Technical Article


Fitting Phase 2 front subframe

"My Method" By Keith Hamer


The information contained in this article has been gained from many years of messing about with Rochdale Olympics in particular and race / track cars in general. I have designed and built several front running racing sports cars and been working on Rochdale's for about 35 years.


Having been commissioned by the Rochdale Owners Club to produce a jig to manufacture Olympic phase two sub frame, and subsequently produced 5 frames, I felt it only fair to explain our method of fitting these frames into your much loved car. The method we use is directly transferable to the fitting of a sub frame into a phase one car also.


Firstly let me explain that the major suspension geometry decisions have already been made for you in that the drawings prepared for the manufacture of the sub frame jig contain all the information on camber, caster and KPI (king pin inclination) angles, therefore the sub frames produced will carry these angles. The only input the person fitting the frame has is in the positioning to attain the for / aft angle which will effect the castor angle to some degree. The only other thing that the fitter has control over is the attitude within the wheel arch, i.e. whether the wheels sit in the middle of the arches and whether the wheels are equidistant from the bodywork from side to side.


Having established the above let move onto my method of fitting the sub frame.


Firstly I have made a couple of assumptions,


1, that the old sub frame has been removed and any repair work has been carried out on the shell in the area around the new sub frame mounting point.


2, that all the suspension components being re-fitted have been re-furbished with new bushes and that all joints are good.


Now using good quality axle stands lift the car up and support with the stands so that all 4 corners are clear of the ground by about 12" to help spread the load and assist in the next part of the process I use a couple of long bits of wood between the axle stands and the body front and rear. Using a spirit level on the flattest piece of the floor set the car up so that it is level to the world from front to rear, this may entail cutting thin bits of plywood which can be slid between the timber and the body floor. The next step is to repeat the levelling process so that the shell is level to the world across the car. This bit is a little trickier as there isn't enough open area around the front of the car to fit a decently long spirit level in. I use the top of the wings in this case to give me a guide to level the shell, this is done by marking on the car a straight line across the wings about 6" forward of the windscreen onto which I place a long piece of straight steel box section, then from the support timber measure up to this steel, using thin pieces of aluminium (shim steel or anything else you have to hand) set the steel up so that it is absolutely parallel to the support timber under the front of the car. You now have a level to set up the side to side attitude of the shell, but make sure not to move the steel from your marked position. First bit done the cars shell is now flat to the world and the process of fitting can start.


At this point it is worth considering whether the floor onto which the front horizontal frame support is going to sit is also 'flat to the world' if it is then great we really are making progress, if not then a little bit more juggling will be required when positioning the frame.


Now the nice bit. Slide the new sub frame into the space once occupied by old rusty frame, and using your own judgement centralise it as best you can. Now you will need to build up the whole front suspension both sides including the steering rack but leaving off the anti roll bar, drop links and spring / damper assemblies for now. You will need to make two dummy dampers to hold the wheels in a convenient position; these should be 12.5" long and will be fitted between the bottom wishbone and top damper mount. Once these are fitted the wheels can be bolted to the hubs and final setting up can begin.


Using ideally a trammel, but two people with a tape measure will suffice, check the wheelbase from side to side, that is from the centre of the rear wheel on the offside to the centre of the front wheel on the offside, and the same on the nearside. At this juncture it is worth pointing out that the front wheels have to be set with NO steering lock, i.e. pointing straight ahead. Jot down these measurements as you will need to equalise them in order to fit the frame correctly. Now assuming that the wheels are in the centre of the wheel arches and the wheelbase measurement is equal from side to side we can move on to equalising the wheels across the car. This is a little bit easier in that you can generally do it single handed. Mark a point in the centre of the wheel arch and using a plumb line measure from the wheel to the plumb (vertical) line, do the same on the other side and note the measurements, the discrepancy (if there is any) is how far out the frame is transversely. If you halve this discrepancy that is the amount you will need to move the frame across in the car, don't forget you are moving towards the side with the highest measurement. Once the frame is positioned you will need to remove the road wheels once again to gain access for the next (most messy) stage, be careful when removing the wheels as you have just spent some considerable time lining up the sub frame and you don't want to disturb it.


