Landracing Forum
Tech Information => Technical Discussion => Topic started by: entropy on January 18, 2015, 06:50:08 AM
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Some of you fine folks have participated in TFA's 101-level questions about the construction and handling of our lil blue lakester.
As a result, setting toe accurately at the track is now on our list.
We recently bought a "Quick Trick" alignment tool and it seems pretty straight forward.
demo of it being used: http://www.youtube.com/watch?v=aadqjpyqlfs (http://www.youtube.com/watch?v=aadqjpyqlfs)
Q; does anyone have any tricks for using the Quick Trick?
Karl
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Dont know, but heres how to cross check your method.
Open wheel car...pretty hard to beat two jackstands, string, and a tape measure. That method also lets you check rear axle thrust angle, though its nice to do that with another pair of jackstands and more string. You should set the front wheels to zero while checkng the thrust angle this way, just to be sure you are dead straight to your Ackerman and scrub radius.
You're just running the string loop across the tire faces (wrapped around the back of the tire, tied off to the axle) and moving your jackstands in or out to get each side parallel. With the jackstands 6-10 feet (or a lot more if you have room) in front of the tires, you get very fine accuracy. You are measuring the strings, out front, to get them parallel, and then your toe-in shows as a small gap at the forward sidewall of the tire. Comparison check the tire sidewalls to the rims, to be sure you arent measuring a bulge.
With the front tires dead straight and parallel (no toe-in) you can pull string from the rears, passing the fronts, to measure for parallel and thrust angle. If the rear tires are narrower than the fronts, use wood blocks vertical to space out from the sidewalls.
Note about the wood block trick....pretty handy for using this method on fendered cars. Just make an H out of 2x4s that can stand against the sidewalls and pull your string loop. Dont fuss with string tension by retying....just slide a jackstand forward.
When you finish, do the water puddle trick on each side to make sure you are right (or that you werent actually straight...I've caught myself on that one). On flat concrete or pavement, pour a water puddle on the ground and hand roll thru it with the wheels dead straight. You can measure any offset right there on the floor when the front and rear tracks show on top of each other. (This old trick can be pretty discouraging when you just bought that brand new, whiz bang, super duty dually for a gazillion dollars. Just take a jug of water to the Walmart parking lot on a Sunday morning, drive through the puddle straight, cross your fingers and then walk back for a look-see.)
No matter how you measure or what tools you use, failing the water puddle test is the final answer for thrust angle. Flat ground and tires dont lie.
Maybe this is a dumb post and I am preaching to the choir, but sometimes we forget how well the old ways still work. A fellow starts getting a little gun shy when the thinking starts muddling with age, so I have to delete most what I write these days. :oops:
JimL
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Nice catch Karl .... $285 from Summit.
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Nice catch Karl .... $285 from Summit.
JimL
Thanks for posting ways to get to alignment without expensive tools. At the beginning I did my bikes with strings & jackstands. It worked, but i gotta tell you i cursed those pink strings more than once as i tripped over them :-D
Joe,
Credit Joe Timney, he apparently saw it at PRI? :cheers:
People seem to agree that each car is likely to have its own "sweet spot" toe adjustment. And that you can only get to that sweet spot by: make a pass/ make an adjustment, repeat, repeat as needed.
The Quick Trick might make it easy to make accurate adjustments on the salt; we'll see.
Karl
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Two things to watch out for.
First be sure that the surface you have the vehicle resting on is level. A laser level is probably the easy way to check that these days and floor tiles or squares of sheet metal are probably the easiest things to use as shims.
Secondly, all tapes are not created equal. Take both tapes and hook them to a common straight edge right beside each other. Pull them out to the approximate distance you'll be measuring. Check to see that they're measuring the same distance at that point. I've seen them vary by as much as an eighth of an inch. You can imagine how that can contribute to your sanity and handling if you measure twice and reverse which tape is where each time.
Have fun and buy a GOOD set of knee pads or get a younger helper.
Pete
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This type of system has been around forever in some form or another in the oval track world. The problem with it is you have no way to reference the wheels accurately straight ahead so caster, ackerman & scrub will all affect the results. Centering the steering wheel is "kinda close" so you will be "kinda accutate".
Sid.
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I made 4 brackets (2 at the front of the car and 2 at the rear)....
(http://purplesagetradingpost.com/sumner/bvillecar-2/12-7-07-7.jpg)
(http://purplesagetradingpost.com/sumner/bvillecar-2/12-7-07-8.jpg)
... that can be bolted to the car anytime, anywhere which will then...
