gymdoc

Few months back swapped wheels to 20x10.5 and 21x13 with pirelli zero corsa system 295.30.20. and 355.25.21 threadwear 60 ).

Ever since the handling went to absolute ****.. The tail wags bad under hard acceleration above 70mph.. and the suspension behavior is very unpredictable all the time any type road!

Best way I can describe it as if you grab the steering and turn it side to side trying to shake the car while driving!!

So I had the car realigned and it didn't help. Then I did the DSC Sport alignment and that didn't help either. Car has mag ride.. So 2 questions:

1) Anybody else with larger or smaller wheels having the same issue?

2) Anyone know if there is some sort of calibration involved after swapping to different size wheels?

juanvaldez

Why would you want bigger wheels?

gymdoc

Because the stock wheels are a bit too small to fill the wheel well properly and looks retarded not to mention the 4x4 factory look.

mowe

Your tire size in the rear has alot to do with it. It’s tough to keep the cars dynamics with a 21 inch rubber band out back. I don’t have a ton of experience with how to fix that if you want that look though.

cdh027

It just needs to be lowered a tad. I would never go larger wheels.

Donuts

I believe they've maxed out the rear wheel diameter/width from the factory, so going to 21's just doesn't give the design much room to work with. As a matter of fact I'm dropping to 19's so I can get a little more rubber back there.

I remember very well after I put 20x12's on the rear of my cts-v coupe and was cruising the curves in north western Arkansas and the grooves in the roadway nearly tossed me to the ditch several times .. wide rubber looks awesome but matched with a very stiff chassis and suspension you're asking for trouble.

HighBeta

I second this suggestion and opinion. And don't forget to do a complete alignment after you drop it or your handling will suffer (again).

mcoomer

I found this thread while searching for alternate wheel sizes. I too don't like the wheel gap but I don't want to lower the car. I'm looking at going to a 35 up front and 30 on the rear, instead of the OE 30 and 25, to get a slightly taller profile. Looking at Discount it looks like there are a number of options in those sizes. You might try going that route instead of putting a bigger wheel on the car.

gymdoc

Bump.. so there is nobody else here with 20 - 21" wheel combo??

Connman

20-21's on order. 295's & 355's here too.

mallett435

Are you sure they are balanced correctly? I had similar symptoms on my last C7 when changed wheels and doubled check the wheel balancing. The tech said somebody was blind who balanced these wheels the first time. Just a thought before expensive alignment and troubleshooting.

silver74vette

Did you maintain the stock camber settings? If so you may have really loaded the inside section of the tire because of the wider wheels even though you kept the stock aspect ratio on the tires. Do you happen to know what your camber settings are? Large diameter wheels do not like camber.

Thanks, Chris

dollarbill

Don’t swap wheel sizes just lower the car to get the ‘tucked’ look that you are after. My 2c

stevebz06

What tire pressures are you running? I would try experimenting with different pressures, probably trying lower to start with, maybe lowering it in 2 pound increments.

If you're running a lot of negative camber, you might need to take some out.

Basically, you've signed yourself up to be a test pilot, so good luck!

Danosonic

I did the spindles and a definite improvement...I am considering the 20/21 as well on a Z07.

gymdoc

FYI to all.. put the stock wheels and tires back on the car today. and ALL the issues went away.. car rides perfect now..

Guess it doesn't like 21's in the rear. Also for what its worth right before the swap I checked speedo against a gps and display was off by 5 miles when showing 80mph.. actually going 85!!

Now wondering about all of you with smaller wheels.. as to as to whether or not you're having any MRC issues - handling issues??

Bill Dearborn

I think it has more to do with the tires than it does with the wheels. The car doesn't know which wheels are on it. The tires make contact with the road not the wheels. From a tire diameter standpoint you could have run into a problem with hitting the wheel well in the rear maybe the front as well. From a nannie stand point the front to rear diameter ratio is almost exactly what the stock tire ratio is. It sort of sounds to me like you may have problem with the cord in one of the tires. Maybe the cord has become separated. A separated cord can cause the tire to squirm.

Get the tires inspected at the shop where you purchased them. Also you could reinstall the tires and turn off all the nannies by pushing the center button on the console and holding it until you see them shut off. With no TC or Stability Control if the car handling improves there is something the tires are doing to set off the nannies.

Bill

pkincy

It certainly wouldn't be fun to throw away $10k worth of wheels and tires.

gymdoc

That's exactly my dilemma right now... and I hate the stock rims and tires.. so its a double wammy.. I'm F^%ked!

Connman

I'm fitting 20/21's now. They're on the car, but I'm still adjusting suspension, then off for an alignment, but I'll let you know what I feel.
I have the exact same tires as you. PZero Corsa's 295/30/20, 355/25/21.