CarYenta

Good idea on the foam on the hood rails. Does it make it more difficult to close? I got some ppf pieces from premier paint guard a long while ago that I've been meaning to put on https://www.premierpaintguard.com/car_ppg/caterham_620r.aspx

Thanks, I agree I don't know what the actual mechanical limits are for these studs, and that more is better. I don't think they are triumph studs. Another calculator showing the min to nominal range is 5.5 mm to 16.5 mm for M12x1.5. Yet another rule of thumb I've seen for M12x1.5 is 6 turns minimum, 12 turns nominal. If my 18 mm is as I tested 12.5 turns, 17 mm is 11.8 turns. I am convincing myself :P

Oh nice! Looks like I measured 10 mm but these are M12x1.5 studs most likely, so 12*1.5 = 18 mm, 1 mm short of the 17 mm I'm thinking about. But, using the equation in the link, d = diameter of thread p = pitch of thread thread engagement length = 2 * tensile area / (pi/2 * (d - 0.64952 * p) tensile area = pi/4 * (d - 0.9382 * p)^2 simplify your pi thread engagement length = (d - 0.9382 * p) ^2 / (d - 0.64952 * p) thread engagement length = (12 mm - 0.9382 * 1.5)^2 / (12 mm - 0.64952 * 1.5) = 10.2 mm Which is 0.8 * d as the bare minimum. That is a lot shorter than 1.5 * d which is probably a real-world safer value. Therefore I think 17 mm is good to go.

Straightened out my headlights, they were set to UK angle as seen here: Suspension felt good around town, pretty darn smooth at low speeds over terrible roads. On the highway, it's very busy and a bit bouncy. Realized I never actually checked tire pressures and they were at 25-30, brought down to 22 to try that. But that got me thinking that the car felt under-damped on the highway very similar to how my Miata with bilsteins did. Reading online and it seems a common sentiment. The other common sentiment is to buy suspension kits from meteor motorsports. Having been burned with tariffs so much lately I think I'll find a US solution. This leaves Penske, MCS, FOX. Will post some suspension measurements. The wheels: Each front stud has 20 mm of thread engagement for the stock front wheels and the lug nuts took about 12.5 turns to remove. The studs appear to be about 10 mm diameter, so with the 1.5x rule I need 15 mm thread engagement and have 5 mm extra. My front spacer adapters are 20 mm thick and the front studs are 28 mm long. The relief in the back side of the front wheels is much smaller than the rear wheels and is 6 mm. This means 28 - 20 - 6 = 2 mm extra. Since I have 5 extra to play with, I can cut 3 and have 17 mm thread engagement when using the stock front wheels. For the rear, the relief in the back of the wheel is 20 mm, the studs are 32 mm long, and the spacer is 15 mm. 32 - 15 - 20 = -3 mm of gap between the end of the stud and the wheel relief, so it should be ok as-is. Do I have any flawed reasoning to think 17 mm front stud-lug nut engagement is acceptable? Front studs: Engagement via antiseize:

Westermann half doors needed some cutting in order to fit. I initially sanded away with a Dremel to see how it would fit, but found out it was best to just make a single straight cut to get around the track day roll cage. As it comes door on left, cut on the right: Another view of the cut: View from top when installed: View from side with two poppers in place, planning to add two more and then add on some edging so I stop scratching the crap out of my roll cage:

The transition by hand does seem mostly smooth, but it's micron level precision to make it so. I'll verify what the reference values should be. I drove around today to test it out, and it's wild that that -0.01 V difference made it so so much more driveable. I am surprised. I could Seattle hill start with a car right on my butt no problem, no hand brake. For the fuel gauge, it does perform a test sweep at ignition set to run. I hope it's not the tank sensor 😬 going to grab another gauge from Bruce to test first. Another thing I noticed, is how close the tie rod end boots are to the brake calipers. These are going to get burned off the first time I get the brakes up to temperature. What do I do about this?? I see a few other forum posts, one was to add a washer (not sure how that would be safe). FL FR

Checked my throttle position sensor voltage - idle was at 0.53 V site 0.0. Site 0.1 starts at 0.54 V. Idle screw completely out (throttle closed) was 0.43 V. Fully open was 3.38 V. It seems like my idle up/down surge repetition is probably something related to thermal expansion and going from 0.53 to 0.54. I set it down to 0.52 V to see if that helps. I did notice that with very, very small throttle actuation, the throttle site value goes up to 1/4 of maximum. This is almost certainly related to the difficulty in small throttle modulations. ---> is there a mod to make the throttle cable actuation more linear at the initial actuation? Like a larger diameter butterfly Build support had me test continuity between green-black and green-black on the fuel gauge dial and fuel gauge connector on the rear left tank side and, it was good. Decided to raise the rear up a little since I was going to take the rear wheels off anyhow to bleed the brakes for the seventh, yes, seventh time trying to get more air out. Went up to 165 mm each side in the rear when loaded with my weight and kept 150 mm in the front.

