[wang970305]

I just swapped from stock ss setup to ss-1le rims and tires.
when the car gets on uneven road, it would swirl a bit. I am not sure its just because the front tires are much wider now or traction control came in. did not see the TC light come on tho.
Also find out the speed is actually faster than my GPS, about 3-4 MPH.

I tried to do some research to see if ECM tire ratio needs to be updated with these different size of setup. please sharing your experience and new ratio numbers

[bishopts]

I know wider tires tend to show you how bad the roads really are, but ib wouldn't think it would be that big of a difference from ss wheels to 1le wheels

[Ray3768]

Are you running the factory issued GY SC3's? I noticed that the car seemed to be a bit squirrely for the very brief time I ran the SC3's. Chalked it up to the tires not being broken in yet and shitty South Jersey roads. The situation improved dramatically two days later when I swapped the SC3's for Continental DWS06+. Not a fair comparison though, the Conti's are not as wide even though they are the same size and certainly not the same rubber compound.

Regarding the speedometer, mine is reading about 1 MPH higher at 73 MPH, so I'm slowly racking up more miles. I rely on the factory warranty, so a tune is not in the cards for a few more years. I intend to try some different tire sizes once these Conti's need replacement that will get me closer to the original SS tire height.

Anyway, enjoy your 1LE wheels. They make a noticeable difference in traction, both acceleration and cornering, and they look badass. The car should have come this way from the factory.

-Ray

[2SS Capt]

Originally Posted by bishopts

I know wider tires tend to show you how bad the roads really are, but ib wouldn't think it would be that big of a difference from ss wheels to 1le wheels

The 1LE tires are lower aspect ratio so the wheel is spinning slightly faster than the stock SS wheel at the same speed...

[bishopts]

Originally Posted by 2SS Capt

The 1LE tires are lower aspect ratio so the wheel is spinning slightly faster than the stock SS wheel at the same speed...

What does that have to do with the FEEL of the car on uneven roads?

[CamaroDreams76]

Its called tram lining. The car follows the groves in the road and creates an uneven feeling. Its from a multitude of things. The front tires being much wider and the GYSC3s being such a grippy tire.

My 5th gen did it with the GY SC2s and got better with the Michelin Pilot Super Sports and 4S. My wife's 22 1LE tram lines better bad.

[2SS Capt]

Originally Posted by bishopts

What does that have to do with the FEEL of the car on uneven roads?

Wasn't the OP asking about the speedo being off?

[arpad_m]

When upgrading to wider tires for my new SS 1LE wheels, I tried to stay close to the original SS heights and ratios, because who knows how many places GM wired in stock tire sizes.

WIth the slight difference I introduced by switching to 275/35/20 fronts and 315/30/20 rears, my speedo is now 100% spot on, I've tested it with several police radars (with stock sizes, the car read a bit higher than actual speeds, probably as a safety margin). Practically zero tramlining to speak of with the Michelin PS4S, although I know other tires are more prone to this.

If OP wants to reprogram the tire size, most midrange and up scan tools can do it, and they only require the new tire diameters, which one can calculate at https://tiresize.com/comparison. Again, I'm not 100% sure this is all it takes to recalibrate the car for SS 1LE wheel/tire sizes, but let's hope so.

[bishopts]

Originally Posted by 2SS Capt

Wasn't the OP asking about the speedo being off?

He was. But also about a "swirl" feeling. I don't really know what a swirl feels like but i do know wider tires follow imperfections in the road more than narrow.
I just wouldn't think 245s compared to 275s would really feel that different. But maybe they do.

[Val Walkinshaw]

Tramlining comes to my mind as well. I notice it on all grooved roads. Doesn't matter if it's my SC3's or the MPS4S. It feels like the car is hunting in-between the grooves. Once on a less traveled road or more recently repaved the "hunting" between grooves goes away. I noticed it to be much worse and twitchy with more aggressive camber but even with "street" settings tramlining has always been a thing with 275 and greater up front.

I stay the hell out of lanes that semi's travel in because of tramlining.

[Bad Anvil Garage]

Originally Posted by arpad_m

With the slight difference I introduced by switching to 275/35/20 fronts and 315/30/20 rears, my speedo is now 100% spot on, I've tested it with several police radars (with stock sizes, the car read a bit higher than actual speeds, probably as a safety margin). Practically zero tramlining to speak of with the Michelin PS4S, although I know other tires are more prone to this.

^^^ THIS

I used a tire calculator online to match the diameters from1LE wheel/tire to OEM SS tire specs. This is the correct formula above. You have to have as close to the same overall diameter for the speedo to be correct without reprogramming.

[wang970305]

Originally Posted by bishopts

He was. But also about a "swirl" feeling. I don't really know what a swirl feels like but i do know wider tires follow imperfections in the road more than narrow.
I just wouldn't think 245s compared to 275s would really feel that different. But maybe they do.

I can def feel the steering wheel starts to turn itself when the road is shitty, it is a huge difference

[wang970305]

I talked to my tuner about the tires, he adjusted my speedo and now its reading accurate

[FlukeSS]

Originally Posted by CamaroDreams76

Its called tram lining. The car follows the groves in the road and creates an uneven feeling. Its from a multitude of things. The front tires being much wider and the GYSC3s being such a grippy tire.

My 5th gen did it with the GY SC2s and got better with the Michelin Pilot Super Sports and 4S. My wife's 22 1LE tram lines better bad.

^

My car did it as well when I upgraded non 1LE wheel/tires to 1LE spec.

Now running 285/35R20 front and 305/35R20 rears.

Blame the road not the tire honestly... its a scary feeling though the first time.

I run into tramming when in construction zones most of the time.

Originally Posted by wang970305

I can def feel the steering wheel starts to turn itself when the road is shitty, it is a huge difference

Ya the best way to describe it is: Torque Roll as if you are running on drag slicks. The car tends to sway due to softer rubber, however in this case its the ruts in the road you are feeling, which can make the car sway 2-4 feet left or right at times. Just have to be careful and ready for it.