Spring rates and weight distribution

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graveltrap

graveltrap

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graveltrap
I've read somewhere that spring rates are related to weight distribution

I'm trying to sort out a look up table using excel to help me set up a chassis a little easier just wanted to run this past you guys to see if I'm making sense...........

Ok then

If a car has 50/50 weight distribution and you want an overall spring rate of say 12.5 you put 12.5 springs front and rear right??

if the car has a weight distribution of say 60%F/40%R and you want an overall rate of 12.5 kg/?? you would fit 15Kg/?? springs on the front and 10Kg/?? on the rear not a hundred percent sure if this is correct or not????? anyone help me out

what I'm doing is this to work out the rate for 60%

12.5*2/100*60=15

and for 40

12.5*2/100*40=10

does this make sense???

sorry for the question marks in spring rate value can't for the life of me remember the strange units GT uses.
 
I see what you're saying, but it may or may not work out the way you're calculating it. Obviously you need the stronger spring rate at the heavier end of the car in most cases, but not always The way you are saying it is logical but I'm not sure it yields any relevant engineering data.
 
I'd like to help,.. but am not a rocket scientist :lol:

What's the car doing that you dont like? When you say weight distibution,.. do you mean how to counter body-roll?
 
Im thinking he means nose weight versus tail weight, when whats really important is cross weight at each point in the turning radius.
 
The car may have a 50:50 weight distribrution but it may have a differnet handling characteristic. We all want oversteer at the limit. Sometimes we want our cars to be stable, more responsive, oversteer coming out of the turn...etc. It also depends on the drivetrain. In GT3, I like to set my rears always higher in FF, MR, AWD vehicles because there's more weight in the front, and I need the rear end to come out as much as possible.

My NSX I have the fronts and rear about the same...

my settings are up there at 15-18Kgs for go-kart handling.
 
Just looking to benchmark spring rates for different front rear weight distribution as a starting point for a neutral set up and making adjustments from there. I understand that there is not a magic formula for setting spring rates (Iwish there was) just looking to make it a bit easier for myself ;)

I did mean front / rear weight distribution as it is not possible to adjust spring rates side to side or even individually (maybe in GT4 hopefully along with tyre pressure)
 
Lets take that NSX as an example. my table shows those spring rates to be around 45 F / 55 R weight distribution. The NSX weight distribution is when looked up on the net 42 F / 58 R.
So in my mind the front of the example NSX 15 kg/mm F and 18Kg/mm rear means that the front is actually stiffer than the rear thus creating UNDERSTEER.

For a same overall stiffness the table makes the front SR 13.8kg/mm and the rear 19.00 Kg/mm (ouch)

try it and see what happens.........
 
I look at spring rates more at how they affect weight transfer. If the back end is searching for traction, then the rear springs are probably too stiff. If the car understeers, then the front springs are probably too stiff.
 
Well, if you wanna get into spring rate, you have to also add into it the effect

of bound and re-bound. All three of these adjustments are inter-twined with

each other. spring rates do effect your weight transfer. On a good FR car

I would normally have a standard setup of a quick tune with the rear stiffer

then the front by 2 to 3 points. With this I would have front and rear bound

and rebound set at all 8s or 9s. This will give you a general feeling of

the car and how it transfers weight and takes turns together. you want your

front end to dip its weight into the turn getting that rear end around. The

LSD is very effective, and perfect to fine tune your turning. At this point I suggest

going back to your replay. this is where it comes into play. You need to watch

your car and remember how it felt going hard into corners and taking those

high speed corners. If you have too much front end dip, you need to raise the

front spring rate. This in turn will screw up the up and down motion of the

car, thus the bound and rebound come into play. The perfect way to tell if the

bound or rebound is not properly adjusted to the spring rate is to watch it go

over a big rumble strip. A good track for that is Rome. If the car Jumps upward

after it hits the bump and sends the front side or rear side or both into the

air. Your Rebound is to high and needs to be adjusted properly. Vice-versa if

the car hits the strip and ducks into the bump and doesn't stabilize after

going back to normal height, ie dips again, then the bound is too low and needs

to be adjusted. I find that you need to tune these three compnents

together or you will screw up the whole weight distrubution of your car real fast.
 
as previously said I'm just looking for a good place to start from.

