In this case I was bottoming badly and had to raise the whole car, and touching the back of the car at the track without a platform is inviting trouble. In retrospect I should have just raised the front and dealt with any handling issues that might have come up from decreased rake differently.
Yep. Kirchner, build an inexpensive platten. I have plans for the one I built, if interested.Originally Posted by mark elder
V/r
Iverson
IMO the setup platform at the track is only necessary when you are trying to get back to a known quantity (after replacing bits and pieces, a serious off, or you've tweaked and tuned so much in frustration you just want to return to a baseline). There's no real need to turn this widget 2 flats or the other one 3 flats and then put it back on the platform while at the track. Keep copious notes of all the changes you make and once you are happiest with the car you put it on the platform and measure everything. That becomes your new baseline for when you roll off the trailer the next time you're visiting that track under similar conditions.
It really doesn't matter where the numbers all end up when you are happiest with the car, only that you can duplicate that set up.
That of course was what got me here....
I would suggest that it is best to get your scales setup at the track and balancing the car before the first practice. That opinion is based on working at the professional level for several decades.
My practice was to do the complete alignment at the shop and get to the track, setup the scales and balance the car. That way I knew where I started from and where my changes took me. This was standard practice at the oval tracks where setup and balance were all important, way more so than at road courses.
You also need the platform at the track to see where the weights and ride heights ended up at the end of a session. If you not do a "set down", you have only one set of data points to work from, which will get you nowhere.
I'm suggesting that the car come off the trailer ready to go.
I'm suggesting we learn what effect all the adjustments available to us make on the platform in the shop. We can then tune the car to our likes/changing/anticipated conditions at the track by turning knobs and adjusting widgets. We don't need to know if we want 8 more pounds of wedge/crossweight or .5%, all we need to know is that 4 flats in the LR is a big change, 1 flats is not. We can measure our new baseline for those same conditions later.
Billy Bob and Jethro don't scale the car at each pitstop, they know what a bump rubber does or 3 turns of wedge, a 1/2 psi in the RR, etc. They can duplicate each of their tunes back at the shop on the setup platform and know what the new starting point is for next time they encounter the same conditions at the same track.
Daryl;
You may have a point. But if one starts changing springs or doing a lot of ride height and rake adjustments, I think the scales are really important. It is real easy to make an adjustment to a push rod and move one side down and the other side up. When the car goes back on the track, the mistake will likely discovered but the track time is lost. That mistake would have been caught on the scales.
One nice think about setting the scales up at the track is to check that the car survived the trailer trip to the track with out changing any of the settings on the car. And when you start testing you really do know your starting points.
I am speaking about how I do things as a professional who is getting paid to go racing. As a club racer, I would probably follow your advise, unless I was doing a serious setup program where the scales would be necessary. When I am working on a car setup, spring and ride height changes are the first thing I start doing and to do that well the scales are necessary.
Understood.
I use a digital level and a laser when setting up my pads. For me having a second system (laser) is easy to set up and increases my confidence everything is accurate. As expected, there are lots of options and opinions on what is acceptable for how to set up your pads. If you feel your set pad height is correct, but what some confidence, remove the car and put it back on the scaled in the opposite direction. You should have the same readings. I've done this process on my car twice, was with in 2 to 3 lbs.
I thought this for a short time, but then realized (I think), if your scale pad is diagonally twisted, yes, you'll get the same readings, but you haven't proved the platform's four pads are level to each other (,right?).
Racer Russ
Palm Coast, FL
I think the point is that they are level enough to be within the scale accuracy limits and therefore, repeatable.
Garey Guzman
FF #4 (Former Cal Club member, current Atlanta Region member)
https://redroadracing.com/ (includes Zink and Citation Registry)
https://www.thekentlives.com/ (includes information on the FF Kent engine, chassis and history)
Russ, from what I have found, if my pads were off (front and rear pair) were not parallel but twisted, and I was putting 6 lbs extra in the RF wheel, when I rotted the car that 6 lb difference was gone. Hence the additional weight on the RF and LR were canceled out due to the pads not being parallel. If my pads had been twisted in the opposite direction I expect I would have seen a larger cross weight difference. Again my point being what ever process you use to set up your pads, If you can rotate your car and still get the same reading +- 1-2 lbs its a sanity check that your process is sound. If you don't something is wrong.
If your scales are diagonally twisted (one or two pads higher than the others) you will have different cross weights when the car is oriented the other direction. If you were 50.5% LR+RF and then pointed the car opposite direction you would get 49.5% LR + RF. If you still ended up with 50.5% then your platform is level (enough).
Here's a thought...
