[R129 SL] sl500 proper tire pressure

[Peter S]

Hi Rob, Robert, Jonathan and Marcus,
Tyre pressures!  We could all spend weeks or even years on cars and vehicle 
tyre pressures.  The pressures are dependent upon tyres, vehicle weight, 
vehicle weight distribution, how much stuff we manage to fit in, number of 
passengers carried, and where all this is carried, required handling, road 
construction, road conditions, road 'banking', vehicle steering engineering, 
fuel economy etc etc.  All good engineering stuff!

We presently have some 7 cars and 4 motorcycles/ scooters (including a 
Piaggio MP3!).  Like many car/ motorcycle enthusiasts, I  have possibly 
owned some 100+ vehicles in my lifetime (so far) and driven a lot more 
vehicles in NZ and other countries.  In winter, I tend to run the cars/ 
motorcycles at 32 psi - yes all of them (front and rear), to give a bit of 
grip on the roads just in case.  In Autumn (fall), Summer and Spring, all 
the vehicles are pumped up to 36 psi.  Sorry about the psi bit, but in New 
Zealand we are meant to use kilopascals for the last 30 years - our 
beautiful country uses all metric parameters, but we still tend to use psi 
as the US uses psi!

I run a variety of tyres from Pirelli PZ0, through Bridgestone Potenzas (my 
overall favourite tyres) and currently Kumho's on the R129 ( believe it or 
not my second best favourite brand).  I also have continentals, Firestone 
Firehawks and Michelins on the cars.  In NZ we seem to be fraught with a 
variety of imported Asian tyres that I can hardly pronounce the names of! 
Many tyres are the very dangerous mud and snow tyres that should be banned 
in NZ - another story!

Our motorways here and very different from the freeways overseas. Our roads 
generally use a rougher chip seal, and most of all of our corners are banked 
to allow better handling/ cornering.  Our secondary roads are narrow 
sometimes, not too dissimilar from English country roads.  We have quite a 
few 'gravel' roads as well.  Note that low profile tyres do not track too 
well on gravel, so if I am back country roads for a long trip, I often 
exchange my 18 inch Potenzas on the W123 with the traditional 123 Mag alloy 
Merc wheels fitted with Bridgestone 205/65/15 tyres.

So in brief, being a simple bloke that is not capable of multi-tasking, 
unlike our female counterparts, I put in 36 psi summer, autumn and spring 
and 32 psi winter.   Those horrible space savers in the Japanese vehicles 
have to be run at about 70 psi though - short distances only.

Cold in NZ at present as it is our winter - about 4 degrees C here today. 
Acquired a chill 3 weeks ago and have had a dowse of influenza (not the 
swine type!) - main possible cause - driving the R129 with the top down, 
outside temp at about 2 degrees, and not having enough gear on!  We have our 
National Mercedes Benz AGM in Picton (top of the North Island) next week so 
will have to get my woollies out as we will be in the R129 with the top down 
heading across on the ferry.  The greater Picton area has about 150 wineries 
within a 100 km radius, so I wonder what else we will be doing......

Have a great week.
Regards, Peter S.


----- Original Message ----- 
From: "Rob Vonderhaar" <rob at robvonder.com>
To: "SL Mailing List" <r129list at mbcoupes.com>
Sent: Thursday, July 16, 2009 6:23 AM
Subject: Re: [R129 SL] sl500 proper tire pressure


I'm running 32 psi front and 36 psi rear (cold) on my 2005 SL500 with the 
AMG Sport package.  Watching the tire pressure monitors while driving, this 
climbs to about 35 & 39.  I also have a 1995 SL500 with similar 18" AMG 
wheels set at those same pressures.

Seems like a good compromise on both cars in terms of giving decent handling 
without feeling every imperfection in the road.  Anything higher just gets 
so rough that it's not fun to drive.  I agree with your mechanic that 28 psi 
in front is too low.

     Rob
_________________________
Sent from my Omnia Windows® phone.

-----Original Message-----
From: rtorchia at aol.com <rtorchia at aol.com>
Sent: Wednesday, July 15, 2009 1:48 PM
To: r129list at mbcoupes.com <r129list at mbcoupes.com>
Subject: [R129 SL] sl500 proper tire pressure


I know this sounds dumb, but I have heard all sorts of opinions about
tire pressure on an sl500. I have Bridgestone Pole Potenzas Z rated
that take a maximum of roughly 50 PSI. The Mercedes manual says 28 PSI
is recommended. My M-B expert mechanic says this is too soft and
recommended 35 to 40 PSI (the former for the front wheels the latter
for the rear wheels), and yet another knowledgeable mechanic
recommended low 40s PSI which gives the car a harsh ride in my opinion.
I do not want to cause irregular or premature tire wear and would like
to hear what you all like on your Z rated tires. Thanks, rt


Robert W. Torchia, Ph.D.
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