Originally Posted by
Bill Kapaun
I hardly consider 7MM difference a "big" disparity! 27" rims tend to be pretty skinny anyway.
Well, a true 27x1 1/4 rim is not very skinny, and 7mm is 20% smaller than the tire width for which the rim is designed. Not only turns but impact protection will be compromised - as you indicated in reference to a smaller diameter with the 25mm tires. The 25mm tires have less height by design and when put on a wide rim they will sit even lower. I would recommend against going below 1 1/8 width, especially as many manufacturers push the lower limit of a given tire width so that their tires appear lighter than others of the "same" width. Check Sheldon's page on tire/rim width.