• This topic has 26 replies, 18 voices, and was last updated 1 month ago by argee.
Viewing 27 posts - 1 through 27 (of 27 total)
  • Are Short Offset Forks The New Normal?
  • Premier Icon TheGhost
    Subscriber

    Are Short Offset Forks The New Normal?

    Premier Icon simondbarnes
    Subscriber

    No

    Premier Icon brant
    Subscriber

    Did you not have a Bontrager Racelite with the short offset crown back in the day? Or a Zinn with a short rake fork? If so you would know the downsides.

    Premier Icon AD
    Subscriber

    hehe I’ve still got a Racelite…

    Premier Icon sillyoldman
    Subscriber

    For bigger travel/slacker bikes yes for greater stability in the conditions those bikes should be ridden in, but not for shorter travel woodsy bikes where low speed manoeuvrability is prioritised – bigger offset better for them.

    Premier Icon benpinnick
    Subscriber

    Yes, no, sort of. What happened was forks got longer offsets in fits and starts for no real good reason (46 & 51mm) and then recently when RockShox decided to stop making shorter offsets there was a reaction, and they went way the other way (37 & 42) and I expect to see them creep back towards the middle ground of 40-46 for all but Enduro stuff.

    Premier Icon tmb467
    Subscriber

    Wasn’t the 51mm offset for 29ers more about being able to corner, especially when the head angle was still steep and the travel was short

    Or have I just made that up?

    Premier Icon benpinnick
    Subscriber

    It was because Gary Fisher thought that we needed faster steering bikes.

    Premier Icon sillyoldman
    Subscriber

    Worth bearing in mind that he increased offset at the same time as going to a 69 deg head angle when everyone else was running 71/72 deg head angles, so slack for that era. Wasn’t necessarily about getting faster steering, it was about getting the steering response he wanted without destroying weight distribution like others did. He only copied Jeff Jones anyway who uses 55mm offset which was more blatantly aped by another bendy bike builder in the UK.

    robj20
    Member

    Transition bikes use a short offset from what i can see, does it counteract the slack front end while keeping the longer wheelbase.

    Premier Icon igm
    Subscriber

    Not as I understand it.

    But I’m often wrong.

    Hob Nob
    Member

    I have 2 identical forks, apart from the offset.

    One being 44mm, the other being 51.

    Which one is which & can I tell any difference? Nope.

    Premier Icon mlltt
    Subscriber

    What I wonder is, how much difference would the average rider notice between say 42 & 37mm offset when the frame is designed for 37mm offset?

    I know a few people put off buying frames as it’s recommended 37mm offset and they don’t want to buy new forks

    andyg1966
    Member

    I could tell between 46mm and 51mm offset on an 120mm Trek original Stache 29er. 68.5deg head angle.

    46mm poor at cornering, especially tight uphill.
    51mm really good

    robj20
    Member

    SBG is designed to be used with a fork offset that is shorter than traditionally used per wheel size. The shorter fork offset brings the front axle more rearward and under the rider which further increases front tire traction. This works in unison with the shorter stem length to provide a more direct steering input and dramatically enhances connectivity to what is happening with the front wheel. The shorter offset also brings the front wheel more under the rider which balances the effects of a slacker head angle. Our SBG system creates a longer trail figure than standard, used in a way that eliminates the negative side effects.

    zezaskar
    Member

    The key word in all this offset talk is trail.
    – Big trail feels planted, stable and undisturbed (the steering has a bigger tendency to self correct) feeling, but means you’ll have to corner more like in a motorcycle (leaning in rather than steering) and can feel wallowy and difficult to control at slow steep climbs with corners
    – small trail feels the reverse of above

    Slacker headtube angle increases trail. Shorter offsets increase trail.

    robj20
    Member

    I can’t get my head around why reduced offset increases trail. In my mind it should almost be the opposite of a slacker head angle.

    Reducing the offset skills surely sharpen the steering and bring the front wheel more under the rider.

    Premier Icon Jordan
    Subscriber

    Its very closely related/more or less the same thing as what is known in vehicle engineering as Caster angle. This creates the force that causes your car steering wheel to self centre when you let it go and increases the tendency for a bike to want to go in a straight line i.e. more stability.

