[Brian A]

...Traditionally I've hated the idea of big sway bars because I've felt that by linking the 2 sides together they cause more loss of compliance in the suspension than upping the spring rate would and can unsettle the chassis over 1 wheel type bumps. Lately though ...

FWIW, to address body roll on my two BMWs I have installed stiffer, adjustable swaybars and run soft-ish springs.

On the road, I really like the result although I still get body roll on the track; it's not a perfect solution. (I also had to have reinforcemnent tabs welded onto the rear subframe after I cracked off the stock swaybar attachment points.)

A big benefit is that my wife still agrees to ride in my car occasionally.

 

[mk e]

FWIW, to address body roll on my two BMWs I have installed stiffer, adjustable swaybars and run soft-ish springs.

On the road, I really like the result although I still get body roll on the track; it's not a perfect solution. (I also had to have reinforcemnent tabs welded onto the rear subframe after I cracked off the stock swaybar attachment points.)

A big benefit is that my wife still agrees to ride in my car occasionally.

I've found the ride quality is more about the shock settings than anything else. For street use I keep mine set on the soft side which yields a softer than stock ride even with the much stiffer springs. This setting does lead to the car felling loose much above 100 mph and very loose above 120, but again not worse than stock and there's nowhere I can drive anywhere near that fast on the street without putting others in danger anyway. This setup has worked really well very for autocross use so I'm happy with the compromise.

Then about 6 or 8 clicks on the rebound adjusters and it's ready for..... shall we say more spirited use

 

[bretm]

I'm paraphrasing old emails between me and Mark - he's running Ohlins STJ's with a 4" stroke up front and a 6" stroke in the rear, coupled with 10" springs in front and 12" springs in the rear. The rear is slightly too long and at full droop the spring isn't long enough. So, I've started researching with his shocks in mind.

My starting point is that I'd like digressive piston, adjustable compression and rebound, 46mm aluminum body, preferably with an integrated reservoir.

Ohlins looks to have discontinued the STJ series, which is a bummer as I was leaning towards them. That said, RE Suspension still has them listed which probably warrants a call.
Racing - Öhlins
Racing Shocks and Suspension at RE Suspension

My next thought was to look at Koni shocks, but there seems to be next to no support for them online, so far as I can tell. I had trouble even find a shop that sells their high end products, in particular the 3012 series. I didn't find information about them being digressive, so that would require a call.
Koni Racing - ITT

And that lead me to Bilstein shocks. They have a mid-line series called the ASN that might fit the bill really well (available in 4" and 6", digressive, 46mm alum body). They're cheaper than the Ohlins and yet are fully rebuildable. Page 16 of the pdf listed here:
http://cart.bilsteinus.com/pdfs/motorsports.pdf
They don't break the bank completely, but require an optional adjustable shaft. I'd have to check if they can also accept the dual adjustable shaft that Bilstein makes (also in the pdf above). That would probably put them close to the Ohlins in regards to price.
Racing Shocks and Suspension at RE Suspension



Mark, would you happen to have the collapsed and extended length of your STJs?

 

[bretm]

I came across these Penske double-adjustable 7500 shocks tonight. When I looked earlier today I didn't click on the latest products tab, so I only saw the non-adjustable and single-adjustable 7500s. They don't come in 4" stroke, but maybe the 5" version would work up front and then use a 6" at the rear like Mark's STJs.
7500 Double Adjustable Series
http://www.penskeshocks.com/files/7500 SERIES GENERAL 2010.pdf

Hmmm... at this point I'm thinking it's either these Penske 7500s or Ohlins STJs (if they're still available). I lean a bit towards the Ohlins as I have a couple buddies with bikes and those have always been the "it" shocks to buy, plus it would be convenient if Mark and I are running identical setups. The more data the better.

 

[mk e]

Mark, would you happen to have the collapsed and extended length of your STJs?

