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Question about sports cars / capabilities
- Thread starter Mike_Honcho
- Start date
plenty vids posted to laugh at with guys on bigger bikes having their asses handed to them by guys on smaller bikes
same thing happened to me at the track, busa would smash me on the main straight then unable to keep up with me after turn 3 until we hit the straight again at turn 12, or maybe my 600RR was too wide to pass
that would depend on who set the suspension for the rider
1 hand on the throttle the other flat on the ground, fun but scary
Boys. Boys.
Let us quell this quarrel, and ogle the beauty of that which is Sterling Moss’ 1966 Jaguar XJ13...
Let us quell this quarrel, and ogle the beauty of that which is Sterling Moss’ 1966 Jaguar XJ13...
Time for some physics nerdery.
Lateral acceleration (so-called "g's") is related to the corner radius and vehicle velocity (roughly the indicated speed), obviously. It's something like this:
A = v^2/r
Doubling the speed through a corner requires 4x the lateral grip from the tires. Assuming that the speed limit is posted for a lateral acceleration of 0.25g (typical a safe assumption for interstates; back-country roads are a whole 'nother story), doubling the posted limit takes about 1.0g. Go into a 25 MPH corner at 51 MPH with a setup that is only good for 50 MPH, and you're going to be short about 4% of the grip required. Might turn into a long day if there isn't enough room to scrub off a bit of excess speed.
Interestingly enough, this hypothetical 50 MPH corner in a car capable of 1.0g is only a 56 MPH corner in a car that can pull 1.25g, but a pickup that can only pull 0.65g can still do 39 MPH and a sedan capable of 0.8g can go through this corner at 45 MPH. Just something to ponder when attempting to chase down slower vehicles on a twisty road or track.
Complicating matters is the tire "friction circle". If a tire might provide a max of 1g laterally and a max of 1g longitudinally, but it can't do both simultaneously; it can only yield about 70% (70.7% if we're being pedantic) simultaneously, or ~86% of one and 50% of the other, or any combination suggested by one's study of right triangles in 8th grade geometry. (And really, tires don't behave quite this perfectly, but it illustrates the point that to gain grip in one axis, we must give up grip in the other axis).
I'll save the lecture on slip angle vs. grip for another day, but that's also an important concept (especially once we consider its effects on the car-driver-road feedback loop).
Lateral acceleration (so-called "g's") is related to the corner radius and vehicle velocity (roughly the indicated speed), obviously. It's something like this:
A = v^2/r
Doubling the speed through a corner requires 4x the lateral grip from the tires. Assuming that the speed limit is posted for a lateral acceleration of 0.25g (typical a safe assumption for interstates; back-country roads are a whole 'nother story), doubling the posted limit takes about 1.0g. Go into a 25 MPH corner at 51 MPH with a setup that is only good for 50 MPH, and you're going to be short about 4% of the grip required. Might turn into a long day if there isn't enough room to scrub off a bit of excess speed.
Interestingly enough, this hypothetical 50 MPH corner in a car capable of 1.0g is only a 56 MPH corner in a car that can pull 1.25g, but a pickup that can only pull 0.65g can still do 39 MPH and a sedan capable of 0.8g can go through this corner at 45 MPH. Just something to ponder when attempting to chase down slower vehicles on a twisty road or track.
Complicating matters is the tire "friction circle". If a tire might provide a max of 1g laterally and a max of 1g longitudinally, but it can't do both simultaneously; it can only yield about 70% (70.7% if we're being pedantic) simultaneously, or ~86% of one and 50% of the other, or any combination suggested by one's study of right triangles in 8th grade geometry. (And really, tires don't behave quite this perfectly, but it illustrates the point that to gain grip in one axis, we must give up grip in the other axis).
I'll save the lecture on slip angle vs. grip for another day, but that's also an important concept (especially once we consider its effects on the car-driver-road feedback loop).
Or maybe the the 906 from the same era is more your speed. This one I’m told is valued at, “$32 million”. My guess is it probably is between there and $3.2 mil.
I hais no problem G.
The sad part is, 1G is where the trace maxes out, the instant digital values read to at least 1.3G, as that’s what I’ve been able to see at a quick glance.
Here the highway patrol has a map in their office with "critical speeds" for all marked corners. Some would surprise you how little error there is, while others are crazy high.
The correct answer is: when the tires tell you. They will start talking to you before they let go.
Some tires are quite communicative. Others very much aren’t.
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Was a general statement from the average in my AO in cars and on bikes.
Always some exceptions but the above was from first hand experience.
Sticky tires are great until they reach their limit.
Seems they go from talking to to damned late in a smaller envelope.
R
This is related to the comment I made on slip angle vs. grip. It takes some slip to generate any grip, and what happens to this relationship after peak grip is exceeded will determine how much warning the driver might receive before things go to shit.
Of course, there are a number of other factors that might influence this line of communication. My car has some performance driving modes that do an outstanding job of correcting minor driver errors, but a side effect is that warnings of impending doom are filtered. The result is an experience that goes from "wow, I'm fast!” to "why am I doing landscaping of the infield?" in the blink of an eye. Sometimes, it's just the tires, and there is rubber that will degrade from heart cycling in an unpredictable manner (like, they worked fine during a session an hour ago, but now feel like someone covered the track in grease).
This is good stuff to learn on a track, but not so fun to learn on public roads.
The HUD in my ZL1 is pretty damn close to reality. Of course, even watching it in the windshield is unwise while approaching the limit.
At 0.76g, you've got a lot of grip remaining, but it doesn't take large errors in corner entry speed to eat up that margin. Combine it with a puddle of fluid, a pothole, some gravel, etc. and things get potentially ugly.
Spending a few hundred bucks on a track day with a competent instructor is a great investment, just as is the case with learning any other complex skill.
I’ll agree that I can’t and won’t look at the HUD for longer than a glance. I can’t wait to take the car to the track and get some instruction.
We also haven't touched on trailbraking (major difference track vs street) or using the whole track. (on street this is not safe especially in blind corners)
Good discussion going, people are comparing track to street which is a totally different planet. If you are on street, you are not doing much braking going into corners, you are typically on a light throttle so your speed doesn't change much for the corner ahead. If you are on a racetrack, you go into corners as fast as your car or bike gets you there and you brake hard and deep (often to the apex) where you immediately go back to throttle and steer out of corner. So on a track you might be coming into a corner at 120, brake all the way to apex and when you let off brakes you are down to 60 so you were actually scrubbing speed, downshifting, and turning all at the same time through most of the corner.
Just something to consider when trying to compare the two. They are not even remotely similar and if you are driving/riding that way on street, you are going to crash or hurt someone very quickly. Those that have not raced (or done trackdays) don't understand that concept and are used to setting their speed up before a corner. The fast way through is actually scrubbing speed deep into the corner.
I used to race bikes, won a lot of class championships and was head coach of a riding school, but cars are very similar in a lot of ways. Bikes require using your body to turn though, it's extremely physical.
You would be amazed at what a moderately priced sports sedan or hot hatch can accomplish.
My daily driver is a '19 Accord Sport. There are some curves on the way to and from work that I can take at 20 - 25 over the posted limit staying in my lane and not endangering others. But I know those roads like the back of my hand, know where it's safe to push, know the safe line through them, know my cars very well.
There's a 60 - 75 degree left hander that has slight banking on my way home and it's posted 50. 75 through it is doable in my Accord on a dry road while staying 100% in the lane if you know the line to a late apex (which I do). I've had morons try to follow me at speed while taking the wrong line in. I always watch the mirror to see them desperately trying to scrub speed to stay on the road. If I had high performance summer tires (or better yet R compound tires) and could use the entire width of the road I bet I could push it up another 10 mph
ETA: As @atomic41 said, that was doing a near constant speed through entry, apex, and exit. NFW would I go through there like I would on a track.
I bet someone skilled in a real sports car can do triple digits safely through that corner.
Watch this to get an idea of what some average looking cars can do, and this was on the OEM touring tires......
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I run a lot stickier tires than what comes on your Vette if your on the factories. But I saw the 1.3G on a highway off ramp. Oops.
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Yep
I was in a vette that looked just like that a month ago.
Performed as stated.
Lambo, yes
Porsche, yes
Amg Merc, yes
It took me exactly 2 track days on a CBR600 to never ride public roads again. Haven’t been on two wheels on a public street in 10 years and I never will again. Definitely track and street are two totally different animals. For my vette, I’m not going to be able to afford a set of tires every month and multiple weekends on track, but I also don’t push it on public roads like I would on a closed course.
No I hate those factory run flats. It’s wearing Hankook Ventus K12(?) maybe K2. Can’t remember the designation now. Z rated summer tires. For me they are fine because I’m not acting a fool with it, mostly. LOL that car impresses me, especially after I did heads, Intake, exhaust and tune. Again, I’m certain I’ve never pushed it close to its limit of capability.
I've seen that same story play out a million times. Most people that start trackdays or especially racing quit street riding. You can never really have fun on the street again after you've had a taste of the racetrack.
It also makes you feel really unsafe on the street after the track.I was pretty much burning up a set of Bridgestone RE-71R each track day. In 215/45/17 they’re under $700 Canadian, but still. I switched to Hankook R-S4 for their supposed longevity last summer. They do take more time to come up to temp, which is fun, but I never got them to the track because of Covid. They’re a step or two more capable than the V12.
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I've seen that same story play out a million times. Most people that start trackdays or especially racing quit street riding. You can never really have fun on the street again after you've had a taste of the racetrack.
I haven't done a track day in about 30 years due to many reasons, but in the late 90s I autocrossed heavily to get a taste of the fix.
I have a beater Honda Fit that my kid uses now but I might strip it and turn it into a fun car once she goes to college next year. I won't cry too much if I wreck it.
Man that's awesome, do it. I retired from racing bikes and coaching a few years back, but missed the track so I bought a WRX for trackdays and a fun daily driver. I'm having mechanical issues (below) so I haven't tracked it yet but will be. I do miss the track!
Mechanical issues long story made short = Had the motor out due to warped heads (you have to remove it for heads), rebuilt heads, replaced a ton of stuff, put it back in and still have a problem so I think I have a cracked block. Poor car is just sitting, I'll probably buy a built short block or just a whole built motor...not sure.
Are you using the whole road or just your lane? Big difference. I'll say this, if your "normal" car is in proper working condition it'll take that "40" mph turn a hell of a lot faster than you think it will provided the person behind the wheel has the talent.
When I first started driving track events, I got my ass handed to me by a HONDA CR-X and a NISSAN Maxima - and I had the sport's car. Frankly, any car made since 2010 SHOULD be able to almost destroy my vintage sports car. The real problem is the braking systems of almost all cars today are just not equipped for repeated torture - even things like a 911 (unless you get a GT3) and Corvette likely need to have brake cooling ducts installed.
My PSA is that any modern car, if you're even at 70% of the true limit of the car you probably need to spend the night in jail.
That's why I cannot warm up to these Porsche's with no dry-sump (yes, I know..."it's integrated now."). May Metzger's engines reign supreme
. Yeah...air cooled still kick ass for that very reason of dry sump. Granted, one could upgrade to a GT3 . Granted, I lust after a 2014-2016 Cayman S.I remember watching 944's spin bearings all the time on #2 because of oil starvation. They seem to have solved that in the 968; but then again, there were not a lot of those in USA let alone the track.
There are several variables when it comes to handling. Suspension, weight balance and the tires. Then you have the driver ability and knowing the car and how it responds or how hard you can push it. I used to build road race cars and off road race trucks. Totally different applications, but each have the same dynamics when it comes to speed and handling. A simple set of really good tires can make a huge difference when comparing the same car for example. I see a lot of people cheap out when it comes to buying replacement tires. Some tires with the same ratings simply do not work as well as others on the same car.
