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post #1 of 17 Old 18th October 2018, 08:14 PM Thread Starter
Marquis Rex
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E39 M5 Spring Or Wheel Rates

First a little introduction:
I'm an Automotive Engineer whos worked for a few OEMs. Including Jaguar and Aston during the 'PAG' era.
I'm a huge fan of vintage BMWs, and own a Euro spec E24 M635CSi and my first car, an E21 323i.
In the future I may get a beaten up E46 M3 as a track rat.


But anyway, for this post, I've always admired the E39 M5. We used it as a benchmark while developing cars I've been involved in.
My memories of the ride and handling compromise over UK roads were remarkable. Recently I drove one again, over the terrible roads up here in the Midwest and I was very impressed. The car in question had had most of the suspension components renewed. The ride was great but also the body control.


Background/fundamentals


My plan is to get the same body control and ride compromise on my Jaguar X308 XJR.
Before anyone patronises me, I can preface this by saying I've looked into this very deeply and it is possible.
BMWs- even the older ones- put a lot of effort into certain vehicle dynamics fundamentals- they look at the yaw inertia relative to the centre of gravity to give the handling characteristics we're all so fond of. Typically their dynamic index (a term that relates the yaw inertia to the centre of gravity) is close to 1- this is the case for an old BMW 2002, An E30 BMW M3 and an E46 M3 etc. By comparison my 1970 Challenger has a D.I of about 1.28!
Fortunately for me- The X308 chassis Jaguar has a Dyn. In in line with BMWs- at around 1 with 52% front weight bias. Its torsional rigidity is about 13,000 nm/deg vs the E39 M5 at 16,000. Its just that Jaguar chose to market the X308 to a different clientele


So this should all be possible.


I need to know either the spring rates or the wheel rates of a STOCK OEM BMW E39 M5.
I tried to measure them with a vibration app on my phone during a test drive and that didn't work. I did a search online and I only came across these two threads:


http://www.m3post.com/forums/showthread.php?t=170966


https://www.m5board.com/vbulletin/e39-m5-e52-z8-discussion/143390-oem-e39-m5-suspension-spring-rates.html


If this doesn't work, I may even beg/borrow or steal OEM style springs from an M5 and have them measured.
Is anyone selling or willing to lend me a front and rear spring in the Wisconsin/Minnesota area?


Seeing as someone from here supercharged a BMW M60 V8 using an intercooler/supercharger pack from a Jag and I helped, I think its time to cash in the favour!


Thanks!

2000 MY Jaguar XJR
1972 Jaguar XJ6 series 1
1970 Jaguar E-type OTS
2007 Cadillac Escalade
2003 MY Dodge Ram 5.7 Hemi
2005 Dodge Ram 2500 Cummins
1995 Porsche 911 Turbo (993)
1982 BMW E21 323i
1970 Dodge Challenger 440 cu in R/T
2006 Aston Martin V8 Vantage
1985 BMW E24 M635CSi
1964 MCI MC5 Greyhound Bus-RV conversion
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post #2 of 17 Old 18th October 2018, 08:25 PM
gsfent
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Quote:
Originally Posted by Marquis Rex View Post
First a little introduction:
I'm an Automotive Engineer whos worked for a few OEMs. Including Jaguar and Aston during the 'PAG' era.
I'm a huge fan of vintage BMWs, and own a Euro spec E24 M635CSi and my first car, an E21 323i.
In the future I may get a beaten up E46 M3 as a track rat.


But anyway, for this post, I've always admired the E39 M5. We used it as a benchmark while developing cars I've been involved in.
My memories of the ride and handling compromise over UK roads were remarkable. Recently I drove one again, over the terrible roads up here in the Midwest and I was very impressed. The car in question had had most of the suspension components renewed. The ride was great but also the body control.


Background/fundamentals


My plan is to get the same body control and ride compromise on my Jaguar X308 XJR.
Before anyone patronises me, I can preface this by saying I've looked into this very deeply and it is possible.
BMWs- even the older ones- put a lot of effort into certain vehicle dynamics fundamentals- they look at the yaw inertia relative to the centre of gravity to give the handling characteristics we're all so fond of. Typically their dynamic index (a term that relates the yaw inertia to the centre of gravity) is close to 1- this is the case for an old BMW 2002, An E30 BMW M3 and an E46 M3 etc. By comparison my 1970 Challenger has a D.I of about 1.28!
Fortunately for me- The X308 chassis Jaguar has a Dyn. In in line with BMWs- at around 1 with 52% front weight bias. Its torsional rigidity is about 13,000 nm/deg vs the E39 M5 at 16,000. Its just that Jaguar chose to market the X308 to a different clientele


So this should all be possible.


