DIY cross weight - weigh and balance the car

[Frank818]

Since having an awesome engine super powerful with an excellent chassis and suspension is worth nothing if all this is not correctly balanced (weight), I figured I will need to do it, especially that I will put in a totally different engine, probably changing the weight distribution into a zone no one knows yet.

I thought buying a set of racing scales for $1000 and use them ONCE is a bit non-sense. It's a very costly tool for one use. Sure, I could try to sell it afterwards, but there must be some acceptable DIY methods that would be acceptable for a street car.

Then, why not going to shop that has those scales and pay to use them? Quebec, Canada, is not a place for racing (though we got an F1 Grand Prix, we love racing, but not too many people do race), and with only 8 million people (a tiddy over Mass) in an area 146 times Massachusetts, everything is quite spread around. Finding some shop that has those scales is very difficult if people you know don't know.

Another choice, I thought I could buy some cheap, but still 0.2lbs accurate, bathroom scales and use them. I don't mind doing the maths for cross weight, total, etc., that's free! But no non-bariatric scale seem to exist over 400lbs, as most people don't weigh that much (except if you eat fast food all the time and don't exercise). I could find some bigger scales for about $200, 750lbs each. Buying 4 scales doesn't make any sense, it's almost the price of a racing set. And having one scale might be a very very long process when you start to re-distribute your weight, as you have to move the car around and scale to each corner all the time.

However, at $15 per 400lbs bathroom scale, that is not enough, as all corners should weigh over 400 (they all eat fast food, you know). But why about commingling 2 scales per corner and dropping the car on some kind of wooden planks making a pedestal to distribute the weight on all scales. If 8 scales is too much to buy, then having 2 scales for 2 corners (4) might be possible. Of course I would still need to move the car and scales around but twice as often as having one scale on 1 corner. I would also need to lift the car on the other 2 corners at the exact height the scales are to make it leveled.

But all in all, for about $120-$160 shipped, what do you think of such DUI, sorry, DIY corner weight method?

[RM1SepEx]

Find a friend, scales are the kind of thing that you will find with your serious racing buddies. I have 3 friends that have nice scales that I can either borrow to use at home or go visit with a bucket of chicken and a six pack of beer. Don't buy cheap scales!

[gpaterson]

Good thinking about using smaller corner scales. It seems that you can buy 250kg (550lb) scales that would weigh each corner. In New Zealand they are not that cheap ... http://www.fishpond.co.nz/Homeware/Salter-Visibility-Electronic-Bathroom-Scale-No9064/5010777131345. This equates to about US$100 per set. You could also buy out of China http://www.alibaba.com/product-detail/comercial-parcel-scales_1386074591.html or http://www.alibaba.com/product-detail/platform-scale-300kg_2000902076.html?s=p for around US$60 each for a 300kg set.

[Frank818]

Well that's the thing about friends, my mech who used to race and his son as well and is still involved in what we call racing here, they know people who race for fun too, but none of them use scales. Hence why I am trying to find another way, until, if, I find someone with scales.

Why would cheap scales not be a good idea? Too hard to be accurate due to the way we use them?

[Frank818]

Alibaba requires 5 and 100 min order qty on the 2 links. :)
550lbs will not be enough for the rear and will still require 2 scales per corner. But would they be better than $15 scales? That I don't know, they all claim 0.2lbs accuracy.

[Wayne Presley]

Find a friend or race shop to scale your car if you don't have them. Check your local car clubs, someone may have scales

[Boog]

You could use a lever. Ignore my crude MSPaint-foo:
http://i.imgur.com/OSI8TUn.png
The theory is that on a level surface with a spacer the same height as the bathroom scale, the ratio of total distance over distance A is your multiplication factor for what your scale reads. [(A + B) / A] = Multiplication Factor
Ex: If distance A is 30 and distance B is 30 (half way between the spacer and scale): (30 + 30) / 30 = 2, so you multiply what your scale says by 2 to get the actual value.

If you want to use a 200lb bathroom scale to weight something with a max weight of 2000lbs, you just need a long bridge between the two plates and set your pivot point with distance A being 1/10th of A + B.

