Front suspension forks question

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tmho   100 W

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Front suspension forks question

Post by tmho » Aug 14 2019 11:20am

I need a front suspension forks for one of my bikes. I saw a post selling one which I would like to buy. But from its photos, I found that there is a place that it is different from the front suspension forks of my other bikes. The difference is the angle of the drop out. Mine are parallel to the vertical line of the forks, but the one for sale is at an angle.
forks for sale.jpg
forks for sale
forks for sale.jpg (32.83 KiB) Viewed 468 times
IMG_3071.JPG
my front suspension forks
IMG_3071.JPG (319.2 KiB) Viewed 468 times
It seems to me that it is not that good because the front wheel may have a higher chance of coming out. Am I correct? Or am I just ignorance? Will it be suitable for use in an ebike?

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Re: Front suspension forks question

Post by markz » Aug 14 2019 11:29am

Dropout could have been bent.

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E-HP   10 kW

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Re: Front suspension forks question

Post by E-HP » Aug 14 2019 11:42am

tmho wrote:
Aug 14 2019 11:20am
It seems to me that it is not that good because the front wheel may have a higher chance of coming out. Am I correct? Or am I just ignorance? Will it be suitable for use in an ebike?
If you're not using a powered hub, I wouldn't worry about it. That's why the add the lawyer lips to the dropout, to keep the wheel from coming off if you don't tighten down the quick release.

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Re: Front suspension forks question

Post by john61ct » Aug 14 2019 1:08pm


E-HP wrote: That's why the add the lawyer lips to the dropout
Sorry, translation please?


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Re: Front suspension forks question

Post by john61ct » Aug 14 2019 1:10pm

What is the best fork / dropout configuration for a powerful front hub motor?

Are suspension forks stronger or weaker for that purpose than most steel-frame non-suspension forks?

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E-HP   10 kW

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Re: Front suspension forks question

Post by E-HP » Aug 14 2019 1:18pm

john61ct wrote:
Aug 14 2019 1:08pm
E-HP wrote: That's why the add the lawyer lips to the dropout
Sorry, translation please?
There's a lip on the outer side of the fork ends that capture the quick release, even when unlatched. They call them Lawyer lips, because they were added to protect the companies from being sued by riders who don't know to latch their quick releases. Sometimes they're just little tabs at the bottom of the fork, and sometimes they go all the way around the circumference of the axle.

Also, supposedly the angled fork end is better than vertical during braking:

Image

Image

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tmho   100 W

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Re: Front suspension forks question

Post by tmho » Aug 14 2019 1:41pm

E-HP wrote:
Aug 14 2019 1:18pm
john61ct wrote:
Aug 14 2019 1:08pm
E-HP wrote: That's why the add the lawyer lips to the dropout
Sorry, translation please?
There's a lip on the outer side of the fork ends that capture the quick release, even when unlatched. They call them Lawyer lips, because they were added to protect the companies from being sued by riders who don't know to latch their quick releases. Sometimes they're just little tabs at the bottom of the fork, and sometimes they go all the way around the circumference of the axle.

Also, supposedly the angled fork end is better than vertical during braking:

Image

Image
Thank you for your explanation.
I am using a rear hub motor or mid drive motor. Therefore, it should be good to use that angled drop out forks. If I misunderstand your idea, please advise.

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neptronix   100 GW

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Re: Front suspension forks question

Post by neptronix » Aug 14 2019 1:57pm

john61ct wrote:
Aug 14 2019 1:10pm
What is the best fork / dropout configuration for a powerful front hub motor?

Are suspension forks stronger or weaker for that purpose than most steel-frame non-suspension forks?
Suspension forks are weaker because of the materials they're made from. I wouldn't run a motor over 250w on one. dropouts snapping ( even with torque arms ) is a common thing at high power, and being sent flying forwards when you lose your rear wheel is second most dangerous way to crash an upright bicycle.

The front end of the bike also has dramatically less traction than the rear.

I don't recommend front motors at all unless you have no choice and are willing to limit the power and/or go with a solid front fork.
Efficiency is everything :bolt:

My first major build: 1.6kW 8T MAC motor on a Trek 4500.
The new all-arounder: Leafmotor 1500w @ 4kW on a Turner O2 full suspension.
The monster scooter: 20" eZee on a Cannondale Semi Recumbent.
Whipper-snapper: ? on a lightweight BikeE Semi Recumbent

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Re: Front suspension forks question

Post by john61ct » Aug 14 2019 2:19pm

Solid front fork it is then.

Where can one obtain these?