(http://purplesagetradingpost.com/sumner/bvillecar-2/12-7-07-9.jpg)
...allow me to string the car. Of course this is a lakester (or might be one some day) so no body work in the way but will have to remove some to put the brackets in place.
More here ....
http://purplesagetradingpost.com/sumner/bvillecar-2/construction%20page-79.html (http://purplesagetradingpost.com/sumner/bvillecar-2/construction%20page-79.html)
Sum
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more good info, thanks!
Peter Jack
"Secondly, all tapes are not created equal..." Excellent, i NEVER would have considered that.
"buy a GOOD set of knee pads" I worked for 30+ years in a big corporation and am fully equipped with kneepads
KBT
"no way to reference the wheels accurately straight ahead" hmmmm... what is easiest way to do that? String?
Sumner
Thanks a million for reminding me of your excellent site!
Karl
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I like to use an aluminum "yardstick" with a built-in red laser (Harbor Freight, less than $10) in place of string. Place the thing against the wheel (or hub if the wheel is dismounted) and project the laser beam against a distant flat wall and mark that spot. To account for the laser's not being exactly aligned with the straight edge of the yardstick, turn it over on its back edge and mark that spot on the wall. Half way horizontally between the two spots will be the accurate "center"-- the actual data point. Do the same thing on the other side & measure the distance between the two data points.
Next, roll the car forward or set up a flat panel as close to the nose of the car as possible and repeat the procedure. If there is zero toe-in, the two measurements will be equal. Some geometry calculation will give you the toe angle if the measurements are not the same.
You can place the laser against the rear tire and see where it aligns relative to the front to check tracking. If you have an independent rear suspension like I have, you can also run a similar procedure to check the rear toe angle.
By placing the laser on the exact center of the body and aligned with its axis, you can tell if the wheels are pointed straight with the body or whether the car is "crabbed". The center-to-left distance should be the same as the center-to-right.
It helps to have the body off but the wood block spacer idea works just as well with a laser as it does for string.
Regards, Neil Tucson, AZ
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I made my toe checker out of 6 ft of 1 1/4" square aluminum tube . This is with the wheels removed . An 18" and a 36" are bolted together like a framing square with a hole in the short leg that goes on a wheel stud . An 18" one by itself goes on a wheel stud on the other side with a lug bolt on each . The in out motion with the long one laying against the single one is the toe . The stiffness of the tube makes the hubs turn together so it only takes one person . Things are in the way so I check it back 90* and 0* to the king pin axis and double the reading . The reading is at greater than the tread radius so I factor that in . A good level on the hub flange tells if if there is any camber to factor into the toe reading . From everything I've seen toe-in helps going straight and toe-out helps turning corners .
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Here is how I do it, it is simple, requires no bulky to transport equipment and can be done in the pits at the salt.
I use a piece of aluminum channel and two framing squares.
1. Mark a reference line on the circumference of the front tires by jacking them off the ground and spinning against the marking tool.
2. With the car on the ground roll it forward centering the wheels and taking out the slack in the system.
3. Slide the channel under the rear of the wheels and clamp the framing squares to it on the marked lines on the tires keeping the squares perpendicular to the floor.
4. Carefully move the rig to the front of the tires and with the squares again perpendicular to the floor align one square with either wheel reference line, at the other wheel reference line measure the distance from the reference line to the edge of the square. That distance is your toe out/in.
Note, the reference lines do not have to be in the exact center of the front wheel since we are only looking for a difference from front to rear not the exact tread measurement. Also since we are only measuring toe the car does not have to be level just on a reasonably flat surface. Another thing the circumferential lines molded into the tire never have zero run out so you can't use them as a reference.
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Thanks guys!
Much appreciated! :cheers:
karl
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Using JD's method, after an adjustment, roll the car ahead and remeasure. That takes out any slack, pre-loads the joints as JD said and is the toe the front end actually sees driving down the track.
Ron
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Using JD's method, after an adjustment, roll the car ahead and remeasure. That takes out any slack, pre-loads the joints as JD said and is the toe the front end actually sees driving down the track.
Ron
Ron,
THAT's exactly the kind of tip which can help my ignorant a$$ have a higher probablility to "do it right"
Karl
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Not sure that this applies to the Salt, but in our drag racing days in stock class we noticed from a picture of our car at mid track that the front was lifted about 4-5 inches from what it was on the starting line. We had set the toe at rest. We found that when we raised the front end to the mid track attitude everything changed. Camber and toe. Worth taking a look at.
