Topic: More tire pressure will improve soft side-walls?

[aalex]

My OEM tires were V speed. Recently, I swapped to cheaper priced H speed tires, but I noticed they were really "soft" and produced a body-roll feeling when cornering.  

I want to know if there will be an improvement if I increase the tire pressure?

[capriracer]

Yes, but isn't handling one of the reason they use V rated tires?  Did this catch you by surprise?

[morty]

This is exactly the reason we do not recommend installing tires with a lower speed rating than what the car originally came with. Problem is that the tires are a significant part of your suspension and braking. You have downgraded the tire and thus downgraded the suspension of your vehicle. Result is poor handling and diminished braking capability.

You could increase the air pressure, but then you will run the risk of diminished treadlife. If you do increase the pressure be certain not to add too much air as the tire will crown. The result is you will wear the middle of the tire prematurely and you will have a smaller contact patch resulting in poorer braking and handling.

Answer...air pressure will help, but if you want the handling you had before you will need to install the proper tires.



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[citydude]

Very good advice there, Morty.

[aalex]

Thank you for your reponse Morty.  

I am not really a fast driver. Max speed is about 130km/h, which is far from the recommended max speed for H tires. My OEM size is 205/60/15, same as the current tires. My car manual recommends 32psi for the front and 30 for the rear.  

Any suggestion as to how much more psi I should add to improve handling without risking too much of the tread life?

Thank you and any help is appreciated.

[oversteer]

Recommended max isn't really all that relevant, because nobody goes 210km/h sustained for any length of time unless you're in Germany.  The 'H' is really a proxy for other characteristics of the tire e.g. sidewall stiffness.

I think you're going to have to use some trial and error and get to a point where you're comfortable.  You'll also naturally adapt to the tires - same thing happens to me every time I switch to T-rated winters from V-rated summers (stock tires were H-rated).  The car feels like it's all over the road for a couple of days while I adapt my driving.

Start by going 34 front, 32 rear, and then bump it up to 35/33 and so on.  You can also play with the front to back difference and change the driving characteristics that way.  Don't go crazy with increasing the psi, of course.  Once you get to about 36psi you're going to accelerate uneven wear and you definitely don't want to get close to the recommended max (probably 44 psi).

[johngenx]

The speed ratings are misleading.  Mercedes owners make this huge goof all the time.  All models come with at least H-rated tires, and many with V, Z or W.

Then, the owner says "heck, I never drive at 210km/h so, I don't need those H-rated tires."

Well, guess what?  Those tires do lots of things other than drive at 210km/h.  They are more heat resistent at ALL speeds and have stiffer sidewalls.  They handle very differently that those S-rated rim-protectors they bought to replace their premium tires.

Heck, just buy the cheapest tires possible, pump 'em to 44psi and hope for the best.  It's better than driving on bald tires, I guess.

(you should buy V-rated tires...)