As long as you are using bias tires, you almost have to have a pad at the track. The tires are not consistent in size so you have to change setup with each tire change. Just saying.
If you have spent a lot of time setting up the car, and kept copious records of what one flat does, And, you are good at math. You can try to measure tire circumference and calculate ride height changes and adjust. But, trust me, its a lot easier with a pad and scales.
YMMV
YMMV - yes. i found Avons to be extremely consistent in size between front/rear pairs. The other thing I've found is that after a couple of sessions they are pretty much identical.
What caught me out in this event was that the fronts, while pretty consistent side to side, were 1/4 inch smaller in dia from the last set (different compound) and the rears about 1/4 " bigger.
Stupidly, I didn't look at my records until after re-setting ride ht, or I for sure wouldn't have touched the rear.
That would depend on how easy it is for you to set up the pads vs. dividing a tire circumference x 6.2832
It would also depend a great deal on what parts of the racing weekend you enjoy more than others, and with the finite amount of time on a giving weekend, where you are going to get the best ROI. Some get a great deal of joy out of the process. Others are tripping over dollar bills to pick up nickels.
a 1/4" of rollout difference is about the .040" ride height difference that Rick's fighting.
1/16" of rollout difference per .010" ride height difference.
The tire likely changes more than that during the course of a race between wear and pressure increase.
Getting the car close enough on the set up and driving around little issues, race craft and how one deals with changing conditions will have a much larger effect on the outcome than splitting hairs on the set up pad. At least at this level. 90+% of club races have winners and losers separated by more than 1 second a lap.
That sounds incorrect to me.
Let's say your car has perfect 50% cross weight, like 200 lb. on both front wheels and 300 lb. on each rear (if you weighed it on someone's perfectly level scale platform).
Then you rolled it off their platform and over onto your platform, nose first, and it reads 55% on the RF and LR.
So, let's agree at this point that your platform is not level.
You then backed the car off, turned it around 180 degrees, backed it onto your platform, it would still read the same 55% wedge. It would not read 45% on the RF and LR, because those two corners are still the heavy corners.
I think that means you cannot verify platform levelness by changing the direction of the car.
I think it would work if your scale platform was a square (as opposed to a rectangle), and you could turned the car 90 degrees. :-)
Racer Russ
Palm Coast, FL
What it would actually read would be dependent on how out of level your platform is and where the high spot(s) is(are).
The heavy wheels won't read the same (when car is oriented 180 degrees opposite) on an out-of-level platform because more weight is being transferred to opposing scales as the car leans/lists. The problem is worse the higher the car CoG and how out of level the platforms are. As a matter of fact, you can calculate the location of your CoG by utilizing platforms that are purposely out of level.
Visualize the extreme. Weigh car on scales that are on a 89 degree incline, then turn car around 180 degrees and weigh on the same 89 degree incline. I guarantee the heavy end of the car will always be the end on the lower pair of scales regardless of which is actually the heavy end.
If only there was just a 1/4" difference in bias tires...
I measure every tire to a 64th, have a Pi tape. I don't believe I've ever had Avons off more than 1/8 side to side. I really only scale the car once a year or so as a result. Until recently, all the tracks out here have been pretty smooth, and I just run it as low as I can.
Especially with tires scavenged from the take-off pile....
“Racing makes heroin addiction look like a vague wish for something salty.” -Peter Egan
Interesting comments. I have nothing to add, except to ask, am I the only guy on here who is till racing, and never had a set up platform?I do have heavy duty bathroom scales for really heavy people (400lbs), that I use in the garage. When I started 50 years ago, some folks used grain scales.
Jim Gustafson
Never had a platform, had access to scales when road racing. Had a ruggles type system back in the 90's for a 1000# car circle track car. Also crewed on a multi-race winning Southwest Tour car back in the early 90's that didn't even own a set of scales. Done with strings, bubble camber/caster gauge and a wheel load checker thing, like they still sell at Speedway. That was a 6-figure annual budget car racing in a series for decent purses, with some success.Interesting comments. I have nothing to add, except to ask, am I the only guy on here who is till racing, and never had a set up platform?
Jim Gustafson
Key is the track conditions are never the same. You unload close enough and know what adjustments to make as you chase the track/conditions. Don't have to get it perfect, just better than those you're racing against
No platform here. I use the same sort of scales (front weights only)...mine are 300-lb capacity and give a new reading every time I press the button in front.... am I the only guy on here who is till racing, and never had a set up platform?
Jim Gustafson
And I use my home-made toe-measuring ("U-shaped") bar (equal-height ends) with my home-made camber gauge to make sure my floor is level and shim it if it's not.
