Ebike Optimized Forks Or Not

[HikerDave]

How does the fork "know" that it is attached to an ebike that weighs a bit more than a clockwork bike?
The fork will be designed to have a max (rider + bike) weight in mind from a stiffness and strength viewpoint to withstand static and the huge range of dynamic loading. What I'm struggling to identify is what physical or engineering laws state that a 120kg (bike +rider) combo will affect the design of the fork if the proportional split between bike and rider was a variable?

An eBike’s moment of inertia about the bottom bracket / motor is higher because of the massive battery. So the fork will ‘know’ because the head tube is moving less. The rear shock should feel a bit less from a front impulse. I would also expect that an eBike rider would feel a bit less hand shock from a front impulse.

That said, I can’t understand why an eBike-specific fork is necessary; the tune for my Fox 36 / Avalanche fork from my human-powered bike feels just as good on my eBike.

 

[SlowNoob]

I'd hazard a guess that the 'average' ebike rider is heavier than the 'average' none 'e' bike rider too. (i realise there are plenty of extremely fit people now using ebikes now, and many people who are heavier using normal bikes.....but i also think there are a lot of people who consider themselves unfit/overweight that have missed being out on a bike and see their only option of enjoying a ride being an electric bike......i myself as a very overweight person, really struggled on a normal bike, and would never have made the initial investment on a non electric bike, and only considered getting any kind of bike because ebikes are available......this group of people will naturally make the 'average' e bike rider heavier) maybe they realised that 30% of their warranty claims were from ebikes when only 20% of their forks were being used on ebikes? or maybe they thought there was a gap in the market to fill? maybe they thought it was a product they could make slightly more profit from, and that the public would chose an ebike specific forks over none e bike ones if given the choice, and therefore all the companies that already use a fox 36 would swap to the 36 e bike specific for fear of looking like they had a lower spec?

 

[raine]

All this time all I was saying was that there's a difference, and it has to do with total machine capacity. I'm not changing the details to fit a narrative - in other words, I'm not compensating to make a comparison equal (which everyone seems to keep doing). Maybe people just aren't realizing that to make the "it's the same system weight" argument seem valid, they're changing the weight of the rider when that rider gets on a lighter or heavier bike.

So once more, I'll try to explain it with simple addition... no physics laws or engineering laws or riding style or "radness" level required - just simple weight measurements and addition:

SAME RIDER AT 210-lbs.

- Bike A "Standard" Build (35-lbs. non-E-Bike) + "Standard" Fork (250-lbs. capacity)
This bike can support up to 215-lbs. of rider weight

- Bike B "E-Bike" Build (45-lbs. E-Bike) + "E-Bike" Fork (290-lbs. capacity)
Bike bike can support up to 245-lbs. of rider weight

Results:
- Rider CAN ride Bike A (210 rider + 35 bike = 245 , under 250-lbs. fork limit)
- Rider CAN ride Bike B (210 rider + 45 bike = 255 , under 290-lbs. fork limit)

All good, the same rider can ride either bike. Now then - without compensating by altering rider weight or bike weight, simply swap the forks; Put the E-Specific Fork onto Bike A, and put the Standard Fork on Bike B. REMEMBER - You're only changing ONE variable, using the SAME rider with the SAME weight and not compensating for bike weight difference!

Now by just swapping the Standard and E-Bike specific forks to the other bike, you get a different (and telling) result:

SAME RIDER AT 210-lbs.

- Bike A "Standard" Build (35-lbs. non-E-Bike) + "E-Bike" Fork (290-lbs. capacity)
This bike can now support up to 255-lbs. of rider weight

- Bike B "E-Bike" Build (45-lbs. E-Bike) + "Standard" Fork (250-lbs. capacity)
Bike bike can now only support up to 205-lbs. of rider weight

- Rider CAN STILL ride Bike A + E-Bike Fork (210 rider + 35 bike = 245 , under 290 fork limit)
- Rider CANNOT ride Bike B + Standard fork (210 rider + 45 bike = 255, over 250 fork limit)

Those arguing against will compensate by changing the weight of the rider lower to get them under the weight limit... if I used a 200-lbs (or less) rider as an example, then the rider would be well under the limit for all 4 scenarios, and then people would say "OMG SEE THERE IS NO DIFFERENCE!" but that's why I used a rider who's weight is near the upper limit, in order to show that there was a difference after all, and again - it's about total machine capacity.

BUT WAIT Do you need an E-Bike specific fork? Is it necessary? Can you use a non-E-Bike fork on an E-Bike? Do you ride rad enough to push the limits? Dunno, don't care. I was never saying anything of the sort - other people brought these tangents into the original purpose of the thread - the OP's question in post #1:

is there much difference between ebike optimized fox 36 forks and a set that isnt ebike opt?

And my answer was simply "Yes, there's a difference." See above.

