RICHARD MANN'S UPPER LINK AND REAR SUSPENSION MODS TO 7004100119Q

[Lotus 47]

I've started this topic to record lots of details on my upper link rear suspension fitted to my 1970 Type 54 S2 - 7004100119Q

There is some existing information at

http://lotus-europa.com/0119q/index.html

A number of modifications accompany this upper link, so there is a lot to absorb.

Why did I do this? I was sick and tired of changing universal joints, and frustrated by the LH drive flange constantly coming loose. A fellow Europa owner lost his LH rear wheel on the track, probably as a result of constantly applying high torques to his LH stub axle nut, to the point where the end of the stub axle and nut disappeared into the weeds, while his whee,l brake drum and drive flange shot off and hopefully didn't hit anything.

My initial aims
- replace the U/J's with CV joints
- add an upper link because the CV joint is designed to change length, and cannot replace the fixed length drive shaft
- find an alternative to the Hillman Imp stub axle

My assumption for the upper link was that it should have a length that is a close as possible to the fixed length drive shaft it was replacing, and that the installed angle of the link should match the installed angle of the fixed length drive shaft.

As a starting point, let's look at the inner upper link mount. The casing of the Renault box is massively strong where it mates to the bell housing, so I built some brackets to pick up existing bolt holes.

I used a piece of 3mm mild steel for the rear flat bracket, and a piece of 3mm thick steel angle for the front bracket. The front bracket dictated where I could mount easily onto the bell housing.

Look at the photos and it is all pretty much self explanatory.

Please note the photos show a Type 395 box which is a 5 speed. The Type 336 4 speed will be very similar.

This design assumed CV joints, and used a complete CV drive shaft from circa 1980 Alfa Romeo Alfetta. These cars used a rear mounted transaxle and de Dion. I happen to own an Alfetta when I did this modification.

The drive shafts are unmodified . I did not want cut/shut shafts in this design, or get new shafts made. I am always very cost conscious when I make a modification.

The drive shafts and links have now been installed for about 200,000km with engines varying from 120-160hp.

In this first batch of photos you will see my links. These are simple ERW tube 1" diameter, with mild steel bosses. The bosses are brazed using what Aussies call "silver solder" or COMCOAT silver 45. I used 1/2 ball joints so they would mount to the existing fasteners for the lower links. All ball joints are RH thread. Half a turn provides accurate setting of the suspension. 

[EuropaTC]

Excellent, I'm looking forward to the next installment.  Your take on mounting the top link is an interesting one, I don't think I've seen anyone do that before.

Brian

[BDA]

I'm interested in the next installment, too. A friend who is building an S2 with a Ztech is implementing your design and I've been following his progress.

My understanding is that you are preserving the original geometry and taking loads off the drive shafts. I understand that the rear wheel bearings were a weak point in the S2s. Does your mod help that situation?

[Bainford]

Yes, I'm very interested as well. I'm interested in the modifications and the reasons for them. Cheers 

[Lotus 47]

I have found the rear wheel bearings to be Ok. My BMW stub axle conversion has a 30mm shaft, so the inner bearing is now a standard 6006-2RS. The 2RS means the bearing is fitted with 2 Rubber Seals. I might be onto my 3rd set of of rear wheel bearings after 29 years and 250,000km.

Here are a few photos of the CV, the mounting flange and its proximity to the inner upper link mounting brackets.

I've also added some photos from inside the bellhousing to show the tightly bunched bolts

[Lotus 47]

I'll get some more photos of the drive flange, and show how it replaces the existing Europa bits. There are a few things to observe for the uninitiated!

This next photo shows the forward mounting for the trailing arms. I pulled the engine out last weekend and thought I should take a picture of the mount in situ. I have more photos buried on a hard drive somewhere. I'll dig them out.

