Radius arm too short after rear suspension rebuild?

I have a 1971 Series II that is in the process of being restored. New C17198 Rubber mounts have been installed on the rebuilt rear suspension. I read in previous posts that these are taller than the old compressed original mounts. I also read that the C30286 Cross Member had to be slotted to bring the attachment holes back to 9 inches (upper bolt hole distance). Please see the photo below.

The distance between the blue marked bolts is now 9 inches. I had to slot the Cross Member approx. 1/8" along the red arrows. This had the consequence of forcing the Rear Suspension down (yellow arrow) about 1/4". Please see the photo below.

When I bring the radius arm up, you can see it will not fit over the feature on the body meant to drop inside. Please see the photo below. Note that the distance vertically between the C26701 Hub Carrier to the top bolt holes is approx. 5.25".

Questions for the brain trust;

  1. Is the 5.25" vertical distance correct? Please note that there is no gas in the tank and no spare in the boot. Also, the engine is not installed. Nor the seats in the cockpit.

Please see photo below.

  1. These are replacement shocks from one of the usual suspects. Can the original spring be used or does a “special” set of shorter springs go with them as a pair?

  2. Finally, how have restorers dealt with this issue in the past? I can’t see a way to “stretch” the radius arms forward without tearing apart the rubber mounts. If the Hub Carrier were to move up (lessen the 5.25" distance) by adding weight to the boot, than the radius arm would be more level and mis-alignment less. Help would be greatly appreciated?
    Steven R Card 1954 S674456 & 1971 2R13840.

Steve, if you do a Search on this subject you will get a lot of hits. Here is a thread I started recently on the subject. Regarding the trailing arm appearing to be too short, my take-away was that for an unladen car, like yours (and mine), you should release the shock/springs to allow the trailing arms to be horizontal, which will swing them into a more favorable postion. Even then, some “persuasion” may be required. I used a come-a-long.

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Sometimes its easy, sometimes not. No rhyme or reason.

I would loosen the irs to chassis bolts to the whole IRS can move freely.

Jack the irs on its front edge with a block of wood so it rotates in a useful direction (clockwise).

Sometimes I have had to remove the lower shock bolts to allow the hub to be raised slightly, in effect shortening the distance. Watch your grease nipples!

The final move is to use a tapered pry bar/podger stick through the eye of the bush into the threaded body hole, enabling you to lever the cups into place. The tapered part of the pry bar helps prevent you messing up the captive thread.

Quite often whilst doing this I have another jack with a block of wood following the arm up as you lever, to prevent the cup from springing out.

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Your radius arm will not fit untill you drop the rear down on its wheels and compress the rear suspension. …shorter springs are required for gaz adjustable hight platform shock…cant see from your photos what yours are…Steve

Thanks for the quick response. I will remove all 4 lower shocks and us some “persuaders” to pull the radius arms forward. I’ll let you know how it goes.

You know, if a minuscule dollar value was put on the additional work, caused by the shoddy After Market Mounting Brackets, that needs to be done to get the IRS unit to fit and attach the Radius arms, by the collective number that carries out this work, we could have funded the tooling to make these parts correctly times over. And I suspect that the contribution by each person would be not even be tens of dollars.




Count me in……

You dont need to remove the shocks…fit the wheels…lower the car onto the ground…the rear compresses you can now fit the radius arm…Steve

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Just noticed as well that your top mount bolts on your shocks are fitted the wrong way around…the nuts should be on the outside of the cage…as they are you will struggle to remove the bolts…Steve


Steve, the OP mentions some pretty significant weight items absent from the car, which is why I would not rule out having to remove the shocks. And maybe worth mentioning is that the weight of the car has to be lowered onto the IRS and the hubs need to be supported (which it looks like he has done).

Dont over complicate things…the radius arms dont have to be connected yet…find out if you have the correct springs first…and sort out the top shock bolts…radius arms can be connected at a later date with the car on the ground they slip in easy …Steve

I couldn’t agree more! However, there are no correctly made mounts that I can find.
Steven R Card

Thanks for the tip on the top shock bolts/nuts. I will probably lower the IRS anyway so I’ll turn them around. I’m guessing that when the bolts/nuts are turned around, you can change shocks without lowering the IRS?

Yes…just need a long spanner to get on the nut

Harvey, et. al.,
The “come-along” idea worked like a champ! First and slackened all the screws/nuts holding the IRS mounts. Then I lowered the car down onto jack stands under the middle of the IRS and removed the shaft holding the lower end of the shocks. Using my lift, I raised the hubs until the radius arm was level with the car body. I applied force via the “come-along” (not much really) and the whole thing went right together. Added the safety straps, reattached the shocks and retightened the mount screws. All is well.
Thanks for tips.
Steven R. Card. '54 XK120 S674456 & '71 Series II 2R13840.