Overinflated tyres?

[Norphy]

Probably a stupid question

 

I bought a new car last week after my accident. This new car has a TPMS and it triggered on one of the tyres today. Annoying, but ok, these things happen. I went to the petrol station, went to the air pump, looked in the fuel cap and it said that they recommended 2.2bar for an unladen car with wheels the size that it has. The tyre that the system reported was at 1.8 bar so I inflated it. I’ll keep an eye over the next couple of weeks and take it to get repaired/replaced if necessary.

 

I checked the others and they’d all been inflated to 2.7bar, or nearly 40psi. That seems way to high to me. Why would the garage have inflated them that high? Am I missing something?

 

I put them down to 2.2, in any case.

Edited June 8, 2023 by Norphy

[3s-gtech]

New tyres on it? Sometimes they don’t set the pressures correctly after popping new tyres on. More likely, they just wazzed them up too high so it could sit for a while without flat-spotting.

 

40psi is too high - but not crazy (check out some videos of garaging finding 100psi+ in customers’ cars) - get them to match whatever the guide in the driver’s door shut specs.

[jmak]

New tyres on it? Sometimes they don’t set the pressures correctly after popping new tyres on. More likely, they just wazzed them up too high so it could sit for a while without flat-spotting.

 

40psi is too high - but not crazy (check out some videos of garaging finding 100psi+ in customers’ cars) - get them to match whatever the guide in the driver’s door shut specs.

 

Unless you've bought a Tesla... Recommended pressure is 42psi [emoji44] Did anyone mention a harsh ride?

[Chris_Cook]

It might be worth checking them when cold and with a different gauge. Temperature from driving can increase the pressure. It might be that they just didn't check the spec for the car.

[MatthewL]

Don't forget to reset the TPMS once you have changed the pressures, common for them to alert when going cold/hot/cold etc. I had a spell of it, nothing wrong with the tyre just use.

[LeMarchand]

I try to check my tyres at home fairly regularly and have often found them over-inflated after new ones have been fitted. Maybe people do it for a "new car" feel?

[Dos_Box]

A problem you have with over inflated tyres is that you wear out the centre first (they bulge in the middle depending on tyre type) and it also reduces your grip. @Norphy, did you check your tyre pressures after a long drive? The air in tyres expands as it gets warm, increasing tyre pressure.

TBH, I just set my front and rear at 35psi as there is only one point difference between the two.

Edited June 9, 2023 by Dos_Box

[Norphy]

The closest petrol station I have is eight miles away, I drove straight there from cold. I don't have a tyre pressure gauge, I should probably get one.

 

That said, even after a long drive I've never seen my tyres at 40psi before!

[LeMarchand]

I don't have a tyre pressure gauge, I should probably get one.

 

Yep, you don't need to spend loads. You can get fairly decent lighter socket powered pumps for reasonable money, too.

[nicholab]

I got 36/42 psi on the motorcycle!

[PotNoodleTech]

It totally depends on the profile of the tyre and the weight of the car. The lower the profile the more PSI needed and the heavier the car the more PSI needed.

 

Hence 44PSi in the rears of my Model S as that's got 35 profile!! It's bizarre coming from my old nissans with baloon tyres that I put 32PSI into

[Norphy]

The car has 16" rims on 205/55 tyres. A pretty far cry from the 225/45/R17s my last car had

 

Anyway, the sticker on the fuel flap says 2.2bar/32psi so I assume that the manufacturer knows best!

Edited June 9, 2023 by Norphy

[Koldov]

A couple of things to mention:

 

a) I've never had a tyre change set at the correct Psi/bar, it's like they have their compressor set at an 'average' and just use that no matter what the make/size of tyre is or the what the manufacturer recommend... even when it comes back from a service at the garage where I bought it from (part of an actual dealership for the make of car), they should be 2.2 bar/32 psi all round for normal driving (unladen) found in the manual and the drivers door. I should imagine a 'new' car could possibly have their tyres pumped a little higher than 'normal' due to the possibility of them sitting around for months...? I doubt they would employ anyone to go around all the cars in the dealership everyday checking tyre pressures (should be done on pre-sale/handover check though)...

 

b) funny thing happened with my 'cheap' compressor... it stopped working the other day, just dead... the OH had been on a very long motorway journey and tripped the TPMS (possibly lost a bit of pressure on warm tyres and so tripped when cooled). I checked the tyres with it and found one that was 0.5 under, so pumped it up and then moved it to another power outlet and... nothing. I checked the remaining tyres with my good old always reliable foot pump and they were OK.

 

I checked the inline fuse and it had blown (F10AL 250V - fast blow 10a), so went through the hassle of ordering more, waiting, finding there was more than one 'size', ordering new ones etc.) only for it to blow again and again (luckily they came in a pack of 10)...

 

I did some research online and in one video it mentioned a spare fuse in the little bag of attachments... Luckily we had kept the box and found it in the garage with instructions and the little bag... now when I checked this 'spare' fuse, I found it was 15A... so maybe it should never have had a 10A in the first place...?

