I'm having a real fit trying to locate tubes of any brand to fit the new Bridgestone Spitfire S11s I have for the R65. The tire sizes are 100/90-18, and 110/90-18, which are fairly standard and readily available. However, the closest size to these I can find anywhere for an 18" wheel, is a 110/100-18. I've looked at all of the major online shops, and while the tires can be had all day everywhere, no tubes. I'm beginning to wonder if a 100/90 or 110/90 tube has been made!
May I run the 110/100-18 tubes in either of the /90 aspect front or rear tires? If so, should I use a lower air pressure? What might be the negatives if I did so? I'm concerned about how handling could be affected, or excessive heat buildup, leading to a flat or shorter tire life. Help!