Agggh! The endless track coilover and spring rate debate!! Help!

[Toastfrenzy]

I'm going for AST 5100 with "track" set-up, so 80N/mm (456lb/in) front and 90N/mm (513lb/in) rear. I'll let you know what that's like on the road.. probably "FIRM".

I have this set up, and you won't have any fillings left in (if you have any) after taking it out on the streets......I wouldn't use this for a daily etc.

 

[EVOgone]

Cup racer rears are only 400 why this obsession with overly stiff rearbend? On my track car its on bilsteins 70/45 n/m springs and it's perfect for road track etc.

 

[Steven103]

I would've thought you'd know the answer to that one.

Are your Bilstein rears a coilover? If not then the motion ratio of the spring position on the rear beam straight away makes the rear more like a 90 N/mm coilover (a bit over 500 lb).


The endless quest to better control the front contact patch for as little money as possible results in really high front spring rates. The roll stiffness ratio (front to rear) needs to remain sensible hence the rears rise too.

The rear spring rates are indeed ridiculous but it's how you make a FWD car quick around a track for the least money and least complexity. Just as an idea 450/500 lb springs with a 130 kg rear corner weight gives a rear ride frequency of about 4.5 Hz. Road cars are typically quoted as 1 Hz, the baby Le Man GTE cars are around 3 Hz and F1/Indycars are quoted around 5 Hz. That gives an idea of how mentally stiff a 500 lb rear spring makes a Clio feel. But it's worth it to make the front better.

To be brutally blunt there are very very very few people on this forum who actually understand why they have built their track/race cars the way they have. Most just pick up buzzwords and typical settings for this size/weight/style of car that are known to work. Not for one second am I saying this in a bad way - you don't have to know exactly how a TV works in every single detail to enjoy watching it!


edit: attempt two.

 

[CamMoreRon]

I assume by correcting you mean raising.. if so, then it will increase load transfer.

Higher roll centre increases Non-Rolling Overturning Moment due to the longer effective lever arm between the point at which the geometric forces act and the ground. It reduces Rolling Overturning Moment by decreasing the height difference between roll axis and CoG, which does act to reduce load transfer, but it comes out as a net increase, unfortunately.

 

[CamMoreRon]

Steven - good posts!

I think those who have the knowledge are able to cherry-pick the bits we know are going to make a difference and leave out the unnecessary stuff, resulting in optimum bang for buck.

I have too deep a money pit in my 205 as it is.. shouldn't have bought those AST's really, but I know it'll be night and day on track compared to the Eibach kit the car came with.

 

[EVOgone]

I would've thought you'd know the answer to that one.

Are your Bilstein rears a coilover? If not then the motion ratio of the spring position on the rear beam straight away makes the rear more like a 90 N/mm coilover (a bit over 500 lb).


The endless quest to better control the front contact patch for as little money as possible results in really high front spring rates. The roll stiffness ratio (front to rear) needs to remain sensible hence the rears rise too.

The rear spring rates are indeed ridiculous but it's how you make a FWD car quick around a track for the least money and least complexity. Just as an idea 450/500 lb springs with a 130 kg rear corner weight gives a rear ride frequency of about 4.5 Hz. Road cars are typically quoted as 1 Hz, the baby Le Man GTE cars are around 3 Hz and F1/Indycars are quoted around 5 Hz. That gives an idea of how mentally stiff a 500 lb rear spring makes a Clio feel. But it's worth it to make the front better.

To be brutally blunt there are very very very few people on this forum who actually understand why they have built their track/race cars the way they have. Most just pick up buzzwords and typical settings for this size/weight/style of car that are known to work. Not for one second am I saying this in a bad way - you don't have to know exactly how a TV works in every single detail to enjoy watching it!


edit: attempt two.

Spoke go the Reiger and Ohlins about this when I got the suspension for the rallycars and they advised its not the way to go. If you look at manufacturers proper developed competition cars they haven't gone that route. Renault for example on the cup racers even the current one and all the rally clios inc S1600 don't share that view with over still rear. Alls I know is that it works and is proven. My track car was quicker than chase racing car and could carry as much corner speed for example.

