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Zeb Thread

Westy

the teste
Nov 22, 2002
54,475
20,275
Sleazattle
(DH Forum closes ANSYS to go get pitchforks and torches)

If you’re wondering why both forks use 15mm, rather than 20mm, axles, it’s because 20mm axles don’t necessarily make for a stiffer fork. It’s the enormous clamping force the axle provides (equivalent to about 5 metric tons), pressing the legs against the hub, that provides stiffness to the system.
 

Jm_

sled dog's bollocks
Jan 14, 2002
19,005
9,670
AK
I was gonna go with a Zeb for the weight savings, but that sounds like a sucker’s move (according to this author, of course)
Yeah, the fox seems decent, if you can get the steerer pressed in straight...also, the damping curve is pretty wacky according to Vorsprung.
 

ChrisRobin

Turbo Monkey
Jan 30, 2002
3,351
193
Vancouver
I'm wondering about that fore/aft stiffness.

RS only wanted to increase it by 2% over the Lyric, whereas Fox increased it a hell of a lot more. So that seems like a plus right? But what if RS only had to increase it by 2% to get close to where the 38 is now?
 

iRider

Turbo Monkey
Apr 5, 2008
5,653
3,093
(DH Forum closes ANSYS to go get pitchforks and torches)

If you’re wondering why both forks use 15mm, rather than 20mm, axles, it’s because 20mm axles don’t necessarily make for a stiffer fork. It’s the enormous clamping force the axle provides (equivalent to about 5 metric tons), pressing the legs against the hub, that provides stiffness to the system.
Wait, I thought there should be no high clamping forces otherwise the hub bearings would bind and die in no time??? :crazy:
 

Flo33

Turbo Monkey
Mar 3, 2015
2,068
1,307
Styria
Go ride a 15mm 36 and and then a 20mm one directly after it on an off camber rooty track- if you can't feel a difference go sell your bike. I rode a '19 36 for the last 18 months and then made a return to a 20mm one this summer thanks to @buckoW and did a direct comparison ride on my home trail in completely similar conditions. The difference in line holding ability over off camber roots was just impressive. I just don't get it why Fox doesn't use it on every 36 and 38.
 

Inclag

Turbo Monkey
Sep 9, 2001
2,752
442
MA
Sounds like most of Seb's criticism of the Zeb has to do with the air spring system differences and the issues he had echo verbatim all of the noted reasons why people thought the Debonair C1 air spring was a step backwards from the B1 version.
 

HardtailHack

used an iron once
Jan 20, 2009
6,765
5,667
I really don’t want a fork named “The Gimp”...
That's what Cannondale should have called the Lefty.

I looked at that, seems like it'd be damn near impossible to get the locktite in there. I'm still considering it, but we'll see. I'd like to stretch it out for at least another few months, but I may go to the bike park tomorrow too.
Could a freeze spray through the steerer help shrink it a bit?

1602850786018.png
 
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Westy

the teste
Nov 22, 2002
54,475
20,275
Sleazattle
Wait, I thought there should be no high clamping forces otherwise the hub bearings would bind and die in no time??? :crazy:
It depends a lot on the hub and is statically indeterminate, but the primary load path from clamping down should go through the hub axle, some additional load will go to the bearings depending on how much the hub axle compresses under that load.
 

Westy

the teste
Nov 22, 2002
54,475
20,275
Sleazattle
Go ride a 15mm 36 and and then a 20mm one directly after it on an off camber rooty track- if you can't feel a difference go sell your bike. I rode a '19 36 for the last 18 months and then made a return to a 20mm one this summer thanks to @buckoW and did a direct comparison ride on my home trail in completely similar conditions. The difference in line holding ability over off camber roots was just impressive. I just don't get it why Fox doesn't use it on every 36 and 38.
As those forks are heavier it is probably not a 1:1 comparison. The axle area may be stiffer, but so was the rest of the fork. Perhaps back to back testing with the same fork with the switchable axle sizes would be the most enlightening.
 

iRider

Turbo Monkey
Apr 5, 2008
5,653
3,093
It depends a lot on the hub and is statically indeterminate, but the primary load path from clamping down should go through the hub axle, some additional load will go to the bearings depending on how much the hub axle compresses under that load.
On fancy road wheels (e.g. Vision), where you can adjust bearing play with preloaders, they recommend adjusting the wheels while clamped in the frame.
 

Jm_

sled dog's bollocks
Jan 14, 2002
19,005
9,670
AK
I'm wondering about that fore/aft stiffness.