Take the NSX again but this time as it comes set up initially with full racing suspension. Front SR 11.7 rear SR 9.0 as the NSX has a weight distribution of 42/58 . The front rate is much stiffer relative to the rear rate (those settings would work on a car with 57/43FR weight distribution) creating understeer.

I think for the start of a neutral set up the rates should be 8.7 front and 11.9 rear this makes spring stiffness (relative front to rear) around the same.

This works for me. In a impromptu test (best of 3 flying laps at laguna seca ) with only the spring rates adjusted the NSX was 1 second a lap quicker with the rates set at 8.7F 11.9R than it was out of the box.

These rates are only a starting point for a set up. Every thing else then needs to be tweaked (including spring rates) to get the car to handle as the driver wants.

I think there is no point in setting up the dampers until you've found a spring rate because the dampers need to be tuned to the spring rate. As the springs are a big factor in how stiff the chassis is, they are my first port of call when attempting to set up suspension. Spring rate will also determine ride height etc etc.....
 
here, I believe that I used those settings for the spring rate as you did, but these are my old NSX type - r settings and they should in theory work with the other NSX honda manufactured.

sr - F - 6 - R - 7
rh - F - 102 - R - 102
b - F - 10 - R - 10
r - F - 7 - R - 7
ch - F - 2 - R - 2
t - F - -2 - R - 0
stabs - F - 7 - R - 7
brake - F 12 - R - 9
lsd - 5 / 5 / 5

they still needed tweaking when I was using them, but you never know they might just go perfect with the other nsx.
 
well my NXS has SR's front aand rear in the 15's Kgs. Because it's MR, the rears are being powered which induce more slippage and because the engine is back there with that weight thingy, the rear tires have more slip angle. I try to not harden teh rear springs because I still want traction, as in the drive tires to absorb bumps. haha

I think where ever the rates are that are given before you touch any setting, is were you should start. Because I tell you with my nephew driving my 'modified' car, he cannot react as fast to the cars responses because the car is too 'fast' for him, but with settings (springs rates included) that have not been touched, it's more controlable for him.
 
All interesting stuff :D

I must clarify that I'm not actually after settings for the Honda NSX and am intrested in spring rates in general and how to get them right for any car.......

As i've got some time off from work for the next couple of weeks :D I'm going to have a bash at this properly......

I think I'll have to try it out with FR, FF and MR cars. As the NSX has been used as an example I might as well stick with honda so it will be an ITR and an S2000 (V) found out that the ITR has front rear weight distribution of 62/38 and the S2000 is bang on 50/50 I guess I should use sim tyres as they exagerate the effect any changes made will have.

Haven't got the stock racing susp settings at the mo so I can't tell you what rates I'm going to try out first

Any one worked out a quick way to get camber and toe settings benchmarked???? :lol:
 
Found something else to add into the mix....tyre size. Found a web page with some tech details about what mugen recommend for using an S2000 on the track......7kg/mm front, 11kg/mm rear (standard rates for an S2000 3.9kg/mm front, 5.2 kg/mm rear). Mugen reccomend a much lower rate at the front because it carries narrower rubber than the rear (i guess to create more front end grip)

Had to try this out on my mugen S2000 and it works :)

Lap times fell by around half a second per lap when running these rates compared to a 50/50 set up of around 9kg/mm (I'd tweaked the chassis around a bit in line with mugens recommendations for ride height and toe and had a rough guess at the dampers.
 
I believe in Toe-in up front. Some bumpsteer will help you turn in. haha Toe out in the rear.. Camber will depend on how mucch the vehicle leans, more spring rate, less lean, less camber needed.
 
