20" Fat e-bike front fork dual crown

[Residents evil]

I'm planning to fully rebuild my bike and would like to upgrade the current fork​

Spec	Measurement/Type
Budget	Unlimited
Use case	City/country side driving only. Almost no potholes, long straight lines.
Bike's future top speed (Theoretical)	50 mph (80 kmh)
Bike's current top speed	31 mph (50 kmh)
Bike type	Fat bike 20"x4"
Wheel size	20" (22" effective size)
Wheel/Tire width	4" (102mm)
Original fork brand (Model unknown)	Exsho
Fork type	Triple tree / Double crown / Dual crown
Fork travel	100mm
Fork offset / rake	42mm
Head tube length	6.7" (170mm)
Axle to crown (Derivative measurement)	250mm
Dropout type	Vertical dropout
Dropout width of original fork	135mm Boost - This can be changed to any other size that fits 4" tires
Front motor?	No
More bike specs	Official website

The reason I want to upgrade is because the original fork is a dropout type.
At 50mph, I don't feel it's wise/safe to rely on such when hitting a bump. Think a through axle is a must.

The reason why I'm making this post is, I've looked at the offers from commonly spoken of brands like DVO, BOS, Manitou, Rockshox, Fox, Marzocchi and Suntour, and didn't spot any Triple Tree 100mm travel compatible with 4" wide tire fork.

I've taken a look at other threads within the forum:
1 - References that a 26" fork will give a weird angle to the bike
2 - Recent reference to not use 26" forks
3 - Old thread from 2011
4 - Recent thread of a similar bike
5 - Geometry analysis

My questions are:
• Should I upgrade my current fork at all? Am I exaggerating my fear of dropout type at 50mph?
• Anybody know a fork that meets all my listed requirements?
• What parameter should I sacrifice to obtain a compliant fork for my bike? I've been looking exclusively at Triple Tree types for added rigidity and stability at speed, 80 to 120mm in travel. Can I, for instances, increase my offset? Go onto another lesser known brand? Motorcycle fork?!
• Would Exsho be a good bet to buy from, if all other major brands fail to deliver? They seem to have offers within my requirements, but I'm looking for absolute best.

Any help will be highly appreciated. Build thread to come soon™

 

[99t4]

• Should I upgrade my current fork at all? Am I exaggerating my fear of dropout type at 50mph?

Hard to say.

I did look at the sales/marketing page you linked. There might be other failures from 50MPH riding that happen first? For example: Those fat tires-- what is their speed rating?

Sorry, I get cynical when I see nonsense specs like this:

"Recommended rider height​

5'7" - 6'11"

Followed immediately by:

"Seat height​

32.5" Unadjustable MOPED Saddle"

And:

"Bike gradeability​

20° for dry dirt roads with throttle only, or up to 40° with pedal"

Sorry, calling BS on that one!

And:

"1,000 Lbs Rear Suspension​

High-performance rear suspension can absorb up to 1000 pounds of vibration energy, providing protection for long-distance outdoor cycling"

What does this even mean? "1000 pounds of vibration energy???"

Sorry, I didn't set out to bash your ride, but did want to caution you that there may be other weak points that 50 MPH riding will cause to surface. Beyond or in addition to the QR dropout front fork.

 

[Residents evil]

I've ridden the bike for 5000 miles (8050 km) at 31 mph and it has shown no signs for concern. After seeing the stories of Super73's frames cracking, I constantly verified my frame and looked for issues, nothing found so far.

The theoretical top speed of 50 mph is a buffer I'll have but rarely want to tap into. I will likely cruise a bit above my current top speed, at around 37 mph, and that's it.

The concern is valid and I share it, this is exactly why I'm upgrading everything I realistically can. The tires and brakes were the first things I swapped, had little over 200 miles on the bike. Magura MT7s and Schwabe Super Moto X. I'm looking into even better brakes and moped tires (Shinko SR567 for example, still gotta finalize my research here).

