Want to put the car on scales: Need Opinions

[gverelli]

Well here is the story, I didn't just buy coilovers for the higher spring rates or lowered drop, I wanted to take advantage of the fact that I can attempt to make the car perfectly balanced. Before I go on, the car is a daily driver and weekend HPDE car. My goal is to have it as balanced, while making it lighter at the same time. My plan is to remove A/C and components (30lbs?), remove rear trunk tar (40lbs?), and maybe remove the back seats (30lbs?). Spare and jack already removed (40lbs?). Its an m20, and the registration states it weights 1380kg (Which seems like a lot to me...)

That said, I want to get the car on scales to improve the overall balance of the car. I am a noob when it comes to corner weighing so any editorials will be great, and for anyone else as well who wishes to do this in the future.

As I understand, getting the front/rear and left/right weights is for a pure track car where ballast is actually moved around to achieve 50/50. And for a non-track car the cross weights is what is important. Double check if this is correct, I may have misunderstood.

So the key points Im looking for are:

-Is it worth the time and money? I have heard mixed reviews on this...

-Will taking out the trunk tar/spare really make the weights off that it will be harder to achieve a perfect balance?

-Is it recommended to leave as much weight in the rear as possible to keep it balanced?

-Should I first balance the car as-is to see what my starting point is, to see if it is even worth it?

Thanks for the input. Any help will be great.
If anyone else has questions, please join in.

[rThor432]

First thing I will mention-- If you have coilovers you absolutely should set the car up using scales. That is why you bought them. My S52 E30 corner-balanced with perfect cross weights @ 50/50 LF-RR/RF-RR with static springs and me in the car (a rare case I think). I corner weighed 3 other E30's that night and none of the others were perfect, so that is why some guys go to coilovers, like you have, for the adjustability to reach perfection.

When setting up a car, do not forget to set the ride height initially and pay close attention to that as you make adjustments.

Cross weights are important on any car-- When setting up a car, we allow for a maximum delta of .3% with the final cross weights. I personally alway finish a corner balance job with perfect 50/50 cross weights-- there is no reason not to with a fully adjustable suspension. Having an F/R balance that is close to 50/50 is nice, but the best way to adjust that is by moving balast around. That figure will change a bit when adjusting the springs though, but not a ton. Keep in mind that Porsche's have been winning big races for many years with 35/65 weight splits so F/R isn't really as big a deal as some will make it out to be.

On to your key points--

-It is worth your time and money. It takes a while to get the car perfect with a lot of fine adjusting after the rough adjusting, but it is well worth it in the end. All of the experienced DE and race drivers that I work with are extremely happy with the results after driving the same setup on the track without corner balancing.

-This depends on your definition of perfect balance. It will affect your F/R balance, but in the grand scheme of things your car is already very well balanced compared to other cars (makes) out there. My E30 with no spare or trunk tar and an S52 engine up front (+100 lbs. on the nose) was 52.3 F/47.7 R @ 2,600 lbs. with me in the car. Compared to an M20 E30 that was set up similarly it was effectively +1% to the nose.

-Some will recommend leaving weight in the rear for a closer to 50/50 balance. I would ditch the weight and drive it. You can always add balast back in, but like I said earlier look at how skewed Porsche F/R weights are typically and they drive very nicely on the track.

-You will have the car on the scales anyway, so you might as well see where you are and go from there. You will likely have a nice F/R balance with the M20, especially if you decide to leave the trunk components in.

At the end of the day the decision is still yours to make as far as all of this is concerned. Also, because I know how varied people's opinions can be on this subject I will say that this is all based on my experience and personal opinion. I work for a Porsche/BMW motorsport shop and do a lot of track preparation and setup as well as track support, so I draw my opinions from that.

[jlevie]

Both ballast and spring adjustments will probably be required. Getting the cross weights the same is slightly more important that front to rear balance, but you really want both to correct for the best handling. A half a percent off (front 50.5% & rear 49.5%) would be acceptable for balance if the cross weights are the same.

[nrubenstein]

I'll have to disagree, Jim. In a BMW, pulling weight is more important than getting the balance perfect. Gt everything out and corner weight it. Obviously, if you HAVE to add weight for rules compliance, then you want it in the right location.

[gverelli]

@rThor432
Thanks for the explanation, that was extremely helpful and I hope others find it helpful as well. I think you have convinced me to lighten it before going, and then get it weighed, if worse comes to worse I can add my spare tire back. Like I said at 1380kg I feel that it can be better than that. My only concern is that I need to find a reputable race shop around my area.

