We_are_Stevo
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...but then again, Chas Roberts says it's perfectly okay to fit a 100mm travel fork to one of his frames; and he designed and built them so... 
rigid fork length question
- Thread starter gsy971
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found this one and its in stock
http://www.carboncycles.cc/?s=0&t=2&c=43&p=1059&
http://www.carboncycles.cc/?s=0&t=2&c=43&p=1059&
I have a frame meant, I think, for 390mm axle to crown forks. I fitted some 410mm forks, thinking this was a small enough difference not to matter.
The slight decrease in head angle should increase the trail, which should give slightly slower steering. However, this was not my experience, the steering is a bit jittery, especially at low speed. Having had read up on the subject, I think the reason is "wheel flop", where the wheel/bicyle has a tendancy to fall into a corner, especially at slow speeds: http://en.wikipedia.org/wiki/Bicycle_and_motorcycle_geometry
I'm now looking for some 390mm forks. :?
Is there a way that you could fix/lock your existing suspension forks to see if it feels right, before you buy?
The slight decrease in head angle should increase the trail, which should give slightly slower steering. However, this was not my experience, the steering is a bit jittery, especially at low speed. Having had read up on the subject, I think the reason is "wheel flop", where the wheel/bicyle has a tendancy to fall into a corner, especially at slow speeds: http://en.wikipedia.org/wiki/Bicycle_and_motorcycle_geometry
I'm now looking for some 390mm forks. :?
Is there a way that you could fix/lock your existing suspension forks to see if it feels right, before you buy?
We_are_Stevo
Old School Grand Master
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Some commonsense from Sheldon Brown...
...and this based on competition roadbike stat's where 'bike fit' can be crucial; on a mountain bike you can make significant changes in geometry and you just will not notice any difference.
There's a nice quote in the fork deflection test link...
Will you notice a difference?
Some riders seem not to notice anything about their bikes. Other riders notice everything. Some riders even notice differences that don't exist! Truthfully, the differences between forks are pretty small. Nice light wheels make a much more noticeable difference. Padded handlebar tape or slightly more or less air pressure make about as noticeable a difference as a new fork, in my experience. But many riders rave about the improved sprinting a stiff fork gives them, or the new found confidence on fast downhills. Others love the comfort they can finally enjoy on longer rides after installing a more flexible fork. The bottom line is you might notice a difference.
...which says it all
...and this based on competition roadbike stat's where 'bike fit' can be crucial; on a mountain bike you can make significant changes in geometry and you just will not notice any difference.
There's a nice quote in the fork deflection test link...
Will you notice a difference?
Some riders seem not to notice anything about their bikes. Other riders notice everything. Some riders even notice differences that don't exist! Truthfully, the differences between forks are pretty small. Nice light wheels make a much more noticeable difference. Padded handlebar tape or slightly more or less air pressure make about as noticeable a difference as a new fork, in my experience. But many riders rave about the improved sprinting a stiff fork gives them, or the new found confidence on fast downhills. Others love the comfort they can finally enjoy on longer rides after installing a more flexible fork. The bottom line is you might notice a difference.
...which says it all
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Not only does it not say it all, it doesn't say anything whatever about head angle.We_are_Stevo":2pvmt2ah said:Some commonsense from Sheldon Brown...
...and this based on competition roadbike stat's where 'bike fit' can be crucial; on a mountain bike you can make significant changes in geometry and you just will not notice any difference.
There's a nice quote in the fork deflection test link...
Will you notice a difference?
Some riders seem not to notice anything about their bikes. Other riders notice everything. Some riders even notice differences that don't exist! Truthfully, the differences between forks are pretty small. Nice light wheels make a much more noticeable difference. Padded handlebar tape or slightly more or less air pressure make about as noticeable a difference as a new fork, in my experience. But many riders rave about the improved sprinting a stiff fork gives them, or the new found confidence on fast downhills. Others love the comfort they can finally enjoy on longer rides after installing a more flexible fork. The bottom line is you might notice a difference.
...which says it all
The head angle of a rigid bike is important, and a two degree variance will certainly make a noticeable difference to anybody with any sensitivity. No bike designer would ever design a rigid mtb with a head angle of 69 degrees, not even if he was using a short stem, so it wouldn't be sensible to do it to this bike.
We_are_Stevo
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'Is the Change Significant?
To put the change in head angle in perspective, here are some changes besides swapping forks that also change the head angle:
Variations among headset lower stack heights (from 11 to 15 mm: 0.25 degrees)
Maybe frame building tolerances (quality frames up to +/-0.3 degrees from nominal)
Running different tire widths front and rear (one 28 mm and one 20 mm tire: 0.48 degrees)
Same model frame, but next size larger or smaller (typically 0.5 to 1 degree)
Choosing a different model frame (as much as 10 degrees)
Take a look at a few manufacturer's frame geometries (they usually list geometries in their brochures). You can easily find head angles that vary from 72 to 74 degrees, and if you hunt a little among different maker's brochures you will find frames whose head angles differ by several degrees farther in both directions beyond those numbers. For example, a friend who is quite a good bike handler likes to pursuit on frames with 78 degree head angles, but he will just as happily pursuit on his bike with a 72 degree head angle! And in the other extreme, for many years bikes had head angles in the low seventies and high 60's. That's a total range of almost ten degrees. In comparison, the biggest change you can get by switching forks is just over half a degree. That's not much.'
To put the change in head angle in perspective, here are some changes besides swapping forks that also change the head angle:
Variations among headset lower stack heights (from 11 to 15 mm: 0.25 degrees)
Maybe frame building tolerances (quality frames up to +/-0.3 degrees from nominal)
Running different tire widths front and rear (one 28 mm and one 20 mm tire: 0.48 degrees)
Same model frame, but next size larger or smaller (typically 0.5 to 1 degree)
Choosing a different model frame (as much as 10 degrees)
Take a look at a few manufacturer's frame geometries (they usually list geometries in their brochures). You can easily find head angles that vary from 72 to 74 degrees, and if you hunt a little among different maker's brochures you will find frames whose head angles differ by several degrees farther in both directions beyond those numbers. For example, a friend who is quite a good bike handler likes to pursuit on frames with 78 degree head angles, but he will just as happily pursuit on his bike with a 72 degree head angle! And in the other extreme, for many years bikes had head angles in the low seventies and high 60's. That's a total range of almost ten degrees. In comparison, the biggest change you can get by switching forks is just over half a degree. That's not much.'
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