Homemade offset trailing arms
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Race Director
Joined: Nov 2000
Posts: 11,872
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From: Waterloo ontario Canada
Homemade offset trailing arms
I know I posted on this before but I keep getting asked how to do it by new guys.
Once again.
The trailing arms need to be out of the car of coarse. Remove the flange nut and the flange, then the 4 bolts holding the axle assembly on and remove it.
You know roughly the size of the tire you want. From that you know roughly the radius of where the maximum bulge is, the inches out from the center where the maximum cross section is.
Say a tire is 27 inches tall, that makes 13.5 inch radius but the maximum bulge might be 2 inches less or around 11.5 inches out from the center.
Mark this location on the trailing arm. Measure the cross section of the trailing arm in this location. That is the maximum offset you can go. Say it is 1 1/2 inches thick at this point.
The actual sidewall of a 27 inch tire minus the 15 inch rim is 12 inches divided by 2 or 6 inches maximum. Take a strip say 8 inches long by the height of the trailing arm which might be 2 3/4 inches or so.
With a strip of steel 8 inches by 2 3/4 by 1/8th thick bend it in a hoop so when the strip is placed flat on the bench it bulges about 1 1/2 inches up from the table or the thickness of the trialing arm you measure.
You want to weld this to the back side of the trailing arm, don't cut anything in the trailing arm, clean off the paint/rust and weld this curve on the back creating the back side of the trailing arm.
Eventually you are going to cut the front but not now. You are going to remove the front but only up to the back wall. You are not going to cut through the back existing wall of the trailing arm.
Cut out top and bottom pieces contored to match the bulge you put in the back and a matching bulge on the front, this will become your new front wall.
Weld the top and bottom pieces on the trailing arm, Don't weld the outside lip the one facing the outside of the car.
This piece you welded top and bottom will be 1 1/2 inches wide but you need to start with something around 4 inches wide to cut out the profile of the bulge.
Now that the top and bottom are welded to the trailing arm cut out the front following the contour of the top and bottom plates but do NOT cut into the back stock wall of the trialing arm. Leave it intact.
Place another bent piece of steel in the front following the top and bottom plate and weld it in.
You now have 1 1/2 inch offset in the place where section width is needed, your new trailing arm has 3 walls, not 2 like stock so it should be stronger. remember the back wall never got cut, you added a new rear and a new front and left the back wall intact.
It is cheap for a little 1/8th steel plate and should take a easy evening to do one. Two guys can do both in a easy evening.
Good luck
Yours should look like this
Once again.
The trailing arms need to be out of the car of coarse. Remove the flange nut and the flange, then the 4 bolts holding the axle assembly on and remove it.
You know roughly the size of the tire you want. From that you know roughly the radius of where the maximum bulge is, the inches out from the center where the maximum cross section is.
Say a tire is 27 inches tall, that makes 13.5 inch radius but the maximum bulge might be 2 inches less or around 11.5 inches out from the center.
Mark this location on the trailing arm. Measure the cross section of the trailing arm in this location. That is the maximum offset you can go. Say it is 1 1/2 inches thick at this point.
The actual sidewall of a 27 inch tire minus the 15 inch rim is 12 inches divided by 2 or 6 inches maximum. Take a strip say 8 inches long by the height of the trailing arm which might be 2 3/4 inches or so.
With a strip of steel 8 inches by 2 3/4 by 1/8th thick bend it in a hoop so when the strip is placed flat on the bench it bulges about 1 1/2 inches up from the table or the thickness of the trialing arm you measure.
You want to weld this to the back side of the trailing arm, don't cut anything in the trailing arm, clean off the paint/rust and weld this curve on the back creating the back side of the trailing arm.
Eventually you are going to cut the front but not now. You are going to remove the front but only up to the back wall. You are not going to cut through the back existing wall of the trailing arm.
Cut out top and bottom pieces contored to match the bulge you put in the back and a matching bulge on the front, this will become your new front wall.
Weld the top and bottom pieces on the trailing arm, Don't weld the outside lip the one facing the outside of the car.
This piece you welded top and bottom will be 1 1/2 inches wide but you need to start with something around 4 inches wide to cut out the profile of the bulge.
Now that the top and bottom are welded to the trailing arm cut out the front following the contour of the top and bottom plates but do NOT cut into the back stock wall of the trialing arm. Leave it intact.
Place another bent piece of steel in the front following the top and bottom plate and weld it in.
You now have 1 1/2 inch offset in the place where section width is needed, your new trailing arm has 3 walls, not 2 like stock so it should be stronger. remember the back wall never got cut, you added a new rear and a new front and left the back wall intact.
It is cheap for a little 1/8th steel plate and should take a easy evening to do one. Two guys can do both in a easy evening.
Good luck
Yours should look like this
