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Home > Forum > Triathlon Forum > Stack and Reach of bikes I'm considering.

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Stack and Reach of bikes I'm considering.
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littlefoot
Dec 25, 20 20:46
Post #1 of 9 (1248 views)
Referencing two prior tri bikes and S/R as I am considering 2 bikes:
Medium Transition: Stack 516 Reach 395 Wheelbase 975
Medium Trek SC Stack 517 Reach 408 Wheelbase 985

I'm considering the Cervelo P-Series 105 and a Trek Speed Concept Medium (above) again. Based on previous fit I liked my fit and ride of the Specialized Transition a lot. The Trek fit well to, but seemed to also climb different. Is that because of the wheelbase being longer and reach being longer? Based on my numbers from the Medium Transition, it seems that the 51 Cervelo is a smart move. Would going with a 54 something I should steer away from, or something that I could work out since it matches the Trek SC fairly closely?
Cervelo P 51 Stack 506 Reach 398 Wheelbase 976
Cervelo P 54 Stack 522 Reach 412 Wheelbase 995

Does Wheelbase even play into something I should consider, or not worry about it?
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Re: Stack and Reach of bikes I'm considering. [littlefoot] [ In reply to ]
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m_sasso
Dec 25, 20 23:57
Post #2 of 9 (1223 views)
If you have narrowed your search down to those two frames, you should carefully take in to consideration the entire frame geometries, not just stack and reach. Critically evaluate the seat tube and head tube angles which will greatly impact your true reach numbers. A steeper seat tube angle moves the saddle forward while a shallower angle moves the seat back the higher the seat post is raised. And yes, the wheel base numbers will defiantly affect how the different size frames will ride, in general a shorter wheelbase will be more responsive, less stable, and have greater toe overlap. Suggest you get with a knowledgeable friend or experienced fitter before making a purchase.
Marc Sasso
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Re: Stack and Reach of bikes I'm considering. [m_sasso] [ In reply to ]
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1415chris
Dec 26, 20 0:49
Post #3 of 9 (1210 views)
Any change in the seat tube angle is compensated by the saddle settings (within the given limits). That allows you to have identical saddle position in the relation to the bottom bracket's axis on the bikes with different seat tube angles. The head tube angle impact is already captured in reach.
So the angles will not change position, however they can have impact on how the bike rides or how someone can fill how it rides.
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Re: Stack and Reach of bikes I'm considering. [1415chris] [ In reply to ]
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m_sasso
Dec 26, 20 2:02
Post #4 of 9 (1201 views)
1415chris wrote:
Any change in the seat tube angle is compensated by the saddle settings (within the given limits). That allows you to have identical saddle position in the relation to the bottom bracket's axis on the bikes with different seat tube angles. The head tube angle impact is already captured in reach.
So the angles will not change position, however they can have impact on how the bike rides or how someone can fill how it rides.


Differences in the seat tube angles could possible be compensated with fore aft saddle settings however it is by no means automatic and not to be disregarded.

So are you suggesting if a spacer/spacers are placed under a stem, actual reach will not change dependant on the head tube angle?
Marc Sasso
Last edited by: m_sasso: Dec 26, 20 2:10
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Re: Stack and Reach of bikes I'm considering. [littlefoot] [ In reply to ]
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jn46
Dec 26, 20 3:19
Post #5 of 9 (1185 views)
A few cm in wheelbase by itself won't dramatically change things handling wise, but front centre and trail will. If you ride steep then you might want more front centre for better weight distribution and more stability when in the aero bars. Conversely you might want shorter if you do a lot of technical courses and climbing and want a very responsive handler. I'd lean towards more front centre for most triathlons though, unless you're doing Tour prologue style TT around winding streets and throwing the bike around.
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Re: Stack and Reach of bikes I'm considering. [m_sasso] [ In reply to ]
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1415chris
Dec 26, 20 9:36
Post #6 of 9 (1134 views)
m_sasso wrote:

Differences in the seat tube angles could possible be compensated with fore aft saddle settings however it is by no means automatic and not to be disregarded.

So are you suggesting if a spacer/spacers are placed under a stem, actual reach will not change dependant on the head tube angle?


Once again, seat tube angle has nothing to do with the the saddle position, has no impact on where the saddle is placed in the "space" in relation to the bottom bracket. Any angle changes are compensated by the saddle movement and seatpost. So yes, for that purpose it can be entirely disregarded.
Equally head tube angle. And no, spacer will not change the reach, as it is fixed bike geometry measurement. You cannot change bike geometry.
Since you decided to bring to the equation additional variable (spacer) I will add two more, stem length and bar reach. Shallower head tube with the added spacer makes the position shorter, but you overcome this, if necessary, by the these two mentioned.
However these changes are so small, that they can be disregarded too. For instance, 20mm spacer and quite extreme 5deg in the head tube angle difference gives about only 3mm!
Last edited by: 1415chris: Dec 26, 20 9:50
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Re: Stack and Reach of bikes I'm considering. [littlefoot] [ In reply to ]
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trentnix
Dec 26, 20 9:57
Post #7 of 9 (1123 views)
littlefoot wrote:
Referencing two prior tri bikes and S/R as I am considering 2 bikes:
Medium Transition: Stack 516 Reach 395 Wheelbase 975
Medium Trek SC Stack 517 Reach 408 Wheelbase 985

I'm considering the Cervelo P-Series 105 and a Trek Speed Concept Medium (above) again. Based on previous fit I liked my fit and ride of the Specialized Transition a lot. The Trek fit well to, but seemed to also climb different. Is that because of the wheelbase being longer and reach being longer? Based on my numbers from the Medium Transition, it seems that the 51 Cervelo is a smart move. Would going with a 54 something I should steer away from, or something that I could work out since it matches the Trek SC fairly closely?
Cervelo P 51 Stack 506 Reach 398 Wheelbase 976
Cervelo P 54 Stack 522 Reach 412 Wheelbase 995

Does Wheelbase even play into something I should consider, or not worry about it?
The armpad stack and reach of the options you are considering has a more significant impact than the frame stack and reach. For example, there are 6 different cockpits on that Speed Concept that are part of the equation.

With integrated and pseudo-integrated cockpit options, the frame stack/reach values aren't as useful as they once were.

If you get a fit on a fit bike, the fitter should be providing fit coordinates based on your contact points, not based on some mythical frame that was presumed to be underneath you.
Trent Nix
Owned and operated Tri Shop
F.I.S.T. Advanced Certified Fitter | Retul Master Certified Fitter (back when those were things)
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Re: Stack and Reach of bikes I'm considering. [littlefoot] [ In reply to ]
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scott8888
Dec 29, 20 15:53
Post #8 of 9 (1035 views)
The Transition was/is a bit of an odd fish in terms of frame stack and reach and you would really want to know pad x/y. The whole front end of the Transition, including the brake cabling, was designed to run with a longer stem and more headset spacers than other TT bikes. It’s actually incredibly difficult to cable the bike in a ‘slammed’ position as it wasn’t intended to be ridden in that way.

The need to run a long stem on the Transition to get a decent pad reach value did impact the handeling. This is probably what you noticed between the bikes. Overall I would be looking to the size 54 Cervelo as the point of comparison not the 51.
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Re: Stack and Reach of bikes I'm considering. [scott8888] [ In reply to ]
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littlefoot
Dec 29, 20 16:04
Post #9 of 9 (1032 views)
Thanks, I appreciate your response. I decided to go back with a speed concept. Should be at my doorstep in a week or less. Excited to be back in the sport
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