I also really dislike those marketing write ups, only linked it to provide extra measurements and a look into the frame, which is basically the only thing I trust on this bike, feels and looks sturdy (hoping it is sturdy in the long run, no way of truly knowing...)
If it ends up failing, I'll rely on my motorcycle casual looking gear and non casual looking ECE 22.06 helmet to soften the slide.

The purpose of the post may be to get suggestions for brands or specific models of compliant 20x4" forks with the specs in OP, but any other bashing and recommendations are welcome, I'll specifically ask for criticism in my upcoming build thread.

 

[2old]

RST used to make an all steel fork (which I considered for a dual motor system) but I don't know whether it's still available or in 20". That's the direction I would consider.

 

[2old]

Also, just saw an ad for a supposed 60 mph bike that uses a dual crown 20" fork from TRAMA; might be worth a look.

 

[Residents evil]

Also, just saw an ad for a supposed 60 mph bike that uses a dual crown 20" fork from TRAMA; might be worth a look.

Appreciate the suggestions. Took a look at TRAMA but their offers differ in some non negotiable aspects (Smaller offset, shorter travel), but I'll keep in mind their D4T-135 and FAT34D-20ТA models. RST has the Guide DC model, offset is 56mm which would increase my wheelbase, correct? I'm afraid of changing the geometry with such a change, even though it would be theoretically beneficial to increase wheelbase.

Meanwhile, I'll send an email to Exsho asking for their suggestion on an alternative fork. Their website is rather polished for what I was expecting and they seem to have higher end offers that I should consider. Thanks for all your input : )

 

[lnanek]

I put a 26" front wheel on my Ariel Rider X-class instead of 20" and love the geometry change, personally. Also put a rigid carbon MTB fork with much higher axle to crown on my Trek 5000 road bike and love the change there too.

Less toe overlap and higher bottom bracket so less scraping. Steering is much more swoopy than twitchy, which is what I like. Allowed a much fatter, more comfy tire there too.

I suppose eventually geometry changes might lead to wheel flop or the axis of steering might creep in front of the front tire's contact patch hurting stability, but I've yet to encounter those situations.

 

[2old]

Looks like you're "expanding" in the mullet direction. My bike(s) seem to improve by fattening the front too.

 

[Residents evil]

I put a 26" front wheel on my Ariel Rider X-class instead of 20" and love the geometry change, personally. Also put a rigid carbon MTB fork with much higher axle to crown on my Trek 5000 road bike and love the change there too.

Less toe overlap and higher bottom bracket so less scraping. Steering is much more swoopy than twitchy, which is what I like. Allowed a much fatter, more comfy tire there too.

I suppose eventually geometry changes might lead to wheel flop or the axis of steering might creep in front of the front tire's contact patch hurting stability, but I've yet to encounter those situations.

I appreciate the suggestion but I don't want to do it.
My build is stupid (Top speed objectives and all that it entails to achieve it) all because I want to keep the frame and style of the bike. In my case, I'm compromising on things to achieve the overall looks. A bigger front wheel would ruin the style I'm aiming for.

I've studied Exsho's offers, they're selling forks for about 180$ (Base price) and they offer a very extensive set of customization options for their models (Steerer length, type, dropout type and dimensions, travel, preload, lockouts, colors, etc). I need to disassemble my bike to confirm some measurements (Steerer length and type) and then will (try to) order a fork from Exsho, and hope for the best.

The price is ludicrously cheap compared to what I was expecting from renowned brands catalogs. It irks me that I can't pay more for a renowned brand for theoretical extra reliability and thus peace of mind...

 

[bananu7]

At 50mph, I don't feel it's wise/safe to rely on such when hitting a bump.

At 50mph, fatbike tyres aren't safe either.

EDIT: just noticed you mentioned planning a switch to moped tyres. That is a very good idea, but will likely require new rims as well.