Comparative form of stiff: more stiff More rigid, more inflexible, more unbending.(adjective)
Wiktionary.org : Text is available under the Creative Commons Attribution-ShareAlike License
Use "stiffer" in a sentence
"Whoever said that drug penalties need to be stiffer is a stupid shmuck."
"Some in the garages are nicknaming the stiffer tires, “restrictor tires”."
"This way, every year you can just add 15-20% more, like every year frames are getting 18-32% stiffer, which is why you should pay more, and your current bike sucks."