    This diagram might help get your head around it.
    trail and head angle

    robj20
    Member

    Yes it does, thanks. So offset does move the wheel backwards but pushes the trail limit backwards. Had angle pushes the trail limit forward.
    Two ways of achieving the same thing.

    So why do Transition that already have relatively slack head angle want to use small offset forks as well.

    Premier Icon Jordan
    Subscriber

    I guess they just want the amount of stability that the particular combination provides.

    So why do Transition that already have relatively slack head angle want to use small offset forks as well.

    Thought I understood this, now I don’t.

    As per Jordans diagram and Zezaskars explanation -> big trail = stability.

    Big slack bike
    good at high speed (lots of trail)
    and steep stuff (wheel way out in front)
    but bad at low speed manourvering (lots of trail, where less would be good)

    Transition come along and go short offset forks and slack angles.
    Good at steep stuff (wheel way out in front)
    good at low speed (not so much trail – probably back to where we were a few years ago with 67-68 degree AM bikes);
    less good at high speed (but did you really need all that stability for railing a blue flow trail anyway?).

    However this from the horses mouth:

    SBG is designed to be used with a fork offset that is shorter than traditionally used per wheel size. The shorter fork offset brings the front axle more rearward and under the rider which further increases front tire traction. This works in unison with the shorter stem length to provide a more direct steering input and dramatically enhances connectivity to what is happening with the front wheel. The shorter offset also brings the front wheel more under the rider which balances the effects of a slacker head angle. Our SBG system creates a longer trail figure than standard, used in a way that eliminates the negative side effects.

    seems to say the exact opposite…

    And now I’m confused

    Premier Icon Jordan
    Subscriber

    ayjayboubleyou
    Transition come along and go short offset forks and slack angles.
    Good at steep stuff (wheel way out in front)
    good at low speed (not so much trail – probably back to where we were a few years ago with 67-68 degree AM bikes)

    You’re still mixed up bud.

    Slack angle + short offset = long trail so not as good at low speed.

    They are saying that used in unison with a short stem it will eliminate the negative side efffects. Whether this is completely true is open to debate. It will reduce the negative side effects but perhaps not eliminate them but this is probably the best compromise for what they want the bike to achieve.

    btw. it’s not my diagram. I nicked it off of MBR.

    Premier Icon supersessions9-2
    Subscriber

    Remember that on suspension bikes the trail figure reduces as the fork compresses.

    Premier Icon benpinnick
    Subscriber

    What I wonder is, how much difference would the average rider notice between say 42 & 37mm offset when the frame is designed for 37mm offset?

    A little, not a lot. The idea that a bike is specifically designed for one offset or another is mostly marketing. Offset modifies the handling, you might prefer it one way, or the other.

    For example: Not long before SBG launched, offsets were generally much closer to what Transition said was the SHG offset preference. Then, in 2016 Rockshox decided to add 4mm to everything 27.5/drop short offset 29 options (who knows why).

    In 2017 Transition come out with SBG which is a revolutionary shorter offset… Except that the new short offset was only going roughly the same amount shorter vs the pre-2016 offset as RockShox had made you go longer the year before, and I bet most people didn’t even notice.

    Just for clarity I realise the above might be confusing…

    MY 2016 Offset: 42mm
    MY 2017 Offset: 46mm
    MY 2018 Transition Offset: 37mm

    Yes the leap from 37 > 46 is pretty noticeable, but most people probably never even thought about the difference between 42 and 46.

    concrete24
    Member

    Cotic did a nice article on the practical differences riding different offsets, (and impact on bar width).

    https://www.cotic.co.uk/news/2019/forkoffset

    Premier Icon Andy R
    Subscriber

    They’re not normal in my world….

    My new Ti forks have 62mm offset and I think that they’re the dog’s bollocks.

    Premier Icon argee
    Subscriber

    Having moved to the patrol i do notice that it handles better with a little speed and steeper descents, low speed stuff has meant a change in the way i do stuff to counter, it does feel slightly twitchy, especially if i take both hands off the bars at low speeds it just wants to turn the wheel.

    THe reality though is that you just change to suit the setup, offset, angles, trail, a change of tyre width/brand can throw those off a little as well, pressure changes in shocks/tyres as well, you just adapt, or if totally uncomfortable, change it.

Viewing 27 posts - 1 through 27 (of 27 total)

You must be logged in to reply to this topic.