Dave Weitzenhof
I don't really have a platform. What I have I call the "hillbilly platen".
Got a smokin deal on some reb-co scales 15 years ago. A friend of mine had purchased a set of Rahal's old mid-80s indy scales, but holy crap - at nearly 200 lbs/bridge they really weren't very convenient.
I just welded together some angle iron with hex stock on the ends for levelers. Years ago I had made some very long ramps to get the car into my toyhauler - these were 4" thick boxes made from OSB, white wood, construction adhesive, and must have a thousand deck screws in them. I cut those to the right length to carry the car from rear to front. Used my trailer ramps to get the car onto the scales. Leftover pieces of the box ramps serve as roll-offs.
For the ground reference I had sheet steel cut and place that on top of the scales to set ride ht before corner weights.
But - it is a royal PITA to set up and use. It was relatively cheap.
Dave W your set up looks just like mine. I also use the scales on the front only. Luckily, my garage floor is almost perfectly flat (side to side). I use jackstands and string for alignment. Camber/castor gauge is made up from a couple of items from Menards. For most of my racing career, it was just my wife and I at the races. No way I would have the time or energy to carry around and set up a platform at the track, with all the other work that a race weekend demands.
Jim Gustafson
Jim, I'm just too damn lazy to have a platform at the track. I agree with Daryl (there's something I didn't expect to write today
) in his earlier post, in that I try to have the car ready to roll as it comes off the trailer. The only time I've needed a set up platform at the track is when I've wiped a corner off of the car (thankfully not that often) and need to check to corner weights post repair. There's never been a shortage of larger (pro) teams willing to let me rolI onto their pad when needed. So far!
At home, I use a set of Longacre scales, bought second hand 20 years ago and split with my local pal Steve, a stack of composite carpentry wedges, some plywood squares, a 6 foot level and a length of 1" square tubing. I even went to the extraordinary lengths of making a couple of set up bars for the RF90, thus dispensing with the jackstands. In my view, this system gets the car well within the zone where the driver can contribute more to faster and consistent lap times than can a more sophisticated set up system.
Having said that, this thread has been a treasure trove of insight on all things set-up related.
cheers,
BT
Sounds like me, also. Too much work and not enough trailer or shop space for a scale platform. At best we have 1 crew besides Sherrie. So a lot of the time, especially for the FRP series' with sometimes 4 sessions a day, there's no time to fool around setting up and using a scale platform.
Most weekends, we have no use for it anyway. I have spreadsheets of spring change effects, etc., so I do setup by calculation. Has worked for 40+ years w/o screwing up the handling.
Dave Weitzenhof
We spend $ on stupider things..
Car raised on lift above pads/scales at home...Wheelbase on my 94/5 VD = 96 & 3/4 inches....so...
why not 2 96" long levels [they sell 'em] and 2 77" [or so] levels set on the pads....and get 'em all level.....remove levels (duh) ....lower car onto pads. Push up and down, roll off & on....etc. work on set up. Raise, string, jack stands and bars and camber gauge, lower and raise and roll off and on as needed...cross weight....repeat....but don't lather...
Key is 96"& 70 something long levels and a lift
I had an accurate pad/scales at the shop and set up the car for whatever track i was going to.
But, when I went out the door, I had documents/charts already made up that told me what each "flat" turned would produce in terms of ride height, toe, or camber. The ICP schools taught me to practice all that stuff at home and record it. And I wrote all the track changes down. Then, on return I would put car back on the pads and re-check. Then I would re-set for next track.
I made alignment/string bars for each car and they traveled with the trailer. Camber was easy to do at the track also.
I cleaned tires at the track and measured. If tire size changed, then I could adjust ride height for any corner change by doing the math and adjusting using my charts.
Luckily, in something like 100 races I had no DNFS, so I didn't need to do suspension swaps at the track.
That was all well and good. But, I wasn't winning major races nor pro races. Last weekend, I watched winning pros roll cars onto scales all day long. Just saying.
I suppose that with aggressive drivers, pounding the curbs all the time and with an occasional off, scaling gives the assurance that everything is the same.
Back when I was officiating for USAC, there was a garage at the back of the old Indy Garage area with a Bear alignment rack in it, staffed by some Bear guys. I bet now everybody does it in their garage, on their own rig. Less opportunity for people to hear about your speed secrets that way
Details
So....
When "scaling" the car:
1) Do YOU sit in the car (in full dress and regalia), have someone else sit in the car, weight it with sand bags or other weight or....?
2) Full fuel load, partial or empty?
3) Full bodywork?
With YOU sitting in the car, have you ever performed these movements and noted corner weight changes:
1) Leaning left or right, as if hard cornering?
