Hi, looking to maybe put a 51mm offset fork onto a new full suss frame designed for 42mm offset - what's the chances noticing any difference in offset by 9mm ?
Im thinking not much ?
This must be the most (un)popular question on here at the moment!
It’s not a big enough difference to justify buying a new fork with shorter offset.
First, I just don't believe that frames are "designed" around a specific offset, that's pretty much marketing BS.
Second, having switched between different offsets half an year ago, I can confirm the difference to be nothing more than a nearly imperceptible "there's something slightly different here" that you totally forget 2min later
I keep saying it (this is the third time now) have you run the 42mm fork on the frame before? if not you will notice absolutely no difference as there is no difference to notice.
the fact fork manufacturers have different offsets in the same fork size for these reduced offset forks, but not a unified one like 51 makes me fully believe its marketing BS to sell more bikes.
Plus i run a 51 on a bike designed (apparently) for a "40 something depending on manufacturer" fork and its ace, i haven't crashed, died as a result and the bike hasn't caught fire.
Nope not run it - I have a 51mm fork on an existing bike that Im considering stripping all the components off of to use on a new frame that runs a 42mm offset. So its basically the opposite of what a lot of other riders are querying / looking to do.
Of course frames are designed with a particular offset - the marketing BS is wether it then makes any different to a frame designed with a different but almost the same i.e. less than 10mm offset.
“First, I just don’t believe that frames are “designed” around a specific offset, that’s pretty much marketing BS.”
If you’re designing a frame you are going to try to optimise the handling around a specific offset - the change in trail and thus steering feel is more than you get from changing the head angle by a full degree. If you don’t nail that offset down, how are you going to make all the frame angle and dimension decisions?
But I don’t think that stops you using the other offset, the way it changes the handling will remain the same.
“Second, having switched between different offsets half an year ago, I can confirm the difference to be nothing more than a nearly imperceptible “there’s something slightly different here” that you totally forget 2min later”
I think you overestimate how everyone else is like you. Some riders notice things, others don’t. Sounds like you’re nearer the latter camp. I’m very much in the former - as I don’t design or race bikes for a living it’s more annoying than it is useful.
@chiefgrooveguru ,
I'm obviously not implying that frames are designed ignoring offsets, it's not that a hypothetical 100 offset fork would work. But in reality the offset differences we get (like 51mm vs 44mm) are very small in the grand scheme of things to actually lead any major design decision in the frames. They obviously include an offset number on the CAD files, just like they include a fork A2C number. But lets not forget that, say, a 160mm fork frame is often built from factory with an A2C fork that can go from 567mm (Fox 36/Z1) to 572mm (Lyrik) or even more and no one bats an eye in that case.
How deep a fork rides into its travel will often have more impact overall than all these numbers.
One more thing, I think people greatly overthink and overblow small geometry differences while ignoring the real world manufacturing tolerances of frames. Things like head angles can have a 0,5º tolerance, and still people waste time talking about a 64.5º vs 65º HA. Same goes for reach, etc etc
Also, about about noticing the differences or not, sure, I can't judge what other feel, but I know I'm not alone on this one, even EWS pros and frame designers have shared the same position
But lets not forget that, say, a 160mm fork frame
And also that a lot of frames can be run with various length forks (as stated by frame manufacturer).
There is also the point of whether it is better or worse. The frame manufacturer may have based around 51 but you may prefer 44 and vice versa.
I am definitely in the "can feel the difference for first 2 minutes then it doesn't matter" camp, although while it is fresh in mind after just swapping I could probably say which I prefer but the preference is so marginal that it again doesn't really matter.
I recently swapped out a 42mm offset 140mm travel Lyrik for a 37mm offset 140mm Pike. The only difference I’ve noticed is the front end pops up easier due to the lighter fork (and lighter wheel as well). Can’t say I’ve noticed a huge difference to steering or stability.
I’m going to be swapping the forks back over again shortly as I’ve now serviced the Lyrik so see if I notice the difference there. I’ve got a feeling the Pike had a quicker rebound setting than the Lyrik which might have added to the poppier feeling - so I’m probably going to speed up the rebound on the Lyrik.
Things you will notice; fork weight, fork pressure, fork rebound, fork axle-to-crown
Things you will not notice; fork offset
“But in reality the offset differences we get (like 51mm vs 44mm) are very small in the grand scheme of things to actually lead any major design decision in the frames.”
I don’t know what else to say other than work out the trigonometry for yourself. A 51mm to 44mm offset change is bigger than a 1 deg head angle change in steering feel. To get that big a change in trail from a change in fork A2C you need to get a fork that’s 25mm longer.
“ Things like head angles can have a 0,5º tolerance, and still people waste time talking about a 64.5º vs 65º HA. Same goes for reach, etc etc”
Those manufacturing tolerances don’t mean you can’t feel the difference. Some can’t but I certainly can. And it doesn’t mean that a bike won’t ride better for someone who can’t quantify what’s different.
