My Gs 300 came with 18" rims and 245/40 dunlop tires. Since I got this car used(11k) I plan to replace them in about 4k miles. Simply put, I want a softer, quieter tire. The lead service rep at a lexus dealer to me that changing to a 245/45 tire would throw off my speedometer and would not make much difference in ride quality. Is he right? I do like the looks of the 245/40's but they just seem too rough. Is there another brand of tire that is better than the dunlops? Thanks for any advice you can give me.

 

it's not the size of the tire that is causing the ride but the type of tire. I'm assuming that you are running the stock Dunlop runflats. Switching to a non-runflat tire will give you a much smoother ride. Just do a search on runflat tires and you will find a number of threads about this topic. Just about everyone who has swapped out their runflats for regular tires swear that they will never go back.

 

I just took for granted that the dunlops on my car(purchased used) were regular tires NOT runflats because my car is 2WD and not AWD. However, they are runflats!! Why would people put runflats on a 2WD drive car? Anyway, it was idiotic of me not to check closely and now I plan to replace these runflat tires soon.

 

Runflats are standard on the '06 GS because the spare tire is optional. Unless the car was ordered with the optional spare, you probably don't have one.

 

245/45 is out of spec, so he is right about that.

The Dunlop runflats are awful (I had the 17'' ones and they still were bad).
Just make sure you have a spare before you ditch them.

 

I do have a spare tire...so I will definately dump the runflats by the end of the week. Thanks again and if you have any good suggestion as to what type of 245/40 tire I should get let me know.

 

Given your original statement in looking for softer, quieter ride, I'm assuming that maximum performance handling is of a lesser concern. That probably rules out the Michelin PS2s which are great performers but a little stiff for my taste. I just put a set of Toyo T1Rs on my GS (just this morning in fact ) and definately smoother than the Bridgestone runflats I had before.

I also have a set of Toyo Proxy4s on my '04 GS and they are a little smoother than the T1Rs (better all-season tires than the T1Rs)

But then again, I still have Dunlop runflats on my SC430 and never thought that those or the Bridgestones on the GS were all that bad to begin with.

 

Go with goodyear assuarance comfertred tires, the quietest tire in the world and treadwear up to 80,000 miles but it may reduce your gas mileage a bit cuz of the weight. just fyi.

 

Question for any tire buffs...A friend of mine has a connection at a tire store. He can get me 245/40 18" size tires in these two brands for a really good deal. The brands are Cooper or Toyo proxy 4s. I know nothing about tires. My only reason for doing this(as previously stated) is to get rid of the runflats into something softer,smoother. The Coopers are $600 installed(balanced etc) and the Toyo's are $640. He said both tire are good and should last about 20k-30k miles. Any opinions?

 

I just purchased a new set of wheels and tires. Tires are Falken Ziex ZE-512 . They are
245/40 18's and they were $530 Installed. Great tire, aggressive look, dead quiet, and great ride quality. Here is a link to see them. Falken Tire

 

I got my set of Toyo proxy 4's put on today and they are much better than the dunlop runflats that were previously on my car. Still, it does take some getting used to going from a 16'' tire on my old 99 gs 300 to a 18'' wheel on my 2006 gs 300.