1g road course suspension, *needed* 1g stock strut dimensions

[drivemusicnow]

Soooo as it goes, I've finally saved enough pennies to revamp the suspension for my 1g track car. I'm a graduating senior mechanical engineering major and am taking a very analytical approach to this. This would be all well and good except my analysis is leaving me without an ideal choice. I've separated the components and these are my thoughts on each. (This is assuming a full track car, bushings/active toe etc, and measurements have been taken care of) Due to class rules/restrictions, I'm not going to be relocating any of the suspension components

Struts/dampers
KYB, Megan/Ksport/d2, tein: The dampers on these products are generally terrible. They do have the positive aspect of being super cheap.
Koni: the OTS yellows, while being a technically good shock don't provide the performance I'm looking for. They are too soft in compression, and the rebound adjustment is typically only good for matching the shocks. While Dennis Grant may think they're the best option, I think with a little creativity we can do better. My backup option would be to have them revalved however at ~75$ per corner, that increases the cost significantly.
JIC: The stock JICs have been proven to have bad dampers. They've also proven to support fast cars when purchased from Mueller. The people that have shock dyno'd them have responded with similar amounts of disgust. Being the engineer that I am, I refuse to pay close to $2000 for the shocks from John Mueller without knowing what I'm buying.
Hotbits: I like this option with a few concerns. The shock has been dyno proven, they offer a DA option for a bit more money and I can have them rebuilt easily and cheaply. The negatives are the initial cost (2146$ for the DAs, without front or rear top mounts) add the cost of their top mounts (we'll discuss lower) or making my own and you end up with almost 2700$ for something that is as of yet, mostly unproven in a road course setting.
Koni Race Dampers
Now, most of the koni race offerings are expensive or unusable, but
Koni just happens to make a series of dampers that is quite interesting to me. I've been talking to Phil at truechoice about the possibility of using either the single or double adjustable (8611 or 8610). Unlike most of their race dampers that are eyelets on both ends, these are insert style replacement dampers with threaded strut rods. The SA are listed at 187$ apeice, while the doubles are close to 310. I think what they did here is take standard koni yellows, shorten the shock body, increase and narrow damping forces and offer it as a generic part rather than vehicle specific. I was also hoping that some one had some blown stock struts they could take some measurements for me, or that I could purchase them. I really would like to make the koni race shocks a viable option, but I just don't have the time right now to go searching through 50 classifieds emailing people for stock struts.


Top Mounts
The two off the shelf options are RRE's and Ground controls. RRE's is superior because of the 3 piece design that allows for better shock articulation. The disadvantage of both is that they're built for a stock shaft size and I'm not sure if the koni race shocks or the Hotbits use the same size (have emails out to find out). The Hotbits have the option to come with their own top mounts however they do not separate the car weight forces from the damper forces which is known to prematurely wear the spherical bearing. They also don't use a thrust bearing which can make adjustment on the car more difficult.

Spring rates
There are a couple different ways to solve for this. The "correct" way is to solve for the roll stiffness front and rear which includes suspension geometry, springs, and ARBs. I'm still calculating this as I don't have the ability to measure a couple things right now. I go to a heavily automotive biased university, which allows me access to some pretty cool pieces of suspension design software. I should have an analysis prepared in a couple weeks. (that is, if finding a job and finishing up my 24 credit hours of classes doesn't stop me) Either way, hypercoil springs and I'm initially trying them without helpers, and 8 inches tall. I'll update this as I go. (initial, un checked and guestimated numbers give me rounded values of 450/450 front and rear with stock bars, and 450/400 with the RM rear bar)


I'd like to hear some thoughts and opinions. I've got too much time into this that I might be too close to see something obvious. I'm willing to put about 2500$ into it, but I'd obviously like to do something cheaper.

[Ludachris]

This is going to be a good discussion... and I look forward to the results.

I would only suggest considering shorter springs - I think I had to go with 7" in the rear due to lack of adjustment threads left on my Ground Control sleeves. However, that may depend on the solution. And stiffer spring rates might be considered as well. Some people are looking at 500-600 lb springs for the 1g in front. But that will depend on a lot of things as well.

