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Fork Rake on 27"(650b)forks, marketing wank or needed?

no skid marks

Monkey
Jan 15, 2006
2,514
26
ACT Australia
So all the forkers are making 650b specific forks, is this just to assure sales,or are 26" forks that can take 27" wheels going to really feel dud in any way? What does it even counter act? Are the 26s lazier from crown down?
 
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Tomasis

Monkey
Feb 26, 2003
681
0
Scotland
i think he meant offset thing.

Bos forks 650b seem have changed only offset by adjusting steerer/crown thing. Not lowers.
 

ptd

Chimp
Oct 16, 2011
22
15
Yeah I'd say offset is important when considering the trail measurement, same as all wheel size/head angle combos.

I'm running 650b on a bike with adjustable HA, in slackest it feels like the trail is too long with too much flop/wheel push/oversteer. With a steeper HA setting it feels fine.

So I'm interested in the more fork offset being advertised recently (x-fusion/bos/sr suntour) to reduce the trail a bit..
 
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Feb 26, 2003
32
0
plovdiv & boston
Trail (mechanical) will increase by less than 6mm if you go from a 26 to a 27 rim and use the "same" tire. And since this is the Downhill forum, in steering feel that is roughly equivalent to slackening the head angle by 1 degree or raising the crowns by 20-25mm. It can be felt by some of the riders, but it's far from significant. And why oh why would someone want less trail on a go-fast bike?
 

Sandwich

Pig my fish!
Staff member
May 23, 2002
16,259
1,157
01776
Offset affects trail which affects steering "sharpness". 29ers (THE DEVIL) are bandied about with something called G2 crowns (THANKS GARY) which increase offset and return steering sharpness to be comparable to 26ers (FLICKABILITY). That way you can maintain the same headtube angle (YAW KNOW WHAT I MEAN) as a 26er with similar feel.

In line with that thought, a 650b (WHY BOTHER) wheel will need a less drastic bump in offset to maintain similar geometries to 26" (NOT FROM MY COLD DEAD HANDS). In practice, most people agree that this is true. My lefty with 650b handles comfortably and not dissimilarly from a 26er (NO PRACTICAL EXPERIENCE ALLOWED) but the lefty has 45mm of offset vs. the more typical ~40mm of a REBAr or Float.

The boxxer has 42, the 40 has 45mm, the 888 has 46mm, the Durdo appears to have 49.55mm.
 
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frorider

Monkey
Jul 21, 2004
964
11
cali
Trail (mechanical) will increase by less than 6mm if you go from a 26 to a 27 rim and use the "same" tire. And since this is the Downhill forum, in steering feel that is roughly equivalent to slackening the head angle by 1 degree or raising the crowns by 20-25mm. It can be felt by some of the riders, but it's far from significant. And why oh why would someone want less trail on a go-fast bike?
Agree with your first and last points. Not sure I agree with your middle point --- slackening a HA by 1 degree is noticeable, and not insignificant.
 

syadasti

i heart mac
Apr 15, 2002
12,721
290
VT
In line with that thought, a 650b (WHY BOTHER) wheel will need a less drastic bump in offset to maintain similar geometries to 26" (NOT FROM MY COLD DEAD HANDS). In practice, most people agree that this is true. My lefty with 650b handles comfortably and not dissimilarly from a 26er (NO PRACTICAL EXPERIENCE ALLOWED) but the lefty has 45mm of offset vs. the more typical ~40mm of a REBAr or Float.

The boxxer has 42, the 40 has 45mm, the 888 has 46mm, the Durdo appears to have 49.55mm.
Most of the latest long travel 29er forks have 51mm. The Lefty Supermax 130mm 29er has 61mm.
 

Sandwich

Pig my fish!
Staff member
May 23, 2002
16,259
1,157
01776
Most of the latest long travel 29er forks have 51mm. The Lefty Supermax 130mm 29er has 61mm.
yeah G2 is pretty much synonymous with 51mm offset. I didn;t know the lefty superlunch is that big though, that's a lot.
 
Feb 26, 2003
32
0
plovdiv & boston
Agree with your first and last points. Not sure I agree with your middle point --- slackening a HA by 1 degree is noticeable, and not insignificant.
Fair enough, but maybe just semantics - significant and insignificant in our statements are the extremes. A single degree HA change is somewhere in between, it won't make the bike unrideable. Going for example from 64 to 63 won't be as drastic as going from 64 to 59.