Aussie suspension guru builds hybrid double-sprung dirtbike front end

skypig
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Caloundra AU
10/25/2020 3:10pm
After reading the article, I only have one question. What on earth is “techo singey”?
I’m guessing it’s “Technical Single track”.
A narrow, single lane, track requiring technical skills to negotiate.
The dirt bike opposite of “WFO fire road”.

Got to love Australian slang 🤡
10/27/2020 5:03am
dirtwalker wrote:
Oh and i just work out the head angle has been massively changed. Not sure that is the way to do it. I would think you...
Oh and i just work out the head angle has been massively changed. Not sure that is the way to do it. I would think you would keep the original headset bearing where it is. Would be way too twitchy.
ZOBITO wrote:
Hmmmmmmno.
Sure. Rake and trail are not a delicate balance. And factory teams don’t play around with a mm here or there.
Crossup
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10/27/2020 11:18am
Pics of a newly completed front dual suspension conversion on a 2012 KTM350 EXC-F....just recently tested for the first time and it works great...this adds a...
Pics of a newly completed front dual suspension conversion on a 2012 KTM350 EXC-F....just recently tested for the first time and it works great...this adds a whole new level of front suspension compliance and control.






Looks familiar...


3
10/27/2020 1:58pm
Pics of a newly completed front dual suspension conversion on a 2012 KTM350 EXC-F....just recently tested for the first time and it works great...this adds a...
Pics of a newly completed front dual suspension conversion on a 2012 KTM350 EXC-F....just recently tested for the first time and it works great...this adds a whole new level of front suspension compliance and control.






Crossup wrote:
Looks familiar... [img]https://p.vitalmx.com/photos/forums/2020/10/27/456340/s1200_957.jpg[/img]
Looks familiar...


The look is superficial.....how they actually work in comparison is very very different...
4

The Shop

Ingjr1
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10/27/2020 3:04pm
Interesting they would take a KTM without linkage suspension on the rear to try this out.
2
SoCalMX70
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10/27/2020 4:13pm
The thing that bugs eggheads about forks is that the motion that compresses forks is at odds with their plane of movement. Think about it: if...
The thing that bugs eggheads about forks is that the motion that compresses forks is at odds with their plane of movement. Think about it: if you just press rearward on the lowers of a set of forks, all it is doing is driving the legs hard into the seals and flexing the components, not compressing the springs. So we have been on a continual push toward larger fork components with slicker coatings, while never really addressing why they need to be so overbuilt and produce so much stiction.

Another big thing that drives technical-types nuts about fork design is brake-dive: On one had, it doesn't seem sensible to somebody designing bikes/suspension that riders give up half their suspension under deceleration, and that we should have all this pitching of the chassis back and forth. On the other hand, all of us are keenly accustomed to that action, and attempts to build suspension systems that were free of it have resulted in riders that can't keep comfortable with the foreign feel of the chassis.
In regards to front end brake dive, I feel it is necessary for tight corners/inside ruts. That change of geometry is favorable when entering the corner. Then, upon accelerating out of the corner you return to the "normal" (more stable) geometry needed for higher speeds as well as the suspension travel necessary for large bumps and jumps.

I'd also assume there would be less front end traction under braking if you aren't getting maximum weight "over" the front, but perhaps I'm not thinking about it correctly.

Your last sentence makes perfect sense to me. I couldn't imagine entering a corner with my front end feeling like it is "sticking up" or "locked "at full travel.
OG725
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10/27/2020 4:33pm
Crossup wrote:
Looks familiar... [img]https://p.vitalmx.com/photos/forums/2020/10/27/456340/s1200_957.jpg[/img]
Looks familiar...


I’m riding that bike today, minus the girder!

10/27/2020 5:15pm
Anyways...the bike has completed and passed its first round of testing and now is soon to get some experienced pro riders on it to see what they think...stay tuned.


4
cappelmans
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Utrecht NL
10/28/2020 2:57am Edited Date/Time 10/28/2020 2:59am
I imagine something like this happens if BMW decides to build a motocross bike again.