I need to know either the spring rates or the wheel rates of a STOCK OEM BMW E39 M5.
I tried to measure them with a vibration app on my phone during a test drive and that didn't work. I did a search online and I only came across these two threads:


http://www.m3post.com/forums/showthread.php?t=170966


https://www.m5board.com/vbulletin/e39-m5-e52-z8-discussion/143390-oem-e39-m5-suspension-spring-rates.html


If this doesn't work, I may even beg/borrow or steal OEM style springs from an M5 and have them measured.
Is anyone selling or willing to lend me a front and rear spring in the Wisconsin/Minnesota area?


Seeing as someone from here supercharged a BMW M60 V8 using an intercooler/supercharger pack from a Jag and I helped, I think its time to cash in the favour!



Thanks!
Well hard to argue with your taste in cars!!


I don't have the spring rates, but there have been discussions over the years about that, mostly in regards to tracking our (relatively) heavy cars. I have a Dinan setup (springs and Koni's to Dinan spec) and I would encourage you to see if you can get the Dinan spring rates. Incredibly good, even better than the original BMW spec. Next to my old MB W124, best riding car I have ever owned.

I am GUESSING we have something like 300-350 front and maybe 200-250 rear stock. For track work, probably want something more like 450/350 or even a little higher in front. But there are folks on here who know without having to searching through old discussions.

I found this after a quick search:

https://www.m5board.com/vbulletin/e3...uspension.html



Regards
Jerry

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Dinan Stage 3 suspension, SS jet coated headers, ESS SC kit w/ 1 range colder NGK's, 92mm pulley, 440 Big Greens, TTFS alpha N tune for meth, RK plenum plates, SBC Endurance Stage 3 Kevlar performance clutch setup, "Jed" lightened DMFW, open brake ducts, TEC cupholder, U.S.(Euro style) tilt/slide armrest, 6k HID fogs, Umnitza bi-xenon flamethrowers w/6k super white low beams, rear fogs, V1/Stealth1, dual head LI, 2.65 diff w/40% lockup/2x dynamic, compact spare, Euro trailer hitch, Mocal oil cooler, ACS type rear spoiler, Rogue custom SSK and tranny mounts, ST 355 BBK (fronts), BP sway bar brackets, Bluetooth retrofit, Speedhut boost gauge (20 psi), Dinan TB's and VS, KB BAP, Howerton/HFS-3 Aquamist WI trunk setup (50/50), with 2nd gauge in rear view mirror, aftermarket trunk mounted sound system integrated into stock unit (amps and crossovers and sub and speakers).......

Last edited by gsfent; 18th October 2018 at 08:35 PM.
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post #3 of 17 Old 18th October 2018, 09:20 PM Thread Starter
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Thank you Jerry. Although Im interested in OEM values , DINAN or similar gives me a range of values to bookend for the car.

2000 MY Jaguar XJR
1972 Jaguar XJ6 series 1
1970 Jaguar E-type OTS
2007 Cadillac Escalade
2003 MY Dodge Ram 5.7 Hemi
2005 Dodge Ram 2500 Cummins
1995 Porsche 911 Turbo (993)
1982 BMW E21 323i
1970 Dodge Challenger 440 cu in R/T
2006 Aston Martin V8 Vantage
1985 BMW E24 M635CSi
1964 MCI MC5 Greyhound Bus-RV conversion
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post #4 of 17 Old 18th October 2018, 11:42 PM Thread Starter
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Quote:
Originally Posted by gsfent View Post
Well hard to argue with your taste in cars!!


I don't have the spring rates, but there have been discussions over the years about that, mostly in regards to tracking our (relatively) heavy cars. I have a Dinan setup (springs and Koni's to Dinan spec) and I would encourage you to see if you can get the Dinan spring rates. Incredibly good, even better than the original BMW spec. Next to my old MB W124, best riding car I have ever owned.

I am GUESSING we have something like 300-350 front and maybe 200-250 rear stock. For track work, probably want something more like 450/350 or even a little higher in front. But there are folks on here who know without having to searching through old discussions.