 

Anyway, I have tried to plug it back in and it blows the car fuses for the power outlets instantly.... Which is strange as they're 20A and the fuse in the compressor is 15A (or 10A originally) and fast blow at that....

[Koldov]

More confused than ever and wishing the OH wouldn't have bought a cheap version...

 

https://www.carsun.com/products/carsun-high-quality-mechanical-air-pump-for-12v-car-digital-display-tire-pressure-pump

 

From the website (I've only included the highlights):

 

5. If you want to set the adjustable button with default value, the default value of this pump inflation is 300PSI (+ key is on,-key is off).

 

 

7. Suction the set value upward and stop the pump automatically.

 

8. When re-inhaling, you need to turn off the switch and then turn it on again to start absorbing water again.

 

Maximum Pressure: 150PSI

 

Auto Air Compressor: Tire Inflator 12V

 

So default is 300PSI... but maximum is 150PSI

 

12V but with a 250V inline fuse... the inline fuse included is 15A which is still alive (or 10A originally which didn't survive, nor did the replacement 10A ones) but, blows both the car's 20A fuses (front and rear power outlets)!

 

Why is it re-inhaling and absorbing water...?

 

I doubt it's worth opening up and seeing if something has melted inside, unfortunately it's off to landfill and look for a better version time!

Edited June 9, 2023 by Koldov

[3s-gtech]

The build of these portable tyre inflators is always very basic. Not seen one that seems much cop.

 

However, the Ryobi ONE+ should be a better thing altogether from what I’ve seen.

[Andrew_C]

12V but with a 250V inline fuse... the inline fuse included is 15A which is still alive (or 10A originally which didn't survive, nor did the replacement 10A ones) but, blows both the car's 20A fuses (front and rear power outlets)!

 

Fuse don't care what voltage is. 15A slow-blow may well go before a 20A fast. Depends on the fault current.

[mikeprice]

I generally set my tyres to about 75 psi

 

 

 

 

 

 

 

sorry - were we naot talking about bikes - whoops wrong forum

 

 

anyway - more to the point

 

I also have never had tyres set right by people putting new tyres on it

I have seen them do it and have never seen one open the drivers door to check the plate to see the correct amount

hence they must be just lobbing in an average amount

 

 

I always set them myself when I get home ( cheap looking electric pump with a gauge on it that came with the car)

[Koldov]

I doubt it's worth opening up and seeing if something has melted inside, unfortunately it's off to landfill and look for a better version time!

 

The build of these portable tyre inflators is always very basic. Not seen one that seems much cop.

 

Well, I took it apart because... that's what we do isn't it..?

 

Anyway, basic is right, but to be fair it's only a small consumer grade compressor, so how difficult could it be, right...?

 

Pretty sure this wire is supposed to be attached to something!

 

 

Luckily I had some 12v batteries, so hooked it up and started poking about on different terminal points, couple of little sparks here and there and the display lit up at one point.... then on another part the compressor spun up and nearly took a bite out of my finger...

 

Then I hit the jackpot so I spliced the wire (as I don't have a soldering iron) and it seems to work OK!

[3s-gtech]

That looks pretty clever for a DT project.

 

Oh wait, that was sold commercially?!

 

To be fair, I think they’re all like that.

[Koldov]

To be fair, I think they’re all like that.

 

It's gets better!!!

 

Well, quite chuffed with my newfound electrical engineering skillz... I went to my car after work on Friday feeling quite smug. After wrestling with an annoying Windows Media Player problem for 2 days (and failing) it was nice to have a 'win' (albeit a personal one and not work related) going into the weekend and not feel like a complete failure/imposter...

 

Plugged it into the centre console in the car before I set off home to test it and after a brief flash of life from the display.... NOTHING!

 

Checked the fuse in the in-line 12v connector and it was OK, checked the fuse in the car... blown! Plugged it into the rear 12v... still nothing (no car fuse blown this time though thankfully)...

 

So, I pondered throwing it in the bin over the weekend, but wondering if I didn't secure the wires properly, or might have attached it to the wrong wire, or it may have been more damaged than I thought, etc.

 

But I didn't have the car this weekend (OH doing a trail run in Dorset) or a spare 12v battery to test...

 

So I came in this morning and tested it (on a 12v battery so I don't blow anymore car fuses), first I checked the 12v connector in-line fuse and found it had actually blown (in half).

 

Changed the fuse and got a flicker from the display, then nothing then a flicker (I should add I was plugging and unplugging the adapter). So, after wiggling the wires to see if there might be a break somewhere, this led me to taking the 12v adapter apart...

 

 

Now, even after my initial triumph (?) of finding a loose wire, I will still have to admit that I'm no electrical engineer, however even I think this might be a problem given that one part (the 'spring' loaded clips) should be negative and the other part (the middle bit where the fuse goes) should be positive and 'never the twain shall meet', because this happens when the spring clips are compressed (as they would be when plugged in).

 

 

Anyway I adapted the clip so it wouldn't slide down anymore and put electrical tape between the two just to be certain they won't make contact!

 

 

I've yet to try it in the car (need to buy some more blade fuses first)... but it works 100% every time on the bench with a battery.