Things to keep in mind:
You need a stable structure with everything level. Its also hard to balance a tire, attached to a car of course, without at least two connecting rods for the tire to sit in. In the idealized form, you would use the centerline of the tire as the distance point, but in reality since the scale side is moving it shifts the contact patch and I dont know if this will change readings since a tire is flexible. For reasonable distances, a reading on the scale with the weight fixed at the inside of the tire vs outside of the tire would cause a huge change.

Your error factor gets multiplied as well. The scale you are referencing says withing .2lbs, which i'm taking to mean +- 0.1lb. If you were to use a 1:10 arm ratio, that error factor gets multiplied by the same value to become +-1lb.




In the end, I plan on buying a set of automotive scales. In the past i've take my cars to race shops to get corner balanced and it just makes sense to be able to do that myself. While the lever arm method works, its more error prone, takes longer, needs more space, and it is MUCH more dangerous. Please stay safe.

I suppose everyone has different priorities, and for many people it could come down to 'a set of auto scales' vs 'a set of bathroom scales and a new set of rims and tires'.

[Bob Cowan]

These are called Ruggle's scales. They are hard to find, but I think Aircraft Spruce still sells them. They shouldn't be that hard to make.

http://i13.photobucket.com/albums/a256/bobcowan/Rugglesscales_004.jpg (http://s13.photobucket.com/user/bobcowan/media/Rugglesscales_004.jpg.html)

http://i13.photobucket.com/albums/a256/bobcowan/smallOnthescale1.jpg (http://s13.photobucket.com/user/bobcowan/media/smallOnthescale1.jpg.html)

http://i13.photobucket.com/albums/a256/bobcowan/smallOnthescale3.jpg (http://s13.photobucket.com/user/bobcowan/media/smallOnthescale3.jpg.html)

[Boog]

Thinking about it a little more, if you don't care about the actual weight and are just trying to balance the car everything becomes easier. Similar to how HP numbers aren't as important as % gains.

It doesn't really matter what contraption you use as long as it is the same on all four corners and the result weight is within the range of your scale.

[RM1SepEx]

Why not cheap scales

time and effort, no repeatability, you will be chasing your tail. I went that route years ago... enough said :rolleyes:

I can laugh about it now

[Frank818]

Interesting points from all. I'll keep my options open, maybe simply reselling the automotive scales after that one-time use is a good option. Cheap is great, but being off due to technical installation errors and chasing my tail will not give the results I would want either. Some fast-food for thought...

[Wayne Presley]

You can buy a new set for as little as $725 and between Racingjunk.com and Ebay you can get a set for $600, sometimes less

[Evan78]

I think you can find someone in your area. I searched google maps for "corner balancing" in Montreal and found this place:

http://www.alignementgarbis.com/index.php/en/services/tuning

I then did a google search for Corner Balancing Montreal and see several forum discussions that may yield additional shops that offer this service. The shop I use in southern California charges about $100 for alignment and an extra $100 for corner balancing.

Here's a GRM article on corner balancing:
http://grassrootsmotorsports.com/articles/understanding-corner-weights/

[Frank818]

If I understand what I read about corner balancing, it may sometimes not be sufficient to tweak it by ride height adjustments. Since I'm putting in a completely different engine, I have no reference points, therefore I may need to move around some bigger parts, like the battery or AWIC's water tank in order to tweak the weight. I can do that only at 2 places, my mech's shop or at home. So I guess going at an alignment shop will not cover all possibilities for me. I would also need to tow the car there, as I can't get the car plated until I complete the car. If I need to move parts around, then the car won't be completed and not plated. Or I plate it without balancing and then may need to remove things I have drilled and fitted already. That time is worth money.

So I discovered I need practicality as well. :) I either need to borrow a set from someone or buy a set. I think I was not clear enough when I spoke with my mech and he misunderstood. I'll ask him again and ask him to ask his racing clients. Who knows... or I buy a set. There are others than Longacre, like Proform and sometimes yeah a (used or not) set can be found for under 750. Worst case I resell it.

