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What Causes Tires to Chirp

  • Momentary lockup of the drivetrain when load is re-introduced

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  • Spinning of tires from power of engines rotating tires

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Discussion Starter #1
Okay.

THere's a thread on the other forum (motoring) about chirping gears. My understanding and thought is that in a manual car to correctly chirp gears you accelerate hard up to near redline and shift and dump the clutch (no power shifting by keeping the throttle applied, which is a "fake" or forced chirp.

Since the power is not being applied and you are introducing load back into the system there's no way it can spin the tires faster. You're dropping RPM and going into a lower gear. I know you can force the chirp by keeping the gas on but that to me is "rice" or the cheap way.

Another opinion was that it was the tires being spun faster when shifting, but again the power is techically off and there's no way my car is going faster without throttle.

So who here has the explaination. I don't think 5AT will do it the same way since you keep the throttle on during the shift, but I can almost see the chirp coming from lock up again.

So what do we think or know? I didn't want to post it on the other site because I'm sure the other side would interject.
 

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Well, not to go offtopic so soon, but I started noticing that ever since I got my new rims and tires (Nismo/Toyo t1s) when I downshift I get a chirp every once in a while. Not really going too fast either, just coming from say third to second from 4k in third to 5k- in second for engine braking. Happens randomly and very seldom, but it surprises me sometimes and I really dont know what the **** is going on when it does it.
 

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And out of the two choices above, one would be different than the other. The first one would be chirping due to a skidding, kind of like what I described above. Just using logic and physics (as well as actually having felt both ways) I can say that chirping while accelerating and switching through the gears is more of a loss of traction for a split second than a drivetrain lockup type skid. Thats my .02
 

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Discussion Starter #4
How do you lose traction if you're at or past PK RPM/TQ and down shift into a taller gear with less leverage? You see what I'm saying you're shifting off power and re introducing the drag of the engine again off-power. To me it seems impossible to accelerate the tires faster shifting into a gear that lowers RPM and off power.
 

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Let's see: If you are increasing velocity on the ground, momentarily 'slow' down and stop applying engine power to the wheels by shifting, then re-engage the power to the wheels as you are 'coasting,' dump the clutch and mash the gas, I think that you temporarily are reaching that point of torque or power which affects the rolling tires which, at the moment, has no power going to them.

I guess what I'm trying to say is that you are spinning the tires at the split second you engage the next gear up.
 

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Originally posted by SmoothZ@Jan 6 2005, 10:17 PM
Let's see:  If you are increasing velocity on the ground, momentarily 'slow' down and stop applying engine power to the wheels by shifting, then re-engage the power to the wheels as you are 'coasting,' dump the clutch and mash the gas, I think that you temporarily are reaching that point of torque or power which affects the rolling tires which, at the moment, has no power going to them.

I guess what I'm trying to say is that you are spinning the tires at the split second you engage the next gear up.

exactly :thumbsup:
 

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Yeah, if you drop the clutch right as you're applying power, you might be applying less power, but over a shorter period and shocking the wheels, which makes them break loose. Think it trying to push a really heavy object on a sticky surface: if you do it real slow, nothing happens, but if you give it a little jolt, it budges.
 

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Discussion Starter #8
The chirp isn't when you hit the gas but release the clutch. I don't think you are hitting the gas when you dump the clutch or you're doing the cheater way...apply throttle. Pay attention tomorrow when you try it and you'll see it can't...or at least I'm not seeing it. We need slow motion replay.
 

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Well, I guess it'd be the same if you were completely off the gas.. The sudden engine braking would have the same affect (just a sudden force in the ther direction)
 

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1st - 2nd chirp = more torque thats it, more torque as you go up the gears, 2nd gear has significant more torque than 1st.

3rd - 2nd chirp = extreme de-acceleration thus producing an impulse of skid.
 

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All about horses and foot pounds. Memories of my past flashing back! I had a '72 Duster, 4spd manual, 3.96 posi and a 340cid w/ a 650 thermo quad. She could BURN not chirp all 4 gears. Sometimes I do miss her, but at 4mpg and thirsty for 95+ gas, one expensive date!

A Hui Hou

PaulO
 

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Explanation torque, when you go into second (from 1st at high rpm)the motor gets back to the ultimate power or torque area, remember the zed hits peak at around 6400 rpm (power) & torque 4800 rpm (better measure as power is just a mathematical equation of the torque measure). So wheels lose traction because engine via drivetrain can spin the wheels. I think you could do it via clutch dump or power shift as long as you are changing gear from above that peak power rpm range!
 

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[/quote]


Peak torque is not obtained in every gear don't forget. Peak torque is achieved when the transmission has selected a gear that has the closest resemblence to a 1:1 unity with the motor. i.e. have you ever seen someone dyno a car in just first gear or just 2nd? No. It is usually in 3rd sometimes 4th where the peak HP and torque (though peak torque is usually a much flatter curve and developed relatively lower than hp) are developed, because the transmission and motor are at a 1:1 (not truly a 1:1, but as close as possible) unity. Think of it as a limit, as x approaches 0 (3rd gear maybe 4th depending on ring pinion etc etc).
 

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Fascinating!

Apparently, a good number of us try to make our tires spin while accelerating and shifting!

I'm not an engineer, but it seems to me that wheelspin = loss of speed.??

In other words, let's race! :shiftdrive:
 

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