How to measure fork off set?

[Bizkit031]

I have a 2012 Fox Float 29 RL and can't find any info on the Offset of this fork. Also what difference will a longer offset make to your handling.

[Captain Fastbastard Mayhem]

the f29 offset may be different depending on the OEM specs, but generally - the larger the offset, the smaller the trail, and generally, the shorter the trail, the snappier the handling. Swapping my 40mm offset lyrik for a 46mm offset Marzo made the bike handle WAY faster, even though the head angle decreased by about 0.5 degrees and the wheelbase extended (it was a longer fork)

 

Stolen from Pinkbike for a more detailed explanation though...

 

To The Point - Rake and Trail

May 21, 2013

by Matt Wragg  Follow 

   Add to Favorites

Murray Washburn started out racing BMX when he was five. He went to college in Colorado, where they issue you a mountain bike when you hit the state line, at the time when mountain biking was in its infancy. He worked as a shop guy in Colorado for many years, in sales and service, working with racers and wrenching for racers. In 1997 he started working for Cannondale and has held a number of roles since then, including sales representative, race mechanic and product manager technical representative. Today he is the Global Director of Product Marketing, which is the link between Cannondale’s Engineering dept and the outside world. He describes himself as a "supremely unqualified engineer, but someone who loves knowing how stuff works." 


http://lp3.pinkbike.org/p1pb6168857/p1pb6168857.jpg What is a fork-offset?

When you're talking about geometry and handling, there are three things that are interrelated.
First there’s head-angle, which is the angle of the head tube. If you a draw line right through the head 
tube and steerer tube and take that all the way down to the ground, that's your head angle. Then there’s
fork rake, which is the amount the front axle sits off that centre line.For mountain bikes, it can also be 
referred to as fork offset. It's been hovering around 45-50mm of offset.you can gain fork rake either through 
angling the stanchion tubes at the crown, or offsetting the dropouts, but the net result is the same Rake 
and offset together create a measurement which is called trail. This is a measurement where you take 
that head angle line extended to the ground and then you find where the axle is and you draw a line 
vertically down to the line. The difference between where the first line and the second line intersect the 
ground is called trail.

http://ep1.pinkbike.org/p4pb9516905/p4pb9516905.jpg

http://lp3.pinkbike.org/p1pb6168857/p1pb6168857.jpg Why should people care about this?

There is no easy way to think about rake and trail, because if you go too far one way, or too far
the other, the affect flip-flops. From a mountain biking standpoint, the easiest way to think about 
is that head-angle controls and affects high-speed and low-speed stability. Meaning, the more you 
rake it out, the more floppy to one side the bike gets at low-speeds, the more of a handful it is on the
climbs. But,when you're travelling at high speeds, it not only aligns your suspension with the oncoming
impacts, but gives it a really planted, solid feel that makes it hard to maneuver it off line. When people talk 
about slack head-angles, they generally refer to it in relation to 45 to 50mm fork offsets. If you think 
about what the demands are for all-mountain riding, you want a bike that's really stable at speed,
but you also want it to be maneuverable when it gets slow. You look at enduro riding, where they've 
got massive high-speed sections, but they've also got tight hairpin sections, quick little uphills, 
you've got all these different things. The idea would be that you've got a bike that has really nimble 
handling at low speeds, but is rock-solid at high speeds. We've been playing around with different 
head-angles and different fork offsets to achieve that.

http://ep1.pinkbike.org/p4pb9608552/p4pb9608552.jpg

http://lp3.pinkbike.org/p1pb6168857/p1pb6168857.jpg How do you apply this to your bikes than?

The most obvious example is the Trigger 29. We took what is normally 45 to 50mm of offset, and we push it out to 60mm of offset. If you look at the SuperMax axle, you can see that there is a big offset of the dropout there. What that does is allows us to kick the head angle back to a relatively slack, 69 degrees, which if you kept that with a 45-50mmmm rake on a 29er, you would have the most sluggish handling bike in the world. It would be great at high speed, but the second it slowed down it would just be a pig. By kicking the head-angle out and kicking the fork rake out, it does the counter-intuitive thing of reducing the trail.

http://lp3.pinkbike.org/p1pb6168857/p1pb6168857.jpg If this is so vital, why isn't this something we hear more about? 

