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Discussion Starter #1 (Edited)
Hi guys,

I have a 03 SMT. I replaced Ksport coilover, front lower 1.5" and rear for 1" lower. I had a set of S-drive Yokohama all around with front are 195/50/15, and rear were 215/40/16. Recently I just replace the rear for Continental ExtremeContact DWS for size 205/45/16. My drive is more acceleration and quieter, but when I'm driving on freeway I'm feeling my car is easier to be wobbling in the back. I tried to lower the tire pressured to 31psi on the rear tires. The wobbling feel less but still there.
My question is should I have a wheel alignment with re-adjust camber? Or can you tell me what's reason make my car wobbling like that?
Thank you for your times.

Best Regards,

Eric

Hi guys,

I replaced a pair new Yokohama S-drive with 205-45-16. I inflated to 32psi. the drive was better than the Continental brand, but still not quite right like before I had 215-40-16. After 1 week drove with that I realize that's the outward of the tire doesn't show any normal wear like usual. I decide to low my tires pressure to 24psi, and it's driving get better. I can see my camber set up is to far out. As you know I replace my coil over ( K-sport) a year ago, and lower it about 1". I think I need a realignment again. But my question is do I need to replace cam bolt pair kit for that? I see those on Tiresrack.
Thank you for your advice.

Eric
 

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Depends what you mean by wobble. It could be that the tires are not balanced correctly (always get a roadforce balance), or it could be that the different characteristics of the different brands you chose for front and rear are causing weird behavior. Very few people run different brands/models of tires on the front vs. the rear....so you're kind of on your own when it comes to the possible negative effects.
 

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Discussion Starter #3
Tires were install by shop ( should be had good balance). Different characteristic is make sense. But can i
do anything to fix that? or nothing can do about that. Thanks. I am appreciated.

Eric
 

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31 PSI?..

I'm at 24 on the rears of mine.. higher and it gets 'Slippery'.. lower and I just start wearing poorly..

But then you are running Miss Matched Tires ( As am I ).. and it's considered a No No

Cap
 

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Tires were install by shop
...most tires are. But not all shops are equal, and neither area are tire balance machines. If it's a wheel imbalance (you feel vibration at 55-60 MPH, and 75-80MPH, find a roadforce balance machine in your area and have them balance the wheels.

If it's some other sort of wobble (you still haven't described this more in detail), and it only started when you had the new tires mounted try pulling the wheels and remounting them, torquing them down correctly. And if finally that doesn't work, then I have to think it's your mismatched brands of tires.
 

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From reading your post carefully, what comes to mind is sidewall flex. Since the sidewalls are so much different on different brands of tires, that may be what you are perceiving as a wobble. Especially if the back tires have a much softer sidewall than the front, and what you previously had on the back.
 

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Discussion Starter #8
I didn't have corner balance when the coil over were install. I did wheel alignment only, actually I don't know what's corner balance mean.
I don't have any vibration from low speed to high speed about 75 MPH. Only unpredictable wobbling on freeway. It's start just after I installed new tires. The car can move to right or left a little bit when i getting faster on freeway, steering wheel feel lighter than before, but no vibration or shaking. Thanks.

Eric
 

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Discussion Starter #9
31 PSI?..

I'm at 24 on the rears of mine.. higher and it gets 'Slippery'.. lower and I just start wearing poorly..

But then you are running Miss Matched Tires ( As am I ).. and it's considered a No No

Cap
Do you really have only 24 psi on your rear? Is it consider too low pressure for rear tires? with spec for 03 model is 215/45/16 for 32 psi. I think go down to 205/45/16, i can go for 31 psi. Do you think it's still too high for that size? or OK? Thanks.

Eric
 

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Discussion Starter #10
From reading your post carefully, what comes to mind is sidewall flex. Since the sidewalls are so much different on different brands of tires, that may be what you are perceiving as a wobble. Especially if the back tires have a much softer sidewall than the front, and what you previously had on the back.
Since I install the new tires, my car acceleration a lot better, I think is the weight of that tire only 17 lbs per tire, replaced other one was 19 lbs per tire. The car run softer than before, maybe the ratio go up to 45%. That's make me feel your theory make sense. Thank you so much.

Eric
 

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Since I install the new tires, my car acceleration a lot better, I think is the weight of that tire only 17 lbs per tire, replaced other one was 19 lbs per tire. The car run softer than before, maybe the ratio go up to 45%. That's make me feel your theory make sense. Thank you so much.

Eric
If what I'm seeing on Tire Rack is correct, you actually went to a tire that has a larger diameter than what was on the back of the car. That means a taller sidewall. They show the S-drive at 22.7 diameter, and the DWS at 23.3 diameter.

