Adjustable Anti-Rollbars ?

[R59]

What's the basic theory in making an dash adjustable anti-rollbar (cable operated).

Does anyone offer kits? or is it a case of getting the stuff made specifically for the car?

My car had them originally, but for some reason they were taken off (probably rule changes).

Rob.

[Chris_SLH]

Hi,

Most adjustable anti roll bar systems use the 'blade type' system. The blade offers different second moment of inertia (and therefore stiffness) as it rotated at an angle relative to its fixings. The blade needs to be moved by 90 degrees from maximum to minimum position. This can be operated by a cable system or perhaps an electronic system utilising stepper motors???

Try someone like Demon tweeks for a kit or it might be possible to adapt an adjustable brake balance system into this role? Not sure on this one but a thought.

Cheers

[tzei]

BMW M3 race cars had levers inside and blades (front and rear) were operated via rods and links. Sorry, can't get you a picture.

[shiny side up!]

Yes, blade anti-roll bars are usually operated from the cockpit via a "push/pull" type cable.

[R59]

OK. Blade it is then. Now I need sources for the equipment. No, not Demon Tweeks.

Rob.

[Chris_SLH]

Hi

Looking through books and there is a good set of pictures in Carroll Smiths book 'Engineer to Win'. Shows both cable and mechanical rod based systems.

[j'bar]

Hello

I'm not sure an adjustment on the move is such a good idea, especially if it's the front bar : it might make the car very oversteery if the front bar is softened too much relative to the rear, especially on a FWD car.

It might be a good idea to have only the rear bar adjustable to start with, then find out the effects from here.

[Mike Holmes]

Make sure your class rules allow them as lots these days specifically ban them!

Mike

[R59]

Just checked the rules again - Suspension - Unrestricted. The only stipulation is that the original mounting points (if not used) must remain.

The car is rear wheel drive, and the idea of adjustment on the move isn't what I'm looking for. It's to save having to jack up the car, crawl underneath, attack it with spanners, etc....

I'll look out the Carroll Smith book and see what I can make of it. If I look through the bits and pieces that I have with the car, other than the adjusting handles, I'm sure I'll find some more of the parts.

Rob.

[hotgemini]

Originally Posted by j'bar

I'm not sure an adjustment on the move is such a good idea.

It seems most higher level touring car builders around the world disagree with you, but who is to say who is right and who is wrong.

[j'bar]

Originally Posted by hotgemini

It seems most higher level touring car builders around the world disagree with you, but who is to say who is right and who is wrong.

I was only speaking from a safety point of view, ie having the ability to change considerably the balance of your car could be dangerous. But I agree it can help you lap faster if your front tyres don't wear the same way as your rear do.

[dtype38]

Originally Posted by j'bar

I was only speaking from a safety point of view, ie having the ability to change considerably the balance of your car could be dangerous.

Had the same issue myself with my brake bias adjustment when I took my car for its SVA test. The MOT people insisted that I take the knob off and dowel pin the adjuster to prevent movement before they'd pronounce my brakes as safe

As for anti-roll bars... I set my spring dampers up properly and threw the anti-roll bars away! Handles just fine, and weights less

[R59]

The beauty with adjustable bars is that if it rains, you can soften the car with the tug of the handle, as you throw on your wets, or alternatively, stiffen up a wet shod car when it dries out and on go the slicks.

Having them cockpit adjustable saves jacking the car up to loosen the nut, and turn the bar. It also saves the need to make the pitstop to carry out the above also.
And it's just plain lazy! Now that I like!

Rob.

[TomS]

Dad's Lola runs adjustable front and rear anti-rollbar. I would post pics but am pretty useless with computers so it would have to be an email.

They are great other than the blades can crack and they have to be replaced which is quite expensive

[dtype38]

Given that I don't actually run anti-roll bars, any thoughts on how I might adjust my springing for wet/dry conditions? I have coil over AVO's all round :-)

[StephenRae]

Originally Posted by dtype38

Given that I don't actually run anti-roll bars, any thoughts on how I might adjust my springing for wet/dry conditions? I have coil over AVO's all round :-)

I'm not skilled at agricultural engineering but couldn't you fit softer springs, then beef them up for the dry with those rubber 'helpers' made for towing trailers.. I think there is a blow up version available......or am I not helping here?

[dtype38]

It's not quite as "agricultural" a question as it might appear. If I simply fit softer spings because it's raining, then a dry line appears, the car will roll all over the place, but more importantly the tyres would certainly rub the wheel arches. If I fit longer soft springs to give more arch clearance just in case, then the ride height will be wrong and throw all my geometry out. Adjustable anti-roll bars allow for this, but without them I would need some sort of in-car adjustable coil spring stiffness.

[marcush.]

a cool move would be a second spring encapsuled in something like a slidercage with adjustable travel.
I did somthing like that ,it works very well and you can change from soft to firm in amatter of minutes.the key is taking the second spring out of the equation drastically stiffens the spring (the secondary spring can be stiffer than the main!),making the system cockpit adjusable...well...lets see ...

[StephenRae]

dtype... that's why I suggested some method of softening the car up without having to change springs...I would think roll bars would be a must though, if only to adjust the balance of the car.

[dtype38]

My car is quite nicely balanced as it is thank you but I take your point that with no roll bars I don't actually have anything to adjust! My car is actually quite pitch sensitive when braking, so I'd increased my front spring stiffness to reduce dive. I re-balanced by adding stiffer rear springs and found that I had so little roll that I didn't actually need roll bars. It was only when I got to my first wet race that I realised it was far too stiff. Will think on this further........

[EVO1X]

Toyota celica GPA works rallys cars had ajustsble front anti roll ball from inside the cockpit they used a racket lever like a handbrake so you could have about 5 settings between hard and soft

[phoenix]

Originally Posted by dtype38

As for anti-roll bars... I set my spring dampers up properly and threw the anti-roll bars away! Handles just fine, and weights less

It is unlikely, though not impossible, that you have the optimum front/rear weight transfer balance without using an anti roll bar at one end of the car at least.

[phoenix]

Originally Posted by j'bar

I'm not sure an adjustment on the move is such a good idea, especially if it's the front bar : it might make the car very oversteery if the front bar is softened too much relative to the rear, especially on a FWD car

Best way to reduce the risk is to limit the range of adjustment. A limit that restricts the weight transfer to, say, 10% of the weight transfered in roll would make a noticeable difference to the handling but without being dangerous.

Best place for the adjustment is at the front as it will in most cases be the stiffer bar, and in the wet it may be the only bar connected.

[phoenix]

Further to my post #22, if you are always on the top step of the podium, don't add anti roll bars!

[ss_collins]

racecar will be running a piece on tuning arbs in the near future