Alright.. so i searched and i kept gettig different answers for caster angle. I see anywhere from 4* - 12*. And do i want positive or negative caster? Negative is top of the axle is farther back than the top.. right? So what is a good rule of thumb to go by for caster? Just want to make sure before i weld the brackets on for good and then find out i messed up. Thanks, John
assuming this is a solid axle ford front end (you forgot to specify) Id aim at 6 to 8 degrees negative with the chassis sitting at the correct ride height front and rear, NOT parallel to the ground, as any chassis rake will reduce the caster angle.
You actually want positive caster, the top of the spindle tilted back from the bottom. Negative caster will give you handling nightmares usually. jerry
I wouldn't go any more that 5 or 6 degrees positive. Any more, and you won't be able to steer it. Positive caster is wiht the top of the spindle futher back that the lower part. This will give stability to staight ahead driving and returnability to center of the steering. Negative caster is the opposite. It makes for easy steering, but is not as stable. Think of it like a bicycle compared to a shopping cart. A bike has the forks laid back from verticle, top further back then the lower. This is what makes it possible to keep balance when riding as it's very stable. Now on the other hand, a shopping cart has negative caster. If you look at the wheels on the front of a cart, the top of the mount is forward of the axle the wheel rides on. This allows the cart to be easily steered with little input from the pusher. It also makes the art very unstable when someone takes a ride in one with no one holding on to guide it. Most cars use positive caster, around 2.5 to 5 degrees. there are exeptions, though. One that comes to mind is the early 4 seater T-Birds. There's so much overhang on the front, with alot of the front end weight forward of the axle centerline, that without some negative caster, you'd never be able to steer it, even with power assist. I hope this helps you out
Ok.. so from what i understand, I want the top of the axle tilted back between 4 and 6 degrees? And 1 more question. Model A wishbones are forged, not cast, right? Just asking b/c i think i may need more caster in the bones themselves so the brackets to hang down too low.
I would suggest closer to 6-7*. That's what we put in all of our drag race chassis and it has worked well on the street. If you were building a salt car or dragster to run over 175 mph, you would want more like 10* to increase straight line stability. Again, measured at ride height and weight. It is not uncommon to heat and bend the bones to adjust the castor. Remember that the spring should, ideally, have the same castor. Adjustable perches on the axle also help prevent binding. Al of this comes into play as you lower or modify the front suspension.
oops, i fucked up. i meant positive. and the bones.. they have forged ends, welded into hollow tube that has a seam welded down it. the best way to adjust the angle would be to cut through where the forged end is welded to the tube and reweld after adjusting the angle.make sure to chamfer well and get a good deep penetrating weld.
7 degrees would be fine. The main reason I said 5-6 is from exerience dealing wiht solid axle Jeeps. They spec at 6.5-8, and when set that far back on caster, the front end will hop when turning sharpley, especially at low speeds. They really do it bad when backing up. Originally, I thought it was just the 4x4 system causing it, until I had a 2wd version in and it did the same thing. Resetting the caster to around 4-5 degrees corrected the problem. It may not be as much of an issue wiht a rod though. And I do agree 100%, more caster is better, espesially at high speeds.
Don't cut all the way through the radius rod tube, rather, saw through to the bottom side of the rod leaving about 1/8" or so, the rod will bend to close up the gap, just the kerf of the saw cut might be enough to get your caster to the right place. It is difficult to get everything lined up when you cut the end all the way off and unnecessary too.
So if using a transverse spring up front, the mount/crossmember should also be at 6-7*. This was my thoughts too. Any one have any thoughts on why we often see suicide mounts at 0*? Seems like it would put lateral stresses on the spring pack.
Yeah.. i was just oing to pie cut it at the seam leaving the bottom still attached. And ill add a plate over the joint for a little xtra security. Well with the motor in the car, the mount will be at about 0* so ill just make a 7* shim just to even everything out. And with the mount being at 0*, i think its b/c of the same reason why mine is at 0*, dont account for the motor dropping the front end down. Now i should be able get my frame done finally. Thanks guys.
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