I remember reading something in a post about adjusting the angle of the steering box when building your frame. Is this something that needs to be done, and if so, how do you figure the correct angle?
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I remember reading something in a post about adjusting the angle of the steering box when building your frame. Is this something that needs to be done, and if so, how do you figure the correct angle?
Location and angle of the steering box affects bump steer.
I have always set the box at the original locator "tits" on the axle beam, the angle has always looked nearly in line and the rag joint takes up the very minimal difference.
there are two positions to the stock steering gear, by reversing the clamping bracket you get a position for ghia (lower angle) or beetle (higher). the clamp has a notch which is in a different location on either side.
scott lyons
scott lyons
That's right.....and if you use the position for a Ghia, it's pretty darn close to what you need for a Speedster.
gn
gn
If I install a rack and pinion unit on my car is bump steer a problem? What is it anyway? Darryll
Well, I was gonna let this one pass, but here goes:
The angle and location of the steering box won't make any difference in "bump steer" on a properly set up front end. There, I've said it.
"Bump Steer" is a phenomenon whereby, when one front wheel goes over a bump it changes the front-end geometry and will cause the steering wheel to swing slightly towards or away from said bump, hence, the term, "bump steer".
The cause for this is (usually) poor front end alignment due to either a sloppy alignment or wrong setting values used, un-compensated geometry changes (dropped spindles), wear of front end components or damage to front end components (bent tie rods or tie rod ends, bent pitman arm and so forth).
If you install a new or good rebuilt steering box in either the beetle sedan position (up) or Ghia position (down), depending on where you want the steering column to go, with or without dropped spindles and then have a knowlegeable front end alignment person set it up, you should not experience bump steer.
So how, with all the various pan or frame based chassis configurations out there, is said "alignment guru" supposed to know what to set it at?
If it is a pan-based car and you know the year of the pan, tell him that year and have him set it for a Beetle or Ghia from that year. If you have a frame-based car, like an IM or Beck, then get the alignment setting info from the manufacturer and pass it along to the alignment guy (or gal) to properly set it up.
For instance, I have a 1969 VW pan with a lowered front end, but NO dropped spindles. I added caster shims behind the lower torsion tubes and told the alignment guru to set it up as a 1969 Beetle Sedan. Turned out just fine. If I had an IM, I would have had to get the alignment info from IM to give to the alignment guy, who does all the work.
Now, what about a rack and pinion system? Ain't no big deal.....all an R&P does is replace your steering box with something that acts the same, from the front end geometry point of view, but is a bit more precise in doing so. All either a "normal" steering box or an R&P unit does is move the tie rods back and forth in unison to make the front wheels turn more-or-less the same amount at the same time (depending on the rest of the steering components).
Again, the geometry and alignment specs are pretty much the same, whether you're running a steering box or R&P. What WILL change are the lengths of the tie rods - they'll be different on an R&P set-up (probably shorter, due to the configuration of the rack), but that should be considered and designed in by whomever is installing your R&P unit. All they really have to do is center the rack and then measure from the rack ends to the tie rod attach points at the wheels and get tie rods that are centered at that distance (they're adjustable in and out, so you "center" them to allow adjustment). Once that's done, then the alignment can proceed to the same specs as mentioned above.
Hope this helps......gn
The angle and location of the steering box won't make any difference in "bump steer" on a properly set up front end. There, I've said it.
"Bump Steer" is a phenomenon whereby, when one front wheel goes over a bump it changes the front-end geometry and will cause the steering wheel to swing slightly towards or away from said bump, hence, the term, "bump steer".
The cause for this is (usually) poor front end alignment due to either a sloppy alignment or wrong setting values used, un-compensated geometry changes (dropped spindles), wear of front end components or damage to front end components (bent tie rods or tie rod ends, bent pitman arm and so forth).
If you install a new or good rebuilt steering box in either the beetle sedan position (up) or Ghia position (down), depending on where you want the steering column to go, with or without dropped spindles and then have a knowlegeable front end alignment person set it up, you should not experience bump steer.
So how, with all the various pan or frame based chassis configurations out there, is said "alignment guru" supposed to know what to set it at?
If it is a pan-based car and you know the year of the pan, tell him that year and have him set it for a Beetle or Ghia from that year. If you have a frame-based car, like an IM or Beck, then get the alignment setting info from the manufacturer and pass it along to the alignment guy (or gal) to properly set it up.
For instance, I have a 1969 VW pan with a lowered front end, but NO dropped spindles. I added caster shims behind the lower torsion tubes and told the alignment guru to set it up as a 1969 Beetle Sedan. Turned out just fine. If I had an IM, I would have had to get the alignment info from IM to give to the alignment guy, who does all the work.