 

[bozothenutter]

Great thread!
I tend to listen to people with more experience than me...its a great shortcut to knowledge, especially if they know how to explain the 'why'

 

[Steven103]

Spoke go the Reiger and Ohlins about this when I got the suspension for the rallycars and they advised its not the way to go. If you look at manufacturers proper developed competition cars they haven't gone that route. Renault for example on the cup racers even the current one and all the rally clios inc S1600 don't share that view with over still rear. Alls I know is that it works and is proven. My track car was quicker than chase racing car and could carry as much corner speed for example.

Good bunch of questions, but I do believe there are answers to each that fit with the overall picture. I wrote a massive reply and decided no-one would care so wrote a short version:

* Rally cars are entirely different. On a circuit absorbing bumps is one of the lowest priorities hence you can get away with overly stiff springs. On a rally car absorbing bumps is one of the highest priorities.
* S1600 and cup racer are both customer cars. They genuinely are not designed to be as fast as possible. They're designed to be easy and predictable to drive so that private teams wlll buy lots of them. They're also better developed and are full of better-ways-to-go-fast-than-overly-stiff-springs (I mean come on, the S1600... it's really not very similar to my 182 at all in terms of size weight track width weight distribution suspension geometry etc.). Also regarding the S1600, I've no idea how much they cost but I bet you could buy at least one 172 track car for the price of a set of S1600 dampers.
* Soft springs ARE better for tyre grip (an alarmingly unknown fact) and Ohlins, RS and other racing car designers know this.
* There are much better ways to maintain a good camber angle during corners than rock hard springs but people who build clio track cars either don't know this, don't have the money or don't have the will.
* For a cheap simple track Clio it's more important to manage the camber angle in corners. So rock hard suspension to keep a good camber angle outweighs the grip benefit of softer springs when you build the car cheaply and easily.

As for your track car being faster than the chase racing car... I believe you (I've watched one of their onboards with you infront I believe) but given that there are 4000 differences between each car on that specific day (however similar they may look) you can't attribute that to one of those differences.



Bozo, this "ride frequency" thing I was on about explains Tony's 400 vs 450 comment quite well IMO.

Imagine a really hard spring on a clio. Now put the same spring on a bus. The same spring rate now feels really soft. Hence spring rate isn't actually a very good measure of how hard a SUSPENSION is. It's fine for measuring how hard a SPRING is though. So "ride frequency" is used to describe how "hard" the whole suspension feels because it takes into account mass, different suspension geometries etc. so it's great for comparing between cars. Remember Tony saying that 400lb vs 450lb wouldn't be a big difference even though it's nearly 15%? It's because of this ride frequency thing. I don't know if this will mean anything to you, but in the equation for ride frequency you "square root" the spring stiffness. This means that the impact of the change is "reduced."

e.g. square root of 16 is 4.

Square root of 4 (which is 4 times smaller than 16) is only 2 (which is only half as small)

That is why what sounds like a decent change in spring rate only makes a relatively small difference to how hard the suspension FEELS. (It's not quite as simple as just square rooting the spring stiffness, there's other stuff in the equation too, but the square root bit is the bit that explains why 450 vs 400 is only a small difference even though the number sounds quite big)

A consequence of this whole square root thing is that a Clio on a 400lb spring does not "feel" exactly twice as stiff as a Clio on a 200lb spring! The other great thing about using "ride frequency" is that a ride frequency of 2 does feel exactly twice as stiff as a ride frequency of 1.

 

[Ph1 Tom]

My setup is now AST sportline 1s with 400lb front and 285lb rear. Can't fault it on the road. I had cooksport springs before and the ASTs are another level. Good ride which is firm but not crashy but a very noticeable reduction in roll. I need to get it on track and see how much better it is.

