Spring rate for 308 road use only?

I'm in the same market. I'd like to know a good recommended spring rate, and a good source for shocks/coil-over springs. I hear Varishocks aare better than Summit QA-1s....

Greg

 

See the thread at http://www.ferrarichat.com/forum/showthread.php?p=134616065

I personally think that 350# fronts for street only might be mismatched as a little heavy for the 250# rears... I'd recommend 300# fronts, especially for street only. I'm using the 300#/250# combo for both street and track, but I'll firm up the adjustable shocks for track days.

 

i second this.

 

Regarding spring rates, I've noticed almost everyone suggesting higher rate fronts than rears...after running some race cars with similar F/R weight distribution as 308's, (Brabham F-2's) I always had the higher rate springs on the heavier end of the car (rear), with something like 140 front and 210 rear. While I'm not trying to make the 308 a race car, tighter over-all handling with alot less understeer would seem to be achieved this way--any thoughts on this theory???

 

I tried that combination and found it cause quite a bit of understeer. Try to stay to about 25-50 lb difference f/r.

The "right" spring is kind of a personal preference thing. I now have 450/400 and like them. Others are very happy at 300/250 while other insist the stock 175/185 are the way to go......

 

2 words, motion ratio. The geometry is different in the front and rear. The effect is that the front shock moves somthing like 3.5" where the rear moves 5.5". So, the effect is that the fornt springs need to be a bit stiffer even though the front of the car is much lighter.

 

I went with 325 front and 275 rear.

 

Interesting thread, keep the spring rates coming!

Greg

 

You bring up a great point! During the suspension changes to the 308 here we also lowered the car and corner weighed it. Obviously you can adjust the F/R weight ratio when doing such things.

 

I am running summitt racing's 350 front and 300 rear. This is perhaps a bit on the stiff side for just street driving, 300/250 would be better). Wheels, tires pressures and shock settings are also a factor in comfort.

4 shocks, 4 springs, a wrench, (crap), a fender cover and two additinal torrington bearings, (two come with the junk wrench), came to something like $825. This is about as inexpensive as you are likely to find

BUT the stock QA-1 bushings and sleeves are NOT the right size.

BAD THINGS will hapen to your Ferrari if you do not properly resize the shock bushings. mounting a shock with an inner bushing size of 5/8 and using the stock 12 mm size bolt is a guaranteed to break the 12 mm bolt.

If you tighten the rear lower shock mount without side spacers AND a 12mm i.d. sleeve, you stand a very good chance of cracking the aluminum casting.

So, don't forget to add in the cost of having the appropriate bushings made to the cost of the QA-1s. I have no information on the Varishocks, Ohlins or any other units but it is worth checking.

hth
chris

 

I could be wrong but I think corner weighting is intended to equalize the left front and right front weight on the ground, (scale) and to have equal weights at the rear, side to side. This is done by adjusting the lower spring perch, which adds or subtracts "weight" from the corner being adjusted.

While we are trying to achieve equal front and rear weights, we also need to make sure that the chasis height is even side to side and ditto the rear, while maintaining the desired "rake".

The total front to total rear weight will remain the same unless you start moving vehicle components, luggage or ballast fore or aft in the chasis.

The only way that i know of to achieve this is with a set of scales. Given production tolerances and the unknown straightness of the individual ferrari chasis, i am not real comfortable with counting the number of turns on the shock spring mount ot achieve the proper set up.

I would be delighted to hear others approach to getting this done.

Still mired in ignorance.
chris

 

Aren't we trying to be sure that the LF+RR=RF+LR???

 

Four Cam and Chris, you are both right. +/- 30lbs is target incl driver.
Will look awkward for road -- it's only a track need.
25 - 30 mm of rake is the rec to me which works well.

I think stiff springs on a road car driven on bumpy roads gets old, fast.
Good luck.
Philip

 

I mentioned this in the other thread that is running, but I'll mention it here too. It is the shocks much more than the springs that make the ride harsh. And with shocks, you get what you pay for. Personally, I think the stock ride is a bit harsh and the car doesn't behave all that well. I have 450/400 springs on ohlins shocks and the ride is smoother than stock. Basically, the more you spend on shocks, the more spring the car will stand without giving up ride quality. I'd guess that with QA1s, 350/300 is probably about it and 300/250 would feel closer to the stock ride.

 

think there is a bit of mathematics here As the front and back will never be the same, this is the same as saying we want the two fronts to be equal and the two backs to be equal. Which sounds reasonable..

 

Chris,

Can you tell me where or how you had the shock bushings in the QA1 shocks changed to better fit the 12 mm bolt. I have these shocks and I need to do this mod for my 328.

 

Here's a major thread on the change to QA1's, though unfortunately the pics were lost in the FChat crash a couple weeks back. However, I have all the pics here saved to my harddrive if there are any in particular you want to see.
www.ferrarichat.com/forum/showthread.php?t=11974

What you need to do is change the "ferrell" which is the inner tube. You drive out the 1/2" ID tube and put in a 7/16" tube and ream it out to 12mm. You also need to add spacers since the mount on the QA1s are much narrower than the stock Konis. Same for the Varishocks, which you can see at http://www.ferrarichat.com/forum/showthread.php?t=39712

 

Brent,

Just as soon as i have a bit of time I will fit the sample bushings made by our good buddy Verell, at Unobtanium supply.

hth
chris

 

Hi Mike,

This is very helpful. Turns out the slop in these bushings were the source of a vibration rattle in the front. After taking off the front wheel you could actually pull up on the lower ball joint and see movement from the top shock bushing. I'm trying to understand exactly what your saying though. My bushing has an OD of 3/4 which fits nicely in the shock and an ID of 1/2" which has too much slop for the factory Ferrari suspension bolts. Shouldn't my new bushing be a 3/4 OD and a 12mm ID? I'm confused by what you mean 7/16" is that an OD? I think that would be too small to fit in the black rubber shock bushing? Also do you where I could get these made quickly? I need 8 of them. Machine shop?

Thanks so much
Brent
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Oh yes, I aready had been using spacers for these shocks.

 

A machine shop, sure, but probably QA1 Precision has them (just like Varishock has them for theirs and supplies them on request -- I got a set with mine).

The reason I say 7/16" ID is that you can't find them ready-made with a 12mm ID. 7/16" is just a tiny bit smaller than 12mm so they can easily be reamed out to 12mm. Of course, if you're having them custom made rather than getting them from QA1 or Varishock, you can just have them machined to the proper ID and OD (sounds like you need .75 OD) from the start.

 

OK now I understand. Any idea how much the 7/16" bushings are?

 

When I bought the Varishocks, they threw them in at no extra charge (by the way, they call them ferrels... the polyurethane that surrounds them they call bushings, not that it really matters). If you had to have them made, I've had similar spacers made out of aluminum for about $5 each, but I don't know if the material for the ferrules will make them higher cost.