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Old 10-08-2018, 09:18 AM
Merritt5 Merritt5 is offline
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Default MacPhearson Strut and chassis setup

When I read into chassis setup, conventional vs bb/ss, it mostly refers to SLA type front suspensions. With sla type suspension, you could go in either direction depending on how you want to drive the car and given the front geometry is optimal.

Since the strut system doesn't allow much camber gain, would it favor a big bar/soft spring setup over a conventional stiff spring/soft bar?



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Old 10-09-2018, 08:24 PM
Yukon Cornelius Yukon Cornelius is offline
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Thirdgen Camaro's and Firebirds favour stiff front spring setups with their strut front ends.
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Old 10-11-2018, 04:44 PM
RidiCat69 RidiCat69 is offline
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Interesting thought. I guess you'd have to measure it out and calculate the geometry to see where the roll center ends up when traveling the suspension more.

Having the car travel more on braking is a good thing to get the center of gravity lower so there is definitely a benefit, but if your roll center ends up underground that would be bad. Same story with the SLA cars. Can't just travel the suspension more and pick up the gains. Takeoff points must be changed to gain the desired camber over a longer travel, and to keep the RC from going too low.

With a strut car, I'd think you could start to lose camber if traveled too far, not to mention have RC issues. Not knowing what kind of car you're working with...I had an 04 Mustang, and the LCA's were at such an angle that the control arm would only get shorter under dive, as the ball joint was already higher than the inner takeoff point at ride height. The car was lowered a little already, so I can't remember what angle the LCA's were at stock right height.

Edit: Your sig says a fox, I'm assuming that's the car you're inquiring about?
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Old 10-12-2018, 02:26 PM
Merritt5 Merritt5 is offline
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Quote:
Originally Posted by RidiCat69 View Post
Interesting thought. I guess you'd have to measure it out and calculate the geometry to see where the roll center ends up when traveling the suspension more.

Having the car travel more on braking is a good thing to get the center of gravity lower so there is definitely a benefit, but if your roll center ends up underground that would be bad. Same story with the SLA cars. Can't just travel the suspension more and pick up the gains. Takeoff points must be changed to gain the desired camber over a longer travel, and to keep the RC from going too low.

With a strut car, I'd think you could start to lose camber if traveled too far, not to mention have RC issues. Not knowing what kind of car you're working with...I had an 04 Mustang, and the LCA's were at such an angle that the control arm would only get shorter under dive, as the ball joint was already higher than the inner takeoff point at ride height. The car was lowered a little already, so I can't remember what angle the LCA's were at stock right height.

Edit: Your sig says a fox, I'm assuming that's the car you're inquiring about?

The fox is what I am working with.

I'll have to get under the car and measure it up to see where the roll centers are at and see what I can do to better the geometry.
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Old 10-13-2018, 12:29 PM
mfain mfain is online now
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I ran into this issue (roll center going too low) with my Focus track car. I solved it by making the inner pick-up points of the LCA adjustable - slugs in front and spacers in the rear. I was able to keep the roll center at .75 inch above ground with full compression. Without the modifications it was almost 2 inches below ground level. In addition, I was able to angle the control arm up in the rear which gave me more caster gain with suspension travel.

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Old 10-14-2018, 05:28 PM
ur-n-8 ur-n-8 is offline
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^Nice.
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Old 10-17-2018, 07:18 AM
RidiCat69 RidiCat69 is offline
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+1! I like that mfain!

Short story on this topic...back before I knew anything about this weird roll center thing A friend and I were working on a Fox with an MM subframe, which had two heights of pick-up points for the LCA's. The car was lowered and had a set of drop spindles on it from Racecraft. Not knowing a whole lot about what we were doing at the time, looking at the angle the LCA's were at we, thought there could be camber gain in travel by moving the LCA's to the upper hole so the arms would get longer as the suspension compressed.

We learned a serious lesson that day at the track. Roll center was too high and the car had no front end grip. Now that being said, had we had softer springs to allow the front suspension to travel further it might have worked out. Would want to measure it all out if I did it again, now that I know better.
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