In front I have stj15400 which is 15 extended, 4" stoke giving 11 collapsed
in the rear I have stj17500 which is 17" extended, 5" stroke giving 12" collapsed

somewhere I have the graph and other setup info on them. attached is the manual

 

[bretm]

I was planning on emailing the shock companies over the weekend, but it looks like calling is the way to go. So, my to do list tomorrow is:

1. Call RE Suspension and ask them if the Ohlins STJ is still being made.
STJ 15400
STJ 17500
704-664-2277 phone
Racing Shocks and Suspension at RE Suspension

2. Call Penske and ask them:
- if they can make 4" stroke 7500 Double-Adjustable
- what is the extended and collapsed length of their 5" version of the 7500DA
- if they have the dimensional diagram for the 5" 7500DA
Phone: (610) 375-6180
7500 Double Adjustable Series

 

[reggazz312t]

Hi Brian,

an M BMW is like driving a Ferrari sitting on a child's high chair,,LOL,no offense,just trying to be funny.,,It takes me a year to come up w/a weeks coin that these heavyweight's direct to their fantastic projects.OnWard Thru The Fog

 

[bretm]

an M BMW is like driving a Ferrari sitting on a child's high chair,,LOL,no offense,just trying to be funny.,,It takes me a year to come up w/a weeks coin that these heavyweight's direct to their fantastic projects.OnWard Thru The Fog

Lol about the BMW. They make simply amazing cars, but even my E46 M3 (which is more focused than the current E92) does feel somewhat detached compared to the 308. That says quite a bit to me because the M3 is just about the best daily driver a guy could ever wish for. A couple gents have swapped E60 M5 V10s into their E46 M3s... that must be a monster, but would require a lot more rear tire than the 255s on the car from the factory.

You can do alright with brake, wheels, and suspension swaps on the 308 if you start with a QV. The stock 16" mags go for decent money, as do the rear calipers. I think there's even a small second hand market for the Konis if in good shape and maybe the rotors. What I'm getting at is that most of the parts going onto my car are actually a good deal cheaper than those coming off, which helps offset some of the pain of spending ludicrous amounts of money on the Penskes or Ohlins.

 

[The Dark Side of Will]

My current thinking is that if the car's not bottoming out them the springs are probably about right. It it's not bobbling anywhere then the shocks are about right so the excess roll I've got means the sway bars are too soft.

Presence of body roll doesn't mean lack of speed.
Presence of speed does not require lack of body roll.

It depends on how good Ferrari's suspension design is. I haven't analyzed the geometry personally. Have you, Mark?

If the geometry can make good use of the tire throughout the whole range of body roll the chassis sees, then the springs only have to be stiff enough to keep the suspension off the bump stops. This means that spring rate should be a function of how sticky the tires are, and acceptable body roll is a function of suspension travel.

The chassis' reactions at high speed (and ride quality) are more a function of damper settings, as you have noted.

 

[mk e]

Presence of body roll doesn't mean lack of speed.
Presence of speed does not require lack of body roll.

It depends on how good Ferrari's suspension design is. I haven't analyzed the geometry personally. Have you, Mark?

If the geometry can make good use of the tire throughout the whole range of body roll the chassis sees, then the springs only have to be stiff enough to keep the suspension off the bump stops. This means that spring rate should be a function of how sticky the tires are, and acceptable body roll is a function of suspension travel.

The chassis' reactions at high speed (and ride quality) are more a function of damper settings, as you have noted.

You're definitely right that roll by itself is not necessarily a problem.

I have not done a full and proper analysis of the suspension geometry because re-designing it was not on my to-do list and I'd have to live with what I have.

What I have spent a bit or time looking at is when the car hits the bump stops....and it's early and often. My first autocross outing with stock suspension/wheels/tires the car spent the entire event with the outer 2 corners on the bumpstops.... and that was with crap tires. out on the road it was not problem to bottom out the suspension over normal Northeast pavement ripples. Just worthless.

Now I have it working pretty well at normal speeds on the street but at the autocross it was still spending a good amount of time with the front outer wheel in particular on the bump stop so I'm thinking it still needs a bit more front roll stiffness. I'm also not happy with the grip coming out of the turns but that could be a lack of weight transfer due to the rear springs or from the roll stiffness imbalance I think so I'm not exactly sure...but I think my springs are a bit out of balance front/rear ratio wise.

Looking at the common setups,
300/250 = 1.2
350/300 = 1.166
400/350 = 1.14
450/400 is 1.125

so with 450/400 I've added quite a bit more rear roll stiffness and I'm thinking 450/375 or 475/400 or even 500/400 would be better combinations. I'm leading toward the 450/375 option then adding a bit more sway bar to keep it off the bumpstops.

