Question about going to track and switching out tire on 05 GT

Airborne2000 said:

Im running stock street tires that are 27" tall and when I go the track I want to have a set to switch out to, I going to get MTs that are 26" tall, is it going to hurt the car if I do not retune it to the proper size of the MTs while im at the track?

from what I understand the only reason to re-tune is for proper speedo calibration. can anybody shed some light on this for me?

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Why would you need to retune your car just for different tires?

Even if it does affect your speedometer it doesn't really matter if you just going to use them at the track.

No worries man, just get those Stickey Thompsons and let 'em rip!

302Feen said:

Why would you need to retune your car just for different tires?

Even if it does affect your speedometer it doesn't really matter if you just going to use them at the track.

No worries man, just get those Stickey Thompsons and let 'em rip!

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Good Advice GrassHopper.....:gringreen

I agree with the above.....:bigthumbsup

Won't hurt a thing!:bigthumbsup

Everything will be fine. You are correct (you did your homework) about the difference in overall tire diameter. The speedo will be affected but shouldn't matter since your only on the track. Ballpark 1" in tire diameter is equal to a .38 gear change. The smaller tire diameter will give you more dig off the line. You will most likely get a tire pressure warning light and chime. I have my drag radials mounted on extra wheels but don't have the sensors. This confuses the car's computer and give a warning message. I just clear it with the reset button. This is only a warning and doesn't effect anything else. Have fun with the new found traction.

Off topic but.... how do you like your shifter and do you actually shift the car going down the track?

I have just read alot of things about tuning when getting diffrent tires.

Thanks a Bunch for all the info!!

I have not ran the TCI shifter at the track yet but I have on the road just driving around and I really like it. It has good positive control of shifting with an auto.

Airborne2000 said:

I have just read alot of things about tuning when getting diffrent tires.

Thanks a Bunch for all the info!!

I have not ran the TCI shifter at the track yet but I have on the road just driving around and I really like it. It has good positive control of shifting with an auto.

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Does the shifter still keep the overdrive lock out button? (The button in the right side of the stock shifter t-handle).

FYI it is better to keep the car in D and let the computer to do the shifting when on the drag strip.

kazman said:

FYI it is better to keep the car in D and let the computer to do the shifting when on the drag strip.

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That may keep the shift points consistent....

correct if i'm wrong isn't the computer shifting below the powerband....

therefore putting the car in drive and pushing the gas pedal would results in slower times.....

RLG34750 said:

That may keep the shift points consistent....

correct if i'm wrong isn't the computer shifting below the powerband....

therefore putting the car in drive and pushing the gas pedal would results in slower times.....

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My '07 makes all shifts at 6000rmp (WOT stock shift points). I'm scared to rev the stock 4.6 any more that that. Any idea of the powerband or dyno chart of a stock car?

looks like the computer is shifting out of the power band

Power bhp 300 @ RPM 5750

Torque lb-ft 320 @ RPM:4500

kazman said:

Does the shifter still keep the overdrive lock out button? (The button in the right side of the stock shifter t-handle).

FYI it is better to keep the car in D and let the computer to do the shifting when on the drag strip.

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yup, the OD button is right above the "P"

Airborne - if you dont have a tune in the car, I'd recommend getting a Bama tune, Doug's auto tunes are near legendary!

kazman said:

My '07 makes all shifts at 6000rmp (WOT stock shift points). I'm scared to rev the stock 4.6 any more that that. Any idea of the powerband or dyno chart of a stock car?

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dont be IMHO, I pull mine to 6600-6700 @ the track w/ 10+ psi of boost!!! :bigthumbsup

RLG34750 said:

looks like the computer is shifting out of the power band

Power bhp 300 @ RPM 5750

Torque lb-ft 320 @ RPM:4500

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My stock tach might be off a bit. Old school rule was to shift slightly above the max hp RPM. This allows less RPM (better place in the power curve) loss in the next gear. Really need a dyno chart to see the where the shift points put the car in the next gear.

Airborne2000 said:

yup, the OD button is right above the "P"

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Thanks. I have to look into this shifter. Seems like its something I can use. Price on Jegs is under $350.

stkjock said:

Airborne - ...dont be IMHO, I pull mine to 6600-6700 @ the track w/ 10+ psi of boost!!! :bigthumbsup

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I bracket race so I really don't have to push my car that hard. There is really no benifit for me to pound the car to pick up even 3 tenths.

kazman said:

I bracket race so I really don't have to push my car that hard. There is really no benifit for me to pound the car to pick up even 3 tenths.

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Sure there is. You could move up in class! :bigthumbsup

TheKurgan said:

Sure there is. You could move up in class! :bigthumbsup

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I bracket race in Street (19.99-11.50) and Pro (15.99-9.0). My car runs 13.50's to 14.50's depending on the weather. No real benifit in writing a 14.0 on the window instead of a 14.30.

kazman said:

I bracket race in Street (19.99-11.50) and Pro (15.99-9.0). My car runs 13.50's to 14.50's depending on the weather. No real benifit in writing a 14.0 on the window instead of a 14.30.

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Gotchya. Here, the brackets are a little closer. 9.50, 10.50, 11.50, etc