| Author | Message | ||
| P. Thomas (Ferrari_fanatic)
Member Username: Ferrari_fanatic Post Number: 381 Registered: 4-2003 |
Thanks Mitch, much appreciated as that is the basic info I needed regarding set-up, handeling characterisics, etc. | ||
| Craig Williams (Craigw)
Junior Member Username: Craigw Post Number: 148 Registered: 4-2002 |
I've just had 4 new tyres and the geometry properly set up on my 348, the car has never felt so planted & stable. I'd reccomend geometry checks to everyone. | ||
| Mitch Alsup (Mitch_alsup)
Member Username: Mitch_alsup Post Number: 746 Registered: 4-2002 |
"Given the proper speed rated tires, what do you think is a comfortable speed for the 355 to "cruise" at?? It is about a 60-90 mile stretch depending on the highway." At least 140, and if the suspension is dialed in just right around 160; but beware, there is a big handling difference that occurs in the window between 140 and 160 if the car is not just right. There are two different stability issues with respect to the F355 (and most likely the later F348s). A) if the front is set too low with original springs, the front end will be twitchy under braking at high speeds. In my car I could 'feel' the center of pressure* move forward under brakes at high speed. B) basic oversteer/understeer relationship (again, with original springs and anti-roll bars) is set (after the front is at the right height) by the rear ride height. Lower the rear for more understeer, Raise the rear for more oversteer. This can also be used to adjust the suspension of tire width changes (265/40ZR18 -> 295/30ZR18) and get the car perfectly neutral over a wide range of conditions. Even little changes here will change the 'feel' of the steering at speeds above 140 MPH. * underbody aerodynamics: the center of pressure under the car pulls downward on the body from a certain point where the pressure fore/aft are equally distributed. When the car is in a braking attitude, the center of pressure can move forward (inducing oversteer) if the rake is too far forward. If you get this sensation, raise the front by 2-3 turns on the shock collars. I happen to love my S03s, I currently have 5,000 road miles and 13 track days on this set of S03s. And as a point of reference, I was timed at 2:10 at TWS this last weekend. I am running 225/40ZR18 front and 275/40ZR18 rear with 35 PSI cold at each end at the TWS track, but only 33 PSI cold at each end at MSR, and 36 PSI cold on the street. I also found that in the pressure range from 35 PSI to 38 PSI, the car would feel 'sloppy at the lower end, and feel stiff at the upper end. This allows me to tune the car to the conditions quite easily. | ||
| Dennis (Bighead)
Junior Member Username: Bighead Post Number: 135 Registered: 2-2003 |
Rob, according to Michelin, the acceptable width for mounting a 295/35-18 Pilot Sport is 10"-10.5". The "measured rim width" is 10.5". In choosing a rear tire size, I went with 295/35-18, instead of the alternatives, for a variety of reasons. The stock OEM size was available only in Pirelli P-Zero SYSTEM, which I dislike, and the Bridgestone KD and KD/W; the KD wears too quickly and has not-so-good wet weather performance, while the KD/W wasn't as good in the dry. Various other size options varied too much in total diameter from spec. Other brands were a bit "older", like the S-02 or AVS Sport or SP Sport 9000. I tried the S-03, didn't like them (as noted), and went with the Michelins. Not cheap, but great wet and dry grip, reasonable wear, and good "feel". Specifically to your question, Rob, I haven't used these street tires on the track, but I was hoping the wider rear tires would help curb some oversteer tendencies. The car is aligned fairly neutral, and I don't drive fast enough on the street to find understeer limits. I was more concerned about surprise oversteer limits, so having more, wider rubber at the rear at basically no "cost" seemed like a good idea. A friend tried the size and loved it, so I gave it a shot. After putting a few thousand miles on it, I can report that the rear does not feel any "looser", if I understand your question -- if the sidewall height had remained the same, I would think that the greater ratio of tread width to wheel width would have made a *bigger* difference; maybe the shorter, stiffer sidewall compensates for this? In any event, I haven't yet found myself in a situation where the car has felt unsettled, either oversteer or understeer, on the street, so I can't testify as to how they feel at the limit -- though I have driven the car a bit aggressively in the White Mountains. The tires look new, and I have no complaints. vty, --Dennis | ||
