a4avant99

Newly purchased car. Tires are half worn. Found a tire with a nail hole that has been patched, which is probably causing a vibration on high ways.

Thinking to replace only two tires to put in front. My imagination is to put slightly lower pressure (e.g. 2psi lower than recommended) in news front tires, and slightly higher pressure (e.g. 2psi higher than recommended) in rear old tires to compensate the difference in diameter.

Any idea?

Thanks

4Driver4

This is bad logic. Real tires don't "blow up" the way they do in cartoons.

Buy four tires.

jseklund

Second the 4 new tire recommendation. If you can't do all 4 at once because of cost, do two and replace the other two within a month or so. It's not great for the transmission to have different tires from either tread pattern or wear perspectives.

I might suggest the Continental DWS tires - they are a little cheaper than the Michelins but they have really made a difference in the way my car drives/feels/sounds and they held up over 40,000 miles for me with the S still showing. I just replaced all 4 though because I drove over something that punctured 1 and damaged the inside of another.

I am not a fan of Continental brand tires - they never last - so the fact that I just put a second pair of their DWS tires on my car says something.

Just Me

The air pressure idea wont work, btu there is no reason you cannot have 2 matched new tires int eh rear and 2 matched older tires in the front. The OD is close enough, and this is done all the time. Note what i said - backwards of what many will think. the safer, more benign handling is under steer - newer in the rear.

A Tire with a proper patch or mushroom plug ( my personal fav) will not vibrate any more than a new one.

jseklund

I don't disagree with Just Me - he may be right. All the tire guys tell you that you must replace all 4 because of the quattro, but this last time I did 2 in the front and then 2 in the rear. The reason I didn't do as Just me suggested (new in the rear) is that I had an alignment issue that wore down the edge of one of my tires and the tread was worn down too badly - so I decided to leave it on the rear.

Near the end, I noticed some slipping in the rear on take off, esp. around turns. It was definately not good for the transmission, but this may not have been as much a matter of the tire differences as much as the one tire was unnaturally worn.

4Driver4

This seems to be the new conventional wisdom. I don't subscribe, myself.
Who says understeer is less dangerous? When do you rotate tires?

OGBULLYLOCDAWG

If you can't bite the bullet for a new set of 4 right now, see if you can source 2 matching used tires from a local tireshop installed for like $80-- tread life would likely be closer to the remaining ones.

SloopJohnB@mac.com

I've replaced two tires on an axle with the other axle tires still at 6-9/32".
I've also replaced one tire on an axle with the other tire at 9/32". Doesn't seem to make a long-term difference (>150K miles on 2K4.2A6).

However, I wouldn't do it with any tire other than the tire(s) that are already on the car.

I've also staggered tire inflation pressures to equalize tire wear across the tread...inflate your tires about 5 psi above manufacturer's recommended inflation (not to exceed the psi max on the tire sidewall!!) and watch for wear in the center of the tread. On my 2K4.2 and 02S6 I run 36 psi rear and 38-40 psi front with 255/40ZR-17 tires...with five people and luggage I run tire pressures up to 40 front and rear. You can adjust/stagger tire pressure front to rear to modify understeer/oversteer somewhat as long as you don't lower pressures so far that you get tread rollover on sidewall. TireRack among others recommends 6 psi cold increase over vehicle manufacturer's recommended pressure setting if you drive extensively and over 45mph...LOL!

http://www.tirerack.com/tires/tirete...jsp?techid=147

The upper level performance tires have little triangle molded into the tread near the sidewall that can be used to indicate how far/much of the tread you're using....if the wear area of the tread is just touching the triangle your tire pressures are ok for the cornering forces you're generating. If the triangle is worn, either slow down in the corners or inflate your tires another five psi!

Although Yokohama says THEIR triangles are: Triangle marks ( ▲ ) on the sidewall show the tread groove position of the “tread wear indicators”, the “tread wear indicators” represent 1.6mm of remaining tread depth at which time the tyre should be replaced.

bigdadi

Find your matched used tires ...this way you can replace only the bad one
http://www.bestusedtires.com/index-exec/

Or Tirerack offers to shave your 2 new tires to match your old.

SloopJohnB@mac.com

Not feeling the love with 255/40ZR17 Dunlop SP9000 used tires.
And TireRack doesn't sell them anymore. They're still available in the UK, though.
I have a feeling the relatively old tire design doesn't match with Dunlop's marketing plan plus I realize this model tire must have had LOTS of warranty problems judging from the number of tires I've had to have replaced under warranty (Discount Tire Direct) for sidewall blisters/delamination.