Anti Roll Bar

[Neil Clark]

Got almost all the rear end dismantled today so ready to look at the front.  Just the diff itself to remove.  The anti roll bar fitted is 24.5mm, so closer to 1 inch than what I think is the standard 7/8 inch which I make 22.5mm.  Is that correct for the standard one?  I won't know if the existing one is damaged until I trial fit it on the new chassis and will save it if I can.

[DanMi]

early spit should be 11/16 later 7/8. However these have been changed over the years. the 7/8 was to counteract the greater roll from the later swing spring, which you may have. I run the later mk4 swing spring with 7/8 on my mk2 and of course someone may have fitted an aftermarket one at some point

 

[DanMi]

to tell which rear spring you have, the original has 6 bolts which hold all leaves down the swing spring has 4 bolts holding a box down so that the upper leaf has a bit of movement

[Neil Clark]

Yes I have the swing spring Dan with 4 bolts and I found that the rear is all in excellent condition.  Do you use the 7/8 anti roll bar out of choice or as part of an upgrade from 11/16?  My car has Konis fitted. 

[NonMember]

The 7/8 ARB is stiffer than the 11/16 and was factory fit on swing spring cars to compensate for the reduced roll resistance of the rear spring. It's highly beneficial (if not as strictly "essential" as people say) with the pivoted rear spring. It's not an upgrade for fixed rear spring cars - it just promotes understeer.

So, in summary, the ARB must match the spring - fixed spring goes with 11/16" ARB, pivoting spring with 7/8" ARB. The other two combinations are not advised.

[Neil Clark]

Thanks Rob - makes sense now.

[DanMi]

and to put it in context fixed spring was mk1-3 and they changed to swing spring on mk4 and 1500 to reduce rear wheel tuck under on hard cornering. Many myself included update both spring and ARB when restoring. The very late mk4 and 1500 also had longer half shafts. on 50+ year old cars what you have will often not be as it left the factory.