MG Engine Swaps Forum

I'm planning to redo my entire front end (swivel ins, bushings etc). Should I fit uprated front springs? My car has a Camaro 3.4L V6 + T5 and it's a 1969 roadster. I would like to keep my ride height as near to standard as possible. I understand that are some after market springs that are smaller and therefore have more travel without increasing ride height. Anyone using them?

Your V6 should be very close to the same weight as the original engine so unless your springs have sagged or you want to emphasize performance there should be no real reason to change them. However, the GT had a bit stiffer springs and would raise the tide height incrementally.

I'm a proponent of tuning the shocks for handling and basically leaving the springs alone.

Jim

Right. Well, the job of the springs is to support the weight, limit excursions to just shy of the bump stops under the near-worst conditions, and set the ride height. Once those conditions have been met there really isn't much more you can get out of them without compromising the ride, and the more of the available suspension travel you can make use of the more continuous will be the tires' contact with the road. Therefore the better the potential handling will be. The shocks however greatly affect the performance of the suspension, determine stiffness in both jounce and rebound, as well as controlling ride quality.

On the MGB, due to the ratio of usable spring stiffness to sprung weight the natural suspension oscillation frequency is uncomfortably fast, so firm damping is advised. And, the firmer the damping is, the lower the spring rate should be for a given ride quality. Conversely the higher the spring rate, the lower the damping. Compare to a boat like the big old caddys where you can practically count the oscillation period in seconds, with a high spring rate, long travel, high unsprung weight, long wheelbase and low damping, the MGB is quite rapid, which contributes to it's nimble handling. But you are very limited in being able to change this period by the constraints of suspension travel, spring geometry, and body weight. Yes, you could wind a lighter spring and stuff more of it into the hole to give the same ride height, but then you risk coil bind and overtravel, bouncing off the bump stops repeatedly. The spring rate really should be rather aggressively progressive, meaning that as the spring compresses more it increases it's load capacity in more of a exponential fashion rather than in a straight line, but unfortunately MGB springs are straight wound so we do not have that option. And there is a definite limit to how far you can go with the shock valving and oil to keep the excursions in range because of physical damage to the shock links and the shocks themselves. Likewise you could go stiffer with the springs and many do. If racing is your game this is sometimes preferred. But, you quickly reach a point where the shocks either make the ride harsher or become ineffective at controlling oscillations. And for me, the MG is uncomfortable if it begins to oscillate any more than the OEM suspension does, meaning you really can't go any lighter on the shocks, or at least not much. And I prefer not to rattle my eyeteeth out of my head in my daily driver.

In all honesty the OEM suspension is really pretty good, but the best bang for the buck is to fit new (reman) Armstrongs with adjustable damping. Then you can dial in the damping to suit your preference. (Alternatively you can do this with valve and oil viscosity changes but it's much more work.) Once you limit the excursions to match your driving style you can evaluate whether a spring change is advisable, but generally at that point you will be looking at sway bar changes instead.

A great deal of personal preference goes into setting up the suspension, and of course once you get to the swaybars you are also playing with handling neutrality. Stock, the MG doesn't have a great deal of understeer but there is some. The Mk I and II cars benefited from being fitted with the GT swaybar, going from 9/16" to 5/8" and if the suspension was lowered an inch handling became neutral. This was a preferred period upgrade. But it has become more common to leave ride height alone and go heavier on the swaybar. There is a limit here too both in terms of making the connection between the front wheels so stiff that you may as well be running a beam front axle, and destroying the handling balance in pursuit of a flat cornering car. A little body roll is not a bad thing. It provides beneficial camber changes, and just cornering flat does not mean cornering fast. Neutral handling means that at the limit of tire adhesion both ends of the car lose grip at the same time. When you go so fast that the car slides sideways it slides equally well at the front and at the rear, and is therefore controllable in the slide with steering and throttle inputs. Up to that point any references to neutral handling are only references to the feel of the car and have no real bearing on actual grip. Going too stiff on the front swaybar without adding a rear bar can absolutely destroy neutral handling. It's not quite as simple as saying that a bigger bar on the front increases grip at the rear, many other elements play a part.

Jim



Edited 1 time(s). Last edit at 2017-08-17 11:43 AM by Jim Blackwood.