changing setback

rrc · 4/17/08, 8:17 PM

If you were to change a sprint car setback from 40" to say 38.5 would you have to change anything on the chassis or would you do it by different length arms,torque tube and driveshaft? thanks

wobbler · 4/17/08, 10:32 PM

I would think that the jacobs ladder mounts would would prevent you from making this change?

rrc · 4/17/08, 11:23 PM

Yes, your right.If the mounts were moved, would that be all the chassis changes necessary?

LEADERS EDGE · 4/18/08, 4:23 PM

You would have to check your seat bar and seat location for clearance.
It cannot work right if it is banging the seat or seat bar and damaging the tube and center section.

Radius Rods are different.

Shock location and valving would have to be looked at as the longer arm would put it's relationship to the tire differently.

It's very doable for sure, but short cars can be very hard to drive in the rough or in the cushion. You can play with the height of a car and change it's roll center and create bite as well.

Is this just a project for fun or are you going to race it?

rrc · 4/21/08, 10:58 PM

I was looking at a chassis that this was done to and wondered just how original the frame would be considering the things that had to be moved or altered.

Larryoracing · 4/22/08, 6:21 PM

I was thinking about this problem the other day and just wondered
why not move the motor plate from outside the frame in the engine compartment to bolting it to the inside of the frame inside the cockpit,
behing the uprights. Then I would :Steerguess you would have to shorten the axel by about 1.5 inches?

Sincerely,

Larry Otani

dant · 4/22/08, 11:01 PM

Done it,most motorplates mount to a horizontal tube,when you move the motor plate from in front to behind the uprights, the upper horizontal tube has to be cut out or the engine would'nt mount flush to the motor plate.shorten the drive shaft,and check torque tube length.Like I said ,did it once would'nt drive the car on a 1/2 mi ,cockpit gets real tight around legs..good luck

tinkertoys · 8/22/08, 7:24 PM

does anyone ever notice that a lot of 360 winged sprintcars are 39'' motorplate cars. Also do you think they build 360's this way to hook them up? Just a little food for thought. before one does all the work. Also becareful when playing with arm length front or rear the spring rate changes are drastic if you look on a spring rate chart shock rate still stay's the same unless you change the pick-up point from the axle center line whether its a 38 or 42 inch car. 1200# is still 1200# however roll center can effect shock valving choice.

RR>LR=LTO · 9/5/08, 8:37 AM

First question is why? I raced 39" cars for a year or so and then bought a 41" car and my whole outlook on racing changed. The 41" car is so much easier to drive,set-up,and hook-up on a slick racetrack. I'd never go back.
Your Question: Move the motor, not the suspension. Move the motor from the front of the frame-uprights to the back, inside the cockpit. You'll havbe tyo shave some material off of the motorplate to get it to fit, but you'll be happier in the long run. Next, cut 1.5" off of your driveshaft and go racing. Good luck, you'll have to be pretty quick on the wheel to keep up with the racecar. The 38's and 39s react far quicker than the 40's and 41's.

4/17/08, 8:17 PM	#1 changing setback
rrc Member Join Date: Jul 2007 Posts: 237	If you were to change a sprint car setback from 40" to say 38.5 would you have to change anything on the chassis or would you do it by different length arms,torque tube and driveshaft? thanks

4/17/08, 10:32 PM	#2 Re: changing setback
wobbler Member Join Date: Jul 2007 Posts: 191	I would think that the jacobs ladder mounts would would prevent you from making this change?

4/17/08, 11:23 PM	#3 Re: changing setback
rrc Member Join Date: Jul 2007 Posts: 237	Yes, your right.If the mounts were moved, would that be all the chassis changes necessary?

4/18/08, 4:23 PM	#4 Re: changing setback
LEADERS EDGE Senior Member Join Date: Jan 2008 Posts: 980	You would have to check your seat bar and seat location for clearance. It cannot work right if it is banging the seat or seat bar and damaging the tube and center section. Radius Rods are different. Shock location and valving would have to be looked at as the longer arm would put it's relationship to the tire differently. It's very doable for sure, but short cars can be very hard to drive in the rough or in the cushion. You can play with the height of a car and change it's roll center and create bite as well. Is this just a project for fun or are you going to race it?

4/21/08, 10:58 PM	#5 Re: changing setback
rrc Member Join Date: Jul 2007 Posts: 237	I was looking at a chassis that this was done to and wondered just how original the frame would be considering the things that had to be moved or altered.

4/22/08, 6:21 PM	#6 Re: changing setback
Larryoracing Senior Member Join Date: Nov 2007 Posts: 380	I was thinking about this problem the other day and just wondered why not move the motor plate from outside the frame in the engine compartment to bolting it to the inside of the frame inside the cockpit, behing the uprights. Then I would :Steerguess you would have to shorten the axel by about 1.5 inches? Sincerely, Larry Otani

4/22/08, 11:01 PM	#7 Re: changing setback
dant Member Join Date: Apr 2008 Posts: 191	Done it,most motorplates mount to a horizontal tube,when you move the motor plate from in front to behind the uprights, the upper horizontal tube has to be cut out or the engine would'nt mount flush to the motor plate.shorten the drive shaft,and check torque tube length.Like I said ,did it once would'nt drive the car on a 1/2 mi ,cockpit gets real tight around legs..good luck

8/22/08, 7:24 PM	#8 Re: changing setback
tinkertoys Member Join Date: Aug 2008 Posts: 95	does anyone ever notice that a lot of 360 winged sprintcars are 39'' motorplate cars. Also do you think they build 360's this way to hook them up? Just a little food for thought. before one does all the work. Also becareful when playing with arm length front or rear the spring rate changes are drastic if you look on a spring rate chart shock rate still stay's the same unless you change the pick-up point from the axle center line whether its a 38 or 42 inch car. 1200# is still 1200# however roll center can effect shock valving choice.

9/5/08, 8:37 AM	#9 Re: changing setback
RR>LR=LTO Member Join Date: Oct 2007 Posts: 112	First question is why? I raced 39" cars for a year or so and then bought a 41" car and my whole outlook on racing changed. The 41" car is so much easier to drive,set-up,and hook-up on a slick racetrack. I'd never go back. Your Question: Move the motor, not the suspension. Move the motor from the front of the frame-uprights to the back, inside the cockpit. You'll havbe tyo shave some material off of the motorplate to get it to fit, but you'll be happier in the long run. Next, cut 1.5" off of your driveshaft and go racing. Good luck, you'll have to be pretty quick on the wheel to keep up with the racecar. The 38's and 39s react far quicker than the 40's and 41's.