620 S Build

[CBuff]

I like my 13” Apollo staggered set up 6” front 8” rear.  My zzs are about used up. Will likely go with r888 until nova gets the zzs back in production.  I loved the zzs. They were great for the road and track. I have had a few runs in the rain with them and they performed well (still a little dicey with such a light car).  But not sure you can really address this without serious compromise the dry handling. I would def recommend the 8” rear. It looks right from the back. (The 13” does look a little lost on the rears from the side - but for the handling benefits worth it). 

[CarYenta]

3 hours ago, CBuff said:

I like my 13” Apollo staggered set up 6” front 8” rear.  My zzs are about used up. Will likely go with r888 until nova gets the zzs back in production.  I loved the zzs. They were great for the road and track. I have had a few runs in the rain with them and they performed well (still a little dicey with such a light car).  But not sure you can really address this without serious compromise the dry handling. I would def recommend the 8” rear. It looks right from the back. (The 13” does look a little lost on the rears from the side - but for the handling benefits worth it). 

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?

Edited November 15, 2025 by CarYenta

[Croc]

12 hours ago, CarYenta said:

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".

 

 

 

I thought you wanted to stay on 15s just in tires with better tread. 

 

13s with better tread.  Thats the objective.  Got it now - just call me slow on the uptake.     

[CBuff]

10 hours ago, CarYenta said:

Do you think that wider than 13x6 and 13x8 wheels would fit?

I defer to the smarter people here about what can fit.  I did need to retrain my thinking when i got this car. Driving big heavy bmw before this I was always trying to get as much tire width as possible. With such a light car the slightest change has a dramatic effect. And the suspension, tires , sidewall height all have an effect on handling. I just deferred to the more experienced folks here( @Croc and others ). 
 

the 13” staggered has been great and I don’t have any regrets.  Not sure how the extra power from the 620 factors in.  
 

my wet weather handling is acceptable.  I don’t fear driving in the rain (although my zzs are pretty much slicks at this point - so extra care is needed). But when new with tread they were fine in the wet.  I’m not running at 10/10 on the road, especially in the wet.  For me having something work in the wet and great in the dry is the best.  On track I’ll go full tilt in the dry and dial it back for the wet. The majority of my time I am aiming for dry driving weather so that’s what I try and optimize with the tires. 

[Croc]

11 hours ago, CarYenta said:

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?

 

13x6 and 13x8 are the only sizes Caterham are going to offer in the Apollos.

 

With the horsepower you have you really need a staggered set up.  Anything north of 200hp benefits from the staggered wheel set up.  

 

Not sure if you can put bigger than 13x6 on the front.  I think a 13x7 will fit front depending on the tire but I suspect then you would need watch out for certain tires where sidewall rubs stay.  As a result 13x6 is safest given limitations on rubber choice.

 

Similar on back.  Max is likely 13x8 as you would find the sidewall rubs the inner paint of the rear wheel well.  Even on a 13x8 you have to pick your rubber.  Youu are fine on Toyo R888R (and formerly Avons).   However, thinking of some other cars at NJMP, the sidewall has taken paint off on the inner wheel well with some of the Michelin F3 slicks they are using.  About to do a test of my CSR 13 inch Pirelli P-Zeros on a De Dion rear wheel and car to see if they work for clearances.

 

Now, one thing to keep in mind is that I find (along with a few other handy drivers in the UK I track with) that Caterhams work better in the wet on a 15 inch wheels than a 13 inch wheel even with equivalent tire spec.  The opposite is true in the dry.  The logic for this is in the wet, the 15 inch wheel set up has more unsprung weight which in a light vehicle helps you cut through surface water to the road/track surface and give better drip.  In the dry, the unsprung weight is better being minimized by use of the lighter 13 inch wheel set up to get better grip/performance.  

 

In an ideal world you would have a set of 13s for dry and 15s for wet but thats not practical for road purposes or your wallet (wife, garage space, etc).  

 

For 15s, the 15x6.5 is the max on the rear of a deDion car - clearance issues otherwise.  Thats why people  drop to 13s to get to the 13x8 wider rear OR use the Beachman spacer solution to allow the CSR wider rear (CSR offsets are different).   When I was there 2 weeks back, Bruce had a 420R in his shop with the latest BMW-copied-look CSR wheel fitted - the wider rear looks right - fills out the rear wings nicely.  He was talking RE71RS tires which are good all round performers in larger rim sizes - that might be his wet race control tire for his Caterham series?  If you do not like the BMW Sport CSR copy wheel then look for a set of CSR Orcus wheels or go custom.  

 

Back to your original question.  If you drop to 13 inch wheels AND want an aggressive tread pattern for your sunny patch of earth where it always pisses down, then one idea - Go for a square set up allround of Toyo RA1 205/60/13   Decent all weather performance.  The RA1 is far better in the wet than the R888.   Some thinking is needed on whether these will rub on the front stays (bending is your friend here).  In theory a 205 tire will fit a 6x13 wheel.  It will not fit a 8x13 though.  I have not checked if rolling diameter is close to your existing set up.

