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What Fork To Get?

spocomptonrider

sportin' the CROCS
Nov 30, 2007
1,412
118
spokanistan
So dumb question here, and I hate making the cliche motorcycle comparison... but if inverted designs are really that much worse why does every high end motorcycle use a usd fork? I realize that weight isn’t as much of an issue but at a racing level it is still important, and with the r&d budget of mfrs at the top end of that sport my lizard brain would think that if there were in fact some benefit to a standard design it would be adopted at the top level perhaps it’s one of those chicken and egg type conundrums, but again I know nothing...
 
So dumb question here, and I hate making the cliche motorcycle comparison... but if inverted designs are really that much worse why does every high end motorcycle use a usd fork? I realize that weight isn’t as much of an issue but at a racing level it is still important, and with the r&d budget of mfrs at the top end of that sport my lizard brain would think that if there were in fact some benefit to a standard design it would be adopted at the top level perhaps it’s one of those chicken and egg type conundrums, but again I know nothing...
Motorcycle, like bicycle, design is more marketing oriented than functional. Twiddle third order effects to sell more.
 

troy

Turbo Monkey
Dec 3, 2008
1,026
785
Motorcycle, like bicycle, design is more marketing oriented than functional. Twiddle third order effects to sell more.
Actually, right side up forks on motorcycles, unlike MTB forks, do not have one piece lowers.
1607553870382.png

With that in mind, it makes much more sense to go with an USD fork design, as upper tubes have much bigger OD (=moar stiffness) and bigger bushing overlap (=moar stiffness again), etc.
 

jonKranked

Detective Dookie
Nov 10, 2005
88,636
26,882
media blackout
Actually, right side up forks on motorcycles, unlike MTB forks, do not have one piece lowers.
View attachment 153416
With that in mind, it makes much more sense to go with an USD fork design, as upper tubes have much bigger OD (=moar stiffness) and bigger bushing overlap (=moar stiffness again), etc.
Plus at the weights they're using they don't have to sacrifice stiffness.

Also, see hondas first gen alloy dirt bike frames.
 

Jm_

sled dog's bollocks
Jan 14, 2002
20,062
10,626
AK
So dumb question here, and I hate making the cliche motorcycle comparison... but if inverted designs are really that much worse why does every high end motorcycle use a usd fork? I realize that weight isn’t as much of an issue but at a racing level it is still important, and with the r&d budget of mfrs at the top end of that sport my lizard brain would think that if there were in fact some benefit to a standard design it would be adopted at the top level perhaps it’s one of those chicken and egg type conundrums, but again I know nothing...
The application is much different. Many moto forks don't even have steerers as we know them, just a threaded piece of rod and bearing-cups at the top and bottom. With mountain bikes, we rely on the steerer as a structural member. If you look at the inverteds on street bikes, they are like 20" of fork for 3" of suspension travel with giant tubes and crowns. The bushing overlap is immense. Think about this for a few minutes and then think about the bushing overlap that you miss out on if you go to a single-crown inverted. Like the one thing that makes inverted at least "acceptable" in some applications is missing when you make it single-crown.

The dual crown moto forks make up for their lack of torsional rigidity with massive crowns and tubes, axle clamps, the degree to which we don't see due to weight concerns. Their biggest concern tends to be casing a a jump, but they still need torsional rigidity. So sometimes the argument is used that "well, inverted does better with fore-aft", but we can do the same by simply making our stanchions a little bigger and we end up with far better torsional rigidity while still weighing less than the inverted that would have adequate torsional rigidity.

When you start getting to enough travel, dual crown inverted becomes the only realistic option that has "enough" bushing overlap unless you start extending the lowers past the dropouts. For sure, this was done a bit, but the packaging starts to be an issue. For bicycles, this happens around 8" of travel. For motos, it's more. So for us, it's like, yeah, we could make a fork with 10" of travel, but you are going to lose out on a lot of rigidity, especially torsional, because we have to go to an inverted design. Do we need a foot of suspension? Maybe, but so far, no. For motos launching doubles and stuff, they seem to need a foot or more of suspension. They need a lot of bushing overlap to make that work with the big air/landings.

