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Discussion Starter · #1 ·
Just following up on the street vs track CG saga... :haha:

I just got done replacing my GC front #350 springs with the new #430 barrel springs...I also moved my rear Dinan bar to the middle position. I am running 275 fronts. My front ride height is now 14.25"+or -...rear is at 14" with the #315 springs...I am running about -1.25 camber on the fronts...

The spring swap was really easy...I'm not looking forward to exchanging the rears...I hope this combo works out...

So far no bottoming issues. In the short time that I have driven the car it seems to be very neutral. The ride is fine...With stronger rear springs ( and stock bar) this may be THE street set up...

I heading out to my favorite set of twisties in the Sierras and I hope this set up holds up...I will report back....

Mark
 

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great -- let us know know the results -- theoretically, this seems to be an ideal suspension for the M5

i'm still happy with the 550/425 with the wonderful turn-in and braking control, but know that not everyone will be happy with the "sports car" ride

any plans to for track days?
 

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Discussion Starter · #3 ·
I just got into Sacramento...put almost two hundred miles on the new set up...The only thing I can say is Holy Sh#t....I ran a set of 90 mile twisties between Hwy 88 and Placerville, Ca (PiPi Valley)...With the "old" #350 fronts, I seemed to bottom every 100 yards...It is a nasty, rutted out road, but it has very little traffic. The turns are spectacular...With the new set up...I only bottomed once!...and it was on the rear!...It was on a 80+ mph transition. The back end was very light under heavy breaking on an off camber...as I turned to the opposite direction to make the curve, there was a square edge bump in the road...it was a slight thud...nothing like what used to happen with the front end...it was a metal on metal contact... like your car's frame was hitting metal at speed...

With the rear Dinan track bar in the middle position and the "light" #315 rear springs (and the change in the static and dynamic lock up in my new rear end from Shadowman)... It took great effort to kick the rear end out..It is almost sad how much traction the rear end is getting...

The only time that I felt any significant push (I have 275s on the front) was off of road irregularities deep into the apex of a turn...I think that now that I have too much rebound dampening dialed into the front shocks to have compensated for the original lighter springs...I think that I am going to try 1.5 turns out from full soft instead of two...

So far the set up that I am running (with the extra -1.25 camber) seems to be an exceptional set up...

I am still grining ear to ear after this run...

Bill at D/A has to get some credit...I have not had a single SES light through any of my runs... they have lasted for hours over 4k rpm...

GC coil overs get a thumbs up in my book.... :wroom: :noSMG:

Mark
 

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Mark,

Thanks for the update on the GC springs! Keep us posted on any new impressions you have. I'm still undecided on what path, if any, I want to take with my M5's suspension, and your feedback is invaluable. :thumbsup:

Cheers,
Chuck
 

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Discussion Starter · #5 ·
CSBM5 said:
Mark,

Thanks for the update on the GC springs! Keep us posted on any new impressions you have. I'm still undecided on what path, if any, I want to take with my M5's suspension, and your feedback is invaluable. :thumbsup:

Cheers,
Chuck
Chuck,

It is hard to remember what the stock ride felt like...but the GC set up with the #430 front springs (and the approx #375 rears) is not that bad of a ride...I cannot compare to stever's ride, but he is close to me and we may just have to have a comparo ride...:)

Chuck...are you looking for handling or lowering ?

Order of handling upgrades (according to me :)) 275 fronts with a Dinan rear bar... and then go for the GC coil overs...the change is incredible...fun factor times ten...

Mark
 

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My primary focus is handling plus ride comfort. Nice set of opposed objectives, huh? I have ridden in Redshift's GC (350/315 I think) M5 on the street and around VIR. He has Stoptechs, 9.5/275 front, r-compounds, Dinan rear bar, etc., and it was simply wonderful around VIR, and I'm sure it would have been even better with the higher spring rates. On the street, his setup is what I would call very firm. Compression damping is much firmer than stock imo. Hence, for how I like to use my M5 at times (highway trips), I would find that setup too stiff, and I know my rear seat passengers would quickly grow weary of such a setup on a long trip over less than perfect roads.