Humans are incredibly sensitive yet adaptable organic machines. We can feel the tiniest changes in all sorts of things but we can also adapt very well to less than ideal things.
That adaptation is brilliant. But if you have a zero cost choice to make then you might as well choose the thing which minimises the adaptative compensation required.
“ Things you will notice; fork weight, fork pressure, fork rebound, fork axle-to-crown
Things you will not notice; fork offset”
Sorry but if you think fork weight changes are more obvious when riding then offset changes then you’re deluded.
Seems that everyone is deluded except you, have a think about that.
And when would you notice, 1mm, 2mm, 3mm?
I would say it makes literally bugger all difference.
I have had 2 forks, 51mm & 44mm offset, otherwise identical. At the time, I couldn't tell which was on which bike, and then swapping them about, lost track of which was on which.
Reflected in various back to back reviews - supposedly minute differences that are barely perceivable at best.
So no, I wouldn't buy a new fork just for that reason. I'd probably buy a shorter offset fork if I needed one anyway, just for the sake of 'fashion' when I want to sell it again, but that would be the only reason.
Certainly a noticeable difference to me. Prefer shorter offsets personally, but have a 51mm Pike on a 65 HA 29er hardtail that was specced with a 44mm. Preferred the handling with the shorter offset RS 35, but the performance improvement of the Pike outweighs the lighter/less stable steering.
I remember asking Pace about this as their bike is "designed around a shorter offset" and using a 51mm offset fork on the Rc529
this is their initial reply:
"That offset will be fine, it may just make the trail a bit longer but nothing noticeable."
Followed by a further clarification
"Offset on the new Rockshox is 42mm whereas Fox is 44mm on our 29ers. Either of those would work well with a Pace bike. So if you have longer offset it will make the trail shorter. It will feel a bit more twitchy or fall into corners abit more easily and also on straight lines it is not quite as stable. Now it will work, and some people may not even notice but in truth it would perform better with a 42mm offset (but it isn't the end of the World)."
“Offset on the new Rockshox is 42mm whereas Fox is 44mm on our 29ers. Either of those would work well with a Pace bike. So if you have longer offset it will make the trail shorter. It will feel a bit more twitchy or fall into corners abit more easily and also on straight lines it is not quite as stable. Now it will work, and some people may not even notice but in truth it would perform better with a 42mm offset (but it isn’t the end of the World).”
Forks flex more than 2mm fore and aft. Bushing slop, even.
I'm with Chief on this topic. Some can tell, some can't and it's about zero to to with riding ability. I reckon I could *probably* pick the 44mm from the 51mm if the bike was short travel and both forks were set up perfectly as comparisons. I'd have a tenner bet on it for fun, that sort of confidence. Easier on a HT than a FS though. On a rigid frame and fork I'd raise that bet a long way and I've tried plenty of rigid fork offset variations on the same frame in recent years. But 44mm vs 42mm? No chance.
If you think 51mm to 44mm makes no odds you're not wrong and it's likely to be a benefit to your riding ability to not be aware of it. You should also agree that a degree on the HTA makes no odds to you either, to be consistent.
@chiefgrooveguru , I'd say you're being a bit hyperbolic on your interpretation of my comments, but might be my impression only.
Myself said that I do notice it, but only for a very short time. No doubt many are way more sensitive than I am. I'm nonetheless curious to know if those claiming to detect the difference in a major way would indeed be able to do so in a real life blind test. The power of suggestion is great, that I know for sure.
People so often look at bikes strictly through the geometry table. We must not ignore all the cumulative differences made by tolerances, tyre size, tyre pressure, tyre wear, fork sag, fork riding height, shock sag and riding height, etc etc. I remember reading a reviewer at an online publication commenting on how he noticed a 5mm difference in reach. Sorry, but that's BS
“ I remember reading a reviewer at an online publication commenting on how he noticed a 5mm difference in reach. Sorry, but that’s BS”
Neko Mulally just got a new custom WC DH frame which is 10mm longer in reach than last year’s. And he said “The longer reach makes a big difference... ...it’s crazy how much difference that extra 10mm makes”. He was on Gwin’s spare frame last year, hence it was smaller!
If 10mm makes a big difference, how is 5mm impossible to detect?
What I keep saying OVER AND OVER AGAIN is that just because you think it doesn’t matter to you, doesn’t mean others don’t notice and find a small change to be both significant and beneficial.
“ Myself said that I do notice it, but only for a very short time.”
So you do notice but you adapt. That’s what we do! Same reason we can ride with suspension that needs servicing, worn out tyres, wrong tyre pressures, badly set up bikes, etc. Now most of us ride flats I enjoy swapping bikes on group rides (well, when they were allowed!) and being on a bike that’s set up wrong for me doesn’t stop me enjoying riding it.
