dirt bike fork on ebike

any chance to fit this fork on vector/qulbix frame? thanks

https://www.minimx.fr/fr/fourche-dirt-bike/494-fourche-alu-730mm-inversee-dirt-bike.html#/produit_additionnel-kit_de_frein_simple_piston_axe_te_pontet_protection

Many factors to account for.

Yes if:

- you can make custom steering gear with upper and lower crowns, or custom headset adapters and use motorcycle handlebar assembly.

- you don't need adjustments and can tune a fork by the means of internal mods.

- you are willing to lace your front wheel to a motorcycle hub, or make custom axle and spacers to fit a bicycle hub.

- you are willing to use their brake, or make a custom brake adapter bracket.

- you are willing to accept the weight penalty.

Also, that 730mm fork is tiny. It's a fork for a mini bike for 5 year olds. They mounting 12" wheels. You could mount it to a Vector style frame, but it's sure going to look funny.

I have that size forks from a pit bike
does it look small ?

MadRhino said:

- you can make custom steering gear with upper and lower crowns, or custom headset adapters and use motorcycle handlebar assembly.
- you don't need adjustments and can tune a fork by the means of internal mods.
- you are willing to lace your front wheel to a motorcycle hub, or make custom axle and spacers to fit a bicycle hub.
- you are willing to use their brake, or make a custom brake adapter bracket.
- you are willing to accept the weight penalty.

Click to expand...

I reckon the weight is the main downside. Pit bike forks are like 3-5x the weight of mtb ones. I nearly died the first time I lifted a set!
The upside is all things pit bike are cheap so if you're going to use pitty forks, again at the expense of extra weight you can also use a moto front wheel and brakes and it'll all bolt straight up. Once you mess around getting the correct size bearings / steerer sorted the whole front end would be cheaper than a single set of mtb forks.

You have to remember that these folks are burning petroleum instead of employing brain cells. These things tend to work only by throwing more and more energy at the equation to make it balance out.

I think you'd be better off using more or less any air sprung fork from more or less any bicycle application. That way, you can probably correct whatever deficiencies you encounter by changing air pressure or oil viscosity.

Disregard my comment if you're intending to nail jumps at 60mph on something that began life as a bicycle. In that case, God help you and release me from liability.

thanks all for replies,

nice bike robo4!

- 730mm its the same size of a DNM fork
- i will use this front brake with motorbike handlebar too for not did custom work
- the weight isnt a problems
- this fork and brake are used for 8-13hp motorbikes, i thinks its good quality for 5-10kw ebikes
- the axe of wheel is 15mm, we can fit a normal 26" bike downhill wheel

sorry i didnt understand this: "you can make custom steering gear with upper and lower crowns"
that means i need did some work for fit the middle crown of fork into the frame of bike?

thanks

frenchkiss said:

sorry i didnt understand this: "you can make custom steering gear with upper and lower crowns"
that means i need did some work for fit the middle crown of fork into the frame of bike?

thanks

Click to expand...

Well in that link, all you got are two tubes which are suppose to replace broken tubes, and you reuse the steering tube and the crown(s) of whatever was on the pitbike fork before.

Yes you will need to do work/fabrication. You will need a welder, and be proficient at welding. Then you need to figure out the bearing races, which bearings you will be using.

It will be better to buy an entire front fork, then deal with the steering tube. Cut, and swap in a bicycle steering tube from a steel fork. Again you will need a welder and know how to weld.

http://www.kijiji.ca/v-motorcycle-parts-accessories/calgary/honda-magna-front-forks-fender-handlebars-vgc/1236528991?enableSearchNavigationFlag=true

Look at that, frocking heavy as shit. Why dont you buy a used bicycle fork, and do as Chalo said.

Here is a steering head image
http://www.triumphrat.net/attachments/speed-triple-forum/58440d1356788213-steering-head-bearing-adjustments-imageuploadedbymo-free1356788214.271930.jpg

Would the head tube be compatible with bike?
Then the bearing issue.

yes a lot heavier than a cycle fork
I actualy had a complete donor pit bike frame I cut the steering head out and made my own tough carbon frame around it so the fork used the original top clamps
mine ended up as 7.2 kw max and I'm happy with it being as heavy as it is (440 x 18650 inside)
wheels are both 19 moto rims

if you are committed to the weight build to handle it
if you want a light bike then build for that

if you are going to purchase items and assemble then go with a proven recipe, what do the other guys use on your frame?
it will be the easiest to use the same even if it is more expensive up front , you will save on the headaches later
there is no reason a down hill bike fork cant handle the weight , but you would probably need a quality set
if I were you I would use the D/H bike fork that's what your frame is made to suit

Yep, it can be pretty simple if you are willing to use the complete motorcycle front end. Then you only need to adapt a headset to fit the motorcycle steering pin to your bike. But, now the weight penalty is huge because all the front end components together ( tire, wheel, disc, caliper, hose, lever, handlebar, stem, crowns...) are much heavier that the biggest of bicycle components. This extra weight will call for more, since you will need a bigger battery to maintain your range. After that, you will not be able to achieve the same performance because of all this weight. Your bike will be slower, it will take longer to brake and accelerate.