They also show that the original size of tire was 215/45/16 at about 23.5 diameter. If the S-Drive was 215/40/16 then it was about an inch smaller in diameter than what came on the car.

The taller, softer sidewall may be what you're feeling. I'm not sure why you would have better acceleration unless it is simply that every revolution that the tire makes will carry you farther down the road. I doubt that the 2lb. difference in weight per tire would be enough to notice.

JMHO
 

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Corner balancing equalizes the weight on the wheels; something that should always be done when insatlling coilovers (in my opinion).
I'm just curious. If a car came out of the factory with the weight close to being corner balanced, and then you put a driver in the car, would that not change everything? Especially if it was a fat driver.

So if I'm a fat driver, do I need to find a fat passenger to equal things out? :lol:

I can see how it probably wouldn't make much difference on a two ton Caddy, but might make a great difference on a light sports car.

I never really thought about this before.
 

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Discussion Starter #16
If the coilovers were installed significantly earlier than the tires, corner balance is not your problem. Your original post could be interpreted to mean that all the work was done at the same time.

If the weight on the wheels is not equal left/right, the car will behave like a table with one short leg. A particularly bad situation is to have too little weight on diagonally opposite wheels. Corner balancing equalizes the weight on the wheels; something that should always be done when insatlling coilovers (in my opinion).

If your problem began with the new tires, then I agree with tecaholic2. You'll either need to drive very carefully or put matching tires all around.
The coil-over was installed a year ago, with all around S-drive Yokohama, front is 195/50/15 and rear were 215/40/16. The drive was fine, very bumpy. just week ago were replace by 205/45/16 DWS. since then, the drive feel a lots softer, a lots less bumpy ( I'm very happy about that), cornering traction feel OK ( a little bit softer), start from low speed at low RPM feel more power to moved the car than the S-drive before. So far I'm very happy with those character. But only big problem is on freeway, the rear feel too light and easy to be wobble by the wind or a little uneven surface. I also think that the set up of the MRS is rear tire have to at least 2 size wider than the front, isn't it? Should I change the front to 185/55/15? I feel the rear now are less grip than the front. I' very appreciated with your advises. Thank you so much.

Eric
 

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Discussion Starter #18
The exact size (185/55 vs 195/50) isn't so important as having the same type of tire all the way around.
It sounds like your new tires are more "squishy" (softer sidewall) than the old ones.
I agree with you. Thank you.
 

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But only big problem is on freeway, the rear feel too light and easy to be wobble by the wind or a little uneven surface. Eric
From what I'm seeing looking at Tire rack, the S-Drive's that you had on the back are a dirrectional tire with an UTQG rating of 300. That basically means they are pretty soft rubber, sticky, but will wear fairly quick.

The Continental DWS is an all-season asymmetrical design with an UTQG rating of 540. That means it is a lot harder rubber designed for high mileage highway use.

If what I'm seeing on Tire Rack is correct, You have very different tires on the front and back of your car. The tread pattern design also looks completely different. This would probably be one of the worst mismatches possible, and could be dangerous. Hopefully what I'm seeing isn't correct.

Read what it says on the side of the tires on the front and back of your car. If what I'm seeing is correct, the tires on the back (DWS) will have "Outside" stamped on the sidewall. That means they are an asymmetrical tire.

The tires on the front will have an arrow showing the direction that they are to rotate. This means they are a directional tire.

If you do indeed see these markings on the tire you should be very careful driving the car.
 

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Discussion Starter #20
From what I'm seeing looking at Tire rack, the S-Drive's that you had on the back are a dirrectional tire with an UTQG rating of 300. That basically means they are pretty soft rubber, sticky, but will wear fairly quick.

The Continental DWS is an all-season asymmetrical design with an UTQG rating of 540. That means it is a lot harder rubber designed for high mileage highway use.

If what I'm seeing on Tire Rack is correct, You have very different tires on the front and back of your car. The tread pattern design also looks completely different. This would probably be one of the worst mismatches possible, and could be dangerous. Hopefully what I'm seeing isn't correct.

Read what it says on the side of the tires on the front and back of your car. If what I'm seeing is correct, the tires on the back (DWS) will have "Outside" stamped on the sidewall. That means they are an asymmetrical tire.

The tires on the front will have an arrow showing the direction that they are to rotate. This means they are a directional tire.

If you do indeed see these markings on the tire you should be very careful driving the car.
You absolutely correct. They are exactly as you said. I made mistake to buy a mismatch tires. Thank you for your advice. I think soon I have to replace them.

Eric
 
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