If this was 20 years ago, I would instantly go with GC with the springs you are running, no questions asked...but now, I'm sort of in a middle zone wondering if the Dinan combo, perhaps Dinan springs and bars plus the newly released GC camber plates for the stock spring setup is the best path to take. I already have the 9.5"/275 front setup. This Dinan/GC setup would give me maximum negative camber adjustment for the occasional track day (A-group, 20+ years track experience) along with (hopefully) as close to stock ride compliance as possible for the rest of the time.

My other thought is to get an AA supercharger setup on my 330i ZHP and set that one up for track fun. After driving the M5 and V70R, the ZHP is a bit "light" on power for me. ;)
 

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CSBM5 said:
My primary focus is handling plus ride comfort. Nice set of opposed objectives, huh? I have ridden in Redshift's GC (350/315 I think) M5 on the street and around VIR. He has Stoptechs, 9.5/275 front, r-compounds, Dinan rear bar, etc., and it was simply wonderful around VIR, and I'm sure it would have been even better with the higher spring rates. On the street, his setup is what I would call very firm. Compression damping is much firmer than stock imo. Hence, for how I like to use my M5 at times (highway trips), I would find that setup too stiff, and I know my rear seat passengers would quickly grow weary of such a setup on a long trip over less than perfect roads.

If this was 20 years ago, I would instantly go with GC with the springs you are running, no questions asked...but now, I'm sort of in a middle zone wondering if the Dinan combo, perhaps Dinan springs and bars plus the newly released GC camber plates for the stock spring setup is the best path to take. I already have the 9.5"/275 front setup. This Dinan/GC setup would give me maximum negative camber adjustment for the occasional track day (A-group, 20+ years track experience) along with (hopefully) as close to stock ride compliance as possible for the rest of the time.

My other thought is to get an AA supercharger setup on my 330i ZHP and set that one up for track fun. After driving the M5 and V70R, the ZHP is a bit "light" on power for me. ;)
I would use some caution comparing springs or "kits" after a single test ride. This is especially true when you're considering ride characteristics of Dinan vs the softest GC offering, as the spring rates are quite similar. Any significant differences in street ride harshness would be attributed to the ride height set, bumpstop thickness...and most significantly, damper settings. You may notice that folks complaining of bottoming with GC kits have tried set ride heights under 14". In some cases, elevated damper rates are chosen to reduce bottoming, but this degrades ride quality on smoother roads and it is a bandaid for insufficient jounce travel. Dinan wisely offers a fixed ride height over 14" to ensure adequate jounce travel. GC owners can do the same by adjusting the ride heights to reasonable levels.

The Koni rear damper setting has a HUGE impact on ride quality and this characteristic has nothing to do with Ground Control or spring rates. When I set my rear Koni's to 66% of full firm (1-7/8 Turns from full soft), the car rode like a 1 ton truck and you literally needed a kidney belt in the rear seat. **The most interesting thing to note is...this rock hard ride was with STOCK BMW rear springs. Again, the car's ride went literally from supple to rock hard after a simple damper swap (and foolish settings).

A Koni rear damper setting near 3/4 Turn from full soft will still feel significantly stiffer than OEM Boges.
 

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Rick,

I've ridden in Redshift's car a number of times both on VIR full course and VIR Patriot course along with street driving, and I have driven it on the street, so my comments were not based on a single test drive. I think the GC compression damping setting on the GC-valved Konis is significantly increased compared to the stock setting...that's my impression anyway. I still believe, from experiencing it firsthand, that the ride is too stiff (although it is still "supple") for my desires of highway hauling with 4 people on board. I'm thinking that the Dinan setup with the GC plates may be the best compromise.

Chuck
 

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Discussion Starter · #9 ·
CSBM5 said:
Rick,

I've ridden in Redshift's car a number of times both on VIR full course and VIR Patriot course along with street driving, and I have driven it on the street, so my comments were not based on a single test drive. I think the GC compression damping setting on the GC-valved Konis is significantly increased compared to the stock setting...that's my impression anyway. I still believe, from experiencing it firsthand, that the ride is too stiff (although it is still "supple") for my desires of highway hauling with 4 people on board. I'm thinking that the Dinan setup with the GC plates may be the best compromise.