Side note: This is probably the last post I'll make in this thread explaining that there is a difference between the fork designs. It's been fun, but more recently any response to anything I say has been increasingly hostile, and I don't want to make any enemies on this forum. If after reading this post people still disagree with it, then that's fine. I just thought of a more simple way to try to explain that there was a difference, so I typed it above.

Have a good week, everyone

 

[Ducatijones]

Wow that was thorough, Cheers guys for all the feedback. I am still looking for forks, not sure what to get yet but after looking around only fox make specific ebike forks. If I can save a couple of hundred quid buying non ebike good forks I think I will. Thanks all.

 

[Jamsxr]

My friend sent me a picture of some Kenevo forks after a Surrey Hills session at the weekend... ?

 

[Ducatijones]

That's nasty. If it wasnt damage from a crash, could he claim on warranty ?...... oh and the important question, Are they Ebike Optimized forks ?

 

[Jamsxr]

It did make me chuckle seeing this after reading all the posts on how eBike specific forks are pointless.

It’s not from a crash. I know this guy likes big jumps and has the skill to match, so it’s not your average rider.

I think the Kenevo just has standard the Lyrik.

 

[Ducatijones]

Well that's given me something to think about jamsxr. More sleepless nights cheers ?

 

[R120]

I think the could happen, and I have seen it happen, on any bike. All that says to me is put some dual crown forks on!

 

[Russell]

Lucky he spotted that before hitting another jump. It makes me think if your going to be doing jumps and DH then maybe you should go tripple clamp sooner than you would on a normal pedal bike. I certainly noticed way more flex on my old suntour forks than I have on a MTB before, I suppose another 10-20kg plus slack geometry of modern bikes.

 

[Jamsxr]

Yep, saw a Kenevo on the trails with some 40’s, it looked tidy and still seem to pedal okay.

I don’t think you’re necessarily missing out if you don’t have eBike specific forks but there’s definitely a case for them. eBikes are over 60% heavier so a stronger crown and stanchions won’t go a miss in my book.

 

[R120]

For me its the crown rather than the stanchions that are the concern - my understanding of the fox ebike specific ones is that have thicker stanchions, but also a solid crown rather than a hollow one.

 

[bowser]

if i buy bike F36 with the thicker legs and 34 Air spring, does that prevent me from adding an AC3 spring conversion later on if I want too? wondering if i am better buying the non ebike forks to allow this option later if i want

 

[drjarvis2003]

I think the could happen, and I have seen it happen, on any bike. All that says to me is put some dual crown forks on!

Good point and i have thinking about putting 180mm Boxxers on my Merida E 160. Already running 180mm Lyriks with a Works angle headset, so geo should not be a problem. Only issue i can see is that triple clamp forks still run 1/1/8th steerer tubes. Has anyone else figured this one out?

 

[Gary]

you simply need to run a crown race reducer to fit any straight steerer fork in a tapered head tube.
eg.
Nukeproof Reducer Crown Race | Chain Reaction Cycles
(assuming it fits the lower sealed bearing in your current headset)
If you didn't already have one I'm pretty sure you can buy tapered to straight angle headsets too.

a 180mm boxxer (raised in the crowns) is actually slighlty shorter axle to crown than a 180mm Lyrik so you could run 200mm and keep (static) geometry pretty much the same as you have just now.

Not really sure why you'd want to put a modern Boxxer on a E160 though.
They're heavier, have less turning radius, you can no longer X-up and the E160 doesn't exactly have DH race bike geometry Unless you prefer old skool (early 2000s) DH geo.

 

[drjarvis2003]

you simply need to run a crown race reducer to fit any straight steerer fork in a tapered head tube.
eg.
Nukeproof Reducer Crown Race | Chain Reaction Cycles
(assuming it fits the lower sealed bearing in your current headset)
If you didn't already have one I'm pretty sure you can buy tapered to straight angle headsets too.

a 180mm boxxer (raised in the crowns) is actually slighlty shorter axle to crown than a 180mm Lyrik so you could run 200mm and keep (static) geometry pretty much the same as you have just now.

Not really sure why you'd want to put a modern Boxxer on a E160 though.
They're heavier, have less turning radius, you can no longer X-up and the E160 doesn't exactly have DH race bike geometry Unless you prefer old skool (early 2000s) DH geo.

X up not really my thing, but I hear what you are saying about turn radius and thought about that myself before, as I ride some of the same places you do, like golfie, thornilee and dunkeld, where it can get pretty tight sometimes. Only reason I was thinking about it was for steering precision. Maybe just wait for the 2020 vitus !

 

[raine]

For me its the crown rather than the stanchions that are the concern - my understanding of the fox ebike specific ones is that have thicker stanchions, but also a solid crown rather than a hollow one.

Fox e-bike specific forks have extra material in the fork crown and thicker stanchions. Also, the 36 e-bike fork uses a FOX 34 air spring, and the lower legs are the same as a regular FOX 34 fork. So basically the upper half is where there is a difference.

 

[Ducatijones]

There seems to be a lot of e-bikes out there that have got forks that are not e-bike specific. They seem to manage ok dont they ?