“ People so often look at bikes strictly through the geometry table. We must not ignore all the cumulative differences made by tolerances, tyre size, tyre pressure, tyre wear, fork sag, fork riding height, shock sag and riding height, etc etc.”
I don’t. But it’s a right pain when something isn’t feeling right - but I’m usually correct and something is up. I’ll notice tyre pressure being 2psi out or shock or fork sag a few percent off... If I was (a lot) quicker I’d be a great development rider!
I don’t think anyone needs to spend money to change a great fork for a shorter offset one but that’s different to shorter offset being beneficial.
Nope not run it – I have a 51mm fork on an existing bike that Im considering stripping all the components off of to use on a new frame that runs a 42mm offset. So its basically the opposite of what a lot of other riders are querying / looking to do.
I did exactly this when swapping parts to a 2020 Orange Stage 5. The only thing I noticed was how slack it was compared to my old bike. I got used to it after a ride or two and love it now.
If shorter offset slows the steering I defo do not want shorter, it's not quick as it is!
When I went from normal Pikes to G2 34s I was pretty impressed by the difference in feel from the offset change. I was less impressed when I found out that actually the offset was the same and it was some other bloody thing I was feeling and giving credit to the offset.
Not saying that it doesn't make a difference and definitely not saying that there might be a best or less good option but I would definitely say that with all the other adjustment and sizing and pressures and dials and whatnot, it's just one variable and it can't possibly make or break a bike. At "worst" you end up with something different than what the manufacturer thought was best but then that's what anglesets and suchlike do too.
“At “worst” you end up with something different than what the manufacturer thought was best but then that’s what anglesets and suchlike do too.”
Exactly!
Of my two bikes, one is meant to have a 51mm offset 150mm fork but I have instead fitted a 42mm offset 160mm one; whilst the other has the original fork travel and offset but a -2 deg headset.
Neither as designed but both better for me!
If you think 51mm to 44mm makes no odds you’re not wrong and it’s likely to be a benefit to your riding ability to not be aware of it. You should also agree that a degree on the HTA makes no odds to you either, to be consistent.
This... Lots of this...
If shorter offset slows the steering I defo do not want shorter, it’s not quick as it is!
Ride faster! No... Really! 🤷🏻♂️
Shorter offsets have become more popular again for the increased stability at speed that they create, at the slight expense of turn in speed. Before lockdown got in the way, I was regularly swapping between 2 bikes, one with a 64.5HA and 150mm 44mm offset fork, the other with a 69HA and 120mm 51mm offset fork. Both bikes are distinctly different to ride, and I have enjoyed them both for different reasons. The reality is that you have to put a little more effort into turning the slacker, longer travel bike with the shorter offset fork, but when you consider the Trail figures of 130mm and 88mm respectively, you can understand why it feels quite a bit more stable at speed too.
Fork offset can change the way a bike feels more than people would credit. It is definitely more of a personal preference thing though than a must have one or the other, with my XC bike I was glad it came with a 51mm offset fork as despite being a big proponent of shorter offset forks myself on modern 29er trail bikes, I wanted my XC bike to feel significantly different and a little more conventional in feel.
Both bikes are fun. The XC bike is still way more capable than XC bikes we were riding even just 5 years ago, but obviously it feels a bit livelier and more engaging at slower speeds than my trail bike does. The trail bike comes into its own when the speeds pick up, the trail gets steeper, and concerns for low speed manoeuvrability go out of the window but the confidence to hit a line at speed with 100% confidence becomes significantly more important.
I can feel the difference between offsets. Currently got a selection from 42-51. It's not a big deal and can happily use either, but prefer shorter. Wants to go in a straight line more, less of a floppy/wandery steering feel, find I have to make less steering adjustments mid corner. Slightly better traction. I'd say the slacker the bike and shorter the stem the more benefit from shorter offset.
If you'd have asked me 10 years ago I'd have said the opposite. Back then it was all about making 29er steering as light and quick as a 26. Longer offset did that and also restored some stability lost due to steep head angles and shorter front centres. Not to mention reducing toe overlap, anyone remember that?
Following this thread...
I haven't tried on a mountain bike, but changing fork offsets definitely makes a noticeable and significant difference for me on road bikes.
Ride faster! No… Really! 🤷🏻♂️
Mate, I don’t have the time to get out enough to compare my times, cornering, speed or offset. I ride similar trails and if I beat a segment it makes me smile. I ride as fast as I can or want to.
For the riding I do and am capable of I don’t want slower steering. I would imagine others are in a similar situation.
“For the riding I do and am capable of I don’t want slower steering. I would imagine others are in a similar situation.”
It’s not really slower. It’s heavier but more immediate. Hard to explain. A bit like the feel change you get from slacker head angles along with short stems.
