I have a 22L drybag to for my winter bag to go in my bar harness. Bought it 2 years ago in a bit of a pinch, the best one I could get my hands on was a super heavyweight Ortleib one. If I get something lighter, I could "buy" myself quite a lot of whisky with the weight savings.

Current Ortleib is 355g - ?D
Alpkit Airlock Extra is 190g - 320D
Alpkit Airlock is 52g - 30D
I couldn't see what D the Wildcat double ender is for comparison.

First thoughts were that the a bar bag is protected in most falls from the bike by the bars touching down first, and the tongue of the wildcat harness would protect from rocks thrown up by the wheel.

But then it is a down bag, and it would be dispiriting to get it wet if something were to happen.

Any thoughts, experiences?

Edit: just remembered the real reason I started looking was for some width compression: there's a 70D exped job with side straps and an outlet valve at 102g. I think tht's the favourite unless its inadvisably skimpy.

Although I guess anything can be compressed with a couple of extra straps?

I've a Wildcat double ended bag. The material looks to be the same as that used in Exped dry bags, I think it's around 160g in weight.

I've not had any problems carrying my down kit on the front. As you say the tongue of the Lion harness protects from stones and if you do crash then the wheel and handlebars would take most of the impacts. I often take a bivy bag and use that as an extra "liner" so there's more protection. Not going to protect against a sharp object puncture but then nothing "soft" is likely to so not a great deal you can do about that.

Cheers Whitesone, edited mine before I saw yours. Good point about the punctures, ta.

Don't forget that dry bags are different shapes for a given capacity. Some fit certain set-ups better than others ... for an example Lomo bags are longer / thinner than Alpkit bags.

Cheers Norm, I'd got into that aspect already, not helped that some companies quote flat and some full, bit of 2πr required.

Forgot about Lomo, though, thanks for that, off to check them now.

By compressing the "width" do you mean the circumference of the bag? I've found that so long as you have roughly the right size dry bag then pushing down on the end of the bag and wrapping the closure as much as possible gets the contents reasonably tight. You can then use the straps on the Lion harness to snug things down. The main thing to watch out for is that the bag is long enough for the straps of the harness to be able to grip it. Ultimately this means that there's a minimum usable volume for bags you use with the Lion.

As Stu says, different bags are different shapes. The Exped ones for instance all have roughly the same length to circumference ratio so once you get to the bigger sizes then the circumference is too big for the harness! I've a Revelate SaltyRoll which is much longer than the Exped bags for when I get to this scenario.

They're in the same ballpark, actually:

Airlok Extra 20l is 32cm flat width,
Airlok lighter weight is 37cm. f.w.
Lomo 20l is 35cm f.w.

Lomo is a good bit cheaper though - half the price of the cheapest alpkit ones. and they have a little window so you can wave at your sleeping bag.

I did mean circumference, yes. As soon as I read yours, I realised most of the time you're looking at a bar bag, "width" is the length.

Last time I used the 22L ortleib on the hardtail, I had the front wheel scuffing the harness when the forks compressed.

Wildcat suggest 8L and 13L fit fine in the harness, I've had 13L in with no worries at all (summer bag, hammock and mat)

The 22L Ortleib just fits in my 46cm drops (it's rolled down quite a bit, and the thick fabric rolled up takes a bit of space) , so with all that considered, a slimmer, longer 20L bag would be perfect for non-drop bars.

I use one of the exped ones with 3 compression straps and the vent, I use the compression straps to hold it to the bars which buys you another 400g+ of whisky usually I have a revelate pocket which acts as a backup to the straps otherwise a pair of double sided Velcro straps for additional security

Cheers Steve, That's the one I've gone for. Hadn't planned to ditch the harness, but I'll have a play when I get it. I'm thinking I'll still be keen to keep the worst of two days of mud spray off the drybag, so I imagine I'll stick with it.

Other thought is that I'll be strapping to truss forks this time round, which can only mean a bit more stability for the bag.