Chuck
Chuck,

Do you know what the settings (how many turns out from full soft) were on Redshift's car? The fronts are easy to adjust. You could run the fronts soft so that the expansion joints do not pound you and then crank it up when you want more dampening...I was driving with the #430 springs all week end (over 400 miles) and they really did not feel too much different from the #350 springs...If fact they almost felt softer...Compression settings were the same with both sets of springs...

Mark
 

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Mark,

I'll have to get Brian to comment on this thread as I don't know his settings. The Konis are only adjustable for rebound damping, btw, so there is no control over compression damping.

Chuck
 

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Discussion Starter · #11 ·
CSBM5 said:
Mark,

I'll have to get Brian to comment on this thread as I don't know his settings. The Konis are only adjustable for rebound damping, btw, so there is no control over compression damping.

Chuck
Thanks for the info...I thought that the front dial did both rebound and compression and the rear just rebound...

Mark
 

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I'm almost positive that compression damping is not changed. Ground Control Jay gave a presentation at the BMWCCA Techfest last year, and that is what I recall him saying...my memory could be faulty though.
 

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CSBM5 said:
Rick,

I've ridden in Redshift's car a number of times both on VIR full course and VIR Patriot course along with street driving, and I have driven it on the street, so my comments were not based on a single test drive. I think the GC compression damping setting on the GC-valved Konis is significantly increased compared to the stock setting...that's my impression anyway. I still believe, from experiencing it firsthand, that the ride is too stiff (although it is still "supple") for my desires of highway hauling with 4 people on board. I'm thinking that the Dinan setup with the GC plates may be the best compromise.

Chuck
Thanks for clarifying, but here's some points to consider:

1) Dinan, Saleen and countless other tuners have been pawning-off repainted dampers with OEM Koni valving for years. It's all about identity, bundling, profit, confusion and value-added marketing strategies. I am frankly surprised they don't grind off the Koni part stamping.

2) GC Konis for theE39 application are not uniquely valved either, despite rumors. GC offers uniquely-valved Konis for some applications, but not E39. They would likely offer custom valving or DA if you asked (as they do for E36 and E46), but it's not a common request for E39. Koni's race shop will provide most any custom mod & reselling is no biggie. GC does not upcharge for bundling yellow Konis with their coil-over hardware, so the issue is moot.

3) With rear rebound damping set "low", the E39 Konis are quite compliant and feel almost stockish. The sensation of better chassis control and firmness subsides within days. They will never feel like the wallowy, underdampened OEM Boges, but I would not characterize them as firm when set under 30%. The 540i community does not seem to complain, unless they choose an aggressive damper rebound setting. I have not found the added, fixed compression damping of the Konis to be "excessive"....more like "welcome". Keep in mind the Koni rear shock for E39 has compromise damping that's intended to please everyone from the non-sport 525i driver to the M5. A stiffer rear Koni is not sold for V8 application.

4) With rebound damping set around 50%, the M5 will ride like a truck. This is true of E39 Dinan Koni, GC Koni or Tirerack Koni. The only difference is color and price.

I plead no contest to your first hand assessment that the ride was not optimal with an UNKNOWN damper setting. I am not surprised as I have witnessed this situation first-hand. Higher rebound calibrations are not advised for street and not even helpful for track. Folks who are planning track time and guessing a baseline setting with no data generally crank up the dampers....I did. I learned this impacts ride quality. Ignoring ride deterioration, a higher setting makes the car unstable on variable road surfaces and a real handful in the rain.

Rebound damping has the greatest influence on ride quality. This is why Corvette FX3 and other cars with cockpit OEM adjustable suspension offer rebound-only adjustment. It will make a car ride like a dumptruck or a pogo stick. Neither characteristic is desireable in my opinion, so I like a set-it-and-forget-it setting. Reducing rebound excursions will reduce bottoming, but it's not a good solution.
 