[wleehendrick]

If I understand what I read about corner balancing, it may sometimes not be sufficient to tweak it by ride height adjustments. Since I'm putting in a completely different engine, I have no reference points, therefore I may need to move around some bigger parts, like the battery or AWIC's water tank in order to tweak the weight.

You're on the right track, Frank. Unless you get lucky, I expect your VW drivetrain to have a significant effect on weight distribution, Since it's going in mounted transverse, it'll likely shift the weight balance forward compared to a standard 818 with a longitudinal EJ and tranny sticking out back; moving the battery to the rear could help you there. The lateral asymmetry of the transverse motor/transaxle will probably require you to shift things around a bit, and could be tricky if it's way off, but as you say, better to address it in construction instead of trying to adjust out a big imbalance with ride height alone.

Or, you could just not worry about it and always race on circle/oval tracks!

[Frank818]

Hey wleehendrick, if you don't mind I'd like to move your response to my build thread, as my thinking was the exact opposite! So I'd like to hear your inputs. But yes, I feel especially in my case that I need something reliable and practical. Reading google it tells me Longacre and Intercomp are the best. Rebco I don't know and Proform seem to have inconsistencies and quality issues.

For the oval track, a bad corner weight seems to be bad too! Depending if you have wedge or reverse wedge, even on an oval it affects handling, hence your time. :) Weight balancing seems a lot more important than I could think of.

[wleehendrick]

but if you're only turning left, you can tune the suspension specifically for that asymmetrical condition. I'm no dirt tracker, but even the GRM article mentions that oval trackers set up with wedge and staggered wheels... helpless if they had to turn right!

[Frank818]

Absolutely! That's what I understood as well. My point was just that if I don't worry about cross weights, which means I won't know what they are, I still need to guess an oval that turns the right direction, if my cross weight is good for right turns, a left-turn oval will be bad. :)

[Slatt]

Just buy a nice set of scales, will ya? If nobody else beats me to it I'll buy them from ya next spring. Just don't drop that Hemi-Challenger on them, ok? Oh, that's not on your list of cars. This should work out fine for us both, Frank.

If you buy a good set then PM me so I don't forget my promise. :p

[Frank818]

Tnx Slatt, buying a set is the best option for me, I'll keep ya posted in the next few weeks/months. :)

[CHOTIS BILL]

Check out this option. http://www.speedwaymotors.com/DECO-Hydraulic-Wheel-Load-Checker-0-300-Lbs,230.html

Bill Lomenick

[AZPete]

Bill, the Deco load checker from Speedway looks good. Have you tried it?

[Frank818]

We would need the 0-1000lbs one, as the rear has quite over 600lbs per wheel for some and if your engine or stuff you are going to fit in the engine bay weighs more than the standard H4, you'll shot for 650+ for sure. The 0-1000lbs option has 20lbs increments for $190. Need 4, that's $760. I feel with 20lbs precision I'd rather pay an extra $300 and get 2lbs precision (1 tenth of a %). But that's a simple option for whoever needs 20lbs+ precision.

[Wayne Presley]

Bill, the Deco load checker from Speedway looks good. Have you tried it?

Really it looks good? To me it would be not as good as bathroom scales.

[Evan78]

Frank, it looks to me like you would only need 1. You just check each corner individually.

[Wayne Presley]

You do realize that you stick the point under the edge of the wheel then use the black bar to lever the tire until it's just off the ground and take the reading...
And you have to lift each tire exactly the same distance off the ground to get the correct reading...

[AZPete]

Wayne, it looks tricky and time-consuming but it's cheap. The sales info says lots of race teams use it, plus it's on the interweb so it must be true, eh?

[CHOTIS BILL]

I haven’t used one but remember seeing adds for them years ago. You only need one and the instructions say to use a piece of paper under the tire as a feeler so you know when the tire is just off the ground.

Bill Lomenick

[C.Plavan]

I'm looking at those bathroom scales and laughing. Way too much effort for "iffy" results. Just find a buddy or shop with scales. My buddies borrow mine all the time.

[Frank818]

I have a deal on a set of Longacre Accuset. From Canada, damn I would be lucky if I could get that one.

But the guy says it's the ACCUSET, not the ACCUSET II. Is there a difference really between them or it's the same thing just different wording?

