# out of control



## butchjr15 (Nov 29, 2009)

hey everyone. i just put new tires on the rear. they are Sumitomo HTR Z II 275/35 18s. on 9inch rims. the prob is any speed over 70mph the car feels so loose and out of control. almost like i had a flat or the side walls were flexing to much. it was floating all over the road. felt like i had 5inch side walls. very scary feeling. is it because there new or what? I couldnt go over 80. thanks for the help and the input.


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## Mongoose (Jun 17, 2009)

maybe the tires arn't balanced right


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## Lautinjr (Mar 27, 2010)

butchjr15 said:


> hey everyone. i just put new tires on the rear. they are Sumitomo HTR Z II 275/35 18s. on 9inch rims. the prob is any speed over 70mph the car feels so loose and out of control. almost like i had a flat or the side walls were flexing to much. it was floating all over the road. felt like i had 5inch side walls. very scary feeling. is it because there new or what? I couldnt go over 80. thanks for the help and the input.


Check the pressure and balance maybe. I just installed 2 P265/35r18 Sumi HTR Z II's on the rear last wensday and can tell you they are stable at 115mph.


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## jetstang (Nov 5, 2008)

Even though they are runflat tires, you still have to put air in them..
Something is definately wrong, check the tire pressures.


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## Nate (Mar 17, 2010)

could it be caused by the camber/caster not being set right?


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## svede1212 (Nov 1, 2005)

Check your front radius rod bushings. One may be blown


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## GM4life (Mar 18, 2007)

:agree

If you don't know what they are they look like this:

The stock on is the one on the left:









Are located here:



















I since torque stripped my bolts after this picture, so I know if the bolts have loosend.


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## butchjr15 (Nov 29, 2009)

i put the max psi in them 51. could it be the tire is to wide for the rims? rims are 9 tires are 275. it doesnt feel like a balancing issue it sways not a shake. what a PITA Anyone wanna buy them? less then 25 miles on them!


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## Lautinjr (Mar 27, 2010)

butchjr15 said:


> i put the max psi in them 51. could it be the tire is to wide for the rims? rims are 9 tires are 275. it doesnt feel like a balancing issue it sways not a shake. what a PITA Anyone wanna buy them? less then 25 miles on them!


More like the air pressure you should never max a tire The GTO requires 35 to 39 psi in rear depending on load and you have a oversized tire which means more air mass so it will require less pressure to support the same wieght. I run 35 in mine and don't carry any more then factory load and a baby seat. if you had to air your tires past 39psi on the GTO to support the wieght that would mean the suspension would be overloaded to.


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## jetstang (Nov 5, 2008)

Vettes run 9.5 inch rims with 275s, so you are good. 51 psi would make it ride like a rock, stiff, but sure footed. You have something broke in your suspension as others are stating. Be carefull, the car should never feel that bad. I drive my 93 POS Astro van 85 mph all day long, a little sketchy, but not out of control.


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## 87GN06GTO07IRL (Aug 10, 2009)

275's should be mounted on a 9-11 inch wheel so your good there. 51 psi is way to much. I like 32. 35 made my car ride like a brick.


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