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Re: Front suspension forks question

Post by john61ct » Aug 14 2019 2:21pm


E-HP wrote:There's a lip on the outer side of the fork ends that capture the quick release, even when unlatched.

Also, supposedly the angled fork end is better than vertical during braking
Excellent ELI5, thanks!


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Re: Front suspension forks question

Post by neptronix » Aug 14 2019 3:44pm

john61ct wrote:
Aug 14 2019 2:19pm
Solid front fork it is then.

Where can one obtain these?
Are you sure?
What kind of power will you be pushing and what speeds do you want to go?
Efficiency is everything :bolt:

My first major build: 1.6kW 8T MAC motor on a Trek 4500.
The new all-arounder: Leafmotor 1500w @ 4kW on a Turner O2 full suspension.
The monster scooter: 20" eZee on a Cannondale Semi Recumbent.
Whipper-snapper: ? on a lightweight BikeE Semi Recumbent

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MadRhino   100 GW

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Re: Front suspension forks question

Post by MadRhino » Aug 14 2019 4:09pm

Forks with open dropouts are from the last century. Doesn’t mean it is not good, only that it should be cheap. I find 100$ would be fair, if it is in working order. I see nothing wrong with the dropout design and placement, it was common then. Today, the steer angle is in the frame design, and forks are optimised for lighter weight.
Make it fool-proof, and I will make a better fool.
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Re: Front suspension forks question

Post by flat tire » Aug 14 2019 5:01pm

I agree. Bikes with any speed or power should be using a beefed up fork with a thru axle mount. As the Rhino noted that's how all the high end MTB suspension has come for years.

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Re: Front suspension forks question

Post by neptronix » Aug 14 2019 5:23pm

Not many thru axle mount motors out there. 14mm shaft is plenty strong with torque arms, unless you're pushing tons of power, which i wouldn't be doing in the first place with a front fork at all.
Efficiency is everything :bolt:

My first major build: 1.6kW 8T MAC motor on a Trek 4500.
The new all-arounder: Leafmotor 1500w @ 4kW on a Turner O2 full suspension.
The monster scooter: 20" eZee on a Cannondale Semi Recumbent.
Whipper-snapper: ? on a lightweight BikeE Semi Recumbent

markz   100 GW

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Re: Front suspension forks question

Post by markz » Aug 14 2019 5:59pm

Rigid fork, but be sure its steel.
No more then 750W, 36V 20A maybe 25A. Mines 36V 26A and its fine even with one TA, my unique TA that is ;)
Then add your own torque arms by heading over the Homeless Despot for some 1.5"-2" x 1/4" x 4' steel, get out the ole angle grinder and make your own super strong torque arms!

No need to look good with these....
https://www.ebikes.ca/shop/electric-bic ... m-311.html

more like look cool and sleak with something like this....
Not the best picture I got, but you get the idea. I have a front 750W geared motor on a CCM that I did the exact same thing too.
Install two torque arms, one on either side.
torque arms.jpg
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torque arms1.jpg
torque arms1.jpg (108.1 KiB) Viewed 393 times

john61ct   100 kW

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Re: Front suspension forks question

Post by john61ct » Aug 14 2019 8:24pm


neptronix wrote:What kind of power will you be pushing and what speeds do you want to go?
As much power as I can figure out how to do safely.

No need for much speed, really after torque more, heavy cargo / tandem, help getting up steep long hills.

And drag braking regen on long descents, supplementary to the actual stopping brakes.


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Re: Front suspension forks question

Post by john61ct » Aug 14 2019 8:26pm

So, forget front suspension?

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neptronix   100 GW

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Re: Front suspension forks question

Post by neptronix » Aug 14 2019 8:49pm

You want a rear motor. Because you're going to gravitate towards 1500W-2000W if you have that application. That will require a larger motor that will induce a funny steering feeling into the front end. It will also cause you traction issues unless you use a super wide tire to compensate for the fact that only ~25% of the vehicle's weight sits on that front tire.

Trust me, putting it in the rear wheel is loads better.
Efficiency is everything :bolt:

My first major build: 1.6kW 8T MAC motor on a Trek 4500.
The new all-arounder: Leafmotor 1500w @ 4kW on a Turner O2 full suspension.
The monster scooter: 20" eZee on a Cannondale Semi Recumbent.
Whipper-snapper: ? on a lightweight BikeE Semi Recumbent

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Re: Front suspension forks question

Post by sleepy_tired » Aug 14 2019 10:16pm

I have a 1000w yescomusa hub motor on a solid front fork.

It's good once you are moving.. like over 5mph it'll pull you along no problem. But if you are in the grass or stopped on a hill then there is no traction to get you moving. Unless I pedal hard the motor wouldn't be able to get me out of my own driveway.