 

Option 2 - Maybe a square set up of 6x14 that you could put the Yoko A052 185/55/14.   Despite what the tread pattern looks like my experience is the wet weather performance on track was better than the R888 (but not as good as the RA1).   Mind you most things are better in the wet than the R888, even my SUV.

 

 

 

 

 

[CarYenta]

11 hours ago, CBuff said:

I defer to the smarter people here about what can fit.  I did need to retrain my thinking when i got this car. Driving big heavy bmw before this I was always trying to get as much tire width as possible. With such a light car the slightest change has a dramatic effect. And the suspension, tires , sidewall height all have an effect on handling. I just deferred to the more experienced folks here( @Croc and others ). 
 

the 13” staggered has been great and I don’t have any regrets.  Not sure how the extra power from the 620 factors in.  
 

my wet weather handling is acceptable.  I don’t fear driving in the rain (although my zzs are pretty much slicks at this point - so extra care is needed). But when new with tread they were fine in the wet.  I’m not running at 10/10 on the road, especially in the wet.  For me having something work in the wet and great in the dry is the best.  On track I’ll go full tilt in the dry and dial it back for the wet. The majority of my time I am aiming for dry driving weather so that’s what I try and optimize with the tires. 

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.

 

 

10 hours ago, Croc said:

 

13x6 and 13x8 are the only sizes Caterham are going to offer in the Apollos.

 

With the horsepower you have you really need a staggered set up.  Anything north of 200hp benefits from the staggered wheel set up.  

 

Not sure if you can put bigger than 13x6 on the front.  I think a 13x7 will fit front depending on the tire but I suspect then you would need watch out for certain tires where sidewall rubs stay.  As a result 13x6 is safest given limitations on rubber choice.

 

Similar on back.  Max is likely 13x8 as you would find the sidewall rubs the inner paint of the rear wheel well.  Even on a 13x8 you have to pick your rubber.  Youu are fine on Toyo R888R (and formerly Avons).   However, thinking of some other cars at NJMP, the sidewall has taken paint off on the inner wheel well with some of the Michelin F3 slicks they are using.  About to do a test of my CSR 13 inch Pirelli P-Zeros on a De Dion rear wheel and car to see if they work for clearances.

 

Now, one thing to keep in mind is that I find (along with a few other handy drivers in the UK I track with) that Caterhams work better in the wet on a 15 inch wheels than a 13 inch wheel even with equivalent tire spec.  The opposite is true in the dry.  The logic for this is in the wet, the 15 inch wheel set up has more unsprung weight which in a light vehicle helps you cut through surface water to the road/track surface and give better drip.  In the dry, the unsprung weight is better being minimized by use of the lighter 13 inch wheel set up to get better grip/performance.  

 

In an ideal world you would have a set of 13s for dry and 15s for wet but thats not practical for road purposes or your wallet (wife, garage space, etc).  

 

For 15s, the 15x6.5 is the max on the rear of a deDion car - clearance issues otherwise.  Thats why people  drop to 13s to get to the 13x8 wider rear OR use the Beachman spacer solution to allow the CSR wider rear (CSR offsets are different).   When I was there 2 weeks back, Bruce had a 420R in his shop with the latest BMW-copied-look CSR wheel fitted - the wider rear looks right - fills out the rear wings nicely.  He was talking RE71RS tires which are good all round performers in larger rim sizes - that might be his wet race control tire for his Caterham series?  If you do not like the BMW Sport CSR copy wheel then look for a set of CSR Orcus wheels or go custom.  

 

Back to your original question.  If you drop to 13 inch wheels AND want an aggressive tread pattern for your sunny patch of earth where it always pisses down, then one idea - Go for a square set up allround of Toyo RA1 205/60/13   Decent all weather performance.  The RA1 is far better in the wet than the R888.   Some thinking is needed on whether these will rub on the front stays (bending is your friend here).  In theory a 205 tire will fit a 6x13 wheel.  It will not fit a 8x13 though.  I have not checked if rolling diameter is close to your existing set up.

 

Option 2 - Maybe a square set up of 6x14 that you could put the Yoko A052 185/55/14.   Despite what the tread pattern looks like my experience is the wet weather performance on track was better than the R888 (but not as good as the RA1).   Mind you most things are better in the wet than the R888, even my SUV.

 

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.

 

 

 

Edited November 16, 2025 by CarYenta

[Croc]

2 hours ago, CarYenta said:

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?

 

No idea.  But you will not find a 15x8 sold by Caterham for a de Dion chassis.  You will find a 13x8 for a de Dion chassis.

