A very dumb driving question....

[ghayes420]

As a rather new Viper owner I have a question about shifting. I usually drag race and I am not to familiar with track racing. Here is my very elementary question:

At good speed (55-90, say 3rd gear) Is it safe to downshift or upshift while in a turn? Simple question I think. Let the flaming begin...

 

[syldogRT/10]

Well it really depends. If you are full out racing you really don't want to down shifts while in the Apex of a turn as you will load the front end and the under steer could cause you to lose traction. YOu are better off setting up before you enter the turn, as the old saying "carry your speed out of the turn, not into it". Now if you're just streeting it around you can shift when ever you like if you find yourself in the wrong gear.

 

[ghayes420]

Thanks sly. I am talking about really spirited driving at around speeds of about 80-120mph going around a twisty track. Your explanation of not downshifting when racing in a turn pretty much explains it. I did it today and the rear jumped out slightly and I recovered quickly. I was just wondering if that was common physics. Thanks.

 

[Chuck 98 RT/10]

At good speed (55-90, say 3rd gear) Is it safe to downshift or upshift while in a turn? Simple question I think. Let the flaming begin...

Upshifting in a turn is not much of an issue as long as the driver knows how to squeeze the pedal. Most drag racers slam the pedal rather than squeeze it.

Down shifting from 3rd to 2nd at 55mph won't get you in too much trouble but you should know what you're doing.

Down shifting from 3rd to 2nd at 90mph you REALLY better know what you're doing.

 

[Tom F&L GoR]

A downshift in the middle of a turn (or even just letting up on the gas pedal) will act like applying rear brakes only (unless you've heel-n-toed and matched RPMs) and the now-extra rearward traction applied will take away from the side traction needed in a turn (i.e. tires will stay inside their friction circle.) With less available side traction, the rear tires will slide sideways and you loop the car. It's called trailing throttle oversteer.

 

[CitySnake]

It's called trailing throttle oversteer.

This is nototious with Vipers.

 

[RX VIPER]

Try to down shift before the turn, as the weight transfers to the back during the shift and it's much harder to control. Also, your ready to accel from the lower gear when coming out of the turn.

 

[Tom F&L GoR]

Well, I'm not too sure how much weight transfers to the back during a shift under deceleration, but the momentary changes in tire load are worth mentioning.

Under braking, the rear wheels are being slowed by the calipers. The rear wheel is being driven by the momentum of the car and also of the drivetrain. Depending on the engine speed, rate of deceleration, flywheel, etc, the brakes may be also be slowing down the engine or the engine may be helping to slow the car. The latter is true in city driving, but not necessarily true on the track.

Consequently you may be threshold braking and when you depress the clutch, you may lock up the rears because now they don't have to slow the engine. (I know, given the weeny brakes in the back of a Viper, you've probably never heard of this.)

And we need to do some math - downshifting to 2nd at 90MPH is putting the engine right around the fuel cutoff RPM, which means you will definitely approach the landscape in a rearward fashion.

 

[KepRght]

do your shifting before the tight turns you want to be rolling on the gas through the turns not shifting, unsettling the rear end will cause a spin.

if you find yourself going to fast in a turn while rolling on the gas to keep the rear planted use your left foot 'slightly' on the brake. try it out first somewhere safe

 

[ghayes420]

Thanks for all the tips fellas. And thank you for defining Trailing Throttle Oversteer, this is exactly what I was wondering about.