Curious if anyone has any experience of running a longer-than-recommended fork – does it really make you a bad person like the manufacturer says? Im keen to try a Fox 36 Talas 160mm fork out on my Iron Horse Mk111 to see how it changes it when cranked up to max travel for the downhill riding , but as its rated as only up to 140mm fork max, will it mean the bike will implode if I do this, or I will be hunted down and shot by iron Horses?

might ride a bit weirdly, 'drop' into corners at slow speed, and lack a bit of front end grip due to your weight being shifted backwards by the higher front end. You could as snap the headtube off due to over loading it with stiffer and longer front forks than the bikes designed for BUT this is unlikely, maybe, allegedly.
Wouldn't do it myself, if you have stiffness problems on yer front end (sorry) maybe try a bolt thru fork like a vanilla rl 140?

do it! longer stroke forks on xc bikes makes them handle big stuff WAY better in my eyes, increasing confidence in the harder bits, without slowing you down on the flat.

slacken them angles, you know you want to!

I stuck some 125mm Psylo's on a 63mm designed Zaskar once. It was bloody awful.
Looked a bit like this…

Having slack angles is one thing, but if a bike is not designed to have such slack angles you can lose front wheel (i.e. cornering) traction.

Do you find the bike unstable as-is?

You know how we look back at those massive 130-150mm stems from back in the day and laugh? That's how we'll look back at the current obsession with "slack". What's wrong with a bike that steers?

I put 160mm forks (36 Vans) on my Pitch replacing the 140mm Pikes – the frame is rated for up to 160mm forks though.

Definitely more wandery on the climbs but I didn't notice much difference in cornering. They feel awesome going DH on steep rocky straightish stuff, not so good on slow, tight twisty stuff.

I've ended up putting a slightly longer stem on though and am thinking about trying some low rise bars.

Before you mess your bike up I'd ask yourself exactly what proportion of your riding would benefit from the change. Very steep and fast/hairy – a typical ride for me would have just one or two little bits like that. Through the singletrack and twisty twisty – loads more of that, maybe fifty times more. Climbing – loads of that too.

From my own experience you will likely prefer it on the one per cent of your ride that will benefit, and kind of tell yourself that it doesn't make much difference for the other 99 per cent of the time. Until about a year later when you'll eventually admit that the bike designer might have known what they were doing after all.

What fork does you mkIII trail current have?
If a QR 140mm Fox 32 then you'll be lengthening your fork by about 34mm

apart from risking ripping the not strong enough head tube off, its not really the 1.5ish degree slacker head angle that'll be the problem. Its slackeningin everything else off so much more too. A longer travel bike designed for the 160mm bike might have a slacker head angle, but the rest of the bike is designed to handle around it
A slacker seat tube will force you're seated weight further over the rear wheel, and as you'll use your saddle as a sort of reference point for your thighs/kness when stood descending, you'll naturally be positioned further back, more so if you stick a shorter stem on to try and speed the steering up a little. If you shift the saddle forward to compensate then you're shortening the shortened (from propping the front end up) effective top tube length further

Your bottom bracket height will suffer badly too, raising your centre of gravity ablve the bike lots, reducing the bikes handling abilities in corners. You could run lots more sag to emulate the BB height eith the 140mm fork, but you'll be bottoming the shock out more easily (the lower pressure and having more wieght distributuon on the rear wheel from the propped up front end) on a bike with a much more capable fork up front
To keep up with the capability of the 160mm fork, you'll probably want to put some fatter tyres on the bike too, lifting the bottom bracket height further.

The effective chainstay length will be shortened, putting your weight nearer to the rear axle (made worse by the slacker seat angle, perhaps more sagged shock) making it harder to get a decent weight distribution to go uphill

The horizontal distance between bottom brakcet centre and handlebar position (is that front centre?) will be shorter which makes pedalling harder, even with a decent effective top tube length, it'll feel wierd having the pedals so far forward in relation to saddle position

If the bike was designed to be able to run a bigger fork, then chances are they'll have designed around it to some extent, if not then probably not. Depends on the bike design, the bikes frame size, (and riding) as to how well it will work

I'm running a 160mm Lyrik on a 2007 Reign 1.

Bloody great, no chopper feeling at all even with high risers and only use the u-turn for really steep stuff.

It's not as if you're putting a Fox36 on a weedy xc bike so I say go for it.

Here's mine….

You could always run a bit more sag

And someone else's, though the Lyriks look a bit wound down

i run 150mm talas on my 2004 enduro and it`s brill 8)

I run overlength forks on an XC bike they are pikes with U turn so I get to try it out at different lengths – when its right maxed out it is chopper like and the weight is too far back – but that is great for downhills. with it wound down a bit but too long for the frame still it rides very well – but this was a twitchy XC frame

A fork 34 mm longer will not ride 34 mm higher as you get more sag as well.

As for ripping the head tube off – you are reducing your safety margin but not by a huge %.

Thanks for all the responses – well useful, particularly the effects on the geometry and riding James. Cheers all.
FOr those who asked Ive currently got 140mm U-turn Revelations Maxle-lites on the Mk111 and tend to run it mostly at 130-140mm except when climbing really steep stuff. It rides great – just thought that with a Talas 36 on it I could increase options a bit more when giving a bit of DH riding a go this year without having to buy a new bike!
Fair enough there will be some risks, and the riding might be a bit odd, but i think I am going to give it a go: with an adjustable Talas I could run 130mm for normal trail riding (most of time) with 100mm for steep climbing, and also have ability to increase travel to 160mm and slacken head angle etc when trying certain challenging steeper stuff. Not gonna be considering running the full 160mm all the time as appreciate it would mess with the angles etc, but still think it may be worth a go on this frame and probably wont be a massive price to pay (until the headtube snaps off eh? 🙂

I have stuck some Fox 36s on my Cove Stiffee. They don't work cos the frame is designed for 130mm and they are 160mm. If I stand right over the front of the bike and compress then the forks work. If I stand back where my weight would be when riding they don't work (almost feel locked out) as the angle isn't correct.

I already owned the forks so it didn't matter for me but I'm glad I didn't buy them specially! If you own the forks already, try it out and see how it feels!

Milkherd – I also have a Cove Stiffee (a 2007 frame). I thought they were designed to take up to 160mm fork quite comfortably? I was thinking then that maybe the 36 Talas might be good for beefing up this bike for heavier duty riding possibilities too? If it handles like you say then maybe not!! Can you not just adjust the air pressures down a bit to get them to be more active with your weight in normal riding position?

Mine is a 2005 frame which I think (or am presuming) was less travel at the front. The forks are Van 36s so non-adjustable. You might be fine with your frame and fork combo though.

I was just warning not to assume that sticking a longer travel fork on the front will only affect the slackness of the bike – it might also mean the forks don't work at all!

I've got a 2010 Cove Stiffee frame that i am just about to fit a set of 2010 TALAS 36's to, hopefully it can handle it!