| Author | Message | ||
| Peter S�derlund /328 GTB -88 (Corsa)
Junior Member Username: Corsa Post Number: 217 Registered: 4-2001 |
Haven't arrived yet. The current front ones are bottoming. Happened 2-3 times. Not a big problem but will be solved with the new springs. The car is lowered a bit... Any news, Mark? Ciao Peter | ||
| Mark Eberhardt (Me_k)
Junior Member Username: Me_k Post Number: 59 Registered: 5-2002 |
Hi Peter, sorry I missed your last post. I think you�re going to like your new springs. Sunday was hard rain all day, so I didn�t go. The autocross was at an old airforce base, it is cement with poor drainage, very slick when wet. I have noticed now that the weather and roads have warmed up, the rear grip a feels better. I took it out and just plain abused it the other day and it was very well behaved. I don�t know when I�ll get another chance to autocross. I�m changing jobs and states, so I�ll be very busy the next month or so. I�d love to hear what you think when you get your new springs. | ||
| Peter S�derlund /328 GTB -88 (Corsa)
Junior Member Username: Corsa Post Number: 204 Registered: 4-2001 |
Mark, any news from your autocross event? I ordered 365F (64N/mm) and 308R (54N/mm) springs for the 328. Ciao Peter | ||
| Peter S�derlund /328 GTB -88 (Corsa)
Junior Member Username: Corsa Post Number: 201 Registered: 4-2001 |
Hi I'm about to change my springs to 354-360F (62-63N/mm) and 303-308R (53-54N/mm) on the 328 now. Anything to add before the bell rings? Ciao Peter | ||
| Peter S�derlund /328 GTB -88 (Corsa)
Junior Member Username: Corsa Post Number: 199 Registered: 4-2001 |
Hi Mark Yes I think the springs are a little bit too soft. My reasoning is that stiffer springs might reduce the overall grip but on the other hand improve feel, which is important to drive on the limit. More rebound damping will also improve feel. I could change the shims inside the shock. So what to do? I�m not sure about how stiff springs I�ll need. I�ll consider your suggestion that the best overall street/track set-up might be 350F 300R. I have stock sway bars and for the moment I�ll probably not change them even if it�s tempting� Hmm� 1� anti-sway bar front, 7/8�rear, where can I get them and how much will they cost? What�s the stock diameter for 328 (not important I can check later)? From balance point of view I was mostly referring to the F/R-setting of the shock, which is not very useful information for anyone� Nevertheless, it�s very easy to tune in over/understeer with those shocks. Ciao Peter I really had a good time. I was only 2-3 sec slower than the fastest Maranello (~1m39s). Ok. he was not an experienced racing driver (neither am I) but he frequently take the car to the track. | ||
| Mark Eberhardt (Me_k)
New member Username: Me_k Post Number: 31 Registered: 5-2002 |
Sounds like you had a good time. The info is helpful too. Those are about the springs I had last year on the konis (350f,250r). I though it was soft overall, particularly the rear. It sounds like your saying the balance seemed good, just soft? I�m happy with the balance on mine (450f,400r), but I�m thinking stiff overall. There is another autocross 6/16, so I�m going to leave these springs in until then and see how it goes. I think I will drop to 400f,350r after that and see how that feels. I�ll let you know how the autocross goes. Are you running the stock anti-sway bars? I�ve been thinking that the best overall street/track set-up might be go down to the 350f/300r with 1� anti-sway bar front, 7/8�rear. I�ve heard that before and I�m starting to they might be right. | ||
| Peter S�derlund /328 GTB -88 (Corsa)
Junior Member Username: Corsa Post Number: 198 Registered: 4-2001 |
Back from track. From start I had the road setting on the shocks 12 ClickFront 15 ClickRear. Hot tire pressure was 2.60-2.65F (38) and 2.70-2.75R (39,5). Spring rate 53F (300) and 48R (275) The feeling and response was not particularly good. It was quite sloppy during braking ad turn-in. My wife was quite disappointed and said that our Alfa GTV TS (Bilstein sport and H&R-springs) has better communication. To the second stint I changed the setting to 8 CF and 11CR (more rebound damping) and the response was much much better and the handling improved very much. It was a very confident feel during braking and turn-in and the communications was good. I�ve never had any problem at the exits. The balance was very good, quite neutral. The spring rate was definitely not to hard for hard driving on track. They can be harder to gain more control. I would like to try a little bit harder springs. It was my first time at that track with the 328 and the first time with the new shocks. I can improve my lap times a lot. For instance I braked much to early at some places. In fact the handling, feed back and communication was far better than with the 550 I tried. It was a relief to drive the 328 after the 550. Don�t misunderstand me, handling and feed back it was, the rest is another thing� Funny that I passed a bunch of Maserati biturbos including a 3200, 348s and a Maranello, that was fun. Ciao Peter | ||
