[JUST-TOM]

I'm new (obviously) to lightning sprints with a background in SCCA. In road-racing we don't run stagger of course. I've read a couple places that stagger can be adjusted with tire pressure.
But, dialing in stagger this way does it not throw off your tire presures in relationship to track conditions (i.e.- dry slick), forward bite, side bite, etc.
Or, is the answer just buying multiple tires and pairing them up properly?

Thanks for any help.
Tom G.

[TQ29m]

You can do it that way, and you will also find that tires of the same size will vary quite a bit in some cases, and, they do make tires in several "sizes" so you can at least get a pair for the rear that will give you as much stagger as you think you need. Tire pressures do make a difference, these are bias ply tires, so they respond to tire pressures pretty rapidly. I prefer to buy and mount tires, and measure them, then if they are close to what I want, with 8-10 psi, I can work with them to change the circumference as little as a quarter inch, or as much as a couple of inches, depending on how big the tire is to begin with, larger tires, more stretch, and you can stretch a tire by airing it up, and laying it out in the sun, just about anything you can think of, will make a difference. Good luck! Bob

[darnall]

The good thing is that as you start wanting to change stagger to adjust to track conditions the air pressure changes you would make also will compliment those track conditions....for example..

When a track is very heavy and fast, you want more stagger...you also want more air pressure in the RR and less in the LR, which will change the stagger the direction you want it to...

When a track starts to go dryslick, you want less stagger, and you also want less RR pressure and more LR tire pressure, both adjustments will take some stagger away.

For a beginner, don't get super worried about covering every combination in half inch or inch increments. You can get by with 2 right rears and 2 left rears as long as they are in the ballpark and measure an inch or 2 different than the other. I currently take 3 of each to the track, but one of each is old and worn out and strictly for using in hotlaps. I have a RR that rolls out to 104" and another that rolls out to 102"...I have a LR that rolls out at 95" and one that rolls out at 96" at standard pressures. That gives me 9", 8", 7" and 6" options at standard pressure, and I can gain another inch either direction or fine tune to the half inch with reasonable air pressure changes...all with only one spare for each side.

If you buy 2 brand new tires the same size there is a decent chance they will roll out as much as an inch different at the same pressure on the same size wheel. If they both end up being the same you can mount one on a one inch narrower or wider wheel and change the rollout. If you have 2 RR wheels with different offsets mount the bigger tire on the wheel with less offset and the smaller tire on the wheel with more offset...because when conditions call for less stagger they also call for moving the RR wheel in towards the chassis, so by mounting your tires like this you can accomplish 2 adjustments with a tire change.

Always remember when you mount a tire air it up to 25# or so and let it sit for awhile. Then bleed it down to race pressure and measure the rollout. A new tire will stretch during it's first time on the track due to heat and centrifugal force and will give you a much different rollout measurement than you thought it had. Airing it up to 25# takes care of that stretching for you and gives you a more accurate measurement.

And as mentioned above, you can grow a tire to an extent by airing it up pretty tight and setting it out in the sun. Just be very very careful not to over inflate it and explode it or the wheel. That can be a lethal mistake. 35 PSI translates to deadly force if a tire/wheel comes apart when somebody is standing over it.

The best way to stay on top of your stagger is to spend a night in the shop mounting all of your tires on different wheels and measuring them at constant air pressures. Use chalk to write the numbers on the tires on different wheels until you find the combinations that give you the most versatility. Once you decide which tires will be used on which wheels write the measurements on the wheel next to the valve stem with a sharpie. This will allow you to just grab one and put it on the car instead of having to measure, think about it and possibly make a mistake in the pits.

[JUST-TOM]

WOW! Great information, exactly what i needed. Thanks alot!

[darnall]

Originally Posted by JUST-TOM WOW! Great information, exactly what i needed. Thanks alot!

No problem man....welcome to the sport. There would be no open wheel racing if it weren't for new people getting involved. And I sure don't know much, but as you will soon learn everybody in this community is more than willing to share what they do know to help a newbie out.

[Steve in NOColorado]

When you adjust stagger for track conditions do you usually then also make an adjustment to the corner weight with the torsion bar also? I remember once making a stagger adjustment on a 270 micro that had the opposite of the desired effect. We added pressure to the right rear to increase the stagger to try to loosen the car up but when the driver came back in he said it was worse than before. Later after thinking about what we had done I concluded that we probably needed to take the weight that we added to the right rear out with an adjustment to the torsion bar. But I'm not sure if my assessment is correct or if something else caused the car to be tighter than it was before we added the air pressure.

[DAD]

Just

Welcome to Mini Sprints. What part of the country are you from?

Years ago we ran across a father son Mini Sprint team just transitioning over from SCCA class racing to Mini Sprints. They were having a bit of a problem also adjusting to left turn only racing. Their names were Larry and Scott Fasse. I turned Larry the dad on to a book written by Steve Smith Titled "Mini Sprint racing and set up". Well I guess Larry and Scott read the book. They went on to open up a store for Mini Sprint racing parts called "Speed Partz". Scott the son went on to write and publish his own book on Mini Sprint racing titled "Mini Sprint Racing 101". They even went on to sell their own brand of race car that they named the "Foz".

I understand Larry is retiring from "Speed Partz" this year. What he doesn't mention is that he was retired from working when he started "Speed Partz". Give them a call or Google search them. Buy both books from them, read them a couple of times and come on out to the race track. Talk to your fellow racers and ask questions, the books will help you frame your questions.

We depend on a half dozen tires and wheels to set our stagger>> several right rears and 4 or 5 left rears. We adjust air pressure only to help adjust the car to track conditions heavy or dry, never more than 2 or 3 PSI. Race tires are like children you can buy half a dozen of them all the same size and when you air them up each one will be a different size, to add insult to injury you can go out and race them and they might "Grow" or "Shrink" in circumference. Then when you dismount them and mount them up again they will measure out different again. Check your tire circumference and tire pressure immediately after the race and take notes, you will soon see a pattern.

Good luck>>>have fun>>> and if you are ever in the pits with us look us up.

Honest Dad himself

[TQ29m]

DAD, you been in the history records of this forum, this post is over a year old, and not a reply from the original poster, probably trapping in Alaska now!? Bob

[DAD]

His second and last post was on 4-26-2013 Like an old test I used to give>>>> "Read everything Before doing anything">>>>boy did we ever mess up a lot of memo graph paper on that one.

Thanks Bob I needed that!!!

Honest Dad himself

[DAD]

Originally Posted by Steve in NOColorado When you adjust stagger for track conditions do you usually then also make an adjustment to the corner weight with the torsion bar also? I remember once making a stagger adjustment on a 270 micro that had the opposite of the desired effect. We added pressure to the right rear to increase the stagger to try to loosen the car up but when the driver came back in he said it was worse than before. Later after thinking about what we had done I concluded that we probably needed to take the weight that we added to the right rear out with an adjustment to the torsion bar. But I'm not sure if my assessment is correct or if something else caused the car to be tighter than it was before we added the air pressure.

Steve

Looks like you have been researching this problem a little bit. With the 13 inch wheels we don't usually worry about bar adjustments to compensate for difference in diameter of the tire, usually a fraction of an inch or so. If you want it tight you add weight to the left rear not the right. What probably happened to you is the track changed on you.

The same thing holds true for Steve Smith and his book, the best thing since buttered bread for somebody just starting out racing. And the neat things this info even holds true for bigger cars.

Honest Dad himself