I’m a dark side virgin so would appreciate others opinions.
I’ve done some tests rides and worked out what I want, it’s a fairly unexciting Trek Domane, but very happy with the choice and sizing.
I’ve tried the carbon and alu frames, both felt good, but I’m sure the carbon felt very slightly smoother and quicker (maybe psychological).

I originally decided on the 2.0 because that’s bang on the money for cycle 2 work, however I’ve now discovered I can get 50% more cash on the scheme.

For pretty much the same cash I can get a:
carbon frame (with BB90 and E2 headset) + Tiagra groupset + Bonty wheels (look fairly basic)
OR
aluminium frame + (mostly) 105 groupset + Mavic Krysium Equipe S wheels.

It’s a straight choice between:
Domane 4.0

Frame: 400 Series OCLV Carbon, E2, BB90, DuoTrap compatible, IsoSpeed
Fork: Trek IsoSpeed carbon, E2
Wheels: Aluminium hubs w/Bontrager Approved aluminium rims
Tyres: Bontrager R1, 700x25c
Shifters: Shimano Tiagra STI, 10 speed
Front derailleur: Shimano Tiagra, braze-on
Rear derailleur: Shimano Tiagra
Crank: Shimano Tiagra, 50/34 (compact)
Cassette: Shimano Tiagra 12-30, 10 speed
Saddle: Bontrager Affinity 1, steel rails
Seatpost: Bontrager Race Lite, infinite tilt adjustment, 20mm offset
Handlebar: Bontrager Race Blade VR-C, 31.8mm
Stem: Bontrager Race Lite, 31.8mm, 7 degree
Headset: Integrated, cartridge bearings, sealed, aluminium, 1-1/8″ top, 1.5″ bottom
Brakeset: Aluminium dual-pivot brakes w/Shimano Tiagra STI levers

and Domane 2.3 with upgraded wheels:

Frame: 200 Series Alpha Aluminium, IsoSpeed, press-fit BB
Fork: Trek IsoSpeed carbon, SpeedTrap compatible
Wheels: Mavic Krysium Equipe S
Tyres: Bontrager R1, 700x25c
Shifters: Shimano 105 STI, 10 speed
Front derailleur: Shimano 105, 31.8mm clamp
Rear derailleur: Shimano 105
Crank: Shimano R565, 50/34 (compact)
Cassette: Shimano Tiagra 12-30, 10 speed
Saddle: Bontrager Affinity 1, steel rails
Seatpost: Bontrager Carbon, 20mm offset
Handlebar: Bontrager Race VR-C, 31.8mm
Stem: Bontrager Race Lite, 31.8mm, 7 degree
Headset: 1-1/8 integrated, semi-cartridge bearings
Brakeset: Shimano 105 brakes w/Shimano 105 STI levers

What do you reckon? Thanks in advance for any advice

A casual glance at the specs above suggest it’s a tough one to call. The 105 equipped bike is a better all-round spec, but the Tiagra equipped bike has a marginally better frame…

I think I’d go with the 105 bike, largely because by the time the kit is worn out you’ll be after another blingier bike anyway.

People may suggest that Trek is a bit bland, a bit Mondeo, but I’ve had one of the original OCLV carbon frames for over 10 years now and it’s rock solid. Trek also do a lifetime warranty on frame and forks.

Crikey! You’ve contradicted yourself. I’d spend more on the frame, but to be honest who gives a shit buy the one your heart tells you to get and ride it lots.

You’ve contradicted yourself

Nah, not really: I suspect that Alloy frame is better than my carbon one anyway!

Heart says carbon but I’m a bit scared of it.. always been a steel mountain bike type. What happens when I drop it, or lean a ladder on it?

Dont know but what i do know is my alu road bike seems to be made of coke cans so wouldnt be any stronger i dont think.

Nothing happens!

I’ve crashed my Trek a number of times, including seeing it bounce down the road like in a Bollywood car crash, and it’s been fine.

That disgraced laddie Armstrong rode a trek to a stage win with a broken chainstay…

(Luz Ardiden, 2003)

Is carbon worth the £500 extra though.. would rather buy right and not buy twice but it seems a lot extra

Difficult, like others have said generally spend on the frame, but the 105 plus better wheels makes that a great deal.

Being made of carbon does make it feel ‘special’ though, less industrial than these horrible mountain bikes. I think I would still go carbon and upgrade slowly as bits wear out.

You are at the same cusp of technology that I was when I bought my HID light – that line of technology had stopped developing and LEDs had overtaken HID in performance. Now carbon has overtaken aluminium in performance; admittedly manufacturers ike Trek and Cannondale are doing fantastic things with ali and hydroforming but carbon is the future and as a more versatile material it is allowing frame builders to build lateral stiffness with vertical compliance in a way that was never possible with ali. I recently jumped on a friend’s new carbon Orbea and was amazed at the directness of the drive and the acceleration and hill-climbing compared with my 2006 carbon Roubaix.

Ignore the spec, you will start upgrading and customising the bike soon with new wheels and bits and pieces; buy the best carbon frame you can afford and use that as the basis for the bike as it evolves in the next few years.

I’d get the better frame, as that’s the bit you’ll be keeping for the long term….

That Tiagra stuff is fine, perfectly functional; and you’ll be grateful to have a pair of wheels that won’t make you flinch every time you see a pothole. Which is a lot!! 😉

Carbon – the new tiagra is so good that there’s very limited benefit from having 105, especially once upgradeitis sets in. The bontrager wheels are apparently utterly bombproof so great as a set of winter wheels, and you’d probably want to upgrade wheels on the alu bike too as they’re not exactly light years ahead in terms of spec!

Buy right first time and save yourself from hankering after a new bike/frame in a few years.

+1 carbon

And buy a better set of wheels – and maybe STIs – later if you get the bug.

Eh? Both come with STIs.

Sexually Transmitted Infection snarf snarf gurgle gurgle

I think he means ‘better STIs’ 😉

I’d go with the carbon + Tiagra one myself, Tiagra is good enough now that you wouldn’t notice the difference over 105 and you can always upgrade to better stuff gradually once bits wear out or get crash-damaged. If it were carbon + 2300 or Sora I’d say stick with the alu frame but Tiagra’s a lot better.
The wheels aren’t much of a factor either really, both are pretty low end but both are perfectly fine for general riding. If you wanted to start racing or just to lighten up the bike you’d be replacing the wheels on either spec anyway.

Cheers all, useful advice. Carbon ordered 8)