's the only time I drop into a servo in my EV.

    • ShortyX on 24/08/2017 - 16:14

      40 PSI for fuel economy benefits

      Is this a serious suggestion? :) Would 40 be classed as overinflation?

      • adr8 on 24/08/2017 - 16:39

        I run 40 PSI on my 20" rims, tyre placard recommends 36 PSI

        NB: tyre pressure should be checked on cold tyres add 10% if inflating hot tyres.

        • tonyjzx on 24/08/2017 - 20:47

          yeah i have no probs with 38-40 in this regard

          also tyres leak so a little more is fine

      • CMH on 24/08/2017 - 22:50
        +3

        My defensive driving course instructor (who is an ex professional racer) told me he'd rather have 10 psi overinflated than 1 psi underinflated.

        He also just recommends 40 psi if you don't know what you're doing.

        So I just go with that advise, and go 40.

    • adr8 on 24/08/2017 - 16:37
      +2

      and extended tyre life

  • [Deactivated] on 24/08/2017 - 17:18

    Telling us your new tire size does nothing as we don't know your own tire size.

    • ShortyX on 24/08/2017 - 17:39

      They're replacement tyres so no change in size.

  • oscargamer on 24/08/2017 - 19:12

    I add 2psi to placard on cold tyres

  • theHMASfriendship on 25/08/2017 - 08:42

    Tyre pressure will rise after driving for a while.

    I go a few PSI above the placard usually.

    • adr8 on 25/08/2017 - 08:53

      I have tyre pressure monitors and after driving for 20-30 mins the tyre pressure will increase by about 4-6 PSI.

      • theHMASfriendship on 25/08/2017 - 08:54

        How much after skids?

        • adr8 on 25/08/2017 - 08:56

          Ha Ha… nah no skids getting too old for that plus 20" tyres aint cheap

        • theHMASfriendship on 25/08/2017 - 08:58
          +1

          @adr8:

          Might have to give it one last crack in the name of science

      • bumblebeetuna on 25/08/2017 - 21:16

        I had this conversation with the guy at my local tyre shop last weekend after getting them replaced. I used to run old tyres at 34, car manufacturer recommended 32. I just felt like 34 performed better.

        Anyway, he says for these new tyres recommend 38psi. Because for daily Metro driving because the tyres won't warm up enough to raise the pressure. He said if I was planning a longer drive some where, to drop the pressure, because it'll rise again after driving did a bit.

  • affable on 25/08/2017 - 08:56

    Only issue running 38+ PSI might be if you live in an area with bad potholes would you possibly be more likely to damage your tyre?

    • adr8 on 25/08/2017 - 09:03

      I would think it is the other way round low tyre pressures would increase the risk of damaging your rim, that is what I have been told. Maybe in my case it is because I have low profile tyres.

    • skillet on 25/08/2017 - 10:41

      Very low profile with very cheap aftermarket rims yes.

  • Ozpit on 25/08/2017 - 08:58

    Higher tyre pressure generally equals better fuel economy, better steering response, harsher ride, faster wear on all suspension components.
    I run 4psi lower than manufacturer recommendations on all tyres as I prefer a smoother ride and like being kind to the suspension.
    Note that I drive at moderate speeds; rarely at or above the speed limit. If I did drive hard, I'd be opting for recommended pressures.
    Obviously, there is a point when a too high or too low tyre pressure starts to become dangerous, e.g. more susceptible to punctures, blowouts, poor steering response, etc.

    • Boshait on 28/08/2017 - 11:33

      That's a good point. The road shocks have to be dissipated somewhere (or the vehicle would vibrate permanently after every pothole, stick on the road etc). Mainly that is going to be in the tyres and the suspension (and to a small extent in the driver, which is why softer tyres are perceived as providing a smoother ride). Where the economic optimum lies is an interesting question, but pumping your tyres harder isn't a free lunch.

  • skillet on 25/08/2017 - 10:38

    Running higher than recommended tyre pressure also put more stress on your suspension system. The tyres absorb less impact when filled with more air. So you may have to rebuild your suspension sooner = $$$.

    I would note the fuel economy with the placard pressure then compare the economy with increased air pressure. If negligible then I prefer comfort over economy.

    I tried 15 and 20% increase, it was very harsh. Drop it down to 10% it was ok but handling improved.

    • ShortyX on 25/08/2017 - 10:56

      Prefer comfort economy

      Did you buy an $80k car as an investment? :)

  • Peck on 25/08/2017 - 10:54

    was told the same by a very good mechanic many years ago, so I do the same. And also the tyre pressures drop over a short time and so it won't be on that pressure for long anyway.

  • Architectonic on 25/08/2017 - 16:04

    The reason why you pump over the placard amount is because over time the tyre pressure drops - so unless you check your tyre pressures frequently, it is better to slightly overinflate, rather than let your tyres become underinflated due to infrequent checking.

  • Drifter on 25/08/2017 - 20:10

    For me, handling is more important than comfort so I go higher than recommended. I get less sidewall flex, sharper steering and generally better handling.

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