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Author Topic:   rear trailing arm angles
Fomocosho
Dirt Maniac

Total posts: 135
posted May 02, 2005 07:19 PM  
What is the best angle to try to get with the upper and lower traling arms on a metric car? I searched this forum numerous times and I seem to get conflicting answers.
any help would be greatly appreciated.


Thanks

racer17j
Dirt Forum Champ
Total posts: 5390
posted May 02, 2005 07:30 PM  
My lowers are level and my pinion angle is good. Is there a better angle to promote more forward bite? The rearend is a non floter from jr motorsports. I dont have any forward bite no matter how much I try to keep my foot out of the gas.

crc1124
Dirt Maniac

Total posts: 143
posted May 02, 2005 08:39 PM  
According to Steve Smith's Street Stock Chassis Technology the best angle for the upper control arms is " parallel to the ground with no angle". This helps in both acceleration and braking. If they have a downhill angle in the front it will cause rear end hop under braking. If they have an uphill angle in the front it is supposed to cause wheel hop under acceleration. The upper control arms control the front to back and side to side movement of the rearend.
This is all explained in the book I mentioned " Street Stock Chassis Technology by Steve Smith". Most racing catalogs sell this book and it really explains alot. I have found it to be a very valuable tool.

[This message has been edited by crc1124 (edited May 02, 2005).]

jay116
Dirt Freak

Total posts: 428
posted May 02, 2005 10:05 PM  
I run the lowers level. The uppers are mounted 8 inches above the pumpkin, on a downhill angle towards the front of the car. Also, springs are mounted 1/2 on 1/2 off the rear axle tube towards the front.

racer17j
Dirt Forum Champ
Total posts: 5390
posted May 03, 2005 04:16 PM  
I dont have any percentages i never had the car scaled. I have 1000lf 1250rf 225lr 175rr with stock mount bilsteins all the way around. Whats the lowest you guys go on tire pressures? I have a consistent top five car but the other guys blow by me on the outside where I never have any traction.

racer17j
Dirt Forum Champ
Total posts: 5390
posted May 03, 2005 05:43 PM  
The wheel hop on braking thing is a myth. Kinda. On my metric I run about 30 degrees onthe uppers. The lowers are at 5 and 10 with the front higher than the back. With the shock behind the rearend(stock metric) the only wheel hop I get is under emergency stop braking where I need to come to a stop NOW to avoid a wreck. And even then its not that bad. under normal racing there is no wheel hop but the back of the car does drop hard when the throttle is chopped. Now on my old car(76 monte) the shocks were infront of the axle. that one had about 25 in the uppers and 15 in the left lower and 5 on the right. because of the angle of the arms the housing rotates as the suspension cycles straight up and down. you all know that, nothing new. however because the shocks were mounted on the front of the axle under power the rearend rotates back and the lower shock mounts raise up. and under braking the lower mounts drop. The end result is about 1/2-5/8 inch shock travel for each inch of wheel travel. even the real heavy PRO shocks felt soft on the back. That car would get wheel hop during racing conditions because of the shock placement.
Nick

Fomocosho
Dirt Maniac

Total posts: 135
posted May 04, 2005 04:11 PM  
Do you mean 30* with the front higher or lower? I have a 6.50 gear with a saginaw 3 speed 205/75/15. on a 1/3 mile medium banked track. I turn about 6,500 rpm I dont have a recall tach.

racer17j
Dirt Forum Champ
Total posts: 5390
posted May 04, 2005 05:16 PM  
on the uppers you will always be higher on the housing then on the chassis there is no way to get around that like i stated before the lowers are opposite the chassis mount will be level or higher then the housing mount

    

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