Originally Posted by nevermore1701
one of the threads i saw was turning a mountain bike into a tourer.........thats my plan.
Normally people start with rigid frames for that. If you convert a bike with front end suspension, you run into several problems, that you will at least want to play with:
- Overall frame geometry. While MTBs can be good for a touring bike, and suspension can be good on a touring bike, an MTB hardtail is often quite different geometry wise than a touring optimal platform. You are far enough down the single track offroad trail, that it just isn't a road touring bike any more. If the frame you have is good for offroad, you may prefer to default it towards a road design, if you are planing to do road type touring.
- How is the frame outfitted for the use you now have in mid. Water bottle mounts, cable runs, brakes, stay lengths if you will be running panniers. etc...
- The whole front end thing.
1) Part one is to get an idea of what your ideal frame fit is. If you can get your hands on a road bike that you can test ride or borrow from a neighbour, your ought to be able to dial in your position so that you can come up with your numbers. Ideally on a 73, 73 head and seat tube angle frame. For me, when I get on a 58/58 frame it is a little short in the top tube length and a little high for best comfort in stand over, if the bike is at the high end of BB height. My ideal frame is 56/59, at 73,73. I like to have a 72 seat tube to accommodate my seat and seat post preferences, and I like a slack steering geometry, so I have to redraw to take those factors into consideration. But getting to some kind of starting point like this is easy with free online fit software, and measuring up a few rides. I think a lot of cyclists would do themselves a big favour if they spent some time trying to get their basic frame numbers.
2) So lets look at touring geometry in terms of five factors, as a starting point: Seat tube angle, reach, BB height, steering, and back wheel position. Of these the only ones that really mater a lot are the cockpit fit ones, the other 3 are relatively speaking, nice to haves.
Since you are going to be rebuilding your front end geometry you can experiment with the stance of the frame to see whether you can get close enough to your ideal geometry with the bike you have. Normally MTB geometry is slacker, and normally higher bb, so you may find that simply by tipping the frame forward you will be able to correct for those factors. What you are trying to do is get the cockpit right, and then find a rigid fork with the right crown height to secure these changes.
By angling the frame forward to correct the ST angle to about 73deg, you will also steepen the steering geometry, this will lower BB, and maximize top tube length. Now you want to take a snapshot and see where you are. Do you have the cockpit dimensions you need?
What is the steering geometry? It doesn't really mater as far as control is concerned, slack is fine on a touring bike, but slack shortens effective top tune length. You can also consider the rear wheel position, and whether it will accommodate your feet and bag, but a lot of people use work arounds, or just make do. There is bagpacking also. You can also measure the BB height and see where it is, but for the most part one can make do with that.
3) If you can find the right stance for the frame and work out the crown height, you will find there are quite a few available crown heights. If your original bike was a rigid, you will have a lot of choice. But you may find that you can only get the crown height you need at a compromise. Luckily there are options that will allow you to mount some front end rack on almost any fork.