 

[bretm]

So, I called RE Suspension this morning and Ohlins is still making the STJ. It sounds like they entertained the idea of discontinuing it, but then decided to keep producing them due to demand. The gent on the phone was 99% sure Ohlins still makes the 4" version, but if they don't, a 5" shock body can be machined down for $35 per shock.

I found the tech specs on the Penske 7500 series:
4" stroke = 14" extended length
5" stroke = 16" extended length

Mark, from your experience would those extended lengths work alright? They're approx. an inch shorter vs. the Ohlins.

Second question, do you remember the ID of the spherical bearing at the top and bottom of the Ohlins? The Penskes are 1/2" if I'm reading their chart right. If the 308 has 12mm bolts holding the OEM shocks in, that would work alright as the hole could be opened up in the chassis/upright.

Third question, do you remember what ID springs you are running? Looks like 2.5" ID is the most common for 10" and 12" springs.

_____________________


These are what I'm deciding between at this point. Price includes springs.

1. Ohlins STJ $2,800
STJ 15400
STJ 17500
Racing Shocks and Suspension at RE Suspension

2. Penske 7500 Double Adjustable $2,340
4" custom stroke
5" stroke
Racing Shocks and Suspension at RE Suspension

3. Penske 7500 Single Adjustable $1,920
4" custom stroke (not sure if this is possible)
5" stroke
Racing Shocks and Suspension at RE Suspension

 

[mk e]

I found the tech specs on the Penske 7500 series:
4" stroke = 14" extended length
5" stroke = 16" extended length

Mark, from your experience would those extended lengths work alright? They're approx. an inch shorter vs. the Ohlins.

I think they are too short, particularly the front one. You should be able to pick the next longer though and have a spacer installed inside to limit the extension.

Second question, do you remember the ID of the spherical bearing at the top and bottom of the Ohlins? The Penskes are 1/2" if I'm reading their chart right. If the 308 has 12mm bolts holding the OEM shocks in, that would work alright as the hole could be opened up in the chassis/upright.

The ones I got are 1/2". I made stepped spacers that slip into the shock to bush it down to M12 and also correct the width.

Third question, do you remember what ID springs you are running? Looks like 2.5" ID is the most common for 10" and 12" springs.

I am using 2.5".

My STJs are a single adjuster. It moves mainly rebound but also does affect compression. Its about a 90/10 split which actually works pretty well it matches the actual damping split so the 1 adjuster make the shock stiffer or softer without buggering up ratios. Remember too that with 1 or 2 way adjustable shocks it's the low speed damping (the suspension travel rate, not the car speed) that you're adjusting. The high speed damping is set by the internal valving alone (unless to spring for the 4 way adjustable versions) so you need to send the shocks back to have that changed.

 

[The Dark Side of Will]

I'm also not happy with the grip coming out of the turns but that could be a lack of weight transfer due to the rear springs or from the roll stiffness imbalance I think so I'm not exactly sure...but I think my springs are a bit out of balance front/rear ratio wise.

Looking at the common setups,
300/250 = 1.2
350/300 = 1.166
400/350 = 1.14
450/400 is 1.125

so with 450/400 I've added quite a bit more rear roll stiffness and I'm thinking 450/375 or 475/400 or even 500/400 would be better combinations. I'm leading toward the 450/375 option then adding a bit more sway bar to keep it off the bumpstops.

Ditto... if it's on the bump stops, it's not working as designed, so the first step is to get it working as designed.

The rear shocks move with the hub carrier, so the motion ratio is (very close to) 1.0. This means that the wheel rate is very close to the spring rate.

What's the motion ratio on the front suspension?
(Not that I need to tell you, but motion ratio is the square of mechanical advantage)
Comparing the wheel rates for different spring rates is a better way to go than looking only at spring rates, or sticking with a fixed split like +50 in the front.

My STJs are a single adjuster. It moves mainly rebound but also does affect compression. Its about a 90/10 split which actually works pretty well it matches the actual damping split so the 1 adjuster make the shock stiffer or softer without buggering up ratios. Remember too that with 1 or 2 way adjustable shocks it's the low speed damping (the suspension travel rate, not the car speed) that you're adjusting. The high speed damping is set by the internal valving alone (unless to spring for the 4 way adjustable versions) so you need to send the shocks back to have that changed.