One thing, you mentioned to make sure to the ride height is set before I go, so I have to set it how I would prefer it to look and then bring it?

@jlevie
I understand what you are saying in regards to cross weights and front/rear balance. However, I am not sure about the actual ballast part, like I said it is not a race car so I am not sure how all out I can do inregards to moving things around. Is it possible to adjust only cross weights and still have a positive affect without moving ballast around?


@nrubenstein
I see you were refering to Jim in regards to what he stated. For me personally though, it is not a race car, it is still my daily so gutting it will not be an option. Only the basic things I mentioned above is what I am willing to remove, if it is necessary. I do want it to be light-er but it is not a race car in my case. Thanks again for your input.

[L8 apexr]

You can't alter front to rear bias when corner weighting,you change the load on each wheel to get the crossweights but the total weight on the fronts/rears remains the same.You can rake the ride height to the front or rear and make a small change or obviously move stuff,keep in mind nearly all cars that are lightened gain in front weight %.

[rThor432]

Hey, I'm posting from my phone so this will be brief--

Setting the ride height has nothing to do with the 'look' (rake/stance/etc.) of the car but rather deals with the precise measurement of compnents of the car to other components or the ground. I have some factory literature that I will post up here later that will give a good pictoral example.

[NigelStu]

Yes - it is worth getting the cross-% balanced.

I would personally go with less overall weight, but with center of mass type things (rear seat/spare tire) - experiment, as there will be minimal cross% change. Run a session with that stuff in, then run a session without. See what feels better AND is actually faster on track.


The beauty of coil-overs is that you can change the set-up easily. So if they are on now, get some weight out of the car and set it up. When (if) you take more weight out, you can do it again with a simple twist of a spring collar or 2.


If its just a DD/HPDE-day car (aka, no timed events, just having fun on the track), cross % is most important and you probably wont have much of an impact with FR/RR balance. Set it up as you will be driving it on the track (extra crap out of the car, you sitting in the driver seat with you helmet on, tire pressures set to what you want them to be when HOT on the track, etc.).

50 % LR/RF and zero rake is the perfect starting point. Pay attention to your ride heights. Adjust from there for speed and driving style.

Keep in mind these 3 things:
-Set you alignment (toe/camber/caster) before you do corner weights. And re-check after.
-cross-weight % (wedge/de-wedge) will control which direction the car turns 'better' in.
-rake will have some impact on turn-in/turn-exit behavior.

[gverelli]

@rThor432
Ok I will wait for the illustration for better understanding. Are you referring to i.e. the front CA arms being level to the ground?


@NigelStu
Thanks for the response, there is very good information in there. To start off, yes the car is only HPDE/DD car. Thus, no time laps etc.

Before I had the coilovers, I had experienced with removing all the extras out, and to be honest (maybe it was a placebo), but the rear tires would break lose much easier and the car did "feel" quicker, and my entry speeds were increasing slightly. However, it may have been because I was getting a better feel for the car and a better feel for the track. So I may have been just improving overall. So I cant really say.

Like I mentioned above, I will have to bring the car to a shop who has race prepping experience. I won't personally be doing it myself, even if I wish I could. Your understanding and knowledge is excellent I can only hope the person I bring it too will be as well.

I will discuss all these points with the garage prior to doing it,

What I understand about rake is the more rake, the better turn in but slower track out from a "snappier" rear end. And the lower amount of rake will result in slower turn in but better track out. I know Im probably only scraping the tip of the iceberg about rake setup so correct anything I say if its wrong.

Thanks again for the input. As I understand so far from everyone is that for a DD/HPDE car, F/R % is not as important as the cross%. I am definitely aiming for a lighter car so I should be fine overall.

[L8 apexr]

For sure the crossweight is the most important for the prep level your at,changing the front to rear % involves relocating items to the rear or removing them from the front altogether.
In general terms the end that gets lightened will improve the grip with all else being the same,which isn't a bad thing for front engine rear drive car as long as the understeer can be tuned out by increasing front grip with alignment/roll resistance changes.
If the first time you drive the car and you find its understeering make sure to work on improving front grip-any monkey can make it balanced by reducing rear grip.Thats counter productive.