Interesting for sure but I wonder how the different offset of the fork will impact the handling
1
ti473
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10/28/2020 4:45am

9
10/28/2020 9:45am
suspensionsmith, congratulations on a very interesting project ! The combination of classic forks and a Hossack type is something completely new. Have always been wondering if it would be possible to adapt the Hossack triangle to an enduro or cross motorcycle. Even Norman Hossack did not dare do it. (he did it on a bicycle though).

For a good comparison, the ideal would be to compare your prototype with a standard sxf 350 from 2012, and then ask some pro-riders to give their assumption.

A question : would it not be better to use a stronger shock in the hossack triangle then the one you are using now ? (the difference in weight of an MTB bike and an enduro bike is considerable...)
1
Question
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FR
10/28/2020 10:39am
peter1962 wrote:
suspensionsmith, congratulations on a very interesting project ! The combination of classic forks and a Hossack type is something completely new. Have always been wondering if...
suspensionsmith, congratulations on a very interesting project ! The combination of classic forks and a Hossack type is something completely new. Have always been wondering if it would be possible to adapt the Hossack triangle to an enduro or cross motorcycle. Even Norman Hossack did not dare do it. (he did it on a bicycle though).

For a good comparison, the ideal would be to compare your prototype with a standard sxf 350 from 2012, and then ask some pro-riders to give their assumption.

A question : would it not be better to use a stronger shock in the hossack triangle then the one you are using now ? (the difference in weight of an MTB bike and an enduro bike is considerable...)
That may help too regarding a MX use, to help both the shock and the fork to be set up relatively similarly in term of rebound on jump take offs for instance.
BroFoSho
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10/28/2020 11:11am
scootch wrote:
Trust forks were beginning to find their niche in the MTB industry before impacts from covid seemed to shut them down. Pretty cool tech from one...
Trust forks were beginning to find their niche in the MTB industry before impacts from covid seemed to shut them down. Pretty cool tech from one of the greats of mtb suspension design. They used a trailing linkage design were able to nix the weight penalty over traditional forks by using a full carbon chassis. This fork was probably the closest the mtb industry had ever seen to a design that showed the true potential of linkage forks. I never got to ride one but i heard they felt amazing.


A friend has a Trust fork. He's a bigger dude (200 lbs) and said there was so much flex compared to a Fox38 he just got.
I didn't notice a lot of flex, but also only rode it for 5 minutes on relatively flat ground
10/28/2020 3:32pm Edited Date/Time 10/28/2020 4:52pm
peter1962 wrote:
suspensionsmith, congratulations on a very interesting project ! The combination of classic forks and a Hossack type is something completely new. Have always been wondering if...
suspensionsmith, congratulations on a very interesting project ! The combination of classic forks and a Hossack type is something completely new. Have always been wondering if it would be possible to adapt the Hossack triangle to an enduro or cross motorcycle. Even Norman Hossack did not dare do it. (he did it on a bicycle though).

For a good comparison, the ideal would be to compare your prototype with a standard sxf 350 from 2012, and then ask some pro-riders to give their assumption.