[asian312]

You make some very interesting claims. Do you have any resources to back these up?

KYB, Megan/Ksport/d2, tein: The dampers on these products are generally terrible. They do have the positive aspect of being super cheap.
I agree that the reputation of the D2 and KSports showing an alarming rate of blown units coupled with a relatively short life market life span is worrying. But the Pro units on a friend's 2G around MSRC felt quite stable and suited for track conditions. Granted they were rubbish on the street. The Teins have mixed reports as well in many communiies. However the 'Basics' are highly regarded in the Miata community.


Koni: the OTS yellows, while being a technically good shock don't provide the performance I'm looking for. They are too soft in compression, and the rebound adjustment is typically only good for matching the shocks. While Dennis Grant may think they're the best option, I think with a little creativity we can do better. My backup option would be to have them revalved however at ~75$ per corner, that increases the cost significantly.
What kind of performance are you looking for? What kind of spring rates are you looking for? Bang for buck I think they're hard to beat coupled with the right spring or coilover.

JIC: The stock JICs have been proven to have bad dampers. They've also proven to support fast cars when purchased from Mueller. The people that have shock dyno'd them have responded with similar amounts of disgust. Being the engineer that I am, I refuse to pay close to $2000 for the shocks from John Mueller without knowing what I'm buying.
Once again this sounds like these are being grouped together with all the other 'asian' shocks. If they are such a bad platform, why would John use them as a base? Why not a Tein or another brand that has a large amount of US support? Mr. Mueller has manage to place them on a few iconic DSMs in recent years. Scott Gray's 1G had them, Roy's 2G (also featured in the SCC USCC) took top honors with the fastest lap using these, and Greg Collier's car were supported by these JICs to 2 SU Championships. This one doesn't add up. Or maybe there's just enough adjust ability to shoot yourself in the foot.

Hotbits: I like this option with a few concerns. The shock has been dyno proven, they offer a DA option for a bit more money and I can have them rebuilt easily and cheaply. The negatives are the initial cost (2146$ for the DAs, without front or rear top mounts) add the cost of their top mounts (we'll discuss lower) or making my own and you end up with almost 2700$ for something that is as of yet, mostly unproven in a road course setting.
Unlike those listed above, these are the exact opposite where there are fewer examples of these units on DSMs. Curious as to what constitutes 'Dyno Proven'.

Koni Race Dampers, Penske, other racing shocks
While 'm not ready to spend $700$ per corner, what kind of understanding of the art of suspension is required to bring out their full potential?

Please don't take any of this personally. I'm just playing devil's advocate as I'm asking myself these very same questions.

[ian7321]

What he means by dyno proven is that the dampening and rebound values are very consistent across the product line.

While JIC and Tein have been found not be very consistent. There was a good thread on this site somwhere search for hotbits and shock dyno.

-Ian

[drivemusicnow]

Originally Posted by asian312

You make some very interesting claims. Do you have any resources to back these up?

As a matter of fact I do. My information has come from an indefinite amount of time researching this online, as well as driving a few non dsm cars with various suspensions. Start googling *insert shock name here* + dyno graphs.
First thing to remember is that what feels good/stable/handles on rails/etc does NOT mean they are doing a better job. In fact, I've noticed a direct correlation between what people think is making their car handle better, and shocks that are actually valved entirely wrong. This is important to notice that suspension is something that is easily misunderstood/felt.

Originally Posted by asian312

KYB, Megan/Ksport/d2, tein: The dampers on these products are generally terrible. They do have the positive aspect of being super cheap.
I agree that the reputation of the D2 and KSports showing an alarming rate of blown units coupled with a relatively short life market life span is worrying. But the Pro units on a friend's 2G around MSRC felt quite stable and suited for track conditions. Granted they were rubbish on the street. The Teins have mixed reports as well in many communiies. However the 'Basics' are highly regarded in the Miata community.

