I have a problem with the handling of my 91 348TS. How do you correct the over steering problem? I think that's what you would call it because at higher speeds my car wants to "float" all over the freeway. It almost feels like it's floating on air and wants to jump lanes. The steering feels very touchy and sensitive at speed. It feels like it's swaying back and forth as if floating I recently put Bridgestone SO-3's 255/40/ZR17 on the rear. The front tires are the original ones 215/50/ZR17 Bridgestone RE-71's. Only the rear tires are new because when I bought the car (2 months ago) the insides of the rear tires were worn to the pont of the nylon showing through and the fronts have 70% tread left . Would the difference in size make the car drive like it does? I never noticed the car handling like it does when I bought it because I didn't want to go that fast with the old tires being in the shape they were in. Could it be a caster problem?
i almost spun my car driving it home day i got it. replaced orig tires with kumho mx 225 front and 275 rear with stock rims and was transformed into easily predicable handling on track and street. now have similar tires on 8x18 front and 295 on 10x18 rear. better still but much more subtle improvement compared to 1st change from original tires. also not good idea to mix old and new. should replace all 4 together.
I've checked the alignment and the front toe-in is at 2.5 mm, well within specs. The rear camber was in too far as shown by the excessive wear on the inside wear of the tires so I removed some shims to get it within specs of 1.5 degrees. The reason I didn't change the front tires is because they still have 70% tread left. I know I know,(should've done both) but hey. Guess I'll be ordering the new fronts also. I tried taking the front tires off of my 308 and putting them on the 348 just to see if the tires made a difference in the handling, but the rims don't fit over the hub!
John: Very sorry to hear about your problem (we discussed this earlier in the "Who Makes Ferrari" thread). All I can say is that purchasing only two new rear Bridgestones for my 348 RUINED the handling. Once I got two new front tires onto the car, the handling was fine again, even though the old fronts still had plenty of tread remaining on them. My symptoms were exactly the same as you are describing. Are there any other 348 owners in your area? Perhaps you could arrange to "borrow" their wheels/tires for a quick test drive for comparison. I'd happily lend you mine for an afternoon if you were up here.
Good to hear. I have a good feeling this will resolve the issue. The tires are from 1990/1991 - original issue. So, they are probably rock hard. The rubber itself doesn't keep, unless properly stored, and I'm not too sure about being stored for 13-14 years. Different compounds will cause the car to behave erratically. So get the S03's for the front and see how it goes from there. It will build your driver confidence if nothing else, with newer tires. I'm quite sure you'll feel a difference.
Could the problem John is describing also be considered tram-lining (sp) ? I had a very similiar problem when I first picked up my 348... dave indy
good pick Randy! The tyres will only be good for 6 years at the most even stored in optimal conditions. I am forever being berated by a friend of mine who runs a tyre shop for up market cars and he has some fancy alignment gear as well where he recommends putting on as much -ve camber as possible (well he would wouldn't he ) Alway seems a shame to change tyres when there is heaps of tread but if they are causing erratic behaviour and the alignment is right then they have to go. One thing I found when I put as much -ve camber on as possible was that at high speed the car is slightly unstable but it turns in nicer whereas with the factory setting the car was stable at high speed but understeered heavily. Sort of , if you drive hard use heaps of camber and castor (6 degrees from memory), if you *****foot it a lot then use the factory settings
New S0-3's are going on the front today. Hope it clears the problem. Thanks all for the help. Good point Schatten, never thought of the rubber getting brittle.
I replaced my rears only ('90 348) in September as they had been reduced to a complete slick. I've had no handling problems to speak of. I don't quite understand what new rubber on the rear would do if you use the same brand/compund.
Haven't had the tires put on yet. Yesterday the tires didn't come in until around 4:15, so by the time I got there,(4:35) they said that there wasn't enough time for them to put them on and balance them. Today It's been raining ALL FRICKEN DAY. Hopefully tomorrow
Don't know what happened to my update post 2 days ago, but here it is again. Had the new so-3's put on the front. It made a big difference in the handling, but still seems to "float" at speed >90 mph. The steering is very sensitive at higher speeds, almost like oversteering. To keep it in my lane on the freeway at speed, is a full consentrated effort. My 308 feels rock solid at speed, compared to the 348. Wonder if more toe-in would help?
You don't mention having checked the front camber, might be worth checking, it should be -0° 30' to -0° 50'
Doesn't the 348 have adjustable ride height? Is it in spec? My 308 gets very sensitive when cornering at 100+ at the track (like the kink at Road America where it responds to very small inputs). I run 30 mm of rake F->R so there's a lot more weight on the front. We need to tighten the front end/loosen the rear ARB to make it more stable. Philip
How is the camber adjusted on the 348? Is it with shims...and if so are they specialized Ferrari parts or something that most alignment shops would have? Thanks, James
Harmony, if it is just wish shims, it will be the same as this TR here. The shims aren't anything special from what I recall but a more seasoned mechanic can shed some light on this topic.
Had the new so-3's put on the front. It made a big difference in the handling, but still seems to "float" at speed >90 mph. The steering is very sensitive at higher speeds, almost like oversteering. To keep it in my lane on the freeway at speed, is a full consentrated effort. Rivee, My '91 348 feels the same, at least when I first bought it. It now seems far more stable, which I put down to sensitive steering that I was not used to. I also run S03's front, contisports rear with 25mm spacers rear, 15mm front. 80-90mph seems to float- slighlty, which then settles down above 100mph. The inside lane of the motorway is paticularly bad which I put down to ruts in the road caused by heavy lorries. Cheers John
No I haven't, but I was told that increasing the caster angle by a degree or so, will help the car's stability on the road, but be harder to steer. No I haven't checked the height of the car yet, but I'm going to. The shims are the camber adjustment fot the 348. They are just round discs the same diameter as the connecting bottom a-arm bushing mount.
Could well do, the purpose of the castor angle is to provide a degree of self-centring for the steering. This makes the car easier to drive and can improve it's straight line stability. Excessive castor angle will make the steering heavier and less responsive, which is why performance cars tend to have smaller castor angles than regular production cars. The basic castor angle for your car is 5° 30' ± 15'
Malcolm Given this, why do the 308/328 series of cars typically operate with about 4 degrees of castor and the 288, 348 (355?) with 5 or more degrees? All (except) 355 are manual steering. Other things being equal, do you typically want the least castor (=max cornering responsiveness?) you can get away with while preserving a stable platform? Philip
