Ok, quick question guys. Keep it simple please. I beg you!

Which will tend to be more “flip flop” when steering up hill/slowly?

A 46 or 51mm offset?

I went from a 44mm to 51mm on a 100mm XC bike
I could immediately tell there is a difference

Same here.

Prefer it. But then I have a biggish frame.

Can’t comment on 46mm, but picked up a set of 51mm Pikes for a 29er (NS Eccentric Alu Evo) and I found the stem length affected the steering. 35mm felt weird, vague, and flip-floppy especially at low speeds. 50mm feels spot on, more ‘direct’.

@mboy the tricky bit is working out flop (how the front end of the bike sinks when you turn the steering). This is at the root of why bikes are stable in motion, and is a bit diff to work out. But apparently you get that formula I gave up there^^.

@poopscoop – 46mm offset more floppy. It is the slow speed climbing behaviour that I notice with slacker bikes, but I have got used to it.

You should also not forget that bikes are designed as a package, and whilst it might be OK to alter the fork offset by 10% or so and the bike still behave acceptably (as you might if you increased your fork travel a similar amount), if you change it by a much larger amount, the likelihood of it ruining the handling of your bike will increase drastically too!

Totally agree with this ^ For example my bike is designed around a 130 mm travel, 51 mm offset fork, 60 mm stem and 760 mm bars. One reviewer decided to try a more fashionable 44 mm offset fork, shorter stem and wider bars. Result was a mixed bag. He thought the 44 mm offset was better for high speed stability, but more sluggish for tight singeltrack. The shorter stem and wider bars just made the steering too light and twitchy. Standard setup was actually more in line with the bike’s intended usage. But it does show that you can “tune” the feel to your personal taste if you know what affects what. Simply following fashion may or may not work for you.

according to the formula, changing offset will change flop by changing the trail, which is one of the factors. More trail=more flop. The slight head angle change you also get will operate in the same direction. And that is what I understand flop to be as well. The trigonometry is well tricky though.

It’s really the head angle that determines steering flop, although head angle and trail are somewhat inter-related in that changing HA affects the trail (unless you change the offset). Let’s say you had a 90 deg HA and a massive (negative) offset to provide some trail, you still wouldn’t get any steering flop ie wheel camber change with steering. What you would have though is a large scrub radius.

you still wouldn’t get any steering flop ie wheel camber change with steering.

I know what you’re getting at and it’s correct – but (and this is a good geek-out mental 3D topic thread, apologies to the OP for the diversion..) .. to corner any bike would need some lean, and as soon as you lean that 90 deg HTA and negative long offset fork you’d have forces on steering creating what I think would be effectively very similar to ‘flop’, a force turning the bar into the corner direction (but..yeah, sort of irrelevant..)

I know what you’re getting at and it’s correct – but (and this is a good geek-out mental 3D topic thread, apologies to the OP for the diversion..) .. to corner any bike would need some lean, and as soon as you lean that 90 deg HTA and negative long offset fork you’d have forces on steering creating what I think would be effectively very similar to ‘flop’, a force turning the bar into the corner direction (but..yeah, sort of irrelevant..)

Agreed, I was only using this extreme example to demonstrate how trail and head angle differ in terms of their effect on camber change with steering lock. The simplistic way of looking at it is to think of “trail” as providing the steering weight/feel (zero trail would give extremely light steering with no feel) and head angle as providing the stability (slacker head angle more stable). In practice they work together, so if you want maximum stability and a damped steering feel then a slack HA + high trail is the way to go. A shorter fork offset is one way of achieving this aim, especially if you don’t want to go overly slack. If you want a more agile responsive setup, then steeper HA and less trail is required.

There is no right or wrong approach as long as it suits the rider and terrain. My local singletrack (Woburn) is super tight and twisty and fairly technical in parts, though there are few steep descents or high speed sections. So stability is never an issue on a modern trail bike. This terrain suits more agile and compact (basically less fashionable) geometry best.

@moshimonster, at a 90 head angle the change in flop caused by a degree change in head angle (say, to 89) is at its highest. By contrast, at a 45 head angle, the change in flop caused by changing the head angle to 46 will be negligible. All assuming you adjust the fork offset to keep the trail constant in those situations. Trigonometry is fun!!!

@moshimonster, at a 90 head angle the change in flop caused by a degree change in head angle (say, to 89) is at its highest. By contrast, at a 45 head angle, the change in flop caused by changing the head angle to 46 will be negligible. All assuming you adjust the fork offset to keep the trail constant in those situations. Trigonometry is fun!!!

Sure, but there isn’t going to be very much absolute “flop” at 89 deg even if the rate of change per degree of head angle is at its highest in that range. There is moderate change per degree in the realistic head angle range we see and a moderate amount of floppiness!

greyspoke

Member

@poopscoop – 46mm offset more floppy. It is the slow speed climbing behaviour that I notice with slacker bikes, but I have got used to it.

Thanks for the reply mate.

Yeah, on my Jeffsy it is a bit of a handful on slow uphills but as you say, you get used to it. Looked at the form today and it is indeed a 46mm.

Thanks again!

So, is the offset made by the crown steerer unit or the axle mounts on the lowers ? On a Pike ?

“So, is the offset made by the crown steerer unit or the axle mounts on the lowers ? On a Pike ?”

Both!

Both

Thanks…

you get used to it

That’s the bottom line with these things. Most people adapt to what they have and when the change is relatively small it soon gets forgotten in the noise.

Another thing I’ve learnt from pro motorsport is that a lot of things that “feel” different are not necessarily better or worse (as measured on the stopwatch). Things that subjectively “feel” good can actually be slower and vice-versa, or simply make no difference at all. Humans are basically not very objective!

“Thanks…”

I think the offset variations between all the different versions are done at the crown but most of the offset happens at the axle (because pushing the axle out in front of the lower tubes frees up more space for the suspension workings, allowing a lower axle to crown height).

“Thanks…”

I think the offset variations between all the different versions are done at the crown but most of the offset happens at the axle (because pushing the axle out in front of the lower tubes frees up more space for the suspension workings, allowing a lower axle to crown height).

I had seen some CSUs with different offsets, which made me wonder..

I think I have decided to send it (2019 model) back and try find a 2018 model with the same offset… As I assume Whyte knew why they originally speccd it with the shorter offset.

Thanks all !

Yeah, on my Jeffsy it is a bit of a handful on slow uphills but as you say, you get used to it. Looked at the form today and it is indeed a 46mm.

Out of interest, my Helm is a 44 offset from the 46 standard on my Jeffsy and I love it. But it’s also a 150mm vs. the 140 and a coil Vs air as standard so not sure which bit has made the most difference. There’s almost certainly some confirmation bias in the mix too, but it feels much calmer

I think I have decided to send it

That’s the spirit!

Wil wrote a pretty comprehensive feature on fork offset here…

What Is Fork Offset? And Why Does It Matter?