A question : would it not be better to use a stronger shock in the hossack triangle then the one you are using now ? (the difference in weight of an MTB bike and an enduro bike is considerable...)
Cheers mate....yes putting a long travel linkage front suspension on a dirtbike that will compete successfully against a stock telefork bike is very difficult for a bunch of reasons...one thing Teleforks are very good at is getting STEERED long travel in a compact simple reliable cost effective way...very hard to beat.
What I realized is that whilst teleforks are good in some ways they are bad in others and a Linkage suspension is also good in some ways and bad in others....so I thought about combining the two but in such a way which keeps their relative strengths but also reduces their relative weaknesses...they become a system working in greater synergy.
I can use the original fork from the bike and so I can get most of the long travel through the telefork but mounting the telefork in a steeper configuration which lessens some of a teleforks weaknesses.
The linkage is of shorter travel which keeps it compact and light and it can be tuned to give a very specific Kinematic profile which then works in harmony with the telefork...the biggest issue with this setup was understanding it and finding that harmonious relationship between the linkage and telefork.
Now this is the really cool part...the two suspension systems combined now give two wheel paths too the front wheel which has never been seen on a dirtbike before......combined they give a wheelpath range of movement which allows the front wheel to move more freely within this range with greater response and sensitivity too the bump forces being put into it...
It gets better....a normal telefork front suspension system will have two main layers of compliance...the first is the front tire...the second is the telefork itself....anything accelerations that gets past them then is felt by the rider.
This dual suspension system adds a third level of compliance through the linkage suspension...the upshot of this is an amazing level of front suspension compliance and control when riding over rough ground.
Every single person who has ridden these bikes has come away very very impressed.
On the subject of the front MTB shock....the issue here is that to keep the linkage front suspension compact enough means a very short compact shock of useful travel....MTB shocks are ideal for this and the latest stuff is very high quality....the Fox DHX2 I am using in the front of the KTM is a Down Hill specific shock designed to take hard abuse...Foxs latest dampers are actually quite heavy as they incorporate some steel internals to make a stronger damper and they are very adjustable with Hi/Lo comp and reb.
The Fox damper in the KTM is also being used with a very low 1.5:1 leverage ratio compared to a quite high ratio of as much as 3:1 found in some DH bikes....consequently I am using a spring rate that would be in the low range when compared too a DH bike....so the shock isnt being overly stressed...tests have shown that it isnt getting overly hot....the other thing is that the telefork is still doing most of the work...its the most active of the two.
4
10/28/2020 3:48pm
We have done some datalogging of the front suspension with some very useful insights.
Here is a data trace showing the two front suspensions working together....the blue trace is the telefork moving over a series of bumps...the pink trace is the secondary suspension also simultaneously moving over the same bumps....notice the two traces are almost the same in frequency just different in amplitude....they are both working in good harmony with each other.
So any accelerations that get past the telefork are then absorbed by the secondary suspension...the level of compliance this gives has to be felt to be believed.


4
10/29/2020 12:08am
scootch wrote:
Trust forks were beginning to find their niche in the MTB industry before impacts from covid seemed to shut them down. Pretty cool tech from one...
Trust forks were beginning to find their niche in the MTB industry before impacts from covid seemed to shut them down. Pretty cool tech from one of the greats of mtb suspension design. They used a trailing linkage design were able to nix the weight penalty over traditional forks by using a full carbon chassis. This fork was probably the closest the mtb industry had ever seen to a design that showed the true potential of linkage forks. I never got to ride one but i heard they felt amazing.


BroFoSho wrote:
A friend has a Trust fork. He's a bigger dude (200 lbs) and said there was so much flex compared to a Fox38 he just got...
A friend has a Trust fork. He's a bigger dude (200 lbs) and said there was so much flex compared to a Fox38 he just got.
I didn't notice a lot of flex, but also only rode it for 5 minutes on relatively flat ground
Heres a MTB that doesnt flex much....dual front suspension downhill bike...another of my prototypes...












5
1
RPM68
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1559
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DFW, TX US
10/31/2020 7:53pm
Cheers mate....yes putting a long travel linkage front suspension on a dirtbike that will compete successfully against a stock telefork bike is very difficult for a...
Cheers mate....yes putting a long travel linkage front suspension on a dirtbike that will compete successfully against a stock telefork bike is very difficult for a bunch of reasons...one thing Teleforks are very good at is getting STEERED long travel in a compact simple reliable cost effective way...very hard to beat.
What I realized is that whilst teleforks are good in some ways they are bad in others and a Linkage suspension is also good in some ways and bad in others....so I thought about combining the two but in such a way which keeps their relative strengths but also reduces their relative weaknesses...they become a system working in greater synergy.
I can use the original fork from the bike and so I can get most of the long travel through the telefork but mounting the telefork in a steeper configuration which lessens some of a teleforks weaknesses.
The linkage is of shorter travel which keeps it compact and light and it can be tuned to give a very specific Kinematic profile which then works in harmony with the telefork...the biggest issue with this setup was understanding it and finding that harmonious relationship between the linkage and telefork.
Now this is the really cool part...the two suspension systems combined now give two wheel paths too the front wheel which has never been seen on a dirtbike before......combined they give a wheelpath range of movement which allows the front wheel to move more freely within this range with greater response and sensitivity too the bump forces being put into it...
It gets better....a normal telefork front suspension system will have two main layers of compliance...the first is the front tire...the second is the telefork itself....anything accelerations that gets past them then is felt by the rider.
This dual suspension system adds a third level of compliance through the linkage suspension...the upshot of this is an amazing level of front suspension compliance and control when riding over rough ground.
Every single person who has ridden these bikes has come away very very impressed.
On the subject of the front MTB shock....the issue here is that to keep the linkage front suspension compact enough means a very short compact shock of useful travel....MTB shocks are ideal for this and the latest stuff is very high quality....the Fox DHX2 I am using in the front of the KTM is a Down Hill specific shock designed to take hard abuse...Foxs latest dampers are actually quite heavy as they incorporate some steel internals to make a stronger damper and they are very adjustable with Hi/Lo comp and reb.
The Fox damper in the KTM is also being used with a very low 1.5:1 leverage ratio compared to a quite high ratio of as much as 3:1 found in some DH bikes....consequently I am using a spring rate that would be in the low range when compared too a DH bike....so the shock isnt being overly stressed...tests have shown that it isnt getting overly hot....the other thing is that the telefork is still doing most of the work...its the most active of the two.
I appreciate you posting that in a manner that suspension illiterate folks can follow. Thanks for posting!
1
10/31/2020 10:36pm
RPM68 wrote:
I appreciate you posting that in a manner that suspension illiterate folks can follow. Thanks for posting!
Pleasure mate...if you need any clarification on anything just ask.
keinz
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Tallinn, Estonia EE
11/2/2020 12:28pm

