Thoughts on stagger

[Matt49]

I've been doing some thinking on this and I had some thoughts I wanted to run past my fellow 4Mers.
With as much rear steer as we are able to get with today's setups and the fact that there is almost always a certain amount of wheel spin, I'm beginning to think that tuning stagger to loose versus tight is a flawed thought process. I'm hypothesizing that the ideal stagger is the stagger that generates the rear wheel camber that creates the most consistent tire temps and wear across the surface of the rear tires.
I know, I know, everyone is going to say that increasing stagger always makes the car looser and I'm not necessarily disagreeing but I'm questioning the real reason WHY it makes the car looser. In my hypothesis that would be because as you increase stagger and hence increase positive camber of the LR and increase negative camber on the RR, you are decreasing the effectiveness of the contact patches thereby decreasing traction in the rear tires (which makes you looser).
My hypothesis could further then state that at some point decreasing stagger from the ideal stagger could also loosen the car but I'm not prepared to defend that statement just yet.
Just wondering what others' thoughts were on this and if anyone here has done any extensive testing in this area.

[MasterSbilt_Racer]

I've been doing some thinking on this and I had some thoughts I wanted to run past my fellow 4Mers.
With as much rear steer as we are able to get with today's setups and the fact that there is almost always a certain amount of wheel spin, I'm beginning to think that tuning stagger to loose versus tight is a flawed thought process. I'm hypothesizing that the ideal stagger is the stagger that generates the rear wheel camber that creates the most consistent tire temps and wear across the surface of the rear tires.
I know, I know, everyone is going to say that increasing stagger always makes the car looser and I'm not necessarily disagreeing but I'm questioning the real reason WHY it makes the car looser. In my hypothesis that would be because as you increase stagger and hence increase positive camber of the LR and increase negative camber on the RR, you are decreasing the effectiveness of the contact patches thereby decreasing traction in the rear tires (which makes you looser).
My hypothesis could further then state that at some point decreasing stagger from the ideal stagger could also loosen the car but I'm not prepared to defend that statement just yet.
Just wondering what others' thoughts were on this and if anyone here has done any extensive testing in this area.

My thoughts are that there is a stagger that is the proper compromise for your track when you look at runout, camber effects, etc. You put that on your car for all conditions.

[billetbirdcage]

A couple of these questions should answer your question, but first some info that will be needed

67.5" hub to hub rear end:

2" stagger = .84876 camber
4" stagger = 1.697 camber
6" stagger = 2.5448 camber

Just to see how much that is, here is the difference in height of the inside of the tire verses the outside of the tire (at 14" wide): Meaning - Tilting tire to said camber and measuring the difference in height off the inside of the tire verses the outside of tire

2" stagger = .20739"
4" stagger = .41463"
6" stagger = .62161"


That being said:

1: Would you only run .8 to 2.5 camber in your RF tire? If not why?
2. Do you think that no camber is ideal on a rear tire when cornering? I mean the tire is trying to roll under the car is it not?
3. Is rear steer the same as stagger? Does the 2 rear tires make the same radius of turn through the corner? is one not making a tighter radius then the other, therefore needs to spin faster to go around the corner (assuming no tire slip)? If the stagger is way less or more then the difference in radius each tires radius track's doesn't one tire have to slip?
4. Do you think the rear tires have better contact patch when corning at .8 verses the 2.5? So if you think the 2.5 is better, then it would have better traction contact patch wise.
5. Do other high level racing divisions (NASCAR - etc) use camber in the rear tires and do they have maximum camber rules? remember a lot of these also don't use a locked rear end

That should answer you question and let you figure it out yourself!

Later, Billet

Also remember you're dealing with a tire that is very compliant in general and in regards to side wall stiffness is very compliant as well unlike an asphalt tire.

[junebug]

this is just my opinion and may not make sense to anyone else, but i think that u run a certain amount of stagger to make the car rotate around the radius of the corner...."That corner doesnt change radiuses just because the racetrack gets dryer or takes rubber or has moisture in it" once i find a stagger that i like for a certain track i never change it ...i do things to make tires have more or less traction when track conditions change...i usually dont do things to change how much the car rotates.

