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Discussion Starter · #1 ·
Hi,

I know it's been posted countless times but still bit unsure about my tyres Pressures and what I should be setting them to. I have MK3 2017 ST model and The recommended tyres Pressures on 19inch wheels both in sticker and book say 41psi and 38psi (front and back).

I've been setting them and topping them up to that since the summer but my concern now in winter conditions on wet damp roads I should be setting them lower. I commute 200miles a week and the drive feels more skiddish, less grippy and less comfortable in general. It doesn't feel safe when putting power down in low gears and I'm not talking about hard acceleration. Also noticed a slight delay with the car hesitating is jerky/jumpy when accelerating changing up 2nd or 3rd gear when getting up to 2.5-3k revs. That's with either shell v power or normal unleaded. Would you say that's sign of a misfire? Other than that, the car is fine. I had stage 1 map done back in September and seemed fine and then started to use super unleaded.

What do people recommend regarding tyre pressures? Do continue to pump up to recommended?

I also have issue with the driver's side rear tyre sensor leaking air before and after having two new Goodyear's placed on the back last month. This is due to go back into Ford for few days (already been in twice albeit on a Saturday, so not been properly diagnose, I've had fault codes for body control module in regards to tyre pressure sensors) as I've had ongoing TPMS sensors not detected fault since September so asked them to check and replace that sensor as it's causing my tyre pressure to drop by 10-12psi over course of few weeks.

Thanks,

Rob
 

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Mk3 ST Sabre 350R
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Personally, I stick to the recommended pressures. Although it's stating the obvious, I'd attribute the 'skiddish' feeling to a combination of road surface (PSV) and tyre friction (or the lack of it) exacerbated by moisture and winter gritting, and although you may marginally increase mechanical grip by lowering the pressures, the consequences can be premature tyre wear and in extreme instances overheating causing a blowout.

Re: 'jerky/jumpy' acceleration, could be an early warning of a coil pack on the way out. What's it like at idle, it is misfiring, have you checked the plugs for gap, wear, fouling?

Re: the TPMS, I just dispensed with the sensors and switched to standard valves (you can opt for steel valves if prefer), they are more aggro than they're worth IMO, fine when they're working properly they'll alert you to an underinflation, but who doesn't check their tyre pressures regularly anyway (same with oil & fluids) and in the event of a rapid deflation/blowout they're not really must use either. What are your rims like, are they perhaps leaking on the bead due to internal corrosion?
 

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Discussion Starter · #3 ·
Thanks, I will continue to stick with the recommended pressures in that case. Only reason I ask is because of a combination of conflicting information I've been hearing from Garages and Tyre fitters "that seems really high, is that right? Should expect that on a van, your pressures are way too high" etc despite telling that's Ford's recommendation in the manual. Understood Re: explanation of attibuting the road conditions and moisture/road salt etc to decreased levels of grip and not feeling as planted as in higher temperatures in the summer.

RE: "Jerky/Jumpy acceleration" with the revs, as far as I can tell overall I haven't experienced any issues at idle that are ascribed to what a misfire would be. No rough idling or lose of power. It's only when accelerating in 2nd or 3rd gear up to about 2.5-3k revs before feel slight jerky hesistation in power delivery/response and have to let go of the throttle in fear it might lose grip and seems to lack little bit of power, like it's hitting flat spot, if then let it drop slightly and get back on picking up, it's fine, of course I could be mistaking this for the TC kicking in.

RE: TMPS issue, What do you mean by dispensed with the sensors and switching to standard rubber valves? Won't that mean the ECU send a signal from Body Control Module to trigger the TPMS light to stay permanently on if they are removed? It's due to go back to Ford for a few days on 24th under warranty as original reported "Tyres sensors not detected" to them in October and I've made them aware of book the small leak of air escaping from the driver's side tyre sensor since and also two faults that I had code scanned and had returned back a few months ago which is related to tire pressure sensor.

"Two faults have returned:

Body Control Module B124D-02 - Tire Pressure Sensor.

Instrument Panel U0073-88 - Control Module Communication Bus off."

My MOT is due at end of March and happy to dispensed with the sensor and switching to standard valves if saves me the aggro as this has been ongoing inermittment problem for 5 months now and rather in the long term not have this constant issues as always manually check my pressures with halfords digital tyre gauge. The rims seem okay not obvious corrison, just bit of flaky curbed damage. Tyre fitter show me some scuffs on inside of driver's side rear when the new goodyear tyres on the back were fitted last month.
 

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2019 AMG C43
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If you think the TC might be kicking in, press the ESC button once and will make the TC less intrusive. Press and hold the button for four seconds and you'll enter Sport mode which turns off the TC and reduces the ESC effects as well.
 

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Discussion Starter · #6 ·
Ideally don't want to disable it as it has some benefit I guess and not sure if that will get flag up on MOT and be considered a failure.

Do you know if these stems replacement valves are compatible with MK3 ST 2017?

 
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