UKC

What diametre of double ropes (60m) would you buy? 8.0 or 8.5 mm? Mainly limestone in my area. I like to go light, but security also counts. Several options out there like Fixe Fanátic (8.4), Fixe Zen (8.1), Beal legend (8.3 cheap), Beal cobra (8.6 expensive). Any advice? ¿Going down to 8.0 is safe?

What about something like the Edelrid Starling Protect ropes (8.2mm) but has aramid incorporated into the sheath so has a much better cut resistance?

8.6 for me because it is a bit easier to hold a fall in thicker rope.  Better over edges too all other things being equal.

I've had a pair of the Beal Legends and they were a really cheap deal. However, they have handled and lasted really well. I would certainly get them again. 

Depends on grade a bit, I can manage a Moderate if not to hard, on a good day, so an extra kg isn't going to skew my grade   But if you are trying to send that alpine (f) 8c then a few grams may be significant.

The fact your asking, I'd go middle of the road. I've had a few ropes in my time but, personally.. I've loved Mammut. My last rope I got a cheap Beal (from Dick's climbing, they're great for ropes) and it's good but it doesn't handle like a Mammut. 

How sharp is the limestone? Bristol area it’s not too much of a problem but swanage I’d want 8.5.

Well I hope so, because my Edelrid Apus are 7.8mm!

It's a compromise, as it is with any type of rope.  Light, tough, cheap, dry-treated, nicely handling, not too stretchy... you can probably pick about three (perhaps four) out of six.  My Apus are very light, dry, and handle really well.  But they were reasonably expensive, and I'm very aware that they won't last terribly long if I abuse them; I have other sets of doubles for trashing with beginners.  

If longevity and cut resistance are important to you then head towards the thicker side of things and accept they won't be very light.  I've no experience of the aramid sheath mentioned: how well do they handle?

Ive had some 60m Cobras for years, not super light as a pair but I have used one as a single on low fall risk mountain routes.

not sure if all doubles are rated for use as a single  quite feature useful to have.

I don’t think safety is an issue, 8mm and 8.5mm ropes are very safe.
If your criteria is lightness and security as per your post then go for 8mm or even 7.9mm. 
I have Edilred Apus 7.9mm’s, great ropes that I would recommend.

There is a ofc a trade off in rope thickness for how resistant to cutting it is (all other factors being equal ofc). Swanage has quite a lot of flint / churt which is extremely sharp. There was an accident some years back iirc cutting a skinny half rope there.

its surprising how much more mass of fibre per meter there is in an 8.5 compared to 8 mm rope, taking Beal ice line 8.1mm and cobras 8.6mm, it’s about 19% more in the Beal cobra.

Thinner ropes tend to stretch more too which can be a consideration when considering hitting the ground / ledges etc.

I think the answer largely depends on the climbing you expect to do with them. You've said limestone, but is that single pitch or multi pitch? In addition to this, how much do you anticipate falling on them? Is durability a factor too, or is weight of the utmost importance? The other thing I'd say, which is a slightly separate point, is whether or not you need 60m. I'll go on to explain each of these in turn...

Single Pitch vs. Multi Pitch - if you're climbing single pitches, there is less need for a lighter rope, as you're not going to be carrying it up quite as far. If you're climbing multi-pitch then a decreased weight has an immediate benefit, as you're more likely to notice the cumulative effect. That said, a lighter rope is always going to be nicer to climb on, irrespective of whether it's single or multi-pitch; however, this leads me on to my next point...

Falling + Stretch - I stopped using 8mm ropes on rock a few years back, after a friend took what I deemed to be an unnecessarily massive fall on a super stretchy set of Beal Ice Lines. These ropes are brilliant for winter and alpine use, but on rock I'm not so sure - particularly if you anticipate falling. In this scenario I'm pretty sure my friend would have been fine if they'd been using a slightly thicker/less stretchy set of ropes, but as events transpired they went a long, long way and - as a result - proceeded to clip a ledge. As such, if you think you're going to fall a lot I'd genuinely consider getting something slightly thicker these days. Obviously the lower impact force is a benefit, but it comes at the risk of something such as this happening. 