4
11/7/2020 11:22pm
Since ktm is using the same frame for much of their enduro models (250-300 TPI has the same frame as the 450 four strokes) and also the husqvarna brand, and now Gas Gas, this would mean you only have tot develop one specific bolt-on kit.
Are you considering production in the foreseeable future ?
11/7/2020 11:38pm
peter1962 wrote:
Since ktm is using the same frame for much of their enduro models (250-300 TPI has the same frame as the 450 four strokes) and also...
Since ktm is using the same frame for much of their enduro models (250-300 TPI has the same frame as the 450 four strokes) and also the husqvarna brand, and now Gas Gas, this would mean you only have tot develop one specific bolt-on kit.
Are you considering production in the foreseeable future ?
We are considering such a kit....although not so much bolt on more as weld on as the stock steering head is removed and the pivot points for upper and lower links...shock and steering pivot are welded on....not a major amount of work.

Some good news tho...yesterday we had Geoff Ballard spend a day test riding the bike and he came away very very impressed with the front suspension....from his feedback we are going to make some changes and he is keen to have another ride.
Next week we have Ben Grabham swinging a leg over the bike for his impressions of it....should be interesting....happy days.
Lurk Ing
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192
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Location
AU
11/8/2020 6:31am
peter1962 wrote:
Since ktm is using the same frame for much of their enduro models (250-300 TPI has the same frame as the 450 four strokes) and also...
Since ktm is using the same frame for much of their enduro models (250-300 TPI has the same frame as the 450 four strokes) and also the husqvarna brand, and now Gas Gas, this would mean you only have tot develop one specific bolt-on kit.
Are you considering production in the foreseeable future ?
We are considering such a kit....although not so much bolt on more as weld on as the stock steering head is removed and the pivot points...
We are considering such a kit....although not so much bolt on more as weld on as the stock steering head is removed and the pivot points for upper and lower links...shock and steering pivot are welded on....not a major amount of work.

Some good news tho...yesterday we had Geoff Ballard spend a day test riding the bike and he came away very very impressed with the front suspension....from his feedback we are going to make some changes and he is keen to have another ride.
Next week we have Ben Grabham swinging a leg over the bike for his impressions of it....should be interesting....happy days.
Those guys know testing suspension too. Should be good tangible feedback. Keep going, your definitely on to something. I doubt it's for everyone but who knows if your results are better than traditional tele forks. If it wasn't for guys like you, we'd all still be putting our foot between the forks and the front wheel to stop.
11/9/2020 12:59am
Lurk Ing wrote:
Those guys know testing suspension too. Should be good tangible feedback. Keep going, your definitely on to something. I doubt it's for everyone but who knows...
Those guys know testing suspension too. Should be good tangible feedback. Keep going, your definitely on to something. I doubt it's for everyone but who knows if your results are better than traditional tele forks. If it wasn't for guys like you, we'd all still be putting our foot between the forks and the front wheel to stop.
Cheers mate

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