My work commute is approximately 22km each way (sometimes I take the 'scenic route' around the lake which adds another 1-2 miles to my trip). Used to wear work pants on my rides into work until I had a wardrobe snafu during the middle of the day. Thank God I had a pair of shorts that day (which I was planning to wear on the ride home) and that worked out but ever since, I have been wearing cycling tights (pants/shorts) with chamois to/from work and carrying work clothes with me. I also keep an old backup pair of pants at my desk just in case. It gets heavy at times but I'm used to it.