Doug :cheers: :cheers: :cheers:
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Not sure that this applies to the Salt, but in our drag racing days in stock class we noticed from a picture of our car at mid track that the front was lifted about 4-5 inches from what it was on the starting line. We had set the toe at rest. We found that when we raised the front end to the mid track attitude everything changed. Camber and toe. Worth taking a look at.
Doug :cheers: :cheers: :cheers:
TFA lakester is front wheel drive, without suspension and only 350-ish hp, so i'm guessing lift will be minimal????
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Doug;
That's called "bump steer"-- toe change as the wheel goes up and down. Not good. Lots of bump steer makes handling squirrely.
A well designed front suspension should have less than about 1/16" toe change as the wheel goes up and down over a 2" travel.
Regards, Neil Tucson, AZ
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july, 2015 followup for the Quick Trick kit to set toe in
I received the kit and it is beautiful. Works by clamping a frame onto the outside of ea wheel. It has bars parallel to the wheel but very low to the ground so that a tape measure can measure the distance before and after the front axle. The difference in those measurements = toe (adjusted for wheel size).
The idea is simple & straight forward
But...
the process depends on perfectly & consistently clamping the frames to the wheels.
TFA's wheels are custom made and the lips where the device clamps onto the wheel are not quite a "factory" profile. Tiny mounting differences = big differences in measured/calculated toe.
so...
I couldn't get consistent/reproducible results anything near the targeted 1/8" toe in.
For factory wheels the Quick Trick alignment probably works perfectly.
At that point i was 100% more knowledgeable & sensitive to the difficulty in accurately setting toe.
so, google introduced me to Mike Loescher of TrueLaser Track
http://www.truelasertrack.com/trihub.htm
Mike's hub-based laser tool allows even me to set toe REPRODUCIBLY to about .020" (or less) of target even in my restricted length garage. I only can get 7' clearance in front of my f axle. 14' gives much better accuracy
It obviously ain't cheap, but it is VERY SATISFYING to use.
karl
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Glad to see you found something that works for ya Karl.
Now that you have accuracy you might want to start out with zero on your FWD, 1/8 in will probably be a little washy on the salt.
Sid.
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Glad to see you found something that works for ya Karl.
Now that you have accuracy you might want to start out with zero on your FWD, 1/8 in will probably be a little washy on the salt.
Sid.
Sid,
Even with the TrueLaser Track (TLT) it takes a bit to develop a methodology which consistently gives high precision results. Randy & I practiced, did about 10 measurements, then read the directions (manly behavior!). In only 5 more measurements we got pretty consistent. About 45 degrees of twist on the tie rod end predictably gives about .045" toe change, more or less.
The point is that I feel kinda confident I could set toe in to about 1/32nd (.031") if that was the target. But from previous posts, i got the impression that there was a reason (handling?) that folks pretty unanimously like toe in = 1/8th (.125") for salt. I think Mike at TLT said he likes 0.000, but he readily said he knows nothing about salt.
hmmmmmm....
Start with toe in very close to zero, or start with current setting (.117"), that is the question.
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I'd definitely start with zero toe with the front wheel drive. Anything else is probably going to produce some form of wandering.
Pete
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Zero or just a fly $hit of toe in to be sure you dont have some toe out is a good start point for a (driven) front end, it's a kinda safe place to start out. From there you can make small adjustments to see if you can improve your vehicle & like I've said before, this is not a fits all situation.
Sid.
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Under power a FWD will try to toe-in so starting with an initial toe-in probably isn't necessary. It depends on the compliance of your front end, though.
Regards, Neil Tucson, AZ
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Everything I've read says toe-in helps straight line stability .
Neil I don't agree that FWD causes toe-in . With FWD the contact patch ought to be inline with the steering axis so no compliance toe change .
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FWD pulls the front wheels forward so that takes up all the slack in your ball joints, heim joints, etc. It also slightly distorts the suspension since it isn't infinitely stiff.
Regards, Neil Tucson, AZ
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That all depends on how much caster you give it. More caster tends to induce toe in and works in conjunction with the FWD to force toe in. If you use positive caster and 0 toein you should be good to go. If it tends to hunt a little add a little toe. [Combination of wine and science].
Doug :cheers: :cheers: :cheers:
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Thanks much guys. :cheers:
Somehow i got toe in = 1/8" fixed in my head. Everyone was telling me go much smaller and i just didn't hear.
dumb-azero me.
karl