If you went any stiffer I feel it would be slightly compromised on the road but you see some benefits on track I'm sure.

 

[CamMoreRon]

Verdict on the AST's, as predicted, is FIRM.

Buttery smooth, but firm.

 

[bozothenutter]

Good bunch of questions, but I do believe there are answers to each that fit with the overall picture. I wrote a massive reply and decided no-one would care so wrote a short version:

* Rally cars are entirely different. On a circuit absorbing bumps is one of the lowest priorities hence you can get away with overly stiff springs. On a rally car absorbing bumps is one of the highest priorities.
* S1600 and cup racer are both customer cars. They genuinely are not designed to be as fast as possible. They're designed to be easy and predictable to drive so that private teams wlll buy lots of them. They're also better developed and are full of better-ways-to-go-fast-than-overly-stiff-springs (I mean come on, the S1600... it's really not very similar to my 182 at all in terms of size weight track width weight distribution suspension geometry etc.). Also regarding the S1600, I've no idea how much they cost but I bet you could buy at least one 172 track car for the price of a set of S1600 dampers.
* Soft springs ARE better for tyre grip (an alarmingly unknown fact) and Ohlins, RS and other racing car designers know this.
* There are much better ways to maintain a good camber angle during corners than rock hard springs but people who build clio track cars either don't know this, don't have the money or don't have the will.
* For a cheap simple track Clio it's more important to manage the camber angle in corners. So rock hard suspension to keep a good camber angle outweighs the grip benefit of softer springs when you build the car cheaply and easily.

As for your track car being faster than the chase racing car... I believe you (I've watched one of their onboards with you infront I believe) but given that there are 4000 differences between each car on that specific day (however similar they may look) you can't attribute that to one of those differences.



Bozo, this "ride frequency" thing I was on about explains Tony's 400 vs 450 comment quite well IMO.

Imagine a really hard spring on a clio. Now put the same spring on a bus. The same spring rate now feels really soft. Hence spring rate isn't actually a very good measure of how hard a SUSPENSION is. It's fine for measuring how hard a SPRING is though. So "ride frequency" is used to describe how "hard" the whole suspension feels because it takes into account mass, different suspension geometries etc. so it's great for comparing between cars. Remember Tony saying that 400lb vs 450lb wouldn't be a big difference even though it's nearly 15%? It's because of this ride frequency thing. I don't know if this will mean anything to you, but in the equation for ride frequency you "square root" the spring stiffness. This means that the impact of the change is "reduced."

e.g. square root of 16 is 4.

Square root of 4 (which is 4 times smaller than 16) is only 2 (which is only half as small)

That is why what sounds like a decent change in spring rate only makes a relatively small difference to how hard the suspension FEELS. (It's not quite as simple as just square rooting the spring stiffness, there's other stuff in the equation too, but the square root bit is the bit that explains why 450 vs 400 is only a small difference even though the number sounds quite big)

A consequence of this whole square root thing is that a Clio on a 400lb spring does not "feel" exactly twice as stiff as a Clio on a 200lb spring! The other great thing about using "ride frequency" is that a ride frequency of 2 does feel exactly twice as stiff as a ride frequency of 1.

pm me the massive one then...i'm a patient padawan.
thanks for explaining btw.....now must get back to my Staniforth and Puhn.
then I have to start making 50%more money to test all of it out!

 

[sonny172cup]

Copy and pasted from the K Tec website which is where my Spax kit came from

http://www.k-tecracing.com/show_product.asp?id=4510

Front 342lbs
Rear 228lbs

New rear units delivered to me this week

. by Ricard o1, on Flickr

I have the Spax RSX set up with this new style rear struts, note that these, dont use helper springs and have 3 lowering shims...on mine I binned the lower shims and used shorter springs (9'') to retain the helper. I am using 400lb rears with this kit and the 342lb fronts. which is too soft, but im in the trial and development phases of racing at the moment, to see what works for my driving style.

