I've just spend time learning about tubulars over the last several weeks. The advantages of a tubular seem to be very slightly faster over a comparable clincher.
The downsides are a lot more preparation work, and that a flat is very bad because they take a lot of effort to fix.
So if you've got a team car right with you, which is carrying spare wheels then that's great. But for the great mass of cyclists, the minor advantages of tubulars are outweighed by the massive downsides.
A clincher and a tubular use fundamentally different interfaces with the rim and therefore are built differently.
You can see the tubular is a tube that wraps a permanent inner tube. The clincher is a "bowl" that wraps 3/4 of an easily-swapped inner tube.
This is better explained in a picture:
Left is a normal clincher, middle is a normal tubular, and right is what I think you've done.
I suspect your tubular tyre has multiple layers of tubular tape trying to fill the void that is the clincher's wheel well or Valley.
You may have become confused between Rim tape and Tubular tape which are very different.
Additionally, Tubular glue is often spread in multiple layers with four on the rim and two more on the tubular. Tubular tape is used in a single layer.
Further downsides to this idea:
- Your tubular tyre is only making contact with the rim in two thin stripes. Its going to wear through the cotton pretty quickly.
- There is some "give" in each layer of adhesive tape, which will allow the tyre to move around the rim, eventually tearing where your valve stem meets the inner tube.
- This give will also allow the tubular tyre to squirm off the clincher rim, probably when you least expect it and likely while leaning/cornering.
In short, use the right rim for the tyre you have.