Read this overview before going to the individual islands
The scenery in the Outer Hebrides is amongst the most beautiful in the world - the sea is very clear. On a sunny day when it covers the white sands of the west coast it has more colours of blue and green than you can imagine. The white colour of the sand is due to its high shell content (over 80%). The marine life includes dolphins, seals, sharks and whales. The Minch (between the Skye and the Outer Hebrides) is one of the best areas in Britain for whale watching. Seals are particularly common and will be seen sunning themselves all round the islands. Not surprisingly the Outer Hebrides are also famous for shellfish which thrive in the unpolluted waters.
The Outer Hebrides are also noteable for numerous lochs. Some of these are brackish and others are dark and acidic, water lillies are quite common and many have populations of trout and charr. Birds include dunlin, redshank, plover, lapwing and the islands are the last stronghold of the corncrake. Nearly every beach seems to have a population of sandpipers. The islands are formed on the oldest exposed rock in the world, Lewisian Gneiss. This is grey coloured with bands of white and dark minerals contorted by the pressure of the earth. These were formed over 3000 million years ago, similar rocks are found today in Canada to which this part of Scotland was once joined.
Harris Tweed is cloth that has been handwoven by the islanders of Lewis, Harris, Uist and Barra in their homes, using pure virgin wool that has been dyed and spun in the Outer Hebrides. This is the definition of Harris Tweed contained in the Harris Tweed Act of 1993 and it ensures that all cloth certified with the Harris Tweed Orb symbol complies with this definition and is genuine Harris Tweed, the world's only commercially produced handwoven tweed.
For centuries the islanders of Lewis, Harris, Uist and Barra have woven the cloth: Clo Mhor in the original Gaelic- 'The big cloth'. Nowadays of course it is exported all over the world. More of the cloth is in fact produced in Lewis but you can still see Harris tweed being woven in Harris on the west coast at Luskentyre.
Traditionally touring cyclists do the Outer Hebrides (Barra, South Uist, Benbecula, North Uist, Harris and Lewis) as a long chain of islands, taking perhaps a week to cycle the whole thing. This doesn't present any problem, and the scenery is at times so beautiful it defies description. Two major questions arise, which direction to do it in, and how to get there. The ferry journeys will be from from Oban to Castlebay (on Barra) and Lewis (on Stornoway) to Ullapool.
Which direction to cycle turns on wind direction. The prevailing wind is from the south-west though in summer there are sometimes northerly winds. The northerly winds are likely to be dry, but westerly winds might bring rain. Personally I prefer cycling cycling north. Traditionally the most reliable sunny weather is in the early summer though perhaps this pattern is now being broken. Certainly these islands do sometimes get long sunny spells when the rest of Britain is suffering rain. A possible problem is that the two mainland ferry terminals: Oban and Mallaig are 100 miles apart, so if you leave a vehicle at one of these places you have a 100 mile cycle on busy roads to return to it.
One solution would be to get the train. You can travel by train to Oban but the nearest train station to Ullapool is at Culrain 50 miles to the east. Cycling between Culrain (Carbisdale Youth Hostel) and Ullapool is fine, and the scenery is splendid. Most people could do it in a day.