Springs !!

Re: Springs !! (Tree)

Mon, 24 Feb 2014 00:44:11 GMT

DOH!! I forgot to attach the article!:http://consummatedriver.blogspot.com.au/2012/02/how-to-choose-spring-rates.html
Just a few extra tid bits to add to Ian's great post

TwoDogs
Thanks Tree,
the wild fluctuation in those figures seems to illustrate that any spring rate will do, which surely can't be right. I presume that other factors come into play such as sway bars ? (I would hate to think people were winding up compression and rebound damping to restrict the suspension travel).

Reason for range of spring rates: There are 2 types of springs, progressive and linear. Progressive, as the name suggests is designed so that under suspension travel the rates increase the more force is applied between two spring rates. This is designed so that the car is compliant on the street and are really made for comfort. Therefore 99% of stock springs are progressive.
You can tell if the springs are progressive because there will be coils bunched up on one end of the spring.
Linear springs have only one fixed rate so they will feel exactly the same. This makes the car much more predictable when there are more G's involved as you guessed. Thus all coilover springs are linear. However since it is a fixed rate, a car setup on the track will be a bone-jarring nightmare on the road. The MR2 is one of those few cars which have linear stock springs albeit it is far from track spec, I believe this is why even the stock MR2 is stiffer than say a stock Silvia.
Unfortunately however, and this ****s me to tears, ALL aftermarket springs for the SW20 are progressive.
The table lists only spring rates for the springs so don't worry about sway bars.

About the table of figures.... a few questions..
1) What is frequency ? and what importance does it have ?
Check the link to the article above, it will explain much better than me

3) Under the Rate column is a number eg 130, what is that? I can see it relates to the adjacent column which looks like Kg/mm ?

Yeh it's the corresponding metric conversion. I originally took this table from MR2oc.com so it was all in pounds, I added the kg/mm b/c was just easier for me to deal with and I was lazy to label before uploading it so my bad (it was 2am haha). I also added the softer rates for RSR Race springs. S Tech, RSR Downs and TRD springs I don't have other rates yet.
4) Pro-Kit and Swift offer lighter than stock springs ! some other unusual purpose for an MR2 ?

Linear vs prog as you now know after reading above. Yes, some people with Eibach Pro kit + Koni yellows (softest setting) reckon it is even more compliant than stock setup!
Ok now back to sorting out my (mis)understandings...
If swaybars do increase/decrease the travel of the shock/car, I imagine it would not be linearly ?? If so, then the combined "spring rate", if it can be thought of this way, would be nonlinear.
This may of course be desirable, I don't now, but should probably be considered.
(Please correct me if I should not be looking at it this way.)

Yes you are correct the sway bars do not have linear spring rate because they are usually basically torsion bars so the spring rate increases proportionally to the amount of force is my understanding. So yeh the combined spring rate is non-linear with the addition of sways. Another reason why some people with this school of thought ditch it I suppose. The attractiveness of the sway bar is the fact that it can reduce body roll similar to the function of springs but minimise impact on the ride comfort.

Back to the table of spring rates and the huge range in approaches...... to me, there must be an optimal setting for cornering, brake and acceleration loadings and bump management for both grip and comfort. Clearly the road has bigger bumps, less speed and passengers, compared to the track, so all the numbers change. (not to mention tyre grip, another variable).

You can definitely work out the best compromise for a street only car, it would be so much easier instead of having double duties of road and track. Dampers are actually largely responsible for ride quality. So even if you have relatively higher spring rates, a good shock i.e Koni, Bilstein, Penske will still be compliant, up to a point.

The table does seem to illustrate that the track springs are firmer. I see a huge variation in the % change to back v front ratings over the stock Toyota settings. Clearly a philosophical difference addressing different problems (eg control of the car under brakes v max sideways grip under acceleration perhaps ??).
So here is more I don't understand how the front and back interact. I did read here on the forum, one member wrote that extra body roll from removing the rear bar, transfers via torsion through the body of the car to take weight of the inside front, for an increase in understeer. This seems to be an important point and why a rear bar would be advisable even on a race car.
(Again pls correct me ).

Again, it's the driving style that determines spring rate. I chose RSR Race because I wanted highest aftermarket rates that was most "oversteery" as I have a bad habit of braking too late without trail braking so I tend to understeer the car on corner entry. Probably cheaper to adopt a different driving style heh. Springs will have the most effect on oversteer/understeer.
I'm not a techy so I don't know about front vs rear interaction; just that removing the rear = more understeer due to more rear grip as you say and vice versa

http://www.mr2australia.c...=22685&whichpage=1
Check out this thread for the "no sway bar" school of thought. Mr zerogk is the one who introduced me so this (which I initially did not endorse). I'm sure he'll be happy to answer the more complex q's which I am too dumb to understand haha. Just shoot him a PM and if he doesn't reply let me know to kick his arse.