It's possible that I threw tein in there in error, Maybe more discussion is needed, however from all the dyno plots that i've seen, they provide the exact opposite response as they seem to be progressive. This means that smaller speed movements instill less force and the ratio of force to speed gets progressively larger (essentially the worst possible curve, however it creates a more comfortable ride). Koni yellows are digressive which means they increase in force quickly at low speeds, and then the ratio gets progressively smaller. Linear would mean that the shocks increase in force to velocity in a linear manner. All race shocks are digressive. the Hotbits are linear, however you could revalve them to be digressive. JICS are digressive however only slightly so.

Originally Posted by asian312

Koni: the OTS yellows, while being a technically good shock don't provide the performance I'm looking for. They are too soft in compression, and the rebound adjustment is typically only good for matching the shocks. While Dennis Grant may think they're the best option, I think with a little creativity we can do better. My backup option would be to have them revalved however at ~75$ per corner, that increases the cost significantly.
What kind of performance are you looking for? What kind of spring rates are you looking for? Bang for buck I think they're hard to beat coupled with the right spring or coilover.

I do believe these fit into the best bang for the buck category. My opinion on this is that the cost difference between 1500$ and 2500$ is not all that much for a significantly better product. I'm not willing to spend 1500$ on something and dislike it, or feel like I left something on the table. They also have slightly too long of a shock body to get proper performance out of lowered car. You'd be best off keeping them at .5-1 inch below stock ride height maximum. Spring rates I'm looking at are a minimum of 450/400. I'm waiting until I properly figure out roll stiffness front and rear. The other problem being of course that to purchase them (~700$) and then another 300$ for revalving seems like there may be better options (maybe not) out there.

Originally Posted by asian312

JIC: The stock JICs have been proven to have bad dampers. They've also proven to support fast cars when purchased from Mueller. The people that have shock dyno'd them have responded with similar amounts of disgust. Being the engineer that I am, I refuse to pay close to $2000 for the shocks from John Mueller without knowing what I'm buying.
Once again this sounds like these are being grouped together with all the other 'asian' shocks. If they are such a bad platform, why would John use them as a base? Why not a Tein or another brand that has a large amount of US support? Mr. Mueller has manage to place them on a few iconic DSMs in recent years. Scott Gray's 1G had them, Roy's 2G (also featured in the SCC USCC) took top honors with the fastest lap using these, and Greg Collier's car were supported by these JICs to 2 SU Championships. This one doesn't add up. Or maybe there's just enough adjust ability to shoot yourself in the foot.

That's the conundrum. They have supported fast cars, when purchased from Mueller as I stated. Mueller is now pushing away from them for Evos, to the buddy club and moton options. Why? your guess is as good as mine. Do a google search for "JIC shock dyno data" there are literally dozens of forums that have threads with dyno data in them. They also aren't all bad. (probably overstated that in my first post) They aren't necessarily good either. The one thing I've noticed is consistency is not their game. Either way, I refuse to pay that kind of money for something that he grinds spring values off and doesn't tell whether he revalves them or waves a magic wand at them. The other option being that I learn for myself, purchase the 1650$ set, set them up on my own, revalved or different spring rates as I learn. They also have super shitty customer service though.

Originally Posted by asian312

Hotbits: I like this option with a few concerns. The shock has been dyno proven, they offer a DA option for a bit more money and I can have them rebuilt easily and cheaply. The negatives are the initial cost (2146$ for the DAs, without front or rear top mounts) add the cost of their top mounts (we'll discuss lower) or making my own and you end up with almost 2700$ for something that is as of yet, mostly unproven in a road course setting.
Unlike those listed above, these are the exact opposite where there are fewer examples of these units on DSMs. Curious as to what constitutes 'Dyno Proven'.

Dyno proven is shock dyno data proving that they respond the way a shock should under the forces/speeds it sees.. I've spoken with both Peter Reilly and Larry Parker about them, seen dyno data (posted on gvr4 forums and from Larry) They look good, from a purely technical point of view... but then do they make for faster lap times? I don't know and they are not nearly as big in the US as other options. These shocks are also very hardcore though. They're widely used in rally and don't break.