MagneShocks Home

Magneto-Rheological shocks for hot-rod projects!
EVERY point on the damping curve can be adjusted! :wink2:

Only about $7600 for the whole shebang: http://www.magneshocks.com/Documents/3rdGenPRICEListStreet-Rods.pdf

 

[mk e]

.

What's the motion ratio on the front suspension?

Remembering back I think
Front = 6.0/3.5
Rear = 6.0/5.5

I think.

But obviously there is more to it than just that as the springs also affect the f/r weight transfer and roll stiffness. I think the ideal f/r ratio is around the 1.8 to 1.2 point....but that's fro the way I drive so.......

 

[mk e]

These are what I'm deciding between at this point. Price includes springs.

1. Ohlins STJ $2,800
STJ 15400
STJ 17500
Racing Shocks and Suspension at RE Suspension

2. Penske 7500 Double Adjustable $2,340
4" custom stroke
5" stroke
Racing Shocks and Suspension at RE Suspension

3. Penske 7500 Single Adjustable $1,920
4" custom stroke (not sure if this is possible)
5" stroke
Racing Shocks and Suspension at RE Suspension

Forgot to comment on this part.

I think you'll be happy with any of the options on you list. I got myself talked into the STJ over the penske and other options at the time based on 2 things.

1) my motorcycle racing experience and just how well the ohlins worked for me.

2) the reservoir on the STJ is MUCH larger than other non-external options and in a gas shock that is important. Compressed gas is a spring and when the shock is compressed, like the outside shock are when you're cornering, the effective spring rate can go up quite a bit causing a loss of compliance which causes a loss of grip on non-smooth surfaces like roads. The down side is the built in reservoir is big and I had to clearance the things to fit it.

How significant either of these points are I'm not so sure but it is what drove my final decision....but almost anything you buy will be a big improvement over the stock konis which absolutely suck.

 

[reggazz312t]

Koni junk

This thread is a great education for me,,,,,why did LD go back to koni? ,,What do you think about putting 350-300 springs on good stock koni,,,47407qv wants upgrade but hes 67 and has limited funds,,as I,,Im 60,,LOL,,thanks mk e,Will and especially Brett

 

[Brian A]

...lack of weight transfer due to the rear springs or from the roll stiffness imbalance ... I'm leading toward the 450/375 option then adding a bit more sway bar to keep it off the bumpstops.

Are progressive springs an option? Usually swaybars are just used for tweaking understeer/oversteer after the main springs rates are dialed in.

 

[dino246gts]

The 360 wheels are aluminum bits:
18" x 7.5" front 215/45 R18
18" x 10.0" rear 275/40 R18
I picked them up back in March of last year, as you can see in post #523 of the other thread.
http://www.ferrarilife.com/forums/p.../12561-308-engine-rebuild_efi-pistons-27.html

Some guys are running four fronts because the rears are a pain to fit, but I'll need all the rear tire I can get once the supercharger is installed. So, I'm probably going to have to follow in Mark's footsteps and move the rear shock mount inwards for clearance.

Anywho, to keep the rolling circumference close to what the 308 has originally, I'm leaning towards Michelin Pilot Super Sports:
225/40 R18 front
275/35 R18 rear
Michelin*Pilot Super Sport

:thumbsup::thumbsup:

 

[bretm]

2) ...The down side is the built in reservoir is big and I had to clearance the things to fit it...

What'd you have to clearance to get the reservoir to fit? The frame rail by where the shock mounts at the top?

I mulled it over a bit last night and I'm leaning towards the Ohlins for three reasons:
1. They're no doubt the best out of my choices. Largest reservoir, as Mark pointed out, etc.
2. Mark's running the STJs successfully so there aren't any unknown fitment issues that I'd be getting into.
3. I'm not a shock engineer and I didn't stay at a Holiday Inn last night so I'm not going to pretend to be one. Double-adjustable Penskes are cool, but ultimately I'd like to drive my car more than tune it and the single adjustment on the Ohlins is surely enough to keep me occupied.

I'll have to mull the numbers over a bit more as it is a big outlay of dinero, but ultimately I'm only going to buy shocks once. Spending a bit more is sometimes worth it in a case like this.

 

[bretm]

By the way, thanks for all the continued input guys! It's a pretty cool discussion that we have going on in here.

:thumbsup: