Front Anti Roll Bar Diameter

[greyV8pete]

For some time now I have though about changing the front Anti Roll Bar on my Hunter for a smaller diameter one. The car corners as flat as anything on a smooth road, but on an undulating country road the ride is rather uncomfortable. As an example of the stiffness, if I jack up one front wheel more than 2” the other front wheel starts to lift off the ground!
The present ARB diameter is 28mm (Granada / Scorpio spec) which is surprising as the rest of the wheel hubs and suspension tie in with a Sierra XR4i setup. The anti roll bar for that model is 26mm diameter.

I have the Rover V8 3.9i engine from a L/R Disco (serpentine drive belt) and R380 gearbox but I suspect that with the engine being aluminium the weight may not differ much from a Pinto? So my question is what diameter* ARBs do other Hunter / Cabrio owners have? Note* - Please measure on a straight part away from the compliance bushes as Mr Ford seems to have standardised on this area to commonalise the bushes, washers and nuts.

Do all the Sierra Mk2 ARBs have the same cranked downwards shape between the D-rubber mounts that my 28mm one has? This is needed to clear the bottom of the sump on the V8. Photo attached. Peter.

[pdm_engineer]

Re: Front Anti Roll Bar Diameter

Peter
Be advised that not all Sieera ARB's are the same shape, some actually crank upwards and backwards. The ARB I used was the same shape as the one in your picture, which came off an 1990 2.0 DOHC GL car, it's diameter is 24mm. There are some pictures on Mike Gardner's Flicker Photo site, which may be of interest. Personally I think you would be better off trying softer springs.
Peter

[danny_nelson]

Re: Front Anti Roll Bar Diameter

Peter, it was good to meet you and your son on Sunday, and I enjoyed the chat. I think Mark used 28mm ARB on most of the cars that he built. I also know that on some cars Mark cut the centre section away. Have a look at Burton Power for Sierra cosworth up grades. Compression struts and track control arms.
Danny.

[Mike]

Re: Front Anti Roll Bar Diameter

Peter
I bought the last Cabrio sold by Marlin. I sent my ARB to Marlin for modification to fit with a BMW M50 engine, and received two struts back, with the centre section removed! When I complained to Marlin, Mark's attitude was that the Cabrio does not need an ARB. I was still not happy about the way they had made the struts (welded large penny washers either side of the rubber bush) to hold it in place, as I believe there would have been a significant amount of play. I was also aware the demonstrator with the M50 engine was fitted with an ARB which did work, and found thit to have a different shaped crank clearing the sump much better.
Simon Gregory has fitted aBMW M20 and has fitted rose jointed struts in place of the ARB, and says his car handles very well, as it is so low. So it looks as though you may not need an ARB.
There are I believe 3 different diameter of ARB, and at least two types of crank shape - the standard one does not work for my M50 engine, but I found that the ARB from a Sierra P100 truck which has the crank shaped back and down was ideal. As the suspension is compressed under load, the crank moves down away from the sump.
I have some photos on my flickr site:

http://www.flickr.com/photos/mikes_bmw_marlin_cabrio/4594901407/in/set-72157603853056410/

You can see the diameters are also different. The top ARB is the 28mm, where as the P100 below is only 24mm

Regards
Mike

[greyV8pete]

Re: Front Anti Roll Bar Diameter

Many thanks to you all for your replies.

I am happy with the spring rates and damper settings as these give a comfortable ride. The reason I have targeted the ARB is that the discomfort is not due to a bumpy road as such but rather due to a road where the surface changes height smoothly but unequally across the width of the vehicle so the ARB is forcing the body to “tilt” side to side (and me with it!) as the front wheels follow the contours of the two road surfaces.

The Burton links are interesting but I suspect may be too rigid (noisy) for road use?

In my “may come in handy one day box” I have just found the old D-rubbers that I replaced on my 2.0GL Sierra about 20 years ago! These are 24mm diameter so bearing in mind all your various comments I think this is the Sierra model ARB that I need to try. If anyone has one of these ARBs that they don't need, plus the two U-clamps that secure it to the body please let me know :-). Peter.

[CosworthCabrioLee]

Re: Front Anti Roll Bar Diameter

Hi Peter give me a call I have one I think.

[Mike]

Re: Front Anti Roll Bar Diameter

Peter

The two U clamps will be the sameirrespective of ARB diameter - it is only the rubbers which differ internally.

[greyV8pete]

Re: Front Anti Roll Bar Diameter

Hi Mike. That may be true for the smaller diameter ARBs but the 28mm ARB rubbers are much larger externally and the U-clamps are a different part number. I found this out when I renewed my existing clamps and Ford ordered the "wrong" ones! I am hoping that the bolt centres are the same though otherwise I will have a bit of fettling to do. :-) For general information though if anyone wants to do a conversion the "other way around" Supaflex do a D-bush that fits the smaller clamps but accepts the 28mm ARB.
Peter.

[greyV8pete]

I finally got around to fitting the 24mm front anti roll bar to my Hunter. I obtained it from John at Kit Fit some time ago. Result is good with a much more comfortable ride over undulating road surfaces and far more like having independant front suspension. The 28mm bar previously fitted was so stiff it was like driving a classic with a solid front axle and cart springs! Another job ticked off the list. Now eagerly awaiting the dual diaphragm servo which is now top of my Marlin to do list :-) Peter.

[CosworthCabrioLee]

What next on your jobs list Peter ?