[Czechman]

Okay, before you roll your eyes and be like "oh no, not THIS again" hear me out.

Whenever someone posts a 0-60 time in the high 4 second range it doesn't take very long before someone dismisses the time as false because of wheel spin.

Assuming that wheel spin is the result of a high 4 second run that means that the wheels lost traction just a few 10ths before actual 60mph. That doesn't seem feasible because, especially in a 6M because you can't go 60 in second gear. That means that at the very end of the power curve going nearly 60 mph the wheels spun? Not very likely. (Assuming stock rev limiter)

I'd like to see a video of a 0-60 run showing the timer and the speedometer so we can see if the needle jumps to 60 in those last 10ths of a second. So if you're getting very low 0-60 times and people are dismissing your claim based on wheel spin, let's see a video.

 

[USRWDV8]

Okay, before you roll your eyes and be like "oh no, not THIS again" hear me out.

Darn. I can't put my tinfoil hat down a second without someone, somewhere, reading my mind... :disgust:

 

[mikeychallenger]

I agree with you. Others have mentioned it too. Your 0-60 time will always be accurate as long as you are not spinning when the needle passes 60, which for most of us, is very unlikely. You can spin all you want off the line and as long as you're hooked up by 60, the time will be accurate. The problem is the time-to-distance like 1/8 and 1/4 mile times. Those will be affected by wheelspin.

Now, on the 2015 models, none of this should be an issue because it has been stated by the engineers who designed it that the readings are now taken from the front wheels. I think we still need to confirm that independently, but supposedly it is so.

Mike

 

[MuscleCarProf]

I've always thought that. How can my speedo inaccurately read 60mph when my wheels are no longer spinning (without traction I mean). By the time I've gained traction and and approaching 60mph it should be reading correctly. The R/T 5.7 has been road tested at 4.9 seconds for 0-60 as well...

 

[GeneJockey]

Well, since the 2015s now have the speedo sensor on the FRONT instead of the REAR wheels, if a bunch of 2015 R/Ts start posting times in the 4's, you'll know.

 

[Woz10]

On my old 6spd R/T, you shift into third shortly before hitting 60.

...so the rotational velocity of our tires is such that it is very close to 60mph linear velocity before shifting into 3rd. Spin them a little on your 2-3 shift and the rotational velocity of the tires increases during the spin to a point that it surpasses the linear velocity of 60mph and stops the timer...

This happened to me on more than one occasion resulting in 4.2-4.5 sec 0-60s. Vs the usual 4.9-5.2 also had a 4.81 once - don't know if it was real though.

Can't speak for the automatics.


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[MrIcky]

OP, not being able to make it to 60 in first is precisely why you spin the wheels. You get to 57mph, you shift to 3rd and get a little spin in the torque curve before you accelerate again. You're not "at the very end of the power curve". You are at the beginning.

Make sense?

 

[mikeychallenger]

OP, not being able to make it to 60 in first is precisely why you spin the wheels. You get to 57mph, you shift to 3rd and get a little spin in the torque curve before you accelerate again. You're not "at the very end of the power curve". You are at the beginning.

Make sense?

Since when do you need to shift to 3rd before hitting 60? The top end of second gear in the 6 speed should be 66 MPH. You should be able to hit 60 in second: 60 MPH should go by at 5800 RPM in second gear.

Mike

 

[Woz10]

On the 6.4L cars you're right mikey. Not on the 5.7L cars. I know from experience !


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[mikeychallenger]

On the 6.4L cars you're right mikey. Not on the 5.7L cars. I know from experience !


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Even doing the math on the R/T using a 5800 RPM redline, 18 inch wheels, the 235/55 tires, 2.1 second gear ratio and 3.73 rear axle ratio, I still come up with 62 MPH in second gear at 5800 RPM.

It's possible you are reaching 60 in second and there's just a little speedo lag that is making you think you don't hit 60 until you shift?

Mike

 

[Woz10]

Mine didn't have those options. 245/45r20 tires, 3.92 rearend. You could slam it full throttle in 2nd gear into the rev limiter then "coast" to 60. That's the only way the thing would hit 60 in 2nd gear stock. I don't believe many of them had 3.73 rearends. Ones that did I could believe would hit 60 in 2nd.

I raised the rev limit once with a tuner and then it would hit 60 in 2nd under power.


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[mikeychallenger]

Mine didn't have those options. 245/45r20 tires, 3.92 rearend. You could slam it full throttle in 2nd gear into the rev limiter then "coast" to 60. That's the only way the thing would hit 60 in 2nd gear stock. I don't believe many of them had 3.73 rearends. Ones that did I could believe would hit 60 in 2nd.