The only real-world advantage I ever experienced was better lubrication, it's definitely better for the oil to sit at the bottom on the seal...for the purpose of lubrication, but that is a double edged sword if you blow a seal and it ends up on the brake rotor. The shivers, both of em, would piss out a ton of oil if this happened. Even a semi-bath oil, if it blows, that's going right on your brake rotor, it doesn't take much to make it completely useless.

The unsprung weight thing ends up being insignificant, because lowers, dropouts, the lower parts of the internals, are not weightless and you have to add the brake rotor, brake, adapter, hub, axle, spokes, rim, rim strip, tire, etc., all to the unsprung weight. When you look at how light casted lowers are, they are pretty damn light and your % difference in unsprung weight ends up being very small, as in you'll get more difference with a different tire.

There's just no good reason to sacrifice that torsional rigidity on bikes.

Exotic manufacturing and designs can get around almost anything if you have unlimited funds, but then you'll end up spending many times what it actually costs and in the end you might get something "as good" that either ways way more or is many times more expensive, vs. putting that money into the conventional fork and ending up with something way better, lighter or cheaper. So there are some that have tried "keyways" in the stanchions and other ideas like Cannondale's square stanchions, to try and boost torsional stiffness, but there's just no point to dumping money and time into something that isn't going to offer a significant advantage.
 
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buckoW

Turbo Monkey
Mar 1, 2007
3,838
4,881
Champery, Switzerland
On an off-road motorcycle there is a decent amount of fork flex to help with deflection. It’s pretty wild how flexy they are but how well they track the ground. I’m terrible at moto and the compliant front end is pretty vague feeling but it gets me outta trouble all the time.
 

Flo33

Turbo Monkey
Mar 3, 2015
2,135
1,364
Styria
So dumb question here, and I hate making the cliche motorcycle comparison... but if inverted designs are really that much worse why does every high end motorcycle use a usd fork? I realize that weight isn’t as much of an issue but at a racing level it is still important, and with the r&d budget of mfrs at the top end of that sport my lizard brain would think that if there were in fact some benefit to a standard design it would be adopted at the top level perhaps it’s one of those chicken and egg type conundrums, but again I know nothing...
Steve has some answers, as always:
 

englertracing

you owe me a sandwich
Mar 5, 2012
1,657
1,143
La Verne
So dumb question here, and I hate making the cliche motorcycle comparison... but if inverted designs are really that much worse why does every high end motorcycle use a usd fork? I realize that weight isn’t as much of an issue but at a racing level it is still important, and with the r&d budget of mfrs at the top end of that sport my lizard brain would think that if there were in fact some benefit to a standard design it would be adopted at the top level perhaps it’s one of those chicken and egg type conundrums, but again I know nothing...
The amount of material involved and bushing overlap, and the amount of force from each direction.

Say the torsional forces were double on a motorcycle well the fore and aft forces might be 10x as high...

Also the way higher a2c on the motorcycle allows much more bushing overlap.

Another way to put it is that on a motorcycle a inverted fork that's strong enough not to fail is stiff enough torsional to not bother a rider. But its fore and aft stiffness is enough over an conventional fork that it is preferred

While on a bike, a inverted fork that's stiff enough not to fail is rather noodley in torsion to the point that its stiffness gain is outshadowed
 

Inclag

Turbo Monkey
Sep 9, 2001
2,775
459
MA
Soooooo from what I gather;

Zeb - Stiffest of the lot. Not a bad fork. Air spring will frustrate those of us that have ridden good suspension so be prepared to spend on an aftermarket fix as I would expect all the tuners to be developing something....or RS will release a D1 air spring which is really B1 old stock.....

Fox 38 - Will/when will it snap crackle pop? Otherwise haven't heard really any other negatives....

Mezzer - It may be really good, it may have QC issues, or it may/will snack crackle pop eventually. Probably has the most potential but also most risk.

This all makes a dual crown all the more tempting. Otherwise it seems that at least the RS has the best chassis of these new forks from what I gather.
 

