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PRI - IRS fro small chassis triumphs?


haggis
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http://www.triumphexp.com/phorum/read.php?8,1225394,page=3

 

Wade through that if you wish, but your instincts are correct!

You are getting rid of the spring, replacing it with a solid arm and bushes, and then adding a separate coil spring. Kerching, pockets empty, no change to suspension.

 

Best changes are the simple factory ones (unless a complete redesign)

For a spitfire/gt6, swingspring plus bigger front ARB

Herald/vitesse courier rear spring plus 1" lowering block (and ditch the front ARB, just like the factory did) OR swingspring if you can get one that isn't too low.

More complex, rotoflex conversion, best with CV joints these days.

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I am not qualified to pronounce on the engineering, but Frankly the fact that the spiel reads like something that has been mangled by Google translator would make me suspicious, as does the obvious thought that if this is such a simple fix for the well-documented problems of small cassis Triumph IRS, how come no-one else has thought of it before?

 

Regards

 

Steve C

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I am not qualified to pronounce on the engineering, but Frankly the fact that the spiel reads like something that has been mangled by Google translator would make me suspicious, as does the obvious thought that if this is such a simple fix for the well-documented problems of small cassis Triumph IRS, how come no-one else has thought of it before?

 

Regards

 

Steve C

Ah, but is it a fix? All they've done as has been said is to substitute the transverse spring for a coil spring. The drive shaft still has only one universal joint and the wheel still subject to camber change. The advantage of the transverse spring is that it applies loading centrally  on the upright whereas the coil spring will give an uneven loading. So to my mind this is a retrograde step for a lot of money.

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Hence the "if" in my post above, and I am as sceptical as you are, particularly about feeding all the suspension loads into an offset coil-over, located on what was intended to be a shock absorber mount! Given the big racing scene in the US, and people like Kas Kasner's (proven) expertise with these cars, if there was an easy fix for the "widowmaker" rear end, someone would have found it long ago and proved it on the racetrack.

 

As a long-time fan of American cars and the hot-rodding scene over there, I know that there are some excellent engineers scratch-building some amazing cars, but equally, there are also some backwoods bodgers doing horrible things like sticking Chevy smallblocks into E-types. This was the nation that thought drum brakes were a good idea on muscle cars with 427 big block (or larger) motors.

 

Regards

 

Steve

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The other aspect of the conversion that would concern me would be the inevitable twist of the upright under braking and acceleration. The spring is absolutely solid in the lateral direction and would prevent any deflection but the top link of the PRI system is pivoted. This cannot be as rigid as the transverse spring so in my view an upper tie rod in addition to the lower one would be essential.

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