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i'd pretty much guarantee that GC coilovers with 350# springs set 1 inch lower than stock ride height will hit the bump stops very frequently (take a look with a flashlight - the bump stops will be about 1/4 inch from the top of the strut)

CSBM5 you've got a difficult decision -- the Dinan 3 is a nearly perfect street suspension (what BMW should have delivered to us in the first place) -- but at your level of experience i think you'll be disappointed on track

the M5 is too heavy for the track and needs stiffer springs, race pads in front (and of course high temp fluid), and R-tires to be very responsive

is seems that just about everyone but me decides a lighter car for the track is the way to go (just met another M5 driver who picked up an E36 M3 for track)

no i'll go dial my front shocks back from 75% and see if it makes a difference (my rears are as delivered from GC and i'm sure are set at about 30-40%)
 

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CSBM5 said:
Thanks Rick...my impressions may be misfounded in that perhaps the harshness I felt a few times was more related to getting into the bump stops given the 350/315 springs and 1" or so lower ride height than stock.

Chuck
Redshift's car is super low and spring rates are modest. If you review threads, the title was appropriately "slammeroni" and the ride heights were in the 12.5" to 13" range. From my experience driving various hefty cars on-track at full song, I would think it's leaning solidly against the bumpstops in every turn...if not while sitting at rest. This would feel much like high rate springs or excessive compression damping. The complex bumpstops provided in the GC kit are quite high tech as they induce a gentle, progressive "rate gain" that feels much like a progressive spring. This allows the car to handle decent under bumpstop contact. With these bumpstops, the sensation of bottoming is quite muted. It would be very difficult to feel contact under most circumstances. If you hit a speedbump or similar, the suspension may solidly slam, followed by a launch/jump.

A 2 ton M5 with linear spring rates in the 350/315 range will need a ride height in the 14.5" range to avoid bumpstop contact. Under severe duty, the bumpstops will be contacted occasionally even with these ride heights.
 

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Discussion Starter · #17 ·
Lscman said:
Redshift's car is super low and spring rates are modest. If you review threads, the title was appropriately "slammeroni" and the ride heights were in the 12.5" to 13" range. From my experience driving various hefty cars on-track at full song, I would think it's leaning solidly against the bumpstops in every turn...if not while sitting at rest. This would feel much like high rate springs or excessive compression damping. The complex bumpstops provided in the GC kit are quite high tech as they induce a gentle, progressive "rate gain" that feels much like a progressive spring. This allows the car to handle decent under bumpstop contact. With these bumpstops, the sensation of bottoming is quite muted. It would be very difficult to feel contact under most circumstances. If you hit a speedbump or similar, the suspension may solidly slam, followed by a launch/jump.

A 2 ton M5 with linear spring rates in the 350/315 range will need a ride height in the 14.5" range to avoid bumpstop contact. Under severe duty, the bumpstops will be contacted occasionally even with these ride heights.
What is amazing is that I just got off the phone from Ground Control and the 9", #280 rear spring is the (their recommended) spring that they include with their "street" kit...I can barely keep the rear ride height at 13 7/8 with the perches at the top of the shock...

I am still waiting on Jay's opnion on what rear spring that he is going to recommend for my rear end with the #430, 7" front springs...I am only going to change these rear springs ONCE more....:crying:

Mark
 

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this makes absolutely no sense as they supplied 10 inch 425 rears with my 550# fronts

a 9 inch 280 is not the right spring -- it should be 10 inch which is a standard Eibach part
 

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stever said:
this makes absolutely no sense as they supplied 10 inch 425 rears with my 550# fronts

a 9 inch 280 is not the right spring -- it should be 10 inch which is a standard Eibach part
The root of the problem is probably related to the inital customer demand for slammer setups for E39. The #1 goal of the E39 V8 community was to slam cars. Vietsb was first on the list, doing prototyping almost a year before chunpng got his street kit. Check out roadfly pics of Vietsb's car....the tires are literally buried deep in the wheelwell like some asian showcar. This early development and customer feedback is probably what spawned the early street kits. Folks looking for real handling and disinterested in slamming are just beginning to buy kits. Hopefully the tide will turn and Jay can zero-in on springs for us.
 

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drallen said:
What is amazing is that I just got off the phone from Ground Control and the 9", #280 rear spring is the (their recommended) spring that they include with their "street" kit...I can barely keep the rear ride height at 13 7/8 with the perches at the top of the shock...

I am still waiting on Jay's opnion on what rear spring that he is going to recommend for my rear end with the #430, 7" front springs...I am only going to change these rear springs ONCE more....:crying:

Mark
Mark,

I may have missed it in another thread, but did you ever settle on what rear spring rate and free length for the rear?

Thanks,
Chuck
 
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