Haven't got round to having a go with the ITR as of yet.....as for setting up LSD's :confused:

Have been playing with the Mugen S2000 it's running 268bhp and is fitted with normal tyres

SR F 7.0 R 11.0
Ride height F 90 R 100
Damper Bound F 4 R 6
Damper rebound F6 R 8
Camber F 2.8 R 1.8
Toe F 0.0 R 0.5
Anti roll bar F 3 R 4

From what I remember off the top of my head. Dampers still need a bit of tweaking to match the spring rates...but on the whole the car handles pretty well.

Best lap round apricot hill 1'30.092
 
interesting grip setup, but it looks as if you have that S2000 to understeer at higher speeds. I would lose the rear toe and add a possible -.5 or -1.0 to the front. looks pretty solid. . . but loose in the front. It also looks to have a comforming ride to the road. It actually looks like a luxury car setting :lol:. Try working those bound and rebounds a little more on that car. :D
 
yep your right it does understeer a little...most notable around the long left hander abot mid way through apricot hill....on the other hand under brakes into turn two the back end is capable of a bit of oversteer...this car is yet to be fitted with a brake balance controller or LSD which is likley to sort those problems out.


The dampers are a little bit soft as you say but i'm sort of working on the theory that if youve got a maximum spring rate of 20kg/mm available the dampers would need to be set at 10 if your using springs rated at 10kg/mm then the dampers need to be set at 5. I do need to get them set up right so I plan to set bound and rebound to zero and work my way up the bound side until i've got something that feels right then play with the rebound in the same way. (Koni recommends this method for setting up it's adjustable shocks)

This whole S2000 setup is based around what Mugen recommends for the S2000 more info on this can be found at

http://www.kingmotorsports.com/mugen_tech_s2000.asp

and this does indicate that the car is set up to understeer a little.

Thanks for the feedback ;)
 
interesting enough, but up and down travel of a car will suffer time loss in the end. I personally like a really stiff setup. But that is tuned to my driving style too :D
 
Originally posted by FuJi K
...In GT3, I like to set my rears always higher in FF, MR, AWD vehicles because there's more weight in the front,...
Click to expand...

Does GT3 even model weight distribution this way? That may be a good place to start, in the end you should use whatever settings make you faster.
 
With the rears higher, there's more oversteer at the limit which makes the car handle better. Oversteer is needed in GT3 because it's all track racing...and some rally.
 
Oversteer is fun but it does not make you faster on the track....the best way to go quickly is to get the car set up to be neutral (lose's grip at the front and rear at the same time). As for the way that GT3 models weight distribution only the guys who wrote the software know and it is up to us to find out ;)
 
I like your theories on setting up SR for each car. I'd like to know how you're finding these real life settings for spring rates, though. Also, if and when you do finish your search for the best starting points, will you be comparing these to actual settings of every tested car out there? (Did that make sense? :confused: )

I also thought that ride height played a big role in weight distribution, aside from spring rates. I may have missed it, but are you leaving this at "stock" settings until you figure everything else out? I mean, a rear-heavy car might be able to become 50/50 once ride heights are adjusted. You get what I'm saying? Please correct me if I'm wrong.
 
I just came across the spring rates for the S2000 on another site, and thought I'd tru them out haven't found any other RL rates as of yet.

I'm not 100 percent sure that ride height can have as bigger impact as you suggest........I tend to have the rear of the car between 10 to 15mm higher than the front.

Conversion fom metric to imperial...is this right

7.0 kg/mm = (7 x 2.22)x25.4 = 394.72 lbs/in

(2.22lbs= 1kg) (25.4mm = 1 inch)
 
I just came across the spring rates for the S2000 on another site, and thought I'd tru them out haven't found any other RL rates as of yet.

I'm not 100 percent sure that ride height can have as bigger impact as you suggest........I tend to have the rear of the car between 10 to 15mm higher than the front.

Conversion fom metric to imperial...is this right

7.0 kg/mm = (7 x 2.22)x25.4 = 394.72 lbs/in

(2.22lbs= 1kg) (25.4mm = 1 inch)
 

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