I never liked the rubber bushes at the front of the trailing arms. They were designed for axial load in the rear suspension of a Rover P6. My original ones were stuffed, and I bought new replacements, but they looked dodgy to me. So after fitting ball joints and upper links at the rear of the trailing arms it made sense to locate the front of the trailing arms precisely with ball joints.

The bolt is 7/16", so I bought 2 generic 7/16" ball joints. I machined a tube about 25mm long, which would accept the ball joint inside with a light push fit. The wall thickness of the tube is about 2-3mm to fit. The rest is 3mm flat plate and some simple stiffeners. I used a stick (arc) welder to make these 20+ years ago and they are still working perfectly with no signs of wear to the bush, or cracking of the fabrication.  I also made a steel spacer so I could re-use the existing 7/16" bolt.

Note that the ball joint is held in by simply crimping or distorting the tube. Crude but effective! No point in over engineering.

Cheap & cheerful, and very effective. I did experiment with different rubber bushes, and it was a complete waste of time. I found under hard acceleration the car squirmed. You could feel the rubber bushes deflecting each side which cause a touch of rear wheel steer.

Now you can hit the accelerator, drop the clutch, light up the rear wheels and it will launch straight.

This is one of my favourite mods because it is so simple, and one that is rarely mentioned.

[BDA]

Nice mod, Richard! It looks very efficiently done (on many levels)!

What am I missing? That picture is taken from the inside of the backbone, right? (it seems like it would be easier to adjust the rear toe if the bolt were turned around - i.e. we would see the bold head in this pictures - another reason why I think I'm missing something) The crimps in the tube keep the ball joint from going into the backbone. What keeps it from falling out?

I have found with the rod ends on my rear suspension that they wear pretty rapidly. After a few thousand miles (don't know how many because my speedo didn't work then) the rod ends lost all their preload and they could easily be moved in the race. Obviously, they aren't worn out but I was concerned enough to get rubber boots for them. It sounds like you don't have any issues with the ball joint wearing out? Do you think that's because it is shrouded in the tube or do you have some sort of seal to protect it (given how simple you made it, I thinking not).

I remember the bolt fits either the trailing arm or the original rubber bush but I don't remember which. Is it the trailing arm?

Has your toe setting been very stable? Have you had to adjust it over time?

[TCS4605R]

I have always thought that the rubber in the trailing arm mounts and in the gearbox mounts at the rear of the frame deflect enough to change the rear toe-in when you back off the throttle or brake hard.  My thought is this rubber deflection is what can make the car 'tail happy'.  Anyone have any thoughts on this?

[Lotus 47]

Nice mod, Richard! It looks very efficiently done (on many levels)!

What am I missing? That picture is taken from the inside of the backbone, right? (it seems like it would be easier to adjust the rear toe if the bolt were turned around - i.e. we would see the bold head in this pictures - another reason why I think I'm missing something) The crimps in the tube keep the ball joint from going into the backbone. What keeps it from falling out?

I have found with the rod ends on my rear suspension that they wear pretty rapidly. After a few thousand miles (don't know how many because my speedo didn't work then) the rod ends lost all their preload and they could easily be moved in the race. Obviously, they aren't worn out but I was concerned enough to get rubber boots for them. It sounds like you don't have any issues with the ball joint wearing out? Do you think that's because it is shrouded in the tube or do you have some sort of seal to protect it (given how simple you made it, I thinking not).

I remember the bolt fits either the trailing arm or the original rubber bush but I don't remember which. Is it the trailing arm?

Has your toe setting been very stable? Have you had to adjust it over time?

1 - the photo of the trailing arm bush is taken from inside the chassis

2 - the bolt heads are on the outside, because the trailing arm is VERY close to the chassis, and there is not enough room for a nut and washer

3 - the steel bracket I fabricated has a clearance hole for the 7/16" bolt. Lets say the hole is 1/2". That stops the ball joint from falling outboard. A picture tells a thousand words and I don't have a picture on hand.