Driving a high performance car is very different from a truck/SUV. A lot of the modern vehicles have a lot of computer control to assist with keeping the car stuck to the road. It can modulate the brakes and the throttle to control it. It takes some of the fun out but there is no denying the computer can do things faster to prevent you from fucking up really bad. You can still be dumb and go beyond the limits and wreck. In some cases it can actually make the car go around a track faster in testing.
There are also differences in rear engine, rear drive cars vs. front engine rear drive or AWD. There is also the mid engine cars which I have very little experience with. They all differ because of where the weight is and how the car responds when braking/accelerating and turning. Oversteer and understeer can be issues depending on the setup. I prefer a slight understeer personally.
No matter what, any of the performance cars will go through the turns better than your Suburban. The most important thing outside of driver ability is good brakes and good tires. Then you need good seats to keep your ass planted when slinging weight around at speed.
Driving a high performance car is very different from a truck/SUV. A lot of the modern vehicles have a lot of computer control to assist with keeping the car stuck to the road. It can modulate the brakes and the throttle to control it. It takes some of the fun out but there is no denying the computer can do things faster to prevent you from fucking up really bad. You can still be dumb and go beyond the limits and wreck. In some cases it can actually make the car go around a track faster in testing.
There are also differences in rear engine, rear drive cars vs. front engine rear drive or AWD. There is also the mid engine cars which I have very little experience with. They all differ because of where the weight is and how the car responds when braking/accelerating and turning. Oversteer and understeer can be issues depending on the setup. I prefer a slight understeer personally.
No matter what, any of the performance cars will go through the turns better than your Suburban. The most important thing outside of driver ability is good brakes and good tires. Then you need good seats to keep your ass planted when slinging weight around at speed.
I have seen Miatas faster than Corvettes on the track. It's always funny to me because the Corvette owners on track can never drive. Either can the Porsche drivers, lol.
I drive a 2013 Mustang GT throttle limit to get only Max 371 RWHP and Average 367 RWHP. Still a blast to drive. I have training with my coach tomorrow and a race next weekend. I gave up on trying to be fast in my SUV or truck.
I drive a 2013 Mustang GT throttle limit to get only Max 371 RWHP and Average 367 RWHP. Still a blast to drive. I have training with my coach tomorrow and a race next weekend. I gave up on trying to be fast in my SUV or truck.
Then brakes. Then damping. Then more driver mod. THEN power.
You have to make an exception to your 'Porsche driver's cannot drive' implication. Turbo drivers definitely cannot
and neither can Porsche owners with those foo-foo coil spring things....real men have torsion bars (unless it's a Turbo !!
I would say for driver mod that HPDE instructors do not help and actually hurt. They are trying to be safe and not making race car drivers. If you want to learn how to go fast hire a pro race driver.
Thanks, I built that bike up from a bare frame. It is definitely a blast to pilot around a closed course.
I am 100% in my lane - tend to ride the white line and create a little extra space between myself and the on coming log truck that is getting paid by the load. I'm sure that someone with some real training could hustle that 6k GVW pig with M/S rubber through a 40 mph corner at closer to 55 or so - but (to me) when the pig breaks loose, its a handful. Gathering it up on snow and ice is easy as you can feel it start to slip and then break loose; whereas wet/dry pavement - it is more sudden and violent.
Interesting that modern sports cars are as capable as they are - thank you all for the education.
I had a 7 series and aside from that I can not say that I have owned anything that was really contemplated, let alone designed to go fast (over 80) or hold a corner. I remember taking the 740i over the same road in the rain (w/ like some Michy Comfy sedan tires) coming into an uphill corner out of a vehicle pass and having the traction control come on - I did not like that. That was another pig - but a much more 'drivable' pig than my Chebby, and way more so than my UZJ100 - which I have no interest in going over 80 in - esp with my pizza cutter mudders.
