This is the first time I have fitted uprights without the “special nuts” which need a special 3/4” thin-walled long-reach socket to fit. Its replacement is the “Top Hat” spacer and a standard 1/2” UNF 1/2 nut. I found fitting this top hat spacer difficult, tight is not the word!
Get the correct side 
Spacers and Nut 
“Top Hat” Spacer in location
I tried reversing the spherical bearing as per Caterham 662A Workshop Notice, but it still wouldn’t fit. I eventually realised that the cause of my problem was the temperature difference between the car (stored in the cold garage) and the top hat spacer which was at relatively warm room temperature. The solution: putting the top hat in the freezer for a few hours so it shrinks, if only by the smallest of margins. This made all the difference, and getting the spacer nearly into place was now a lot simpler.
The uprights and ball joints are a mixture of metric and imperial fittings. If you are unsure what tool to use, just look at the lock nuts: as a general rule if the nylon is blue its a metric fixing, white is imperial. This certainly the case for all the fixings supplied in my kit.
I removed the nuts from the track rod and upper wishbone ball joint and also took off the plastic cover from the track rod ball joint, before the top hat came out of the freezer. The final bit of preparation was to slide the thin spacer onto the upright. It only wants to go one way, so don’t force it.
Remove the nuts 
Ready for upright install 
Don’t forget the thin spacer (R spec only)
Once I retrieved the top hat from the freezer, I inserted it into the lower wishbone spherical bearing, before the upright was lowered into the lower wishbone spherical bearing. Be careful not to push the top hat out of the bearing. Next, I fitted and tightened the 1/2” UNF nut to the lower wishbone / upright, while the top hat was still cold, to pull it into its final position. Hold the upright at all times so it doesn’t fall.
I suggest adding the track rod ball joint at this stage – even if it’s just finger tight – to stabilise the upright so it doesn’t swing into the side skin.
Lift the wishbone into the ball joint 
Start the nut
Now fit the top ball joint from the upper wishbone into the upright. Lifting the upper wishbone to get the thread of the ball joint into the hole is simple enough, but not enough thread was visible to attach the tightening nut. I solved this by lifting the lower wishbone with a jack. The tightening nut is a non-nyloc nut to make pulling the ball joint into the taper easier. With the use of a 6mm Allen key and a 22mm ring spanner the upper ball joint taper is pulled tight with the tightening nut, then the tightening nut is removed.
Not the hex in the ball joint 
Using the Allen key to stop the ball joint from turning 
Remove the nut
Next remove the axle nut (3/4” ring spanner) and discard the washer.
Remove the axle nut 
Discard the washer
Fitting the wing-stay wasn’t as simple as expected. Locate it on the upper ball joint first, then slide it onto the axle. However, as you can see from the photos, my LHS wing-stay didn’t look like it was going to fit. Derek from Caterham Cars confirmed that this can sometimes be a problem, and the solution is to lift the wing-stay using the wing-stay arms. This seems brutal, but it did permit the wing-stay fitting.
Needs a lift to get the axle into the wing stay 
Fit the top first
Now it’s just a case of tightening all the fixings. The upper ball join is difficult to access, so a wobbly extension bar is or similar needed. The track rod end ball joint may need pressure from the top to lock the taper, but hand pressure is sufficient.
I torqued the track rod ball joint to 34Nm. I found this information in the old manual (2015C), as no torque setting is listed in the new manual (v1.2 and v2.0). The axle nut is torqued to 81Nm, the top ball joint to 61Nm and the lower upright nut to 54Nm.
Tools Used
- 3/4″ 3/8 Socket
- 22mm 3/8 Socket
- 17mm 3/8 Socket
- 3/8 Extensions (wobbly)
- 3/8 Ratchet
- 22mm Combination Spanner
- 3/4″ Combination Spanner
- 3/8 Torque wrench
- Jack and lifting block
caterham420detailedbuildblog.co.uk 
One option for torqueing the upper ball joint is the Draper 64534 torque wrench. This is rated at 10-80Nm so the 61Nm required is within the performance envelope. A 22mm socket fits directly onto the 3/8” drive and because the wrench is quite short it fits comfortably between the suspension and the body albeit it needs a firm push/pull to get to 61Nm. The Draper is not expensive, less than £25, but when I checked it against more expensive and sophisticated digital wrenches it’s performance was in line.
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To Nick’s comment above, I managed to get a 1/2″ 22mm socket onto my 1/2″ torque wrench to torque the upper wishbone ball joint nut. Just. A 1/2″ torque wrench is a bit long for this but it still worked.
It’s worth pointing out that when you use the temporary nut AF to tighten the upper wishbone ball joint down onto the upright and wingstay, it needs to be FULLY tightened to lock the ball joint taper shaft and prevent it from rotating before you remove the nut again. Unless you do this, once you remove the temporary nut the taper shaft will still spin when you try tightening the actual nyloc nut afterwards. The temporary nut has no nyloc and is easy to tighten so doesn’t turn the taper shaft, whereas the actual nyloc nut is stiff and tends to turn the taper shaft unless the taper is locked downwards with the temporary nut first.
Once I’d fully tightened the temporary nut, I then clamped the lower wishbone and upper wishbone together to prevent the upper wishbone ball joint taper from lifting out of the upright again as the temporary nut was removed. I then removed the temporary nut and tightened the actual nyloc nut without any problems. Then you can remove the clamp.
Suffice to say I learned this the slow way, by fiddling around with the nyloc nut for a while before I realised it wasn’t tightening and the ball joint taper shaft was spinning instead…
I also used the trolley jack (as per Chris’s recommendation) to lift the bottom wishbone before doing any of this, as the suspension sags under its own weight otherwise. Works well.
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Hi,
I am assembling my 420r kit and am a little confused, your photos show a plain spacer and another spacer that is stepped in profile – I assume this is the one you describe as the top hat.
The plain spacer fits between the lower wishbone and the bottom of the upright, but where does the top hat spacer fit ?
I cannot find reference at all in the assembly manual and am stumped.
Any help would be appreciated.
P
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Hi Patrick, I have updated the photo description (last photo, of the first collection of three, on this post) that shows the top hat spacer in location before the upright is installed. If your still confused, use the contact me form, and I will send you a copy of the workshop notice Caterham produced for the Top Hat spacer back in 2018 (shows how long they have had to update the manual). Hope this helps, and good luck with your build. Chris.
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Chris,
I have had a play and I have now installed the top hat into the bottom of the lower wishbone – it now seems to fit – thanks.
Regards
Patrick.
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[420R S3, Q1 2022]. You will need to drill a hole in the end of the wing-stay arms for the repeater earth cable. I highly recommend you do this before fitting the wing-stays, as it’s much easier now than when they are fitted.
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