| Author | Message | ||
| Brian Kennedy (Kennedy)
Member Username: Kennedy Post Number: 535 Registered: 3-2002 |
Please let us know how the Pilot Sport Cups perform for you. That, too, is the next tire I am going to try. Another option that should perform slightly better than the Corsas, are way cheaper than the Corsas, and work great on the road as well as the track, are the Kumho V700s. I've been very happy with them... but think the PSCups might be even better. However, the Kumhos have the same problem as the Corsas: that you end up with a too-small rear tire. | ||
| s.c.davis (360c)
New member Username: 360c Post Number: 12 Registered: 1-2003 |
I track my 360 Modena several times a year and have done some research on tire choice. Hoosiers are the fastest track tire; but are totally unsuitable for road use as they have absolutely minimal tread depth. Pirelli P Zero Corsa's are the best track road compromise;but beware, the rears are NOT available in the correct size. I took a chance and tried the 295/30 ZR18 and it presented a few problems. The speedo reads significantly out, the rear ride height drops which effects aero downforce and the traction control comes in very early (if you forget to turn it off). I currently run Corsa's on the front and P Zero C's on the rear, which seem ok. So for track use I now go with Hoosiers for the dry, Corsa/P Zero C combo for the wet and general road use. BTW, I use 360 Challenge wheels which are half an inch wider than standard road wheels from memory. By the way of a performance comparison, around Phillip Island Hoosiers are about 2-3 seconds a lap faster than Corsa's which are maybe 4 seconds faster than P Zero Rosso standard fitment tires. We are not allowed to run slicks; but a best guess is that they are maybe 2-3 seconds faster than Hoosiers. There may soon be another choice in tires with the new Michellin Cup Sport tire as fitted to the BMW M3 CSL. I will get the opportunity to try these out when mine is delivered in a week or so. If they are any good, I will let you know. | ||
| John B (John_b)
Junior Member Username: John_b Post Number: 84 Registered: 5-2003 |
I know this is only on a street car but I found similar results on my Modena. I took it to a track day recently and was suprised how "tail happy" it was. I was getting a lot of oversteer in the last third of the turn after the apex to track out in medium speed turns. The car would be much quicker if I could comfortably use the power there. This seemed more of a mechanical grip issue to me as speeds there were only about 80mph. I am getting some challenge wheels and mounting 235/18 fronts and 295/18 rear soft compound Pirelli P-Zero Corsa's I hope the extra rear width will help. (I currently have 235f 275r). The car seems like it would benefit from either less rear bar or more front bar. I didn't notice any problems or instability under braking though and I was braking pretty hard until they faded. (I subsequently put in Ferrodo DS2500 pads & Castrol SRF fluid which should help) I will be tracking the car again Nov 7th and will report on the results. | ||
| Will 575 (Willh)
Member Username: Willh Post Number: 323 Registered: 3-2003 |
Phil and all, after driving the 360C this weekend I reread this thread, very helpful. I think I will try to adjust brake bias by changing pad compounds - unless bias can be addressed directly. The sloppiness under braking - light or hard, really - would make me reach for the bias knob in any other car. The bloody thing also has a lot of oversteer, even with a bit of rear toe dialed in and modest fiddling with tire pressures. I keep thinking the aero on the car might - might - work better as entry speed increases, but who wants to experiment too much with that in this car? I am leaving lots of tenths in the fast corners, having to play too much both going in and coming out (apex on, going back to power oversteer). As the rear tires wear, it becomes impossible to get power down. Will try some of the suggestions posted here, though it's very hard to get into FoW's race shop. Think I need to hire a track & Phil for a day or two to sort things out! | ||
| Brian Kennedy (Kennedy)
Member Username: Kennedy Post Number: 527 Registered: 3-2002 |
> Ride height and rake makes big changes to underbody aero....but the more you get, > the more you lose when you slide or bounce, so mechanical grip and a wing > can be relied upon much more than the underbody. True of normal flat underbody or venturi effects. But what about an actual wing under body? I was looking at some pics in a Stradale article and one reminded me of one of the changes to the Stradale's underbody is that they effectively mounted wings low in each of the Venturi tunnels. Its width is obviously limited, but its depth and height is pretty substantial. That element should give good downforce independent of the butt rising. Thoughts? | ||
| Phil Hughes (Ferrarifixer)
Junior Member Username: Ferrarifixer Post Number: 239 Registered: 7-2003 |
