As you may have seen on another thread, I got rid of my GY F1 Runflats at 22K miles and replaced them with Sumitomo HTR Z II's (non runflats) after much deliberation. Spent most of the day yesterday at the dealer while they mounted them up, balanced and torqued (by manual torque wrench - @125 instead of just an air wrench).

Initial impressions:

Positive:
1. They're VERY quiet. it's like being in my wife's Riviera... just floating along.
2. Much smoother ride (with my Z51 package I think this is a good matchup), particularly over little road-patch bumps which seem to be everywhere in Illinois.
3. After cookin through several turns, backroads and interstate entrance/exit ramps (that I was very familiar with and knew what the F1's would do with them), I have to say my EARLY impressions is that the Sumi's are a bit softer... not to the "mushy" point, but they don't seem to have the schtick and rigidity that the F1s did. Could be I'm running only 32 lbs in the Sumi's and I always ran 34 lbs (cold) in the F1s.
4. Acceleration from a dead stop has produced a bit more grip and definately less sideways tail-walk when stepping on it hard in 1st or 2nd gear. The F1s were nearly slick though. Naturally, in 1st you have to feed the power on more gently, but you can hammer 2nd gear and she sticks pretty well. Had one with some wheel hop but that was my launch... not the car or tire's fault. I've yet to really pound it really hard...

Negatives:
1. The corners, where the sidewall meets the top meat of the tire, is much more rounded than the "squared off" F1. This means that the tires, after coming up my country lane, look dirty and as if I haven't washed it in a week.... even though I have tire sheen and am almost **** about clean tires. I MUCH preferred the sharp 90 degree angle of the F1 over the rounded, almost go-kartish look I think they give my FRC now. And I definately am going to have a problem with the dirt-always-visible thing on the rounded corners of the tires. This aspect of them I really dislike.
2. From 60 to 80 there was a very healthy shimmy & shake to my front -- where the F1s had never had ANY kind of shimmy (at all speeds). Call me a grouch, but I cannot tolerate a shimmy in my front end -- and never have been able to. This was severe enough it feels like it's hurting my tie rods. At 70 it's so noticeable you have to drop down below 60 or get it well up above 80 til it goes away. I know this is a balance thing... so I took it back this morning to the dealership. They checked the front's balance again. Dead on - need no weights. However, with their Hunter machine (6SP9700 - new and state of the art), it showed sidewall "Road Force" imbalance on both front tires... 22 lbs on the passenger's side, 28 lbs on the driver's side. According to the car dealer, about 12 to 14 is about as high as you want to "allow" for tire road force imperfections.

We hung them on the car again, torqed them up and I drove it home, shake and all. I called Tire Rack. They said they needed their customer service folks to chat with the dealership. I gave them the dealer's number and was told I'd be called back right away. That was over 4 hours ago. It would now be too late in the day to expect them to get 2 replacements shipped to me... but at this point I can only HOPE Tire Rack will stand good on the warranty. Which means, IF I get a call tomorrow morning, the earliest I could expect to see replacement tires drop shipped to the dealer would be 2 or 3 days from now... then another vacation day lost to going back to the dealer to mount up the replacements. Not to mention the $255 I paid to mount the 4 tires... and now will have at least half that $$ again invested to swap out the tires next week. We didn't check the road force numbers on the rears... at this point I'm of weak faith for the quality of these tires. Next week when I'm in there we'll take off the rears and put them on the machine. If THEY're also unacceptable, I'm going to try to return all 4 and get my money back.

What I would like to see happen is 1) they overnight the two front replacements, 2) reimburse me for half of the total installation, 3) cover any additional costs associated with taking off the rears and checking them for road force imbalances. :smash: And I want my 2 vacation days back. :smash: :jester

For that reason, I've decided not to go to the track tonight. She's not 100% shimmy-wise, front tires might be unstable at race speeds, and I don't want to use up the back tires in the event I'm going to end up sending them back.

I'll post a follow-up when I hear back from the Tire Rack and we see what "shakes" out (sorry, couldn't resist). Until then, my daily driver is just gonna shake. :crazy:



[Modified by Gunny, 6:26 PM 4/10/2002]

 

I have been thinking about getting these tires myself. Thanks for the write up

 

Hey Now:
Thanks for an honest write up :cheers: But check your torque settings. Should be 100. :yesnod:

 

If you wanted a cheap good tire, you should have went the Kumho route. I have 275-35-18 Kumho 712's all the way around on my Camaro. I love them! My sister has 225-50-16 Kumho 712's all the way around on her Grand Am. She will tell you that they are not much in the snow, but other then that are awsome! I know when it is time to replace my runcraps I am going to the 712's without a doubt. I will do 265-40-17 in the front, and 275-35-18 in the rear. This will still give you that staggered look and you loose about a total of .5-1" of total sidewall height. You will also gain a shade of tread width on the back, and about an inch up front. The other cool part is that you can get all four in this size for about $580.00 shipped!!! That to me is an outstanding deal. If you have to send them back to tirerack, see if you can exchange into these. :cheers: :cheers:

 

Just an update...

I patiently waited to hear back from the Tire Rack all day yesterday. I've even given them my 1-800 # and I'll gladly eat the toll charges.

Didn't hear a peep from them. I guess I'll have to call them again... hope this doesn't get ugly. But I'm not going to drive a C5 on inferior tires, beating up my tie rods, for very long before taking action. I've got a 3pm tee time with my corporate attorney... and if Tire Rack hasn't taken action by then, you can bet what the lawyer and I are going to talk about. :mad

 

good luck , the names just sounds cheap though IMO.

 

Frankly, having ANYthing rice on my car gives me the heebie jeebies :)

I called Tire Rack this morning and they said 2 new tires shipped yesterday. Update to follow after the new ones are installed (I guess, next week). Stay tuned for the continuing saga.... :)