sustainable long distance and easily achievable mph averages

Question
Hello

I'm looking into cycling from the north of scotland to the end of england for charity.

I have worked out a few approximate average.
70 miles per day for twelve days
85 miles per day for ten days

so these mean long cycling days, now I a have only just started training and as of yet I don't have a gadget that allows me to calculate my averages over a ride.

I know that averages vary immensely from person to person but is:

7mph average easily attainable and sustainable over a long ten hour ride.

8.5 average over ten hours

and is there a possibility that the fatigue of doing this day in day out would make it harder to reach each day?

Answer
An average cruising speed of 10-12 mph is an easy pace. Cruising speed is what you would maintain over flat or gently rolling terrain. Obviously, hill climbing could slow that down to 6-8 and down hills could reach 20+. Then there are stops for traffic, meals, etc.

In my opinion, while 70 miles per day is reasonable for a cyclist in good shape who cycles regularly, it would take a while to build up to that level.

Not being familiar with the terrain, it is my impression that you would be starting with very hilly terrain ending with flatter terrain. So your early days might involve less mileage. On the other hand, you may find more miles per day in the middle as you come down from the highlands and get more downhills. A flatter terrain can actually be harder since there is less coasting and more constant peddling.

Another factor is your day. Depending on the season, you could have as few as 10 hours of daylight and as much as 14. You may also have to account for weather and down time due to it. head winds and tail winds can also affect your speed and effort.

Another factor is your support. Are you doing this on your own or will you have people traveling with you? Most importantly will you have to carry your own gear (clothes, tools, etc.)? If you do, that will also increase your effort and fatigue.

And yet another factor is your seat. You could have strong legs and wind, but sitting on a bicycle seat for 10 hours can get uncomfortable by the end of the day and multiple that by several days and hot baths will look very good at the end of each day.

Hope this helps,
Scott<>