Tires or Gears

SST159 · 11-01-2014, 11:00 AM

Looking for some racer input.
Running a SBC 401 stroked 3.750 with 6" rod, 4.88 rear, 1.80 glide, 14/31 rear tire rolls out 98-99". Motor Dyno shows peak HP at 7100 rpm. Shift on time SST trim 2830 lbs.Currently going through traps 8K. I would like to drop the trap RPM to around 7600-7700. I need new tires so I believe my options are go to a 14/32 tire rolls out 102", or change gear to 4.56. What would you suggest?

Adger Smith · 11-01-2014, 12:13 PM

Tire for the first change.
If you change gear ratio it might upset it too much and you might have to end up with a 1.96 low gear in the tranny. Expensive changes. The gear is about a 7% change. 8,000 - 7% = 7,440
1.80 x 4.88 = 8.78 1.80 x 4.56 = 8.20
That is 7% diff in overall low gear.
See the 7% goes all the way back up the power train. It might even upset the stall or hit on your converter

Tom Goldman · 11-02-2014, 09:11 PM

Drew , if I remember correctly your current tires are only. 100" roll out .
I think the 104" tires will drop you 300 rpm from my experience .
You might get away on the .500 tree with the 4.56 gears , your car hits the tree pretty hard with the setup you have now , and you can drop the delay a little .
Give me a call this week .

SST159 · 11-04-2014, 09:55 AM

Thanks Guys for the advise and suggestions.
Tom, I will give you a call.

E MAN 1982 · 11-04-2014, 08:49 PM

Just dont touch that ET transmission! E

SST159 · 11-05-2014, 09:04 PM

E Man,
Don't worry I won't touch it.
The "ET" tranny is working flawlessly as always!!
Thanks for a great Job.!

11-01-2014, 11:00 AM	#1
SST159 Member Join Date: Jul 2005 Posts: 301 Likes: 4 Liked 18 Times in 12 Posts	Tires or Gears Looking for some racer input. Running a SBC 401 stroked 3.750 with 6" rod, 4.88 rear, 1.80 glide, 14/31 rear tire rolls out 98-99". Motor Dyno shows peak HP at 7100 rpm. Shift on time SST trim 2830 lbs.Currently going through traps 8K. I would like to drop the trap RPM to around 7600-7700. I need new tires so I believe my options are go to a 14/32 tire rolls out 102", or change gear to 4.56. What would you suggest? __________________ Drew Wonderly SST 159

11-01-2014, 12:13 PM	#2
Adger Smith VIP Member Join Date: Dec 2001 Location: Texarkana Ark/TX Posts: 2,355 Likes: 437 Liked 682 Times in 264 Posts	Re: Tires or Gears Tire for the first change. If you change gear ratio it might upset it too much and you might have to end up with a 1.96 low gear in the tranny. Expensive changes. The gear is about a 7% change. 8,000 - 7% = 7,440 1.80 x 4.88 = 8.78 1.80 x 4.56 = 8.20 That is 7% diff in overall low gear. See the 7% goes all the way back up the power train. It might even upset the stall or hit on your converter __________________ Adger Smith (Former SS)

11-02-2014, 09:11 PM	#3
Tom Goldman VIP Member Join Date: Jan 2003 Location: Allentown,PA Posts: 2,438 Likes: 779 Liked 703 Times in 206 Posts	Re: Tires or Gears Drew , if I remember correctly your current tires are only. 100" roll out . I think the 104" tires will drop you 300 rpm from my experience . You might get away on the .500 tree with the 4.56 gears , your car hits the tree pretty hard with the setup you have now , and you can drop the delay a little . Give me a call this week . __________________ Tom Goldman 1500 SG , 1506 STK

11-04-2014, 09:55 AM	#4
SST159 Member Join Date: Jul 2005 Posts: 301 Likes: 4 Liked 18 Times in 12 Posts	Re: Tires or Gears Thanks Guys for the advise and suggestions. Tom, I will give you a call. __________________ Drew Wonderly SST 159

11-04-2014, 08:49 PM	#5
E MAN 1982 Member Join Date: Oct 2005 Location: Boyertown, Pa. Posts: 120 Likes: 0 Liked 0 Times in 0 Posts	Re: Tires or Gears Just dont touch that ET transmission! E

11-05-2014, 09:04 PM	#6
SST159 Member Join Date: Jul 2005 Posts: 301 Likes: 4 Liked 18 Times in 12 Posts	Re: Tires or Gears E Man, Don't worry I won't touch it. The "ET" tranny is working flawlessly as always!! Thanks for a great Job.! __________________ Drew Wonderly SST 159