Which shocks for GC coilovers on a 99 GSX.

[jtmcinder]

No need to apologize, Charles; anyone with data or an open mind can play.

What spring rates were on the Shockteks that bent? The amount by which a spring resists being bent is proportional to its rate, so the side-force issue that we're worrying about depends on this. At the same time, higher-rate springs allow for more lowering, so the issue is usually magnified even more.

- Jtoby

 

[cait sith]

I talked this out with John M. at RRE and he convinced me that coaxial hats had more minuses than pluses in my case. He still would sell them to if I insisted, of course, but he talked me out of it. And when a vendor talks a customer out of buying something, that usually gets my attention.

- Jtoby

I find this interesting because the JIC FLT-A2 setup that I had him build for me seem to have Coaxial hats (Red andonized jobby at the top). Or at least the spring is not banging right on the upper mount, so to speak.

http://img34.exs.cx/img34/4980/frontpair.jpg

http://img45.exs.cx/img45/2029/rears.jpg

My apologies for the weak photos, it's all I got of the setup off the car.

 

[Poloturbo]

Part # = USS10.5-2.5

Thank you. Are thoses the same as this pictures above?

 

[ACM]

No need to apologize, Charles; anyone with data or an open mind can play.

What spring rates were on the Shockteks that bent? The amount by which a spring resists being bent is proportional to its rate, so the side-force issue that we're worrying about depends on this. At the same time, higher-rate springs allow for more lowering, so the issue is usually magnified even more.

- Jtoby

Rats, you would ask that - note that data is conspicuously absent from my post...

Currently I have 700/550 on the Shockteks, but I think I started out softer than that. To confirm this I have to get into the garage, and that requires melting the ice floe that's up against the door - somehow I don't think my hair dryer's up to that task. If I was running softer springs, it would be about 600/450.

Charles

 

[Jeff_Jeske]

Just buy the collars for GC...Dont get the whole sytem.

Also check out DSS coil overs on konis..

QA1 springs... 4 x ~$36

Are you telling to get collars and sleeves from GC then get springs from QA1? Why would a QA1 spring be any better than a GC?

Or are you telling me to look for a complete coilover system from DSS? I am guessing this is just another option to GC. Are there any benefits such as price or performance?

Lastly, are the stock GC springs 7" front and rear?

Ok did some digging....apparently DSS uses hypercoils which are said to be better than Eibach. However DSS coilovers are not available for 2g cars. People are using GC sleeves with hypercoil springs.

 

[jtmcinder]

GC springs are Eibach Race Springs. Better than QA1. Not as good as HyperCoils.

Yes, GC will want to send you 7" front springs, but you want 8". Less chance of binding. 7" is fine in the rear, although 8" is nice (if you have a flat plate) so you can swap them around for experiments.

...

Yes, FLT A2s have coaxial hats, but they also have adjustable bodies that can be set to be very short. So you can have the pluses of coaxial hats without one of the major costs. The argument that we're having is not one of "is this good ... yes or no?" because the items in question have good points and bad points. The question is whether it's worth it. Well, if you can get the positives without one of the major negatives, then - obviously - that shifts the balance a bit.

Continuing the above, another factor that comes into play here is the spring rate. And another factor is whether the shock's parts are more or less prone to the negatives of side-forces. Low spring rates (which also means that maximum travel is more important) and shocks that don't mind some side-force move you away from coaxial hats. High spring rates and shocks that are tempermental move you towards them.

Blanket statements are dangerous.

- Jtoby

 

[cait sith]

This is true, I did forget the fact that the Koni's have a lot more body length than the adjustable body length of the JIC's which gives them less travel room to play with.

 

[MNGSX]

GC springs are Eibach Race Springs. Better than QA1. Not as good as HyperCoils.

Yes, GC will want to send you 7" front springs, but you want 8". Less chance of binding. 7" is fine in the rear, although 8" is nice (if you have a flat plate) so you can swap them around for experiments.

Blanket statements are dangerous.

- Jtoby

My QA's have'nt sagged.. Can anybody say that about ERC or sportlines.. etc..

IMHO they are on par with Hypercoils I have looked up the materials and seen their shop. They just skip sizes from 7" to like 10" in lengths instead of having the 8" on up..

