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TECH CORNER
The largest Legends Tech resource on the internet:
RPM/MPH/Gear Chart
(click for printable copy)
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This page will be created and expanded as new information and test results are
acquired. We started racing late in 2000. Started late again in 2001. We learned
a lot of what not to do. We are now learning what and why. We have found a lot of
misinformation and what works for one doesn't work for another. For as many cars
and drivers there are out there, there are that many different setups. There are
some smooth and patient drivers and some ram bang impatient ones. Either way when
the car matches the driver, then a winning combination exists
The following are links to Legends Series web sites that already have tech information.
Bob Graham III, Alpine California "LEGENDS FORCE" a great name for a Legends web site.
Lots of useful educational tech information plus some rule tips. Bob also takes care of team LCOC
and the Barona Speedway. Cal. dirt track web sites.... A GREAT LEGENDS SITE TO VISIT
www.legendsforce.com
Kevin Yeatts from Powhatan, Va. has a quick fix chart and a tech tips page worth checking.
Kevin also sells setup information.
www.kevscorner.com
International Legends Cars...Utah Dealer Brandon Burton has put together an informative Legends web site.
Tech tips, cars/parts for sale message board, etc.
www.legendcars.com
Legends Auto Racing "Design and Theory:" TX OUTLAW An informative Legends web site.
Tech tips, cars/parts for sale, tips for sponsorship and more.
www.legendsautoracing.com
Nevada Racing An informative Legends web site.
Tech tips, cars/parts for sale. The largest used car list on the internet. Great Job
www.nevadaracing.com
North Dakota Legends ND Legends has a
tech board in thier Discussion board. Well worth the visit.
www.ndlegendsracing.com
Throttle stuck open?
DO NOT try to slow down and stop the car by using the brakes with the car in gear and the engine racing.
This never works. You will just burn off your back brakes and lock up the front and loose your steering.
You have two options. 1. Push in the clutch to release the drive train. 2. Reach over and shut off the
ignition switch. I practice full throttle recovery. I sit in the seat, imagine certain situations and
physically push the clutch in and shut off the switch. You may think this is stupid and I am daffy in the head
but it is called training. When I climb into a race car I want to know two things, where is the throttle
to make it go fast and where is the shut off switch to kill it.
Full throttle problems. This is a highly unlikely problem in a Legends car but I have seen it happen.
A bad cable is most often the problem. We have had this problem. Check the cockpit side and the carb side for broken cable
strands. Check the outer cable for kinks and sharp bends. These cables are cheap and easy to replace.
Special note:
Set your throttle cable so you have full throttle when the foot pedal bottoms out. If you don't get it quite right
with the cable locking bolt, you can tweak it in by adjusting the cable ends.
The carb mounting band clamps. These can be a problem if they are not positioned correctly. I have
not seen the throttle stick wide open because of these but I have seen them stop the throttle from
opening causing the engine to run poorly.
Special note: These clamps have a special alignment dimple. Align it with the bump on the intake rubber
and you won't have any problem. We haven't done this one but we helped someone fix the problem who did.
Another special note: Do not over tighten these band clamps like I did. It will cut the intake rubbers
and you will be sucking air.
The throttle body rack. This is a simple design. I have never seen any of the return springs break nor
have I ever seen a shaft bend. This could happen. Just inspect it from time to time. We do.
The only time I saw a rack stick was when a small stone jammed between the throttle cam and the aluminum
heat shield on Scott Below's #51 car. He had enough present of mind to push in the clutch and shut off
the engine.
Special note: Lamar Shaffer (LHS ENGINES) tells me if the cable is not adjusted as stated above
you can stress and damage the throttle body rack.
ODD BALL PROBLEM Nut that holds the throttle pedal on. Use a lock nut. If you use a nylon lock nut
the nylon can wear out. Vibration can tighten and loosen any nuts. Check this nut
to see if it is tight on the stud but not tight against the pedal allowing free movement.
If it is to close to the pedal, pushing down on the pedal may tighten the nut causing the pedal to stick.
I have experienced this with similar lever operating systems so it could very easily happen here.
While we are on the engine, DO NOT over torque these bolts and screws. Head bolts 25lbs. check them
often and retorque when cold. Pick up a Yamaha repair manual and follow the spec's.
Since I am on a roll of admitting things, I am going to quietly state; if it is on a Legends car
and can be broken or screwed up; my list of "done that" is longer then my list of "didn't do that"
............yet.
TIRES: Legends cars race on a spec. tire. We are only allowed to use the "Legends Edition" BFGoodrich
205/60R13 T/A Comp HR4 tire. You can not soak, soften, razor cut, regroove or recap these tires.