RS only wanted to increase it by 2% over the Lyric, whereas Fox increased it a hell of a lot more. So that seems like a plus right? But what if RS only had to increase it by 2% to get close to where the 38 is now?
Supposedly, the Lyrik is already a lot stiffer than the 36. Fox is kind of known for using dinky small crowns, so that may have something to do with it, vs. on the 38 they finally stiffened it up some compared to the 36.
 

HAB

Chelsea from Seattle
Apr 28, 2007
11,581
2,009
Seattle
I've got time on both, and the Zeb feels a little stiffer overall (especially torsionally) than the 38. Midstroke support from the Zeb isn't as firm as I'd like it to be, but small bump sensitivity is really good. I'm still fiddling with settings on the 38, but the compression damping adjustment range is surprisingly narrow, and pretty light.
 

Jm_

sled dog's bollocks
Jan 14, 2002
19,005
9,670
AK
That's what Cannondale should have called the Lefty.


Could a freeze spray through the steerer help shrink it a bit?

View attachment 150967
I'd think heating up the crown would be more effective, the aluminum crown is wrapping around the steerer and has a much greater circumference due to this, so due to it's rate of expansion, it should open up more. But perhaps a combination of packing the steerer with some ice or something and trying to heat the crown, I dunno. My usual trick for headset cups is put them in the freezer and heat up the head-tube with a hair-drier, then the cups go in pretty easy.

I put new uppers on order...but they are backordered.
 

Westy

the teste
Nov 22, 2002
54,475
20,275
Sleazattle
On fancy road wheels (e.g. Vision), where you can adjust bearing play with preloaders, they recommend adjusting the wheels while clamped in the frame.
That makes sense. Wonder if I could do that to finely center my brake rotors?
 

Flo33

Turbo Monkey
Mar 3, 2015
2,068
1,307
Styria
As those forks are heavier it is probably not a 1:1 comparison. The axle area may be stiffer, but so was the rest of the fork. Perhaps back to back testing with the same fork with the switchable axle sizes would be the most enlightening.
Both are 2019 36 Grip2 Factory 170 models, one a 650b and the other a 29" one. Guess which is which...
 

ChrisRobin

Turbo Monkey
Jan 30, 2002
3,351
193
Vancouver
Supposedly, the Lyrik is already a lot stiffer than the 36. Fox is kind of known for using dinky small crowns, so that may have something to do with it, vs. on the 38 they finally stiffened it up some compared to the 36.
That's makes way more sense.
 

ChrisRobin

Turbo Monkey
Jan 30, 2002
3,351
193
Vancouver
I've got time on both, and the Zeb feels a little stiffer overall (especially torsionally) than the 38. Midstroke support from the Zeb isn't as firm as I'd like it to be, but small bump sensitivity is really good. I'm still fiddling with settings on the 38, but the compression damping adjustment range is surprisingly narrow, and pretty light.
If you had to pick one fork, which one would it be?
 

Happymtb.fr

Turbo Monkey
Feb 9, 2016
1,920
1,272
SWE
Fox 38
torsional 31.5 Nm / °
Frontal 245.1 Nm / °

RS Zeb
torsional 37.9 Nm / °
Frontal 242.8 Nm / °

Based on the numbers in the article above and not totally relevant measurements made by ze Germans :
2016 Fox 36 with 170mm of travel for 27.5 and with pinched bolt yields:
torsional 22.8 Nm / °
Frontal 209.5 Nm / °
2017 Rockshox Yari / Lyrik, 27.5 with 170mm of travel for 27.5
torsional 31.3 Nm / °
Frontal 238.0 Nm / °
 

englertracing

you owe me a sandwich
Mar 5, 2012
1,581
1,076
La Verne
Yeah, the fox seems decent, if you can get the steerer pressed in straight...also, the damping curve is pretty wacky according to Vorsprung.
Its not that it's whacky its just that the hsc doesn't do much.

Where before the hs adjuster DID alot....
 

Trekrules

Turbo Monkey
Apr 12, 2007
1,226
148
New generation ZEB? looks like new lowers with air pressure release buttons like on the FOX 38.
s1200_IMG_20210808_WA0000.jpg
 

Happymtb.fr

Turbo Monkey
Feb 9, 2016
1,920
1,272
SWE
Whatever that is, it is attached to the damper side which would be the wrong side to monitor pressure in the positive chamber...

This fork looks really close to a production model with the decals for Bluetooth, CE approval etc below the pressure relief nipple.