Mick F said:

Is it better to be over-inflated or under-inflated?
Obviously it's better to be spot on, but how do you know if you are?

If you inflate to the pressure stated in the handbook, and you are sure the pressures in the tyres are correct, how do you know the pressures are correct for your new tyres when they are a different make (but same size) to the originals?

Different tyres need different pressures?
To be honest, I don't know with regard to car tyres, but I do know with respect to bicycle tyres. Same bike with same size tyres but different makes state different pressures. It's all to do with design.

Mick.

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So 32 front and 30 rear? Regardless of whether it’s a bike, a truck, a Fiat 500, a 3 series estate or a Porsche 911?

Pressures are like torque figures, sure, exact is best, but near enough is also going to be safe enough. My rears should be 46 PSI when my car is fully laden on summer tyres. If my gauge is 10% out, then the pressures could be 41.4 PSI which is still going to be safe, or they could be 54.4 PSI which is going to be fine as well.

But if I set the rears wrong in the first place, to say 30 PSI, then they could be as low as 27 PSI which is probably not going to be safe and I run a greater risk of rolling a tyre off a rim or getting a sudden loss of total pressure at speed which could be fatal.

That’s why arbitrary figures are a terrible idea, they could end up with someone being killed.

My Wife's 2015 Hyundai i10 has TPMS. When a tyre pressure hits 29 psi, the TPMS illuminates. It's happened at least 4 times during our ownership (from new), twice just a week after a dealer service, when inexplicably, they for some reason reduce the tyre pressures from the stated 32psi, down to 30psi. I don't know why they do this, they just do so I then have to increase the pressures back to 32psi all round (extra load tyres on these cars as standard).

I quite like TPMS to be honest. In my day job, many of the cars I drive do have it as standard. On a couple of transfer runs in the last couple of weeks, I've had to pull over and get the tyre compressor out and inflate to the correct pressures because the TPMS has illuminated. I sometimes wish I had it fitted as standard to my Saab.

I had a driver's door replaced on my Twingo GT due to accident and the tyre inflation sticker went with the old door. I haven't remembered to check after it was replaced. Consequence: after extensive and futile search I managed to get the info from another GT owner form Twingo forum. Quite lucky I might add as there is just over hundred owners in the UK. The information just was not out there! Renault garages had no idea, and the manual helpfully stated to check the door sticker... It would be really helpful if the info on tyre pressures are in several places (door, manual etc) in case you lost one source

frupi said:

My Wife's 2015 Hyundai i10 has TPMS. When a tyre pressure hits 29 psi, the TPMS illuminates. It's happened at least 4 times during our ownership (from new), twice just a week after a dealer service, when inexplicably, they for some reason reduce the tyre pressures from the stated 32psi, down to 30psi. I don't know why they do this, they just do so I then have to increase the pressures back to 32psi all round (extra load tyres on these cars as standard).

I quite like TPMS to be honest. In my day job, many of the cars I drive do have it as standard. On a couple of transfer runs in the last couple of weeks, I've had to pull over and get the tyre compressor out and inflate to the correct pressures because the TPMS has illuminated. I sometimes wish I had it fitted as standard to my Saab.

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I’m half considering retrofitting TPMS, but then I’d have to buy two sets of wheel sensors as well as the TPMS ECU and adding the harness for it as well.

My day car has TPMS, but my winter tyres don't have sensors (yet). I drove all winter with the warning on....

D

I've not got tpms on my car not do I really seen the need for it quick visual check on the tyre's every few days when your getting in and about once a month check the pressure on a compressor/gauge
Never found mine to drop more then 1psi a month

Implications of tyre pressures here:
Note, Under-Inflated tyres are More likely to suffer a 'Blow out' because every time the side wall comes around to the bottom it flexes and over time this flexing will heat up the sidewall making the tyre more pliable and this increase in tyre material temp will also increase the pressure of the air within the tyre until Pop!

chris3234 said:

I've not got tpms on my car not do I really seen the need for it quick visual check on the tyre's every few days when your getting in and about once a month check the pressure on a compressor/gauge
Never found mine to drop more then 1psi a month

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TPMS isn’t there to monitor your pressure from week to week. It’s more to let you know when you’ve picked up a puncture while driving and are running the risk of having a blowout.

306maxi said:

TPMS isn’t there to monitor your pressure from week to week. It’s more to let you know when you’ve picked up a puncture while driving and are running the risk of having a blowout.

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Correct. In fact, depending on whether it's direct or indirect TPMS, it might not actually be reliably measuring pressure at all. Indirect systems use the ABS sensor to measure wheel diameter and infer an inflation issue from this.

gazz_bee said:

Correct. In fact, depending on whether it's direct or indirect TPMS, it might not actually be reliably measuring pressure at all. Indirect systems use the ABS sensor to measure wheel diameter and infer an inflation issue from this.

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Yeah, my F31 uses the ABS type system, you can code it to use proper TPMS that monitors the pressure in the tyre. Obviously you have to put a sensor on each wheel, a TPMS ecu in the car and the wiring harness, but it’s not that difficult.

Mick F said:

32 front 30 rear.
These are the pressures that all of my cars have been happy with.

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All of my cars.
Not all cars.

Mick.

306maxi said:

I’m half considering retrofitting TPMS, but then I’d have to buy two sets of wheel sensors as well as the TPMS ECU and adding the harness for it as well.

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I might give these a go:

https://www.ebay.co.uk/itm/LCD-Wire...m=192448864045&_trksid=p2054897.c100204.m3164