Enduro/AM - The Weight Game

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Enduro/AM - The Weight Game
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flag swan3609
O+
Posted: Sep 2, 2020 at 13:39 Quote
R-M-R wrote:
clapforcanadaa wrote:
Haha, yeah I'm still here (barely). Not so much time with a 5 month old baby, another one due in a month and the industry in such a boom. I'll be back full time when I'm fully bald, nice little gut and too out of shape to be a Strava dick anymore.

Sounds like you're still pretty fast if you can make two babies in six months.

Just going to bring up how funny this was.


Also manager has a MRP Bartlett on his 2020 Enduro.. It's real good.
flag PHeller
O+
Posted: Sep 2, 2020 at 13:43 Quote
I read somewhere that a quite a large portion of the flex we can perceive in the fork is from the crown or csu.

So it's something like 40/30/20 Crown/Bushing/Stanchion. Maybe throw in hub/axle stiffness for a few percentage points. It's also my understanding that the bigger seals and bigger bushings allow more tolerance with less friction.

The idea being that if you make the crown stiffer, it's easier to isolate the flex elsewhere in the chassis, which is partly why 35mm stanchions were so good for so long.

So if you increase the stiffness a little bit in every part, its combined feel is more direct/rigid/smooth yes, but the crown (or dual crown) would have the biggest impact on overall stiffness, especially at longer travels.

This is also why you might have seen people say you could "make a 32mm dual crown as stiff as a 35mm single crown". That might have Chris Porter.

The Zeb, 38 and Mezzer are just minor improvement in all 3 areas of flex.

But I bet if you ran a Bartlet or a Boxxer against any of the big single crowns, you'd immediately notice a big increase in stiffness from the dual crown.
flag PHeller
O+
Posted: Sep 2, 2020 at 13:47 Quote
Also, the Lefty Supermax 160 was as stiff if not stiffer than the 36 of the same time despite it only having HALF the fork (the Supermax was also a 36mm square stanchion). That's because the roller bearings, the dual crown, the bigger outer tubes all contributed to its increased "perceived" stiffness over its competitors.
flag clapforcanadaa
O+
Posted: Sep 2, 2020 at 14:03 Quote
R-M-R wrote:
clapforcanadaa wrote:
Haha, yeah I'm still here (barely). Not so much time with a 5 month old baby, another one due in a month and the industry in such a boom. I'll be back full time when I'm fully bald, nice little gut and too out of shape to be a Strava dick anymore.

Sounds like you're still pretty fast if you can make two babies in six months.

LOL

We were picked to adopt a baby girl while my wife was already 12 weeks pregnant. We found out about the adoption 4 days before she was born. Things escalated quickly!
flag clapforcanadaa
O+
Posted: Sep 2, 2020 at 14:03 Quote
whattheheel wrote:
clapforcanadaa wrote:
NorCalNomad wrote:
So basically he's built up a mid 2000's FR bike...weight and all

Seems like this is the thread where all the long time pb'ers still are (re:CFC)

Haha, yeah I'm still here (barely). Not so much time with a 5 month old baby, another one due in a month and the industry in such a boom. I'll be back full time when I'm fully bald, nice little gut and too out of shape to be a Strava dick anymore.

What'd you call me bitch??? lol lol

Hahaha, didn’t want to call you out like that!
flag whattheheel
Posted: Sep 2, 2020 at 14:06 Quote
And answer your dash too!! Slacker!
flag R-M-R
Posted: Sep 2, 2020 at 14:09 Quote
clapforcanadaa wrote:
We were picked to adopt a baby girl while my wife was already 12 weeks pregnant. We found out about the adoption 4 days before she was born. Things escalated quickly!

Figured it must've been something like that. Congratulations / you have my sympathies! lol
flag clapforcanadaa
O+
Posted: Sep 2, 2020 at 14:17 Quote
whattheheel wrote:
And answer your dash too!! Slacker!