As of 2002 we are allowed to camber and/or flat cut the tires. The tire rule is a blessing as you do
not need different size and/or different compounds for each corner of the car. The tires are responsible
for the traction limit of the car so your job is to figure out how to get the maximum contact patch on
the ground when it is needed. If you race both asphalt and dirt buy two sets of tires, always use the
fresh ones on the dirt. Tires get hotter on the asphalt and get harder with time. They also wear
different and faster.
Camber and flat cutting the tires: This rule change came about because almost everyone was doing
it and it was impossible to detect or prove because tires will get a camber wear to them anyway.
Unfortunately this adds to the cost of racing. You now need more tires plus the cost of cutting. We
camber cut the front tires only because the guy who owns the tire cutting machine said it was a good
idea. The Legends Edition tires are radial tires. Radial tires flex and roll. We record tire temps and
don't see any difference in a camber cut or non camber cut tire. We do not race on the asphalt very often
and we don't have any tire temp comparisons so we can't say if it helps or not. Remember, he who sells
snake oil stands to profit the most. We do not flat cut the rear ones for the dirt. However
for the asphalt we suggest cutting all new tires to prevent the tire from tearing chunks out
of the tread. We have experienced this on asphalt but never on dirt.
NOTE: We are going to be talking about the left and right sides of the car. To avoid any
confusion we are going to use the US standard, the drivers side is the left side and the passenger
side is the right side. End of confusion. I forgot about England and the right hand driver cars.
Well here goes, it is while sitting in the drivers seat, left is left and right is right. Got it? OK
spot on.
Stagger: Stagger is the difference in circumference of the left side and the right side tires.
Legends Edition tires are about 70.5 inches around. We only pay attention to rear stagger as the rear
is locked and both axles turn the same. When you go around the corner the outside tire (right side)
needs to travel more distance causing drag on the outside tire and/or slippage on the inside tire
(left side). The tire rule limits your choice so measure and mark your rear tires. Put the largest
one on the right rear and the smallest one on left rear. We have only
found a 3/4 inch difference and most often we don't even have that. Get as much as you can.
Front stagger: Some people claim front stagger helps. I think they are blowing smoke but if
you think it will help do it. The front wheels are independent of each other. There is no drag or
slippage problem. You are looking at contact patch and traction limits here. We do not pay any
attention to front stagger.
Tire air pressure: For the dirt. Many people are running 5-8 lbs. on the left side and
8-12 lbs. on the right side. Take tire temp readings. Take them as soon as you get the car back to
your pit area. Use a probe type reader that sticks into the rubber. A spot reader only reads the surface.
This may give a false reading as the rubber under the surface may be warmer. We are running 9 lbs. on the
left and 13-14 lbs. on the right. Our car is a little heavy and the driver weighs 200 lbs. Our car with
the driver scales out at 1,375 lbs. With the lighter air pressure the center of the tire starts to fold
in and is not contacting the track. Remember, your job is to get max. tire contact with the track when
you need it. On the asphalt we double our tire pressures. The tire temps are much hotter on the asphalt
but they are still fairly even.
Tire air: A short word about tire air. As the tire heats up the pressure will also increase.
Some times by several lbs. The drier the air you put in the less the effect. It is the moisture in the
air in the tire that causes this. Some people are using nitrogen to fill their tires to help keep their
tire pressures even. If you don't get the moisture out nitrogen doesn't work much better than air.
(Want a little laugh -- Nitrogen makes up 78% of the air, by volume on earth)
We do not use or buy into the nitrogen trick. It cost money and the results are not worth it simply
because 78% of the air in the tire is already nitrogen.
Simply dry the tire before mounting and use filtered air from the compressor. We have found that what
ever tire pressure we start with any increases work equally well. This may be a problem on the larger
asphalt tracks but has not been a problem for us on the dirt. There are some tricks that work and some
that don't. Use your own judgement.
NOTE: We have seen large increases in air pressure due to moisture and this could mess up your setup.
Check your tire air pressure when you come off the track so you have an idea of what is going on.
Tire temperatures. Tire temps tell you a lot about your car. Measure tire temps in 3 places.
About an inch in from the outside tread the center and about an inch in from the inside tread. Do not
worry about cold or hot temps, only the evenness across the face of the tire. Tire temps tell you how
that tire was hitting the ground. If your RF tire reads o-94 c-92 i-90 this is a good reading. This
means your camber is set ok and your tire pressure is ok. If it was o-92 c-92 i-92 than you have a
perfect camber setup at that wheel.