If you can get the moto stuff for dirt cheap if not free, and you are going high power then I see it worthwhile.
I honestly looked at doing it weeks ago, thats why this thread peaked my interest. It fell into my theft proof, frocking ugly bicycle image, where the thief wouldn't have a clue what the unknown bicycle was, and therefor would skip it in a nanosecond, for a recognizable bicycle. The idea is still lingering, because I want a bike where I can lock it up on a bike rack at the transit train station, without needing a bicycle lockers at $12/month. Two real options available to me, use of bike locker and a cheap $200 setup (motor/controller and take the expensive battery with me), or a bike rack with quick release mid-drive motor + controller and of course take the battery with me. No one ever pays attention to the bike lockers, I have rarely seen anyone use them, but once I start using it often you never know.

Yes that would work

Just a random FYI. I was on kijiji and found a 21" rim I wanted the spoke nipples from, when I picked up the parts the guy had a set of forks he wanted gone. He said $5 so I grabbed them but don't need them then I remembered this thread. The forks fit the bomber crowns exact fit just 6.5" longer, the guy said they were from a RM250 I think.

Nice!

Just fallowing up on a bad idea that could be fun and will happen someday. These were the trees inertiaproject was selling direct fit onto dirt bike forks you would just want to use forks with disc brake tabs to start and then sort out the spacing.

kneedeep said:

Just fallowing up on a bad idea that could be fun and will happen someday. These were the trees inertiaproject was selling direct fit onto dirt bike forks you would just want to use forks with disc brake tabs to start and then sort out the spacing.

Click to expand...

Nice! I wish I had picked up a set of those trees before he sold out.

My two cents into safety.

Let us be more specific. Shall we


Pit bike forks are from 500mm up to almost 800mm. You can choose length the same as dh forks, 730mm or 750mm.
Prices:
pit bike DNM fork about 300eu - 400eu. 735mm weights 6.28kg to be specific.
Faceace fork is simial in price and weight.

Above two mentioned pit bike forks are not worse in quality compared with DNM8, opposite, they are better for heavy bikes due ability to install pit bike brakes.

So let us add up.

Pit bike fork weighs 6kg
triple clamp 1kg (maybe this is included in the fork weight, can't tell right now)
front wheel 4kg (if you use 17 mc pit bike wheel) / (if bicycle wheel take put 1 or 2 kg)
brakes 1kg (yes, they are not high end but work better than any pricy dh brakes)
and little unforeseen stuff like axle or smth 1kg

Pit bike:
So, pit bike front end - 13kg overall. Probably you can do 11kg or even less if you use bicycle wheel.

Bicycle:
Downhill bicycle front end (fork, tyre, rim brakes) 6kg or 7kg or even 8kg if with mc tyre.

Therefore pit tike front end is not too heavy, especially if you plan to go fast, 70km/h or so.

Bicycle brakes are not sufficient for heavy and fast ebikes. Cheap rotors have not much metal and gets hot fast, some have cooled rotors but hey are still are too thin, brake pads have a small surface, wear out quickly.

In pic you can see pit bike fork.

BTW
This fork in pic is not DNM or Fastace. Maybe its Volt (Version1 - 100eu or Version2 - 200eu) or some cheap analog. Can't tell from view.

MInde

Your front end weight estimation is biased

My commuter front end, including all components: headset, complete Boxxer WC fork with DM stem, wheel with 24X3.0 tire, caliper and rotor, handlebar and both brake levers, switches and throttle, headlight and running lights, (empty) battery bag and mounting brackets... I weighted it all together when I took it off to replace the headset: 15 lbs 7 oz.
OK, all this is expansive, but not the best weight that can be achieved, only close to.

Now weight your pit bike front end and tell me. Or, if you want to compare fork only, mine is 6 lbs 4 oz with crowns and axle. Then you can consider that mine has all settings and tuning options: Sag, preload, low speed compression, high speed compression, rebound control with high/low hit gate, plus 5 pre-settable Mission Control levels.

I am not saying there is no good reason to fit a pit bike fork to an ebike, but sure not performance and safety.

PS. So far, my commuter ebike stopped shorter from 50 mph on dry pavement than any motorcycle, including those equipped with ABS.