I currently have a 120mm RST fork on my hard tail MTB, its showing a lot of signs of wear on the stanchions, new 120mm are quite pricey, my question is, can i replace them with 100mm forks? or will my bike be set to have 120mm? it came with 120mm from new.
thanks
The front of your bike will be 20mm lower.
That change in geometry may affect how it rides in a good or bad way.
You will have to tell us what frame it is, how you ride and what sort of riding you want to do. Even then, its likely to be a matter of how you feel not what others say.
Id notice 20mm either way - you may not. Personally Id stick to the same length, but buy some good forks.
You can fit 100's but they will steepen the head angle (quicker steering) and obviously lower the front end too. If you've got a set lying around or can borrow a set , fit them and have a go , to make sure you're happy with the angles before buying. It would be less good down hills 🙂