I think a good start would be 400lb all round, maybe then uprating to 450s all round, then when you get a feel for the car, adjust, i.e stiffen up the rear to suit driving style.

Note that the spring rates suggested are for the Spax coilovers.

p.s the new rear struts are leaps and bounds ahead of the old units. Note, that these cannot be re-valved (unlike the fronts) as they are a sealed unit.

 

[rdoxenham]

I have the Spax RSX set up with this new style rear struts, note that these, dont use helper springs and have 3 lowering shims...on mine I binned the lower shims and used shorter springs (9'') to retain the helper. I am using 400lb rears with this kit and the 342lb fronts. which is too soft, but im in the trial and development phases of racing at the moment, to see what works for my driving style.

I think a good start would be 400lb all round, maybe then uprating to 450s all round, then when you get a feel for the car, adjust, i.e stiffen up the rear to suit driving style.

Note that the spring rates suggested are for the Spax coilovers.

p.s the new rear struts are leaps and bounds ahead of the old units. Note, that these cannot be re-valved (unlike the fronts) as they are a sealed unit.

Where did you get the springs from? Spax direct? Thx

 

[sonny172cup]

Any 1.9'' spring will work, the standard Spax springs are way to long imo they hinder the ability to lower the rear of the car to an ideal level. I got the rear springs from Mark Fish which I think is the Faulkner items.

 

[Ricardos]

Any 1.9'' spring will work, the standard Spax springs are way to long imo they hinder the ability to lower the rear of the car to an ideal level. I got the rear springs from Mark Fish which I think is the Faulkner items.

I have the 11" Spax springs and will order the 275lbs Faulkner springs, do you think i should stay with the same length? I only ask as you've mentioned the 9". How mine sat with the 11" seemed ok ( approx 20mm higher than arch line) but would like the option of lowering the ride height a bit, will the 11" be ok to do that? I didn't want to compromise the components.

 

[sonny172cup]

Might as well drop to 10" or 9", you can still adjust the height of the collar to original height. I found that the rears could not go low enough, and btw im no stance queen, the car is used for racing and isn't actually that low in terms of whats on here.

This is my set up (minus the height spacers).

 

[-D4N-]

I have the Spax RSX set up with this new style rear struts, note that these, dont use helper springs and have 3 lowering shims...on mine I binned the lower shims and used shorter springs (9'') to retain the helper. I am using 400lb rears with this kit and the 342lb fronts. which is too soft, but im in the trial and development phases of racing at the moment, to see what works for my driving style.

I think a good start would be 400lb all round, maybe then uprating to 450s all round, then when you get a feel for the car, adjust, i.e stiffen up the rear to suit driving style.

Note that the spring rates suggested are for the Spax coilovers.

p.s the new rear struts are leaps and bounds ahead of the old units. Note, that these cannot be re-valved (unlike the fronts) as they are a sealed unit.

Newer style rear struts?? What's the difference between yours and the other rear struts, I bought my kit last year so I'm guessing that there the older style ones. What's the advantage with the helper spring on the rear, I have them on the front just not on the rear?

Daniel

 

[sonny172cup]

The new struts ( i say new they may have come out last year) have a slightly thicker piston, dust cover, larger rubber mounts and the shims. The Spax tech when I spoke to him said they are also valved go up to a next spring rate, these are very similar to the Spax race rears that are controlled for the 750mc club (on ktec website). Helper spring is to stop main spring rattling when uncompressed.

I purchased my Spax in 2012 and the rears was pathetic in comparison.

 

[Ricardos]

My 1st set of RSX rear coilovers were purchased in Feb 2013 and didn't have helper springs only the 225lbs 11" items. They lasted about 11k and less than a year so Spax sent me a pair of new dampers under their 2 year warranty.

I think i'll go 275lbs and 10" as it's primarily a road car (182 FF not stripped out) driven hard with the occasional trackday

 

[sonny172cup]

Interesting. Yea sounds good, new springs from Merlin motorsport are cheap enough anyway to play about with.

