Interesting Princess and the Pea issue
So I'm riding my road bike around, and it just feels weird. A tad Unstable, difficult to ride a consistent straight line. All of a sudden I'll just be over there. Like a big gust of wind moved me over.
I've had this feeling two times before. One time when I broke my frame. There was a hairline crack at the seatstay and seat tube. The other time was when I had a frame where the top tube was too long. The short stem I used didn't provide enough weight on the front to make it really stable.
I'd turned my bike over several times looking for cracks, nothing. I've loved this bike since I'd gotten it considering it the best frame road or mtn I've ever had. Why all of sudden would it feel weird.
The only thing I'd done recently was mess around with tires. The rear tire had been really squared off from riding on the trainer. I moved the front tire to the rear and put a new tire on the front. I was wondering if I just wasn't used to riding on a properly shaped tire after riding on the squared profile trainer tire.
But I think the issues was that I bought a different brand tire for the new one. One that had a slightly taller profile. The new tire was in front and it raised up the front, decreasing the weight on the front by a tad. To test this out I rotated the new tire to the rear and moved the rear tire to the front.
Bingo. felt back to normal.
I haven't measured anything, just going by feel. It still seems implausible that the small difference in tire height, if there is even one, would be enough for me to feel. But sure enough from one ride to the next the bike felt better.