Mk2 rear anti roll bar?

Do you guys have any thoughts on my budget rear anti roll bar for my Mk2? it is an 18mm roll bar from the rear of an Opel Manta B with the ends cut off, cost me £25.00 from Ebay inc. postage, plus four 19mm cable clamps, I will shorten it a bit (50mm?) more and will probably machine up four 50mm long alloy blocks with 3/4" one side and 18mm the other half round cut outs to slip between the rollbar and torsion bar where it is clamped, any thoughts? clamp it each end? or move the rear clamp forward a bit? I think it looks made for the job!

Hi M, I don’t know how far it matters but the Harvey instructions said to mount it with the ends towards the rear axle ?
Regards Roger

Incredibly good fit and neat job. It would be good to throw it around a bit to feel the difference in handling.

I’ve been thinking about some of the changes with loads on the two torque rods and would like to offer my thoughts.

When one wheel goes up or down relative to the other, the anti roll bar twists slightly. In twisting, it will want to rotate a little in the clamps. This could eventually cause wear in clamping area and may eventually break a clamp. Fabricating the special clamps will help this. Also there will be a much greater load applied to the torque rod rubber bushes which could shorten their lives.

I’m being a bit of a devil’s advocate to highlight a few places that would need inspecting from time to time. It would be interesting to see if there is any long term usage history on this accessory.

Peter

Not 100% sure your get the best out the roll bar having it that way around :thinking:

When I try to work out the theory of roll bars or steering racks my head gets sore! Do HB recommend that way round because their straight roll bar would hit the diff case or a shaped one would be more expensive to make or because a shaped one would be less effective?

I don’t have the front of my rear springs attached at the moment so will do some tests by jacking up one side or the other and take a look, not today as we are preparing for paint but before I finalise it, It will be hard for me to compare the handling as I sold my last Mk 2, a white 340, 45+ years ago!

I doubt I could break those clamps, they have M10 threads and are stainless, the rod part will be on the solid roll bar and the wider saddle on the tube torque rod, I could place large, 3" dia. nylon washers each side of the torque rods but that may induce a load they won’t like if they cannot twist in normal use,

I am not sure , straight bar would be less expensive to make , but don’t think HBE would make a bar straight just to save a few pounds , as we know they are expensive now new , one shaped to go over the diff would add a few hundred to the cost I would have thought .
On saying that , having the bar run along the Axle it may well be more affective :thinking:

Hold your arms out in front of you , lift one up the other down , see how much more movement there is at your hands , then your shoulders .

So would fitting the bar at the end with more movement be more affective , after all the idea of the bar is to stop so much movement !

For another £25 I may fit both :rofl:

I’m also no expert but have the HBE bar in my car, my thought was that it is intentionally pointed the way it is so that the twisting of the bar ends is what actually pushes against the twisting of the axle vs. the body, whereas having the way you have it may be too stiff, or not twisting the bar the right way to achieve the desired effect, but just a guess! The axle is always straight, it is the body end of the arms that can shift away from parallel, so in a sense having the straight end of the bar closer to the body is the maximum effect?

Here’s my 1 Satoshi :slightly_smiling_face:

  • stabilizer bar applies force between body chassis and rear axle, so moving it’s mounting points to torque arms will increase rubber silentblocks load,

  • if stabilizer bar is closer to rear axle (weight-wise) it will add to undampened mass at the wheels more,

  • stabilizer bar should transfer only rotational torque, so it works best when it’s torque part is aligned with mechanism rotation axis. These are the points where rear axle torque arm’s bolts are put, both ends are adequate.

  • less stress is put ont the mounting bolts of stabilizer bar when torque is applied to as long arm as possible. This promotes bar mounting points (rubber blocks) at the bar rotation axis, which Mk2-1 lack from the factory.

My Opel roll bar is I suspect thinner than the HBE and has quite a few bends in it so inherently more flexible, I will jack up one side and observe what happens, quite easy to do at the moment as I don’t have the front of the rear spring mounted, I have been mounting the BMW steering rack today, pictures will follow,

I have thought of a test you could do Pat
Place a Axle stand on some Bathroom scales , and place under one end of the Axle ,
Then jack up the other end , by a given amount , say 8 inch .
Then bolt the Bar the other way around and do the same .
If there is a diffrence , it will show in lbs :thinking:

Hi All,
I Am still interested in mounting an ARB at the rear of my Mk2 and so really like the alternative Opel one . What a found! In the meantime any practical experience ?
Has someone maybe the dimensions of the HBE one ( diameter, size between the legs?) as may be there is another one that fits .
Thanks in advance.
Roger (‘61 Mk2 3.8 auto with S3 box)

I too would be interested in these measurements.

WRT fitting the bar front or rear, wouldn’t having it further forward decrease the amount it moves for a given amount of suspension cant (is that the word?) and therefore decrease the mechanical advantage?

So with the Opel bar over the diff you actually have to bend your bar much more for the same amount of cant, both making it relatively stiffer but also risking breaking it.

I fitted the HB item earlier this year - clearly noticeable reduction in roll, no reduction in comfort - as Ian has inferred, and in my limited understanding leverage is key hence effectiveness relies on the the clamps being as widely spaced along the torque/control arm as possible.

I recon the HB roll bar is 3/4" 19mm, the Opel item is 18mm, so a bit more bendy but as I am mounting it the other way round it should be comparable, I may shorten the legs a bit and move it a bit more towards the centre of the anti tramp rods, or I could probably reverse it … a good road test will tell me more, and that may not be so far away, I have never seen a broken roll bar, yet!

I had a customers Subaru come into the shop and the lady was saying that she noticed the car was down on the passenger front.
Put it on the hoist and the ARB had actually flipped 180 deg on that side, I loosened off the fitting and it sprang back into the correct orientation. Bolted every thing back up and she drove off. This after pricing up new parts expecting the ARB to be trashed 🥲

Hi, reading this post, I would be very interested to hear more about the BMW rack… particularly bump and ackerman thoughts… sounds interetsing… cheers

I understand it rolls less but with all other parameters untouched, doesn’t that make the chances the car oversteers much higher?

Hi Julien,
Agreed body roll is much reduced - cannot comment on understeer - cannot say I have noticed.
John.

As far as I know, installing a stiffer ARB at the front make a car understeer, whereas a stiffer car at the rear make it oversteer (or at least oversteer more than stock, which could also mean make it understeer less towards a neutral behaviour).