| Peter S�derlund /328 GTB -88 (Corsa)
Junior Member Username: Corsa Post Number: 197 Registered: 4-2001 |
Sorry to hear that. I was going to a track day a month ago but the weather forecast said RAIN all weekend. I checked the forecast at least twice a day the whole week before. It always said rain all weekend. Finally 10 pm the evening before I cancelled it (2 hours drive) and what happened. SUNSHINE all day. Ciao Peter | ||
| Mark Eberhardt (Me_k)
New member Username: Me_k Post Number: 20 Registered: 5-2002 |
I went to the autocross, but I was the only one. Apparently they canceled it, pretty disappointing. I drove about an hour in the rain, then just as I got there the sun broke through. I need to stop trusting their web page. I don�t see anything on the schedule for a couple weeks, but I will let you know when I get it out. I�d love to hear how your track day goes, good luck. | ||
| Mark Eberhardt (Me_k)
New member Username: Me_k Post Number: 17 Registered: 5-2002 |
The numbers are probably newtons or kN per meter, so multiply by .22 to get to pounds, then dived by 39.37 to go to inches. So my 400 lb/in are 71581 N/m or 71.6kN/m. It might just be the part # too. They're calling rain AM then clear, we'll see. | ||
| Peter S�derlund /328 GTB -88 (Corsa)
Junior Member Username: Corsa Post Number: 190 Registered: 4-2001 |
I don't know the suspension travel yet. I forgot the spec at the shop. Regarding spring rate, I checked the numbers on the springs today but they didn't make any sense to me, I'll have them translated by the shop on monday. Mark, I'm very eager to get your opinion after the autocross session. I,ll go for a track day next weekend. I have a feeling that I need stiffer springs, though. Ciao Peter | ||
| Mark Eberhardt (Me_k)
New member Username: Me_k Post Number: 16 Registered: 5-2002 |
The stock shocks on my car had 5.5" travel rear and 3.25� front if I remember right. The Ohlins that I bought STJ17500 rear has a 5" stroke and the front STJ15400 has a 4" stroke. Both the konis and Ohlins have rubber snubbers on the shaft which limits the travel slightly. I had them put a big snubber on the front to knock the travel down and a small one on the rear to get as much as possible. The free length of the shocks was about right as is, although slightly shorter than stock. The 46DRs might be a little different as far as stroke and free length, Peter can probably answer that, they also sound easier to install. Anyway, the way mine are set up the wheel still has it�s full travel in front and almost full in the rear, although with the stiff springs its probably not using it all. Springs come in 25 lb/in steps so you can have basically anything you want. They take standard 2.5� ID so I bought eibachs which are $50 a pair instead of $100 for Ohlins, but there not the cool yellow. The valving in the shock can be set basically anyway you want with the external adjuster to fine tune your rebound (and compression if you go with an external reservoir). Mine came the dyno sheets so you can see exactly what they are doing where to help with the tuning. I had them start near the koni damping rates, but straighten the curve out and they seem close. I think it�s $25 each to revalve them at the shop I got the from, so changing your mind is no big deal. They are nice pieces and a lot lighter than the stock set up. If it doesn't rain Sunday I'm going to get the car to the autocross to figure out if the rear grip issue is the shocks/springs or the extra 30-40 HP I added over the winter. | ||
| Bill Sebestyen (Bill308)
Junior Member Username: Bill308 Post Number: 241 Registered: 5-2001 |
Thanks Peter and Mark for a good discussion. We just like our cars set up differently. Most racers limit their suspension travel and this works well on a smooth track, especially with wide tires. I'll post a photo of the Koni setup when I get a chance. Can the Ohlins be ordered in a configuration that retains full suspension travel? | ||
