250 Tyre Pressures Twitcy/Understeer

Discussion in 'Suspension, Brakes, Wheels & Tyres section' started by Charlie Howard, Jun 22, 2018.

  1. What tyre pressures do you guys use? My fronts are 2.5/2.6 and rears are 2.1/2.2. They have been since I got the car and handling was godlike when I got it but in the past months I've noticed the cars is twitchy under hard acceleration which I understand I will get in a FWD car with 300+BHP but it never used to be! I've also noticed the handling doesn't feel as planted as it used to when I got it.
     
  2. Are you on 18 or 19 wheels
     
  3. Non motorway- 35-30psi

    Motorway- 38-33psi

    Eco- 41-37psi
     
  4. could be swivel bearings if the steering feels vague and wonders a bit.
     
  5. What's that on the in car display as that does it differently?
     
  6. The previous owner replaced the swivel bearings last year so shouldn't be that.
     
  7. I have been known to see problems that aren't there lol but it seems if I accelerate in 2nd then I have limited steering.
     
  8. Run my fronts on 2.2, your fronts seem high.
     
  9. I'll try letting some air out then, it all could be in my head as the car has always had 2.6 on the fronts since I've had it. I did slide into a curb during the snow and then I had to get the wheels aligned but I'm sure they would have checked for anything else too.
     
  10. Added bar figures to the above, just cos I'm bored lol

    I just ran mine at the figures stated on the sticker inside the door.
     
  11. Ah so seems mine is in eco mode. Is there a noticeable difference in MPG in non-motorway mode say. I do a balance of motorway driving and non so not sure what would be best. Not bothered about the ride if I'm honest, might as well put it in non-motorway.
     
  12. Mikeyjp

    Mikeyjp RSM Club Member

    Mine 2.4 f and 2.2 r
     
  13. Sounds scary. What kind of tires do you have?
     
  14. Could be something as simple has tyres have worn and its reach that point. The 19s do tend to stupidily wear more on the outer edges on the front.
     
  15. Tyres still have a lot of life left, Pilot Super Sports. I think I'm over exaggerating the 2nd gear thing, I jj6seem to understeer more in 2nd.

    Although after saying all this, a couple days a go me and my friend went for a nice drive round country roads and I had absolutely no problems keeping up with his brand new Golf R, he did nothing I couldn't do.
     
  16. Get the tracking done on a modern computerized set up.
    Its amazing how these cars respond to even minor adjustments,if the trackings out.
     
  17. Just got it done a month ago, was way out.
     
  18. For track fast road 2.0bar / 2.1 rears

    Normal road 35lbs f / 30lbs rears
     
  19. Lol you've given them in 2 different measurements.
     
    BIG E likes this.

  20. I use both... lol..
     
  21. If you're understeering, add pressure to the rear/remove from the front.
    For oversteer and braking stability, the opposite.

    I'd go to factory settings and add/remove 0.1 at a time until you're happy.

    Mine is at 2.1 cold (front) and 2.3 cold (rear) and the handling is now extremely balanced.
    I was at 2.3 and 2.6 but the grip was compromised, particularly at the rear under braking. I have also noticed no relevant difference in MPG since the change...
     
  22. Hello, I´m new here but will anyway state my opinion right now, because I have the same problem, , 19" as well with Michelin Pilot Sport S4. First it´s very important with what temperature you are checking the pressure. My tire pressure increases by min. 0,2 bars from cold condition just by cruising for 20 kms on the road. With hard pushing on the track, the pressure increases from 2,2 bars to 2.5, even 2,6. If you are on the track, you should correct the pressure after some laps when it has been increasing to it´s peak pressure. Then reduce the pressure to about 2,2-2,3 bars. Basically, the Megane suffers on a lack of camber. If you should have adjustable top mounts, you should go to - 2° of Camber. Then the tires are working much better. Don´t forget to increase the pressure after the track back, it might be to low for fast Autobahn in Germany ;-) If you have coilovers with adjustable dampers, you should make the front setting relativly soft and the rear hard to make the rear more oversteer to reduce the understeer. Without any possibilities to readjust suspension and settings it´s difficult to alter the cars behaviour seriously. Once the car understeers hard ( maybe at Slalom), you should reduce the steering angles by driving "softer" to avoid to challenge the tires more and more, causing even more temperature and understeer.
     
    knowledgeflyer60 likes this.

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