1969 Torino

[FETorino]

Originally Posted by Flash68

That wheel is sick.... would make even a Torino look pretty good.

If you did something similar on BMF it wouldn't be a bad thing.

[intocarss]

Originally Posted by FETorino

If you did something similar on BMF it wouldn't be a bad thing.

[Flash68]

Originally Posted by FETorino

If you did something similar on BMF it wouldn't be a bad thing.

Similar... but different.

Originally Posted by intocarss

Now there's the Jer we all know and love.

[Ron Sutton]

Hi Guys,

I'm back. I'll try to catch up.

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Hi Todd, I love racing in Vegas.

Do you AutoX your car on a regular basis in Vegas? If so ... where?

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[Track Junky]

Originally Posted by Ron Sutton

Hi Guys,

I'm back. I'll try to catch up.

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Hi Todd, I love racing in Vegas.

Do you AutoX your car on a regular basis in Vegas? If so ... where?

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Glad to hear your back Ron.

[Ron Sutton]

Hey Ron, another question for you...

You mentioned that in Gaetano's case he might as well have just thrown 275 tires on the back of the car instead of the 315s because he would need to remove the 15.x percent more grip that the 315s added in order to get the car balanced again.

My question is, if you're working with more tire in the back versus the front, can you tune the rear to have more grip in the straights and less under steady state cornering?

Good question. Tough answer.

First, What is this steady state cornering you speak of? I'm kidding, but only a little. The car is almost always in transition. Even in the "roll through zone" ... after the driver is off the brakes & has not picked up the throttle yet ... the car is decelerating (coast down) so the speed is changing ... "settling" in pitch (nose wanting to come up & rear down) ... and increasing in roll angle a small amount more. On long sweeping corners the car might be in the "same state" for a second. But on most road courses, short to medium ovals & AutoX, the car is constantly "transitioning."

When I'm working with a race driver, we break each corner down to three sections ... and if that is not enough detail, we'll break it down to all 5 or 6 driving actions. The three sections are Entry (braking & turn-in), Middle (roll through zone, coasting, no brake or throttle) & Exit (throttle roll on & steering unwind).

If the car is doing something difficult to sort out, the driver & I will break it down to what happens at each step: Brake application, steering input into the corner, steering set, brake release, roll/coast, a sharp steering "cut down" if there is one, steering unwind & throttle roll on.

You can make the larger rear tired car turn great on entry & have awesome grip on exit. The middle is always the challenge. The bigger rear tires make it hard to roll the center at optimum speed without pushing. And the ironic part is, the mid corner push caused by the larger rear tires ... CAUSES the car to "snap loose" on corner exit ... and be loose on exit.

If you can get a handling car to turn well in the middle, without pushing, it won't "snap loose" on exit ... and if tuned right ... will have more grip on exit, than if we were fighting a tight or push condition in the middle from larger rear tires.

Just so everyone is clear:
A. There are lots of suspension tuning methods to improve rear tire grip on corner exit. Having bigger rear tires is just one.

B. I'm not saying you can't run bigger rear tires and have a good handling car, but when they difference gets significant, you designed in handling problems for yourself.

C. There are situations where we want bigger tires in the rear, than the front, but it is when the car's weight balance is rear heavy.

D. Otherwise, having the same size tires front & rear, makes it easiest to create a well balanced handling car, that will be fastest on track.



Matt

[Ron Sutton]

Originally Posted by Matt.A

Hey Ron, another question for you...

When you discussed the pros and cons of high roll/low pitch versus high roll/low pitch, I was curious if you could run one setup on the front and the other on the rear. I feel like there is a reason you haven't mentioned doing this, but if you have the time, it would be cool if you could explain what would happen from running low roll/high pitch in the front and high roll/low pitch in the back.

Thanks for all the time you've spent sharing knowledge with us amateur hour club guys

Matt

Hey Matt,

It works .... but not the best. But not for a lack of trying, as I have seen literally hundreds of racers "in transition" from old school set-ups to the new high travel set-ups try to keep their setups in the rear.

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Conventional:
• Stiff front springs
• Small, soft sway bars
• More Roll
• Less Pitch

Sample Set-up for a 3000# car:
Front Springs: 550-700#
Front ARB: 100-200#
Rear Springs: 150-200#
Rear ARB: 50-100# or … No ARB & 50-100# stiffer rear springs … or higher rear Roll Center

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High Travel:
• Soft front springs
• Big, stiff sway bar in front
• Known as SS/BB … soft spring/big bar … if no bump stop or coil bind is utilized.
• Same concept used in conjunction with travel stops: Bump Stops or Coil Bind
• Less Roll
• More Pitch

Sample Set-up for a 3000# car:
Front Springs: 300-400# (200-350# with bump rubbers or coil bind)
Front ARB: 600-1500+# (from short tracks to big tracks)
Rear Springs: 300-500#
Rear ARB: 100-200# … or No ARB & 100-200# stiffer rear springs … or higher rear Roll Center

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The problem if you allow the rear to roll too much is ... the car rolls over unevenly .... onto the outside rear tire ... and off the inside front tire ... reducing the tire contact patch on the ground in the front by half ... causing the car to push.

One key to the "less roll" set-up ... is less roll ... running flatter ... in the rear helps keeps the inside front tire planted.

Make sense?

[Ron Sutton]

Originally Posted by FETorino

Ron flew the coop for a week so until he gets back I'm taking a break from the tire/handling discussion. I have some more info on track width and such to throw out there for discussion.

I did take track width into consideration when choosing the tire wheel package. My front comes in at 55.25" and the rear at 58" Ron was surprised by this since it is intuitive to think tubbing in the rear would push the track width in significantly. I had to remind him what you all know. My car has a big butt. So more tire to the inside of the fender would have widened the gap in front to rear track. Currently I have 1.75" more TW in the rear which should help free the back end up some even with the 345s.

Rob,

I did incorrectly assume your wider tires in the rear would have narrowed the rear TW. Thanks for clarifying your car is different. You're on the right track that the wider rear TW will free/loosen up the car..

If your measurements are right ... front TW 55.25" & rear at 58" ... the math ... 1.75" more TW in the rear ... doesn't jive. That would be 2.75" more TW in the rear.

Would you please confirm the numbers, so we're talking on the same page ?

Thanks !

[Ron Sutton]

Originally Posted by 67goatman455

Whew! i never thought i would see so many informative posts in a row in this thread!

I have so many noob questions, that i'm pretty lost but ill sit back and keep reading. Hopefully ill catch on. looks like i need to change my mind set, I too planned on throwing the biggest freaking tire on the back i could, and make do with what i could up front. I will be quite disappointed on the track if i do that, i see!

Yes, Scott, you would be constantly fighting a push condition. And that's no fun.

[Ron Sutton]

OMG Rob,

Those wheels are really nice looking. Light too.