[gverelli]

For sure the crossweight is the most important for the prep level your at,changing the front to rear % involves relocating items to the rear or removing them from the front altogether.
In general terms the end that gets lightened will improve the grip with all else being the same,which isn't a bad thing for front engine rear drive car as long as the understeer can be tuned out by increasing front grip with alignment/roll resistance changes.
If the first time you drive the car and you find its understeering make sure to work on improving front grip-any monkey can make it balanced by reducing rear grip.Thats counter productive.

Thanks for the input. Your completely right in regards to my level of experience, it is not a race car and in terms of the body/chassis its completely stock. As for front grip, camber was at around -2.7 in the front toe set to 0, and not sure about caster numbers (m3 cab), and completely forgot the rear #'s. When I installed the coilovers I had the m3 drop-link installed to my 20mm eibach bar, which has 3 adjustments now on the stiffest setting. I am thinking about adding in a larger one, but until then this is what Im working with.

I never felt like I had understeer issues, turn in always felt good. Perhaps, the more experience I gain, the quicker I will be around the track resulting in increased understeer. But for now all seems okay.

When my HPDE season begins Ill see how it feels. However, before I had H&R Race/Billies, now the front rate has been bumped from 380 to 500 with adjustable konis, so I may have a bit more difficulty tuning it out. Compared to before I did not really have a choice because nothing was adjustable.

[L8 apexr]

Be careful with the bigger sway bar must be better school of thought,I've built somewhere around 10 race cars for myself over the years for differing types of events.One of the lessons learned from all those different cars and trying to make each as fast as possible is that big sways can start to hurt more than they help.
The E30 is too heavy and tall to go barless up front but I wouldn't go any bigger than whats in there now without exploring spring rate changes,stock rear bar is big enough.For autox it seems most fast guys remove the rear bar,for faster track work I'd leave the stock rear bar.
I suggest you drive the car for awhile to get used to the changes,then for fun soften the front bar and run it again.Maybe it'll be better maybe it won't but you'll never know if you don't try.
If you can have a friend take a head on shot of the car cornering at maximum,use that picture and a protractor to measure the body roll relative to the track surface.Between 2 and 3 degrees would be ideal,if its more(it likely will be with 500lb springs)then it needs to be firmed up to meet that target.If the tracks you run are smooth bias the roll stiffness towards the springs,if its rough than use the bar a little more than the spring.If you start lifting the inside front you either have too big a front bar or the rear is too soft(most likely cause).While lifting a wheel looks cool its slowing you down and isn't optimum-4 wheels on the ground makes more grip plain and simple.
Next too driving my favorite thing about cars is trying to make them go around a corner better.:)

[gverelli]

@L8 apexr ^^

Thanks for the info. Ya like I said buying a new front bar will be probably last on the list so Im stuck with what I have for now. I haven't run the car with the new suspension yet so I have absolutely no feedback in feel. I actually have no even driven in the street yet either because I did the suspension swap over the winter. Im going to run it as is for this summer (in relation to sways), 20mm front hardest setting and no rear bar. I had tracked with a 16mm bar and I didn't find it optimal at all, I found myself coasting through corners because the back end was WAY to tail happy. But I still haven't driven it without the rear one yet so I have no feedback yet.

I will try what you said with loosening the front bar just to experiment the feel of it. I wanted to get the car scaled before the first track day so should I experiment with the bar before or after the scaling? I also have to experiment with shock rebound because it is the first time I use konis, over my last billies..

[NigelStu]

Get the car corner-weighted/balanced first, then play with bar settings.


If you do it right, the bar should NOT have an impact on static cross weights (in most cases). If fact, set corner weights with bars off, then set the bars to no pre-load (with you in the car). I'm assuming you have adjustable end-links for the bars.


Sounds like with the susp changes, you have a bit to relearn with the car. Get yourself a base-line setting and run that until your lap times stabilize. Then start playing with damper/sway rake settings. Otherwise, you won't know for sure if a change was really good, or if you are just getting back into the groove.

[L8 apexr]

Exactly what NigelStu said,make sure the shop unbolts 1 end link when doing the crossweights and then sets the end link so it isn't preloading a corner.

Drive the car untill your comfortable with it before making changes,I suggest you start with tire temps-its the only way to know what is actually going on with the car dynamically.If you don't have one try and make friends with somebody that does,also make sure its a probe type as infareds are essentially useless for the info your after.
Once you optimize the tire pressure to the best you can for the alignment you start with then and only then should think about any changes,the temps will point you in the right direction-if unsure post up the temps and somebody will help no doubt.

Have fun above all else.;)