UKC

I need a new trad rope and am unsure about the wisdom of an 8.3mm rope despite the exciting prices £65). 8mm is too thin for my liking, 9mm seems old fashioned and what do you think?

8.3 sounds ideal. I used 8mm earlier in the year, and the weight saving over the 8.6 I was used to was amazing. They didn't feel like string, either...

If 8 is too thin and 9 too old fashioned for you then 8.3 at a bargain price seems to be in the sweet spot!

Currently climbing on a pair of 7.2mm ropes and they are like shoelaces but you get used to it.

I've used 8.5 Mammut Genesis for years - perfectly good but 8.3 sounds like a step up especially at the price you are talking about 

Crikey! What make and model are they? 

I've been using 8mm halves for 10 years now and have complete confidence in them. And this from an old fouger who started out with No 4 hawser laid nylon and later became so over the top with safety consciousness we did most of the Scottish classics lugging around a pair of 11mm ropes! 

... I've been using 8mm x 50m for a while now... they weigh less and they pack up smaller and they have pretty much the same performance as that of an "old-fashioned" 8.5mm - when you're walking into mountain crags at our age(!!!) any weight saving, in my book, can only be a good thing...

Dunno which Martin is looking at, but Beal Legend 60m 8.3mm are £68 at Rock and Run

Go for it, but check if you (and your climbing partner) need to replace your belay devices.

Simond - not much thicker than accessory cord - mainly bought because they were light and cheap.  They work well but they are a little tangly.  The knot on your harness is disconcertingly small.

Ignore the diameter, look at the density instead. It's a far more accurate guide to how much material there is contained in the rope. Also have a look at the sheath %, which along with the density tells you how much sheath material there is, which is a good guide to the ropes inherent durability.

For example, if you compare DMM's 8.0 and 8.5 ropes, they are very different beasts. The Couloir is 43g/m2 and 39% sheath, which gives 16.8 g/m2 sheath material. The Pitch is 49g/m2 and a whopping 49% sheath. With 24g/m2 of sheath it has over 40% more sheath material than it's skinnier cousin - the Coulior is a rope for ice climbing, the Pitch more a beefy trad workhorse. Petzl Rumba 8.0 is 18g/m2 of sheath and seems a good in-betweener, mine is lasting well so far.

It's the stretch (no doubt that's not the right technical term) that bothers me with the thinner ones.  I have a 60m 8.1 for winter as, in that situation, stretch seems useful especially when combined with less weight.  But for trad I have stuck with 8.6 because I often second routes that are hard for me and sometimes need all the help I can get.  I tried 60s for UK trad for a year or so (admittedly at 8.6 so heavier than my previous 50s) but went back to the 50s.  I usually find that I struggle to do pitches longer than about 45m anyway, even when there is little to cause drag. The ropes just seem to get too heavy.  Also, it takes longer to coil them and drag them up the route.   I only really want to do all of that extra coiling if I'm getting some advantage.  In winter, given more marginal gear and the greater chance that I might be forced to fight my way up to a belay that is more than 45m away, I decided thinner was OK because it's lighter.

So, my solution is to have a 50m 8.6 and a 60m 8.1.  I can pair them if necessary and I can also team up with somebody who has a 50 or somebody who has a 60 as needed.  The days when I am willing/able to afford a pair (let alone two pairs) are long gone.

Maybe I have got the thing about stretch wrong.  I hope I have, as I am small so anything I can do to lighten my sac would be good news.