I raised the rev limit once with a tuner and then it would hit 60 in 2nd under power.


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245/45/20 with a 3.92 rear works out to almost identical shift speeds compared to 235/55/18 with a 3.73 rear. The above is why I said you might be hitting 60 in 2nd and not realize it. There's no way you can "coast" to 60 because there is no further acceleration if you lift or just bounce off the limiter. Maybe because you are right at the 60 mark, the timer needs to see a little more than 60 MPH to stop the timer... or it has to see at least 60 MPH for a fraction of a second or something.

That's interesting because you might actually hit 60 in 2nd but the timer needs to see just a little more to shut off, forcing you to shift to 3rd to get a valid 0-60 timer reading.

Mike

 

[waumo]

Now, on the 2015 models, none of this should be an issue because it has been stated by the engineers who designed it that the readings are now taken from the front wheels. I think we still need to confirm that independently, but supposedly it is so.

Mike

So they are saying on the 2015s the 0-60 timer speed reading is taken from the front wheel speed and the speedometer is taken from the rear?

 

[randycat99]

I think that is the problem, right there (for the pre-2015 models with speed sensing on the rear wheels)...it's such a close margin to hit 60 in 2nd, you either have the next shift timed perfect, or you hit the rev limiter, or you hit the next shift prematurely (by tenths of a second). In the latter scenario, that is when you may get just enough wheel spin upon re-engagement of the clutch w engine load, that the rear wheels momentarily read 60 mph (which triggers the timer stop).

So assuming you have the gear/axle/tire to mathematically reach 60 mph in 2nd, the only way you can take a valid (indisputable) test is to not leave 2nd gear. You may bang on the rev limiter by some degree, but the only recourse to completing a valid test is how late and how fast you can let off the gas, once 60 mph is reached (similarly, in a different car, time travel is achieved by hitting 77 mph). That ensures no wheel slip to throw off the measurement. As soon as you bang that gear into 3rd and power-clutch, a wheel slip event is going to occur. If it happened before 60 mph, then the measurement is wasted. If it happened after 60 mph, then all is good...however, the window for that to happen is exquisitely narrow.

 

[Woz10]

Mikey. I'll have to do the math when I'm not on my phone. 1/2" difference in those tire diameters and you're saying that the gear ratio difference puts them back at the same shift points ?

And yes you can coast to 60! Accelerate as fast as you can to 50mph then push the clutch in ... I guarantee you'll coast to 60mph!

I put 22k miles on my 6spd R/T with lots and lots of 0-60 runs with the timer. I can guarantee it hits the limiter a couple miles per hour before 60. Several times is hit the limiter and nose dived on me as I crossed the 60mph mark.


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["Charlene"]

Since when do you need to shift to 3rd before hitting 60? The top end of second gear in the 6 speed should be 66 MPH. You should be able to hit 60 in second: 60 MPH should go by at 5800 RPM in second gear.

Mike

Hehe... going wide open on the 8 speed 392 it'll shift into 2nd at about 36mph and then into 3rd at 55mph. 4th at around 80mph. 5th around 100.

 

[randycat99]

And yes you can coast to 60! Accelerate as fast as you can to 50mph then push the clutch in ... I guarantee you'll coast to 60mph!

That part puzzles me! If you're coasting, how can your speed increase? I'm not saying you did not experience what you experienced. I'm just wondering if there is more stuff going on than expected, for this to be possible.

 

[Woz10]

...it's called momentum. You have enough momentum that you overcome gravity and the friction between the road and your tires to continue to gain speed until they overcome. How smooth the road is will play into this as well.


Maybe from 50mph it may not be able to coast to 60mph...but from say 57 or 58 mph you are definitely going to coast to 60.

Same idea as throwing a baseball. You throw it using the muscles and motion of your body. It goes through the air speeding up until gravity and the force of pushing through air overtakes it. You only applied that acceleration force while it was in your hand. After that it's still speeding up from the momentum it had when it left your hand ... Until it is overcome by gravity. So it's coasting and speeding up right ?

...at least this is all sounding good to me after a few beers anyway ...

 

[randycat99]

Momentum cannot be the explanation. At best, you maintain your original speed via momentum. Your speed does not increase. More likely, you lose speed gradually from frictional losses bleeding down momentum.

This all comes back to a basic law of physics. An object can only increase speed when energy is applied to it. Once you cut the addition of energy, the object ceases to accelerate.

 

[Woz10]

...hmm...man now when I'm back in the office Monday I'm going to have to do physics homework.


I distinctly remember questions like this from physics in college 7 years ago.