Tyre Pressures

[portzy]

Yes, I know its been flogged to death before but I think this may be a bit different. The ingredients are as follows. I've just adopted, or rather modified, my setup to an offset one as in, 7.5J 225/45.17" front and 8.5j 245/40.17" rear. The car only ever has me or me plus another single passenger in it. As everyone knows, in the petrol cap flap there is a selection of pressures given depending on load set against maximum speed. I had at 1st, i.e. 13 months ago, the pull left problem so I ran the fronts at maximum pressure in the belief that this would help, it didnt, but the pull left was cured by the dealer but I left the pressure at maximum. I also ran the rears at maximum pressure, believing I was staying in balance? and that is the situation ever since last June. Still awake?.

So, what I'm proposing is to lower the fronts to the minimum but, will I notice heavier or different steering characteristics?, tyre wear is not a worry by the way. If I do lower the fronts is it unwise to keep the rears at maximum or should they be at minimum also. I keep saying minimum, I believe the correct terminology is comfort. The actual pressures to use? i've manged to suss from the dealer but, its the mix I'm usure about.

Any and all thoughts welcome

 

[C240Sport97]

I have factory AMGs on my C240 W202 with the same staggered sizes as yours. I found the ride too hard, so I started messing around with the pressures. No luck. If anything, the ride was worse on lower pressures. So I called MB who told me that the pressures in the petrol flap covered ALL tyre configurations. I changed the pressures back to those in the petrol flap. No real change. UNTIL I changed from Conti SportContacts to Pirelli P Zero Rossos -- much better ride, sharper steering and much improved handling.

 

[portzy]

C240Sport97, thanks, Mmnnn, I suppose I should have added " by the way, the tyres are Michelin Pilot Sport" do you know of any problems with those?, I thought they were "top hole" so to speak. Thats what I had from new and before the mod.

 

[Tigger]

Allow me to confuse matters even more then Hehehehe

I have 18" Brabus Monoblock VI with Michelin Pilot Sport tyres 235/40ZR18 on the front and 265/35/ZR18 on the rears.

My fuel filler flap now has a Brabus sticker inside it with cold inflation pressures as follows:

Front: 2.4 Bar = 35 psi

Rear: 2.8 Bar = 40 psi

Needless to say the ride is purrrrfect!

 

[gklau]

Mine came with the sports package with the same tyre sizes as yours, and with Michelin Pilot Sports as well. My filler flap says:

30 psi - fronts
33 psi - rears

At most, I carry one passenger as well. When I have a fully loaded up car I increase the pressures to:

33 psi - fronts
36 psi - rears

Hope this helps!

 

[Shude]

My fuel filler flap now has a Brabus sticker inside it with cold inflation pressures as follows:

Front: 2.4 Bar = 35 psi

Rear: 2.8 Bar = 40 psi

Is that for just one passenger or for a full car?

 

[Tigger]

Is that for just one passenger or for a full car?

Those are the only figures quoted. I'll post a picture of the sticker later.

Personally, I think with lower profile tyres you should really increase the pressures a little otherwise if you hit a bump or pothole you risk impacting the sidewall resulting in a bulge (speaking from experience).

 

[C240Sport97]

Maybe MB meant ALL tyre and wheel configurations available from MB.

However, Brabus must know what they are talking about.

My fuel filler flap now has a Brabus sticker inside it with cold inflation pressures as follows:

 

[Shude]

Maybe MB meant ALL tyre and wheel configurations available from MB.

Well if it means anything ALL w202 models come with the same sticker on the inside of the filler cap, so those with 15" steels and those with staggered 17" AMG rims all have the same tyre pressures. I've been trying to picture it in my head but if you think about it, if you compare a 15" steel wheel to a 17" alloy the larger diameter wheel is usually wider as well, the rolling radius of the wheel/tyre combo will be very similar so maybe the amount of air in the tyre is very similar regardless of the diameter size etc because the width is increased too.

 

[C240Sport97]

I think of it as the suspension systems being designed to rest and perform best at a certain pressure/load, instead of amount of air

Since weight is spread around more surface area on wider tyres, but these have lower profile .. so that actual contact pressure/load for a wider lower profile tyre is roughly the same as a narrower higher profile tyre, both tyres being of the same air pressure

not very scientific at all, mere conjecture.

Well if it means anything ALL w202 models come with the same sticker on the inside of the filler cap, so those with 15" steels and those with staggered 17" AMG rims all have the same tyre pressures. I've been trying to picture it in my head but if you think about it, if you compare a 15" steel wheel to a 17" alloy the larger diameter wheel is usually wider as well, the rolling radius of the wheel/tyre combo will be very similar so maybe the amount of air in the tyre is very similar regardless of the diameter size etc because the width is increased too.

 

[portzy]

Thanks for that guys. I spent a few hours last night thinking about and experimenting with all the various suggestions and pressures and finally settled, for the time being who knows, 36 PSI front and rear. I did notice a difference with the wider tyres at 1st anyway so maybe things were not quite as scientific as I had thought. All ends up though, i'm well suited now cheers.