Lower control arm angle???

joe1369

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I am re-building my front end, box LCA and UCA, and Jimco aluminum spindles, My origional front end had the LCA's mounted at a 4-5 degree angle of attack upward, What is propper, current, I know there is no standard. The new box bulkhead has room for me to go up to 10 degrees up angle. Should I go with that, or keep it where it is, What benefit/detriment will increasing the angle of attack have on the car, The car is an Alumicraft/Mirage/Jimco stlye front end. Thanks Joe1369
 

Wild bill

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Not sure on buggies, but Geiser told me to set up my TT with the lower arms parallel to the ground.
 

BajaFand

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If I am imagining what you are saying correctly, your "angle of attack" would be castor, of course there is usually castor built into the control/spindle configuration as well. The more castor you have the easier the car will drive straight down the road and also straighten itself when you let go of the wheel, but also the more you have it gets harder to turn the wheel.
 

motorhead

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I believe Jimcos run 6*.
Partybarge, I know you have ALOT more info regarding rake than that :D.

Joel - I haven't built very many cars yet, so my opinion probably isn't worth much. With that said, I put 8 degrees of rake into my front engine truck along with 2-3 degrees of positive castor gain and am convinced it improved the suspensions ability to absorb sharp, square edged bumps but at the price of excessive brake dive. More anti dive could have been added, but at the cost of additional bump steer, I chose less bump steer :D.
 

scottm

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If I am imagining what you are saying correctly, your "angle of attack" would be castor, of course there is usually castor built into the control/spindle configuration as well. The more castor you have the easier the car will drive straight down the road and also straighten itself when you let go of the wheel, but also the more you have it gets harder to turn the wheel.

I think he means the angle of the lower arm relative to the ground, called rake, rather than castor. Motorhead is right that more rake makes square impacts softer, and im my opinion more rake is easier on parts too. But more rake does result in more brake dive. I built in 3° rake at ride height on my truck. A rear engine buggy can probably use 5° or more.
 

atomicjoe23

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OK. . .I just want to make sure I'm on the same page as you guys.

Which angling of the A-arms are you talking about?

Are you referring to the angle of the A-arm when viewed from the front from the chassis attachement point to the knuckle attachement point, and downward meaning that your lower A-arm slopes from the frame attachement to the knuckle attachment? This angle should only really have an affect on ground clearance, corrrect?

Or, are you referring to the angle of the A-arms when viewed from the side of the vehicle? From the front chassis pivot to the rear chassis pivot? This angle would have an affect on the anti-dive charachteristics of the suspensions. . .castor should be able to set completely independent of this (assuming you are building from scratch) correct?

Thanks for the clarification on which angle you're talking about.
 

scottm

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It is the angle seen from the side, and is measured at stationary ride height. So 3 degrees positive rake means up in the front. Some trucks you will see are actually at a negative ange at ride. Most people agree it should be at a positive angle, as more angle results in better absorbtion of square edge and frontal impacts. The downside is more brake dive with greater rake angle. My truck with 3° has very little dive, but I run a stiff lower spring.
 

atomicjoe23

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OK. . .cool, I thought that was the angle that was being talked about, but I just wanted to double check.

Thanks again!
 
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