i think i may be carrying too much stuff,when riding my road bike.

I can't resist a limerick about Wiltshire either

Racefaceec90's a man of Devizes
too heavy by far he surmises
he carries so much kit
his climbing is sh*t
but his descending could win him prizes

I see that the OP is located in a Wiltshire town loved by composers of limericks.

There was a young man of Devizes,
Whose rucksack held many surprises,
'Cos of the weight on his back
He was dropped by the pack
And finished outside of the prizes.

I'll get me coat.

Good advice above, but one thing I carry this time of year is a survival (space) blanket http://en.wikipedia.org/wiki/Space_blanket. It might seem a bit stupid but it takes up no space, is very light and has a miriad of uses. Most obviously to help keep you warm, (under your waterproof) but can also be given to others in need. It is one of those things that you hope you will never need but will be glad of it if you do!

I cant see the pic of what you take so sorry if its there, but things not mentioned are chain tool (maybe on multitool- but parktool mini one is likely to be better), and shimano joining pin (or sram link thingy.) In addition a tyre boot which can repair a damaged tyre is worth having. These things weigh next to nothing.

For rides of less than 2 hours I dont think you need food or drink especially when its not hot. I take a bottle of water on a 3 hour ride but dont feel the need for food. Longer rides your needs tend to go up quite quickly as you have used reserves up. If you are going hammer and tong then you might want something a bit sooner... but still not in 27 miles as its likely to be less than 1 and a half hours riding.

Finally (i am assuming from the question you are a relatively new to road stuff) the back pain may not be from the load but the position. If you still have issues after an unloaded ride dont be afraid slowly change things. On a ride make small changes one at a time. I tend to do saddle height 1st (too high can hurt your back if your hips rock) then saddle fore and aft. Get an idea of bar reach and height by changing where you grip the bar. Then try a few cheap stems.

I think you need to lose at least a third of it; like someone said you don't need that much liquid for 27 miles. The food looks like a weekly supermarket shop - you could just have a couple of bananas or energy bars in a back pocket. You don't even need those for that distance if you have some carbs in your drinks.

For longer distances you probably need to work out how much food & drink you need and whether you can stop and fill up anywhere. On a hot day you'd need 3-4 water bottles for 70-100 miles but in the winter you need less hydration and more energy drinks.

If you want to carry a lot without having it in a rucksack or pannier I'd take a jersey with back pockets, 2-3 bottle cages and a large saddle bag (the largest topeak aero wedge expands and has elastic straps to put a piece of clothing under it).

You can get little bags that strap on the top tube behind the stem as well but I find they rub on my legs when honking (i.e. exactly when you realy don't want something rubbing on your legs because you've run out of gears, feel like s**t and still can't see the top of the hill).

Instead of a D lock a small lightweight cable lock is probably okay for coffee shop / corner shop stops where the bike is only out of sight for a few minutes. What's the point of protecting your bike if you can't enjoy riding it?

Topeak pocket rocket is a good small pump which fits in a back pocket & comes with a bottle cage mount. I'd check user reviews before buying a lezyne mini.

If you've got mounts for a rack, a tortec velocity slimline rack won't slow you down much and you can strap waterproofs to it with a bungee if you're not taking a pannier. If you're not riding competitively and want to carry stuff then a pannier is a good way to get it off your back, although the bike will feel a bit more sluggish and you won't look cool. Bonus points when you overtake someone on a road bike with no luggage though (see http://www.itsnotarace.org)

For me, bottle on the bike. Usually water with a nuun tab chucked in.

Some id plus phone incl ride id app.

Lezyne mini pump, tyre lever, patches, mini tool incl chain splitter.

Snack of nutri grain bar and a few jelly babies.

bidons on bike, tube/patches/multitool in seatpack, pump and gilet in centre pocket. keys in another pocket and cafe money in the third.
If I'm planning on being out late, I'll stick the Joystick on my helmet. Flare is always on the seatpost.

My ideal bike is the Kona Ute. Nuff said I feel.

Me:

Bidons x2
Phone in sweat/waterproof cover
Pump, tube, patches and 2 L shaped hex keys in saddlepack
Snack
Garmin and Femtos

Tend to only take 1 bidon and no snack on rides less than 100km

It may be old school, but I stuff my pump down the back of my shorts.

On the odd occasions when I've needed to lock the bike I've carried a chain and padlock around my waist, I've seen a combined belt/lock advertised which is a more sophisticated version of this.

I carry;

Right Jersey Pocket

2 tubes (long ride) 1 Tube (short ride)

Center Jersey Pocket

Lezeyne Pouch containing - CO2 Cannister, Tyre Levers, Small Patch Kit, Multi Tool, Keys, Lose Change for Coffee

Lezyne Micro Drive Mini Pump

Left Jersey Pocket

Phone, Credit/Debit Card, Gel/Bar

On Bike

1 or 2 Bidons
Garmin
"Get me home lights" if I think its going to get dark before I am home.

For ~2 hours:
Seat pack with inner tube, tyre lever, multitool, Snickers/fruit bar, zipties, toe strap, cash.
Lezyne mini pump and 1 water bottle on the bike.
Jersey pocket holds a pertex windshirt (wore it too often this year! ) and, if I'm considering unfamiliar lanes, a page from a road atlas folded in a poly pocket.

At this time of year I fit lights if it may start to go dark before I'm home, as it did last week, otherwise the Electron Backupz.

I don't generally stop on rides other than at a village shop for a water refill on longer rides. On those I take a second bar, a puncture kit, chain tool and second inner tube.