What is dash?
flag tom666
Posted: Sep 2, 2020 at 14:41 Quote
R-M-R wrote:
"A little knowledge is a dangerous thing."

Yes, large diameters can make components uncomfortably stiff, but only due to the overall stiffness. Larger stanchions with a less-stiff crown probably aren't stiffer than smaller stanchions with a double-crown. 40 mm stanchions on a 1998 SID crown and steerer wouldn't be uncomfortably stiff - or stiff at all. I don't have data on Zeb vs. Boxxer, but if the Zeb were stiffer, I suspect we would quickly see a 200 mm version and the Boxxer would cease to exist.

Are you sure about bushing bind on single-crowns? Below the crown, there's no reason a single-crown and double-crown should behave differently.

I feel similarly - surely overall/resultant stiffness is what would create fatigue. I very much doubt a ZEB is stiffer than a Boxxer so I don't think it would create fatigue for that reason.

It could be that there's nothing at all to the claims he's heard - but for whatever reason people he knows who have tried ZEBs and 38s (lots of which will be pros just because of the circles the guy moves in) think they're harsh on the hands. My friend is convinced by what he's heard, but like I said, I'm not sure I am. I'd like to try one.

About the binding - I think it's highly likely that the dual crown is better at keeping the stantions in line than a single crown fork. The Boxxer is a meaty fork and fixed in two places instead of one, which is surely likely to be better at resisting forces and keeping everything straight and concentric when things get hairy.
flag PHeller
O+
Posted: Sep 2, 2020 at 15:12 Quote
clapforcanadaa wrote:
whattheheel wrote:
And answer your dash too!! Slacker!

What is dash?

Dashboard stuff. Like, people posting to your dashboard and things.
flag mtbman1980
O+
Posted: Sep 2, 2020 at 15:18 Quote
tom666 wrote:
R-M-R wrote:
"A little knowledge is a dangerous thing."

Yes, large diameters can make components uncomfortably stiff, but only due to the overall stiffness. Larger stanchions with a less-stiff crown probably aren't stiffer than smaller stanchions with a double-crown. 40 mm stanchions on a 1998 SID crown and steerer wouldn't be uncomfortably stiff - or stiff at all. I don't have data on Zeb vs. Boxxer, but if the Zeb were stiffer, I suspect we would quickly see a 200 mm version and the Boxxer would cease to exist.

Are you sure about bushing bind on single-crowns? Below the crown, there's no reason a single-crown and double-crown should behave differently.

I feel similarly - surely overall/resultant stiffness is what would create fatigue. I very much doubt a ZEB is stiffer than a Boxxer so I don't think it would create fatigue for that reason.

It could be that there's nothing at all to the claims he's heard - but for whatever reason people he knows who have tried ZEBs and 38s (lots of which will be pros just because of the circles the guy moves in) think they're harsh on the hands. My friend is convinced by what he's heard, but like I said, I'm not sure I am. I'd like to try one.

About the binding - I think it's highly likely that the dual crown is better at keeping the stantions in line than a single crown fork. The Boxxer is a meaty fork and fixed in two places instead of one, which is surely likely to be better at resisting forces and keeping everything straight and concentric when things get hairy.

In my simplistic understanding the location of the clamp should be where the bending forces will happen so that would be the lower crown in a dual crown fork the same a single crown. There could be something I'm missing though.
flag whattheheel
Posted: Sep 2, 2020 at 15:20 Quote
PHeller wrote:
clapforcanadaa wrote:
whattheheel wrote:
And answer your dash too!! Slacker!

What is dash?

Dashboard stuff. Like, people posting to your dashboard and things.

No. it's this:
photo
flag Twenty6ers4life
O+
Posted: Sep 2, 2020 at 15:29 Quote
mtbman1980 wrote:
tom666 wrote:
R-M-R wrote:
"A little knowledge is a dangerous thing."

