ARB/Swaybars

[Jeroen]

The side you stiffen up becomes more sensitive to act up. If you make the front stiffer, you will get more understeer. If you make the rear stiffer, you will get more oversteer. For track use you always adjust the swaybars to cope with the conditions. On a road car I always try to find a setting that works well overall. Some understeer isn't too bad, our cars are not much understeered anyway. But the rear, you don't want that to be too stiff.

I have the Alpina swaybar on the rear which has 4 holes/positions. If we call them from soft to stiff hole 1-2-3-4 I found hole 2 to work very well in dry and wet conditions and quite come improvement compared to the stock sway bar. Rear stays quite level but it doesn't make her too tail happy as far as you can't call an E21 tail happy lol. Don't have an uprated sway bar for the front yet.

[PeteK]

I'm sure you already know this, but it's much more complicated then that.

Big front bars transfer grip from the front to the rear. Big rear bar transfers grip to the front. The key is finding the balance.

BTW, torsional spring stiffness goes up in proprtion to the 4 power of the diameter. That means a 6.25% increase in diamter gives a 28% increase in stiffness.

[AndyBaur]

Big front bars transfer grip from the front to the rear. Big rear bar transfers grip to the front. The key is finding the balance.

BTW, torsional spring stiffness goes up in proprtion to the 4 power of the diameter. That means a 6.25% increase in diamter gives a 28% increase in stiffness.

So, BMW didn't think it was worth uprating the front bar, just the rear one. Since they will have spent many thousands of man-hours researching the issue, I have to assume the settings they arrived at were pretty close to optimum. Venturing too far from those settings will compromise other areas.

[e21-Mark]

Modern tyres, different size aftermarket rims, lowered & uprated springs, and 20 something years wear and tear etc, will all have an effect on handling.

I don't think BMW ever optimised handling. It's more likely a compromise between comfort and handling. Added to that, I'm sure we all have our own preferences when it comes to how our cars handle? I found the Whiteline ARB's made things feel much more taught without going over the top. In the rain though, I'd prefer stock ARB's. Personally, I think half the fun in modifying our cars in in working out what works and what doesn't.

[AndyBaur]

I don't think BMW ever optimised handling. It's more likely a compromise between comfort and handling.

In any given situation there is a always a compromise - e.g. a stiff suspension works well on a track but not on the road & the opposite is true.

BMW optimised the E21's suspension (given the mechanical limitations of the day) for enthusiastic drivers to drive in a reasonably enthusiastic manner on the road whilst still being comfortable enough for every day use. They offered harder "Sport" subframe bushes, a larger rear ARB & the usual Sport springs 'n' shocks for drivers that wanted a bit more feel &/or control.

A setup that is too soft for one driver could well be too hard for another.

However, your comments on the value of larger ARB's for road use were helpful. Once I've got the suspension up to scratch (shocks only or shocks & springs [Spax?]) I'll be able to make more of a judgement call as to whether the suspension meets my needs or whether I want to go further.

Given the incredibly low geared steering I think I'd like to put the money into a faster rack first. The reversed LHD E46 swap interests me.