HAB

Chelsea from Seattle
Apr 28, 2007
11,589
2,021
Seattle
Soooooo from what I gather;

Zeb - Stiffest of the lot. Not a bad fork. Air spring will frustrate those of us that have ridden good suspension so be prepared to spend on an aftermarket fix as I would expect all the tuners to be developing something....or RS will release a D1 air spring which is really B1 old stock.....

Fox 38 - Will/when will it snap crackle pop? Otherwise haven't heard really any other negatives....

Mezzer - It may be really good, it may have QC issues, or it may/will snack crackle pop eventually. Probably has the most potential but also most risk.

This all makes a dual crown all the more tempting. Otherwise it seems that at least the RS has the best chassis of these new forks from what I gather.
That's pretty much my take, having ridden all 3. I will say that the Mezzer that I have has been really solid — whether I got lucky and got a good one, or that's pretty representative, I can't say.

If the Zeb air spring was better, I think I'd love it. It's definitely the stiffest of the three (at a middle weight — the Mezzer is significantly lighter, and the 38 is a good chunk heavier) and the Charger 2.1 damper is pretty good.

The 38 is a good fork, but it's both heavier and less stiff than the Zeb, doesn't have the amazing midstroke support of the Mezzer (but better than the Zeb), and is the most expensive of the bunch.

If I were buying one tomorrow, it would be the Mezzer.
 

Jm_

sled dog's bollocks
Jan 14, 2002
20,062
10,626
AK
Soooooo from what I gather;

Zeb - Stiffest of the lot. Not a bad fork. Air spring will frustrate those of us that have ridden good suspension so be prepared to spend on an aftermarket fix as I would expect all the tuners to be developing something....or RS will release a D1 air spring which is really B1 old stock.....

Fox 38 - Will/when will it snap crackle pop? Otherwise haven't heard really any other negatives....

Mezzer - It may be really good, it may have QC issues, or it may/will snack crackle pop eventually. Probably has the most potential but also most risk.

This all makes a dual crown all the more tempting. Otherwise it seems that at least the RS has the best chassis of these new forks from what I gather.
I don't know about all of that, the Zeb and 38 haven't been out long enough to really know if they will stand the test of time and not creak. The Fox seems to have some QC issues with many shown to have the oval portion of the steerer not lining up correctly along the longitudinal axis. They tend to handicap stuff a little more with their crown designs too. Vorsprung did a good in-depth review of the 38. But again, I don't think enough time has passed to really tell whether these will creak in the future.

And you can't have an enduro because f*ck you. It's way too early, we need E-bikes to run around with 38s and Zebs for a while and then we'll realize they should have had dual crowns all along and everyone, even the non-e-bikers, can "upgrade" again. First we have to sell a bunch of 38mm forks.
 

buckoW

Turbo Monkey
Mar 1, 2007
3,838
4,881
Champery, Switzerland
"I only Listen to nickleback ironcally so that makes it okay."
Haha! What if I sing it ironically? « This is how you remind me » with heavy breathing....
I’m over 40, a foreigner and dgaf so I use that as an excuse to do what the fuck ever I want.... like snowboarding, DH bike riding, part time working, drinking, etc.... and if that involves some heavy breathing covers of Nickelback then fuck it! Looks like more fun than the real world!
 

Inclag

Turbo Monkey
Sep 9, 2001
2,775
459
MA
I don't know about all of that, the Zeb and 38 haven't been out long enough to really know if they will stand the test of time and not creak. The Fox seems to have some QC issues with many shown to have the oval portion of the steerer not lining up correctly along the longitudinal axis. They tend to handicap stuff a little more with their crown designs too. Vorsprung did a good in-depth review of the 38. But again, I don't think enough time has passed to really tell whether these will creak in the future.

