cbernhardt

I have read several articles indicating that the best acceleration is obtained with some degree of rear tire slippage. Does anyone have an opinion as to how much slippage relative to the front tires would produce the best acceleration? Assuming, of course, a rear wheel drive car and that the front tires stay on the ground

Charles

4DRUSH

I would say less than 1 revolution of the back tire would be good

Dave-T

QUOTE=4DRUSH;1587552183]I would say less than 1 revolution of the back tire would be good[/QUOTE]

cbernhardt

4DRUSH and Dave-T – thanks for the replies. Are you saying that maximum acceleration down the track would be achieved with just one turn of the rear tires and then no slippage?

I am not an experienced drag racer, but here are a few quotes I found on line. I realize that these articles are more for ultra high power dragsters, but I would think the same principles would apply for any car.

http://dragracingonline.com/technica...nfc3000-3.html
“In order to get maximum traction between the rear tire and the racetrack surface the tires must also slip just a bit going down the track. Clear evidence of this tire slippage are the black streaks that run down the track following a run, and the resultant rubber that builds up on the track. “.

http://www.turnfast.com/tech_handling/handling_tractn
“a tire's maximum traction potential is actually reached when there is a small amount of slippage….. In acceleration, the tire should travel slightly more distance than the distance of the acceleration (spin just a bit faster than normal). The tires will actual slip; not a lot all at once to result in free wheelspin, but ever so slightly during the whole acceleration phase. When you can sense this slip, and control it, this is when you're getting maximum acceleration from the vehicle. “

My reason for asking this question is related to a project I am working on. My car is a ’59 with C4 suspension and it has a 572/620 GM crate engine, 4L80E transmission, and weighs about 3000# with me in it. Wheelspin off the line with street tires is easily obtainable. As an inexperienced drag racer it is difficult for me to tell when the rear wheels start to lose traction, so I have programmed a microcontroller to read the front and rear ABS sensors and I can compare the front and rear wheel speeds to compute the amount of rear wheel slippage compared to the front wheel. The car does not have fuel injection so there is no way (that I know of) to electronically control engine speed so I built a small box with four lights that show the amount of wheel slippage. The first light comes on with no slippage, the second light comes on with 5% slippage, the third light with 10%, etc. I can program the lights to correspond to any percentage I want, but I was hoping to get some idea as to what the optimum slippage percentage should be. It may be that I just have to take it to the strip and try it out.

Charles

Paul_Z06

I'm not an experienced drag racer but I did stay at a Holiday Inn Express once.....or twice..I'd suggest you watch some Pro Stock races.

mackeyred96

Are you using a C4 IRS?

cbernhardt

And what should I learn by watching?

Yes. If I break it I will be putting in a solid axle.

Charles

4DRUSH

If.......

mackeyred96

Put the solid axel in now! That IRS Dana 44 if you put a slick on the car won't last at all.

tektrans

Cant sell it if you break it...

Joe_G

You're going to learn what wheel spin feels like pretty quickly, in my humble opinion you won't need a device to tell you it's happening...though it's neat that you were able to build such a device.

A good video man at the starting line is very helpful, along with a go pro or even your phone with a mount in the car to watch you and the gauges. These items will help you improve a lot.

If you drag race very much at all you wouldn't want an electronic device to cut power with wheel spin either - c5, c6's and c7's all have traction control and we always turn it off because the computer isn't as good as a good driver in controlling spin yet maintaining forward momentum.

Your build sounds really cool...can you post up some pictures?

cbernhardt

Pictures here: www.carols62.com/59

Dave-T

Beautiful build.

Joe_G

Wow that is amazing...you did some great work.

Have you taken it to the track yet?

Paul_Z06

That these cars don't dead hook and wheel spin is induced intentionally. I think there's a wide misconception that it's best to dead hook on the launch. That's best for breaking parts.

Joe_G

Holy smokes I spent some more time on your webpage....

You did some tremendous work - making your own hubcaps, making your own headers (that look terrific BTW), creating a channel in the door hinges for the wiring...doing your own body work and paint....very impressive indeed. I'm glad I spent some time on your page and glad you put up all the pics.

May I ask, what is your day job such that you have such skills in your repertoire?

And I don't recall seeing what converter you have but if you have a stock converter it will be holding you back from good ET's...though it's soft launch may be easier on the parts. A good converter will give you quite a bit of ET.

cbernhardt

Thanks for the compliments. As you may have noticed by the dates on the pictures, I have been working on this project for a long time. Almost everything worked as planned except the hubcaps, they just did not look right on the 17” and 18” wheels. Since then I have modified a set of 16” x 7” Camaro wheels to take a set of original ’59 hubcaps. They look like original ’59 wheels, but unfortunately I put C5 calipers and rotors on the front end so now those wheels will not fit.

I am a retired civil engineer and got into computer programming later in my career. Lived on a farm most of my life so I learned how to weld and fabricate in order to repair farm equipment.

All I know about the converter in my ’59 is that it is a 2500 rpm stall speed. Originally I built the car to run in the Maxton Mile, so I was not really too concerned about performance off the line. Just about the time I finished the car the sanctioning body (ECTA) moved the event from Maxton, NC, which is about a two hour drive from my house, to Wilmington, Ohio, which is a little too far for me.

Charles

Joe_G

Very nice. My hat is off to you for such a great build. It deserves to be in a magazine.

Regarding drag racing, my advice would be to just go do it. You'll know when the car is spinning and let off. When I used to run a series, my advice in every drivers meeting was if you get sideways, let off - its much easier to control the car without the throttle floored, most of the time when guys go into a wall it's trying to drive out of a slide at WOT. Not easy to do. Let off and the car usually comes around.

One thing I like about drag racing is it's something you can measure, and therefore, track improvement. I like to monitor my driving, launch RPM, shift points, speed, etc. That's much less important in an automatic. You'll experiment with different launch techniques, (flash from idle vs. holding at different RPM), burnout length (I like 8 seconds), tire pressure (I like 17 psi). After you get your car consistent and the improvements are at much smaller increments, you'll want to go quicker. When that happens I advise looking for a looser converter. Modern converters are the magic bullet as they are loose when it matters but not bad around town like the old ones were. If you post up a dyno sheet you'll get advice on what converter to use, including stall speed and shift extension. It's a science that has come a long way I'd say in 10 years....the converters of today can be expected to knock a half second to a full second off a ¼ run.

Though geared toward a manual car, this website is a resource used very successfully by many...and the videos are great.

www.rangeracceleration.com

If you hit the strip let us know the results!

subfloor@centurytrans

I'm of the opinion that in order to be as consistent as possible, dead hooking is the better way to go. The problem with having some slippage is that unless you have the exact same amount every single time you won't be able to dial in the car properly.

Joe_G

Listen here you slush box guy...easy for you to say...your car comes with an automatic slipper!

Us clutch guys have to slip something, either the clutch or the tires.

That said, I agree with you, I've personally always slipped the clutch, not the tires. But even with that, trying to be competitive in a money drag race with a manual is like showing up to a gun fight with a knife. You can get lucky once in a while and the guy will miss but you're at a significant disadvantage.

Some clutches won't allow this, and in those cases, I typically recommend a bias ply tire as they are easier on the rear and can slip then grab a lot more than a drag radial.

In the OP's case I don't think he plans to get that into drag racing, and as we know, bias rear needs bias front or at least skinnies to avoid the dreaded "butt waggling" doing down the track. And of course, you can't really drive on the street on the bias ply...a puddle can loop the car around.