As for length.. Why would a 7 bind and a 8 not on a lowered car? Not like there is enough travel. At stock/near stock maybe 8 is right. There is a ratio of travel to required spring free length. Lowered 2" an 7" is'nt more likely to bind at stock height I think you are right.. it's more likely but has anyone see it happen... especially with spherical upper bushings and hats?

 

[DG-FNR]

The JICs do use coaxial hats. It's a shame that the forces they produce are so wonky and that they are single-adjustable in compression AND rebound simultaniously.

The issue with coax hats - as has been stated over and over and over again - is less about the side forces on the shock rod (although those can be fearsome) but is rather is more about the ABSOLUTE NECESSITY that springs be compressed as squarely as possible.

A spring that is compressed out-of-square has a rate that is both nonlinear and unpredictble, because the spring bows outward and does other funky things. The actual RATE will vary as a function of both the amount of compression on the spring and the degree of non-angularity.

This is very easy to see if you have access to a scale, a spring, and a press. Jig the spring up so that the ends are even slightly nonparallel, and the rate will be wildly different than what the rate is supposed to be - and it will CHANGE as the spring is compressed (usually the rate drops, but not always) . Change the angle on the base, and you get a completely different rate vs stroke length function.

NOTE - If you actually try this test on your spring rate tester or via a jury-rigged deal on a scale and a press, be ABSOLUTELY SURE that the spring is positively captured by your setup. A spring that is nonsquarely compressed can shoot out of the rig, and does so at like a million miles an hour. This CAN KILL YOU. Under no circumstances compress a spring unless it is restrained. See http://www.mktechnologies.com/ for an example of an excellent spring tester design.

Now then, a DSM shock pivots through the bearing/bushing area as the suspension moves through its range of motion. The front suspension, in addition, pivots the shock as the steer angle changes. This means that the actual angle between the centreline of the shock and the base of the upper shock mount plate is a function of the amount of travel (rear) or the amount of travel and the amount of steer angle (front).

If the top of the spring is resting on the underside of the upper mount plate (as it does in the Ground Control design at least) then the amount of non-squareness of the compression of the spring is the same as the angle between the centreline of the shock and the underside of the mount plate - which means that it is a function of current stroke position and steer position.

What happens as you negotiate a corner? The steer angle first increases (going in), then decreases (going out). The stroke position changes as the sprung mass rolls. And the rate of that nonsquarely-compressed spring is COMPLETELY UNPREDICTABLE AND IT CHANGES AS THE CAR GOES THROUGH THE CORNER.

The odds on these changes being beneficial to grip are practically infinate. It is much more likely (and I have experimental observations to confirm the predictions) that all these spring-rate monkeyshines will result in a loss of grip.

When you switch from under-plate mounts to coaxial hats, there is an immediate and noticable increase in grip. The car becomes far more predictable, and reacts much more predictably to spring rate changes.

The best proof I can offer is that while everybody else in DSM-land (save perhaps Charles) is running lots of rear spring and bar to try and loosen the car and get it to turn, I am running much more front spring (900 lbs - and I may try more) less rear spring (400 lbs) and the STOCK REAR BAR with the RM Racing front bar - and the car has a slight corner-entry OVERSTEER (which makes sense when you run the numbers and see the weight transfer distribution figures)

This setup would push like a pig for anybody else, but for me, it makes the front end stick better, the car turns in better, and net understeer is reduced. Why? Because the springs (the front springs especially) are acting the way they are supposed to and the tires are producing grip. I don't have to unstick the rear of the car to counteract understeer. Instead, I make the front stick better and go faster overall.

Coaxial hats are not something I pulled out of my ass. You'll see them on every serious race car that uses coilovers. You will not see a single IndyCar, F1 car, WRC car, DTM car, le Mans car etc etc etc without a coaxial hat - and every single race I ever won in a DSM was done on a car so equipped.

JToby will of course claim that this isn't proven out yadda yadda yadda because gainsay me is what he does. I hope everybody has seen all the evidence at this point that he's just trolling as per usual.

But if you don't belieive me, first pull a front wheel off, and watch the top of the shock and spring while a helper moves your steering from lock to lock, and watch the spring (assuming you have under-plate mounts) bend and bow. The do a rate check with the spring compressed non-squarely, and see what happens. Then you tell ME if you think a coax hat is necessary or not.

As far as spring sagging goes, you need to measure spring free height in terms of thousandths of an inch. A spring that has sagged 0.050" is garbage. That's not something you measure with a ruler or a couple of fingers stick in the fender arch.

