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      01-13-2013, 08:52 AM   #1
jasonprice07
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BMW high tyre pressures

As the title suggests, does anyone think the recommended tyre pressures are high? I've been doing some testing of the Birds suspension I fitted over xmas. For the most part it's an improvement over stock, but I was surprised that I can still feel every little imperfection on the road, I was hoping the new kit would isolate me a bit more, especially as I'm on my 17" non runflat winter tyres.
Came across the following on a Jag XF website, I think the Jag is roughly the same weight and RWD, I found it interesting there is very little change in their recommended pressures, even on the 20" staggered set-up. From memory the pressures for the 35D go up quite a lot as the wheels get bigger.
Anyway, I lowered my pressures to 2.2F and 2.3R and went for a drive around the lanes. Much less feeling of minor road imperfections and the handling still felt ok, was not really pushing it too much as it started to snow

Jason
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      01-13-2013, 09:17 AM   #2
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Does the jag have runflats though?
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      01-13-2013, 09:20 AM   #3
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Tire profile is different as well .....
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      01-13-2013, 10:03 AM   #4
jasonprice07
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I was looking more at the trend rather than exact values, lower pressure and same front to rear.
Most people recommend increasing tyre pressures when switching from run-flats to normal tyres, hence the difference would be even greater.
Just looked at Merc pressures and most of them are similar to the ones on the Jag.

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      01-13-2013, 12:21 PM   #5
zltm089
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hmm...quite interesting...

So if you plan to go over 100mph, then then they recommend upping the psi to 38!!!...
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      01-13-2013, 12:49 PM   #6
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Apart from the xfr which it recommends the same pressure

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      01-13-2013, 12:57 PM   #7
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I found the recommended BMW pressures for the rear to be really high aswell when the car is meant to be on "full load"...i think they recommend something silly like 48psi!!!...
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      01-14-2013, 03:10 AM   #8
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Quote:
Originally Posted by zltm089 View Post
hmm...quite interesting...

So if you plan to go over 100mph, then then they recommend upping the psi to 38!!!...
Iirc it's constant 100mph + if you were on an autobahn or similar.

In out country it won't apply as although its a bit too easy to hit 100mph it certainly isn't for long.
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      01-14-2013, 04:17 PM   #9
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Quote:
Originally Posted by jasonprice07 View Post
As the title suggests, does anyone think the recommended tyre pressures are high? I've been doing some testing of the Birds suspension I fitted over xmas. For the most part it's an improvement over stock, but I was surprised that I can still feel every little imperfection on the road, I was hoping the new kit would isolate me a bit more, especially as I'm on my 17" non runflat winter tyres.
Came across the following on a Jag XF website, I think the Jag is roughly the same weight and RWD, I found it interesting there is very little change in their recommended pressures, even on the 20" staggered set-up. From memory the pressures for the 35D go up quite a lot as the wheels get bigger.
Anyway, I lowered my pressures to 2.2F and 2.3R and went for a drive around the lanes. Much less feeling of minor road imperfections and the handling still felt ok, was not really pushing it too much as it started to snow

Jason
I'm a bit surprised you can feel everything on 17" non run-flat winters. I used to run that size and tyre on my E91 330d touring in winter, and were a very supple tyre at 2.4 bar front and 2.6/2.7 bar rear. I was on standard suspension with Koni FSD dampers.

Have you got the Bird B3 suspension? Isn't the Bird suspension also following a similar concept, to improve secondary ride quality, while retaining primary control?

Quote:
BMWCar wrote: ....and ride quality is streets ahead of any other E92 we've driven. The setup isn't designed to provide a wafty limousine-type ride, but even then the first time you pilot the car, you do feel that it's at the softer end of the spectrum. But then you realise just how much your backside has been conditioned by all of the crazily stiff chassis' that BMW now offers. As mileage builds, you start to realise that it isn't at all soft, but it can eliminate all normal bump shocks from upsetting the chassis and the driver. Hey, isn't that what suspension is supposed to do?
Just thinking outside the box... Is the Bird suspension conflicting with the wheel size? What wheel size and combination is it designed around?

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      01-27-2013, 01:19 PM   #10
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Just switched back to my 18" wheels and summer tyres and the ride is better.
I don't really understand why, winter tyres do have a higher load index 97 and 99 compared to 92 and 94 of the summers.
I borrowed my neighbours car today, e93 SE spec with 17" run flats. The ride was more to my liking if not the body control.
I'm seriously thinking about fitting SE suspension with uprated ARB's as my next experiment.

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      01-27-2013, 02:01 PM   #11
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Jason,

I have birds B3S kit on my e91 msport.

I run non RFT oem 18" rim / tyres.

2.3/2.7 fr and back works v well for me as DD and then add 0.3-0.5 all round for the occassional track day.
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      01-27-2013, 02:31 PM   #12
jasonprice07
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I guess we all have different views on what is good / bad, that's why there are so many aftermarket options I'm finding the B3 kit a bit inconsistent. Sometimes I see a sunken man hole cover which I can't avoid and I hardly feel anything and I think WOW, what an improvement, then I drive over some over bit of crappy road and the cars feels like it did as standard and I'm left confused
I've test driven 2 new cars this week both with adaptive suspension and for me they were by far the best BMW's I've driven, just need to find some money to buy one now!

Jason

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Jason,

I have birds B3S kit on my e91 msport.

I run non RFT oem 18" rim / tyres.

2.3/2.7 fr and back works v well for me as DD and then add 0.3-0.5 all round for the occassional track day.
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