DiscoQuinn

Can it be done on FB struts? And by how much? I'd like to lower the car properly while retaining the stock geometry (Use an RCA under the strut bottom). Maybe even get rid of that nasty +1 camber. :S

Re-Speed.com

iTrader: (3)

Yep......it can.

Decide on an insert. Choose tube material needed for new insert. Cut off old tube. Weld on new tube.

Some insert choices need larger tube, some will take the stock tube. If just shorten the stock tube consider where you may be adding a new seat for a coil over sleeve. You may be able to have that weld serve two purposes.

-billy

DiscoQuinn

I'm keeping the stock springs. I just wish to move the spindle higher up then stuff an RCA under it to get everything back to normal. So I can chop 2" out of the strut just above the spindle and I won't be ruining the enclosed shock?

Kentetsu

Ummm, this is over my head. I'll leave you two alone....







.

Percentage

iTrader: (7)

Hey, would this be considered strut sectioning? Because I've been curious if anyone here knows anything about strut sectioning on our cars.

DiscoQuinn

I guess you could call it that. Removing a section of strut casing. This relocates the spindle higher, thus lowering the car, however, it's suggested an RCA of equal size is placed under the strut on top of the steering knuckle. Equal to the amount of strut casing 'sectioned'. This allows the original geometry to remain, but the front of the car to physically sit lower, without all the negative effects of a shorter spring.

Just wondering how much I can cut out, and the basic process behind it. Obviously I'll make a line along the strut to make sure after the cut things line up for the new weld. I think bwaits is mentioning welding on a collar over the removed section/new weld to help strengthen the casing further.

Re-Speed.com

iTrader: (3)

The entire inside cavity is taken up by a shock insert. To move the cast knuckle up you will need to use a shorter insert.

If you are stuck on the stock length insert then you will need to remove the material in the bottom of the knuckle so that the insert can pass through it. This will involve adding material back - below the knuckle - to support the insert.

Theoretically you could make a "roll center spacer" that has a bored section in the middle for the insert and then another bored section on the opposite side that is clearance for the ball joint stud and nut. The upper bored section could be used to support the insert.


-billy

DiscoQuinn

Ahh, boo. The shock insert is the whole thing?!?! Bawls to that: Though that's a creative solution by removing some of the casing above the spindle, and adding it below it. I'll look at mine a bit more and see if I can pull that off.

bstrange99

This may be a dumb question, but what's an "RCA"?

Re-Speed.com

iTrader: (3)

Roll Center Blocks are used to lower the outer suspension pick up point. This brings the outer pickup point back in relationship to the inner pickup point after the vehicle was lowered.

-billy

DiscoQuinn

That's a confusing wording!

When you lower your car, the lower control arm angle changes. In stock form, it points downwards. So when the suspension compresses the car's width actually becomes wider. However, once the car is lowered, the lower control arm sits level or pointed upwards. So when the suspension compresses the car gets skinnier, which is unproductive. This causes the car to have a higher roll center, making it handle worse. So to combat that, you put a spacer under the strut and above the steering knuckle. This spacer is the RCA, and it moves the lower control arm back to a downwards angle. This makes the handling characteristics positive again as the suspension compresses the car becomes wider.

Re-Speed.com

iTrader: (3)

Incorrect. The track width has absolutely nothing to do with the roll center.

A roll center is defined by a line drawn through the ball joint and inner control arm pivot point. If these points are changed the roll center is changed. The block does move the lower control arm angle back down. This is to maintain the stock relationship.

Why maintain this relationship? Because the distance from the roll center to the center of gravity has an effect on how much the vehicle leans in the corners. Since the "roll couple" or "leverage arm" is longer - And we all remember we could move a mountain with a long enough lever arm.

This image shows exaclty what happens:



-billy

DiscoQuinn

Your roll center will lower the wider your track width gets.

Diagram B doesn't make sense. For the inner pivot point of the lower control arm to be lower, the frame must be lower. This lowers the entire weight of the car, thus the center of gravity would be lowered, but in the photo it remains the same.

That photo only applies to moving the points of suspension on a frame, and not moving the frame itself.

the track width will increase if the lower control arm is on a downward angle. wheel travels through and arch as it compresses. The wheel will move away from the center of the car. The furthest point is when the ball joint is level with the frame mounting point. Then the wheel will move towards the car again as the suspension continues to compress.

When track width increases the weight is further away from the point it is trying to distribute to as the outer tire is the one receiving the weight and compressing the suspension. If the lower control arm is angled downwards before compressing and compresses only to the maximum width (ball joint level with the frame mounting point), the track width will increase and the roll center will lower. This aids in cornering speed, as it is conductive to countering acting the distribution of weight to the outer wheel during cornering.

<3

DiscoQuinn

DiscoQuinn

another good thing with using RCA's is you can play with regular or offset RCA's to adjust camber and track width even more, (static track width. :P) Offset RCA's can move the spindle further from the center of rotation of the ball joint. this increases track width, and changes camber. However, it changes the point of rotation for the steering, since the pivot for the steering is from the center of the upper strut bearing and the center of the steering knuckle bearing in the lower control arm. Bump steer may increase since the wheel is further away from this pivot pint the road has more leverage against your arms?

Re-Speed.com

iTrader: (3)

The image I posted was just a quickly I found before posting. I wanted to show the readers how the angle of the control arm dictates the roll center. As well as how it it can change the length of the roll couple.

True the CG moves down but the roll center *can* change by a differing amount.

With your response and image, you have accurately described how a standard linkage works. Still does not have as much to do with weight transfer as the roll center, roll couple have.

If you were to model the first gen suspension you would see the track change will be minimal. The arc is what....... 30"? In 3" of bump travel that will change the track width by maybe 1/32"?

-billy

DiscoQuinn

I can agree, the track width change is minimal since the lower control arm is fairly level in stock position. You could improve track width changes by lowering the lower A-arm further than the stock location, though I'm unsure how that would affect steering.

j9fd3s

iTrader: (3)

track width is easy to change, you just run wheel spacers. track width does make a difference.

but the objective of the roll center adjuster, is to keep the roll center in a good place, not to change the track width (although you could)

also i have heard of the RCA's that are offset to add caster

lastly if you have a stock car with +1 degree of camber, and you lower it, doesnt the lower arm get longer? what does that do to camber?

Re-Speed.com

iTrader: (3)

The arc the control arm rotates about is large so the camber change is minimal.

-billy