I know that some people have successfully re-slotted the front upper control arm shaft so the castor is increased for more directional stability. That means however extra work and weakens the part.

I know about complete redesigned suspension/steering front ends too. But these are expensive and change the original looks.

Given that a shaft only cost about 45$, is there any aftermarket shaft available that has this offset build in?

 

what year?
Bill

 

It's a 64

 

Moog makes one (offset shaft) that some of the corvette parts suppliers sell. It should be available from your local parts house too. It was originally intended as a collision repair part. I'll find the p/n and post it.

Harry

 

Moog K-6104

Harry

 

I had identified that one, however in the ads I read it says to increase CAMBER (see blue text) and not caster....Can someone confirm it increases CASTER too?By how much?

 

It does provide added caster adjustment range, if you don't change the camber (to more negative). Fewer of the shims will be used to achieve camber, leaving more space for shims used to add caster.

Can't tell you how much, though.

Harry

 

Why do you want to increase caster beyond what the factory provided?

 

The most important reason is that I like the engineering part of rebuilding cars, not in the least suspension and steering tuning.

We may tend to focus more on the engine because talking horsepower is kind of more 'real'. You would hardly impress saying that your C2 has '5° caster, 2° camber and 1° toe-out at the front', at least much less than when showing of with the 730HP LS7 you put in your car .

Now, the difference between a great DRIVING car and a less great driving car is not only about horsepower. Suspension, chassis and steering contribute a lot to the feel of a car.

Test driving my C2 revealed that directional stability is less than what I prefer (notice I said 'prefer', no statement about good or bad or right or wrong ). More caster is a way out of it, and that it will require more steering effort is no issue cause I go for Borgeson PS anyway

 

At one point I was talked into the mis conception that more is better when comes to castor. I have some tubular control arms on my car that allow for all sorts of adjustment. My mechanic was all excited to adjust to 7deg positive. I hated it. Lost all my nimbleness.
See what "Mr Corvette" recomends:
http://www.guldstrand.com/alignment.asp
No more than 3deg for me now ...

 

great data table, thanks. Would these data be different now that we have radial tires, although I will use original tire size?

 

It show the same specs for '63 to '82. I'm pretty sure those later ones have radials ...

 

I used to use 5-6 degs in my race car. Made it MUCH more stable at speed. I was using big slicks though. I remember at the factory settings it would wander around and was difficult to drive fast. The car was nervous and so was I !!!

 

I looked in on your posting on occasion and knew no one would give you the answer you probably needed. There are a few on here that could, but none of them helped you. I don't like getting into it with these idiots.
Basically yes you could slot the shaft at the two existing holes. Lengthing the wheelbase could basically improve straight line stability but then the turning ability deceases. Setting less wb makes it easier to turn but on the street that could be uncomfortable if taken too far which could be as little as a degree. Thus you could go in the direction with the castor for high speed and to tune for turning, put more camber into it. But it all depends on what you are doing. I paint shim sets and setting marks to tune for rapid track course set-up and then can put it all back in minutes.
For slotting I would use a mill, and if you are racing you could weld the original hole location which strength isn't really the reason why they are welded, people weld to plug the area so the shaft doesn't slip or slide from where you want it) and then clean everything up with a clean up mill of the newly slotted area, but no need for this on a street car to reweld. Thus leave the slot and just check that the shaft hasn't slid on you. I have cotter pins and lock wire in my bolts on the bushing ends and on the adjustment bolts to lock it all down. Also I have the Moog offset shafts to get that added camber, when using the del-um bushing, or I can throw the set of arms that has the concentric drilled solid bushing that act as a cam to set camber and some castor by turning the position of those, but I have the shaft slotted like you are looking to do. Plus I run a spreader bar and have bar stock that essentially reinforces and prevent flexing of the a-arm shafts based on using the adjustment bolts (bolts that hold the shaft to the frame and lock in the shims) for mounting.
Thus what you are talking about doing or needing to do is alot more sophicisated than trying to wiggle the arms with just shims to gain castor which is a bad design in that your camber will change automatically with the shim change. Thus slotting and sliding the entire arm by slotting shaft gives you practically any desired castor that you want.

Idiot- Endearing Term! Probably intelligent people but that just try to throw something in that generally doesn't answer your question or help you. Maybe they had good intentions, or maybe they are just trying to maintain their post count supremacy!