| Mark Eberhardt (Me_k)
New member Username: Me_k Post Number: 14 Registered: 5-2002 |
Peter, great description! That�s exactly how I feel about mine. I wish I had done this sooner. I looked at the Ohlins sight, I think we have all the same parts in our shocks. I think he difference is yours can be upgraded to the external reservoir with compression damping adjustment, where on mine the top of the shock is much larger giving a big internal (although not as big as the external) reservoir, but no separate compression adjustment. It was because of the large OD at the top of the shock I had to clearance the Aarm, I see why you didn�t need to cut anything. I would be very interested to know what springs you end up with. Bill, it�s a % of the total spring travel in the suspension. I think it might be important to note that there really is no such think as the �right� setup. It depends a lot on preference. Personally, I autocross the car every chance I get and go out of my way to find roads that are as unstraight as possible, so quick, clean direction and speed changes are required. Also wheel tire combinations change the way things work a lot. I run 225-40-18 tires on front and 285-35-18 on the rear, so the side walls are very low and will tolerate fairly high spring rates without making the car bobble . Also the Ohlins shocks are MUCH more linear than the Konis and will also tolerate high spring rates without allowing the wheel to bounce over harsh bumps. I think that Ferrari did the best they could with what they had, but things have changed a lot since then. I think we might be comparing apples and oranges. | ||
| Peter S�derlund /328 GTB -88 (Corsa)
Junior Member Username: Corsa Post Number: 189 Registered: 4-2001 |
Mark, try to soften the rear rebound damping to gain rear end grip. The shocks and your car will probably respond well to these adjustments. Ciao Peter | ||
| Peter S�derlund /328 GTB -88 (Corsa)
Junior Member Username: Corsa Post Number: 188 Registered: 4-2001 |
Hi all. Bill. The reason they are mounted up side down is, as GT4 Peter mentioned, to reduce the unsprung weight and access to the adjuster knob. Mark. No modifications of the A-arm were necessary. They have externally adjustable rebound low speed damping and adjustable ride height. All other damping properties are also adjustable but you have to tear them apart. The springs are 100% stiffer than the original ones. The spec of the shocks is still at the shop. I'm still evaluating springs and damping force. I think that the spring rate can be higher, though. First I didn�t have the correct ride height. It was about 10-15 mm too high both front and rear so the geometry where not correct. Now I have shorter springs to enable more ride height adjustment. I have lowered the car about 1-2� (the lower A-arm is pointing slightly slightly upwards) and have had the suspension set up done for the new ride height. I have more camber at the front for instance. I have played with the adjuster and can confirm that it is very easy to tune in the balance and response. Nevertheless, the feeling is just fantastic, I�m so happy for those dampers. They give much more control in the wheel movement, all kind of transients are gone, just a very nice feeling of good damping control. They are not hard but �strong�. It�s very difficult to explain the feeling even in Swedish. Ohlins dampers are well known for giving less tyre wear, after this first test I do now fully understand that. Maybe that�s the best way to describe the feeling. On bumpy roads they works fine but the ride is a little bit harsh. On smooth roads and at high speed the confidence is stunning. At the first road test I came in a little bit too fast into a high speed bend. The confidence for the handling I had already after 80 miles of driving was amazing, just brake a little and go thru the bend without any drama. I also met a tractor on the wrong side of the road so I have already tested high speed braking with the same result, confidence. They costed me about $2200 here in Sweden. As an option there is a canister with adjustable low-speed compression damping to put on. It�ll set me back another $1000. My previous dampers were OEM Bilstein Sport. Yes that�s right, some of the Ferraris where delivered with Bilstein instead of Koni. They do also have the rectangular Ferrari emblem engraved in them. Ciao Peter | ||
