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Non Runflat Tyre Pressures
- sunnydays
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Non Runflat Tyre Pressures
Hey all,
Switching over to Michelin Pilot Sports 4S on my 35IS from the stock runflats.
The default tyre pressure is relatively high, everything I have read suggests that tyre pressure is vehicle dependant not tyre so I am leaning towards running the BMW defined pressures of 44 / 34 psi (off the top of my head)
Any thoughts guys?
Cheers
Switching over to Michelin Pilot Sports 4S on my 35IS from the stock runflats.
The default tyre pressure is relatively high, everything I have read suggests that tyre pressure is vehicle dependant not tyre so I am leaning towards running the BMW defined pressures of 44 / 34 psi (off the top of my head)
Any thoughts guys?
Cheers
-
- Senior Member
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- Joined: Sun Nov 20, 2016 2:49 am
Non Runflat Tyre Pressures
You're right. But, for the 35iS, it's 44 rear and 36 front.
Vidi, vici, veni
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Non Runflat Tyre Pressures
You're also right that tyre pressures are vehicle dependent.
They're also size & profile dependent.
They are not RFT dependent. On the same car, RFTs and non-RFTs have the same pressures.
They're also size & profile dependent.
They are not RFT dependent. On the same car, RFTs and non-RFTs have the same pressures.
Vidi, vici, veni
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Non Runflat Tyre Pressures
If anyone wants to argue these facts, just refer them to BMW itself or Michelin, Pirelli, Goodyear ...
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Non Runflat Tyre Pressures
BMW also put a convenient little sticker on their cars, of course, to confirm the tyre pressures for the vehicle in question.
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- R.E92
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- Joined: Wed Dec 04, 2013 10:10 am
Non Runflat Tyre Pressures
I found that running the stock pressures makes the car feel unsettled.
I now run 40 rear and 34 front. Best for both the PSS and PS4S. Nice even wear too.
I now run 40 rear and 34 front. Best for both the PSS and PS4S. Nice even wear too.
- Garvin
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Non Runflat Tyre Pressures
Facts? Where did you get these facts from?Busterboo wrote: ↑Wed Jun 28, 2017 11:10 am You're also right that tyre pressures are vehicle dependent.
They're also size & profile dependent.
They are not RFT dependent. On the same car, RFTs and non-RFTs have the same pressures.
and
If anyone wants to argue these facts, just refer them to BMW itself or Michelin, Pirelli, Goodyear ...
Pressures are tyre dependent - the pressures given by BMW are, at best, linked to the RE050A RFTs they fit to the Z4 or, at worst, a compromise across a range of RFT tyres.
Below are the tyre pressures from the F355 handbook where Ferrari bothered to test the F355 with each of its recommended tyres - same size (non-RFTs) but significantly different pressures for each tyre brand.
It's a bit experimental but when I fitted (same size) MPSS to the F355 the best tyre pressures turned out to be 34psi front and 36 psi rear. Over 40psi for rear non-RFTs on something the size of the Z4 seems a tad high to me!
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Non Runflat Tyre Pressures
Actually, 44 & 36 are a tad low.
The correct conversion into psi of the bar figures is higher.
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Non Runflat Tyre Pressures
And the "non-RFTS" element is irrelevant.
Both RFTs & non-RFTs of the same size are inflated to the same pressures.
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- Smartbear
- Lifer
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Non Runflat Tyre Pressures
Then how do you explain the manufacturers table above? It shows tyres of the same size inflated to different pressures.
Rob
e89 Sdrive 20i, plenty of mumbo & good economy-the thinking bears z4
e89 Sdrive 30i, this ones busted, pass me another...
e85 3.0si sold
- R.E92
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Non Runflat Tyre Pressures
I'm with Garvin on this. Different tyres need different pressures.
I think the construction of the tyre will determine the contact patch at different pressures. RFTs have wildly different construction to proper performance tyres.
I think the construction of the tyre will determine the contact patch at different pressures. RFTs have wildly different construction to proper performance tyres.
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Non Runflat Tyre Pressures
Could you let us know your thoughts on the ride comfort please?sunnydays wrote: ↑Wed Jun 28, 2017 9:57 am Hey all,
Switching over to Michelin Pilot Sports 4S on my 35IS from the stock runflats.
The default tyre pressure is relatively high, everything I have read suggests that tyre pressure is vehicle dependant not tyre so I am leaning towards running the BMW defined pressures of 44 / 34 psi (off the top of my head)
Any thoughts guys?
Cheers
-
- Senior Member
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Non Runflat Tyre Pressures
That said, car makers do recommend tyres & pressures, of course. BMW - Bridgestone, Porsche - Pirelli P Zero Rosso N~ for the 911, and so on.
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Non Runflat Tyre Pressures
Tyre manufacturers will tell you that tyre pressures are vehicle dependent. If you don't believe me, contact them and ask.
Many 2017 tyres by the major manufacturers are coming as 'XL' - with stiffened walls for higher loads and do not have "wildly different construction" from RFTs.
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