Yes, large diameters can make components uncomfortably stiff, but only due to the overall stiffness. Larger stanchions with a less-stiff crown probably aren't stiffer than smaller stanchions with a double-crown. 40 mm stanchions on a 1998 SID crown and steerer wouldn't be uncomfortably stiff - or stiff at all. I don't have data on Zeb vs. Boxxer, but if the Zeb were stiffer, I suspect we would quickly see a 200 mm version and the Boxxer would cease to exist.

Are you sure about bushing bind on single-crowns? Below the crown, there's no reason a single-crown and double-crown should behave differently.

I feel similarly - surely overall/resultant stiffness is what would create fatigue. I very much doubt a ZEB is stiffer than a Boxxer so I don't think it would create fatigue for that reason.

It could be that there's nothing at all to the claims he's heard - but for whatever reason people he knows who have tried ZEBs and 38s (lots of which will be pros just because of the circles the guy moves in) think they're harsh on the hands. My friend is convinced by what he's heard, but like I said, I'm not sure I am. I'd like to try one.

About the binding - I think it's highly likely that the dual crown is better at keeping the stantions in line than a single crown fork. The Boxxer is a meaty fork and fixed in two places instead of one, which is surely likely to be better at resisting forces and keeping everything straight and concentric when things get hairy.

In my simplistic understanding the location of the clamp should be where the bending forces will happen so that would be the lower crown in a dual crown fork the same a single crown. There could be something I'm missing though.


I think the implication is that in a single crown fork, the crown would flex/twist forward more under full compression whereas a dual crown would not flex as much because the upper clamp would help keep the lower clamp from flexing as much as it would in a single clamp. So more chopper affect for a single crown, and more bushing stiction as well. So it would seem. I could be wrong though.
flag kwapik
Posted: Sep 2, 2020 at 16:01 Quote
R-M-R wrote:
clapforcanadaa wrote:
Haha, yeah I'm still here (barely). Not so much time with a 5 month old baby, another one due in a month and the industry in such a boom. I'll be back full time when I'm fully bald, nice little gut and too out of shape to be a Strava dick anymore.

Sounds like you're still pretty fast if you can make two babies in six months.

Yeah - the math isn't adding up Wink Wink

Congratulations on the adoption!
flag R-M-R
Posted: Sep 2, 2020 at 16:05 Quote
tom666 wrote:
About the binding - I think it's highly likely that the dual crown is better at keeping the stantions in line than a single crown fork. The Boxxer is a meaty fork and fixed in two places instead of one, which is surely likely to be better at resisting forces and keeping everything straight and concentric when things get hairy.

There are no forces from the crown below the crown. Its influence on the stress profile ends a few millimeters below the lower / only crown. The bending moment increases steadily and smoothly from the bottom up to the top, then there's a stress concentration at the lower edge of the crown (which should be mostly mitigated by the shape of the crown), and an abrupt change in shear force at the edge of the crown. As I said, below the crown, the rest of the fork has no idea what kind of crown is above it.

The only difference would be if there was enough flex to significantly change the angle of the stanchions, which is not the case; a degree, maybe, but not the many degrees that would be necessary to significantly change the bending moments.


Twenty6ers4life wrote:
I think the implication is that in a single crown fork, the crown would flex/twist forward more under full compression whereas a dual crown would not flex as much because the upper clamp would help keep the lower clamp from flexing as much as it would in a single clamp. So more chopper affect for a single crown, and more bushing stiction as well. So it would seem. I could be wrong though.

Your thinking is correct, but the effect is small. It's not zero, but if double-crowns were dramatically more effective at reducing the flex you describe, we would all be on double-crowns because they would be a lot lighter for a given level of stiffness. The transition point where double-crowns could be lighter for the same mechanical properties occurs somewhere toward the upper range of the single-crown spectrum, though we stick with single-crowns for convenience and aesthetics. The balance would tip a little more in favour of double-crowns if we allowed dedicated steerer tubes, headsets, and head-tubes for each.

 


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