1LE Rear Tire Size

[1leNPP]

I think he talking about the Diff. it self it mite be a Torsen . I had one with a 4:1 TBR http://en.wikipedia.org/wiki/Torsen ratio it was good for road racing not so good for Drag racing .

[Firefighter]

I run one in my Dime,a Zexel (SLP pullout from an F body) it's a solid unit. I didn't know they put that in the 1LE. That's a good thing to me.

[1leNPP]

Sorry I should have said the Torsen mite be in the ZL1 I thing that what Pete mite have been talking about but I could be wrong. Now the Z/28 is going to have a Torsen in it . We got just a plane old clutch pack diff. with a 2:1 TBR ratio .

[Firefighter]

So disappointed... lol

That could be a future upgrade for me...

[Norm Peterson]

Originally Posted by gajagfan

. . . I would be concerned that the increased rear grip could bring back some understear, but assume the increased front grip would compensate for that

Close enough. More precisely, it's a matter of balancing the slip angles front vs rear, which generally follows what you do with tire sizes and wheel widths.

what is the difference in the two rear diffs (1LE vs ZL1)? I ask because I do not know and am curious.

The ZL1 has a 9.9" ring gear and an iron diff case. I think those are ZL1-specific pieces not available otherwise. "Heavy duty limited slip" was mentioned in the early reviews for the ZL1, whatever that means.


Norm

[Snidely Whiplash]

Originally Posted by racerx1214

There was an quote from one of the engineers that stated that was the reason.

I believe them.

They understand things better than a hillbilly with a mullet car thinking wider is always better.

Lou Gigliotti at LG Motorsports is a local guy that did quite a bit of racing Corvettes over the years. He put the FACTORY Corvette on the trailer more than once. If I have a suspension/wheel to tire size question, I'd ask him.

Local professional racers in DFW have more than a little knowledge of setting up cars to go fast. Lou is to vehicle handling on road courses as the late Lee Shepherd was to Chevy/Pontiac racing heads. Endless R&D is the reason. I've only spoken to Lou one time (while my exhaust was being installed) but spoke with Lee on numerous occasions. Lee gave us the "tulip" exhaust valve among many other cylinder head designs.

Remember - the FACTORY must produce within a budget. Racers must PRODUCE.

If I only still had those hand-ported Lee Shepherd big block heads, today.

[Norm Peterson]

Since this topic has floated another notice of reply to topic . . .

Originally Posted by Cody6.2

Yet the tire/wheel combo that does the most work aren't like this......

You don't suppose that the front wheels were intentionally kept down at 10" as a means of ensuring a little limit understeer for the average driver now, do you? Probably true for both the 1LE and the ZL1, except that the ZL1 also gets the wider rear tires as a crutch against the ease with which 550 ft-lbs will get them loose on even an easy corner exit on the street. Note that the Z/28 only runs 1/2" difference in wheel width . . . and consider that car's intent and intended buyer.

I can tell you that squaring the 11" wide wheels as well as a 285/35 tire size can and does work quite well, although breakaway can come a little easier under drop-throttle or with a little less warning otherwise.


Norm

[JusticePete]

Originally Posted by Norm Peterson

I can tell you that squaring the 11" wide wheels as well as a 285/35 tire size can and does work quite well, although breakaway can come a little easier under drop-throttle or with a little less warning otherwise.


Norm

[X25]

Originally Posted by Cody6.2

The same engineers also said the larger lower grille on the 2014 let more air in. Yet if you actually look at it the actual opening is the same if not smaller than the 2010-2013.

I guarantee if you put a ZL1 rear tire on a 1LE that handling would be better not worse.

The reason for more air is not the size of the opening, but rather the hood scoop that increases the flow by reducing the back pressure.

[Billy10mm]

Ah, my eyes. My eyes. The misinformation is strong in this thread:

1) The wider rear rim with the stretched tire makes the rear tire stiffer. This stiffness helps reduce grip in the rear and gets the car to rotate more. Not dissimilar to using a thicker sway bar in the rear.

2) To the guy who said that going to a wider rear would improve handling, you have no idea what you are talking about. The 1LEs best handling characteristic is its ability to both turn in quickly and rotate. The slim and stretched rear tire is a major reason for that and why many who track regularly and have driven both the 1LE and the ZL1 will tell you that the 1LE handles better.

For the people foaming at the mouth right now who can't wait to tell me how wrong I am because the ZL1 is faster around a road coarse ... calm down and let me explain. The ZL1 is indeed the faster car ... but an extra 150+ horsepower will do that. The ZL1 tire setup however, is a compromise, and is not set up ideally for road circuits. GM engineers put a larger rear tire on the ZL1 to help harness those 556 ft-lbs of torque on the street and on the drag strip. Having driven both cars quite aggressively, I can tell you that you drive both cars quite differently.