The Australian team (Michelotto 2000) wing gives around 120kg of downforce at 200kph when set to max, at any body attitiude. The underbody generates around 80kg at 200kph...but only when the car is parallel to the ground and travelling in straight line on a smooth track. Ride height and rake makes big changes to underbody aero....but the more you get, the more you lose when you slide or bounce, so mechanical grip and a wing can be relied upon much more than the underbody. When fitting the rear bumper/floor the joint between them is critical, as if any misalignment is done (very easy), the bumper will turn into a parachute. The std challenge Pirelli tyres are adaquate and forgiving, but going to 245/645/18 D5 Front and 305/680/18 D3 or D5 rear will help considerably. Don't bother with the D6 as they are a different construction and behave quite differently. Ok for 3 lap shoot out's though if that's your thing. But don't set the car up to rely on them for long. Yes, they are over sprung and under damped....particularly the rear. The factory option 21mm Front antiroll bar is the best trackside option to adjust set up, I can change one in about 6 minutes now, but 20 is the norm. Do it after rake and toe changes....in that order. The N-GT cars use a virtually std under floor at the rear. The front bumper is all new and has a huge adjustable splitter. The ACO Le Mans cars have shorter venturis' and different side skirts etc. The front N-GT bumper has a removable panel to control air flow under the car. With it removed there is less drag but more pitch sensitivity. | ||
| Ben Cannon (Artherd)
Intermediate Member Username: Artherd Post Number: 1086 Registered: 6-2002 |
"In that case, the butt is way up" In any ordinary race car, I'd say to turn up the rear rebound. 360C may need a LOT more. My money says this is where the actual problem lies, and that the wing is just a band-aid. (no doubt it does help on the fast sweepers though.) Best! Ben. | ||
| Hubert Otlik (Hugh)
Intermediate Member Username: Hugh Post Number: 1554 Registered: 1-2002 |
There's a few ways to get the ass end to sit under braking: 1. lower rear ride height v. front; 2. greater toe-in on the rear; 3. moving up one step to a slightly more aggressive rear compound (w/out bringing on lock-up) to slow the rear slightly faster than the front, so as to keep some compression on the rear. Also, changing out the springs is the next step, to a set of softer springs, or adjusting the amount of rebound that's coming from the rear shcoks; slowing down the rebound might alleviate some of the the darting under braking, but the above changes , to the suspension geometry, will help too. Also, from everyone's comments regarding the twitchyness of the car, overall, I'd say that it's a weight transfer issue and the car "sounds" (to me) over sprung, and under dampend, but I'm a clown, so take it with a grain of salt. | ||
| Jon P. Kofod (95f355c)
Intermediate Member Username: 95f355c Post Number: 1113 Registered: 8-2001 |
Brian, I think we need to clarify a point here. All this discussion centers on a 360 Challenge being driven at the extreme limit where these issues surface. Also turn in speed between a 360 C and a street 360 are pretty large at speed due to the extra weight the street car carries. I think this may be why you don't feel it as much as someone in a Challenge car. If your suspension is stock and your car has an extra 400-500 pounds the transitions happened in a much more controlled fashion thuse the air distribution under the car has less negative effect. With 500 pounds less and let's say an extra 5-7 mph through a given corner there could be quite a difference in the nervousness during transition from front to back or vice versa. At 9/10's or 8/10's this nervousness and loss of downforce is not really an issue. The 360 C I drove wasn't set up very well and of course it wasn't my car so I am not trying to set lap records but the one corner with run off room I did drive it on the limit twice and the speed differential going in was much higher than in my 355 C. I typically turn in early and make one adjustment at the apex that tends to get the tail loose a bit (rotation) to avoid understeer. In the 360 C the second time around the car felt much more twitchy than when the rear steps out on my 355. Noticed it right away. If you are a late turn in guy then the nervousness would surface at the point of turn in up to the apex. My driving style isn't as conducive to the 360 without a wing. In the end I am no expert or aero or much of a set up person and my experience is limited in a 360 C but the one corner where I experimented with the 360 C is a corner I have taken a thousand times with my 355 C. The 360 seemed much more of a handful. Regards, Jon | ||
| Jon P. Kofod (95f355c)
Intermediate Member Username: 95f355c Post Number: 1112 Registered: 8-2001 |
