Viewing 31 posts - 1 through 31 (of 31 total)
  • Frame sizing – Reach?
  • Premier Icon soobalias
    Free Member

    when comparing a bike i know and ride with a new frame, is ‘reach’ one of the best comparisons, ignoring how the bike rides, for a similar style of bike.

    ive a hardtail and a full suss, ive always felt the FS a little to ‘short’, the bars are rolled forward to give a bit more space and always tempted to slide the saddle back (shoulda/coulda gone up a frame size i guess)

    what are the extremes of reach? +/- 50mm? or much less, going up a frame size seems to add only 20-30mm

    Premier Icon Superficial
    Free Member

    what are the extremes of reach? +/- 50mm? or much less, going up a frame size seems to add only 20-30mm

    Yeah, 30mm per frame size seems pretty average IME. At 6’1, I could ride most manufacturers M, L or XL frames, with L usually the prescribed option. So that gives a 60mm ish range of reaches.

    440mm reach would feel a bit short but it’s probably what I was riding a few years back. My last bike was ~470mm reach, current one is 500. They’re all pretty ‘comfortable’ for all day riding and I don’t think I’ve necessarily hit the upper limit on reach where longer = worse for everything.

    I’m fairly convinced that the longest is the fastest so far. Going from 440 to 470 just made the new bike feel ‘a bit long’, whereas the 500 definitely requires a different style of riding to get the most out of it.

    Premier Icon DanW
    Free Member

    You need to look at reach and stack together to understand the fit.

    A long reach frame isn’t necessarily that long if the stack is really small as a crude example- by the time you raise the bars up the reach will shorten. Also look at the fork length that the geo came from.

    If you know the information for your current frame then you can use this along with the stem/ spacer/ headset stack info to work out what stem and spacer combos you would need on a new frame on various websites.

    The reach and stack of different frames varies so wildly nowadays and “Large/ Medium/ etc” are pretty meaningless. Most manufacturers are pretty good though at giving ballpark height estimates for each size as the simplest way to judge.

    If that seems too complicated then buy something you like the colour of 😀

    Premier Icon honourablegeorge
    Free Member

    Reach measures how long the bike is when stood up, depending on seat angle a bike that’s long in the cockpit when stood up might feel quite normal or even short when sat down.

    Reach is one element, but top tube length is also relevant for seated position (unless you’re on a DH bike)

    Premier Icon DanW
    Free Member

    Reach and stack give tell you where the top of the head tube is relative to the BB. That is valid for seated pedaling too. Saddles have rails. So long as the seat tube isn’t crazy slack or you aren’t looking at really long travel frames that get slacker as they go through the suspension then you should be able to get the saddle in the right place relative to the BB too. Reach and stack and a cursory glance at the STA should be enough but I iz well jey and so are my bikes 😀

    Premier Icon MrFart
    Free Member

    It depends on the seat tube angle – steeper STA requires greater reach.

    Premier Icon soobalias
    Free Member

    cheers superficial, thats useful ‘feel’
    maybe i should double check the stack as i guess feel when riding is about that diagonal measurement from BB to top HT, or pedals to grips.

    colour will have to be second, but its still a big consideration

    Premier Icon ta11pau1
    Full Member

    Reah, ETT, seat tube angle, stack, all important for how a bit ‘fits’.

    Then add in the change in geo on a hardtail vs a FS (hardtail will get steeper and reach will increase as sag increases).

    Premier Icon zerocool
    Full Member

    I mainly look at Reach, Seat Tube length, Head Tube angle and Rear centre (don’t like really short back ends). Although from what I’ve been reading Stack could actually be more important than Reach.

    Premier Icon the00
    Free Member

    Top tube length, and then stack, are the most important determinant of seated comfort. The reach is what you notice (or don’t) when you are stood up. In my experience I am much more tolerant of variation in reach than I am variation in the seated position.
    Unfortunately most brands do not adequately express the top tube length to account for offset & raked seat tubes. This is especially a problem on larger sizes.

    Premier Icon Andy_Sweet
    Free Member

    Long reach is the new wide bars, which was the new short stem, which was the new wheel size etc.

    Premier Icon jobless
    Free Member

    Not connected with this at all but I found it incredibly useful when looking at bike sizing:

    https://geometrygeeks.bike/

    Create a login and you can compare more bikes.

    You will now spend days and days of your life on there. Sorry about that.

    Premier Icon fooman
    Free Member

    geometrygeeks is good stuff, according to their numbers I went from a 444mm reach to 516mm (and steeper seat, slacker fork) which I thought might be too radical a step but there is no way I can go back now – always felt a bit squeezed on before. But I think overall fit depends on so much more than a couple of numbers, must hard to get a feel on a test ride too it took a few hours in the saddle before I though yes this is right for me.