Now at this point we have to make an assumption, that is that the frame you have just removed was fitted correctly in the first place because you are going to have to use the evidence of the original frame to line up the tubes on the rear of the new frame against the engine bulkhead, unless you have access to Camber / Castor / KPI gauges the position of the original frame is going to govern the Caster of the new frame.


Just a quick hint on castor, firstly definition: Castor is the angle of an imaginary line drawn through the top and bottom pivots (ball joints or trunnions) and is viewed from the side of the car.


Castor can be either negative or positive and it is what gives the car its stability in a straight line. I have measured several Olympics over the years and found the Castor to be about 13 degrees on average, as has been discussed within the club for many years this seems to be quite a lot, but trust me it isn't too excessive, when we designed the DRK we looked into castor and decided that 11 degrees was our goal, we built 59 DRK's and to date no one has complained about the handling of them.


Just out of interest the camber and KPI aspects of the geometry are set within the new sub frame (built from drawings supplied by the Rochdale Owners Club) and the hubs fitted to your car. Some front hubs do have different angles present, it does depend on the original donor vehicle as all triumph hubs are not the same. The rule of thumb would be to use both hubs from the same vehicle. Over the years it is not inconceivable that hubs have been replaced or damaged (bent or distorted as a result of being kerbed) this would explain the possible differences in angles we have come across over the years.


Below is a table of measurements we have done on Phase two Olympics which show (just for interest) the differences which can be present, I hasten to add that all cars handled perfectly well.


Car 1


Castor offside 13.5 nearside 14.5


Camber offside .25 pos nearside 0


KPI offside 7 nearside 14


Car 2


Castor offside 12 nearside 12.75


Camber offside 1.5 nearside .5


KPI offside 27 nearside 17


OK now back to the job in hand. You have your sub frame positioned in the car and it is correctly positioned, you now need to check that it is level across the car with a spirit level on the bottom tube. This tube needs to be level, if it isn't you can shim the tube up off the floor of the car with a suitable medium, I would tend to use glass fibre but body filler will suffice. You will also need to check the position of the rear tubes against the engine bulkhead from the original frame marks and support the back of the frame in position.


You now have the sub frame in position and it is now time to get 'down and dirty' I don't use this phrase lightly, with all our experience of glass fibre gained over many years I can say without question that this job is simply the worst job you could possibly do on a Rochdale. I don't propose to describe the process of bonding the frame in; if you have got to this stage in a Rochdale re-build you will no doubt be pretty good at fibreglass already. All I am going to say is that when we fit these frames I find that it is best to do the bonding in stages, start by bonding the horizontal tube to the floor, this is the easiest of the tubes to get to and it will have the effect of locking the frame into position so that you don’t have to be too precious when you bond in the bulkhead tubes. Having cut out the old frame you know where you need to bond, just take your time and the whole thing should come together pretty quickly.


Using the method detailed above we have just finished fitting one of our sub-frames to Roger Coupe's phase two. Having built up the front suspension with component parts re-furbished by Roger we did our standard geometry check and were delighted with the results we achieved. These results are detailed below but the critical factor for me is that the angles within the system should be as close as possible from side to side, most car manufacturers will give a 1 Degree tolerance from side to side, we achieved :-


Roger Coupe phase 2


Castor offside 8 nearside 8


Camber offside 1 pos nearside 1 pos


KPI offside 27.5 nearside 27.75


This has been achieved by careful manufacture of the sub-frame jig from accurate drawings, close tolerances in the manufacture of the sub-frames themselves, and accurate alignment of the frame within the car. I don't consider that we are any more skilful than the average Olympic owner and although bigger than most peoples garages our facility is still only a wooden shed with a concrete floor, and I can't see why anyone can't reproduce these results on their own car.


Good luck


Copyright © Rochdale Owners Club
Last Update