MGB Evolution 3 – The Ultimate MGB Front Suspension Upgrade

Few realise that 1939 was not just historic for world events, but it was also the year that the front suspension design that is found on the MGB first appeared on a prototype MG Y series car that was intended to be made available to the public in 1940. Hostilities delayed that arrival for eight years, but when it did arrive it was still leading edge for the time, and was subsequently to be used on the TD, TF, ZA/B, MGA and then fifty years ago in 1962 into MGB, with other BMC saloons taking advantage along the way.

It is testimony to the design that here we are in 2012 some seventy-three years after the suspension design first appeared, we are seeing a further modernisation of that original design because it is still a valid and very functional suspension design. Clearly the passage of seventy-three years does allow some things to become a little dated and therefore open to redesign and use of more modern components, and this is the intention behind the  Evolution 3 suspension.

Evolution 3 was chosen to describe this new suspension based on an understanding that Evolution 1 is the original version of this suspension as found on the MGB from 1962 with the traditional king pin and double arm lever type damper being also the upper suspension arm so combining the suspension location function with the damper function. (Note for many here is that a damper is not a shock absorber; the spring is the shock absorber and the damper does as the title suggests, damp the spring movement, just so we are all clear what I am talking about.)

Evolution 2 is regarded as the RV8 development of that original suspension where the king pin was replaced by a new stub axle and hub assembly held in place by new spherical ball joints, and the original dual function hydraulic lever damper replaced by a new upper double arm with shorter arms than the lower arms, and the damper function being taken over by a vertically mounted telescopic damper sat within the coil spring (often described as a coil over damper).

The benefits of the redesigned suspension were quite clear in the greater control over suspension geometry during suspension movement and more precise damping control.

These advantages were significant enough to see the RV8 suspension be slightly altered to enable it to be offered for any MGB with bolt on or wire wheels, but the down side was the need to also use the new hub design which also demanded the RV8 brakes as well. The result was an enormous cost of nearly £2000 by the time the last items were sold, which understandably put many potential buyers off. The benefits of the redesigned suspension were not lost however, and as most will know there have been effective alternative front suspension conversions available for some years, which sees the original lever arm damper removed and replaced by separate double arms and telescopic damper.

This may generate the question of why there is any need for another MGB front suspension? The answer is quite simple in that nothing is ever perfect and there is always room to make improvements. This is one takes the opportunity to create a developed MGB front suspension with the advantage of the big step forward the RV8 design made by using spherical upper and lower ball joints to replace the king pin. This has not hitherto been used, but unlike the RV8 it retains the MGB stub axle, so enabling all standard MGB parts that fit to this to be used, and also allowing all current uprated products developed for the MGB to still be perfectly applicable too. Ease of adjustment of suspension geometry is also a big advantage, allowing for both camber and castor. The use of these joints provides much smoother and precise movement over a wider range and so improves the operation of the suspension. Additionally, the need for greasing is eliminated so the two grease nipples per king pin are no longer needed and the position where the nipples were fitted is plugged with a threaded plug. (Threaded plugs allow for simple removal and fitting should there be a need to change the stub axle at any time in the future.) This lack of suspension grease nipples is a feature even the last MG TF of 2011 can’t claim!

 

Another bonus for this suspension is the inbuilt ability to easily alter the camber and caster angles, the latter a more common goal in recent years to reduce steering weight as the nominal 7 degrees was specified for the early cross ply tyre days. The RV8 cross member was constructed so that when fitted to the body the caster angle was around half that of the standard MGB, to suit radial tyres, and in recent years this has been a more common goal using various means of altering the angle that the front cross member attaches to the car body. This can be a little fiddly as altering the angle of fit of the cross member to the body also affects the angle of the steering rack mountings and that has to be corrected also.

Fitting the Evolution 3 requires removal of the original ends of the cross member to provide clearance for the new position of the GAZ telescopic damper, consequently a substantial new bump stop is now found within the coil spring acting against a modified spring pan. The coil springs used are original which makes spring choice for the intended application simpler as standard MGB spring specifications are obviously well proven. The damper as mentioned is also the very well proven GAZ damper that is renowned for its precise but also very comfortable ride characteristics, and being mounted outboard of the spring on the axle centre line means it is working in an ideal position.

So much for the description but how it actually works is clearly what everyone will be interested in, and the simple answer is very well, just as it should. The MGB front suspension has always been more advanced than the rear so it is very important to say that the rear suspension must also be in a commensurate as new condition if you are to achieve and enjoy the benefits of the new front suspension and the test car was in such a condition.

I have only driven the car on secondary public roads, meaning many ‘not’ maintained at public expense, so the ruts and general surface irregularities were the good sections and most other sections were severely rutted with breaking up edges creeping out into a third of the road width. Fine when nothing is coming the other way, but forcing you into those rough areas when something was, as it frequently was, makes you think a 4×4 or old Citroen would be more appropriate. Nevertheless, the ability of the new front suspension to cope with these situations and allow good progress to be maintained was surprisingly impressive and not dissimilar to how my MGF copes with the same roads; although the MGBs live rear axle is not so capable and reinforces the point about ensuring this area is not ignored.

The test car was equipped with power steering, which is something that can be invaluable to some at sub 20mph speeds, but for those looking for the best feedback and fine control then the original non assisted MGB steering with the chrome bumper ratio is in my view best, although compensating for this using the adjustment of camber and castor available with the MGB Evolution 3 Front Suspension could give the best of both worlds.

One of the benefits of these modern softer more precise suspension conversions is that you can now consider more modern and lower profile tyres than would have been possible previously. I moved up to 15″ rims and took a risk by covering them with a 185/55 x 15 Toyo Proxes T1 R tyre, a very modern and effective performance tyre usually associated with MGF/TF than MGB, and the experience has been much better than I had hoped for with none of the harshness and patter that I have experienced before when using a 60 profile tyre with original spec MGB suspensions.

Development of the new Evolution 3 specification has involved testing both standard and modified MGBs at the famous Millbrook test facility to validate the actual cars suspension when taken to the limit, something that can’t be done on public roads. The results of these tests will be summarised elsewhere as I was not present for these, along with others road driving impressions of the modified car. Overall though what other car can claim to have such effective developments still occurring after such a long period?

Words by Roger Parker.

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