| David McAlexander (Stuttgartdavid)
New member Username: Stuttgartdavid Post Number: 15 Registered: 5-2003 |
On the issue of high speed stabilty: Remember that alignment plays a big role in the "twitchiness" of a car. I set my autocross car up with a very different alignment than used for my high speed time trial car (using some toe OUT to initiate quick turn-in - the result is ligthtning fast response ala' the intentional dynamic instability of an F-16, but also a good bit of "dartiness" at speed I wouldn't want in the middle of turn 9 at Willow Springs!) If you are going to run those kinds of speeds, especially on state highways with the guardrails, drop-offs, and trees which are a far cry from the relatively safe and sanitized run-off areas of a race track, get the car realigned at a good shop and tell them your intended use. | ||
| Rob Schermerhorn (Rexrcr)
Member Username: Rexrcr Post Number: 658 Registered: 11-2002 |
I'm curious, how does the change feel? Technically, the tire's about an inch or so wider, and on the same wheel, will have a bit less lateral "stability" in that the sidewall is no longer as vertical as with the narrower tire. One way to potentially make a tire more responsive to directional changes is to mount it on a wider wheel. If you can visualize it, the 'wide tire, narrow wheel' combination, the wheel can move laterally more than a wheel-tire combination of say, 10 inch wide tread with 10 inch wide wheel. ?? | ||
| P. Thomas (Ferrari_fanatic)
Member Username: Ferrari_fanatic Post Number: 379 Registered: 4-2003 |
Frank, that brake squeel is damn annoying. I have Brembo pads, and I am going to swap them out to the Porterfields. Dennis, Thanks for the info. | ||
| Frank K Lipinski (Kaz)
Member Username: Kaz Post Number: 327 Registered: 11-2002 |
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| Dennis (Bighead)
Junior Member Username: Bighead Post Number: 134 Registered: 2-2003 |
Frank asked, "Dennis did the 295-35/18 change your speedo? I was told there is only a 5mm difference and it won't alter the speedo... I'm thinking of doing same or maybe 245/40....?" _____ Well, theoretically, it would. The change from the stock 265/40-18 to 295/35-18 results, on a purely mathematical basis, a smaller diameter -- but it's only 99.178% of the original diameter. So, less than a 1% decrease. I think there is probably a bigger variation than that when you switch from one tire brand to another. Also, a 1% change in tire diameter is well, well, well within the margin of accuracy of a standard Ferrari speedometer (typically +10%). :-) vty, --Dennis | ||
| Frank K Lipinski (Kaz)
Member Username: Kaz Post Number: 325 Registered: 11-2002 |
Paul - I have a 96 Twin Turbo with a Richard Danvers motor. Seems that over 140 the front end "floats" unless you have a full tank of gas to off set the balance - Porterfield R4S are the best thing since sliced bread on a 355. I could not go to the gas station and back without wipping down my wheels from dust, and not to mention the embarassing squeal of stock pads. Great daily pad, but prob too soft for track use. About $150 a pair. www.porterfield-brakes.com (I think) Dennis did the 295-35/18 change your speedo? I was told there is only a 5mm difference and it won't alter the speedo... I'm thinking of doing same or maybe 245/40....? | ||
| Dennis (Bighead)
Junior Member Username: Bighead Post Number: 131 Registered: 2-2003 |
Re S-03: Too much sidewall flex. It made the car feel like I was running softer springs. I played with pressures, and even drove it a few hundred miles to make sure all of the tire compound was worn off, but it just didn't feel right to me. Tire Rack exchanged them for Pilots (which I got to like when we bought my wife a 996 with those tires on it). Happy enough with them. I'm cheap enough, though, to consider brands like Kumho, but they don't offer anything in the sizes I needed. vty, --Dennis | ||