Oh really, so this full droop actually has the shock fully extended already then and increasing ride height only increases spring preload?

Fascinating. I took the wheel off to measure the hub bore, so it's easier to see the sunpension also: Is it typical to have the coilovers near minimum height yet only have 10 mm distance from de Dion to side rail at full droop? I was going to raise the rear up 10-20 mm but not anymore! Is the 150 mm ride height not applicable to 620? Also look how long these springs are, 13 inches! ~50 cm end to end on the shock body. And some hub measurements if anyone or future me needs it:

I might need to put in slightly shorter studs too, will find out! Can't determine the wheel rear fascia pocket depth. No idea what the contour shape is of the nuts either on the adapter so may need a few parts. An adventure!

Going for gold (anthracite w/ polished lip actually) since the black friday sale is ridiculously cheap compared to anything custom, and have had a good time with Konig on my miatas: Konig Hyperspec 15x7 et35, cb 73.1, 11.3 lb Konig Hyperspec 15x9 et35, cb 73.1, 12.7 lb Australian Caold converters, 4x108 w/ cb 63.4 to 4x100 w/ cb 73.1 20 mm thickness front, 1.1 lb = effective et15 front for total of 12.4 lb 15 mm thickness rear, 1.5 lb = effective et20 rear for total of 14.2 lb How it will sit compared to the 15x6.5 et13 on the car currently: front: rear:

I believe it does not have a watts linkage - this is the right hand side looking forward, there would be a second bar coming off the top of the de dion tube going towards the rear if it had a watts, right?

Changed the front toe to zero, decided to keep the rest of the alignment as-is to 1) learn what the behaviors are first and 2) I imagine the bushings will settle somewhat, changing the alignment anyways. For anyone like me wondering where the heck the flats are on the tie rods after loosening the lock nut, they are hidden under the inner rod corrugated rubber boot, so remove the zip tie, push it back a bit, and there are 11 mm flats. Every 1/4 turn changed my total toe by around 1/16".

Looking at tire options, it seems like I should probably just run 15". I see several combinations of 205/50-15 and either 225/45 or 225/50 and also three 245/40. Am initially thinking 15x7 et13 for 205/50 15x9 et25 for 245/40 with continental extreme contacts in mind for summer, then converting my 15x6.5 into the winter set with a wetter tire option.

Welllll waddyaknow, there's a sneaky shim in each side.

Also received some dpr mirror mounts which apparently donates to this forum for each order, sounds like there's a back story somewhere. Oh and my amazing ballast, looks just like me.

Update, I went to resettle the car after adding driver ballast, and that's when I noticed a 2x4 sitting further out on one side of my wheel chalks. My tape measure was hitting that and bowing out, creating an artificially long rear measure DOH! After measuring without anything in the way, there is between 1/32" toe-in and zero toe in the rear. Tape measures only go to 1/16", so that's good enough for me. Front toe with ballast is now 5/16" toe-out. With my ballast, ride height currently from factory is: FL - 150 mm - rear lower wishbone, lowest part of frame rail (the curve of the bodywork makes it kind of vague to read from the outside. FR - 150 mm RL - 155 mm - at the A frame connection point of the lower frame rail at the front of the rear wheel RR - 150 mm Caterham guideline is 150 to 190 mm front and 15 mm higher in the rear. I'm not sure I can go much higher in the rear without contacting the dedion tube and frame rail. I will raise the car and see what I can get to. Front: Easier to do this when not taking a picture Rear: DeDion vs frame rail: Sitting on ground. How much droop will there be when raised? Will report back.

Do you have a recommended rear toe and camber value? For front suspension, miatas are double wishbone too, so wouldn't it be similar up there? De dion is a mystery to me!