As Mitch pointed out some of the nervousness on either the 355 or the 360 can be dialed out. Before my 355 was converted it had no wing and one particular turn and braking zone at Summit Point was giving me problems. Turn 4 (referred to as the chute) is a fast downhill right hander that requires braking from about 110 to 5-10 mph. We changed a lot of settings (ride height, brake balance, toe in etc.) but it only helped marginally. You come down the chute and if you are carrying enough speed you have to brake while the car is not straight and the left side suspension is loaded up but about to unload as you get straight. The ride height adjustments Mitch mentioned helped somewhat but couldn't cure the problem. I basically had to carry les speed and feather the throttle at turn in. My speed through the chute was about 105-110 mph. With the wing it no longer mattered. The car didn't need to be straight and instead of 105-110 I was doing 115 mph down the chute. Huge difference and one of the few places where I can catch a well driven 360 C if I am close enough coming out of turn 3. The rear wing may seem like a crude item in this era of nifty diffusers and underbody aero but I think there is a reason that at the top level of sportscar racing they are still used. Will, saw all your tires stacked up at FOW ready to go on your 360 C. Ought to be a great event. Are you bringing any of your other race toys? Regards, Jon | ||
| Brian Kennedy (Kennedy)
Member Username: Kennedy Post Number: 490 Registered: 3-2002 |
Interesting analysis, Mitch. However, with Venturi effects, getting the nose down and the rump up (as long as not too far up), should increase the overall downforce effects. So, though the center of force will move forward somewhat, it should just be increasing in the case of the 360. I've never felt anything worrisome coming off power in the exit of a turn... not even a twitch... now if you went total power off rather than just a controlled lift, might be different. Rather, in my experience, the only time my 360 makes me nervous is under braking... no question it will stop... just always a question whether you can keep it straight. Trail braking is particularly worrisome as the car is twitching as you initiate the turn. In that case, the butt is way up... possibly too far up causing the aero connection to the road to be broken, in addition to the natural weight shift you are combatting anyway. Jon, Solly, what is your experience on this? | ||
| Will 575 (Willh)
Member Username: Willh Post Number: 312 Registered: 3-2003 |
A serious question - are there any relatively easy to make at the track suspension changes, like bars, other than tire pressures? I'm not real happy with the handling of my car, and hate to have only one tool in the box. | ||
| Will 575 (Willh)
Member Username: Willh Post Number: 311 Registered: 3-2003 |
You guys are really helping me prep my excuses. It's not that I'm in touch with my inner slow guy ... it's the car! | ||
| Mitch Alsup (Mitch_alsup)
Intermediate Member Username: Mitch_alsup Post Number: 1207 Registered: 4-2002 |
"They all felt it needed a wing. Some of the discussion was centered on nervousness under braking but the majority of it was over loss of downforce in corners. It seems that lifting when making corrections (such as when the car pushes or gets loose) upset the air flow under the car and cause all sorts of problems." Amplifying what Jon Kofod said: lets say you have a car under power in the exit stage of a turn (between apex and trackout). The nose is high, and air has easy ingress and egress from the underbody. the underbody aero delivers several hundred pounds of force to the rear tires. Now assume the driver needs to back bown the power in order not to leave the road at trackout. As he backs down power, the nose comes down and the center of aerodynamic pressure (under the car) moves forward, increasing front aero bite while decreasing rear aero bite. Not a good situation to be in: A) stay in it and leave the road, or B) back down and spin. The Jaguar GTP car from the early 90s had this problem. See "Race Car Aerodynamics; Designing for Speed" Joseph Katz. A rear wing does not have this kind of sensitivity with respect to nose height and its downforce is constrained to the rear of the car (e.g. doesn't move around). | ||
| Mitch Alsup (Mitch_alsup)
Intermediate Member Username: Mitch_alsup Post Number: 1206 Registered: 4-2002 |
I know on the F355 cars, the wiggle under braking comes from the Front suspension ride height. Get this set right, and then use the rear ride height to balance the oversteer/understeer relationship you desire. A wing does basically noting at 50 MPH, nor do the underbody aerodynamics! Aerodynamic devices tend to generate force quadradic wirh respect to velocity; 2X velocity gives 4X the force. I belive the tunnels on the F360 are supposed to generate about 400 pounds of downforce at max speed (188 MPH), this becomes 100 pounds at 94 MPH, and 25 pounds at 46PH. So if the car is not doing what you want it to do in 50 MPH turns, the solution is to manipulate the mechanical grip of the car (ride heights, springs, shocks, alignment, tires) until it is correct. Then use aero to balance the high speed handling characteristics. | ||
| Jon P. Kofod (95f355c)
Intermediate Member Username: 95f355c Post Number: 1110 Registered: 8-2001 |
