square rear vs square wheelbase

[imca37]

Ok I'm not sure what to do. Rear end is squared off the motor plate 72 1/4 both sides. Plumb bobbed it, drew the lines and all that jazz. All is good there. Then when I measure the wheelbase from center of spindle to center of rear end, the left is 111 3/4 and right is 110 1/4. Any ideas or suggestions?

[hall99]

the only way you can square off of the front end is to set your caster and camber the same on each side. I usually square off of the manufacture recommendations, ex. motor plate, 4 bar plates, etc... Have also squared of off the front cross member of late models. You will also find out how much built in steer you car has... good to know.

[imca37]

Caster and camber is set. Caster is +6 right and +2 left and camber is -4 right and +3 left. Are those settings gonna change the wheel base? It's and old Harris so maybe it has a turned stub of about a 1/2 inch. So the real questions is do I just leave it or do I adjust rear links to to make even?

[twisterf5]

Caster and camber is set. Caster is +6 right and +2 left and camber is -4 right and +3 left. Are those settings gonna change the wheel base? It's and old Harris so maybe it has a turned stub of about a 1/2 inch. So the real questions is do I just leave it or do I adjust rear links to to make even?

yes the + caster on the right sets the wheel back compared to the left. you can not go off wheel base just square the rear and you will be fine as long as your front mounts are ok and lowers are both the same.

[HEAVY DUTY]

Don't measure the wheelbase. Most cars have the stub turned, as well as the tires offset in or out from front to rear, which will give you false measurements.

[JustAddDirt]

111 3/4 left to a 110 1/4 right is way too short on the right wheelbase.
what if you took a framing square, and had one side of angle on floor, and the other against the rearend. Take a tape measure, and hook the front on the lower ball joint grease zerk and measure back to framing square.
do that on both sides and see what you get numbers wise.

[Duckhnter83]

Some say go off the motor plate. Some say go off lower grease zerks on lower a arms. Some manufactures give you measurements from one point. But the question is what do you want the rear squared to if you don't have a manufacter notes. The motor plate? The chassis? Or the front end? I use the motor plate rather that's right or wrong it works for me.

[imca37]

Ok I measured from the grease fittings to the hole in the frame according to imca.com and measurement was 1.25 inches shorter on the right than the left and it didn't matter what hole I measured from. All measurements were 1.25 inches shorter on the right. I replaced the right lower A arm mid season last year with an A arm bought from SPEEDWAY. So now what? Go get a left lower from SPEEDWAY? Go to the junk yard and try and find a stock lower for the right? Or leave it and run it as is? If left as is what do I do to compensate? Thanks stock car driver for the measuring reference

[drtrkr244]

yes the + caster on the right sets the wheel back compared to the left. you can not go off wheel base just square the rear and you will be fine as long as your front mounts are ok and lowers are both the same.

Every car that I have checked,the wheelbase lengthened when more positive caster was set. Generally, every 1 degree of caster caused the wheelbase to increase 1/4 to 1/2 inch.

[HEAVY DUTY]

Every car that I have checked,the wheelbase lengthened when more positive caster was set. Generally, every 1 degree of caster caused the wheelbase to increase 1/4 to 1/2 inch.

Not possible, unless you are running a strut rod car and are putting caster in by pulling the lower a frames forward. You might be reading the caster wrong. If you add caster by moving the upper balljoint back, the spindle pin has to move back although by a smaller amount. If you have pos caster, the upper balljoint is behind the lower, and negative means the upper balljoint is in front of the lower. If you turn your front wheels the wrong way when zeroing your caster guage, it will read pos , when it is negative. I have seen gauges that you are supposed to turn the wheel back from center to zero, and some that you turn forward from center . Not trying to start an argument, just trying to help.

[imca37]

Thanks for the input from everyone. Now to the next question. Since I had to do a lot of moving the rear end backwards to get it square and the J Bar bracket is now more forward than the pinion. What is the correct or ideal difference you want the mounting points. Such as you want J Bar mount on pinion to be XX from the motor plate and want J Bar mount on chassis to be XX from the motor plate. Any ideas?

[drtrkr244]

Not possible, unless you are running a strut rod car and are putting caster in by pulling the lower a frames forward. You might be reading the caster wrong. If you add caster by moving the upper balljoint back, the spindle pin has to move back although by a smaller amount. If you have pos caster, the upper balljoint is behind the lower, and negative means the upper balljoint is in front of the lower. If you turn your front wheels the wrong way when zeroing your caster guage, it will read pos , when it is negative. I have seen gauges that you are supposed to turn the wheel back from center to zero, and some that you turn forward from center . Not trying to start an argument, just trying to help.

I always shimmed my lca forward to get more positive caster.They were stock with some modifications. I did not shim the uppers to prevent any binding. I ran into the same problem with the gauges when I switched brands.Be sure to read directions when buying a new gauge.

[JustAddDirt]

drtrkr244
do you have a eccentric on your lower a arm mounts?

[powerslide]

I would think that the Wheelbase on a harris should be around 110.

[drtrkr244]

drtrkr244
do you have a eccentric on your lower a arm mounts?

No, they were stock Chevelle. I welded a flat plate to the mounts and bolted a 5/8 heim. Then i made spacers to adjust the caster. Real simple but effective.ran it for years with no problems.