 

[bozothenutter]

Isn't the B14 75 mm at the front?
So matching that would be a start.
Any idea's what the rears are?

 

[ripp]

Hi there,
After about three years two of my GAZ shocks (GHA kit) started to leak. I'm undecided wether to go for bilstein b14 or refurb the GAZ units as I'm quite tight on a budget right now.
I know that billies have a very good reputation but also heard of them being problematic after couple of thousand miles.
But the biggest issue is regarding how soft or hard they really are. The GAZ being adjustable I managed to set them up close to the way I like them (the shocks are set to about 30-40% of their maximum stifness).
GAZ are 275lbs/in front and 250lbs/in rear. Bilstein are said to be quite soft (I really don't want them to feel softer than my current setup) but they are said to be 70nm/mm front which is about 400 lbs/in, so that means their springs are actually harder than the GAZ ones?
If I'm not missing anything and they are a bit stiffer than my current setup than I'll be quite pleased with that.
The car is not stripped, and I have some rubbing issues on the front, it's not even that low (As I've seen lots on here0 and that's why I don't want anything softer than my current setup.
Cheers!

 

[ripp]

c'mon.. I'm sure there are people here who went from gaz to billies and could give some feedback

 

[NorthloopCup]

Hi there,
After about three years two of my GAZ shocks (GHA kit) started to leak. I'm undecided wether to go for bilstein b14 or refurb the GAZ units as I'm quite tight on a budget right now.
I know that billies have a very good reputation but also heard of them being problematic after couple of thousand miles.
But the biggest issue is regarding how soft or hard they really are. The GAZ being adjustable I managed to set them up close to the way I like them (the shocks are set to about 30-40% of their maximum stifness).
GAZ are 275lbs/in front and 250lbs/in rear. Bilstein are said to be quite soft (I really don't want them to feel softer than my current setup) but they are said to be 70nm/mm front which is about 400 lbs/in, so that means their springs are actually harder than the GAZ ones?
If I'm not missing anything and they are a bit stiffer than my current setup than I'll be quite pleased with that.
The car is not stripped, and I have some rubbing issues on the front, it's not even that low (As I've seen lots on here0 and that's why I don't want anything softer than my current setup.
Cheers!

If your on a tight budget and your gaz took 3 years to leak I'd just get them refurbed mate personally. If you liked the way it drove on them as well, you at least know what your getting.

 

[ripp]

Makes sense what you're sayin' but on the other hand my experience with coilovers is very limited. I never drove another clio running other coilies to compare with mine. Yeah i'm on a tight budget but if the b14's are indeed in another league of handling then maybe it's better to wait a little and do an upgrade.

 

[NorthloopCup]

Makes sense what you're sayin' but on the other hand my experience with coilovers is very limited. I never drove another clio running other coilies to compare with mine. Yeah i'm on a tight budget but if the b14's are indeed in another league of handling then maybe it's better to wait a little and do an upgrade.

I personally would say the bilsteins are in a different league compared to the gaz stuff. Their only downside is that they're not damping adjustable.
What spring rates are your gaz currently running on?

 

[ripp]

the GAZ are 275 lbs front and 250 lbs/in rear. I found that the bilstein kit is 90nm (front springs) which if I'm not mistakin' is about 400lbs/in.
Yes they're not adjustable but I'm pretty sure that the damping is well suited from the factory. I'm basically running my dampers in the same setting since I've got them so not really keen to have adjustable damping, I could live without it even if that's one of the reasons that I went with gaz initially

 

[NorthloopCup]

the GAZ are 275 lbs front and 250 lbs/in rear. I found that the bilstein kit is 90nm (front springs) which if I'm not mistakin' is about 400lbs/in.
Yes they're not adjustable but I'm pretty sure that the damping is well suited from the factory. I'm basically running my dampers in the same setting since I've got them so not really keen to have adjustable damping, I could live without it even if that's one of the reasons that I went with gaz initially

The rates of the gaz are quite low compared to the bilsteins then. I'd be saving up and opting for the billies personally.

