General Discussion Triathlon Talk » Bike Fit Stack help Rss Feed  
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2017-01-26 9:07 AM

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Subject: Bike Fit Stack help
So I've decided to put together my own bike one piece at a time and have an initial question. I went a while back and went through a fitting for my measurements. The frame I got has a Reach of 424 (mine is 426) so basically perfect but the stack is 568 and my suggested is 526. I was supposed to have a 172.5 crank arm length with my measurements. Question, how is the difference made up? Do I get a 175 crank? Any help is appreciated but please keep it very vanilla because I am not very bike tech savvy, which is a large part of the reason why I'm doing the build. If the difference is no big deal then just say so. I am planning on buying higher end components second hand or clearance so I just would like to know if I need to do or buy something to off set the difference. Thanks in advance.


2017-01-26 9:37 AM
in reply to: Hunting Triathlete

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Subject: RE: Bike Fit Stack help

From the FitWerk site

“Stack” is the vertical distance, in centimeters, from the center of the frame's bottom bracket/crank to the top middle point of the head tube (where the fork passes through the frame). “Reach” is the horizontal distance from the center of the bottom bracket/crank to the top middle point of the head tube



BUT

sometimes people specifiy pad stack and pad reach. The difference between pad reach and frame reach is made up with stems, aerobars etc
the difference between pad stack and frame stack is made up by risers under the pads, angle stems.....

are your numbers pad stack and reach or frame stack and reach ?
2017-01-26 9:45 AM
in reply to: 0

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Subject: RE: Bike Fit Stack help
I'm not sure to be honest. I had the session with Tad Hughes in Houston. The sheet doesn't specify but it shows just a frame with measurements.

Edited by Hunting Triathlete 2017-01-26 9:48 AM
2017-01-26 6:34 PM
in reply to: Hunting Triathlete

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Subject: RE: Bike Fit Stack help

Frame reach of 425-ish is typical for a size L or 56 bike from most manufacturers.  So I'm assuming you have a L or 56 frame.

Frame stack for a L/56 usually falls in the 540-560 range.

My guess is that you picked up a Quintana Roo?  Not that it really matters.

What's more important than frame stack and reach is pad stack and reach.  Those are going to be your actual contact points.

Were your suggested fit coordinates, the 526 stack / 426 reach, for frame or pad?  If it's for frame than you'll be okay.  If it's for pad you have the wrong bike frame, and by a country mile.

The difference between the frame and pad measurements results from the stem/bar/spacers/risers used in the cockpit.  For example, my bike has a frame stack and reach of 540/425.  My pad stack and reach is about 600/460.  I have a 10mm stem spacer and the bar and pad holders (w/no risers) account for the other 50mm.  Then I have my pads set about 35mm forward.

So if your suggested numbers from Tad are for pad stack and reach you're going to be way off on stack with that frame because you'll likely have a pad stack in the 630-670 range, so over 100mm more.

How tall are you?  Not that it's the most relative number but if you say you're 5'8" there's pretty much no way you should be on a size L/56 frame.

2017-01-26 7:47 PM
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Subject: RE: Bike Fit Stack help
Originally posted by Hunting Triathlete

So I've decided to put together my own bike one piece at a time and have an initial question. I went a while back and went through a fitting for my measurements. The frame I got has a Reach of 424 (mine is 426) so basically perfect but the stack is 568 and my suggested is 526. I was supposed to have a 172.5 crank arm length with my measurements. Question, how is the difference made up? Do I get a 175 crank? Any help is appreciated but please keep it very vanilla because I am not very bike tech savvy, which is a large part of the reason why I'm doing the build. If the difference is no big deal then just say so. I am planning on buying higher end components second hand or clearance so I just would like to know if I need to do or buy something to off set the difference. Thanks in advance.



Frame stack and reach is only a starting point. What really matters in the long run is pad- (and hand grip) stack and reach.

It's usually fairly simple to make a shorter-than-ideal frame stack work using some combination of headset spacers, flipped stem, and/or pad risers to get the pad stack up. It's a bit harder to make up for a taller-than-ideal frame stack. You definitely want to use no headset spacers below the stem, a steeper angled stem (-~17* instead of the common ~-8-10*), a, and make judicious choices with your cockpit. Look for something like the Profile V2+ or V4+ extensions which go under the base bar instead of over, and allow the pad to be lower. Speaking of base bars, most are flat but some have some "drop" meaning they're bent so the hand positions are lower than the stem clamp area, like these: http://ep.yimg.com/ay/yhst-69433785329726/zipp-vukabull-40mm-drop-c...

I don't know if you can compensate completely for the higher frame stack, but you can probably get into a ballpark that would be workable.

Don't mess with the cranks. If you get your pad stack low enough, or even close to low enough, you're not gonna want longer cranks lest your knees come too close to your abdomen on the upstroke.

Edited by gary p 2017-01-26 8:03 PM
2017-01-26 8:40 PM
in reply to: GMAN 19030

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Subject: RE: Bike Fit Stack help
Originally posted by GMAN 19030

Frame reach of 425-ish is typical for a size L or 56 bike from most manufacturers.  So I'm assuming you have a L or 56 frame.

Frame stack for a L/56 usually falls in the 540-560 range.

My guess is that you picked up a Quintana Roo?  Not that it really matters.

What's more important than frame stack and reach is pad stack and reach.  Those are going to be your actual contact points.

Were your suggested fit coordinates, the 526 stack / 426 reach, for frame or pad?  If it's for frame than you'll be okay.  If it's for pad you have the wrong bike frame, and by a country mile.

The difference between the frame and pad measurements results from the stem/bar/spacers/risers used in the cockpit.  For example, my bike has a frame stack and reach of 540/425.  My pad stack and reach is about 600/460.  I have a 10mm stem spacer and the bar and pad holders (w/no risers) account for the other 50mm.  Then I have my pads set about 35mm forward.

So if your suggested numbers from Tad are for pad stack and reach you're going to be way off on stack with that frame because you'll likely have a pad stack in the 630-670 range, so over 100mm more.

How tall are you?  Not that it's the most relative number but if you say you're 5'8" there's pretty much no way you should be on a size L/56 frame.




No I'm almost positive it is frame as the bike I had before was a 56 Cervelo P2 (just 20 less on stack then this one) and the fitter said it was the closet thing he could find. FYI I'm 6' and have a 32" inseam. I'm pretty positive it's the right frame I was just worried about how big of a deal that 40 difference in stack would make. Also, yes it is a QR.

In summary I guess by yall's comments I should be good and a 172.5 crank would also still be good. Thank you for the responses and if you have more to add after reading this please do.


2017-01-27 6:39 AM
in reply to: Hunting Triathlete

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Subject: RE: Bike Fit Stack help

I agree.  It's the frame coordinates.

Did Tad not give you pad stack and reach in the fitting.  Tad is really good so I'd be surprised if they're not on your report somewhere.

2017-01-27 8:29 AM
in reply to: GMAN 19030

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Subject: RE: Bike Fit Stack help
No, but I think what I got was just a simple set of measurements for the list of bikes that he provided me as far as fit. For QR he showed M or L which is why I was a little worried when I saw the difference. After your help and others I'm thinking now that I will be fine. I also think he may not have because I'm not super serious about it and my biggest concern was a fit that would not aggregate my back.
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