Front Suspension Bushings
Esprit Series 1 and Series 2
I have been having problems with my front suspension bushings for two years now. The problems began on the track when I was braking hard at the end of a long straight for a hairpin curve (at Shannonville Motorsports Park - in reverse direction to normal for those who know the track). This was one of the world famous Let Luce nights - one of which was incorporated into LOG 20oo.
During braking, I heard a loud bang and figured I had broken a brake calliper or something. It turned out, after I limped home and inspected things, that my left lower link to anti-roll bar bushing had pulled through the seat in the lower link.
I ordered replacement anti-roll bar bushings (there are four, two at the lower link and two at the attachment points to the chassis. With the advice received from various experienced Esprit owners, I was able to find a way of installing the press-fit lower link bushing using a large carriage bolt to fashion a home-made press. I thought all was well and went driving. I got two hours away from home and the thing pulled through again. This time it was the right hand side.
I could not determine why this happened but assumed I did not have them fully pressed in. My next step was to have them pressed in at a local garage using a hydraulic press. This obviously meant fully disassembling the front suspension to get the lower links in my hand to carry to the garage. While I had everything apart, I decided to "renew" the lower link pivot-bushings. That turned out to be a problem. The original lower link design did not have a replaceable bushing. JAE suggested a polyurethane replacement and I ordered them. When they arrived, it turned out they were WAY too small to do the job. After some discussions with Jeff at JAE, he agreed to take them back, but I still had the problem of finding a solution to the pivot-bushing problem. I ended up consulting with Ed Luce and two other gentlemen, one of whom owns a series 1 Esprit, and came up with a design using delrin, a super durable nylon-type material. The design involves two "top hat" pieces machined from delrin and some large flat steel washers along with the metal sleeve recovered from the original bushings. One "top hat" is pressed in from the front and one from the rear, the sleeve is inserted into a hole drilled through the centre of each "top hat" and the washers are placed outside the assembly front and rear to spread the loads when things are torqued down.
I assembled these parts with some bushing grease to ease the pivot action necessary to make the lower link function properly. This part of the design SEEMS to be working well after two seasons and circa 4,000 miles.
I then reassembled everything with my bushings now pressed into the lower link and once again I thought all was well. Wrongo! After a month I began to notice the car pulled to the right. I decided to have the front end aligned assuming I had upset things with my modifications to the pivot-bushing. I was told my caster on the right side was way off. Strange, since the measurements from the previous year had things the other way around. Upon investigation, I again noticed that the right lower link bushing was nearly out of its seat.
I assumed this time that the double insertion of the bushings had damaged them, so I ordered replacements. Don Tingle told me the bushings were no longer available but that a polyurethane version was available (See photo - the red bushing is the polyurethane replacement). This design requires re-use of the original bushing's inner metal sleeve. It seemed logical and worth a try so I ordered a pair but became concerned when I saw them as they seemed very soft and, in my opinion, did not look up to the task the Lotus design set for them. I have since learned that the Opel (from which these parts are taken) has its anti-roll bar mounted behind the axle rather than in front so the stresses on these bushings would be much lower in that application.
As I suspected the bushings did not survive long. In fact, they did not survive the stresses involved in lowering the suspension after installation. When the suspension was lowered, the bushings split. Two large metal washers kept things more or less together, but I did not have enough faith in things to take the car on the Let Luce track event prior to the LOG and was forced to use my "winter beater".
I set myself the task of designing a new bushing. Design goals were a) to have something sturdy enough to hold together longer than a week, and b) to make installation simple enough that removal of the lower link would not be necessary.
After learning about delrin for the pivot-bushing, that material seemed a good candidate. Ed Luce cautioned that it was good in compression but not very tough under torsion. Okay, what else could work? Jeff Fleming advised me that any material change would affect bump steer characteristics so I should stick with the rubber design. So then the question became, is there a way to make a rubber bushing in two or three pieces (for ease of assembly and ease of production) that could do the job? Hmmmm. What I really need is two hockey pucks with a rubber tube joining them together. Hey, wait a minute!!!
How to make lower link anto-roll bar bushings. (Use the design that follows at your own risk)
Go to your local Canadian Tire store and purchase three Canadian Tire brand hockey pucks. (Accept no substitutes - you will know they are right because on the side it says "official" and "made in Slovakia" - I am convinced the Canadian Tire logo is important too). Use a hole saw to cut out three mini-pucks of a size larger than the outer diameter of the original bushing and smaller than the inner diameter of the overall aperture in the lower link. Use The same hole saw with a smaller diameter blade to cut a central hole roughly 1.25 inches diameter in the centre of one of your three mini pucks. Find a piece of heater hose (or similar rubber tube) that is roughly 1.25 inches outside diameter and yet fits tightly over the metal sleeve recovered from the original bushings. (Note, take all measurements from the original bushings before burning the rubber off because the dimensions of the rubber bits must precisely position the wheels in castor.)
I found a hack saw worked for the next part of the job. From the mini puck with the 1.25 inch hole, cut two rubber "washers" of a thickness to give an accurate positioning of the wheels in castor. (i.e. duplicate the vertical spacing - dimension "a" in photo - of the original bushings.) Next, cut the other two mini pucks to be thick enough to "fill" a significant portion of the depression on the rear of the lower link seat. (I found this to be roughly 3/4 of the original puck's thickness.) Then, I used the hole saw again and various blade diameters up to roughly 1.25 inches diameter to hollow out one side of the mini puck to form a cup shape to accept the metal sleeve with its heater hose rubber tube. The depth of this hollowing needs to be sufficient to allow the mini puck to touch (or nearly touch) the lip inside the lower link bushing seat with the bushing components all in place. This is likely not as critical as the thickness of the "rubber washer" on the other side as things will deform under torquing of the bolts on final assembly pulling everything together nicely. As you can see from the photo, I left dimensions "b" and "c" larger than original due to the expected deformation during final assembly. The final step is to drill a hole through the base of the cup large enough for the bolt to pass through into the anti-roll bar.
The two photos that follow show the various pieces of the new bushing - first completely disassembled and second partially assembled. Note the "cup-shaped" mini puck ready to be inverted and placed over the exposed end of the metal sleeve.
I assembled everything with some bushing grease and a large steel washer on the rear of everything to support the bushing from the rear. I found that the design not only made the assembly of the bushing easier, but it greatly eased the assembly of the anti-roll bar to the chassis. I just threaded the lower link bolts slightly into the ends of the anti-roll bar and pushed everything as far forward as things would permit. I found that, compared to the original design, there was very little pressure needed to torque the anti-roll bar up to the chassis mounting bushing. On the other hand, when I torqued the bolts down, things seemed to pull in nicely and (visually at least) things sorted themselves out properly.
To the extent I can tell at this point, the design works well. HOWEVER, I must caution others considering this approach that I have not driven the car more than 100 meters and certainly not tried threshold braking yet. As soon as all the snow is gone and Ed holds another Let Luce night I will update this page to give you my final verdict.