A new Litespeed titanium goody has arrived...of the Monster Cross variety

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RyanH
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by RyanH

It looks like I'm searching for a unicorn fork. The resulting trail for most forks that I can find will probably be in the high 70s, if not 80s. For the geo experts out there, is that too much trail for a gravel bike?
Strava
Current Stable. The Snob Machine
The Ex's. LS Siena: 6.21kg | Parlee Z5 SLi: 5.9kg | LS Xicon: 5.76kg | C59: 5.7kg | Cervelo R5ca: 5.09kg | Fuji Altamira SE - 6.2kg | Scott Foil - 6.2kg | Evo - 5.18kg | LS Classic - 6.7kg | The Crumpton - 5.9kg

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dwaharvey
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by dwaharvey

How are you getting that number? It looks like Litespeed claim a 69.5 HTA but their table doesn't include a fork axle-to-crown at which that is measured (and their claimed rake of 1.5cm is obviously wrong). They do say they suggest an 80-100mm fork, which if one were to use a FOX would give AC of 468-488mm. Not clear if the 69.5 is with fork sagged either. And their "BB drop" of 12.5cm is obviously messed up too... maybe 12.5" BB height, but not clear what size wheels that is with, if that's what it is at all!.

For comparison, Enve cross fork is 395 axle to crown, 47mm rake. Enve mountain fork is 470 axle to crown adjustable rake from 44 to 52mm. Wheel size between 27.5x2 and 700c x 35-40mm is damn close of course.

I suspect a cross fork is just too short to work right, lower BB and make HTA too steep. Finding a rigid MTB fork with the AC you want seems the best bet...?

by Weenie


RyanH
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by RyanH

They spec a rockshox sid rct3 27.5 which has an axle to crown of 487mm (IIRC). That seems about right because when I mocked up the Enve fork with its 470mm AtoC, HTA was slightly steeper than that. I'm hitting a wall on trying to find a fork with the right AtoC but not a wonky offset. 26" forks have 38mm rakes it seems. Cross forks are too low and HTA would steepen significantly.

I suppose the question is, will 80mm of trail equal a poor handling bike?

Update: Cx fork *may* work. I'll pull the Caadx fork off and measure the HTA but I think it should be 74* or less which should put trail around the mid 50s.
Strava
Current Stable. The Snob Machine
The Ex's. LS Siena: 6.21kg | Parlee Z5 SLi: 5.9kg | LS Xicon: 5.76kg | C59: 5.7kg | Cervelo R5ca: 5.09kg | Fuji Altamira SE - 6.2kg | Scott Foil - 6.2kg | Evo - 5.18kg | LS Classic - 6.7kg | The Crumpton - 5.9kg

RyanH
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Joined: Tue Jan 17, 2012 4:01 pm
Location: Downtown Los Angeles, CA
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by RyanH

Nope, put it on the Caadx fork. HTA went to 75.7*. Cx fork isn't going to work.
Strava
Current Stable. The Snob Machine
The Ex's. LS Siena: 6.21kg | Parlee Z5 SLi: 5.9kg | LS Xicon: 5.76kg | C59: 5.7kg | Cervelo R5ca: 5.09kg | Fuji Altamira SE - 6.2kg | Scott Foil - 6.2kg | Evo - 5.18kg | LS Classic - 6.7kg | The Crumpton - 5.9kg

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dwaharvey
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Joined: Thu Oct 26, 2006 8:54 pm
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by dwaharvey

If it's 69.5 with 487 AC, then with the Enve mtn fork at 470 AC it ought to be ~70.5 deg (about 0.6 degrees for every 1cm of fork length). I think that's going to give you pretty decent handling. For comparison the Open Up in size M has an HTA of 71 with the specced fork length and rake of 50mm. Those numbers give a trail of 68mm, which is only 1mm different than your frame ought to be if you push the Enve fork offset out to its max of 52mm.

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