Solly and I were just discussing this issue last week at Pocono International Raceway. If most of you will recall, at the very first 360 Challenge race at Homestead in 2000 a grand total of 12 360 Challenge cars were crashed some beyond repair. Steve Earle, multiple time Challenge champion said the 360's seemed to have a much smaller window between on the limit and OVER the limit. They all felt it needed a wing. Some of the discussion was centered on nervousness under braking but the majority of it was over loss of downforce in corners. It seems that lifting when making corrections (such as when the car pushes or gets loose) upset the air flow under the car and cause all sorts of problems. Halfway through the season the Challenge teams petitioned FNA for a wing but Ferrari said no. The belief is that so much was invested (time, money and marketing) in the 360 Modena's underbody and aero package that FNA and Ferrari didn't want to alter the Challenge car from the street car. In other words, Ferrari was touting the relative improvement of downforce on their 360 street cars and using this as a big selling point, that adding a wing to the race car would somewhat be an admission that the effectiveness of the aero package on the street car was overhyped. I have driven the 360 C and while it seems to be a superior car to the 355 C in almost all respects it did seem to be much less forgiving than the 355 C. Phil, didn't the Group N cars in FIA change the underbody aero package at high speed tracks like Spa and Monza? I seem to recall that the top teams did extensive modification to the underbody in addition to adding the wing. Solly, you coming out to Summit Point Raceway this weekend for the big event. Spoke to FOW and there are 70 cars lined up. Should be fun. Regards, Jon P. Kofod 1995 F355 Challenge #23 www.flatoutracing.net | ||
| Will 575 (Willh)
Member Username: Willh Post Number: 310 Registered: 3-2003 |
Phil, interesting to hear your comments, I have heard other mention the rear toe in - might help with what I find to be wicked oversteer at times (though I haven't been able to get my car aligned and scaled). I am new to the car, this weekend will really only be myfourth and fifth days - a fine car, but like perhaps most other race cars really needs a lot of optimisation to go truly fast. | ||
| Brian Kennedy (Kennedy)
Member Username: Kennedy Post Number: 484 Registered: 3-2002 |
Phil, how much downforce does the wing provide at 50mph? | ||
| Phil Hughes (Ferrarifixer)
Junior Member Username: Ferrarifixer Post Number: 238 Registered: 7-2003 |
Yes Ben, I've been spannering a fleet of up to 10 360 Challenges (and N-GT) for 3 years, in a formula where some deviation from factory spec is allowed, so a great environment for experimentation. Factory springs/shox are woeful on bumpy tracks, but the softer spring options (from the parts manual) will tame it a bit. The best way though is to fit adjustable shox and have a professional set it up to suit your style. They are very responsive (critical) to set up changes, so you can always achieve any characteristic you desire, if you have the people and equipment to do it. | ||
| Phil Hughes (Ferrarifixer)
Junior Member Username: Ferrarifixer Post Number: 237 Registered: 7-2003 |
I'm shortly getting the next batch of rear wings delivered. Price TBA but well under half Michelotto prices! The team has built replica wings of the 2000 spec Michelotto N-GT car, which is smaller than the current cars, but still quite efficient. You can see them at www.procar.com.au in the image galleries. We have used them very successfully for 2 years now. In the meantime, you can reduce the tail happy nature by increasing rear toe in up to around 4-5 mm each side...a total of 8-10mm toe in. Sounds a lot, but the 360 goes to toe out on the rear as it lifts if it's below these values, and you wont chew your tyres up. You can also adjust the "brake balance", by using more aggressive front pads and/or less aggressive rear pads. Using slotted discs on the front only will also help. | ||
| Ben Cannon (Artherd)
Intermediate Member Username: Artherd Post Number: 1085 Registered: 6-2002 |
I don't think I would ever want traction control on a mid-engine car. The LAST thing you want to do at 10/10ths is lift! (Now for the idoits who don't know what 400hp can do in a light-ish sports car in a 1st gear 180* turn, F*** 'em let them use the ASR. I'll take the circuit that disables it by default on engine start.) Note I've never driven a Challenge spec 360. Do they really wiggle that bad? Is it because of the lack of wing, or something else affot here? (they brake so well that tyre deformation occurs?) Has anyone done any real telemetry based research to find out what's going on? Best! Ben. | ||
| Brian Kennedy (Kennedy)
Member Username: Kennedy Post Number: 478 Registered: 3-2002 |
