revtothelimit - motorbike forum

Bit of a weird one which is making my scratch my head a little.

One of the tyres in my car keeps losing pressure, but only to a certain point. It's got the in wheel pressure monitors (legal requirement AFAIK after a certain year) so it's pretty easy to track. I pump it up to spec 290kPa* but then it drops to 200kPa roughly overnight, but it seems to then stay there. Driving the car and warming the tyres up brings it up to ~220kPa like you'd expect.

I can't work out why it would leak, but only a bit. Can't see anything sticking out of the tyre etc. I can only guess it's either got a very very small leak, or perhaps some gumpf stuck in the valve?

I would take it back to the garage, but their solution to all these problems is to spend £1000 on a new wheel and tyre

System defaults to the European spec kPa and I can't be arsed to change it, bite me

Might be a porous rim - had this once on a 10 year old wheel. Garage just painted a load of sealant on the inside of rim and it was all good. Have you checked the valve core is tight?

Car has 2000 miles on it, it's 3 months old, so I doubt (hope!) there's no corrosion or anything like that.

No, by the way, I haven't I was thinking similar.

For £500 plus expenses...

KungFooBob wrote: Tue Oct 01, 2024 3:51 pm For £500 plus expenses...

I can buy 2/3 of a new wheel

Hence why I haven't asked the garage yet

+1 on the valve

Mr. Dazzle wrote: Tue Oct 01, 2024 3:22 pm Bit of a weird one which is making my scratch my head a little.

One of the tyres in my car keeps losing pressure, but only to a certain point. It's got the in wheel pressure monitors (legal requirement AFAIK after a certain year) so it's pretty easy to track. I pump it up to spec 290kPa* but then it drops to 200kPa roughly overnight, but it seems to then stay there. Driving the car and warming the tyres up brings it up to ~220kPa like you'd expect.

I can't work out why it would leak, but only a bit. Can't see anything sticking out of the tyre etc. I can only guess it's either got a very very small leak, or perhaps some gumpf stuck in the valve?

I would take it back to the garage, but their solution to all these problems is to spend £1000 on a new wheel and tyre

System defaults to the European spec kPa and I can't be arsed to change it, bite me

Have you tried rebooting it?

Mr. Dazzle wrote: Tue Oct 01, 2024 3:50 pm Car has 2000 miles on it, it's 3 months old, so I doubt (hope!) there's no corrosion or anything like that.

No, by the way, I haven't I was thinking similar.

If it's only 3 months old, does it not have a warranty? If so, take it back and tell them something is wrong with the wheel.

You've got a nail or similar in the tyre somewhere

Pump it up to 290 or whatever, take it off, spray it all over with soapy water and look for the bubbles. Unlikely to be a faulty wheel but that would be a warranty situation. Most likely a tiny puncture.

McNab wrote: Tue Oct 01, 2024 5:58 pm If it's only 3 months old, does it not have a warranty?

It does yeah, of course.

It's made by company I work for and leased via an employee scheme*. I'd have to take it back to fleet HQ and their solution to most problems is replace the part and if it's a damaged wheel it gets tricky in terms of paying for it. If it's potentially damage to the wheel I'd rather find that out before going in.

If it's a puncture they won't let me have the car back until I pay for a dealer fit tyre.

Downside of the employee lease scheme.

*not gonna get into the deets, but it's not a benefit with BIK, it's not a company car either. Basically a private car sold at a big discount.

Rockburner wrote: Tue Oct 01, 2024 5:41 pm Have you tried rebooting it?

You joke, but one of my first thoughts was that the TPMS was wrong, not reality. But no, I've confirmed with a traditional pressure gauge that the electronics are correct.

Does the pressure go down only when it's being driven? If so I'd suspect physical damage rather than a dodgy valve.

Motherfucker's gonna drop the pressure
Motherfucker's gonna drop the pressure
Motherfucker's gonna drop the pressure
Motherfucker's gonna drop the pressure
Motherfucker's gonna drop the pressure
Motherfucker's gonna drop the pressure
Motherfucker's gonna drop the pressure
Fucker's gonna drop the pressure
Motherfucker's gonna drop the pressure
Motherfucker's gonna drop the pressure
Motherfucker's gonna drop the pressure

Mussels wrote: Tue Oct 01, 2024 8:58 pm Does the pressure go down only when it's being driven? If so I'd suspect physical damage rather than a dodgy valve.

It seems to just drop from 290kPa to 200kPa and stay there, which is what's so weird about it. Like I said, it goes up again when you're driving due to the temperature increase. This weirdness is what initially made me think it was a problem with the monitoring system.

I pumped it up to 290kPa on Saturday, drove to work on monday and got a warning it had dropped to 200kPa again part way into my journey. 50 miles later it was 220kPa, then 200 again when I left in the afternoon. It was 200 today when I nipped into town.

200kPa is just under 30psi BTW, so it's not like I'm driving on a completely flat tyre. The fronts are only 250 as standard. I even wondered if the TPMS had a lowest possible reading of 200, but apparently not.

I suppose the solution is gonna have to be take it to the garage.

After you pumped it up on Saturday did you check the pressures before your drove it on Monday? I'm wondering now if your problem is down to temperature changes rather than a leak.

Could you take it to a high street tyre fitting place and ask them to take the tyre off and inspect it? Or maybe put some puncture fixing goo in there?

£450, but I'm cutting my own throat.

Mussels wrote: Tue Oct 01, 2024 9:30 pm After you pumped it up on Saturday did you check the pressures before your drove it on Monday? I'm wondering now if your problem is down to temperature changes rather than a leak.

Checked em on me phone

What's kpa?

Kilopascals.

100kPa = 1 bar.

The car displays default to kPa and that's what's typical for most of the world. I'm sure if I dug into it I could change the display to psi but I CBA

It's kinda like mph, only we brits and the Yanks really use psi just like it's only really us who use mph.