CHASSIS DIFFERENCE BETWEEN 348TB AND 348GTB/SPIDER?

Ferrari lowered the upper chassis rear a-arm attachment point by about 20mm, this raised the roll center in the back, and transfers more weight to the outside front in turns, inducing understeer (n.e. quelling oversteer.)

The Specialé was the first 348 to get this suspension which carried over to the F355. All 348s made after the Specalé got the suspension change.

For a while (several years) there was a jig circulating around that one could attach to a disassembled rear end to guide the drilling of the new lowered suspension pivot points.

 

I'd love to see the spec drawings on the two.

 

FWIW, the change supposedly occurred in June, 1992. I don't have an exact SN but as a somewhat educated guess that would be somewhere around the 94000 mark.

I tend to doubt that you can redrill the original tabs since there's not a lot of room on them. I suspect you'd have to weld new ones into place. Replacing the lower forks is also required. It's actually pretty easy, but not inexpensive if you use OE forks. I've been hoping to find a set for myself but so far the ones I've seen are too expensive to make the modification cost effective.

If you're only concerned about track handling you can achieve much of the same results by lowering the car significantly, a la the Challenge cars. In fact, it's been my supposition that the car was designed to be run 25 mm lower but that proved impractical on the road so the geometry was altered on later cars to mitgate the effect of raising the ride height. Don't have any evidence to support that but it makes sense to me...

For road use it really doesn't matter as long as the car is properly set up and aligned. That's critical on *any* mid-engine car-- the more "race-car-like" the car, the more the setup changes are felt by the driver. A poorly set up later 348 would handle worse than a well set up early car.

IMO the "evil handling" hype surrounding the early cars has been vastly overblown over the years. Yes, the car will bite an unskilled/unaware driver, especially if it's not set up properly, but so would a lot of cars built before electronic nannies took over the task of car control. A well set up early 348 will handle beautifully and will be quite controllable even on the track, especially if it's lowered at least a bit.

HTH.

 

I dug up a picture I had from 2002 when I investigated F355 suspension stuff. Many of the files are unreadable, now. So this is the best I have:
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I had a 1990 348TS that had the sudden oversteer problem. I have been driving sports cars for years, including a couple of years in a bathtub Porsche in SCCA racing. The 348's sudden oversteer caught me out once, but I was able to catch it. That, and the fact that the car was underpowered, led me to sell it and buy a C5 Corvette instead - a much better handling car with more power.

 

I have a good bit of experience tracking both street and race versions of the 348 and C5. Properly set up, the 348 is a better handling car. There was something wrong with your 348.

 

If you click on the item 6's ie moving frame you can see the carious options and they quite often reference the suspension fork type

Ferrari 348 TS (1993) - Frame - Rear Part Elements: Page 104 | Order Online Eurospares


The 2 types of fork with notes shown here:

Ferrari 348 TS (1993) - Rear Suspension - Wishbones: Page 040 | Order Online Eurospares

 

Is that all it is?

See item #21 and the difference between the two (early and late cars).

Too bad the superseded part is listed at $900 each, and the 348 needs four of them (same on the 512TR and 512M).
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So the lower A-arm on the later cars has a "higher" mounting point where it attaches to the sub frame.

 

A blow up and crop to show how the lower A-arm is positioned relative to the sub frame.
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There's a corresponding change to the upper A arm pivot point as well. I'd been thinking Maranello just moved the mounting tabs but based on the pics in the link Jeff posted it appears they did it right and actually moved the bracing.

 

$900 for that?

give me the 3D file and I can get that machined for less.

Kai

 

I'm still looking... because I can't see it yet.

The part numbers can be confusing since the later ones are superseded. On ebay, they can be misidentified as well.
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Wade, which version of the lower fork is fitted to your TB-- the straight one shown in the main drawing or the curved one shown in the inset drawing?

 

I think there's a lot more than the forks to convert a car from old to new spec suspension


Ferrari 348 TS (1993) - Rear Suspension - Shock Absorber and Brake Disc - Valid Till Car Ass. Nr. 8798: Page 039 | Order Online Eurospares

Ferrari 348 TS (1993) - Rear Suspension - Shock Absorber and Brake Disc - Valid From Car Ass. Nr. 8799: Page 039 | Order Online Eurospares

Rear wheels also changed with a different offset (which could be simulated by adding spacers)

 

I have the curved one. Which I assume is the later version since it matches the F355. Was there a service bulletin (TSB) to replace the early "flat" forks?

Following it's part numbers; 100784 (early 348, 400i and 412) supersedes to 136189 -> 159399 (all F355 and Mondial t).

https://www.ricambiamerica.com/100784-fork.html

Search Results for 159399 - Eurospares | Order Online Eurospares

The "flat" fork, 116690 (early 348, 412 and Testarossa), supersedes to 177707 (348, 512TR and 512M)

https://www.ricambiamerica.com/car-diagrams/ferrari/v6-v8/348-group/348-1989-1992/rear-suspension-wishbones/116690-fork-f.html

Search Results for 177707 - Eurospares | Order Online Eurospares
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The rear A-arm fix point "height reduction" (production improvement) started in 06/01/92, and my car was built in August 1991. So, "height reduction", does that mean lowering the rear of the car itself?

http://www.ferrarichat.com/forum/144103176-post16.html

Ferrari348Enhancements

 

This modification does not alter the ride height at the rear.
Ride height in 348 are controlled by shims on the spring perches.
Ride height on 355 are controlled by threaded spring perches.

This modification moves the instant center inwards, and raised the rear roll center.

 

minor correction; 348s are threaded perches.

 

I can vouch for them being threaded - I'm currently overhauling mine
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As we know, the knuckles are different between the early and late 348s. Is the upper part of the knuckles different lengths as well? So different length upper A-arms too?

I'd love to see these parts side by side.
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