Durability - whilst this is a slight over simplification, thicker ropes last longer, and having used everything from 8mm, 8.2mm, 8.3mm, 8.4mm and 8.5mm I can say - at least from anecdote and experience - that there's a massive difference between the first and the last in terms of how much use and abuse they can take.

60 vs. 50m - If you're climbing Scottish Winter, or happen to live somewhere with particularly long pitches, then 60s are great. If, like me, you find that 99.9% of your climbing isn't, then you'll just find yourself having to pull up an additional 10m of rope at each and every belay. What's the point in weight saving with an 8mm if that saving is eclipsed by an additional 20m of rope?!

In recent years I've moved from 8.5mm, partly because I think rope technology and construction has moved on, meaning that the modern 8.3mm and 8.2mm ropes feel like they offer the same sort of performance - maybe even better.

Whilst I haven't used any of the ropes you're suggesting, I am currently reviewing the Edelrid Starlings that Graeme mentioned (I'll try and get the review written up ASAP). Prior to that I used the Sterling Duettos, although they're no longer available in the UK, they were a great set of ropes!

it’s also easier to catch big falls using the sort of belay devices most people have on thicker ropes. Thinner ropes tend to slip through the device more, cause burns to hands etc. You certainly can get specialist belays devices that are really good for skinny ropes but they don't tend to work for thicker single ropes (can be a pain when abbing), you also can’t assume your partner will have one, so you need two of them.

Go try abbing on 8s and 8.6s then see how you feel! 8s need quite specific belay devices.

Surely there's no difference because each pitch of a multipitch is the same length (or often shorter) than a single pitch? Doing 5 single pitches one after the other is no different to doing a 5 pitch multipitch in terms of rope weight carried on lead (which is all that really matters).

You seem to be quite focussed on the only benefits being on lead, which is something I'd disagree with. Whilst this is indeed one benefit, there's more to climbing than leading - there's the approach (and the weight you're carrying) as well as the amount of rope you've got to haul up afterwards. So yes, whilst the weight of the rope you're carrying might remain the same, the other two factors are the ones that are arguably most important.

My mate burnt two massive holes in his hands exactly like this, it was a while ago but that was 8mm twins too.

I have used 7.5ish twin ropes in the past to reduce the weight on long pitches but as others have said they require smaller belay devices which is actually another weight saving. I favour 60m ropes because at swanage the routes are 30m which in the past were climbed in two pitches but can now be strung together. I hear the comments above about sharp chert cutting thin lines but really the routes at swanage are mostly overhanging. That said I now use thicker lines and that's really because the lighter belay device wasn't particularly easy to believe in. And any weight saving can be easily achieved by taking less gear (which I have tried and often failed to do).. 

One of the problems here is your natural instinct (possibly from neurones in your spine believe it or not) is to flinch your hands away when they get burned. Did your friend manage to keep hold of the ropes?

I take your point about overhanging routes at swanage. I’ve only climbed to E2 there. I found around E1 and below there was still plenty enough bulges for the rope to catch on, Certainly on many HVS’s which is what I mostly climbed.

Fair enough. And as I say these days I use a thicker rope. Perhaps in my younger days I was a bit more cavalier.

No-one has mentioned it so I will. How heavy are you? I'm a small skinny fella and I use ice lines for trad. I do fall off now and again and I'm happy with the stretch. If I was 14 stone I'd make a different call.

Back to Rob's point above - i've held a few falling seconds who were 'substancial' and they were unnerved by how far they went. You have to consider the others.

Light is generally right, in 1980 I saw Alex MacIntyre climbing on the Ben in winter with 2 X 7mm ropes. I never asked but I'd guess that he was under 10 stone.

Good luck with your choice...... Jeff

yes, but like I said it was before belay devices were specifically designed for smaller ropes.

I have an HB Marshal device made for smaller ropes (it won’t take 10mm ropes and above and is designed for half ropes). I bought that in the late 90’s. I think when I bought it it was already discontinued and I got it on sale. It has a solid metal loop instead of a wire one. Actually a really good device that has enough metal to be reassuring and works well on all half ropes I’ve tried down to 8mm.
 

This was pre the DMM bugette which must have come out around 20 years ago now.