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  1. #1
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    How important are Stack + Reach vs. Top Tube Length and Standover Height?

    So I currently ride a 49cm Allez (Specialized Bicycle Components) and I like the way it fits.
    I'm looking at this frame (GreatKeen Bike Sport Equipment Co.,Ltd) and I'm just a bit confused as to what I'm supposed to be looking for in terms of compatability.

    I'm stuck between the 48cm and the 51cm on the second bike. The 48cm has a smaller horizontal top tube and standover height. The standover height on my Allez is just right. However, when I was trying out the 52cm Allez at my lbs, they told me it would fit me just great if the top tube was a bit shorter.

    Now, the stack on the 48cm S5 and my Allez are both 505cm. The reach on the S5 is a bit smaller.

    Final Questions: Does Reach counteract a longer top tube? Would I be more comfortable with a slightly longer top tube and shorter reach?
    Thanks!


    **Yeah, I know the best thing to do is try the S5 frame out, but there are no Cervelo dealers near my current location :/

  2. #2
    wyrd bi ful rd
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    Measure the 'effective' top tube on your current bike and note the stem length, and get your new frame along the same lines ...

    I do not put much thought into standover or frame sizing. 2 frames with the same effective top tube length can be 'sized' as 48cm or 51cm.

  3. #3
    FTR
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    Standover is mainly important if you like spending lots of time standing over your bike.
    ETT is far more important to get right.

  4. #4
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    Stack and reach are directly related to bike fit (relative positions between the crank, saddle, and bars). Top tube length and stand-over height are more indirectly related to fit.
    ... 'cuz that's how I roll.

  5. #5
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    Let's see ...

    How important are Stack + Reach vs. Top Tube Length and Standover Height?-s5-vs-allez-geo.jpg

    Quote Originally Posted by YOLO View Post
    So I currently ride a 49cm Allez (Specialized Bicycle Components) and I like the way it fits.
    If you like the Allez, the short answer is to go with the 48cm S5. Aside from a 6mm shorter top tube, it's virtually the same size. You can compensate for this difference with a slight saddle adjustment.

    The stack difference between the 48 and 51 S5 is due primarily to a taller head tube, 114mm vs 134mm. This variance not only raises the standover but moves the top tube closer to your upper body ... something you'd notice when you get out of the saddle to climb or sprint, i.e. your knees will have less clearance.

    I'm assuming your Allez fits well without the use of an unusual setup, stem or seatpost. A pic of your Allez and/or you riding it would be great.

    Quote Originally Posted by YOLO View Post
    Final Questions: Does Reach counteract a longer top tube? Would I be more comfortable with a slightly longer top tube and shorter reach?
    The 48cm S5 will probably use the same stem length as you use on your Allez to achieve the same fit (or reach), maybe 5mm longer. The difference in handling would be negligible.

    As for comfort, that's more a function of seatpost and stem adjustments. The top tube length merely gives you a starting point. From there, you'd fine tune saddle and bar position to get comfy.

    Questions?
    Last edited by joeinchi; 07-11-2013 at 08:22 AM.

  6. #6
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    Quote Originally Posted by joeinchi View Post
    Let's see ...

    Click image for larger version. 

Name:	s5 vs allez geo.jpg 
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    If you like the Allez, the short answer is to go with the 48cm S5. Aside from a 6mm shorter top tube, it's virtually the same size. You can compensate for this difference with a slight saddle adjustment.

    The stack difference between the 48 and 51 S5 is due primarily to a taller head tube, 114mm vs 134mm. This variance not only raises the standover but moves the top tube closer to your upper body ... something you'd notice when you get out of the saddle to climb or sprint, i.e. your knees will have less clearance.

    I'm assuming your Allez fits well without the use of an unusual setup, stem or seatpost. A pic of your Allez and/or you riding it would be great.

    The 48cm S5 will probably use the same stem length as you use on your Allez to achieve the same fit (or reach), maybe 5mm longer. The difference in handling would be negligible.

    As for comfort, that's more a function of seatpost and stem adjustments. The top tube length merely gives you a starting point. From there, you'd fine tune saddle and bar position to get comfy.

    Questions?

