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Relationship between reach and stem length

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  • July 1, 2019 at 4:58 pm #29826
    at4998

    Hi all,

    I’m purchasing a new road bike which has a racier geometry than my old bike with a reach of 390 vs. 384. The comfortable stem length on my old bike was 100mm and I need to decide on the new stem length – would you recommend offsetting the increased reach by getting a 90mm stem on the new bike? The other option is to go for a 110mm stem.

    I’ll get it fitted properly, but need to take a stab at the best guess for the inital order.

     

    Thanks

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Viewing 15 replies - 1 through 15 (of 16 total)
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  • July 3, 2019 at 3:05 pm #945265
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    Boatsie

    Maybe sit on your old bike..
    Maybe sit on your old bike..
    Estimate the differences.
    Partially rest hands to emulate positions. Have a feel to your preferred own.

    On my bikes. 1 is extremely comfortable and fast at seat post to handlebar centre, 73cm.
    1 is awkward as at measurement 69cm.
    Both seats same, lagging tail 15cm aft of pole.
    I can’t get get seat back, I can’t get bars forward. That 4cm feels that it’ll make a big difference during a long ride.
    I don’t know per normal but my personal preference would be to extend reach yet that’s my measurements. Shorter would probably assist greater force of tangent, hence more torque, longer might relax biological machine better.
    Depending upon your needs, I hope that assists you.
    73cm was setup to a rider 1 inch shorter than I. I guess that’s at my low point. Is your current bike at your low reach? High reach?

    July 3, 2019 at 8:28 am #945263
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    Boombang
    Welsh boy wrote:
    Are you serious ? 6mm difference will make a huge difference to the feel of the bike.

    Yup, I jump between bikes frequently where the difference is more like 4cm and after a couple of seconds hardly notice any difference.  So long as it doesn’t cause comfort issues, especially when putting out big efforts or tired, sticking with a more neutral length stem is sensible.

    For me at least, 6mm is probably about 1% of my reach and personally swapping between different stem lengths on the same bike from 100 to 110mm has been barely noticeable, I however notice changes in height a lot more and that for me is the key to comfort.  For me shifter angles are paramount once reach is in the ballpark.

    In this case the OP is having a stab at stem length off a geo chart before getting properly fitted, so I would start at 100mm length.  As an aside though and depending on other aspects of the geometry I would rather downsize the frame, or buy a different geometry bike to shorten reach without lowering front, than run a 90mm stem.  Only if getting down to near 70 degree head angle would I start reducing stem length (like the 71 degree HA on my CX bike where I run a 100mm stem, but then I also run wider bars which in part negates the stem length change).

    July 2, 2019 at 7:36 pm #945261
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    Welsh boy

    Have a play around with this

    Have a play around with this site

    http://yojimg.net/bike/web_tools/stem.php

    July 2, 2019 at 4:32 pm #945259
    0
    at4998

    OK thanks so much there is

    OK thanks so much there is some great advice here. I’ve also reached out to Ribble who suggest going with the 110 and adjust the saddle and spacers as required.

    July 2, 2019 at 3:45 pm #945257
    0
    jaysa

    There may also be a

    There may also be a difference in the reach and drop of the handlebars.

    Your new Ribble has own brand Level 1 bars – can’t see the reach and drop for these.

    Your Bianchi bars look like 77m reach and 126mm drop.

    I’d sooner be too hunched than too stretched but ymmv.

    You can get new alloy stems from ebay for £10 – £30 so if you feel like a change it won’t hurt

    July 2, 2019 at 2:59 pm #945255
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    CXR94Di2

    The Stack and reach

    The Stack and reach difference can all be adjusted with stem length, spacers and angle of stem.  Like I said before try it, change if uncomfortable.  You’re not far from original bike settings.

    July 2, 2019 at 2:18 pm #945253
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    Jimmy Ray Will

    As mentioned above, the stack

    As mentioned above, the stack height will more of an influence than the reach differences. 

    Also, factor in that because the head angle is steeper on the Ribble, it will effectively increase the difference in reach the higher the bars are mounted on the steerer. But no more than an extra mm.