We have measured tire temps as low as 60 degrees on cold days and as high as 110 on hot days. Asphalt
readings are about 20 degrees higher. Here in Pa. we were snowed out twice at the beginning of 2002.
Even so almost 40 cars showed up. I doubt on those days tire temps would have reached 60 degrees.
Tire temps do not tell you everything but they will tell you a lot.
The following is not a complete list but it will give you an idea of what you are looking at.
If the center is cooler than the outside and inside it does not have enough air pressure.
If the center is hotter the tire has to much air pressure.
Front tires: If the tire temps are not even or close to being even you need to make a camber adjustment.
Example: RF o-98 c-92 i-90 this means you need more camber in the RF.
If you have a reading that looks something like this RF o-98 c-90 i-90 you need more air pressure and
add some camber.
LF readings. o-98 c- 92 i-90 This means you have to much camber in the LF. Remember the left side reading is reversed
from the right side. o is outside c is center and i is inside.
If the RF is much hotter than the left front the car will more likely be tight but you will already have figured
that out. Try taking out some wedge and get more weight on the LF.
Rear tire temps: The hotter tire is doing most of the work. We always check the rear tire temps. We only use the
rear tire temps to adjust air pressure and confirm what we already know about the car.
Camber: This is the one and only adjustment that makes your car look like a race car. The top of the right side tire
will tip in toward the motor. Neg. camber The top of the left side tire will tip out, away from the motor. Pos. camber.
For the dirt we use from - 3.5 to -4.5 degrees on the right side. On the asphalt we go to -4.5 deg to -6 deg. The left
side we only put in about +1.5 degrees to +3 degrees. You need to buy a caster/camber gauge
and slide plates to adjust your front end. The tire temp. gauge is critical to finding the optimal settings.
Camber settings are important for getting that max. contact patch on the ground when cornering.
This is also the adjustment that can get you in trouble with the 60 inch rule. So make sure you check with your
width gauge.
For road racing both left and right front wheels will have some negative camber. We do not do
any road racing so check with road racing people as to how much camber to use.
Caster: Caster settings help you get into the corner, and around the corner. This is an important setting.
Caster is the rotating of the front spindles forward and backwards. This is an easy adjustment on a Legends car.
We are still playing around with caster adjustments. You do need to have some tools. Caster/camber gauge and slide plates.
The general school of thought is to get about 3 degrees difference
between the left and right sides. Left side settings are from +1.5 degrees to -1.5 degrees and the right side from
-2 degrees to -6 degrees. Several things happen when you create this difference. The first thing you will notice
is the car will pull to the left. The more the difference the more the pull. The second thing is the car will be harder
to steer and you will need to hold pressure on the steering wheel to go down the straight stretches. The third thing that
happens is the left tire will turn more than the right tire which is good because when you are cornering the left and right
tires are on different arcs. The left arc is sharper than the right so you want the left to turn more. Check out the degree
reading on the skid plates. When you turn the right tire 10 degrees to the left the left should turn 12 degrees. Another thing that happens
is the right front will pick up. This causes weight shift changes. It also causes toe out changes. You have to pick a balance
between driveability and advantages of all parameter changes to suit the driver, car and the track.
Toe out: Toe out helps stability in cornering and helps to keep the car straight on the straight stretches.
If your car has a darting problem (doing some unexpected steering on its own) check your toe out. Toe out is an easy adjustment
to make. This is the one front end adjustment you see people making at the track using strings, boards, and metal bars.
Toe out settings range from 1/16th to 3/4 inches. We are using 3/8 to 1/2 on the dirt, less on the asphalt 1/4 to 3/8.
When you push down on the front end of your Legends car the tires will toe in. Use your god given brain here.
Lighter springs in the front the more toe out you need to compensate for this. The heavier the front springs the less
toe out needed. The faster the track the sharper the corners and a whole range of factors will dictate the toe out
amount. The disadvantage of toe out is front tire scrubbing and loss of speed. So pick the smallest toe out you feel
comfortable with. We have changed to heavier springs so we may be changing our toe out settings to 1/4 to 3/8 on the dirt.
Setting the toe out: You can buy a toe out gauge or make one. We made one but have since hung it up and use the string method
which is just as accurate and quicker.
NOTE: Centering the steering box can also be done at this time. Centering the steering box simply means setting the steering
box to center so you have equal steering to the left and right. We presently are centering the steering box. Not everyone
does this. Some prefer more left steering and run the car tighter. Some prefer more right hand steering and run the car looser.
