These dresser bars are not going to do much for your bike or any bike at speeds of 30 to 40 mph as Pig9r said.
The dresser (Triumph does not call them crash bars) bars are mainly for if you forgot to put your kickstand down or got off of the bike wrong or for some reason your foot that was on the ground slipped on some oil and you were unable to keep the 900 lb beast from falling. The bars may get damaged but you should, for the most part, avoid damage (or at least major damage) to the bars, gas tank, etc... .
Good luck, I had the later model Triumph bars they were definitely thicker than the original ones that Triumph came out with.
Dennis
18 dtg KAF
23 dtg Dubai
24 dtg London
77 dtg Dubai
78 dtg Home (Thunderbird time and, hopefully, R3T ordering time)