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Twisted anti roll bar


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Hi, the FARB on my 1968 13/60 convertible is twisted by about 25-30 mm. Can anyone inform me of an acceptable amount of twist on these things? If this is too much twist , as it seems that the roll bar.is made of mild steel, is it possible to straighten with some heat without adversely affecting the torsional rigidity ? Failing this it seems that only a 7/8 inch dia one is available at Canley , is this an option as I think mine is 1/2 inch?

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Twister thin ones are quite common and no you dont want any twist at all.

 

the 7/8" bar is fine was used on all later cars I believe

 

there are some thoughts it makes for understeer but having used this bar as an upgrade, find that correct front and rear toe with the (from the manual) 150lb load added to each seat and then setting the toe with the car in in its designed static ride height makes a word of difference . ( does what it says on the tin)

 

Two straight planks and a tap measure is quite accurate enough to measure across the wheels

 

pete

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  • 1 month later...

Would toe in make any difference to the sag I have on the rear off side.  I've changed the spring and trunnions but it still sags.  Not by much but it's anoying. I've never seen a GT6 saging and wonder if it could be a torsional thing.

 

Any thought?

 

Peter

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Which GT6? if non-rotoflex, check both driveshafts are the same length. (late GT6 had a 1" longer shaft, so could cause the issue)

 

Next, it may be a problem at the front of the car Jack the car up centrally front, then rear, see if that helps show which end the problem is.

 

Final suggestion from me. The diff mountings may be bent/out of alignement. A very small amount may cause the issue. Not easy to check either.

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I Agree,

 

whilst rear toe out will tend to lower the ride and excess toe in will raise the ride its unlikely to

cause sag on one side

 

certainly check the front anti roll if you cant jack , try removing one sides drop link. There shoild be no real

load side to side.if it springs out of line its bent .

 

Check with a tape the ride height of the front springs

 

let us all knownwhat you find from the clues suggested

 

lean is often nothing to do with where you see the effect

 

pete

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Sorry I wasn't clear in my post.

 

I've a Spitfire 1500 with a lean on the rear off side.  This is noticable from the rear.  If I reverse the lean changes to a very upright car with postive camber.

 

I've renewed the spring, using a standard one, and the diff (because of a rumbling sound) and trunions.  This made no difference, although it rides better.

 

I'll try out the test discribed and advise.

 

Peter

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Sorry I wasn't clear in my post.

 

I've a Spitfire 1500 with a lean on the rear off side.  This is noticable from the rear.  If I reverse the lean changes to a very upright car with postive camber.

 

I've renewed the spring, using a standard one, and the diff (because of a rumbling sound) and trunions.  This made no difference, although it rides better.

 

I'll try out the test discribed and advise.

 

Peter

 

If the camber  / lean changes when you reverse, that suggests your rear alignment is out.

 

Get a long straight edge, the bottom of the sill is parallel, so you can see if the alignment is out.

 

If one side toes out, it will drag the suspension down on that side when going forward. Reversing jacks teh suspension up.

 

Cheers

 

Colin

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Yes two good straight bars or plank and tape measure

 

You need 150lbs on each seat before you checkmany geometry

 

so load it , with renta crowd or sacks of coal/sand

 

with the help place the planks against the tyre above the ground bulge and tape measure across the car, use a long plank as said to sight the alignment down the sill.

you will get a result in 5 minutes and its free

 

rear toe in static laden is around 0-3mm toe in

 

pete

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