The terrain i go for ride is hilly but have downhills too. is 10 miles trail. I park my truck i go for ride i do the 10 miles then i return in my truck 10 more miles that do total 20 miles. My average speed is was 12 miles. I ride road bike. My crank is 53/39 and my cassette is 9 speeds 12-25. gear ratio i have is 118.2 high low 41.7 The elevation in that trail is from 700 feet to 900 feet. I do the 20 miles but i had to walk 3 times. Sounds like i use the wrong gear ratio?