Camber adjustment 300zx

[DavidM]

I've seen a camber curve somewhere of the Z32 and it was decent. I have the adjustable upper links on my TT as well as rear upper adjustable links. Nice and easy swap out and camber adjustment is easy, though not as easy as camber plates for a strut car. Eccentric bushings sound like a pain, but it is what it is.

David

[esuvee]

They use, I bet, eccentric bushings.

I believe some a-arm cars may have hit a very large speed bump on the way to the track as well. Pretty known quantity in SS and I'm guessing it migrated to IT.

Alex

[Tristan Smith]

I believe some a-arm cars may have hit a very large speed bump on the way to the track as well. Pretty known quantity in SS and I'm guessing it migrated to IT.

Alex

what????!!! somebody is "bending the rules" a little? I am shocked and dismayed. :eek:

[JeffYoung]

I wish someone would have accident with my car and bend the axle tubes up a bit. Just a bit.

[TomL]

Greg Amy -

I'm confused. Why do you say you can fix camber curves but not roll centers? On strut cars, the RC is determined by the angle of the strut and the inclination of the lower control arm. You can't do much with the former, but the lower control arm inclination CAN be changed through the use of the so-called "turn-in spacers". As you note, you can't change the inner pickup point, but since you can modify the strut with the spacers, you can accomplish the same thing at the other end of the control arm, i.e., changing the lower control arm angle and thus the RC location.

To me, the camber change curve with struts has always been the bigger problem, as in, having to run 5 degrees static camber.

[Greg Amy]

Tom, care to expand on these ""turn-in spacers"? If you're referring to spacers between the ball joints and the strut, or between the steering arm and the strut, and you're not actually modifying the strut itself, then these are not legal in Improved Touring.

For example, on my NX2000 the strut bolted to a cast knuckle (this design is typical for FWD Volkswagens as well). The ball joints and the tie rod end bolted to the knuckles. None of this geometry between the ball joints and/or the tie roads and the knuckle could be corrected legally within the IT ruleset. If you're implying spaces in these cases are legal, then you're mistaken. I sincerely hope you are not currently doing this in IT with the misunderstanding it's legal.

On the other hand, the ITB Audi Coupe has an all-in-one strut/knuckle assembly, where the strut and the knuckle assembly are one. In that case, since struts are free, you have a s**tload of latitude on how the toe rods and ball joints attach to the assembly (and it's a suh-weet setup, too).

Little more detail, please. Specific examples would be useful.

GA

On edit: I found the following after "googling" the term; scroll down for "turn in spacers":

http://www.gforceengineering.net/products.htm

Not being familiar with the Mazda RX-7 design, I cannot say whether this is legal as they claim. However, if the steering arm and/or ball joints do not attach directly to the strut - as is the case in most FWD McPherson strut applications - then these parts are decisively not "IT-legal". Jake? - GA

[TomL]

Greg -

You are correct. The term turn-in spacer seems to have originated with 1st Gen RX7s. For those not familiar, it's a spacer between the stock strut and the steering knuckle on the many cars that are built with the strut bolted to a separate steering knuckle. (I have an RX7 and a Nissan 200SX that are). I think is has been discussed here in the (long distant) past, but I thought most everyone agreed it's IT-legal, as long as you weld it to the stock strut, i.e., it's a "substitute strut" at that point. For your NX or VW, you are probably correct about roll canters. Sorry I forgot that there are other designs, particularly on FWDs. But for cars like the RX7 that come with struts and separate steering knuckles, would you agree that roll centers can be corrected?

[JeffYoung]

As I understand it -- and my understanding may be wrong -- these bolt to the bottom of the strut and fit between the strut and the lower a-arm. They are essentially a "bolted on" extension of the strut itself, and that is the argument for their legality.

Check this link for some pictures of an RX7 front suspension:

http://www.google.com/imgres?imgurl=...&ct=image&cd=1

Tom, care to expand on these ""turn-in spacers"? If you're referring to spacers between the ball joints and the strut, or between the steering arm and the strut, and you're not actually modifying the strut itself, then these are not legal in Improved Touring.

For example, on my NX2000 the strut bolted to a cast knuckle (this design is typical for FWD Volkswagens as well). The ball joints and the tie rod end bolted to the knuckles. None of this geometry between the ball joints and/or the tie roads and the knuckle could be corrected legally within the IT ruleset. If you're implying spaces in these cases are legal, then you're mistaken. I sincerely hope you are not currently doing this in IT with the misunderstanding it's legal.

On the other hand, the ITB Audi Coupe has an all-in-one strut/knuckle assembly, where the strut and the knuckle assembly are one. In that case, since struts are free, you have a s**tload of latitude on how the toe rods and ball joints attach to the assembly (and it's a suh-weet setup, too).

Little more detail, please. Specific examples would be useful.

GA

On edit: I found the following after "googling" the term; scroll down for "turn in spacers":

http://www.gforceengineering.net/products.htm

Not being familiar with the Mazda RX-7 design, I cannot say whether this is legal as they claim. However, if the steering arm and/or ball joints do not attach directly to the strut - as is the case in most FWD McPherson strut applications - then these parts are decisively not "IT-legal". Jake? - GA

[lateapex911]

Ahhh, Greg, who was it that said "It's a whole new world out there""??

Part of the strut.

[Greg Amy]

Got it. In that case, I'd agree that it's legal.