    Again as already mentioned, bar shape and lever position all have the potential to affect position as much as the 6mm listed, so its a tricky one to give a steer on.

    One way of looking at it though is to ask how your current bike feels. Is it a bit hunched up, too stretched, or just right? How you answer that should dictate if you get a 90mm stem than shortens your reach, or a 100 that lenghtens it about teh same amount. 

     

    July 2, 2019 at 1:38 pm #945251
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    kingsouth

    You also need to take into

    You also need to take into account the lower stack height. With spacers (16mm) added under the stem to match the “slammed” position of your existing bike, the reach is actually very simmilar. If you have a signifficant number of spacers under the stem of your existing bike, the Ribble is probably too low at the front for you.

    July 2, 2019 at 1:08 pm #945249
    0
    bobbinogs

    Just get the two sets of

    Just get the two sets of stats and then use this site to work out where the bars are going to go:

    http://yojimg.net/bike/web_tools/stem.php

     

    Only the OP can tell if 6mm is important, but the point about the length is that can also affect a number of other factors (play with the tool and it becomes clear how this can work). 

    Bear in mind that you may also need to factor in the STIs themselves, for instance, some of the Compag STIs have a 5mm increase in reach to get to the hood compared to Shimano. 

    Ultimately though, don’t be afraid to play with the stem length/height until you are happy.  Just get some cheap ones off ebay (other sites are available) and then, when you have settled on setup (spacers and length), buy a decent stem and chuck the rest back on ebay to recoup your initial outlay.

    July 2, 2019 at 10:39 am #945247
    0
    at4998
    kil0ran wrote:
    Difficult to tell without knowing the seat tube and head tube angles of the two frames, or the stem angle.

    If you have those details (or can find them) then this may help

    http://www.bikegeo.net/

     

     

    Hi guys,

     

    Thanks for the responses. I’ve attached the different bike geometries if that would help. Ideally I’d want to keep the same feel, although on my current bike (100mm stem) I’m sort on inbetween a 90mm stem and a 100mm stem for comfort.

     

    Thanks

    July 2, 2019 at 10:39 am #945245
    0
    at4998
    kil0ran wrote:
    Difficult to tell without knowing the seat tube and head tube angles of the two frames, or the stem angle.

    If you have those details (or can find them) then this may help

    http://www.bikegeo.net/

     

     

    Hi guys,

     

    Thanks for the responses. I’ve attached the different bike geometries if that would help. Ideally I’d want to keep the same feel, although on my current bike (100mm stem) I’m sort on inbetween a 90mm stem and a 100mm stem for comfort.

     

    Thanks

    July 2, 2019 at 10:36 am #945243
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    Welsh boy
    Boombang wrote:
    6mm is not much at all, I bet if everything else was the same (bar height, bar angle, hood length, bar shape, hood angle etc.) you wouldn’t notice the difference.

    Are you serious ? 6mm difference will make a huge difference to the feel of the bike.

    As already mentioned, frame angles will affect the reach as will the stem angle, when I get home I will post a link to a calculator which takes all the variables into account and gives you the actual overall reach. 

    July 2, 2019 at 10:21 am #945241
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    kil0ran

    Difficult to tell without

    Difficult to tell without knowing the seat tube and head tube angles of the two frames, or the stem angle.

    If you have those details (or can find them) then this may help

    http://www.bikegeo.net/

     

    July 2, 2019 at 10:07 am #945239
    0
    Boombang

    6mm is not much at all, I bet

    6mm is not much at all, I bet if everything else was the same (bar height, bar angle, hood length, bar shape, hood angle etc.) you wouldn’t notice the difference.

    If you do not have the same bars, levers, head angle and stack height (plus same angle of bars and levers) then I would put on a 100 and see how it goes.

     

    July 2, 2019 at 9:49 am #945237
    0
    ChasP

    It’s not as simple as that as

    It’s not as simple as that as the actual reach depends on the rest of the geometry, if it’s ‘racier’ it may have a steeper seat tube so the saddle may be further foreward (the reach measurement given is from the bottom bracket).  The height range suggestions for each frame may help, or contact the seller bfor advice, but as above I’d try the 100mm first.

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