Now, what about a rack and pinion system? Ain't no big deal.....all an R&P does is replace your steering box with something that acts the same, from the front end geometry point of view, but is a bit more precise in doing so. All either a "normal" steering box or an R&P unit does is move the tie rods back and forth in unison to make the front wheels turn more-or-less the same amount at the same time (depending on the rest of the steering components).
Again, the geometry and alignment specs are pretty much the same, whether you're running a steering box or R&P. What WILL change are the lengths of the tie rods - they'll be different on an R&P set-up (probably shorter, due to the configuration of the rack), but that should be considered and designed in by whomever is installing your R&P unit. All they really have to do is center the rack and then measure from the rack ends to the tie rod attach points at the wheels and get tie rods that are centered at that distance (they're adjustable in and out, so you "center" them to allow adjustment). Once that's done, then the alignment can proceed to the same specs as mentioned above.
Hope this helps......gn
WOW!....thanks
I second that WOW!....thanks Gordon. Can a late 60's pan be properly aligned with the drop spindles or should one steer away from them. Pun intended. Darryll
Dropped Spindles.....hmmmmm..........
In theory, dropped spindles allow you to drastically lower your car without otherwise altering the front end geometry.
I say "in theory", because it all depends on how (and how well) those dropped spindles are made and how true they hold to the caster/camber lines that the VW designers had in mind for their car.
To make this short (Kathy just told me to get off here 'cause we're supposed to be running errands); if you use a well designed and built dropped spindle assy, and the tie rods are of adequate length to allow the alignment guy to do a proper adjustment of everything to the specs for that year and model that you've chosen, you shouldn't have any problems.
The two problems I've seen with dropped spindles are: (1.) setting the car too low (all around, but especially in the front for that "rakish look") and then having clearance problems when it bottoms out on bumps or hits just about everything in the road bigger than a walnut (often, the tops of the front tires hit the top inside of the fender), and;
(2.) getting the proper-length shock absorbers spec'd and mounted so as not to bottom out a shock first (many of those shocks are too short for the application travel and can bottom out either up or down or both). After you figure out what length shock to use, then you have to decide on a damping rate (amount of resistance to movement required) and, more often than not, there aren't a lot of choices available so it's difficult to get the right rate. That's why a lot of fellow Speedster owners use older, softer shocks on the front end - it's so light that you don't need a lot of damping for a good ride.
Munroe used to have a formula for figuring out damping rates for a given weight per wheel - maybe they now have that somewhere on a web site - don't know.
gotta run......gn
In theory, dropped spindles allow you to drastically lower your car without otherwise altering the front end geometry.
I say "in theory", because it all depends on how (and how well) those dropped spindles are made and how true they hold to the caster/camber lines that the VW designers had in mind for their car.
To make this short (Kathy just told me to get off here 'cause we're supposed to be running errands); if you use a well designed and built dropped spindle assy, and the tie rods are of adequate length to allow the alignment guy to do a proper adjustment of everything to the specs for that year and model that you've chosen, you shouldn't have any problems.
The two problems I've seen with dropped spindles are: (1.) setting the car too low (all around, but especially in the front for that "rakish look") and then having clearance problems when it bottoms out on bumps or hits just about everything in the road bigger than a walnut (often, the tops of the front tires hit the top inside of the fender), and;
(2.) getting the proper-length shock absorbers spec'd and mounted so as not to bottom out a shock first (many of those shocks are too short for the application travel and can bottom out either up or down or both). After you figure out what length shock to use, then you have to decide on a damping rate (amount of resistance to movement required) and, more often than not, there aren't a lot of choices available so it's difficult to get the right rate. That's why a lot of fellow Speedster owners use older, softer shocks on the front end - it's so light that you don't need a lot of damping for a good ride.
Munroe used to have a formula for figuring out damping rates for a given weight per wheel - maybe they now have that somewhere on a web site - don't know.
gotta run......gn
I suspect that "bump steer" did not even exist in the Porsche lexicon back when the VW suspension was invented. With the existing VW design, it it IMPOSSIBLE to eliminate it. Bump steer is a fundamental part of the steering/suspension design.
To eliminate bump steer from a beetle front end one would have to design and fabricate new steering arms for each side of the chassis. Each separate steering arm would need its' inboard pivot to reside in the same imaginary plane as the attachment point of the front trailing arms to the torsion beam. Then as the trailing arms rise and fall, the steering arm pivots with it, and does NOT otherwise pull on the spindle. Of course both these left and right steering arms must be connected by a tie rod and suitable pivots. Actually every common Chevy or Ford has this design down pat. VW did not.
Solution? Put in the biggest anti-roll bars you can. If the body can't roll, you limit bump steer effect to the occassional hole in the road.
To eliminate bump steer from a beetle front end one would have to design and fabricate new steering arms for each side of the chassis. Each separate steering arm would need its' inboard pivot to reside in the same imaginary plane as the attachment point of the front trailing arms to the torsion beam. Then as the trailing arms rise and fall, the steering arm pivots with it, and does NOT otherwise pull on the spindle. Of course both these left and right steering arms must be connected by a tie rod and suitable pivots. Actually every common Chevy or Ford has this design down pat. VW did not.
