20 inch wheels upfront C7

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Nov 12, 2019 | 04:16 PM

Ladyk

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20 inch wheels upfront C7

I would like to use 285/30/20 tires and wheels upfront on my 2017 z51 vette what kind of issues would this present? Thanks in advance HH

Nov 12, 2019 | 06:06 PM

JMII

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From: Margate, FL

1) rubbing
2) depending on the size of the rear tire the traction control system may not work properly

Nov 13, 2019 | 07:09 PM

Ladyk

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I would like to use 285/30/20 on all 4 wheels will they rub on the front?

Will the 79 offset work on the front wheels?

Last edited by Steve Garrett; Nov 13, 2019 at 07:12 PM. Reason: Merged Posts

Nov 14, 2019 | 12:58 PM

JMII

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From: Margate, FL

I assume they will rub. Since this is the stock rear wheel you can test the fitment yourself but just swapping them. I do not think the computer will be happy with a square setup. Be warned the handling will go towards oversteer. Personally I wouldn't do it.

Other then rotating tires what are you trying to accomplish by doing this?

Nov 14, 2019 | 03:14 PM

Ladyk

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More rubber on the pavement, the 258/30/20 seems like a better fit for traction in cornering etc. I thought you could do a front end alignment and correct for the under or over steer this might cause. What is your thought on this.

Nov 14, 2019 | 04:09 PM

JMII

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From: Margate, FL

I wouldn't do it.

If you need more cornering grip I'd would go wider on both sets and / or get gripper tires. And yes you'll likely have to mess with alignment to get wider tires up front.

Nov 15, 2019 | 10:39 AM

subieworx

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Quote:

Originally Posted by Ladyk

You would need to do a total car alignment.

Are you going to be doing track days?

You can run the same size front and rear tires and with HP tuners can adjust the tire size to keep the traction control system from freaking out.

Nov 15, 2019 | 10:50 AM

Bill Dearborn

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From: Charlotte, NC (formerly Endicott, NY)

Quote:

Originally Posted by subieworx

Does HPTuners have the ability to change the EBCM programming? The Traction Control function is controlled by the EBCM. The ECM just follows instructions from the EBCM. Even if you can get the ECM to not react to the command from the EBCM the EBCM can still apply the rear brakes to control what it sees as spinning tires.

Bill

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Nov 15, 2019 | 10:55 AM

LT1 Power

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From: Charlotte, NC

The wheels are in staggered size for a reason, I cant see any benefit to going the same size all 4 corners.

Nov 15, 2019 | 11:47 AM

#10

Bill Dearborn

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From: Charlotte, NC (formerly Endicott, NY)

Quote:

Originally Posted by LT1 Power

The wheels are in staggered size for a reason, I cant see any benefit to going the same size all 4 corners.

The smaller front tire is one way to build in some under steer for driving on the street. The OP's thoughts are by going larger diameter they can decrease under steer but that means they would also need to go with a wider tire which could get into some rubbing inside the wheel well. There isn't a lot of clearance around the lower control arms so going with a smaller diameter wheel can cause some rubbing on the front of the lower control arms. On my Z06 I run 18x11 front wheels on track and have issues with the inside of the rims rubbing against the air deflectors mounted to the front of the lcas. If I run a 315/30 Hoosier I start having issues with the outside edge of the tire rubbing against the spat. If I run a 305/660 Pirelli slick I don't have the spat issue. A 19 inch rim stops the problem with the inside of the rim rubbing against the lca but the Pirelli slicks come in 305/690 and 315/705 sizes which at 27 inches and 27.75 inches in diameter are too tall for the front wheel well and that leaves the Hoosier 295/30/19 which is about an inch narrower than the 315/30/18 and at 26.1 inches tall may be too large in diameter as well.

For track tires most people go with 18 inch wheel sizes since there are more choices.

Bill

Nov 15, 2019 | 02:07 PM

#11

subieworx

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Quote:

Originally Posted by Bill Dearborn

The tire size settings in the ECU though control the resultant speed output and should then help the traction control system. Haven't actually tested it yet, just a theory. I run staggered on my car, but I have heard of a few people doing this.

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