    Premier Icon peaslaker
    Free Member

    I bought my newer full suss without getting rid of my older bike. They’ve both been raced in enduros and pelted down mountainsides. At 6’2″, I can set up my riding position on both equivalently even though one has a reach of 432mm and the other 483mm. 55mm vs 75mm stem (with some rise), spacers and some bar roll sorts it out. I feel that going much longer or shorter would introduce compromise; the bikes I have bracket my preferred fit. So that’s a 51mm range of reach that’s perfectly workable.

    Reach and stack should definitely be considered together. Slacker head angles and a low stack will both undermine a nominal “reach” value – when you add spacers, the fit will not be as roomy. I expect to see a balance between longer reach and a longer chainstay. I don’t ever look at top tube or ETT lengths; for my riding these are irrelevant measurements. Saddles can adjust significantly on their rails. For the style of bike I choose, the bars are almost always too close for seated mileage but that is the least worst compromise that I accept.

    Premier Icon peaslaker
    Free Member

    FWIW, Jeff Lenosky saying hardtail reach should be shorter than full suss reach…

    Premier Icon soobalias
    Free Member

    ive not watched it yet, but sounds like the sort of confirmation bias im after.

    Premier Icon ciquta
    Free Member

    Reach doesn’t mean anything if not referred to STA.

    Reach and stack tell you how distant your wrists will be from your ankles, but only STA lets you know where your bum (and so your CG) will be.

    You can easily adjust the reach by centimeters swapping bars and stems, but you can only cheat the STA by millimeters swapping seatpost.

    STA determines not only handling and CG but the way you pedal, the muscles involved, the portion of weight you can put on your pedals.

    STA is the most important thing geo-wise

    Premier Icon chiefgrooveguru
    Free Member

    “ STA determines not only handling and CG but the way you pedal, the muscles involved, the portion of weight you can put on your pedals.

    STA is the most important thing geo-wise”

    Seat tube angle is totally irrelevant as soon as you stand up. So it has no bearing on MTB handling downhill or on standing pedalling uphill.

    I don’t care about road bikes but for MTBs seat tube angle is less important than reach, stack, head angle, chainstay length or BB height when it comes to what matters to most riders.

    Also, although on paper there is over two degrees difference in seat tube angle between my two MTBs, in reality they have the same seat tube angle at my saddle height because one has the saddle slid all the way forwards and the other has the saddle slid part way back. No other aspect of geometry is so easy to adjust.

    Premier Icon kerley
    Free Member

    Seat tube angle is totally irrelevant as soon as you stand up. So it has no bearing on MTB handling downhill or on standing pedalling uphill.

    It may well be but I am seated for 90%+ of the time so for me it is very important. My bike is set up on that basis and is perfect when seated but when standing feels a bit short so if most of my time was spent off the saddle the bike wouldn’t be great.

    Premier Icon peaslaker
    Free Member

    but I am seated for 90%+ of the time

    As someone at the more enduro end of the riding spectrum, I spend more time sat on my bike than I do standing. Climbing hills takes longer than riding down them. There are the bits in between the hilly bits as well.

    But, when I take myself down dangerous, technical descents or enduro race stages, I’m standing. Whenever I’m jumping, I’m standing. Whenever I’m having fun, I’m standing. When I’m speccing a bike, I’m optimising it for the memorable bits of riding not the filler.

    Premier Icon v7fmp
    Free Member

    interesting thread, as i have been going through the same this morning. Its a bit of a minefield and a bit confusing if you arent up to speed on it all. I am think of changing my frame (when they are available). The manufacturers height chart puts me on a Large (current bike), but on the new frame, according to the height chart i would be on a medium (im 5’9).

    The new frame reach is 465, compared to 480 of current.
    The new frame stack is 630, compared to 629 of current.
    The new frame ETT is 592, compared to 637 of current.
    The new frame Seat tube C-T is 420, compared to 445 of current.
    The new frame seat angle is 78.6, compared to 76 of current.
    The new frame wheelbase is 5 mm shorter.

    So from what i can gather, the potential new frame would be shorter when standing and considerably shorter when seated? But will it be dramatic enough to make a big difference?

    I dont find my current bike too long or uncomfortable. In fact it feels really nice to ride (i just fancy a change).

    And why is there such a difference in length between manufacturers on bikes made for similar height people?

    Premier Icon oikeith
    Full Member

    geometrygeeks is good stuff, according to their numbers I went from a 444mm reach to 516mm (and steeper seat, slacker fork) which I thought might be too radical a step but there is no way I can go back now – always felt a bit squeezed on before. But I think overall fit depends on so much more than a couple of numbers, must hard to get a feel on a test ride too it took a few hours in the saddle before I though yes this is right for me.

    Similiarly I went from 465 reach to 511 reach with a longer wheelbase, slacker HA and steeper SA. Took 2 descents/15 mins to get “used” to it, this was November, now the grounds are drying out and the trails are running faster I am having to get used to the higher speeds the bike encourages!

