Please re-read the information I posted...
That is Toyo's own recommendation - 5.5-7.5
(Backed-up by George Polly, as it happens.)
Far better to go with what the manufacturer's recommend, rather than idle gossip and speculation I find

Ok - time for an update, as I have eventually got around to fitting the new Toyo tyres on Eugene...
(Thanks to Uncle Albert!)

As mentioned earlier I went for Toyo Proxes R888R
2x 185/60r13 for the front - 2x 205/60r13 for the rear - both on the same 6" rims.

I've only done 40 or so miles so far, but I have to say they are very, very impressive.
I know the 021Rs were old, so a fresh set of just about any rubber would feel good, but these feel just amazing so far.
Nicely compliant, and not at all harsh compared to the 021Rs, but very, very grippy in the warm weather we have today.
Inflated to 18psi all round as a starting point.

And they look great too - the 205/60r13s in the rear do not at all look 'balloony'.

And the ground clearance is not at all too compromised - 80mm to the lowest point of the sump with the lower wishbones (rear arm) parallel to the ground.

This is looking to be a good choice!

Looks better with more rubber in the rear arches

Not been on for a while but thought I would add my observations.

Had a Caterham since 1989. used Yoko 001HFR (very good), Yoko 048R (disliked them) and had 3 sets of Yoko 021R (loved them). Also used Avon CR28 Sport on the road (3 sets) plus I have had more than a few sets of specialist hill climb tyres including slicks and list 1A stuff. But the Yoko 021R has been the best all rounder and excellent value with good wear rates as well.

Needed a new set for this year but no more 021R's. Looked at many and decided to try a set of Uniroyal Rain Expert in 185 60 14. Have to say that I am more than happy especially considering the fitted price. I was a bit worried about the soft sidewalls creating poor handling but the car feels no different to how it did on the 021's pressing on in Lincolnshire. Expected some tyre squeal but all has been silent so far, probably not trying hard enough.

Worth a try for tight arses like me.

I've not tried the Rainexpert 3's, but I know a few who have.
My issue would be 'block/tread' movement, making them less precise in turn-in, etc.
(Basically squidgy tread movement...)



I also loved the 021Rs -especially for the price - but, the R888Rs are bloody amazing!

021r's had large tread blocks but that never made those feel imprecise. Like I said above the Rain Experts feel no different in normal fast road use.

Read to many stories of cracked rubber after winter storage to even consider Toyo's. The chap I got the the Uniroyals from is a Toyo motorsport retailer and he would not recommend them to anyone for road use.

Having just done 2200+ miles across Spain/Portugal/France in some of the worst weather imaginable, the R888R's were amazing!
So much better than the 021R's previously on Eugene.
(Donut had the same tyres, and will basically say exactly the same...)

Update

After a full summer on the Uniroyal Rain Experts I am still more than happy. Its been mostly dry (as we know) but I did manage to get caught in a couple of storms and the car felt well planted with no tendency to go light at the front in those dreadful ruts caused by HGV's that fill with water.

Despite my best effort on a deserted industrial estate I could not induce any tyre squeal on the roundabouts but I think its fair to say the front end did not feel as precise as the Yoko's did when doing that sort of thing, it did wash out but nothing happened suddenly and the back end felt really secure.

But if looks matter they are not the tyre for you, normally seen on basic hatches which does not give much street cred. Am I bothered, not one bit.

To be honest, its the lack of crisp turn-in that I found an issues when I tried another 7 with the Uniroyal Rain Experts.
The R888R's are so precise, the difference was obvious, and felt like the steering had been partially disconnected.

And the way the R888R's handles to rain in Spain/Portugal was amazing.
They handle way better than they deserve!