| P. Thomas (Ferrari_fanatic)
Member Username: Ferrari_fanatic Post Number: 378 Registered: 4-2003 |
Dennnis, what didn't you like about the S03? I had them on a P-car and they were awesome. The Pole Positions were great in the wet, but a moot point as my F-car will never see any rain. | ||
| Dennis (Bighead)
Junior Member Username: Bighead Post Number: 130 Registered: 2-2003 |
I switched to Michelin Pilot Sports (not the A/S, nor the Cup) for street use. Used to use the Bridgestone S-02PP; didn't like the S-03 version. Happy with the Michelins. Moved up in rear tire size; run a 295-35/18 without any problems. Swapping between ATE Super Blue and 2000 between fluid changes (same fluid, different colors, makes bleeding easier). For pads, running Performance Friction PFC-97. Squeal a bit, but lasts long and great bite. This is all for combined street/track use. For track use, I run Pirelli P-Zero racing slicks (the D3 compound). vty, --Dennis | ||
| P. Thomas (Ferrari_fanatic)
Member Username: Ferrari_fanatic Post Number: 377 Registered: 4-2003 |
Frank, which P-Turbo did you have? A 993 or a 996. I had a ton of P-cars before my f-car. I have not had my car over 125. There just is not enough open road in the immediate SFO Bay Area, plus I have been working too much! Does Portefield make more than one pad for the 355? Frank, which Porterfield pad did you get? | ||
| Frank K Lipinski (Kaz)
Member Username: Kaz Post Number: 323 Registered: 11-2002 |
I also believe that was a 348 thread. I�ve had my 355 at 140-145 for prolong periods on several occasions. I am always impressed with the stability of these cars at high speeds. All temps hold normal and the car really sticks (at least compared to my P-Turbo). All stock except brakes - I changed to Porterfield to eliminate stock squeaking. On the way back from Sebring there is a nice winding road � cruised it for about an hour at 100 and do so very safely�for about the first 30 minutes tagged up with another 355. Dr. Mike..was that you by chance? Was a red spider � Euro with Tubi� | ||
| P. Thomas (Ferrari_fanatic)
Member Username: Ferrari_fanatic Post Number: 376 Registered: 4-2003 |
Thanks, Dennis. The thread I was referring to could very well have been referencing the 348. What are you running for tires, brake pads, brake fluid, etc? | ||
| Dennis (Bighead)
Junior Member Username: Bighead Post Number: 129 Registered: 2-2003 |
P. Thomas, are you sure you aren't thinking of the 348? The earlier models have gotten a reputation for snarky handling at the top (not so much top-speed related, but at the limits of lateral adhesion). I happy to like the handling of the early 348s, but that's the common perception. I haven't heard the same of the 355. And the car is designed to reduce lift at speed with the "downforce" tunnels. I've had my 355 (stock street) running 155 mph on Long Pond Straight at Pocono with no stability problems. vty, --Dennis | ||
| Mr. Doody (Doody)
Intermediate Member Username: Doody Post Number: 1178 Registered: 11-2001 |
i've taken mine to 125 with the top down, and it was impressively smooth - with the top down. you want to haul ass for 90 miles? get a maranello and you'll never look at 160 the same way again ;-) doody! | ||
| Dr Mike Jacobsen (Dr_whoopie)
New member Username: Dr_whoopie Post Number: 4 Registered: 5-2003 |
These cars run cooler the faster you drive them. At least at Sebring When I do 20 minute "balls to the wall" runs and reach 140-150 on the 2 straight-aways. I would expect if the tires are perfectly balanced original size, and aligned the car could cruise at those speeds easily and maybe faster if the pavement was smooth and flat. Fly n High, Dr. Whoopie! | ||
| P. Thomas (Ferrari_fanatic)
Member Username: Ferrari_fanatic Post Number: 356 Registered: 4-2003 |
Recently, a thread popped up on the Silver State Classic "race" (it is an open strecth of highway where top speeds are legal at this sanctioned event) in Nevada. About a month ago I read a thread on the 355 (I beleive) stability issues. Given the proper speed rated tires, what do you think is a comfortable speed for the 355 to "cruise" at?? It is about a 60-90 mile stretch depending on the highway. |