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Thread: Lengthened lower arm (how to)

  1. #1
    Senior Member MDMurcy2's Avatar
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    Lengthened lower arm (how to)

    Hey guys, I need a little advice and maybe some more experienced help here.

    I am building a Murcie roadster and using an MR2 as my doner. In the rear I am requiring lengthened lower arms to accomodate the wider track of my build. I need to add 4" to this lower arm. As I am a first time builder and new to all this.....I am not sure exactly what to do here to solve my problem. But this is what I think.......

    Question is: Can this arm be cut and welded longer, it looks cast. Or should I get it fabricated?

    If Fabricating a new arm is the best way to go...... well then I dont know anyone here that I could get to do it for me. If anyone can do this for me, can you please PM me. I would send the original OEM MR2 arm to you, of course.

    As for the upper strut extension adapter, I was looking into what Extreme does for their Murcy builds and that seems easy enough to do. But I dont know enough to fab a lower arm from scratch. I would not feel safe if I did this myself. Maybe seems silly to those with experience but I just dont have it and I definitely dont have the experience to trust my work just yet to that kind of fabrication.

    Here's a pic of the OEM lower arm and where I need it extended the 4 inches.

    Any help and advice would be greatly appreciated.

    Thanks,
    Mitch.



    Keep dreaming if you want to, I'm building mine!

  2. #2
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    Re: Lengthened lower arm needed

    Why extend the rear lower arm, I thought everyone used spacers on the rear to make up the wide track???
    It's the front lower arm you need to worry about, but I am still waiting on someone to speak up on what's involved as tie rod ends and some sort of adaptor would need to be made between the strut and hub housing????? :/

  3. #3
    Senior Member MDMurcy2's Avatar
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    Re: Lengthened lower arm needed

    I have no problem with the front. The rim offset allowed for a 2" spacer to fit up and the turning radius still works with the wheel well. I can live with that.

    The rear is 13" total too narrow (at OEM stock stud plate to the exterior of the body). Unless I change my rims.....Which I could do..... I need at least 6" to 7" wider track per side. I got the rims I have for next to nothing so I would like to keep them. If I can widen the track by 4" or at least 3"....Then I only need 3" spacers to make the rims I have work. Perhaps cost and safety would dictate that different rims would be the way to go...But I am trying to avoid that....thats why I am asking for advice. I really need to keep costs down as my budget is always under pressure.

    I am currently spaced out 6" each side with adapters just for build and measurements. But for putting this on the road and everyday use....That wouldnt be safe.
    Keep dreaming if you want to, I'm building mine!

  4. #4

    Re: Lengthened lower arm needed

    I would make an extention piece from steel that goes down the ball joint hole to lock in place and has a flap on left and right to prevent movement

  5. #5

    Re: Lengthened lower arm needed

    That would be easy to make out of rectangle tubing. I would go 1/4" wall tube and choose the height/width once I measure the stock arm.
    Weld in round tube at the bushing points and make your own bushings out of uhmw plastic. The ball joint receiver must be made by a machine shop to match the ball joint taper.
    I had this done a few times for my front ends, its not too expensive.

    Is the hole on the left for a strut rod?
    If so I would consider moving that as far out as I could too to prevent front/back wheel movement under acceleration and braking.

  6. #6

    Re: Lengthened lower arm needed

    i have been thinking about that as well. but i need to shorten the front ones. welding cast iron is never the best way to go imo. because it is subject to stress. the material properties are difficult to match after welding ( thats a trade ) if i wanted to do that... i'd mount some skids to the bottom of the car and drive over some curbes (scary shizzle)

    the spacers were a good idea and the new build from rectangular piping as well.
    i think I'll go with the pipes... have made them before out of round tubes for a super-7 and works pretty good.

    but be carefull.. do not break them while driving and land in a ditch.

    in the aircraft industry they use breakable paint. it breaks if it is stressed too much. maybe if you use this, you could amp up the stress (during driving) and see catastrophic failure before it breaks.

  7. #7

    Re: Lengthened lower arm needed

    What Jim is saying is to make new arm rather then cutting and extending it. This is common practice/work/modification for a lot of custom cars.

  8. #8
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    Re: Lengthened lower arm needed

    That piece is probably cast steel. It can be welded with the proper procedure and rod. I would extend it between the strut hole and where it mounts to the frame as that is where the least stress is. If you can find an extra set cut one long and one short and weld them together with a stiffener. Take it to an expert though. You could fabricate one but I wouldn't use ERW square tube. I am not familiar with the MR2. Is the hole near the left end for a strut or is there an anti-roll bar attached there to locate the lower arm like a lot of the front wheel drive suspensions have?

  9. #9
    Senior Member MDMurcy2's Avatar
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    Re: Lengthened lower arm needed

    Quote Originally Posted by txbuilder
    That piece is probably cast steel. It can be welded with the proper procedure and rod. I would extend it between the strut hole and where it mounts to the frame as that is where the least stress is. If you can find an extra set cut one long and one short and weld them together with a stiffener. Take it to an expert though. You could fabricate one but I wouldn't use ERW square tube. I am not familiar with the MR2. Is the hole near the left end for a strut or is there an anti-roll bar attached there to locate the lower arm like a lot of the front wheel drive suspensions have?

    This is what the rear looks like.

    Keep dreaming if you want to, I'm building mine!

  10. #10
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    Re: Lengthened lower arm needed

    Does the strut rod that disappears out of the top of the pic have an end that mounts to the frame similar to the end where it attaches to the lower arm? If so then you can extend between the strut mount and the frame on the lower arm. You may need to bend the strut rod slightly so as not to put to much distortion in the mount on the lower arm. You may also have to lengthen the strut rod to maintain the suspension geometry. When you extend the lower arm you will either have to move the top of the spring strut out or slot the holes in the bottom of the spring strut to align the camber on the wheel. Moving the top of the spring strut out will maintain your current roll center height but it will change if you adjust at the bottom of the spring strut.

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