Right so I finally got myself a 29er last year and I’m having no luck getting it setup properly (it’s a Scandal). I stuck all the contact points in what felt like the right places, slightly longer/lower position than normal for an MTB (but not as low as my road/cx bikes) it had rigid forks and it felt great for the first hour or so but unfailingly after 15-20 miles my forearms started hurting, lots. If I take my hands off the bars and “roll” my wrists I get little shooting pains up the underside of my forearms after another few miles I’ll be getting stronger shooting pains from every bump.

Since then I’ve added 80mm suspension forks (shorter than I use on my 26ers but pretty sure that’s not the issue anyway, I ride lots of miles on my cx without this trouble) tried a few other bars I’ve had no problems with in the past. Raised the bars, lowered them, longer stem shorter stem, tilting the saddle back/forward even moved my saddle further forward than I like with a short stem to really shorten the reach. No (or very little) difference, I still can’t ride it over 20miles comfortably.

I’ve ridden lots of bikes in the past, some with pretty dubious riding positions, not had this problem before except maybe riding long rocky rides on a rigid SS, when my arms were completely shot the downhills would be uncomfy on my arms, still a different sort of pain to this tho.
Any ideas what should I be looking at?

Looks like you’ve tried quite a lot of changes, so only a few things spring to mind:

Try some bars that are designed to tame trail ‘buzz’ a bit – like these from Deity: http://www.bikeradar.com/mtb/gear/category/components/handlebars/handlebars-mountain/product/review-deity-dc31-mohawk-carbon-handlebar-14-48852/

OR (and this may sound weird) have a look at brake lever position. If you ride with your levers covered with one finger pretty much all the time (I know I do) then if your new brake levers are too high or low (or the lever is out too far) that may cause your problem.

OR do you find yourself gripping the bars hard on this bike? That could be because it’s a bit of a handful or because you don’t yet feel ‘dialled’ on it. Try making a conscious effort to relax your grip as you ride…

Grip thickness? I had similar forearm discomfort with thinner grips (RF Half Nelson), largely solved when I stuck some Lizard Skins Northshore on.

Are the grips different to ones you’ve used before?

I built up a winter bike in December, and by the end of Jan I was getting some pain in one of my hands – swapped the grips to match the softer, fatter ones on my other bikes and the problem went away.

cheers for the suggestions, will look at the brake levers thing, think I just set those up as usual (angled quite far down) I will try ’em flat.

Not sure about the trail buzz thing, like I said I ride rigid cx a lot and don’t have this trouble. Thinking about it I’ve got a carbon bar on the shelf, none-OS too, will give that a go in an effort to introduce a bit more give.

I try to keep my hands relaxed, don’t really have deathgrip, like I said bike feels fine and quite comfy for the first 10 miles or so.

<edit> Forgot to mention in the OP: using my usual grips, yeti lockons, been using the same style for years so that shouldn’t be a factor. Have been meaning to try something a bit squishier not got round to it yet. I’m wondering if it’s a combination of factors, not one thing, certainly proving tricky to nail down.

I can lend you some ergo grips to see if that makes any difference???

cheers junkyard, might take you up on that offer.

I will bring them out next week.

Another vote for brake-lever position. I experienced similar with them angled slightly too far upwards, but I’d imagine it has a similar effect the other way too. Difference was pretty noticable in how relaxed my wrists/forearms immediately felt.

hoping the brake thing will solve it, if not then carbon bars squidgy/ergo grips and if that doesn’t solve it….I dunno.

Ride no-handed? Unicycle?