 

I always understood it to be clearance issues somehow.  But I have never checked myself.  I do know it came up in a conversation with Bruce B two weeks ago when I saw a 420R with the widest set of 15 inch rear wheels I ever seen on a de Dion car.  He said it was clearance issues?  Maybe up the top of the wheel somewhere?  Admittedly he was trying to sell me on his sexy adapter spaces dooby whackers but I am immune to such temptations.    

 

However, given a de Dion chassis car accidentally fell into my garage in the last 48 hours, I plan to see what happens when I put a 7 inch CSR front tire on the rear of a 620S and measure clearance when on a lift.  I'm also planning to try a CSR sized Pirelli P-Zero slick on a 13x8 de Dion Caterham wheel.  Will report back eventually.  

 

 

 

[CBuff]

4 hours ago, Croc said:

However, given a de Dion chassis car accidentally fell into my garage in the last 48 hours, I plan to see what happens when I put a 7 inch CSR front tire on the rear of a 620S and measure clearance when on a lift

Someday I want to hear more about this…..

[MV8]

To determine what size and offset rim will work, purchase (from a tire shop that will accept returned tires) one of each size tire in the sizes you are interested in running and the tool for determining the rim size needed. Support the suspension. Pick up a few five gallon buckets to set in the rear and fill with water or remove the springs to check bump clearance.

[CarYenta]

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.

Edited November 17, 2025 by CarYenta

[CBuff]

Yeah. I didn’t want to remove my floor either. I was able to take one screw out and raise it just enough to get the light thru.  
 

 

I didn’t want to rip the carpet out as well so I just put a strip of double sided Velcro (prickly side sticks to the carpet and the soft side faces out. It is hardly noticeable. Can’t seem to find a picture of this. 
 

I did have a strange led failure. 2 of the middle lights died a few weeks apart on each strip. Cater led sent me another one and I sourced one from Amazon for like $9.  Must have been a band batch. The current ones have worked well 
 

 

[CarYenta]

36 minutes ago, CBuff said:

Yeah. I didn’t want to remove my floor either. I was able to take one screw out and raise it just enough to get the light thru.  
 

 

I didn’t want to rip the carpet out as well so I just put a strip of double sided Velcro (prickly side sticks to the carpet and the soft side faces out. It is hardly noticeable. Can’t seem to find a picture of this. 
 

I did have a strange led failure. 2 of the middle lights died a few weeks apart on each strip. Cater led sent me another one and I sourced one from Amazon for like $9.  Must have been a band batch. The current ones have worked well 
 

 

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

[CarYenta]

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.

 

Edited November 17, 2025 by CarYenta

[MV8]

Driven wheels toe-in under dynamic load but any rear toe-out when driving is too much imho.

The front will toe-out under load. The goals are zero dynamic toe front and rear unless you are trying to tune the handling in some way.

2.5deg is excessive for touring unless you have a lot of body roll.

 

I suggest starting with one rear wheel to align to the chassis, then line up the others based on that as a reference.

 

Edited November 17, 2025 by MV8

[CarYenta]

29 minutes ago, MV8 said:

Driven wheels toe-in under dynamic load but any rear toe-out when driving is too much imho.

The front will toe-out under load. The goals are zero dynamic toe front and rear unless you are trying to tune the handling in some way.

2.5deg is excessive for touring unless you have a lot of body roll.

 

I suggest starting with one rear wheel to align to the chassis, then line up the others based on that as a reference.

 

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.

[MV8]

Jack stands and string will show thrust angle for each rear wheel. Because the chassis tapers, the distance between the stands is reduced. As high as will clear the fender, bring the string up against the tire bulges then measure to the ends of the parallel chassis rails (cowl and boot). You can check distance to the rim front and rear if you don't trust that the bulges are equal. The greater the distance between the stands, the more accurate it will be.

 

You can shim to align each one to the chassis or you can use the first one you set as the reference to set the other side.

 

The miata suspension is very different but whatever you are happy with. Just a discussion.

 

 

 

[CarYenta]

7 minutes ago, MV8 said:

Jack stands and string will show thrust angle for each rear wheel. Because the chassis tapers, the distance between the stands is reduced. As high as will clear the fender, bring the string up against the tire bulges then measure to the ends of the parallel chassis rails (cowl and boot). You can check distance to the rim front and rear if you don't trust that the bulges are equal. The greater the distance between the stands, the more accurate it will be.

 

You can shim to align each one to the chassis or you can use the first one you set as the reference to set the other side.

 

The miata suspension is very different but whatever you are happy with. Just a discussion.

 

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!

[MV8]

Identical components on seemingly identical chassis can have dramatic differences in camber gain (and other aspects) from small changes in control arm locating points. Miatas are completely different front and rear.

 

I would run zero toe and a 1/2 degree camber on the dedion until tire wear or some other situation (like roll steer or high speed instability) suggested a change.

[CarYenta]

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.

Edited November 18, 2025 by CarYenta

[CarYenta]

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.