    OMFG YES!
    This is exactly the kind of information I was looking for
    And yea, I'll try to post a picture of my bike setup. The only thing I did was flip the stem so that my neck wouldn't be as sore after long rides.

  7. #7
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    Quote Originally Posted by joeinchi View Post
    Let's see ...


    If you like the Allez, the short answer is to go with the 48cm S5. Aside from a 6mm shorter top tube, it's virtually the same size.

    The 48cm S5 will probably use the same stem length as you use on your Allez to achieve the same fit (or reach), maybe 5mm longer. The difference in handling would be negligible.

    As for comfort, that's more a function of seatpost and stem adjustments. The top tube length merely gives you a starting point. From there, you'd fine tune saddle and bar position to get comfy.
    A couple of important corrections. You based your comment re: stem length on the ETT. Unfortunately the STA varies greatly between the two bikes. Assuming both measure reach the same he looking at a 27mm difference in reach between the two, meaning the stem length would not be the same, not even close.

    You also state that he should fine tune saddle and bar position to "get comfy." Saddle fore/aft measurements should be based on his location with regards to the bottom bracket. The stem length can be adjusted for comfort, but stem and saddle adjustments are not to be used interchangeably. In essence, if one person owns numerous road bikes all will feature the same saddle setback (measurement between saddle nose and center off BB parallel to the ground), though different spacer stacks, stem lengths and stem angles should be expected.

    Saddle setback will be achieved in different ways depending on the STA of the individual bike, but should not vary in most circumstances.

  8. #8
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    Quote Originally Posted by xjbaylor View Post
    A couple of important corrections...
    Thanks for chiming in xj. I agree with these clarifications. And the point regarding saddle fore/aft position relative to BB is no minor issue which is why I asked for a look at the current setup.

    However, the S5 is a different animal and comes with a reversible seatpost. Going from a 25-35mm setback to zero with a simple flip would increase the effective STA to virtually the same as the Allez ... before any fore/aft saddle adjustments. Wouldn't it?

    Also, it's common for multisport competitors to utilize a different setback on their race vs training bike, so while I agree that setback should not be used primarily to tweak ergonomics, I believe we need more information regarding Yolo's plans for the bike before we can make a suggestion on which setup would be optimal.

    Quote Originally Posted by xjbaylor View Post
    Assuming both measure reach the same he looking at a 27mm difference in reach between the two, meaning the stem length would not be the same, not even close.
    I wasn't sure where you got the 27mm variance. I only saw a difference of 6mm between the 49cm Allez vs the 48cm S5.

    Clearly, you have a good understanding of the finer points, so please feel free to elaborate. It's all good.

  9. #9
    FTR
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    Quote Originally Posted by joeinchi View Post
    Let's see ...

    If you like the Allez, the short answer is to go with the 48cm S5. Aside from a 6mm shorter top tube, it's virtually the same size. You can compensate for this difference with a slight saddle adjustment.
    You should not adjust for a shorter TT by moving your saddle AFAIK.

  10. #10
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    Agree. The statement was made to demonstrate just how small a difference in TT lengths exist between the two bikes, 6mm or 0.24".

  11. #11
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    More to ponder. The design differences between the two bikes make it a challenge to use some of the specs to determine the right size.

    For example, the aforementioned seat tube angle. While the Allez employs traditional design (where the seatpost continues along the same angle as the seat tube), the racier S5 seatpost takes a steeper angle as it exits the frame. See pic.

    Also, notice the low-profile headset on the S5. Stack measurements only apply to the frame but use of headsets with different top cover heights changes the effective stack spec (and reach to a lesser extent).

    The bike in the pic also has a cut steerer and minimal, if any, spacers; a new bike will probably have a longer tube and spacers but it's something you'd want to confirm.

    Finally, the top tube shape and its connection point to the headtube can also affect knee clearance ... something not reflected in the stack measurement. As you can see, the S5 top tub is relatively straight and connects near the top of the headtube, whereas, the Allez top tube bends down and meets the headtube a bit lower. It's probably negligible but, yet, another reason why a test ride is probably the best way to determine which size to go with.

    Damn sexy bike, though! I can see why you're eager to pull the trigger.
    Attached Thumbnails Attached Thumbnails How important are Stack + Reach vs. Top Tube Length and Standover Height?-design-s5-vs-allez.jpg  

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