    Premier Icon mudeverywhere
    Free Member

    Seat tube angle is not irrelevant when standing. If you’re used to a slacker angle and more rearward seated position your natural standing position will likely be that way as well. Slacker can cause the tyre to buzz the saddle when the suspension compresses. Seems to be a particular problem for shorter riders on 29ers, or pro downhillers (maybe they just like the sound). Also changes the height when lowered. A 200mm dropper lowered at 78 degrees is not going to be the same height or position as it would at 74 degrees. There are some fairly wild variances in seat tube angles at the moment that can’t be accounted for by just sliding the saddle forward or back.

    Reach is a byproduct of other more important measurements, including seat tube angle and effective top tube. If anyone sizes a bike just by looking at reach and stack they’re taking a big risk.

    Premier Icon alan1977
    Free Member

    that raises a few good points
    which is more important, seated or stood… my transmitter and aeris i prioritise being stood, im stood 99% of the time going down stuff, and 40% going up. reach becomes a key measurement
    my flat bar gravel bike, i spend 85% seated and effective top tube is probably more of a useful figure to consider.

    Also as above, i didnt know it was a thing, but my hardtails are shorter in the reach than the Aeris. which is huge at 480 odd for a M/L with me at 5ft 8, while my transmitter sits around 440 from memory, similar seat tube angles. again because the front on the hardtails pitches down way more than the Aeris, lengthening the reach when my body is staying vertical/central

    Premier Icon chiefgrooveguru
    Free Member

    “ Reach is a byproduct of other more important measurements, including seat tube angle and effective top tube.”

    It isn’t. It’s the horizontal distance between the centre of the BB and the top centre of the head tube. ETT derives from stack height, reach and effective seat tube angle. Turning it the other way around is completely contrary to logic but it mean seem sensible if you’re used to the old way of doing things.

    “ Seat tube angle is not irrelevant when standing. If you’re used to a slacker angle and more rearward seated position your natural standing position will likely be that way as well.”

    Your body still has to balance, unless you rely on weighting or pulling the bars to stop yourself from toppling over. Seat tube angle may influence your momentary position when standing but now we have long dropper posts it’s less and less relevant. It was very different when we rode with fixed posts.

    Premier Icon Blackflag
    Full Member

    When im stood up im moving all over the place. One foot is 175mm in front of the reach measurement and one 175mm behind. My weight is centred based on the angle of the bike and the terrain. its never static.

    Premier Icon mudeverywhere
    Free Member

    It isn’t. It’s the horizontal distance between the centre of the BB and the top centre of the head tube. ETT derives from stack height, reach and effective seat tube angle. Turning it the other way around is completely contrary to logic but it mean seem sensible if you’re used to the old way of doing things.

    That’s incorrect. In order to calculate reach you first need a seat tube angle, effective top tube and stack. Even if designing for a specific reach figure you wouldn’t start with that and then add the others on. Bizarre. Let’s remember companies only started providing a reach figure to help us understand standing sizing, it’s a byproduct.

    Premier Icon peaslaker
    Free Member

    Personally I start with the normal distance from the steering axis to the BB. I’ve analysed a bunch of geo charts and remarkably a huge number of bikes come in with round numbers of millimetres for this measurement in their sizes. I like ~700mm bikes in peaslaker effective normal improved sizing (hint: look closer)

    Why? Because stem length adds to it and stem spacers don’t alter it at all. Once you’ve got head tube angle and as long as the head tube isn’t too long you’re golden.

    If there is sufficient interest, I’ll start an NSFW thread for how to measure this.

    Premier Icon chiefgrooveguru
    Free Member

    “In order to calculate reach you first need a seat tube angle, effective top tube and stack”

    To fix the reach of a bike, all you need is the head tube joined to the down tube joined to the BB and joined to the chainstays (and to know the fork A2C length). That gives you the reach and stack, the head angle, the BB drop and the chainstay length. You don’t even need a seat tube or top tube (obviously structurally you do but you can put them wherever you like if they fit, it doesn’t change the other tube positions).

    Premier Icon kerley
    Free Member

    To fix the reach of a bike, all you need is the head tube joined to the down tube joined to the BB and joined to the chainstays (and to know the fork A2C length)

    Agree, seat tube angle and ETT are nothing to do with reach measurement.

    Premier Icon mudeverywhere
    Free Member

    That gives no thought for seated sizing, might as well be a trials bike then. I don’t mean to alarm anyone here, but the fact is sizing for most bikes is designed first and foremost with a seated body position in mind. Obviously there are other measurements involved but this means picking a desired seat tube angle and effective top tube length directly controls the reach measurement. Doesn’t matter if the bike is intended for downhill fun while standing up, that’s just an added bonus of additional seated cockpit length required now we want a better climbing position from steeper seat tubes and better handling from shorter stems.

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