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I have an On One Summer Season. I am considering moving to the 456ti or 456 carbon. I really enjoy the slack ht angle of the simmer season, although I run it with a 130mm fork. Both 456's can handle up to a 150mm fork.

Question is if I put a 150mm for an a bike with a HT angle of 67.5 (measured with a 140mm fork) will the actual HT angle be similar to my current set up (stats say 66.6 measured with a 140mm fork) since I am only running a 130mm?

Is there a formula for how much HT angle changes per 10mm of fork increase or something like that?

Thanks,
John
 

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Just keep on thing in mind John. You may or may not be increasing your fork length by only 10 or 20mm by putting a 10 or 20mm longer travel fork on the bike. This is assuming that you are changing forks. Not all forks are created equal. The best measurement to use in comparing fork lengths is axle to crown height. I've seen AC heights vary between different manufacturers as much as 20mm for the same travel fork. I had an older 80mm Manitou fork that I replaced with the 100mm Marzochi. The crown on the Zocch was beefier (taller) and resulted in an additional 19mm of fork length. Total AC height difference between the two forks was 39mm, not just the 20mm that comparing only the travel would suggest.

If you are using an adjustable travel fork of the same model, then yeah you'd be spot on, 20mm more travel would equal 20mm more fork length. But using a fork from a different manufacturer or even a different model from the same manufacturer may yield slightly different results than what you are expecting.

Just something to be aware of.

Good Dirt
 

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Besides changing the head angle, a taller fork will also raise the bottom bracket and change the seat tube angle. You may or may not like the feel anymore when the bike is taller
 
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