MattB

It could be that the plate that depresses the brake switch plunger isn’t properly set, ie it isn’t fully depressing the plunger. Easy enough to check with the pedal box cover off. MattB

https://www.demon-tweeks.com/uk/pitking-products-universal-alloy-race-mirrors-pair-1097933/ ?? MattB

Doesn’t adding plates make it louder? MattB

Jonathan Thanks, but unfortunately the factory diagrams are no use whatsoever in this case. I do know that it’s a red/white wire I’m looking for. I’m hoping that someone has a photo taken when they had their scuttle off that shows the physical wiring arrangement out of the back of the fusebox. I just need to see where the beginning of the wire is, so I know where to splice in the dimmer. MattB

Reference the dash lights, I too find the gauge backlights in my 2022 420 incredibly bright (not the blue full beam light). I talked to the Caerbont guys at Goodwood last year and they said that the led output was as specified by Caterham, but if I sent them all my gauges they could replace the leds with less bright ones. Since I’m not prepared to go through the hassle and cost of removing/posting/waiting for/replacing all of my gauges just to fix yet another piece of poor Caterham engineering, I asked if I could fit a dimmer, and they said that they thought a PWM dimmer should work. Looking at Andrew Revill’s beautiful wiring diagram for a K series (Andrew - can we have one for a 420 pretty please?) it seems that the lamps for all of the gauges are fed in series from a single source - a red/white wire from the fusebox. Assuming that the wiring in my 420 follows the same principle, I just need to find where that wire comes out of the fuse box and splice in something like this https://www.demon-tweeks.com/uk/stack-led-dimmer-switch-for-stack-gauges-stast269114/ or this https://www.pilotlights.net/pwm-dimmer-12-vdc-high-power-7a-easy-fast-terminals-12-14vdc. Does anyone have any photos of the wiring coming out of a 420 fusebox? I’m struggling to see anything under my dash, even with the help of a mobile ‘phone camera. MattB

Now that’s bar service!

The current owner’s manual does indeed recommend 23psi for the ZZS tyres. Avon, however, recommend 18-21psi for the same tyres (see their guide in the technical pages of this website). I’ve found Avon’s advice to be better … MattB

If the dimensions really matter (eg if you’re worried about a 185/60 tyre fitting under the wheel arch) the best thing to do is check the details on the manufacturer’s website. I had 3 sets of wheels/tyres for my last car (road/winter/track), all supposedly 215/45/17s. They differed significantly in width and diameter. MattB

185/60 means that the sidewall is 60% of the width, ie 111mm. A 185/55 tyre technically has a 102mm sidewall, so the difference between the Toyo and the Avon is nearer 9mm. I appreciate that actual dimensions are often different to labelled dimensions (especially for track/race tyres), so that 9mm could actually be smaller or larger. MattB

They weren’t fitted to my factory built car when I collected it in January 2022. MattB

Mk3 MX-5s with the Duratec engine had a known issue with the wires to the coils, particularly cylinder 1. You can buy a replacement connector with 8” (IIRC) pigtails to solder into the loom. People also removed the plastic coil cover because it squashed the wires, exacerbating the problem. MattB

https://www.caterham7diaries.com/post/fuse-and-relay-box-layout MattB

Caterham tweaked the idle on my 420 as part of the first service (the one where they get you to pay for them to check if they built the car properly …). MattB

I bought some spares for my 2022 420 on eBay. Do a search for “Spare Keys x2 for FIA Battery Master Cut Off Switch Kill Switch GRAYSTON KEY55”. MattB

Radtec haven’t updated their website, so this page doesn’t yet show the option of buying just the radiator: https://radtec.co.uk/shop/radiators/caterham/r300420r-road/ Just give them a call when you want to order one, as they also need to know the model number of your fan. Be aware that they don’t have them on the shelf. Mine took 6 weeks … MattB