Most bike manufacturers design around industry standards and creating change within that world is slow and difficult. Suspension manufacturers build forks that are consistent to each other based upon OEM stuff and, like everything in mountain bikes, people accept things as standards and rarely think about them in a different way. Cannondale is a frame and suspension company first and foremost and we have the unique ability to change angles where we see performance improvements.

http://lp3.pinkbike.org/p1pb6168857/p1pb6168857.jpg Doesn't a slack head-angle just mean poor low-speed handling?

If the head-angle was the only factor, the answer would be yes. Thankfully though, this stereotype 
is just that. Handling is one of the things that, up until now, has been holding back longer travel 29’ers.  
At low speed, there is a natural tendency for the big wheels to be sluggish. Frame designers have been 
using steeper head angles to help, but it was at the expense of high-speed stability. That is not a lot 
of fun for a bike that naturally wants to go fast. By adjusting both head angle and trail, you can get a
bike that handles just as incredibly well at high speed as it does at low speed.

http://ep1.pinkbike.org/p4pb9608529/p4pb9608529.jpg

Ben Cruz aboard a Cannondale Jekyll with a prototype SuperMax.

http://lp3.pinkbike.org/p1pb6168857/p1pb6168857.jpg Why don't you just eliminate the trail then to make slack bikes that handle incredibly quickly?

You need trail to offer some stability to the bike. Without it, the front wheel would behave like the wheels on a shopping cart. It is the balance of these subtle ingredients that separates great handling bikes from the rest.

[Bizkit031]

the f29 offset may be different depending on the OEM specs, but generally - the larger the offset, the smaller the trail, and generally, the shorter the trail, the snappier the handling. Swapping my 40mm offset lyrik for a 46mm offset Marzo made the bike handle WAY faster, even though the head angle decreased by about 0.5 degrees and the wheelbase extended (it was a longer fork)

 

Stolen from Pinkbike for a more detailed explanation though...

 

 

To The Point - Rake and Trail

 

 

May 21, 2013

 

 

by Matt Wragg  Follow 

 

   Add to Favorites

 

Murray Washburn started out racing BMX when he was five. He went to college in Colorado, where they issue you a mountain bike when you hit the state line, at the time when mountain biking was in its infancy. He worked as a shop guy in Colorado for many years, in sales and service, working with racers and wrenching for racers. In 1997 he started working for Cannondale and has held a number of roles since then, including sales representative, race mechanic and product manager technical representative. Today he is the Global Director of Product Marketing, which is the link between Cannondale’s Engineering dept and the outside world. He describes himself as a "supremely unqualified engineer, but someone who loves knowing how stuff works." http://lp3.pinkbike.org/p1pb6168857/p1pb6168857.jpg What is a fork-offset?When you're talking about geometry and handling, there are three things that are interrelated.

First there’s head-angle, which is the angle of the head tube. If you a draw line right through the head 

tube and steerer tube and take that all the way down to the ground, that's your head angle. Then there’s

fork rake, which is the amount the front axle sits off that centre line.For mountain bikes, it can also be 

referred to as fork offset. It's been hovering around 45-50mm of offset.you can gain fork rake either through 

angling the stanchion tubes at the crown, or offsetting the dropouts, but the net result is the same Rake 

and offset together create a measurement which is called trail. This is a measurement where you take 

that head angle line extended to the ground and then you find where the axle is and you draw a line 

vertically down to the line. The difference between where the first line and the second line intersect the 

ground is called trail.

