What is the smallest wheel size that fits with this adapter? Philip Cowles March 30, 2018 17:05 Follow The smallest wheel size this adapter can accommodate is 20”. Related articles Which of your trainers does this adapter work on? Is the trainer skewer safe to use on the road? What is the difference between a Quick Release and a thru axle? Do you have shorter legs for the trainer so that it can accommodate a BMX bike? What is the recommended maintenance for my bike trainer? Comments 0 comments Please sign in to leave a comment.