Link pin shims with angled bushings

[hardingfv32-1]

OK, let us see if we can learn something from this discussion.

Steve thinks there could potentially be better handling if the front control arms flex less than is presently the case. May I assume our goal would be to reduce the amount of positive camber that a FV sees under full corner load and thus generate more front end corning performance?

1) We can reduce positive full load camber by starting with more static negative camber. This might not be possible with standard offset bushings, but there is no reason why someone could not have done this on their own. You can easily machine bushings for a no binding 2-3 deg of negative camber. Offset king pin bushings are also possible. Why hasn't the class gravitated to this approach? Could it be that it does not help overall car balance or corning capabilities?

2) There is an middle size tire that can be used to increase front end grip. If our chassis need more front grip , why is this not the std setup. Why is the new Goodyear fronts so narrow if we need front grip? What are the chances that the new Hoosiers will be a wide front?

For this discussion assume that the average FV is pretty neutral. One weekend a little loose and the next weekend maybe a little push. And that we are talking about a big change in the level of front grip. How would this benefit us?

Brian

[tiagosantos]

Not saying that's the case, but wouldn't current rear suspension and tire setups also be limited by and based on available front grip? If a new part or set of parts became available that increased front grip levels in such a miraculous way, I would think a lot of effort would be placed by the class geniuses to improve rear suspension setups and tires..

Again, not saying we need these new parts or that they're a good or bad idea. Just wondering.

[hardingfv32-1]

1) In the short term, we are stuck with the tires that we are provided with. As both brands will have a new design/compound soon, then you can assume it will be 3-5 years before the tires change again.

2) I am going to state that the rear cornering performance is at its maximum at this point for the tires we are provided. We can easily achieve any rear camber we wish at the rear, so there is no reason the the optimum camber has not been/or can be achieved. Very difficult to get a significant reduction in the CG at the rear, so what if left to improve at the rear?

Brian

[tiagosantos]

good point

Still, if anything, a solution for the bendy bendy turkey legs might make our setups easier and more predictable.. What if instead of starting at -1.8 degrees and ending up at god knows what under load, we start up at god knows what and stay there? Wouldn't that be a good thing?

(waiting for another good point to smack me in the head )

[Bill_Bonow]

Another way to get front camber.... Sometimes it is very difficult to fixture a beam tube true/straight when welding in a spring adjuster and in the process, the tube gets welded back together a little crooked

Here is an extreme example:
[ external image ]

[cendiv37]

Instructive Video of FV front end at work:

http://www.youtube.com/watch?v=dombJDMiOc0

I try to keep my link pins as tight as possible with no binding. Like Brian M. I don't believe the shims are for adjusting camber. They are for adjusting end play to align the top and bottom carrier to spindle connections so they don't bind when the link pins are tightened up to near zero clearance.

BTW, the most common offset bushings give you 1 to 1.5 degrees of negative camber. I have seen cars with over 2 degrees negative camber built into the bushings.

[Ed Womer]

It is my top left link pin also that keeps coming lose. I have been doing this for a long time and have my front end working very loose. I slightly back off each link pin so there is no binding and have done it this way for ever but never had a link pin move once the pinch bolt is tighned. The pin does go into the arm easily so I am thinking of trying to close it up some since I usually tap in a chisel to open the hole up so the pins slide in easily.

As for the Goodyears having to much grip I don't think that is my problem since my car is lose so I am not leaning on the fronts real hard just to turn.

Ed

[FV80]

That is a GREAT video of the Vee front end working. It really shows how much positive you get in the turns under load - even in relatively slow turns. Also looks like his CHASSIS came VERY close to the ground going through the cork screw...
Steve, FV80

[problemchild]

I could not see the torsion arms bending in that video. Where do they bend and in what direction?

[FVartist]

The video is a little deceptive. Toad is running on American Racer's and the side walls flex more than either the Hoosiers or G/Y's. Watch the rim and you will see it does go positive but not as much as it seems. This is one of the reasons that the A/R's do not corner as well as the other two.

Bruce

[hardingfv32-1]

So all the "shims are not for adjusting camber fans", you are telling me you live with the camber that develops from the parts you "properly"put together?
No selection of pre-bent parts to try?
No bushings with a different angles?

Brian

[problemchild]

I am not challenging anyone's theory .... merely trying to understand. Most race cars have camber curves built into their suspension design which stabilizes camber with chassis roll. FVs do not. I presume that most of the positive camber that occurs on the outer wheel when cornering is primarily due to chassis roll. How much more is from arms bending and where do they bend?

[hardingfv32-1]

1) The frame is close to the ground in the video because the car is soft in roll. This will get you half way to the positive camber situation, while bending control arms does the rest for you. You can verify how much roll there is using a DA system. It will NOT get you to positive camber with say a 3/4" sway and one full spring pack.

2) If you load the control arms in a press with a test fixture you will find that they bend in a decreasing manner as you travel out the arm. The lose of negative camber is from the lower arm moving in... AND ...the upper arm moving out.

BUT, what does it matter if we have a car that is very close to balanced in most cases? This assumes proper car maintenance and suspension settings as found on most front running National cars as an example.