 

http://ep1.pinkbike.org/p4pb9516905/p4pb9516905.jpg

http://lp3.pinkbike.org/p1pb6168857/p1pb6168857.jpg Why should people care about this?There is no easy way to think about rake and trail, because if you go too far one way, or too far

the other, the affect flip-flops. From a mountain biking standpoint, the easiest way to think about 

is that head-angle controls and affects high-speed and low-speed stability. Meaning, the more you 

rake it out, the more floppy to one side the bike gets at low-speeds, the more of a handful it is on the

climbs. But,when you're travelling at high speeds, it not only aligns your suspension with the oncoming

impacts, but gives it a really planted, solid feel that makes it hard to maneuver it off line. When people talk 

about slack head-angles, they generally refer to it in relation to 45 to 50mm fork offsets. If you think 

about what the demands are for all-mountain riding, you want a bike that's really stable at speed,

but you also want it to be maneuverable when it gets slow. You look at enduro riding, where they've 

got massive high-speed sections, but they've also got tight hairpin sections, quick little uphills, 

you've got all these different things. The idea would be that you've got a bike that has really nimble 

handling at low speeds, but is rock-solid at high speeds. We've been playing around with different 

head-angles and different fork offsets to achieve that.

http://ep1.pinkbike.org/p4pb9608552/p4pb9608552.jpg

http://lp3.pinkbike.org/p1pb6168857/p1pb6168857.jpg How do you apply this to your bikes than?The most obvious example is the Trigger 29. We took what is normally 45 to 50mm of offset, and we push it out to 60mm of offset. If you look at the SuperMax axle, you can see that there is a big offset of the dropout there. What that does is allows us to kick the head angle back to a relatively slack, 69 degrees, which if you kept that with a 45-50mmmm rake on a 29er, you would have the most sluggish handling bike in the world. It would be great at high speed, but the second it slowed down it would just be a pig. By kicking the head-angle out and kicking the fork rake out, it does the counter-intuitive thing of reducing the trail.

http://lp3.pinkbike.org/p1pb6168857/p1pb6168857.jpg If this is so vital, why isn't this something we hear more about? Most bike manufacturers design around industry standards and creating change within that world is slow and difficult. Suspension manufacturers build forks that are consistent to each other based upon OEM stuff and, like everything in mountain bikes, people accept things as standards and rarely think about them in a different way. Cannondale is a frame and suspension company first and foremost and we have the unique ability to change angles where we see performance improvements.

 

http://lp3.pinkbike.org/p1pb6168857/p1pb6168857.jpg Doesn't a slack head-angle just mean poor low-speed handling?If the head-angle was the only factor, the answer would be yes. Thankfully though, this stereotype 

is just that. Handling is one of the things that, up until now, has been holding back longer travel 29’ers.  

At low speed, there is a natural tendency for the big wheels to be sluggish. Frame designers have been 

using steeper head angles to help, but it was at the expense of high-speed stability. That is not a lot 

of fun for a bike that naturally wants to go fast. By adjusting both head angle and trail, you can get a

bike that handles just as incredibly well at high speed as it does at low speed.

http://ep1.pinkbike.org/p4pb9608529/p4pb9608529.jpg

Ben Cruz aboard a Cannondale Jekyll with a prototype SuperMax.

 

http://lp3.pinkbike.org/p1pb6168857/p1pb6168857.jpg Why don't you just eliminate the trail then to make slack bikes that handle incredibly quickly?You need trail to offer some stability to the bike. Without it, the front wheel would behave like the wheels on a shopping cart. It is the balance of these subtle ingredients that separates great handling bikes from the rest.

Thanks,so both your forks have same travel exept that the offset is different. I wanna get a Pike 140mm travel so do you think I should stay with the same offset or can I change it?

[Captain Fastbastard Mayhem]

Thanks,so both your forks have same travel exept that the offset is different. I wanna get a Pike 140mm travel so do you think I should stay with the same offset or can I change it?

No, the old fork was a 170 and the new 180mm. If the offset was the same it would have made it a bit slower than before due to the slightly longer wheelbase and slacker HA. But the larger offset overcame that and more and so instead of slowing down the handling actually sped up.

 

If yiu are going longer on your fork I would suggest increasing the offset, but not too much cos here is a point of no return

[Captain Fastbastard Mayhem]

To add... Iwan Kemp knows more about this than I do

[Bizkit031]

To add... Iwan Kemp knows more about this than I do

I need to measure my Fox and go from there.