Solution? Put in the biggest anti-roll bars you can. If the body can't roll, you limit bump steer effect to the occassional hole in the road.
And after you figure out bump steer. Take a look a akerman steering.
(Which has changed from the design spec. when the pan was shortened)
www.auto-ware.com/setup/ack_rac.htm for definition.
Greg B
Just thought I'd throw that in to make you go hmmmmm....
(Which has changed from the design spec. when the pan was shortened)
www.auto-ware.com/setup/ack_rac.htm for definition.
Greg B
Just thought I'd throw that in to make you go hmmmmm....
Bump steer is when a change in wheel height relative to the chassis causes a change in toe setting. It happens in all cars to some degree, tie rod length and the vertical angle of the tie rod have a large effect.
The reason it happens is that a tie rod is a fixed length and as the wheel moves up the tie rod scribes out an arc and pulls the wheel in. The steeper the angle of the tie rod the greater the effect. To help visualize it imagine a tie rod at about 45 degrees for every inch the end moves up and down it moves in and out the same distance.
The way to reduce bump steer is to adjust the tie rods so that they are horizontal with the car loaded normally.
When you lower a car by adjusting the springs at the front, the wheels move up relative to the steering box/Pitman arm. This increase the angle of the tie rod making the bump steer worse. A potential fix is sold for this, marketed as a bump steer kit, it allows you to mount the out board end of the tie rod lower on the spindle.
Another possible fix for this would be to adjust the inboard end of the tie rod by moving the steering box or changing the pitman arm. The steering box is located in the correct position by welded tabs since it sees high impulse loads which could conceivably work loose bolts alone, causing sudden injury or death.
Dropped spindles are a much better way to go when lowering the front of the car since they don
The reason it happens is that a tie rod is a fixed length and as the wheel moves up the tie rod scribes out an arc and pulls the wheel in. The steeper the angle of the tie rod the greater the effect. To help visualize it imagine a tie rod at about 45 degrees for every inch the end moves up and down it moves in and out the same distance.
The way to reduce bump steer is to adjust the tie rods so that they are horizontal with the car loaded normally.
When you lower a car by adjusting the springs at the front, the wheels move up relative to the steering box/Pitman arm. This increase the angle of the tie rod making the bump steer worse. A potential fix is sold for this, marketed as a bump steer kit, it allows you to mount the out board end of the tie rod lower on the spindle.
Another possible fix for this would be to adjust the inboard end of the tie rod by moving the steering box or changing the pitman arm. The steering box is located in the correct position by welded tabs since it sees high impulse loads which could conceivably work loose bolts alone, causing sudden injury or death.
Dropped spindles are a much better way to go when lowering the front of the car since they don
Thanks, Bruce......That was excellent!
gn
gn
Daryll, are you still considering switching to rack & pinion or have you been bumped or steered off the road already. Trying to locate a decent R&P for a pan based VW is not an easy choice, there is no drop in replacement, and it will require some fabrication, like cutting & welding. All a little daunting and trying to minimize bump steer will be one consideration.
Do you have any R&P selected?
Bob
Do you have any R&P selected?
Bob
No Bob, I haven't. I haven't even located a car yet. I'm still putting together an assembly manual from this site. I must have four inches of paper in folders where I have printed most of Chris's build on this site and many, many of the threads from this site. I like to do all the grunt work prior to getting involved with a project. I once had a '58 MGA Coupe w/R&P and really liked it. It was the first car I ever owned. I was thinking about going to "Pull Your Parts" here in California, or what ever it's called and looking for a R/R unit and welding it on a pan. D-man
Darryll, fitting a rack in a VW pan car is a real brain teaser. Been thinking about it long and hard myself, not for my Speedy, but for another project of mine, a mid-engine VW autocross car that's still under construction and uses a VW suspension front & rear.
On a Speedy, you don't have much space under there to start with, unless you toss out the fuel tank, but then you can't get too far. The bug spindles are a rear steer style and most racks today are front, so not many to pick from, and propably a manual one just for simplicity, again less to pick from, and having the steering shaft on the drivers side is a big plus.
I'm almost to the point where I really don't see much wrong with the old reliable bug box.
Good luck with the search, it can be done, but it ain't that easy.
Boston Bob E.
On a Speedy, you don't have much space under there to start with, unless you toss out the fuel tank, but then you can't get too far. The bug spindles are a rear steer style and most racks today are front, so not many to pick from, and propably a manual one just for simplicity, again less to pick from, and having the steering shaft on the drivers side is a big plus.
I'm almost to the point where I really don't see much wrong with the old reliable bug box.
Good luck with the search, it can be done, but it ain't that easy.
Boston Bob E.