EDIT: All I could find is this http://www.jegs.com/p/Longacre-Racing/Longacre-Racing-Products-AccuSet-AccuSet-II-Computer-Scales/2342119/10002/-1

- Memory recall feature in the Accuset II
- Slanted face for easier viewing in the Accuset II.

That's all? So both have 1/10% accuracy and both are as reliable and durable over time?

[D Clary]

I have used the deco checker in the past, I had little trouble with it. It takes a lot of time and practice to repeat result's. It also takes more than one person to jack and read the gauge. If you have a lot of camber the plunger will stick from the side load so you need to be careful of that. I used it for a few years until I bought scales. Cross weight is very important unlike oval tracks you don't want it on a road course so the need to know what it is is just as important.

[Jaime]

Frank, remember that cross weight really verifies that your suspension is set up with all the wheels equally planted on the ground. It has very little to do with the actual weight distribution of the car. You will be able to get really close to 50/50 just by adjusting preload on all four corners, even if the car is heavily loaded on one side. Technically, you should have the car statically balanced before you do cross weight.

Think of cross weight tuning as finding just the right thickness matchbook to put under a table leg. Just because the table doesn't wobble doesn't mean that it's loaded evenly.

[Bob_n_Cincy]

Gentlemen,
Can you get close on cross weight by adjusting front spring to the same length with a caliper?
Then repeat with the 2 rear springs.
I'm assuming the springs are in new condition and matched from the supplier.
Bob

[Tom Veale]

I used the UCDIY Scale Method on both my FFR Challenge car and also on my '33 Hot Rod. That stands for Ultra Cheap Do It Yourself Scale Method. I drove my cars over to the municipal garage area. They load salt by weight during winter months for road salting. The scales are only +or- 10 lbs accuracy, but that has been good enough for my usage.

It is amazing that even if we get the car ride height as exact as we can and the shock/spring adjustment as exact as we can we will find that the corner weights can be off considerably. My Challenge car was off by nearly 100 lbs in cross weight when I first weighed it. With these municipal "drive-on" scales I first weigh the whole car, next weigh just the front axle, next weigh just the rear axle, next weigh each corner independent of the others. Then it's just a matter of writing all this down on a diagram. Then I drive the car home and give the offending coil-over spring a half turn or so depending upon how far off the corner weights are with me in the car.

Next I repeat the weighing at the municipal garages. If my adjustment wasn't enough I repeat until the cross weights are as good as the scales will allow. If you think about +or- 10 lbs on a 2350 lb car it is a relatively insignificant amount.

This was the cross weights, etc on my '33 Hot Rod before I made any adjustments. It shows 40 lbs out.
http://thefactoryfiveforum.com/attachment.php?attachmentid=32645&d=1408480187
I put in about 1/2 of a turn on the FR Spring and afterward it was down to less than 20 lbs but more than 10 lbs in cross weight.

The UCDIY System has worked well. They've never questioned me or charged me. One guy came out and invited me to his monthly AM hot rod breakfast that I knew nothing about.

BTW, I also have done the same weighing without me in the car. The values change, but the bias really didn't change all that much. So, either way will work. If the car is going to be raced, then weigh the car with the intended driver in place. If it's a street car mainly, then either way will do.
http://thefactoryfiveforum.com/attachment.php?attachmentid=32676&d=1408555031

Best regards,
Tom

[FFRSpec72]

I have a deal on a set of Longacre Accuset.

I live just down the road from Longacre (as most of their equipment is tested just across the road at Monroe speedway) and they have good deals on refurbished scales, http://www.longacreracing.com/refurbished-products.aspx

[Jaime]

Gentlemen,
Can you get close on cross weight by adjusting front spring to the same length with a caliper?
Then repeat with the 2 rear springs.
I'm assuming the springs are in new condition and matched from the supplier.
Bob
Nope. One millimeter of preload is about 11 pounds of spring force. Just putting the scale on an uneven surface will throw it off. If you buy your own scales, make sure to rent a surveying transit to level them.

[D Clary]

you can level them with an inexpensive laser level

[CHOTIS BILL]

I level mine with a long straight square tube and a bubble level.