| '75 308 GT4 (Peter)
Intermediate Member Username: Peter Post Number: 1860 Registered: 12-2000 |
I'm guessing (marginal) unsprung weight(?). Although this isn't uncommon. Most motorcycle-rear shocks and the majority of off-road vehicles (BAJA Buggies) have this mounting arrangement. | ||
| Bill Sebestyen (Bill308)
Junior Member Username: Bill308 Post Number: 239 Registered: 5-2001 |
Peter, I was looking at your photos and noticed your shock assemblies appear to be mounted up-side-down. I've never seen a shock mounted this way. Can you tell me what the benefits are? | ||
| Bill Sebestyen (Bill308)
Junior Member Username: Bill308 Post Number: 238 Registered: 5-2001 |
Mark, I guess I don't understand your philosophy, nor do I understand your statement "the fronts have about 8% the rears 5%". These are percentages of what exactly? Your're basically doubling the spring rates. Do you plan to use the car on the road or are you seting it up for the track? I still believe in the Colin Chapman (ex Lotus) philosophy of modest spring rates, good damping, and generous suspension travel. This philosophy makes the suspension do the work rather than the chassis, especially for northeast style roads which tend to be less than table top smooth. When I did my Koni setup, one of my design criteria was to retain full suspension travel and stock bushings for compliancy. 308's are generally considered one of the better handling cars of all time so I'd be hesitant in deviating too much from the basic design unless this car is intended for a very special purpose. | ||
| Mark Eberhardt (Me_k)
New member Username: Me_k Post Number: 13 Registered: 5-2002 |
Well, your right that the front is much lighter than the rear, but the motion ratios are also much different. Plus 50 lb/in the front is about right to get good balance. Generally for aggressive driving, I like to see a car sag 40-50% of designed travel and spring preload of about 10% of total spring travel usually get you close. with this combination the fronts have about 8% the rears 5%, so it is probably a touch on the firm side, particularly the rear. Those are just starting points though and I was interested in what other were trying. | ||
| Bill Sebestyen (Bill308)
Junior Member Username: Bill308 Post Number: 237 Registered: 5-2001 |
Mark, I not sure what you're trying to accomplish with your chosen spring rates, but they seem overly stiff and unbalanced. I've heard of track people using 300-350 lb/in at the rear, which may work well on a smooth track, but 400 lb/in seems a bit much for the road. 450 lb/in at the front seems much to much. The front of a 308 is lighter than the rear, so it seems it should be less than the rears no matter what. I converted the rears of my 308 to Koni 8211's and specified a spring rate of 200 lb/in, compared to the factory specification of 185 lbf/in (3.33 kg/mm) in the GT-4 Workshop manual. I'm leaving the fronts stock at this time. This same manual specifies 175 lbf/inch for the fronts. Values for the GTS are not specified in my OM so they are either the same or a little stiffer because the GTS is a little heavier. In any event, I think you would be well advised to change your spring rates. | ||
| Mark Eberhardt (Me_k)
New member Username: Me_k Post Number: 11 Registered: 5-2002 |
The externally adjustable STJs with the springs and custom valved were $2200 for the set. What springs did you go with? I may have gone a little stiff with 450 lb/in front and 400 lb/in rear. It doesn't roll in the corners any more, but it seems like the grip in the rear coming out of the corner or leaving a light isn't what it should be. I'm going to try softening the shock adj, but I'm questioning the springs. Thoughts? | ||
| Ric Rainbolt (Ricrain)
Junior Member Username: Ricrain Post Number: 115 Registered: 2-2002 |
How much were these? | ||
| Mark Eberhardt (Me_k)
New member Username: Me_k Post Number: 10 Registered: 5-2002 |
Nice! I just put Ohlins STJs on my 308 and love them. The 46DRs should be even better. I had to do some clearancing on the Aarm though, it looks like you will too. | ||
| Peter S�derlund /328 GTB -88 (Corsa)
Junior Member Username: Corsa Post Number: 187 Registered: 4-2001 |
More pix at: Before http://www.stotdamparexperten.nu/fore.htm after http://www.stotdamparexperten.nu/efter.htm And http://www.ohlins.se/ Check 46DR racing    Ciao Peter |