I found this after a quick search:

https://www.m5board.com/vbulletin/e3...uspension.html



Regards
Jerry

That helps.
I just found this from the same guy


https://www.m5board.com/vbulletin/e3...discovery.html


That LSC guy seems to have vanished though.


I tried calculating my own spring rates of my XJR via the wire/coil diameter and got a ridiculous number for the front (470 lbs spring rate leading to 300 wheel rate which is 1.76 hz nat freq which is ridiculous- and higher than the E39 M5 front - which I don't believe!).


Then I used the deflection method and got a bit more believable results. 200 lbs wheel rates front and rear for the M5 are figures I saw banded about on another forum. But that again was calculated.


Im thinking I need to get hold of an actual spring and get it measured and compare it to measurements of my Jag springs!

2000 MY Jaguar XJR
1972 Jaguar XJ6 series 1
1970 Jaguar E-type OTS
2007 Cadillac Escalade
2003 MY Dodge Ram 5.7 Hemi
2005 Dodge Ram 2500 Cummins
1995 Porsche 911 Turbo (993)
1982 BMW E21 323i
1970 Dodge Challenger 440 cu in R/T
2006 Aston Martin V8 Vantage
1985 BMW E24 M635CSi
1964 MCI MC5 Greyhound Bus-RV conversion
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post #5 of 17 Old 19th October 2018, 12:19 PM
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The stock rear springs are a progressive wind, so it's not so easy to state a single rate for them. From looking at them, they likely can almost be considered two rates depending on deflection however. 40 years ago in undergrad mechanical engineering lab, we had a session on measuring spring rates, and the lab had a very simple device that secured the spring and allowed it to be compressed while showing load vs deflection. I think we measured the front springs off a Chevy Impala. I've always wanted to have one of those around ever since.

I didn't explore the links, but I'm pretty sure the motion ratios for the E39 M5 are here somewhere on the board.

Regards,
Chuck

Current stable:

2019 M2 Competition 6MT LBB, slicktop
2011.5 M3 sedan 6MT Silverstone, slicktop: Dinan front swaybar, Eibach rear swaybar, pins-out-max-camber-up-front, Dinan exhaust, Michelin PS4S, Apex EC-7 9.5/10.5x19
2007 328i wagon Silver/gray: Eibach 28mm front swaybar, E93 M3 rear swaybar, 219M M3 wheels, Michelin PSAS3+
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Last edited by CSBM5; 19th October 2018 at 12:20 PM.
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post #6 of 17 Old 19th October 2018, 03:18 PM
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I reached out to Dinan several years ago and they provided spring rates from a 540i M-sport as well as their springs

540i M-sport spring rates: 167/197

Dinan Spring Rates: 197/250

As mentioned above, the factory rears are progressive whereas the Dinan are linear rate.

Best of luck!

- Darrell

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post #7 of 17 Old 19th October 2018, 03:40 PM
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Seems like the spring rates are almost irrelevant-- what you actually need are the frequencies, front and rear.

... unless the jag has the exact same motion ratios and is the same weight as the M5, as well!

I have no idea what the M5's frequencies are, but I'd bet the rear is ~20% stiffer than the front (not spring rates-- frequencies).

Last edited by Obioban; 19th October 2018 at 03:45 PM.
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post #8 of 17 Old 19th October 2018, 04:41 PM Thread Starter
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Quote:
Originally Posted by Obioban View Post
Seems like the spring rates are almost irrelevant-- what you actually need are the frequencies, front and rear.

... unless the jag has the exact same motion ratios and is the same weight as the M5, as well!

I have no idea what the M5's frequencies are, but I'd bet the rear is ~20% stiffer than the front (not spring rates-- frequencies).
They're not irrelevant when you have a spreadsheet - that has all the data, thank you. That's why I specified wheel rate OR spring rate.


Judging by values of the E34 and E46 and then another thread I got the E39 motion ratios down as 0.9 front and 0.83 rear. This wasn't measured directly by me. This compares to 0.818 and 0.774 for the Jag but factor in a heavily angled spring on the Jag of about 70 degrees on the rear. This was measured directly by me.


The frequencies for the E46 M3 stock are 1.47 rear and 1.31 front, where as for the E39 M5 with PSS9 I'm getting 2.11 front and 1.47 Hz rear.
I prefer to design to the 'flat ride theory' tuned to motorway speed-which BMW often doesn't. I wont be tracking my car really so I'd really be happy with stock OEM M5 style wheel rates/frequencies.