Spring free length isn't really a theoretical issue - a 7" spring of x rate works every bit as well as a 12" spring of x rate, and vice-versa. As the rate goes up, the wire diameter increases and the amount of compression the spring can see before coil bind occurs drops, but this isn't a real issue for reasonable rates on DSMs. A 7" spring should be fine on a DSM from a coil bind perspective.

Where free length does get more interesting is with regards to where the coilover sleeve sits with regard to the shock and spring. All else being equal, for the same ride height, a shorter spring moves the lower spring perch higher on the shock, and a longer spring moves the lower perch lower on the shock. Depending on where the coilover sleeve sits on the shock, it is possible to run out of adjuster travel either up or down. GC's sleeve height is a little too low for best use of a 7" spring; an 8" is a better fit.

I'm going to place the coilover sleeve on our shocks such that with an 8" spring, "slightly lowered" will be at the centre of the adjuster range. This should provide maximum adjuster range.

DG

Learn: http://autocross.dsm.org/books.html

 

[MNGSX]

I should take pics but if you like the car a bit lower than most a 7" spring gives you more adjustment range where you like it.. Lower...

To each his own but DG just backed up that a 7" spring wont bind with DSM travel.

Also if you run hats on the flat RRE plates you will have a lowered (a bit) upper spring perch with GC collars.. a 7" will more closely match the lower seat location at a given ride height.

As for the DG setup it's an engineering issue. They want to use a given spring brand which comes in 8" but not 7" so lower the centerline of the lower perch sleeve.

There is more than one way to skin a cat.

 

[MNGSX]

DG

How are you dealing with a springs tendancy to want to rotate?

 

[DG-FNR]

DG

How are you dealing with a springs tendancy to want to rotate?

Torrington bearings in between the spring and the perches, as an option.

It's not that big a deal on a street car. It is a little bit of a deal on a full-race car. I installed them on my car mostly because my suspension position sensors are attached to the coaxial hats on the top and to the pinch bolts on the bottom, and when the hat rotated it tried to twist the sensors apart. Torrington bearings on the perches solved the problem.

I actually simulated this on the shock dyno, running a coilover shock/spring on the dyno with and without the bearings installed. With the bearings, the spring "floats" and cannot put any rotational load on anything. It also makes ride height changes a little easier.

The downside is that the bearings need a little TLC. They need to be greased every once and a while or they will rust.

For the super-overkill solution, Hypercoil makes hydraulic load-balancing hats and perches, but they are big money.

DG

Learn: http://autocross.dsm.org/books.html

 

[MNGSX]

Torrington bearings in between the spring and the perches, as an option.

It's not that big a deal on a street car. It is a little bit of a deal on a full-race car. I installed them on my car mostly because my suspension position sensors are attached to the coaxial hats on the top and to the pinch bolts on the bottom, and when the hat rotated it tried to twist the sensors apart. Torrington bearings on the perches solved the problem.

I actually simulated this on the shock dyno, running a coilover shock/spring on the dyno with and without the bearings installed. With the bearings, the spring "floats" and cannot put any rotational load on anything. It also makes ride height changes a little easier.

The downside is that the bearings need a little TLC. They need to be greased every once and a while or they will rust.

For the super-overkill solution, Hypercoil makes hydraulic load-balancing hats and perches, but they are big money.

DG

Learn: http://autocross.dsm.org/books.html

I have seen those... Hydro-lower perches and hats.. Spendy...

I'd look at some bearing company catalogs.. I have seen housed sealed torringtons...

 

[jtmcinder]

So, if anyone has access to a spring tester, please go ahead and do what you have to in order to be safe, introduce about a 5 degree angle, and see how the rate is changed at various amounts of compression between 20% and 80%. I guess you should first verify that the spring is linear in it's middle 60% of range, as good compression springs should be.

Since a relatively standard manufacturing tolerance for squareness of ends is 3 degrees, I'm not expecting huge changes, but I'd love to have some data to go with all the homey stories about real race cars and such. And, in case it isn't clear, I like my data uncontaminated by other simultaneous changes.

Yadda Yadda Yadda

- Jtoby

 

[jtmcinder]

A spring that is compressed out-of-square has a rate that is both nonlinear and unpredictble, because the spring bows outward and does other funky things. The actual RATE will vary as a function of both the amount of compression on the spring and the degree of non-angularity.