My driveway is a short, somewhat steep climb, from my house to the neighborhood road. It's concrete and even if it's 100% dry and sunny outside the motor generates enough torque that it'll just sit an spin the front wheel and not move me anywhere. If I get up and out of the seat and lean on the front bars I can get enough weight on it that it'll move properly...

I use the bike mostly for pedal-assist and only use the full 1300 watts to drag me up big hills when I am already moving fast. Moving around at slow speeds or from a stop at full power is pretty hopeless due to the lack of traction.

If I had to haul something big on the rear or tried to pull a big trailer or something like that then it wouldn't be very good at all. For a heavy cargo bike or hauler or something like that then I would 100% go rear motor. No question about it. It's a no brainer.


The ideal setup in my mind for a bike that was just a pure brute and could be used as essentially a low-speed small pickup would be something with a steel frame and a big 45mm hub motor. 20 inch rear wheel if I could do it. Big tire, lots of amps, but not a whole lot of top speed.

https://www.ebikes.ca/tools/simulator.h ... 170&hp=100

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MadRhino   100 GW

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Re: Front suspension forks question

Post by MadRhino » Aug 14 2019 10:31pm

Of course, rear motor. Front motors are not good for a suspension fork. You can build it safe, but the fork won’t work good anymore. Some fork can be custom tuned to work with the weight of a small motor, but the performance of those motors doesn’t justify the expanse.

So, front build are ideally rigid fork, slow or moderate speed, on fair surface. Sport or performance are rear build domain, because hard acceleration unloads the front and fast riding requires light steering with proper suspension.
Make it fool-proof, and I will make a better fool.
Current bikes
Street: https://s20.postimg.org/ewrvugywt/Session_04_2015.jpg
Dirt: https://s20.postimg.org/lbqwr55ml/IMG_0157.jpg

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Re: Front suspension forks question

Post by john61ct » Aug 14 2019 11:30pm

I did not say I would not have other motors.

This thread is about front forks, and rather than telling me what I want, I'd greatly appreciate help with that topic, and specific questions answered.

Please.

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Re: Front suspension forks question

Post by john61ct » Aug 14 2019 11:35pm

I figure with an extra long custom frame there's a lot of flexibility in how weight is distributed.

Yes fat tires are likely.

I was not planning on the front hub handling the from-stopped startup load.
sleepy_tired wrote:I use the bike mostly for pedal-assist and only use the full 1300 watts to drag me up big hills when I am already moving fast.
Exactly, also drag braking with regen for long descents

Thanks

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Re: Front suspension forks question

Post by john61ct » Aug 14 2019 11:40pm

MadRhino wrote:So, front build are ideally rigid fork, slow or moderate speed, on fair surface.
Thanks.

Yes "rigid" is a quality, strong of course, but more specifically opposite of flexible. So steel is the only appropriate material, right? presumably thick walled tubing if not ?solid? as suggested.

not carbon?

super powerful braking is a must as well

I'm collecting ideas from 60-70's Columbia tandem frames, if not the bikes themselves.

Does that evoke more specifics for an appropriate fork design for safety with a powerful hub motor?

Is there any chance the stock one would do, perhaps with reinforcing?

Looks are not a priority.

And through-axles better than any type of dropout for quick-release?

Very robust torque arms




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neptronix   100 GW

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Re: Front suspension forks question

Post by neptronix » Aug 15 2019 1:00am

Torque makes twist, which is your problem. You are asking 2 tubes to do the work of 4. You will probably have torque steer at the torque you need. A front motor is a very bad option for your situation.
Efficiency is everything :bolt:

My first major build: 1.6kW 8T MAC motor on a Trek 4500.
The new all-arounder: Leafmotor 1500w @ 4kW on a Turner O2 full suspension.
The monster scooter: 20" eZee on a Cannondale Semi Recumbent.
Whipper-snapper: ? on a lightweight BikeE Semi Recumbent

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Re: Front suspension forks question

Post by neptronix » Aug 15 2019 1:02am

Of you want strong braking, then a rear DD with regen is the ticket. it can slow you down better than any mechanical brake. I'd absolutely not run high power regen on the front though as you're liable to be thrown off forwards.
Efficiency is everything :bolt:

My first major build: 1.6kW 8T MAC motor on a Trek 4500.
The new all-arounder: Leafmotor 1500w @ 4kW on a Turner O2 full suspension.
The monster scooter: 20" eZee on a Cannondale Semi Recumbent.
Whipper-snapper: ? on a lightweight BikeE Semi Recumbent

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