Went looking at carbon 29/27ers today but found a bargain 26er, same as my current bike but latest model at a bargain price and am very tempted. Would I notice a speed difference in a lightweight hardtail carbon 29er or 650b over a 26er?

Probably.

29 over 26? Yes in an XC way
650/27.5/26 and a bit over 26 – depends how much kool aid your drink

Why do you want a new bike? If it’s anything other than ‘it’ll be shiny’ then a current version of your existing model will likely have all the same attributes.

26″ carbon XC bikes are cheap because no one rides them anymore! If you’re happy then get yourself a bargain absolutely, but I’d be surprised if you didn’t notice a speed difference.

I rode a few 650b bikes yesterday and they felt exactly same as any 26’r I’d ridden ..

Why do you want a new bike? If it’s anything other than ‘it’ll be shiny’ then a current version of your existing model will likely have all the same attributes.

Pretty much thinking that I’ll be replacing a parts over the next year and spending some cash on servicing, so should I just bite the bullet and buy a new version of my current bike (that I am quite happy with) and sell my current bike on.. It could make economical sense, current bike is 9 speed XT, new bike would be 10 speed XT/SLX (Scott scale 620)
. I cant help thinking I should be going 27/29 though so seeking opinions from those who’ve made the jump from 26 to something bigger.

29ers = small difference maybe – whether this is ‘better’ or not depends on lots of variables. 27.5 = utter bullshit.

What fork is on the bargain bike, and how much is the bike?

This will probably tell you if it’s money well spent over replacing kit on your current bike.

Same level fork but newer, so most definitely an improvement with 5 years of technological improvements over the old one.

I’d not be so convinced by that. IMO a 2014 SID isn’t really an improvement on a 2009 one…

You seem to be talking yourself into it, personally I’d not buy a 26″ wheeled XC focused bike now. If nothing else companies aren’t doing forks/wheels/tyres in 26″ so much these days. Any performance differences aside.

If nothing else companies aren’t doing forks/wheels/tyres in 26″ so much these days.

Any evidence for that ?

I can’t think of any forks, wheels or tyres that aren’t available in 26″. People keep saying that they will be harder to find, but I can’t see any evidence.

The RS1 fork, Roval wheels, Tune’s latest XC wheels, American Classic no longer do any new 26″ wheels.

The hookless LB rims are only 650b/29″.

And so on.

It’s more prevalent in lightweight XC stuff, of course you’ll always be able to buy bits, but I can’t see companies focusing their innovation on 26″ for that sort of equipment.

Of course, there are some wheels/forks/tyres not available in 29″ or 650b either… it’s inevitable that with multiple wheel sizes not all products will be available for all wheel sizes. Long term it’ll be more of an issue with 26″ perhaps, but I’m not sure I’d worry about it with any wheel size really. Time to except that market fragmentation means that only some products will fit your bike in future, not all. That’s not the same as saying that you won’t be able to get wheels/forks/tyres for your bike… just that not all wheels/forks/tyres will be available for your bike.

Forks aren’t really an issue anyway… if that lovely but bank balance busting RS1 is ever made in a form that fits 650b bikes, then it’ll fit 26″ wheel bikes fine.

If nothing else companies aren’t doing forks/wheels/tyres in 26″ so much these days.

The thing that’d really put me off a frame is a 1?” straight headtube, regardless of wheel size, because I don’t think midrange and above straight steerer forks will be available for much longer. I reckon this’ll be a bigger issue than 26″ wheels.

Of course, there are some wheels/forks/tyres not available in 29″ or 650b either.

Well obviously, but I’m not aware of any company that have released a product aimed at the XC market in 26″ only, and plenty of manufacturers are either dropping 26″ products from their range (a la Roval and AMC), or just not releasing products in 26″.

Roval? Any component brand owned by a bike manufacturer, and primarily run to supply OEM to said manufacturer, will probably only make wheels that fit in with the bikes that manufacturer is aiming to sell. Roval top end race wheels will be 29″ only while Specialized top end race bikes are 29″ only.

Depends if it’s enduro specific, and if you’ve got a 650b specific saddle, and 650b specific shorts, only then will the trails come alive.