Dennis -

I have found many sources for the idea that non-squareness of compression can cause bowing and, therefore, violations of the basic 4:1 (length to diameter ratio) rule with regards to buckling, but I can find nothing to suggest that mere bowing alters the spring rate. The closest that I've seen is when bowing causes the spring to contact the body of the shock, which, of course, will alter the effective rate, but this can't be what we're worried about, since I've never even heard of this happening on a DSM.

How sure are you that non-square compression and/or bowing causes a change in the spring rate, assuming that the spring does not contact the shock and that the spring does not buckle? And, if you are sure, can you direct us to a specific source? TIA

- Jtoby

 

[ACM]

As far as fluctuating spring rate is concerned, consider the following.

Running GC-type top mounts I have significant wear evident on both my Koni/GC setup and on my Shocktek/GC setup, indicating that the spring is binding/catching on the top of the damper constantly. Once I switched to co-ax top hats this wear barely increased at all - even with this setup being swapped onto my 98 for daily driving 2 years ago. Fedja's Penskes now have something like 3 seasons on them, including 1 season doing daily driver duties - there is virtually no wear at all of this type.

This is only evident on the front assemblies, of course.

If the spring is hanging up on the top of the damper body or coil-over sleeve, it's altering the effective length and number of effective coils - that will change the spring rate dramatically - aside from wearing holes in the damper body, which is also less than optimal. Either of these reasons is sufficient to justify co-ax hats.

How significant is the spring's desire to rotate ? One would think that if this is so the squishy rubber spring isolators would exhibit signs of fretting, yet none of the ones I have (4+ sets) exhibit this at all. I would not argue at all with isolating every component as far as possible however.

 

[MNGSX]

As far as fluctuating spring rate is concerned, consider the following.

Running GC-type top mounts I have significant wear evident on both my Koni/GC setup and on my Shocktek/GC setup, indicating that the spring is binding/catching on the top of the damper constantly. Once I switched to co-ax top hats this wear barely increased at all - even with this setup being swapped onto my 98 for daily driving 2 years ago. Fedja's Penskes now have something like 3 seasons on them, including 1 season doing daily driver duties - there is virtually no wear at all of this type.

This is only evident on the front assemblies, of course.

If the spring is hanging up on the top of the damper body or coil-over sleeve, it's altering the effective length and number of effective coils - that will change the spring rate dramatically - aside from wearing holes in the damper body, which is also less than optimal. Either of these reasons is sufficient to justify co-ax hats.

How significant is the spring's desire to rotate ? One would think that if this is so the squishy rubber spring isolators would exhibit signs of fretting, yet none of the ones I have (4+ sets) exhibit this at all. I would not argue at all with isolating every component as far as possible however.

My rear stock isolators were worn clear thru and you could see the end of the spring digging into the front one...

I bought GC collars used and cheap.. The previous user must have experienced a bit of spring to collar contact in the front.. I'm running a full inch lower than he was and have no contact.. 2.5" vs 1.5" drop..... It is all because of the hats..

The spherical bearing shock mount keps me from seeing shock fluid leaking all over.... Without the hat you can rub the spring on the shock and guess what... Side loading even with pillows...

 

[RU2SLOW?]

I don't mean to go off topic at all, but something was mentioned earlier in this thread that really intrigued me. I believe that something was said that the Koni Yellows use a different ring to fit the GC sleeves that the AGXs do- am I correct with this?? The reason that I'm asking is that I'm looking into changing my front shocks to Koni Yellows from AGXs in an attempt to improve ride quality (and performance from what I've read) and keep my AGXs in the back for adjustability purposes- I'm FWD and need the stiffer rear for launches. I was afraid that I would have to buy new front GC sleeves that were made specifically for Konis, but if I understood this correctly, I should be able to just call up GC and order the rings for the Konis instead. Am I way off with muy understanding? Thanks for any help...

 

[Jehu]

How sure are you that non-square compression and/or bowing causes a change in the spring rate, assuming that the spring does not contact the shock and that the spring does not buckle? And, if you are sure, can you direct us to a specific source? TIA

- Jtoby

Simple. Once a spring is bowed, any linear movement in the original spring axis will have two components. One of bending the spring, and one of compressing it. It is the changing interaction between the bending and compression components that lead to the non-linear *effective* spring rate.