New question - a lot of questions I now, sorry about that,
5) Once I have the spring rates "right" (clearly there is no right) then how does one work out (or feel when driving), the difference between the front bar and the rear bar ? I presume if there is too much roll, then stiffening the rear bar (ie the heavy end) is the starting point, but how much of the increased stiffening/correction is put into the front bar ? Again if I am looking at these things the wrong way someone pls correct me).

Questions is what keeps forums alive! From your first post it sounds like you need to stiffen the rear. Ultimately I think it will come down to trial and error. There's only so much theory you can do, but without trying out the settings for yourself that theory is abeyant. With adjustable sway bars ofc. Here's some basic guides on suspension settings:

http://www.execstudio.com/tech_suspension_over-understeer.htm
http://www.sccawiregrass.org/suspension.html
There is a little book by Carroll Smith called Engineer in your Pocket which I have been meaning to get; very handy for track goers. Probably overkill for you just like all your questions haha but I admire your eager for knowledge/research

Re: Springs !! (Reddtarga)

Sun, 23 Feb 2014 18:06:56 GMT

"1) What is frequency ? and what importance does it have ?"
Here's one description if you like equations:
http://hyperphysics.phy-astr.gsu.edu/hbase/shm2.html

"2) What is "Drop" ? a shorter spring?"
Drop refers to how much the car is lowered from stock.
If you can find one that hasn't been already modified, on a '92+ SW20 the stock ride height will be about 340mm measured from the centre of the wheel to the underneath of the fender arch, both F&R. Turbo models also seem to run a bit lower at the rear.
On earlier models ride height is a bit higher.

"3) Under the Rate column is a number eg 130, what is that? I can see it relates to the adjacent column which looks like Kg/mm ?"
Spring Rate is the change in load per unit deflection in pounds per inch (lb. /in.) or Newtons per millimeter (N/mm).

"4) Pro-Kit and Swift offer lighter than stock springs !"
I don't know about Swift springs, but Eibach Prokit springs are actually about 2 kg per spring heavier than the stock ones. I have found that these give about the same ride height as the stock '92+ cars but ride harder. However many people seem to like them, especially if combined with Koni adjustable inserts.

"5) Once I have the spring rates "right" (clearly there is no right) then how does one work out (or feel when driving), the difference between the front bar and the rear bar ? I presume if there is too much roll, then stiffening the rear bar (ie the heavy end) is the starting point, but how much of the increased stiffening/correction is put into the front bar ?"
On my own car in practice I found fitting a stiffer rear ARB compared to the front made my car unstable with poor tracking. On the other hand fitting a stiffer bar on the front improved turn in. A bit more neg camber and caster than stock also helped understeer.

Re: Springs !! (TwoDogs)

Sun, 23 Feb 2014 10:27:40 GMT

Thanks Tree,
the wild fluctuation in those figures seems to illustrate that any spring rate will do, which surely can't be right. I presume that other factors come into play such as sway bars ? (I would hate to think people were winding up compression and rebound damping to restrict the suspension travel).

About the table of figures.... a few questions..
1) What is frequency ? and what importance does it have ?
2) What is "Drop" ? a shorter spring?
3) Under the Rate column is a number eg 130, what is that? I can see it relates to the adjacent column which looks like Kg/mm ?
4) Pro-Kit and Swift offer lighter than stock springs ! some other unusual purpose for an MR2 ?

Ok now back to sorting out my (mis)understandings...
If swaybars do increase/decrease the travel of the shock/car, I imagine it would not be linearly ?? If so, then the combined "spring rate", if it can be thought of this way, would be nonlinear.
This may of course be desirable, I don't now, but should probably be considered.
(Please correct me if I should not be looking at it this way.)

Back to the table of spring rates and the huge range in approaches...... to me, there must be an optimal setting for cornering, brake and acceleration loadings and bump management for both grip and comfort. Clearly the road has bigger bumps, less speed and passengers, compared to the track, so all the numbers change. (not to mention tyre grip, another variable).