 

[British_Tommy]

Sorry to revive this thread...

I've just had a good chat with Julian at Balance Motorsport, in conjunction with AST.

I'm buying coilovers for my 197 track project, and couldn't figure out why a lot of you opt for heavier springs at the front and lighter at the back. Surely this just induces understeer? Especially with some of the mentally heavy springs you guys are quoting?

I've gone for 450 front / 500 rear, which is a good balance in my opinion, unless you are a pro driver who wants to drive the worlds twitchiest car...

Call me a cynic but why do you guys insist on heavy front springs?

 

[DrHammershaft]

Sorry to revive this thread...

I've just had a good chat with Julian at Balance Motorsport, in conjunction with AST.

I'm buying coilovers for my 197 track project, and couldn't figure out why a lot of you opt for heavier springs at the front and lighter at the back. Surely this just induces understeer? Especially with some of the mentally heavy springs you guys are quoting?

I've gone for 450 front / 500 rear, which is a good balance in my opinion, unless you are a pro driver who wants to drive the worlds twitchiest car...

Call me a cynic but why do you guys insist on heavy front springs?

Is it AST you are going for? If not which are you after?

Not sure which dampers I'm going for with my 182 but I'll be trying 500 front and 550 rear to see how I get on.

 

[British_Tommy]

@DrHammershaft yep AST 5100 with top mounts. I've not decided yet but leaning toward 450 front 500 back... Any reason you're going harder? Julian has offered to calculate optimal spring rates for me but I'd need to disassemble the strut to get the measurements for him, which I'm not really inclined to do so was looking for advise on here... Seems to be a bit open still!!

 

[DrHammershaft]

I'm not clued up on 197s but the reason for going so hard on the rear is a sort of average of the advice I've been given. Some say 475 rear, some say 625 rear. I want to try 500 on the front so wanted a little more on rear for better turn in. I'm new to the track coilover game so thinking about buying some extra springs and seeing how I go from there

 

[Sonic Boom]

Sorry to revive this thread...

I've just had a good chat with Julian at Balance Motorsport, in conjunction with AST.

I'm buying coilovers for my 197 track project, and couldn't figure out why a lot of you opt for heavier springs at the front and lighter at the back. Surely this just induces understeer? Especially with some of the mentally heavy springs you guys are quoting?

I've gone for 450 front / 500 rear, which is a good balance in my opinion, unless you are a pro driver who wants to drive the worlds twitchiest car...

Call me a cynic but why do you guys insist on heavy front springs?

Sorry to revive this thread...

I've just had a good chat with Julian at Balance Motorsport, in conjunction with AST.

I'm buying coilovers for my 197 track project, and couldn't figure out why a lot of you opt for heavier springs at the front and lighter at the back. Surely this just induces understeer? Especially with some of the mentally heavy springs you guys are quoting?

I've gone for 450 front / 500 rear, which is a good balance in my opinion, unless you are a pro driver who wants to drive the worlds twitchiest car...

Call me a cynic but why do you guys insist on heavy front springs?

I use my Ph1 172 for Hillclimbing and currently run 500lb fronts and 650lb rears as you can see from this photo 500lb springs up front still isn't enough nor is the camber (currently 2.25 neg but needs to be 3.0 neg)
To keep the ratios front to back the way I like I think I'm going to go 650lb fronts and 850lb rears although this will require an upgrade from my GHA's as they are currently maxed out on the damping.
I have to say it's quite horrific to drive on the road but awesome on the hills (I have to drive it to and from the events)

Rich

 

[Tony Hunter]

This is all very well, but tbh, you cannot find the answer on the internet.
We tested, tested, and tested some more, we were lucky to get a box of springs from Curtis at AST, and just kept trying them, all with different camber and toe settings.
Suddenly the car felt good, very good, we didn't even look at the final spring rates, as the car felt epic, that was good enough.

Flat through Craner Curves at Donington was good enough.