Bill Lomenick

[Frank818]

I live just down the road from Longacre (as most of their equipment is tested just across the road at Monroe speedway) and they have good deals on refurbished scales, http://www.longacreracing.com/refurbished-products.aspx

Lucky you. I checked the RBC catalog, not a bad idea indeed.
Tom, good method on the salt scales, overall cost of $0. Can't beat that!

So far the deal I have is for a hybrid Accuset Gen1 Basic system with upgraded Heavy Duty 3500lbs pads. For US$725.

32646326473264832649

The beauty of this is it's in Canada. I estimate about $200 in shipping, whereas if I buy from the States it's 200 to 450, depending on the place, plus I have to pay taxes on $1000, which is another 100-$150.

The kit works flawlessly according to the Subaru guy.

If you guys were me, would you think it's a worth deal?


EDIT: The 3500lbs/pad kit is worth $3500 new with 24' cables. The above has the 20' cables but still the big chunk comes from the pads.
Also in Canada we are very unlucky as we always have to pay shipping and quite more when we get stuff from US. I know you guys in USA can get a new 1100lbs/pad kit for $900-950 with FREE SHIPPING, but that's not our life up north here. :(

[Bob Cowan]

I'm looking at those bathroom scales and laughing. Way too much effort for "iffy" results. Just find a buddy or shop with scales. My buddies borrow mine all the time.

Laugh if you want to, but it works. They are definitely low tech, but that also means reliable, repeatable, and affordable. The same system is used for aircraft. Equipment doesn't have to be high tech and computer controlled to be useful. And it's a whole lot easier than hoisting each tire one at a time.


Gentlemen,
Can you get close on cross weight by adjusting front spring to the same length with a caliper?
Then repeat with the 2 rear springs.
I'm assuming the springs are in new condition and matched from the supplier.
Bob

Sometimes you can. The last time I weighed my Cobra, I started out by lifting each end off the ground, and setting the springs so they just touch the hats. Then I set the ride height by making the exact same adjustments to each side. Did same for the rear.

The ride height was not exactly the same side to side. There was a bout 3/16" difference side to side. But the springs were adjusted exactly the same.

After that I rolled the car onto the scales. After checking it a couple of times, the balance was so close I didn't change anything.


I used the UCDIY Scale Method on both my FFR Challenge car and also on my '33 Hot Rod. That stands for Ultra Cheap Do It Yourself Scale Method.
Tom

I like that! That is the difference - IMO - between hot rodders and check writers.

[Frank818]

Lucky you. I checked the RBC catalog, not a bad idea indeed.
Tom, good method on the salt scales, overall cost of $0. Can't beat that!

So far the deal I have is for a hybrid Accuset Gen1 Basic system with upgraded Heavy Duty 3500lbs pads. For US$725.

32646326473264832649

The beauty of this is it's in Canada. I estimate about $200 in shipping, whereas if I buy from the States it's 200 to 450, depending on the place, plus I have to pay taxes on $1000, which is another 100-$150.

The kit works flawlessly according to the Subaru guy.

If you guys were me, would you think it's a worth deal?


EDIT: The 3500lbs/pad kit is worth $3500 new with 24' cables. The above has the 20' cables but still the big chunk comes from the pads.
Also in Canada we are very unlucky as we always have to pay shipping and quite more when we get stuff from US. I know you guys in USA can get a new 1100lbs/pad kit for $900-950 with FREE SHIPPING, but that's not our life up north here. :(

Too late and too bad, I bought the kit. $CAD810 ($USD735) shipping included, no tax. 14,000lbs, if you got a couple of Hummers, I can weigh them all at the same time. No headache with this kit and all the money I've spent on the 818 will be optimized as much as I can optimize the weights, so I should be happier. Besides I know I'm gonna use it a couple of times during the build, in order to ensure I locate the components where I can balance the corner weights to the most optimized possibility. I really don't want to install something and then remove it, fix the consequences of removing it (holes, glue, modified panels, brackets, etc.) and install it somewhere else, modifying other things for a second time.

Tnx to everyone helping me understand the importance (at least to me) of corner balancing.