Elise Chassis Corrosion and Repair
We look after many hundreds of Elise's and their derivatives, over the past few years we have noticed a powdery deposit associated with aluminium oxide corrosion around the front upper wishbone mounting point which understandably has given us some cause for concern.
Recently we have had an Elise in for some suspension work which has given us the opportunity to remove the front upper wishbone. Having removed the wishbone we found that the area that had been concerning us had corroded to the point that it was perforated around two thirds of the way round the mounting point.
We
have investigated the cause of the aluminium oxide corrosion and
have come to the conclusion that it is as a result of the chemical
reaction between the chassis bobbins (the thick washers that are bonded to
the chassis), mild steel caster adjustment shims and the aluminium
chassis, this problem is exacerbated with natural build up of road
muck around this area.
At this stage It is likely there are only a few
early high mileage cars that have corroded to a point where the
chassis is perforated. On the rest of them the important thing is to
stem the corrosion. With this mind we are currently having the
caster shims produced in an material that will not rust and so
reduce the chemical reaction between the chassis bobbins and the
aluminium
chassis. We will need to remove the top wish bones, clean and treat
the chassis bobbins and the chassis, paint the affected area and
reassembled with our new caster shims, this will stop the corrosion
in its tracks and greatly reduce the chances of it reoccurring.
For cars where the corrosion has perforated the chassis we are working on a repair panel that we will be able to bond and rivet into place to regain the original strength.(Watch this space) Although we would discourage any owner from this form of repair until the manufacturer has had time to evaluate the problem and perhaps come up with an official repair.
The
same chassis bobbins and caster shims are still being used by Lotus
on the current Elise's and the derivatives, so even the current cars
will in time go the same way unless the chassis bobbins are treated
and the shims car changed.
We are offering a free visual inspection for any owners who may think their vehicle may be affected please ring 01932 340003 to arrange an appointment.
Elise Chassis Corrosion, Repair Update Sept 10
Since we found the first badly corroded chassis show in the pictures above, we have had the opportunity to examine the many vehicles we see regularly and have thankfully found that in the vast majority of cases these vehicles are in the early stages of corrosion. This has confirmed our view that the corrosion stems from the mild steel bobbins and caster shims.
The use of any different types of metals in contact with each other will always have the possibility of corrosion issues, so the first problem has been coming up with a material that can be used in place of mild steel. The material we have used is 316 grade stainless steel, the grade used if of the up most importance! 316 stainless steel is the type used extensively in the passenger aircraft industry where aluminium and stainless steel are routinely used together and where safety and longevity are of the up most importance.
We have reproduced both the caster shims and chassis bobbins in this top grade stainless, we have also increased the size of the bobbins firstly to increase the surface area of bonding to the chassis and also with the aid of the special adhesive cover the early stages of corrosion on the alloy chassis.
The
process begins by removing both front dampers and upper damper
mounting brackets, we when remove both upper wish bones then clean
and degrease all the affected area, we then examine the chassis to
evaluate the extent of the corrosion to insure our repair is
appropriate. It is of the up most importance to be sure that the
chassis has not corroded to the point that the strength has been
lost from the alloy chassis mounts, whilst the new bobbins will
increase the strength of the chassis they are not a replacement for
the alloy chassis.
Providing at this point we are happy that alloy
chassis has not corroded to the point that
the strength has been lost we move on to the next stage, we
carefully remove the original bobbins from the chassis and clean
away the original glue, after cleaning and degreasing the area we
the glue and clamp into position the new bobbins and then leave for
the required time for the glue to set.
The
Front Suspension is the reassembled using the new stainless steel
caster shims, we can also fit a stainless steel shim between the
steel upper damper mount and the chassis as we have also found high
levels of corrosion in this area because once again steel has been
used in direct contact with the alloy chassis.
We are still looking at the possibility of
repairing the few more badly corroded
chassis, but as this is a
major mounting point safety is our first concern. We can not
emphasize enough how important it is to stem the corrosion early.
The potential cost of replacing the chassis / tube will in the vast
majority of cases render these vehicle beyond economical repair.
This repair / corrosion prevention is in no way approved or recommended by Lotus Cars and is designed to pre long the life of your Lotus, but we can not prevent natural corrosion happening in the fullness of time.