 

[Revolution]

Cool. Now this is getting useful.

The issue with my old set-up was not the lack of a coaxial hat. The problem was the bushings that GC sends with their plates. They do not allow any movement, so they hold the shock shaft at a tangent to the plate. Since the lower shock mount is often not directly below the plate, this can bend the shaft.

If you calculate what the side-forces are likely to be due to the spring not being a tangent to the plate, they are not very great. They are not zero, but they are not enough to out-weigh the negatives of coaxial hats on a street-driven car. As long as the shock's shaft is free to move - as they are with any pillowball - I don't see the shaft getting bent again.

Keep in mind that if you try to run Koni Sports with coaxial hats, you will probably also have to switch to a spherical bearing at the lower shock mount, as well. Why? Because the stock rubber bushing in the lower LCA is pretty stiff and is partly responsible for pointing the shock's shaft in the wrong direction (assuming something like urethane or Delrin bushings at the inboard end of the lower LCA). With the spring no longer helping to spread the load of the car onto the chassis, any twisting of the bushing in the lower LCA must now be done by shock's shaft. You don't want this, so you should probably switch the lower bushing to spherical at the same time. And that means metal-on-metal at both ends of the coilover unit. And that means you don't want to drive the car on the street.

Sorry about the ruder comments, MNGSX; I blame it on haste and a lousy web-site. Those are, indeed, hats. My bad. In fact, isn't 10.5mm the diameter of a Koni Sport's shaft?

- Jtoby

Jtoby,You stated "that if you try to run Koni Sports with coaxial hats, you will probably also have to switch to a spherical bearing at the lower shock mount, as well. Why? Because the stock rubber bushing in the lower LCA is pretty stiff and is partly responsible for pointing the shock's shaft in the wrong direction (assuming something like urethane or Delrin bushings at the inboard end of the lower LCA). With the spring no longer helping to spread the load of the car onto the chassis, any twisting of the bushing in the lower LCA must now be done by shock's shaft. You don't want this, so you should probably switch the lower bushing to spherical at the same time. And that means metal-on-metal at both ends of the coilover unit. And that means you don't want to drive the car on the street."
Please go more into detail.

I was actually thinking of adding an accurate tech coaxile hat to my cars setup which is consisting of hr sport springs on koni yellow shocks.

But after re-reading your post I feel ,well abit more confused. If the differences between a coilover and a spring /shock combo is minimal (and I mean that only to save me from typing everything that sepereates them) why would a hat react any differently to my combo versus a coilover.And is it a must to change lca busghing when adding a hat or no?

 

[DG-FNR]

The only reason to change out the lower control arm bushing is to get rid of the inline spring the bushing represents - which is a good idea, but not a "must do", like the upper mount is.

BTW, I can sell you a set of nice hats with a car attached to it. See http://www.dsmtuners.com/classifieds/showproduct.php?product=29031&cat=4&page=1

DG

 

[D_Eclipse9916]

JNZTRBO, if you're in the northern VA area I'd let you take my gsx for a spin to see what problems I have with the high spring rates and illuminas Just drop me a pm and I can set aside some time for it.

[edited for typo]

Hahahaah wanna offer that to me too . I live in Tysons Corner, are you making it to the rockville meet this saturday? You should!

 

[jtmcinder]

My lower shock bushings are stock while I have RRE coaxial tops. No problems at all.

Glad I wrote "probably."

- Jtoby

 

[Revolution]

Thanks guys ,for clearing this up for me, and everyother enthusiast that likes turning the wheel at speeds.

DG im sorry to here your selling the car,but then again everyone needs to move forward sometime, will you be thinking about purchasing the next nissan skyline r34 which should be allowed in canada as soon as it goes for sale in the states? I would imagine after your car you would want something, how do I say just as good.

Jtoby thanks for letting me know your setup is treating you good, now I wont have to worry.

Lastly ,I really dont need hats for the rears do I? Or is their something specifically for the rears I should be looking into to?

 

[jtmcinder]

You could argue two ways about the rears. On one hand, the angles between the shock and the plate do not change much in the rear, so coaxial hats could be seen as overkill. On the other hand, the ratio of unsprung to sprung weight is really high in the rear, so any stiction issues will be much worse, arguing in favor of hats.

In the end, I got all four.

- Jtoby