In reply to this post by Triumph Trophy mailing list
One of our members uses 190's on his '95. I think clearances are the same for the Mark 2's, but not positive. I think our wheels are 5.5" wide. That is fine for 180's and probably 190's. Worst case you'll get a bit of a triangular tread profile, but probably not enough to notice.
The thing to pay attention to is when you are in a hard corner at an extreme lean angle, you could maybe lose front tire performance and low-side whereas you wouldn't with the stock 170 or one size up 180. Might never happen, but best be cautious until you are confident that it won't happen. Have a look at the front and rear chicken strips on the stock setup. The wider the rear tire the bigger the difference will be.
I think if you are not a REALLY serious canyon carver you'll be fine.