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Derv? Nein Danke.
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130 Posts
Discussion Starter #1
I've had my Mini for exactly 8 weeks now.

When I bought it, it had one replacement tyre fitted.

Today I checked the tyre pressures as a matter of course not because of any visible signs of a problem.

The new tyre that was fitted was at 34psi, so assuming they had inflated it the the stated 36psi it had dropped an expected 2psi.

The other 3 tyres were at 25psi!!! :aargh: In 8 weeks have the original tyres really dropped 11psi, whereas the new one has only dropped 2psi???? :puzzled: The run-flat inidactor light has not come on at all, but surely if there had been a pressure drop with such a huge differential to one wheel it would have lit surely??

I'm guessing that the dealer didn't bother checking the pressures much like the rest of car and subsequent problems I found?

Is there a rule of thumb that long term owners have found regarding expected pressure drops on Dunlop Run-flats?? I've always checked tyre pressures on my other cars at 6 to 8 week intervals and normally put around 3psi to top them up, I've never had such a huge pressure drop. :puzzled:
 

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still learning
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1,270 Posts
the dealer probably has not set the pressures correctly........ and you should have checked them yourself after collecting the car.

set them yourself at 2.2 bars and reset the pressure monitor.

check them again after a day or two to see if there is a difference.

ps 6 to 8 weeks is far too long between checks, you need to do it every week !!
 

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Derv? Nein Danke.
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130 Posts
Discussion Starter #3
Having paid 16k for a 'Cherished' (ha, ha) Mini, I didn't even think about checking tyre pressures and never have had to on any of the other cars I've bought over the last 22 years!! I expected the Mini to be prepare with the same level of care and to the same standard as all the other manufacturers I've bought from.

I've also never needed to check tyre pressures weekly either, as I said every 6 to 8 weeks has seen approximately a 3psi max drop on my other cars. If my tyres were needing to be checked and re-inflated on a weekly basis I'd think that something was seriously wrong. :wink: :biggrin:

I've inflated them correctly now (2.5bar all round according to my door sticker) and reset the monitor and will check them alot more regularly to see if they are prone to loosing pressure more so than other cars. Based on the fact the new tyre had lost so little pressure and was in line with previous cars, I'm hoping it was a dealer cockup. Just hoping I'm not blighted with overly porous alloys.
 

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still learning
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1,270 Posts
unfortunately you cannot trust the dealer to set your tyre pressures correctly and always check them yourself.....................that's just the way it is.

I would not be happy driving about with my tyre pressures at 3psi less than they should be...............it only takes five minutes to check them ?
 

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Derv? Nein Danke.
Joined
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130 Posts
Discussion Starter #5
99% of cars owners use forecourt compressors with their accompanying pressure guages. Its a well known fact that forecourt pressure guages are inaccurate and could easily be 3psi+/- out from the true pressure. I've not met anyone that fanaticaly checks tyre pressures on a weekly basis, my neighbours would think I'm bloomin nuts!!

Unless a car is being tracked and driven on its limits a 3psi pressure variance makes little difference. Ambient temperatures changes between mid summer and mid winter make warmed up tyre pressure different, yet no car manufacturer (that I've seen) gives different pressure for summer/winter time. Its also interesting to read various threads on here about how some people choose to run higher and lower tyre pressures (compared to book) to make the car feel right to them.

I certainly do not drive in a manner that requires fantatical checking of tyre pressures to ensure they are always and constantly bang on to the nth degree. I also do not find it neccasary to check my oil level every week!! :aargh: :hmph: 8 weeks on and it hasn't used a drop. Checking once a month will do me just fine. :biggrin:


Back to my original query ........................... can amy long term owners pass on their experiences regarding the expected pressure drop of their tyres over a given time period.
 

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Back In A Clubman 23yr On
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194 Posts
Unless a car is being tracked and driven on its limits a 3psi pressure variance makes little difference. Ambient temperatures changes between mid summer and mid winter make warmed up tyre pressure different, yet no car manufacturer (that I've seen) gives different pressure for summer/winter time. Its also interesting to read various threads on here about how some people choose to run higher and lower tyre pressures (compared to book) to make the car feel right to them.

I certainly do not drive in a manner that requires fantatical checking of tyre pressures to ensure they are always and constantly bang on to the nth degree. I also do not find it neccasary to check my oil level every week!! :aargh: :hmph: 8 weeks on and it hasn't used a drop. Checking once a month will do me just fine. :biggrin:
Coupe,
The changes in ambient temperature actually have very little affect on the "running" pressure of a tyre........if you were actually to take a pressure reading after a 5 mile or so drive you would be surprised at the change from "book"....(i.e they go up with use)...this is why they are quoted as "cold" pressures. However...you are quite right that the "cold" pressure would vary between the seasons, and they do not quote for this.

Having done several technical tyre courses for work, hosted at different manufacturers, I can tell you that the same basic "liner" design is used on both run ons/run flats as normal tyres. Therefore, the pressure drop characteristics should be the same as other tyres. We use run flats at work on 535d tourings doing 1k - 1.5k per week.......and the pressure drop is consistent with standard tyres.

I think that you might well have been slightly over optimistic about the dealer's attention to detail........and the "reset and monitor" suggestion is probably a good one to follow to see if there is another problem present.

Sorry can't be anymore help than this.
 

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Derv? Nein Danke.
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130 Posts
Discussion Starter #7
Cheers Mr Numpty, interesting stuff and good to hear that the run flat characteristics are similar to 'proper' tyres :wink: :biggrin: I've learnt very quickly that 'Mini dealer' and 'attention to detail' go together like oil and water!! :hmph:

Am I right in saying that tyres gain approximately 4-5 psi from their cold temperature against their running temps??

Have you got round to wiring your spots in yet?? If so how did you get on? :smile:
 

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Back In A Clubman 23yr On
Joined
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194 Posts
Cheers Mr Numpty, interesting stuff and good to hear that the run flat characteristics are similar to 'proper' tyres :wink: :biggrin: I've learnt very quickly that 'Mini dealer' and 'attention to detail' go together like oil and water!! :hmph:

Am I right in saying that tyres gain approximately 4-5 psi from their cold temperature against their running temps??

Have you got round to wiring your spots in yet?? If so how did you get on? :smile:
Actually, the running temp pressure is probably nearer to 10psi above the cold.....I have personally seen more than 20psi for certain vehicles under certain conditions (loads and use).

The spots were "installed" as a part of getting the vehicle ready for its visit to "the pirate" last week....including the other bits like JCW bumper, aero grill etc......because I wanted the vipers to go down onto the valance. However....they are not yet "wired in":rolleyes:
Basically, I did not have time to get this completed at the same time...but I hope to complete the wiring loom this coming weekend ;)
 
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