 

[raine]

There seems to be a lot of e-bikes out there that have got forks that are not e-bike specific. They seem to manage ok dont they ?

LOL well the bike on post #65 didn't

If you want to put a fork on your bike that will "manage ok" that's up to you. You have 50% of the people here telling you there is a difference between e-bike and non-ebike forks and 50% of the people here telling you that they think there isn't.

Honestly, With your last few comments it really sounds like you're trying to justify to yourself that you're going to be ok by choosing to save some $$ and buy a non e-bike specific fork, and you're looking for people to tell you "yeah man, it's ok."

Not sure if you said it earlier, but the fork you "twisted" that was on your Trek, what actual fork was it?

 

[Ducatijones]

Ha ha yes tell me it's ok to save about £400 odd quid on a pair of 36 non e-bike specific forks. The pair I twisted were specific forks, but damaged due to my crash and stupidity at the end of a ride . I have seen the damage on post #65 as well, but there must be a case for using non specific otherwise there would be bikes falling to bits.

 

[raine]

Ha ha yes tell me it's ok to save about £400 odd quid on a pair of 36 non e-bike specific forks. The pair I twisted were specific forks, but damaged due to my crash and stupidity at the end of a ride . I have seen the damage on post #65 as well, but there must be a case for using non specific otherwise there would be bikes falling to bits.

I’m sure there is a case but that’s not the point - look, you already broke an e-bike specific fork, right? And you want to replace it with a fork that isn’t built as stout so you can save money? How does that make sense... lol

 

[Ducatijones]

The crash I had might have bent a set of motorbike forks, going to fast for the conditions. I am honest enough to say it was my fault and have listened to the arguments for and against specific forks, but I dont think there is a winner. But what do I know lol. ?

 

[Rusty]

Seriously, with ANY component there are many variables. Rider weight, bike weight & types of trails/riding done, are the main ones but there are lots more.
Rider skill level - a grom rider that does lots of ramp type jumps (say off little ridges on the side of a trail) and flat lands will put different stress on a bike than an ace that does big hucks and gap jumps, but lands nicely on the down ramp. The volume of the tires makes a big difference with someone on 2.2-2.3 tires transmitting more stress into the suspension than someone on 2.6 or 2.8 tires. You also have to take into account how the suspension has been set up. Last night I was playing on some jumps to see how the extra weight of my 700Wh battery would effect the bike in flight and there was a guy on a Levo like mine - I could hear his suspension clunk with most of his landings, where me at probably 20kg heavier was gliding them.

 

[raine]

The crash I had might have bent a set of motorbike forks, going to fast for the conditions. I am honest enough to say it was my fault and have listened to the arguments for and against specific forks, but I dont think there is a winner. But what do I know lol. ?

You’re right - there is no “winner” because at this point you’re not comparing just fork vs e-bike fork - you’re also adding in your budget. But I’m pretty sure you have more that enough information from this thread (whether it’s actual facts and figures vs. personal opinions, justified or not) to actually decide what is right for your purpose and your specific needs. GLHF

 

[khorn]

LOL well the bike on post #65 didn't

If you want to put a fork on your bike that will "manage ok" that's up to you. You have 50% of the people here telling you there is a difference between e-bike and non-ebike forks and 50% of the people here telling you that they think there isn't.

Honestly, With your last few comments it really sounds like you're trying to justify to yourself that you're going to be ok by choosing to save some $$ and buy a non e-bike specific fork, and you're looking for people to tell you "yeah man, it's ok."

Not sure if you said it earlier, but the fork you "twisted" that was on your Trek, what actual fork was it?

Are you paid by FOX?

Karsten

 

[Jamsxr]

Not sure how this is still a debate, eBikes are heavier, manufacturers have since brought to market stronger components, simple. You will likely be okay with non eBike specific forks, but if you want to take the belt and braces approach, go for eBike forks - they are stronger.

I snapped my pedal clean off landing/casing a 20 foot double this evening, I need eBike specific pedals now ?

 

[raine]

Are you paid by FOX?
Karsten

LOL no I'm actually a Rockshox/SRAM guy, with the exception of the Shimano E8000 system on my bike.

So what's your point? Hahaha

 

[raine]

Not sure how this is still a debate, eBikes are heavier, manufacturers have since brought to market stronger components, simple. You will likely be okay with non eBike specific forks, but if you want to take the belt and braces approach, go for eBike forks - they are stronger.

Agree 100% to the above.

 

[Welshman]

If the riders is already 120kgs....would e specific forks make any difference???

Casing point

90kg rider + 10kg mtb = 100kg
80kg rider + 20kg ebike = 100kg

What difference would the e bike specific fork make if both = 100kgs

 

[raine]

If the riders is already 120kgs....would e specific forks make any difference???

Casing point

90kg rider + 10kg mtb = 100kg
80kg rider + 20kg ebike = 100kg

What difference would the e bike specific fork make if both = 100kgs

Since you don't even read the thread, start with #63.