Out of the box, it seems to drive straight luckily. I don't have a method to determine thrust angle, but it feels straight and the steering wheel is straight. Are you saying to shim the rear to reduce the 1/4" toe in, since under load they toe-in even more? I have the S suspension = nice and soft so am assuming lots of camber will help. I run -2.0 degrees camber on my miata front and back with xida touring and it's about perfect. But, I have big tires and low power on the miata, so I assume I want the 620 rear camber to be less, like -1 to -1.5 but will keep the front camber large to start just for simplicity and move as desired.

My rear toe-in measured via toe plates and tape measures is currently 1/4" total toe in across about 22 inches (toe plate width). With an isosceles trapezoid calculator I get 0.33 degrees each (0° 20' each) or 0.66 degrees total toe in (0° 40' total toe in). This seems kind of high compared to other cars I've had. Do people shim this out to get closer to 1/8-1/16" toe-in? Or do de dion just like to scrub tires? This is a 98% road car. 66.5" across front of rear wheels 66.75" across rear of rear wheels Front wheels came from the factory at 3/16" toe out. Am planning to set to zero to 1/16" toe-in front. Haven't measured the camber yet but the front looks like >3 degrees. Would bring to about 2.5 I think if it seems like I'm never using the outer edge of the tire.

Nice! I saw a gap and didn't attempt any screw removal. After cutting and seeing 5 absolutely tiny wires, my face was 😬

Soft bits for sevens half hood installed: The side straps are not long enough to utilize the velcro as a hold-down. This seems like not how it is supposed to be. Otherwise, fits great. CaterLED tail lights installed: Driving lights on only Driving lights off, 4 ways on: Blinkers are slightly less visible than I would have hoped when the driving lights are on as the red and yellow are on at the same time. Instead of removing the boot floor which seems rather difficult since I have a liner and fire system and gas filler to remove, I just cut the cable and ran it though a side gap and resoldered, then installed the connectors. Right hand side of boot shown. The same gap exists on the left hand side. Is only as fast as your soldering skill 😂 The little lightly-colored thing next to the cable at the threshold of the boot floor is just a fuzzy.

True, the lightest cars I've had were my old NA miata which I ran 225's on and then my current nd3 miata with 245's, and this is 1000 lb lighter but +130 extra hp. On the NA, I had 15x6 with all seasons when I bought it, then went to 15x7.5 wheels for 205/50 direzza ZII tires, and the lack of grip compared to my prior car (E36 M3 on 245/40 17x8.5 direzza Z*) made canyon driving feel slow, nervous and outright dangerous even with a good alignment. I then got 15x9 with 225/45 r-s4 and it was a real game changer. Much much more grip and confidence even though it was a track tire and not an autocross tire that works better cold. With the ND3, I just went straight to 17x9 with 245/40 PS4S as I like it big, and really liked PS4S on my GT3 compared to the cup2 it had for wet performance and sandy roads. Many miata people disagree with me, but I love grip at all moments, and I imagine the caterham would be similar? Lots of sandy leafy dirty bumpy off camber PNW streets. Why is the max 15x6.5 but for 13" is 13x8? I'd assume there would be even more tire bulge on a 13 with larger tire profile? I just measured in my wheel well very roughly and there is ~3-3.5" clearance paint to tire, and ~2.5" clearance tire to the trailing arm (not sure the correct name for it), and 0.5" on the outside. It seems like a correct offset 15x8 would fit and allow tire flex just the same as a 13x8, assuming the sway bar/drop link doesn't interfere. Am I not noticing what would be the rubbing issue on the inside? De dion is new to me. Since I currently have 195/50-15 it seems like that would have probably a similar contact patch as a 205 in 13"? So would ideally have larger than that in the rear. Having now browsed the tire selections for 13", I'm pretty set on a 15" option since, while still measly in options, there are so many more tires to choose from than 13". BUT If it's way cheaper to get apollo's in 13x6 and 13x8 than a custom 15x7 and 15x8/8.5/9 (I'd have to measure more carefully) I might end up doing that. It seems tricky to find wheels that aren't seemingly made from lead.

I really like the 13" apollos. Except like you say they probably only have summer tires and I already have brand new 15" avons 😭 Do you think that wider than 13x6 and 13x8 wheels would fit? Anyone know the widest 15" wheel and tire sizes that fit?

What if I don't like how CSR wheels look 😬 I guess I'm less worried about what wheels there are as I can get them custom made, but am more worried first about max tire sizes in useful tire models so that I can choose an appropriate wheel size, ideally a 13".