Brian

[hardingfv32-1]

Ed

"As for the Goodyears having to much grip I don't think that is my problem since my car is lose so I am not leaning on the fronts real hard just to turn."

If you are loose the front has too much grip or the rear to little. For this discussion, I will assume you WANT to move to a more neutral situation. After all your years of racing FV do you think you can find more rear grip? I am going to assume that you can not. That leaves us to work with the front. Would we not need to decrease grip at the front? It could be stated that your front tires are providing too much grip, but you really do not have many options there other than grooving the tread.

Brian

[problemchild]

Ed,
My tongue-in-cheek comment was ment to be humorous while complimenting Goodyear for their much-improved product.
It probably was no more ridiculous than many of the theories presented on these online sites.
Cheers!

[hardingfv32-1]

If you find the theories ridiculous, challenge then with some logical counter theories or test proven facts. How do we learn anything without accurate information.

In my case, most of my ideas are tested on car at the track when appropriate. Some things are better test in a more controlled manner in the shop.

Brian

[problemchild]

Relax Brian (Harding). We all see absurd theories presented evert day. I was not referring to anyone or any theory in particular.

Just as I have no interest in sitting down to dinner with murderers, terrorists, or rapists, I choose to refrain from direct discussions with you or about your theories. I am sure some feel that way about me too. That is all our choice.

I was just trying to learn more about this bending suspension theory. Please continue on with your discussion. Cheers!

[SR Racing]

I too would like to see how much the turkey legs play a role in loss of neg camber. Obviously they must flex "some", but is that what we are seeing in the photos? How was this measured?

Jim

[brian]

My primary interest in reducing front end flex is to improve handling by reducing one of the many variables we deal with. As surfaces change, track to track or as rain or oil is introduced to the surface itself, the front end will change differently. No flex, no changes. As it has been explained to me, the cyclical loading on the spindle and bearings will be greatly reduced if the turkey leg is not flexing. This may reduce spindle failures as well.

As far as the rule and cost hysteria is concerned, several years ago, I asked the CRB to allow use the weld on reinforcements, available as a $9 kit in Hot VW, and was denied. Now after some dreaming while towing around the country, I have come up with a bolt on approach that would not need a rule change. Yea, it will cost a bit more than gussets but it seems that i don't have a choice. Help me legalize the gussets and we won't have to travel this path. I'm not doing it for the money.

Don't bother looking at my car while at the Runoffs. Testing is not complete and I NEVER go to the Runoffs with new stuff.

[hardingfv32-1]

Maybe you should make an exception for cardiovascular stints.

Brian

[hardingfv32-1]

The easiest way to measure the bending on the car is with horizontal potentiometer connected to the end of the control arm and the frame. Your shock potentiometer provides the vertical scale. Your compare the static or calibration plots with the on track data to get a reading on the amount of bending.

Brian

[brian]

Greg, if you watch the video again you'll see that the positive camber goes up while the wheel is on the outside. When it's the inside tire nothing appears to happen. The lower outside turkey leg is pushed inward toward the center line of the car. If it was only chassis roll changing camber, you would see the inside wheel lean more negative. In addition to the tire forces, the chassis roll moves more weight out on that turkey leg as well. The off road gussets were developed because turkey legs were getting bent quite often. Once they had been reinforced the bending stopped. While I've never measured the actual bending knowing the tire is flexing can be confirmed with a pyrometer. Often a squished biased ply tire will generate high inside temps leading the reader to think there's too much negative but in fact the tire is being shoved inward causing the inside edge to rise. That's why fronts often cup on the inside. The Goodyear guys should me how higher tire pressures could solve this problem and reduce the inside temps without touching the camber.

I really enjoy these conversations and don't really mind having to rethink things once in while. The more theories the better.

[jpetillo]

The video was interesting. I think it appeared to bend much more than it really was. The distorted tire hid part of the rim and added to perhaps an illusion that it bent more. Brian M, I agree with your argument of the roll not contributing much. But, the inside had much less load and the tire did not distort much. The camera angle also seemed to contribute.

That's all an unsubstantiated hunch on my part. The camber change due to bending should be pretty easy to determine. Brian H., on the bench do you have the ability to measure bending offset vs. force? If so, it would be straightforward to figure out what the load is during cornering and calculate the expected camber change.

John

[hardingfv32-1]

Unless you are using a Valentino Rossi gimbaled (Gyro) butt cam how are your going to tell if the car is rolling? I know the car in the video and it does not have anything stiffer than a 3/4" bar and one full spring pack. It is rolling like a pig (for a race car) like all Vees.

Brian

[Ed Womer]

Greg, I know, I just wanted to mention that I like my car loose since I am one of those that dislikes understeer.

Brian, could I get more rear grip? I guess but like I just mentioned I prefer a loose car since it is faster to drive but you have to keep on top of it and don't get behind in the steering! Goodyear had an engineer at the Glen double and ask my wife if I would come to him so he could get some tire temps from a vee and when I did they couldn't have been any better, so even if my car is loose I am getting the most out of the tires.

Ed