 

WOW ! Open mouth insert foot ! You better check your alignment book TC .

 

You are probably one of the guys that knows what he is doing, but you sure didn't share any beneficial details with the OP!

Also I didn't suggest any alignment setting specifically because I don't know his tire sizes, what parts he is working with, how much wheelwell clearance (side to side), etc, etc.! I Just talked as to how and why to slot the shafts for Castor.

You came up with a statement of how great your car was with more castor and how bad it was on factory settings. Thus give the guy your specs, tire sizes, and parts, and modifications that get you to the alignment settings that you shared. What G's are you pulling, so how much camber to put the footprint flat, what bars? what shocks? Etc.
The OP's question was looking for the detail just on slotting for castor, but it would actually help him get to where he wants if all of us smart people would just stop throwing out magical setting numbers that might not work on his set-up or he can't get too until the mods are done. Doing the slots, gives him more adjustability to eventual get to where he is good! Thus to fit all of this, you might need longer bolts on those crossshafts.

Ps Mr. Guldstrand has slotted shafts!!!!!!!!!!! He has a diagram or article where he is doing this for a Camaro set up, but the same principles apply to either a Corvette or Camaro. You can probably find that here on the internet.

Also for strength to prevent flex. If you can't run a spreader bar, you can still just use bar stock and stretch it down the length of the shaft after drilling two holes to prevent flex. Also large thick flat washers are effective in strengthening an area, put need to be locked down.

 

Well, some people may just have a less 'technical' approach to things than others. I am a very technical/engineering oriented person ( I am a designer and engineer, sorry), my posts are reflecting that.

Your post was certainly to the point of what I was looking for, thanks for that.

I do learn from all the different opinions and posts however, even those where I don't agree. I could not live with just one answer on a post

I like this forum exactly because it generates a multitude of opinions and convictions. Very often taste and personal preference are the base for this wide spread. The difference between a 'Racer' and a 'Cruiser' would induce very different technical solutions.

And about idiots? There is no reason why there would be none on this forum, there is enough of them in the outside world too. I would dare to say that there is proportionally less in this community, because our passion for Corvettes has a curing effect

And now about the caster problem. My plan is to do the slots, adjust the setting 1 degree at the time until I get the mid-high speed feel the way I want. I'll do all of that before putting in the power steering (Borgeson is the plan) so I have direct road feel for what is going on. Once set I will add the PS solving the 'no/slow speed muscles required' problem that gets worse with the caster increasing. I am not going to modify camber, I want to keep the original KO wheels/tires standing 'straight' .Makes sense?

 

Wow - glad I hadn't attempted to post a probably meaningless reply to this question. I would hate to be lumped in with all you other idiots who asked the year car and provided part information and part numbers. Dodged that one.

 

Well here's a non technical answer that might be helpful. Offset control arm shafts, without any other changes, i.e., number of shims, will move the upper ball joint outward from the center of the chassis and increase camber in the positive direction. You can increase positive caster substantially without changing camber by adding shims between the shaft and the frame at the rear bolt and removing an equal thickness of shims at the front bolt. Putting shims at the back bolt only will increase positive caster and will decrease positive camber.

The problem is that typical offset shaft changes camber by about 5 degrees positive. If your frame is dimensionally correct and your A- arms are not bent in any way you will need a LOT of shims to get the camber close to where it needs to be. It is entirely possible that you will run out of bolt before you can put in enough shims to get any reasonable camber adjustment and add the amount of positive caster you want. When you're done shimming, you at least want a couple of bolt threads extending beyond the end of the lock nut for safety reasons.

That is why slotting the bolt holes on the pivot shaft came up in the first place.

Been through this; I have offset A arms because my frame isn't quite as straight as if should be. I could have this fixed, but I'd rather have funny looking shim packs than risk a body crack getting the frame straightened. The car has about 2.6 deg + caster and 0.8 deg + camber on the driver's side with NO shims and an offset pivot shaft; the passenger's side has about 3.2 deg + caster and 0.8 deg + camber with a set of shims over an inch thick on the back bolt and none on the front. Car drives perfectly straight and has no tracking problems, but the back shaft bolt on the passenger's side barely sticks through the lock nut.

 

This is what I call a technical answer, cause it gives the reasonings, the problems and the eventual solution. Thanks, really helpful