You have to understand that especially in the case of FWD it's very, very, very unusual to have struts like that. Most manufacturers, to improve production and decrease costs, will have separate strut and knuckle assemblies and the ball joints and and tie rods attach to the knuckles. The primary reason for this is that FWD knuckles also have to not only accommodate the strut, ball, joint, and tie rod attachments, but the drixe axle pass-through and wheel bearings assembly. Thus, it's much more cost-effective to build a separate casting (and it makes replacement struts very easy and cheap). In fact, with the noted exception of the Audi, I can't right off the top of my head think of another FWD car that does what's illustrated above...

Further note that if the tie rod and ball joint attach to the knuckle, changing the location of its attachment to the strut has zero effect on the suspension geometry; moving the strut up and down relative to the knuckle only affects the location of the piston rod and the position of its stroke within the bore. So, no geometry advantage.

I'd be all over redesigned front struts on the RX-7...and I even might go so far as to suggest it not get the strut subtractor... - GA

[TomL]

Greg -

It isn't bolted to the strut, it's welded. As Jake said, it's now "part of the strut", thus a making the new assembly a legal "substitute strut". The pictures you showed don't include the spacers, but if they did they would be attached to the bottom of the strut tube.

But back to the original question, I can see how on your design why you couldn't change roll centers. But another question is, how do you change the camber curves (significantly)?

[Greg Amy]

...how do you change the camber curves (significantly)?

By moving the top of strut strut around. Farther out = less camber gain, farther in = more camber gain. Keep in mind that camber change is not solely a function of the arm angle, but more that of the angle of the strut. Then you correct the static camber by adjusting the hub-to-strut angle.

Taken to an extreme, you can even design a strut that causes POSITIVE camber as the wheel moves up in bump... - GA

[JeffYoung]

You lost me on that last part. How do you do that on an IT car? You machine the spindle?

By moving the top of strut strut around. Farther out = less camber gain, farther in = more camber gain. Then you correct the static camber by adjusting the hub-to-strut angle. - GA

[Greg Amy]

You lost me on that last part. How do you do that on an IT car? You machine the spindle?

Keep in mind, Jeff, that most strut cars do not have integral hubs and struts, the above is unusual...so that bolting interface between the knuckle and strut is completely free. - GA

On edit: Here's a pic of a typical FWD strut:

http://www.kakashiracing.com/images/DCP_0968.JPG

[JeffYoung]

My experience is admittedly limited with strut cars -- basically the Z and mine.

The hub on my car slides on the spindle and his held there by the spindle nut -- same as a Z. I could see maching or planing an angle into the "contact patch" between the hub and strut, but that's all that comes to mind.

So on your car (the NX) how did you correct it?

Keep in mind, Jeff, that most strut cars do not have integral hubs and struts, the above is unusual...so that bolting interface between the knuckle and strut is completely free. - GA

[Greg Amy]

So on your car (the NX) how did you correct it?

Check the link in the above post - that's the stock one, modified - and the link below - which is the struts we fabricated for the 8611 inserts. I can't seem to find a photo of the knuckle - if I find one I'll post it - but the knuckle assembly bolts onto those tabs with the two bolts holes. you can see that those tabs are fully legal to modify in any way you wish.

http://www.kakashiracing.com/temp/DSCN4201.JPG

[JeffYoung]

Ok, I see now. Your knuckle/spindle that the hub mounts to (or is the hub, is that more accurate?) is bolted to those tabs, which I agree you can move around?

I guess the analog on my car is I could fab up an entire strut (like you guys did) and change the angle and location of the spindle.

Very nice work. Very nice.

[TomL]

Okay, I guess we have the legality issue settled, and that it may not apply to FWDs. And I understand how you change your camber curve. My first thought was "that can't be much of a change", but when I calculated it out, I see that it is significant.

But I still don't understand why, for my car at least, you don't think that the spacers would change the roll center. I agree it doesn't change the relationship of the ball joint and tie-rods to the knuckle. But what it does do is it changes the relationship of the knuckle, ball joint, etc. to the ground (i.e., hub height is fixed and the ball joint is now spaced down relative to the hub), thus changing the lower arm angle (and roll center).

And even in the case of your car (or any strut car), I'm fairly sure there is some interrelation between roll center and camber change, so almost any change of one would affect the other at least a little.

As far as getting rid of the strut subtractor, I seriously hope you are joking.

[lateapex911]

I'd be all over redesigned front struts on the RX-7...and I even might go so far as to suggest it not get the strut subtractor... - GA

HAr har har..

Want to trade that for 50 for the boat anchor of a live axle with all that weight banging around and no alignment possibilities?


Oh, it's hard for the ITAC to know which struts can, and which can not be utilized in this fashion, so it's all for one and one for all! Pick your warts carefully,

[Greg Amy]

...(or is the hub, is that more accurate?) is bolted to those tabs, which I agree you can move around?

Well to be technically accurate, the strut bolts to the knuckle, which encompasses the bearing/axle assembly that retains the hub.

....why, for my car at least, you don't think that the spacers would change the roll center.

I don't recall saying that; if I did I was mistaken. However, changing the spacing of the center of the wheel at the end of that lever arm is not going to have a significant affect on the roll center.

As far as getting rid of the strut subtractor, I seriously hope you are joking.

HAr har har..

Not joking, but not a serious suggestion. Having a front suspension such as that virtually negates all the geometry problems of a strut design. When I saw the front end of Tim's (nee, Alan's) Audi coupe I was suitably impressed. If I ever decided to take a shot at ITB it would absolutely be in an Audi coupe (5-cyl torque *and* a good front suspension). In fact, I wish I had the coin to buy Tim's, or at least talk him into a partnership... - GA