Originally Posted by asian312

Koni Race Dampers, Penske, other racing shocks
While 'm not ready to spend $700$ per corner, what kind of understanding of the art of suspension is required to bring out their full potential?

Please don't take any of this personally. I'm just playing devil's advocate as I'm asking myself these very same questions.

Suspension is NOT an art. It's very much a science and that's what really bugs me. There have been years and years and years of knowledge base passed on to consumers for engine tuning and horsepower gains. This "suspension age" is really just beginning and many people are at the ground level looking up. Heck, most people don't even care how their cars are acting as long as it feels looks and sounds fast.

Now, the more adjustment, the harder it is to setup obviously as there is more to "set correctly". The advantage comes in that you can more accurately tune it to your vehicles behavior. You don't have to have them valved perfectly for your vehicle because you have a bit of play either way.

[asian312]

I say suspension is an art, because science has more to deal with fact's and truth's laid out on paper. While they may be true, it's up to the individual (driver) in this case to find what matches and suits them. Therefore what's laid out on paper is not necessarily the best setup for a given driver.

I've done some searching myself, and what information out there that is readily available often contradicts itself or lacks comparable results (front vs. rears, mid range model vs. high-end model, price differences, etc.) However there are a few good sources of empirical data floating around, but nothing conclusive and I've certainly not found any conclusive evidence for either direction.

I'll kick back and see what comes of this.

[GreenGSX]

Originally Posted by drivemusicnow

They also have slightly too long of a shock body to get proper performance out of lowered car. You'd be best off keeping them at .5-1 inch below stock ride height maximum. Spring rates I'm looking at are a minimum of 450/400.

There are other reasons not to lower a 1G car beyond ~1" regardless of what springs or struts you choose. We can all agree that lowering the car with spring height adjustments is the quickest and easiest way to lower the cars center of gravity but there is no free lunch. 1G cars have a relatively high roll center of gravity and when you get the center of gravity near or beyond the roll center wacky things happen. Most guys correct for that by using bars and lots of spring but ultimately the benefit is not there. The biggest and to me the most glaring issue with lowering a 1G too much is the angle of the tie rods and bump steer. If you put the car in the weeds prepare yourself for lots of bump steer.

I'll take my 400/350 Hyper-coil-Koni Yellow close to stock ride height over a "in the weeds high $$$ set-up" any day.

I also have not seen any mention of final race weight. That is going to be the biggest factor in selecting spring rates. How about matching the frequency of the springs to the shocks? Lots of good stuff here. Anybody try the FWD spindles which some say mount the tie rod in a different spot than the AWD cars allowing for a lower ride height? Can't wait for the alignment stuff to come up.

You know the more variables that get thrown in and relatively small number of guys who actually understand everything this suspension stuff is starting to look more like an art to me.

[drivemusicnow]

Originally Posted by GreenGSX

There are other reasons not to lower a 1G car beyond ~1" regardless of what springs or struts you choose. We can all agree that lowering the car with spring height adjustments is the quickest and easiest way to lower the cars center of gravity but there is no free lunch. 1G cars have a relatively high roll center of gravity and when you get the center of gravity near or beyond the roll center wacky things happen. Most guys correct for that by using bars and lots of spring but ultimately the benefit is not there. The biggest and to me the most glaring issue with lowering a 1G too much is the angle of the tie rods and bump steer. If you put the car in the weeds prepare yourself for lots of bump steer.

I'll take my 400/350 Hyper-coil-Koni Yellow close to stock ride height over a "in the weeds high $$$ set-up" any day.

I also have not seen any mention of final race weight. That is going to be the biggest factor in selecting spring rates. How about matching the frequency of the springs to the shocks? Lots of good stuff here. Anybody try the FWD spindles which some say mount the tie rod in a different spot than the AWD cars allowing for a lower ride height? Can't wait for the alignment stuff to come up.

You know the more variables that get thrown in and relatively small number of guys who actually understand everything this suspension stuff is starting to look more like an art to me.

I agree that lowering a 1g past 1 inch (heck, even at all) is not idea.