That's a lot of stuff !!!
Me (and I carry a lot ! By road stds )

Two inner tubes, chain tool and magic links
Self adhesive patchs two steel tyre leavers
Mobile phone. Gels at 1 per 10 miles (never use them for rides less than 30 but they are there just in case) money and some times car keys. Small pump

1 or 2 bottles (750 or 1000 depending on weather / distance)

Rain jacket / cut down water proof trousers depend on forecast

All fits in a very small saddle bag and back pockets

If I think I am going to need a lock then I use my 2nd lock which wraps around the seat post

for complete pump overkill .... lezyne do a mini that'll
do Co2 AND manual
All my other gear goes into a single waterproof pouch that
fits a jersey pocket - job done

Assuming you've been eating normally in the days leading up to a ride, you probably have enough energy stored to manage an hour to 90 minutes without needing extra fuel on the ride. My Saturday club run is 26 miles and takes about 1 hour 15 minutes and I just take one bottle with water and then mobile and a fiver in jersey pocket, 1 gel just in case and then a saddlebag with CO2 cartridge and chuck, spare tube, patch kit tyre levers and then my house keys.

When I go on longer rides, I take a bigger saddle bag with all of the above plus an extra tube and a mini tool, add on a frame-fit mini pump and then 2 bottles with energy drink and more gels, bars and even spare drink powder in a zip lock bag in the jersey pocket.

If I know I may be out in the dark, the lights just go on the bike rather than being carried. If I'm going home to home, I try to dress appropriately and if it rains then just grin and bear it knowing I'll be home soon enough which avoids taking too many extra layers like waterproof trousers. If you must take a lock, look at ones for snowboards, they are small, pocket sized ones with a small retractable cable. Should be enough to deter the opportune thief if you are just inside having a cuppa and can generally see where the bike is.

Assuming you aren't too far from the beaten path, cash and a card can help in food emergencies so what you have been packing is really too much.

For a 27 mile ride at this time of the year, provided you're hydrated and fed before you start, you should need no more than one water bottle in a carrier. For hotter weather and longer distance (up to 50 miles) a second water bottle in a carrier. Anything longer, you are going to have to fill up en route.
Leyzne do great mini-pumps which fix to a bottle carrier and I use a co2 canister carrier which also fixes to the bottle carrier
I use a small saddlebag which holds two tubes, tyre levers, co2 head and multi-tool.
Your greatest weight is the lock. I think you will have to compromise in terms of risk. I use a very light and cheap combination wire lock which also goes in the saddle bag. Any serious thief could cut it in seconds, but it will deter the opportunist whilst you go inside and buy your coffee - then drink it with the bike in sight.
With regard food, a ride isn't a picnic, so plan to stop and buy food or Mars bars at places which suit the ride. All you should carry is a gel or energy bar in case of suddden energy loss.
If you do not plan to be out in the dark, don't carry proper lights. For emergencies at this time of the year (puncture at dusk) carry two small single bulb LED lights.
Take a measured risk on clothing - you can't cover all eventualities, but forecasts are pretty good these days. I've got a cheap weather station with an outdoor sensor so I know how cold or warm it is when I'm getting ready - it helps in not overdressing or underdressing
Please whatever you do DONT contemplate panniers unless you're camping with no chance of contact with the civilised world!

No worries, good luck with it!

I know the feeling though with gear creep. I do a lot of ski touring and if i take a bigger bag than absolutely necessary i end up taking the kitchen sink.

Force yourself to only take what you can carry in your pockets and be ruthless. Travel light and travel fast!

That looks like a huge amount of kit for 27 miles?

Firstly i just don't take a lock, simple enough if your out in a group but if you're out solo i'm lucky enough to have a bike friendly coffee shop handy. I tend not to ride where i'll get stuck in the dark but i just leave my lights clipped on.

Everything else fits in jersey with exception of water.

Pocket 1: Phone, credit card or tenner and key in sandwhich bag. Jacket stuffed on top.

Pocket 2: Minipump, tyre levers, tool and tube, with elastic band. Usually i stuff a wrap or two in there wrapped in parfoil, nice and easy to open on bike.

Pocket 3: Food, usually the Skratch labs rice cake stuff. Again wrapped in parfoil.

Are you carrying drinks in sports bottles or as they are? 2 bottles on frame will do most big rides but can always refill or buy a big bottle to refill mid ride. (Incidentally are you not absolutely buzzing with that much red bull stuff?).

Shouldn't really need anything more than that?

WOW, things will change for my on a trike, I can carry what I like and not feel it.

But upright, for 27 miles? A pump, spare tube, a bottle with something in it half full. Lights if its dark and my phone.

For 100 miles I would add some food, maybe a small lock, but nothing that chunky, thats an "all day" commuter lock in my eyes, not a pit stop one.

How much of the drink did you actually, um, drink? Unless it is really hot you're not going to need more than an 800ml bottle for a 27 mile ride (otherwise you're going to be stopping for a piss constantly).
Food: forego the variety. Gells taste/feel wrong, but mars bars or similar are easy to stash.
If you must carry a pump, make it a compact one (i have a superb one I picked up in Halfords- own brand "bike hut" but works beautifully) strapped to the frame; the hardcore would suggest anything other than a CO2 cannister is overkill.
Look at the weather forecast, dress appropriatly rather than carrying extra gear.
If you're riding from home to home, then unless you're going shopping on the way back do you need to carry the lock?
The ultra-hardcore Velominati rules frown on carrying anything more than a single bidon and only what will fit in the pockets of a jersey

if your going to take all that have you thought about some panniers.why dont you put your drinks into 2 bidons then they are on the bike in the bottle cages. everything else will just fit in your jersey pockets apart from the lock