We ran into the problem of the radius rods hitting the shocks plus we are trying to set the car for minimal amount of steering.
So we have no need to have more left or right steering. This is a drivers personal preference thing. What ever works for you.
Square the rear: Good golly miss molly, we got burned on this one. RULE 1. Never assume anything is square
or even on a Legends Car frame. This is a must do setup check. We raced most of 2001 with a cocked rear. The car
was pushing so bad that we became setup frustrated. It got to the point were we threw the setup book away. We jacked
weight around, changed springs, and finally decided to cock the rear. We thought we were cocking the rear but in reality
we were actually bringing it into square. When we stripped the body off during the winter we measured everything. We now
measure back from the front shock tower. (actually we put it on a hunter sonar machine and dial the rear in to 0 degrees
thrust angle.) Needless to say we started setup testing all over again in 2002. However cocking the rear is a racing trick.
Make sure when you set the rear you are within the 72 3/4" to 73 1/4" front to rear axle rule.
Front axle lead. To determine this you need to have the rear squared. Use your trusty 600 racing front to rear
axle measuring tool. and remember the 72 ¾ to 73 ¼ inch rule. This is something we are going to pay more attention to
in 2003. Again two schools of thought but here is the short of it. Longer right side the looser the car. The longer the left
side the tighter the car. We have found this to be a minor chassis fine tuning advantage. In the past we just adjusted
our caster, camber and toe out, got our 1/16th inch clearance on the lower A frame on the right side and ¼ inch on the left.
Where ever the axle lead was it was. In 2002 we tried some adjusting but we saw nothing that we could say, yes that worked.
Front to rear axle length or wheel base. The short wheel base of Legends make them prone to
spinouts. Once you start there is no returning. In spite of this the car is inherently tight.
There is some room for adjustment of the wheel base by 1/2 inch.. Not much
in the over all percentages. As a matter of fact the percent difference in change is .0045.
Which equates to 0 times 0 equals 0.
Here is the theory. The shorter the axle length the looser the car.
(Translate more prone to spinning out) The longer the axle length
the tighter the car. (Translate less prone to spinout.) The PRO gurus say shorter for dirt and longer
for asphalt. We say BS longer for dirt and longer for asphalt so there.
Rear axle shift to the left or right.. There is the 6 inch rule. You must have at least 6 inches
between the frame and backing plate of the wheel. We move our rear to the right for the dirt.
I am seriously thinking about centering the rear for one simple reason, which is---We race on dirt.
As the track dries out and for asphalt the PRO gurus say move the rear to the left. I AGREE.
The problem is, the track dries out while you are racing on it. So you need to make a guess about
future track conditions. Two things happen by moving the rear right. You get a little more side bite
which is a good thing on a wet track and it loosens the car up a little. Which may or may not be a
good thing. In addition if you change this at the track you also change your weight distribution.
So what appears to be a good thing may turn out to be a nightmare.
More rear end tricks. Pinion angle. When you stomp on the throttle you are sending 130 hp from
the engine through the pinion to the tires. As the tires bite and rotate clockwise there is an equal
amount of counter clockwise force on the rear end housing picking the front of the pinion up in the air. Radius rods hold the rear in place but what you are looking for is to keep everything straight. When everything is straight you get max hp transfer and thus better and more acceleration. We adjust the upper radius rod so the rear points downward in the static position. Use more because you need more on the asphalt.
You run into two problems on dirt, pot holes and ruts. With to much forward angle the drive shaft will
hit the crossmember and could cause the drive shaft bolts to break or damage the drive shaft.
This is also a traction enhancement adjustment. Not because of the pinion angle itself but because
of what happens when you get more hp to the rear wheels. The frame acts like a pivot arm and picks
the front up more causing more weight on the rear wheels resulting in more traction. This is a win, win
adjustment. But more is not
better. What you are looking for here is that the pinion and drive shaft are straight at max hp
transfer.
Springs. There are two ways you can handle your spring choice. Choose a set of springs. Then
dial in
the rest of the setup parameters to match them. Or setup the other parameters and swap out springs until
you get a match you like and can drive. Until we figure out the true relationship between the springs
themselves,
the weight distribution, engine power, front end geometry settings, ride height, front roll couple,
shocks, tires, added ballast weight, driver weight and driving style we are going to remain partially
mum.
Here is the Pro Guru's thoughts and what springs are supposed to do.
Lighter springs for the dirt. Better and more side bite.
Lighter springs faster weight transfer. Faster reaction times needed.
