April 25, 200719 yr i have a ty175 and i am considering modifying the fork caps to air valves. has anyone had any experience of this? specifically, what valves to use? how to fit ? pressure in the fork? is it a benifit? any advice will be greatly appreciated. paul.
April 26, 200719 yr Yes I used air caps on my TY175 for a few years in the 1970s both with and without steel springs. You already are using air pressure as a spring in standard TY175 forks but with zero preload (atmospheric pressure). You can vary the overall spring rate to prevent bottoming by increasing your oil quantity if that is what you want. Careful measurement of oil height is required though to ensure the forks are getting full travel. Yes air caps "work" because: You can fiddle to your hearts content with spring rate and preload by varying oil quantity and gas pressure. However air caps are not used much in real life because: The gas heats up and cools down depending on ambient temperature and bike use and so changes your carefully adjusted pressures. The gas volume in TY175 forks is so small it is very hard to get the pressure where you want it. The increased pressure causes increased drag on the fork seals. This is not good for suspension action on a trials bike. For the same reason the fork seals wear out faster.
April 26, 200719 yr Not only will it be hard to set pressure, but difficult to get both the same. I too would recomend using oil level to make the fork progressively stiffer. If you insist on using air, go to a bicycle shop and buy a pump mountain bike shocks, it will make it easier to set pressure. Also if you could link both sides together it would help.
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