Interesting. I experience the same tail wiggling and squirming under heavy braking. Given it's actually worst under straight-line braking because it was so random which direction it would squirm/wiggle, I ended up blaming my tires for a lot of it... I think I was braking so hard that the tires would actually give going into either left drift or right drift, causing the squirm. I fixed that by going to much higher tire pressures than I would normally have used... cost me some traction on cornering, but gave me oh-so-much more confidence in every braking zone. Of course, the back end was still very loose under trail braking... but I'm starting to get used to that. It will be interesting to see whether the improved aerodynamics of the Stradale (higher lip on back, larger venturis underneath in back) will make an impact here. Just don't know how much extra downforce you are getting at trail-braking speeds (40-80mph)... though its pretty impressive up at 100-140mph. Its nice to hear the Challenge ASR actually is usable on track... maybe the Stradale's will be too. I still probably won't use it much, but I'd love to be able to turn it on as an "aggressiveness threshold" when I let others drive it... with the Modena that threshold would be far too low. | ||
| Steven J. Solomon (Solly)
Member Username: Solly Post Number: 642 Registered: 6-2001 |
Brian-Yes, in heavy braking or trail braking the back of the 360 wants to get loose, and if you don't catch it immediately you are in a spin, and i mean immediately. The 360 is not an easy car to drive at high speed, very unlike the 355 Challenge which is much more forgiving. There is a reason the 360GT cars all have wings now. I usually leave the ASR on until I am comfortable with the track and the tires are warm, then it goes off. I can threshhold brake better than the computer, and don't lose acceleration when I get back on the gas. I only started timing myself recently, but at the Glen event I did a best of 2:18 with the ASR on, and 2:14 without it. | ||
| Brian Kennedy (Kennedy)
Member Username: Kennedy Post Number: 477 Registered: 3-2002 |
> We used the traction control the entire time, which I assume retards > acceleration slightly, but still the power was pretty impressive. Another question for Solly... is the traction control on a Challenge actually usable during agressive driving?? I've never been able to get around more than the first turn without having traction control kicking in way too much... I never drive on the track with it on in my Modena (or any other car I've ever owned). | ||
| Brian Kennedy (Kennedy)
Member Username: Kennedy Post Number: 476 Registered: 3-2002 |
I am curious why you say it needs a rear wing... I wonder if you're experiencing the same thing I do in heavy braking... inquiring minds want to know... | ||
| Steven J. Solomon (Solly)
Member Username: Solly Post Number: 638 Registered: 6-2001 |
Nothing like a warm dry day at Watkins Glen with slicks to scare the crap out of a passenger. And you are correct, the brakes are amazing, especially with the Ferodo pads we found for them. I can outbreak just about every car out there into the turns. But the car needs a rear wing for sure. I'm trying to find one. | ||
| DES (Sickspeed)
Senior Member Username: Sickspeed Post Number: 7164 Registered: 8-2002 |
Jack, very awesome, thanks for sharing...! i get goosebumps just thinking about what it must be like...!  | ||
| Jack (Gilles27)
Intermediate Member Username: Gilles27 Post Number: 1452 Registered: 3-2002 |
At the request of DES, I thought I'd make mention of my experience yesterday: I got a call from a friend of mine late Monday to say that he had rented out a local track (Blackhawk, for those of you familiar) for Tuesday and if I'd be interested in coming out. Um, well, SURE! Once at the track, there were only five of us which meant plenty of open track. It was the first time I've tracked my 328, and the combination of a damp, leaf-covered track along with an 80-mile return trip meant I went pretty easy. Anyway, before I left for home, Dave had me strap into his Challenge (he had a second seat put in--don't think they're standard but not sure) for a few laps. The sound alone from the cockpit is incredible. It sounds like a racing engine should. We pulled out of the pitlane, and immediately I could tell how cool this was going to be. For a little perspective, Blackhawk isn't a long track. It claims 2 miles, but our odometers all agreed with about 1.6. The track was still damp from morning showers, and like I said, there were wet leaves everywhere. Pretty to look at, but a bit on the slick side. With treaded tires mounted, we were lapping about 15 seconds slower than would normally be the case. All the way around the track, the car was so firm, and you could really feel the side loads through the turns. We used the traction control the entire time, which I assume retards acceleration slightly, but still the power was pretty impressive. However, like you always hear, what really impressed were the brakes. I believe they use 14-inch front rotors, and as we would head into the first turn, it was unbelievable how late he could get onto the brakes. They literally press you against the harness. Needless to say, it was an experience. Dave promised that, on some clear day, he'll let me actually drive it myself. That will be something. Andreas, sorry I didn't have time to call you. I found out myself too late to corral others. I'll definitely be able to get you a ride some day, though. |