I've followed NASCAR all my life. One question I 've always had was what type of differential do they run? Lots of times I've seen just ONE tire track when leaving the pits (sometimes right, sometimes left). It seems to me that a locking-type would constantly be "working" especially on the short tracks where the outside wheel is always traveling further than the inside. But when doing victory burnouts they're definately BOTH spinning. I guess it could be controlled by stagger to some extent (right side tires different circumference than left side). Anybody know?

I think at the super speedways, they use open gears, on short tracks they use Detroit Lockers.

I would imagine the different between pit road and burnouts is they are probably feathering the gas and slipping the clutch on pit road to stay under the speed limit versus the burnout where they just mat it and snap the clutch.

There is no way they use Detroit lockers in any track, perticularly short tracks. The tight radius corners need a LSD to get around the corners. Personally I've never seen a one tire frier out of the pits, always been both wheels. Can never see them using open diffs because of the massive lack of traction. Limited slips all around at every track is what i'd say.

actually, i think they do run lockers. at least on the big tracks.
if only NASCAR had a good technical section on their website...

I've heard,or read(?),open diff.s at super speedways before as well.

edit:I found this on Eatons' website:
Detroit Locker
The Detroit Locker maximizes traction by delivering 100 percent of the torque to both drive wheels. It is engineered to keep both wheels in a constant drive mode, and has the ability to automatically allow wheel speed differentiation when required. Enthusiasts and professionals use the Detroit Locker in many off-road applications. It is the only differential used in NASCAR.

here's the link:http://www.eatonperformance.com/press_releases/brands_012306.html

There is no way they use Detroit lockers in any track, perticularly short tracks. The tight radius corners need a LSD to get around the corners. Personally I've never seen a one tire frier out of the pits, always been both wheels. Can never see them using open diffs because of the massive lack of traction. Limited slips all around at every track is what i'd say.

Start watching a little more closely then. When I worked on a local guys car, we ran a mini spool on 1/3 mile tracks and an open rear on 5/8 mile tracks.

they run a open on big tracks and a posi on shorter tracks......the stagger in the rear tires helps the cars turn....at least thats what we did when I had my arca car.....but it may have changed in the past few years

Yep, gotta have a locker for the stagger to have an effect. Stagger is like taking a paper drink cup, laying it on it's side, and rolling it. It turns, because the mouth is bigger than the bottom. This is the principle behind stagger. The right rear is bigger than the left rear, and influences the way the rear of the car turns.

Stagger is like taking a paper drink cup, laying it on it's side, and rolling it. It turns, because the mouth is bigger than the bottom. This is the principle behind stagger. The right rear is bigger than the left rear, and influences the way the rear of the car turns.

And exactly the reason it's important to have the same size circumference tires on a drag car. :yes:

Nascar tires dont have much stagger, if any on them. Even Indy cars have just 1/2" stagger. Its not like sprint cars or modifieds.

I would never run a spool on a short track, and if I were to run one, itd be on a superspeedway where the corners are very long, and you gotta do clutch dumps out of the pits.

We used to run up to around 3/4 of an inch, less on the "big" 5/8 mile track. And you need a locker on the short tracks for a couple reasons, one, to kick the back end around in the corner, the cars just don't turn well enough to do it all on their own. And two, if you ran an open rear end on something as tight as Martinsville, you just blow the inside tire off when you mashed on 850HP coming out of the corner.

I never suggested running an open diff at Martinsville, personally I wouldnt anywhere. I fully agree it'd be very traction limited. If your kickin the back end around a corner, then the setup and driving style isnt correct. The fastest way around a track is not sideways. A spool would understeer into the corner, and out of the corner, and just not rotate through the middle. Like you said, you have to kick out the backend just to get it to turn. A good LSD will allow the one tire to travel at the different rate, while still putting power to the ground via both wheels.

3/4 of an inch is quite a stagger though. :)

They all run one form or another of a locker, everywhere, in a ford style 9" pig. Stagger is pretty much gone now due to the radials, you must run the air pressures dictated by goodyear. The changes in the way they set those things up now would shock anyone with old time experiance! Ralph

Ralph67

You are right with old school experience meaning nothing. In the old days of bias ply tires - stagger was HUGE in making a difference. Remember the days of team running rights on the left side and vice versa.

All rearends are Ford 9 inch deals with truck trailing arms. Very similiar to chevelles, but the trailing arms are alot longer.

Sideways is the fastest way around on dirt!