The table does seem to illustrate that the track springs are firmer. I see a huge variation in the % change to back v front ratings over the stock Toyota settings. Clearly a philosophical difference addressing different problems (eg control of the car under brakes v max sideways grip under acceleration perhaps ??).
So here is more I don't understand how the front and back interact. I did read here on the forum, one member wrote that extra body roll from removing the rear bar, transfers via torsion through the body of the car to take weight of the inside front, for an increase in understeer. This seems to be an important point and why a rear bar would be advisable even on a race car.
(Again pls correct me ).

New question - a lot of questions I now, sorry about that,
5) Once I have the spring rates "right" (clearly there is no right) then how does one work out (or feel when driving), the difference between the front bar and the rear bar ? I presume if there is too much roll, then stiffening the rear bar (ie the heavy end) is the starting point, but how much of the increased stiffening/correction is put into the front bar ? Again if I am looking at these things the wrong way someone pls correct me).

that will do for now - coffee calling.
Cheers Tree et al.

Re: Springs !! (Tree)

Sun, 23 Feb 2014 02:38:33 GMT

Hey TD,
This attachment for various spring rates might assist you in searching for your springs. For the street, most folks seem happy with Eibach Pro Kit or TRD springs or even the late model stock springs as Red has mentioned earlier.
This article seems to be a great well of knowledge to choose rates, maybe a little too technical for non-track enthusiasts however you strike me as a guy who seeks genuine answers (as you mentioned).
My understanding is that stiff springs + no sway bar = ultimate traction due to individual wheel independence but sacrifice comfort vs
Mild springs + heavy sways = decent handling and minimised comfort loss. This is might you.
This is probably an over-simplification but I am a simple guy lol

Re: Springs !! (TwoDogs)

Sat, 22 Feb 2014 23:03:44 GMT

Hi Rt, I must admit that the thought of using stock Japanese ratings comes as a bit of a shock (no pun intended). I've been into motorbikes for 40 years more than cars, and 1st thing you needed to know is that you are a 60kg rider. The springs needed to be changed. So if you are saying that stock Toyota springs are close to the mark, then I will rethink my whole strategy.....

Re: Springs !! (Reddtarga)

Fri, 21 Feb 2014 17:13:19 GMT

"I'm hoping someone can advise what spring rate(s) to use, front and back for use as a road car"

For a low budget fix why not get some used stock springs. They should be easy to find and although they may have sagged a bit they don't wear out.
I would recommend some off a post '92 model car since they are slightly lower than the earlier models.
With these if you needed to replace shocks you could also use the cheaper inserts, assuming that you have the gland nut type struts. (That will depend on the year/model of your car).

Keep in mind that any springs that lower the car more than one inch from stock will need expensive heavy duty shocks if they are to last.

Re: Springs !! (TwoDogs)

Fri, 21 Feb 2014 11:13:26 GMT

Thanks Rt for responding. I have done a little bit more googling and now understand that the relationship between springs and sway bars is quite complex. People seem to have success using different approaches, such as no rear sway at all ! Everything impacts everything else. Roll, grip, harshness.
So my question is clearly not specific enough.
I have the feeling that when the spring rates are right then the sway should be less stiff and that many soft springs are "solved" by a stiff swaybar but is a poor, compromised solution. But now I recognise that my "feelings" may be totally wrong.
More reading, I think.
The other problem is that people have their opinion, based on varying amounts of experience and while since it is simple to improve some old worn out springs and shocks via just about any method, people become convinced that "this is the way to do it". So sorting through those opinions to find the genuine suspension experts, is not easy.

Re: Springs !! (Reddtarga)

Fri, 21 Feb 2014 10:36:06 GMT

"I suspect that suspension-wise, it has not been done optimally".

Can you be more specific?
Excessive lowering generally means hard ride and bad handling, especially if the shocks are shot.

Springs !! (TwoDogs)

Fri, 21 Feb 2014 01:31:17 GMT

I have recently acquired an SW20 as a project car for my son and I to work on. Initially, I would like to sort the suspension, working to a shoestring budget. The car has been lowered, not sure how this was done, and while I don't mind the concept of a lower cog, I suspect that suspension-wise, it has not been done optimally.
I can decide on ride-height later, but for now, not wanting re-invent the wheel, I'm hoping someone can advise what spring rate(s) to use, front and back for use as a road car, not track.
The car weighs the standard amount, and my weight is a svelt 85kg.
Currently the front suspension responds reasonably well to being pushed down and released. The back gives a much more sluggish rebound.
I am really hoping that someone has 2 MR2s, one for road and one for track, and can advise what springs they settled on. cheers
Nigel