Tire inflation pressures

[Albert-230SL]

Hi Group,

Our Owner's manual recommends the following tire inflation pressures (Cold tires, Kg/cm2):

Front: 1.8 [26 pounds/in2]
Rear: 2.2 [31]

I tested some different tire pressures in my car (Michelin MXV-P radial tubeless tires, original size 185 HR14), and I found the best compromise comfort/handling with:

Front: 2.15 [30]
Rear: 2.5 [36]

which is very close to what the new "Michelin Passion" site, recommends. See: http://www.michelin-passion.com/passion/collection/en/cr_pneu_trs_result.jsp?lang=EN&codeRubrique=8&Marque=126&Modele=1095&Annee=97

Front: 2.2 [31]
Rear: 2.6 [37]

(Note: Although it seems that their tire type for Pagoda is the Michelin XAS, if you go to: http://www.michelin-passion.com/passion/front/templates/affich.jsp?codeRubrique=40&lang=EN&dimension=1  you will see that in the 185 HR14 size, the tire actually is the MXV-P, an evolution of the XAS, which is TL (= Tubeless))

What tire pressures are you using? Why this big increase in the recommended pressure in comparison with the Owner's manual?... maybe the difference in the tire construction?

Note: Home page of Michelin Passion is: http://www.michelin-passion.com/passion/home/en/home.jsp?lang=EN

Regards,

Albert de la Torre Chavalera
Barcelona (Catalunya/Spain)
Feb.'64 230 SL Euro 113042-10-002432

[George Davis]

I use the following tire pressures:

front: 28 psi (2.0 kg/cm2)
rear: 30 psi (2.1 kg/cm2)

My priority is ride comfort.  I find this combination gives good comfort with improved steering response.  But this is the US, and I seldom drive faster than 70 mph (120 kph).  At higher speeds, I'd probably use higher pressures.  If I ever autocross the car, I will start out with pressures of 45 psi (3.0 kg/cm2).

This is just conjecture, but I would guess the recent higher pressure recommendations are mostly related to tire warranty and long tread life considerations.  Higher pressures reduce flexing, which should help make the tire last for 60,000 or 80,000 miles.

George Davis
'69 280 SL Euro manual

[Albert-230SL]

quote:Originally posted by George Davis

I use the following tire pressures:

front: 28 psi (2.0 kg/cm2)
rear: 30 psi (2.1 kg/cm2)

My priority is ride comfort.  I find this combination gives good comfort with improved steering response...  

George Davis
'69 280 SL Euro manual

Hi George,

Just a thought:
your tire pressures, in comparison with the owner's manual, are +0.2 [+3 pounds] in the front tires and -0.1 [-1.5 pounds] in the rear. I think this combination affects the behaviour of the car on corners, increasing oversteer (and you could experience that on a twisty road, even within the speed limits!). I would go to 2.4 kg/cm2 [34 pounds] in the rear tires in order to keep the original balance* of the car... and believe me, even with 2.5 [35 pounds] in the rear tires, it's still very comfortable.

*If Mr. Uhlenhaut and his team of engineers chose that combination of tire pressures (rear tires: 0.4 kg/cm2 [5.5 pounds] more than front tires)... in a car where most of the weight is in the front axle... there should be some good reason for it.

Regards,

Albert de la Torre Chavalera
Barcelona (Catalunya/Spain)
Feb.'64 230 SL Euro 113042-10-002432

[George Davis]

Albert,

good point about maintaining the car's balance.  I'll try 2.4 [34]in the rears and see how it goes.  Perhaps I'll try autocrossing the car at one of the local MBCA chapter events one of these days just to see how various tire pressures affect handling.  I'd like to try the car on a racetrack, but without a roll bar the local track won't allow it.

George Davis
'69 280 SL Euro manual