I'm not sure if todays setups are even similiar to ones of two years ago. Back in 2005 I know for a fact that alot of cars where running around on the right rear. Very similiar to a dirt track setup.

Remember there are very little wedge changes now. Most adjustments are with a half pound here and there. Very little track bar anymore.

And exactly the reason it's important to have the same size circumference tires on a drag car. :yes:

& air pressure!

:confused: I always thought (not that I think alot) NASCAR used quick change rear ends as well as open wheel Sprint and Indy cars.

I'm pretty sure NASCAR Super Trucks have the same Champ or Halibrand quickchange rearends that Outlaw dirt track cars use

all the top NSACAR series share a lot of common suspension and drivetrain parts. they all use a 9" rear axle and truckarms in the back, and the same front suspension parts that are readily available from a number of aftermarket suppliers.
yes, you can order the very same suspension parts used by your favorite NASCAR teams brand new from any number of places. just flip thru a circle track magazine sometime and see what's out there.

No quick changes in cup, busch or trucks Cardiac. They have been referedto as that sometime because you can change a 9" pig in about 10 minutes, or less! with the right guys. Ralph

I run from 1/4 mile to 3/8 mile asphalts in modifieds and we use Diamond track diff. I also know several late model and Grand Nationals that use this one or a similiar one. It basically has 16 little springs (or you can use less for less preload) and that locks up the rear. It is not a ratchet like a Detriot CTRR which is a locker style. On mine I have about 250lbs breaking load. We do run a spool every now and again and they suck compared to one of these. Would also have a Blackgold by DPI which uses the same principals. For our 1/4 track we use upto 3" of stagger and the 3/8 mile it shrinks down to under 2". We run a treaded Goodyear Eagle and slick Goodyear Eagle for Short tracks, I doubt they are the same ones used in the big leagues. They are like a bias ply but also like a radial. We are having to increase the air pressure so high to get the sidewalls to stop pulling the contact patch off the ground. We actually run air pressures in between the bias and radial.

http://www.quickchangeexchange.com/diam.traks,9.html

Why sometimes you see only one tire spinning on leaving the pit box. This was started years ago by Ray Evernham while with Jeff Gordon. Ray would have one person and yes this was thier job. When Jeff would come in, A guy behind the wall would throw OIL DRY under the left rear tire, So upon the hard clutch dump on the exit ONE tire would bite and one would spin putting less load on the Complet drive line. Everything brakes under a load. If you are spinning and not hooking up, NO-clutch,tranny,D-shaft-ring and pinion, axel problems. GEE I would have never thought of that, But Ray Evernham did.

Bob ACES--AACA
And yes I work for the networks and do NASCAR races.

Bob
Now that you mention it, I remember when they started tossing speedy dry under the wheel :clonk:

Why sometimes you see only one tire spinning on leaving the pit box. This was started years ago by Ray Evernham while with Jeff Gordon. Ray would have one person and yes this was thier job. When Jeff would come in, A guy behind the wall would throw OIL DRY under the left rear tire, So upon the hard clutch dump on the exit ONE tire would bite and one would spin putting less load on the Complet drive line. Everything brakes under a load. If you are spinning and not hooking up, NO-clutch,tranny,D-shaft-ring and pinion, axel problems. GEE I would have never thought of that, But Ray Evernham did.

Bob ACES--AACA
And yes I work for the networks and do NASCAR races.

Funny you mention this, as the only one I ever seen do this was Dale Earnhardt Sr at Talladega. It was necessary because of the high gear in the rear to run 190+ they had a problem with shearing the yoke right off the pinion.
A few years ago, the summer race at Michigan was a much better race, as the teams complained at the June race that they couldn't get the cars to turn. They pushed too much. So Goodyear made a new right side tire for the August race that was a bit bigger to give the cars MORE STAGGER.

So they are still staggering tires in Nascar?

So I wasn't dreaming when I've occasionally seen a "one-legger" out of the pit box??

Some time they help the left to spin, sometime the lockers unlock and that happens. They have some "stagger" built in but they are using other means to get the cars to turn now. You would not believe what rate springs i have seen going in the cars and what they can do with the shock packages now. They actually have cars "bottom" on bump stops rather than use the full suspension. This is why the COT is giving some fits they have to go back to a more traditional style of setting up the cars. You may see an occasional "one legger" coming out its not that un-usual. Ralph

Thank you everyone for answering my question in such detail. I am satisfied and feel good about a question that has troubled me over the years.