2) Moved your left leg from the dead pedal, to the clutch pedal and then to the brake (yes, under the steering column)?
John Mihalich, Jr.
Lotus 61/FF/28
I put weight on the car just in front of the main hoop equal to my weight + a few lb of downforce (214#). Also ~17# on the front to compensate for having the nose/crush box/wing ass'y off. All the bodywork is on with the exception of the engine cover and tail-piece + nose ass'y. Full fuel tank. I also do the alignment (ride heights, chassis angle in rear view, cambers, toes, swaybar preloads - usually zero), in this condition.
However, having said all that, it really doesn't matter as long as you do it the same every time and keep records of it and how it worked. And I've never tried to determine the effects of moving my body around because its effect would be negligible, IMO.
Dave Weitzenhof
What I usually do, is put a series of weights in the car, arranged in such a way to get as close to the weights I see with ME in the car - at least on the front end. I'm about 10-20 lb short on the weights - which are lead/aluminum/zinc alloy anodes from a gold mine plating operation. They weigh between 7.5 and 10 lbs each, and each is numbered and marked with a centerline.
I usually use this to set ride ht, and then take the weights out to set corners, figuring that taking the weight out removes any inaccuracies in placement. Then I put it back in for alignment.
However, what I found this time was that since more of the driver's weight is on the rear of the car, and the inaccuracies are more easily magnified back there, a normal symmetrical installation of weights would not work. I had to stack them pretty asymmetrically to get the weight on the front the same as with me in the car. That was a real surprise.
But it worked - when I got back in after scaling the front was spot on and the back pretty good too.
I usually do all this without bodywork and empty of fuel. I tend to start off slowly, and get a lot faster as the session goes on, so I prefer having the car come to me at the end.
Dead pedal? Not in a VD with size 12.5 feet.....
Driver movement does have a surprising effect. Especially for men (if you've ever studied the different dynamics of men skiing vs women). We have all that weight sitting relatively high up.
If you can move enough in a formula car to affect the corner weights more than a few #, you need to revise your seat to keep you better located. Being loose enough to move much is, IMO, a deterrent to driving properly and can be a safety issue.
Dave Weitzenhof
^^^ Exactly ^^^
The caveat here is that if you are shooting for a particular known set up given to you by somebody else then you need to do it the same way they did.
Set up X and alignment Y with you in the car is not the same as it is without you in the car. Set up X with some of the bodywork off, to facilitate adjustments, isn't the same with some of the bodywork on (as raced).
Yes, moving around in the car makes a bigger difference than a platform out of level .040" that we spent lots of bandwidth debating does. Your 40#left leg on the brake or moved over 4" to the left can change your cross weights a several pounds.
I found it best practice to start with a known good set up with me in the car, and then take all those measurements unladen. Now I don't need to be in the car to duplicate a particular set up. The process only needs to be repeated if my weight changed more than a few pounds or I did something to change wheel rates.
Somebody could measure their alignment in radians, or their corner weights in stone or regulation ping pong balls for that matter. As long as they are duplicating their process it will work and nobody will try to copy your set up notes
How many folks measure their toe in inches vs. degrees? What do they do when they change tire sizes?
Body weight shift
Moving a 40# leg 6" (the whole leg, not just the part that moves laterally) with a track width of 60" gives 4# weight shift. I.e., 2# off one side and 2# onto the other. This is divided between the front and rear in a ratio dependent on the wheel and tire rates unless your frame has very low torsional stiffness, and that's a whole other issue. So that means somewhere around 1# weight change on any one of the 4 scales.
To me that is well within the error level one could expect even if everything else is almost perfect. As I said above, that is pretty much negligible and not anything I'd worry about. And even if you could, which extreme would you use?
For most setups getting cross weight equal within 5# is acceptable as long as the chassis is not tilted L or R in the process.
Dave Weitzenhof
Perhaps I am overthinking/or "underthinking" this. I believe moving 40# 6" has the same effect as moving 4# 60". If we move 4# from on top of the RF tire to on top of the LF tire (60") it's a net change of 8# (the RF gets 4# lighter and the LF gets 4# heavier).
Obviously we aren't moving our entire 40# leg, and we are likely only pivoting at the ankle/heel depending on foot box size.
I'm just saying we are after repeatability and someone moving around or varying sitting position has an effect that we should be aiming to eliminate (it's low hanging fruit).
I leave my simulated driver weight installed for the entire alignment process, certainly doing corner weights. My corner weight numbers without driver weight are massively different, and I would not even bother to check them, for any reason.
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F1600 Arrive-N-Drive for FRP and SCCA, FC SCCA also. Including Runoffs
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