Some people are putting the lighter springs on the right. (it works for them)
We may be going back to lighter springs and a higher ride height. But first we are
testing other parameters. Plus we know people running and winning on the dirt with
heavier springs like (300, 325, and get this 350 on the right front.)
Heavier springs for the asphalt better weight control and keeps the tire
contact patch more even on all tires. (I believe this to be true for all dirt and asphalt tracks,
except a sloppy dirt track.)
Heavier springs slower driver reaction time needed.(That's me)I used to be fast in my younger day
but now I am only half fast.
Front roll couple. This is an important number to balance the slip angles of your tires.
There is a direct relationship between the FRC % and the rear weight bias %. FRC % is the total
front spring rates divided by the total of all the spring rates. We read many books that mention front
roll couple but none were specific and/or
gave a formula to figure out what the balance would be. We need more data to confirm our findings.
We do not have a formula nor did we develop one, but we did plot a graph with some good data but
we do not have enough data to claim this as gospel. Fortunately we had a variety of data which included
two extremes. We had both dirt data and asphalt data. We had both driver in and driver out of car
rear bias weights. We choose the driver in because we know with the driver in the car the rear bias
changes
considerably. From our graph we see the following. The higher the FRC % the lower the rear bias
needs to be. We need input data. All we need is the Front Roll Couple %, the Rear Weight %
(with the driver). Do you race on asphalt or dirt, and whether you win races, top 5, or how the car
handles. If we get more data and it complements what we already have we will post them here.
Shocks Don't get me started. The purpose of this web site is to promote the whole of the
Legends Series in a positive light nor do I ever intend to use this site for what I call political bitching.
I understand 600 Racing's decision and I applaud them for it. A healthy profit making 600 Racing means
a healthy prospering Legends Series. So in keeping with that spirit the best thing
I can do is direct you to Bilstein. They do a fantastically wonderful job hyping and
explaining their racing gas shocks.
www.bilstein.com/motorsports/oval.html
All I ask is when you finish reading the Bilstein information you mumble under your breath "Bull ----"
The only complaint I have is they bend and snap off while racing. I have 8 damaged shocks six
are from just racing. 600 Racing made a good business decission. In my opinion they just chose
the wrong shock.
End of Rant.
Shocks Let me start over. The Bilstein shock does have one virtue I like. Not adjustable.
This one setup parameter I can do without, no shock rebound and compression settings.
These are gas shocks, so make sure you are jumping up and down on the front and rear bumpers
getting the shocks to take their working set. Then do your ride height adjustments and scale readings.
Don't panic if you come out the next day and find your ride height rose by a 1/4 of an inch.
This is normal with gas shocks. Simply jump up and down on the the car to work the shocks and
they will return to their working set.
Mono tube shocks. Look to see if there are any dents in the body of the shock. Any dents in the body
render these shocks to the scrap heap.
Check you shocks for bending. Replace them if they are. If you have a mystery handling problem
especially if it is an intermittent handling problem. Check your shocks first.
To check the shocks, remove them and run them through compression and rebound, any binding throw them
in the scrap pile.
A weak spot in these shocks seems to be about 3/4 inches down from the threads on the piston shaft.
It appears a clamping machine (more then likely used to hold the rod while it gets threaded on the top.)
creates enough force to damage the rod at this point causing a weak spot. Most of our shocks bent
or broke at this spot but not all.
Mounting the shocks. These shocks can be mounted upside down. We mount the front shocks right side up
and the rear upside down. (I listened to some guy go off on hanging shocks upside down was an advantage
because of sprung and unsprung weight, bla, bla, bla.) We hang them upside down because it makes it easy
to get at the coil spring adjuster. The rear shocks we mounted on the outside of the frame. You may need to run a tap from the inside as the mounting was not
threaded all the way through. We ran the tap from the inside to keep continuity of the threads all the
way through the mount.
Shock rubbers, These are the rubber bumpers on the shock rod. They are not there to clean dirt like
someone told me. We use them to see how much travel these shocks run through when we are racing.
They can tell you a lot about weight transfer and how the springs are working. We slide ours against
the shock body then measure them to see how far they moved. You can get an idea how much weight
is shifting around. If a shock moves 2 inches and you have a 250 lb. spring on that shock you
know 500 lbs. at some time was shifted to that wheel. The other things it tells you is whether
you need heavier springs or whether you can run lighter springs if you wish. Not many people look
at these. We are doing a better job of monitoring them and pushing them back down between events.
More tech information coming. Keep checking back.
If anyone knows about any web sites with tech information please let us know and we will
post it here.
Contact jblack@noln.com
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