I agree progressive rate makes it harder to quote figures- but not really as you can quote the ranges.


Although I don't have the OEM M5 rates yet- zeroing in on numbers for my XJR now-(but am open to changing this) from all Im absorbing- F: 250 lbs spring-300 lbs (progressive) or wheel rates 1.31 to 1.44 Hz and then rear: 317-400 lbs (progressive spring rates) or wheel freq of 1.47-1.65 Hz

2000 MY Jaguar XJR
1972 Jaguar XJ6 series 1
1970 Jaguar E-type OTS
2007 Cadillac Escalade
2003 MY Dodge Ram 5.7 Hemi
2005 Dodge Ram 2500 Cummins
1995 Porsche 911 Turbo (993)
1982 BMW E21 323i
1970 Dodge Challenger 440 cu in R/T
2006 Aston Martin V8 Vantage
1985 BMW E24 M635CSi
1964 MCI MC5 Greyhound Bus-RV conversion

Last edited by Marquis Rex; 19th October 2018 at 04:49 PM.
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post #9 of 17 Old 19th October 2018, 04:49 PM
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Quote:
Originally Posted by Marquis Rex View Post
They're not irrelevant when you have a spreadsheet - that has all the data, thank you. That's why I specified wheel rate OR spring rate.


Judging by values of the E34 and E46 and then another thread I got the E39 motion ratios down as 0.9 front and 0.83 rear. This wasn't measured directly by me. This compares to 0.818 and 0.774 for the Jag but factor in a heavily angled spring on the Jag of about 70 degrees on the rear. This was measured directly by me.


The frequencies for the E46 M3 stock are 1.47 rear and 1.31 front, where as for the E39 M5 with PSS9 I'm getting 2.11 front and 1.47 Hz rear.
I prefer to design to the 'flat ride theory' tuned to motorway speed-which BMW often doesn't. I wont be tracking my car really so I'd really be happy with stock OEM M5 style spring rates.


I agree progressive rate makes it harder to quote figures- but not really as you can quote the ranges.


Although I don't have the OEM M5 rates yet- zeroing in on numbers for my XJR now-(but am open to changing this) from all Im absorbing- F: 250 lbs spring-300 lbs (progressive) or wheel rates 1.31 to 1.44 Hz and then rear: 317-400 lbs (progressive spring rates) or wheel freq of 1.47-1.65 Hz
I don't believe your e46 M3 stock frequencies are correct, and .9 isn't the e46 M3 front motion ratio (not sure if you were trying to say it was or not, just clarifying). The e46 m3 suspension geometry and spring location are completely different than the e39s, so I wouldn't use that as any sort of basis for the e39's motion ratios (again, if you were).

BMW has ~20% flat ride on pretty much every car they make. I don't know for a fact that this holds true on the M5, as I've never dug into, but it certainly feels like it does.

Last edited by Obioban; 19th October 2018 at 04:51 PM.
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post #10 of 17 Old 19th October 2018, 04:53 PM Thread Starter
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Quote:
Originally Posted by Obioban View Post
I don't believe your e46 M3 stock frequencies are correct, and .9 isn't the e46 M3 front motion ratio (not sure if you were trying to say it was or not, just clarifying). The e46 m3 suspension geometry and spring location are completely different than the e39s, so I wouldn't use that as any sort of basis for the e39's motion ratios (again, if you were).
I didn't quote the E46 motion ratios.


The values for the E39 I got from a thread elsewhere.


Yes, I'm aware that the E46 layout is very different to the E39.


Feel free to nit pick some more by all means, but what would really help would be OEM E39 M5 spring OR wheel rates (yes Im aware that theyre not the same thing and that wheel frequencies are what really counts- thank you!).

2000 MY Jaguar XJR
1972 Jaguar XJ6 series 1
1970 Jaguar E-type OTS
2007 Cadillac Escalade
2003 MY Dodge Ram 5.7 Hemi
2005 Dodge Ram 2500 Cummins
1995 Porsche 911 Turbo (993)
1982 BMW E21 323i
1970 Dodge Challenger 440 cu in R/T
2006 Aston Martin V8 Vantage
1985 BMW E24 M635CSi
1964 MCI MC5 Greyhound Bus-RV conversion
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