The 1LE turns in faster and is better balanced from a grip perspective. It is much easier to rotate the 1LE with minor throttle inputs - and minor throttle inputs are important, because if you need major throttle inputs or larger amounts of horsepower to rotate your vehicle, that rotation comes faster and is harder to manage. So you end up driving the 1LE differently from the ZL1. With the 1LE, you dive towards the Apex aggressively and quickly. You hold great mid-corner speed and you exit well. With the ZL1, you have to enter the corner with less speed, less slip angle, and you make that speed up on the exit, where that extra torque and the fatter rear tires help you to accelerate faster.

The end result is that the ZL1 is, and forever will be, the faster car on any regular road coarse (though I would bet a 1LE could do better in an Auto-Cross in the right conditions). But the 1LE actually handles better (for me, who enjoys a car that rotates easily and turns in quickly). The "for me" part in that last bit is important, as handling is a subjective trait. I would bet though, that most track junkies would prefer having a ZL1 power with 1LE handling.

[jcamo]

Originally Posted by white1LE

I don't road race so I installed the 305's for looks and grip in a straight line. Someone already said it, wider body needs a fatter tire as far as appearance goes.

......That does look good but it will have more push through the corners ...but since you don't track it roll on it looks nice.

[Spoolin]

Originally Posted by Billy10mm

Ah, my eyes. My eyes. The misinformation is strong in this thread:

1) The wider rear rim with the stretched tire makes the rear tire stiffer. This stiffness helps reduce grip in the rear and gets the car to rotate more. Not dissimilar to using a thicker sway bar in the rear.

2) To the guy who said that going to a wider rear would improve handling, you have no idea what you are talking about. The 1LEs best handling characteristic is its ability to both turn in quickly and rotate. The slim and stretched rear tire is a major reason for that and why many who track regularly and have driven both the 1LE and the ZL1 will tell you that the 1LE handles better.

For the people foaming at the mouth right now who can't wait to tell me how wrong I am because the ZL1 is faster around a road coarse ... calm down and let me explain. The ZL1 is indeed the faster car ... but an extra 150+ horsepower will do that. The ZL1 tire setup however, is a compromise, and is not set up ideally for road circuits. GM engineers put a larger rear tire on the ZL1 to help harness those 556 ft-lbs of torque on the street and on the drag strip. Having driven both cars quite aggressively, I can tell you that you drive both cars quite differently.

The 1LE turns in faster and is better balanced from a grip perspective. It is much easier to rotate the 1LE with minor throttle inputs - and minor throttle inputs are important, because if you need major throttle inputs or larger amounts of horsepower to rotate your vehicle, that rotation comes faster and is harder to manage. So you end up driving the 1LE differently from the ZL1. With the 1LE, you dive towards the Apex aggressively and quickly. You hold great mid-corner speed and you exit well. With the ZL1, you have to enter the corner with less speed, less slip angle, and you make that speed up on the exit, where that extra torque and the fatter rear tires help you to accelerate faster.

The end result is that the ZL1 is, and forever will be, the faster car on any regular road coarse (though I would bet a 1LE could do better in an Auto-Cross in the right conditions). But the 1LE actually handles better (for me, who enjoys a car that rotates easily and turns in quickly). The "for me" part in that last bit is important, as handling is a subjective trait. I would bet though, that most track junkies would prefer having a ZL1 power with 1LE handling.

Thanks for the in depth reply. I got what most of the guys in the beginning of the thread were saying but this was very clear and precise and helped clarify a bit more.
Made me wonder though, if they stuck that 305 rear on a wider rim on the ZL1, therefore stretching the tire and reducing some of the overall grip, would that help the ZL1 become more neutral and easier to rotate in the corners? Or would they also have to fatten up the fronts like they did on the Z/28 to get that effect?

I've been tracking my 1LE every other weekend for the past two months and have gotten really good at rotating the car in the corner with throttle and trail braking and it's been supremely predictable and fun. Reading things like you've written makes me wary of ever driving another car that isn't as balanced as the 1LE. I make alot of mistakes that would otherwise send me into a wall if it wasn't for the 1LE's neutrality in the corners.

[Norm Peterson]

Originally Posted by Spoolin

Thanks for the in depth reply. I got what most of the guys in the beginning of the thread were saying but this was very clear and precise and helped clarify a bit more.
Made me wonder though, if they stuck that 305 rear on a wider rim on the ZL1, therefore stretching the tire and reducing some of the overall grip, would that help the ZL1 become more neutral and easier to rotate in the corners? Or would they also have to fatten up the fronts like they did on the Z/28 to get that effect?

I don't think it's quite as simple as a wider wheel reducing grip. On one hand, the tire should gain a little vertical stiffness assuming you maintain the same inflation pressure. which will tend to reduce mechanical grip slightly. But on the other, there will be less tread distortion, which improves the situation . . . at least as long as you can still get (or keep) the tread similarly flat on the pavement. I'm quite sure you'd have to revisit the front wheel size, since reducing the rear slip angles without affecting the front slip angles is by definition additional understeer.


Norm

[JusticePete]

The push (understeer) is a product of weight, weight placement, speed and power. The OE fronts on the SS are too small. The 305s are the the best possible solution withing the sheet metal constrictions. 315s would be the perfect solution.