4 - My first upper link design was fitted to my 4 speed, and I used ball joints with nylon races. They pounded out in no time. So spend the money here and buy ball joints with stainless steel balls and stainless races, with a Teflon insert.

5 - the bolt in the front of the trailing arm is 7/16". There is a steel bush welded in to the trailing arm, with a 7/16" holes through it. I didn't want to unnecessarily modify the trailing arm, so I kept it standard and re-used  the original bolt.

6 - I particularly dislike the 105E Ford engine mounts and rear gearbox mount (R16 part) They provide heaps of compliance, which means the engine can roll around like one of these silly emojis

As soon as you drive the car hard, the engine and gearbox are jerking around all over the place. You go from 2nd gear and can't find 3rd cos it ain't where it used to be. The twin cam went some way to solving this by adding a decent mount to the rear of the box. You can clearly see my solution in the "bare chassis " photo 

7 - my rear suspension settings are stable. I run 5.5" Cosmic mags and 205 rear tyres. I trimmed the rear guards to make this fit with the original suspension, and my twin link runs identical track as far as I can tell. The camber is no more than 0.5 degrees negative. I like to run the tyres fairly square to the road to maintain a big tyre contact patch. I run about 4mm toe-in. That is a difference of 2mm per side between the rear of the tyre and the front of tyre.

[Lotus 47]

I have always thought that the rubber in the trailing arm mounts and in the gearbox mounts at the rear of the frame deflect enough to change the rear toe-in when you back off the throttle or brake hard.  My thought is this rubber deflection is what can make the car 'tail happy'.  Anyone have any thoughts on this?

Hi Tom,

I see you have found my thread!

In the previous post you'll see my thoughts on the rubber in the standard set-up. I am not a fan!

On a road where you have 2 lanes , often I would find the car darting all over the place as I changed lanes.
Fitting ball joints helped.
Fitting the twin cam style rear gearbox mount helped.
Fitting different engine mounts helped. MORE ON THIS LATER
Understanding what the front suspension was doing helped. THAT'S A WHOLE NEW TOPIC CALLED BUMP STEER!

There are many many interlinked issues going on in the rear, and I will try and address all of them.

A standard 80hp S1 is a delightful and nimble car to drive. Put 100hp or 120 hp into and S1 or S2 with fat sticky tyres, and things start to move, loosen, break, etc.

Hopefully I can answer all your questions on line here, so they can be shared with everyone, but feel free to contact me on email richard.mann047(at)gmail.com

Cheers!

Richard

[RoddyMac]

Richard,
I'm very interested in seeing the CV drive flange.  I'm going to running VW Golf shafts on my car and I've picked up a set of 100mm inner flanges from a VW gearbox, but I'm undecided on the way to adapt them.  Did you machine up a complete output shaft, or did you cut and weld the Lotus (or Renault) output shaft to the Alfa output shaft/flange?


Rod

[BDA]

Thanks for the answers to my questions. But...

3 - the steel bracket I fabricated has a clearance hole for the 7/16" bolt. Lets say the hole is 1/2". That stops the ball joint from falling outboard. A picture tells a thousand words and I don't have a picture on hand.

So what you're saying is the plate has a bigger hole than the bolt (1/2") and you crimped the tube after you put the ball joint in?

Theoretically, your alignment shouldn't change. It's nice to know the theory holds sometimes!

[Lotus 47]

Yes - I installed the ball joint then crimped the tube on my fabricated bracket.

More photos below.

The outer bracket is attached using the 4 x 5/16" UNC bolts in the aluminium upright. So no load goes thru the steel trailing arm. I did try bolting to the trailing arm but it started to distort.

[Lotus 47]

and another

[Lotus 47]

BMW stub axles - all of this stuff has been posted for some time now, but I'll repost it here so every thing is together in one spot.

The Microsoft Word document (if it loads) details the stub axle change using a fixed length drive shaft, but the installation is not any different to the CV drive shaft conversion on my car.