There are a lot of factors, however only some of them are variables. You're stuck with the same strut mount, the same inner control arm pivot axis, the same unsprung weight, the same (or close) corner weights/sprung weight.
You can change static camber, but the camber-displacement curve is the same. You can change spring rates and bar rates which effect roll stiffness. You can, sort of, change rebound and compression damping based on shock choice or adjust-ability.
You can change the CG, but only slightly, and as noted the roll center changes more than the CG does and has a more negative effect. When changing ride height you change where you are on the camber curve, as well as the tie rod angle, like you mentioned. I've also read about the FWD spindles haveing lower tie rod mounts. They are also further from the axis of rotation because of manual steering models I believe. (more mech advantage) this would give a duller steering feel (reduce torque steer as well) but i'm not sure how much (if any) of an effect this would have given 255 wide track rubber.

So lets set some of these constant. Race weight is 3000 lbs with driver. (it's slightly higher than that right now, but I'm not done removing sheetmetal) lets assume corner weights of 925,875-620,580

Solving for natural frequencies of 2.5 and 2.2... (I don't have my notebook from when I was working on this, IIRC it was close to 400/400)

Anywho, I'm not familiar with how to easily relate natural frequencies to shock force values. Unless you're speaking the entire transfer function/response of the system with a given input, which would be entirely to cumbersome to calculate for the dozens of different inputs a suspension sees.


I'll be the first to admit that I don't know everything about this stuff, but I will not let that stop me from learning as much as possible.

As another interesting sidebar. It looks as if my koni 8611/8610 plan is in full swing over at Race proven solutions | Zzyzx Motorsports. I'm going to talk to the owner and see if there isn't something we can put together. Seems like he manufacturers the strut housings to install the 8611s into. Could be exactly what I'm looking for. (good reference/papers section on their website as well)

[drivemusicnow]

A little update:

It seems that the 2g/3g rear Koni yellows may be a good solution in the rear for us 1g guys. The strut body is a bit shorter and the valving is slightly more "aggressive". It also is a NORMAL Koni top adjuster rather than the push to adjust ish.

The bottoms are the exact same, the threaded top is slightly different. Worse case scenario is that I create a new top mount for the rear, but hopefully I could just purchase someone elses/an EVO one.


The 8611 (which is what i'm going to use up front) uses the same M14 threaded top as stock does. This means that it will bolt into the RRE (or whoevers) top mount like normal. (still have to use RREs silly bushings because they didn't use metric spherical bearings, but hey, good enough is good enough.)

I'm trying to talk to zzyzx to see if they'd make a front strut housing for us that would A) allow you to slide the Koni race shock in and go, B) allow for a decent amount of camber change at the spindle and C) look pretty allow easy height adjustment.

As far as Costs (I know that's what you 1g guys want to see)

Rear 2g koni yellows: $155 Per (310$)
Front 8611s: 310 per ($620)
Hypercoil springs: 67 per ($266)
Rear coilover perches 130$ (truechoice/koni parts including bumpstops and such)
Front strut housing ??? (guessing from doing the math on his current offerings, it'd be about 150-250 per housing, so an absolute worst case scenario of 500$)
Rear top mount (Need to look into this more, but it seems like an EVO one would work. no more than 200$)


I have a feeling that the front housings will be significantly less, and the rear top mount can be done for less money as well. (hell, it's a piece of metal with a spherical bearing and two studs pressed into it)
Lowest possible cost option would be to use the stock housing and modify it to work with the front race shock. This could then be done for less than 200$ (100$ for the threaded perches and such, and ??$ for strut housing mods done by a machine shop)

This equates to a worst case scenario of 2026$. for everything.
I'm *guessing* a final cost of 1800$ or so for the DA fronts, 1550 for the SA fronts, and another ~200$ less than that if you use the stock front strut housings versus the fancy zzxyz ones.

[Zero Bar]

Lots of good info in this thread, keep it going!! Your spring rates sound right on, my car has 400F/350R with both sways, poly bushings, etc....it has little body roll at the track, it's weak point are the aging AGX's on the car so I can't comment much beyond the body roll. This is good info as if I keep the car it could use a suspension overhaul next season and I've been debating what to do.