[4bangerhotrod]

we did some testing a couple yrs ago to see what the best stagger on average was. we tested on 4 different tracks that were diff size shape and with alot diff turn radius's. we checked tire wear and temp's. we just wanted to find out what the best all around stagger was to use, so we wasnt changing stagger for every track. we came up with about 3 3/4"-4" to be the best all around stagger. so now we make every rear tire roll out 93" and 89" so now theres no having to find matching tires we can grab any tires we want and throw them on. the only time we change anything is on a tight 1/4mile track we will go to 4 1/2" just to help turn and on the real long sweeping 1/2mile tracks we will go 3 1/2" sometimes.

thanks,
4bangerhotrod

[profab00]

Do you suppose your test applies to all brands of chassis or just yours? I'm slightly past plain old hard headed when it comes to the amount of stagger to properly run on a good handling racecar

[4bangerhotrod]

well we tested this with a rocket but since then the driver has switched chassis 2 times and the tires were checked with each and the temp and wear was right so we've stuck with it

[billetbirdcage]

If your trying to figure out the true stagger needed only based on the 2 different radius' the tire follow then:

500ft corner (meaning the entry of the RR tire on turn 1 to the exit on turn 2 is 500ft across - entering at 3 O'clock and exiting at 9 O'clock, noon being 12 then measuring from the RR tire at 3 to 9 is 500ft. This is actually a 250ft radius turn!)

2" of stagger is the closest to being right
The RR tire travels 9424.7796"
The LR tire travels 9200.15406"

If the RR was 92" it would turn 102.442 times
If the LR was 90" it would turn 102.224 times

A 300ft corner (this is a 150ft radius turn)
4" of stagger is closest
The RR tire travels 5654.86"
The LR tire travels 5430.2"

If the RR was 92" it would turn 61.465 times
If the LR was 88" it would turn 61.70 times

[Graff Spee]

Heres what I do. I find out what the roll out is in the part of the track I assume I will be runnig . I then double that for qualifying stagger. I reduce the stagger as the nite goes on depending on the track condition etc. If the track is real dry for the feature then I am pretty close to my optimal stagger for roll out. Even with great amounts of roll steer you are still sideways a bit. You will need more stagger than your roll out suggests. You are just trying to optimize the use of each tire. In the feature you can use tire temps to see what is really going on.

[ALF401]

Adjusting Roll Out or stagger in the rear.

Do you adjust stagger with the left rear only???

[4bangerhotrod]

if we change stagger any we try to do it with the LR, that way we can keep the RR rollin out at 93" so we can keep the RR the biggest possible. theres a reason most series has a 93" max tire rule and no min tire size rule.

[ALF401]

Dumb Question time!

Why is there a max RR tire size rule???

Also we had biggest LR tire we had on the car and wanted to drop stagger, so we put on a 1" smaller RR, car was terrible, could not touch the throttle. Changing stagger messes with the bite in the car, is that the main reason most don't change stagger during the evening????

[junebug]

in the old days guys had only a few adjustments....like air pressures wheel offsets and stagger....problem with these adjustents is your not only changing stagger or air pressure or offset....you change a bunch more things all at once...like ride height wedge crossweight, bar angles wheel rates and a bunch more....i think its easier to change the things that have the least effects on other parts of the car....like changing one bar angle, assuming nidexing stays the same, or changing panhard height.....this is why i think most ppl are not changing stagger at the track anymore

[hall99]

I have to disagree I run mostly region type touring races and I very seldom change and bar or angle unless it is a extreme situation with the acception of bar length. Most of people I race with don't seem to either.

I still find pretty good success changing stagger, air pressure and the attitude of the car with minor coil over adjustments.

For me the best adjustment I can do my car is tires with stagger and making sure they are in good condition. Its seems to be the ultimate factor at the end of the race.

JMO - Good Luck to all.

[Ghopper]

Stagger is a passive method for torque vectoring that we are seeing on production vehicles. All performance cars are doing this with active differentials or brakes, but we only have stagger to legally change. Torque vectoring helps the car turn during cornering when the outside tires have more normal load (vertical force), and therefore a larger traction ellipse.

With respect to DLMs:
Because most of us are using a locked differential under throttle, and having different tire radius with equal angular velocities for our rear tires creates different longitudinal force at the contact patch (Larger radius has a larger force driving the car).

Production vehicles vary this effect with normal load. We cannot vary stagger depending on load, so we need to pick the best compromise for the whole track. Like 4bangerhotrod did, do a test that finds the best compromise for his type of tires (construction, compound).

4" is the long standard of compromise. But this should vary depending on compound and surface variation. These points will change the relationship of normal load to lateral and longitudinal force. At somepoint on these curves there is a drop in force and deminished return from excessive slipping of the tire. The only method you have for testing this is on the track (unless you have a lot of expendible income, and then I can point you to test facilities.)

I wish I had a better answer for you that could be applied today.


Ghopper