And you can't have an enduro because f*ck you. It's way too early, we need E-bikes to run around with 38s and Zebs for a while and then we'll realize they should have had dual crowns all along and everyone, even the non-e-bikers, can "upgrade" again. First we have to sell a bunch of 38mm forks.
From what I gather folks have already encountered the creaky 38's but not many reviewers have. I also get the sense the air spring and damper is a little more sorted. I'd love to consider a Mezzer, but damn that seems risky. Known bushing issues and reported creaking make me nervous and at that weight it seems all the more not a question about if, but a matter of when. I don't love SRAM products, but I've got to give it to them. They seem to be producing the best chassis' these days....

Why does dual crown seem most appropriate???
 

Happymtb.fr

Turbo Monkey
Feb 9, 2016
2,066
1,437
SWE
Why does dual crown seem most appropriate???
More better
Proven shit
20mm axle
Not much more weight
No creak
...
And just to tease the "threaded BB shell and space for a bottle cage"-crowd who also believes that you cannot turn with a dual crown :dirol:
 

Inclag

Turbo Monkey
Sep 9, 2001
2,775
459
MA
More better
Proven shit
20mm axle
Not much more weight
No creak
...
And just to tease the "threaded BB shell and space for a bottle cage"-crowd who also believes that you cannot turn with a dual crown :dirol:
Thank you for confirming my biases....when I rip off my headtube and break my face now I'll be able to sleep well knowing I can blame others besides myself.....
 

Bikael Molton

goofy for life
Jun 9, 2003
4,088
1,235
El Lay
No creaks or complaints with my 38 so far.

As far as the air spring, it's the most supple off the top that I've ever ridden, including the B1 LyriK that I liked a lot. Mid-stroke support seems good.
 

kidwoo

Artisanal Tweet Curator
Haha! What if I sing it ironically? « This is how you remind me » with heavy breathing....
I’m over 40, a foreigner and dgaf so I use that as an excuse to do what the fuck ever I want.... like snowboarding, DH bike riding, part time working, drinking, etc.... and if that involves some heavy breathing covers of Nickelback then fuck it! Looks like more fun than the real world!
"I only Listen to nickleback ironcally so that makes it okay."









;)
 

UnusualBread

Chimp
Nov 2, 2020
26
18
I can chime in on mezzer vs a 38 performance (w/ 3pos Grip). Ended up preferring mezzer by far. The mid stoke you can tune in gives me a hell of a lot more confidence when riding at the limit which is what I personally care about. Both are good forks but I'm pretty picky.

Fox 38 chassis is decent with low friction (on par with mezzer). I struggled a bit with air spring and damper, feeling like when I had mid stroke support I wanted, I was sacrificing on small bump and end of stroke/bottom out (not using more travel when it felt warranted), or vice versa. Dampening also felt loose/digressive and the LSC adjuster added harshness, not as much support (I wanted more mid/high speed dampening). Can't say how much GRIP 2 damper would improve things but I'd guess that it would not be enough to close the gap to mezzer for me.

Found I can run a crap ton of compression dampening on the Mezzer without it getting harsh.
 

Kanye West

220# bag of hacktastic
Aug 31, 2006
3,767
501
That's pretty much my take, having ridden all 3. I will say that the Mezzer that I have has been really solid — whether I got lucky and got a good one, or that's pretty representative, I can't say.

If the Zeb air spring was better, I think I'd love it. It's definitely the stiffest of the three (at a middle weight — the Mezzer is significantly lighter, and the 38 is a good chunk heavier) and the Charger 2.1 damper is pretty good.

The 38 is a good fork, but it's both heavier and less stiff than the Zeb, doesn't have the amazing midstroke support of the Mezzer (but better than the Zeb), and is the most expensive of the bunch.

If I were buying one tomorrow, it would be the Mezzer.
Have the stiffnesses been tested accurately on the 38 and Zeb? I see conflicting claims of that all over the place.
 

HAB

Chelsea from Seattle
Apr 28, 2007
11,589
2,021
Seattle
Have the stiffnesses been tested accurately on the 38 and Zeb? I see conflicting claims of that all over the place.
If there is, I haven't seen it. Would definitely be interesting.

I've A/B compared the two on the same bike and I'm confident in my assessment that the Zeb feels stiffer, especially in torsion. For whatever that's worth.