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  #1  
Old 02-12-2020, 03:03 PM
tmadrecki tmadrecki is offline
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Longer vs. shorter reach, impact on handling

Hi there -

I'm currently considering a new custom build and musing about past bikes - what I liked, what I didn't, etc. from a geometry perspective.

It struck me that some of the bikes I've liked over time have a longer reach. At 6'2", I generally ride a 58. So for example, my Van Dessel Full Tilt Boogie has a pretty long reach for a CX bike in that size. What I've generally found is that the longer, lower geometry seems more stable at speed (possibly due to longer wheelbase as well?) relative to more twitchy/nervous frames that are shorter reach.

What's the general feedback on how reach impacts handling? For example - a frame with 395 reach combined with a 16 offset seatpost, versus a 411 reach frame with a 0 offset seatpost? Will they handle similarly if other values are kept constant?

I have my own thoughts on the matter but wanted to crowd source some opinions to start... thank you all!
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Old 02-12-2020, 05:20 PM
robt57 robt57 is offline
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"with a 16 offset seatpost, versus a 411 reach frame with a 0 offset seatpost?"

The reach is from the BB center. The offset of the seatpost will strictly be a component of the Seat Tube Angle with your required 'setback' astride/riding 'behind the BB'. The the Length forward to the cockpit from there come next.
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  #3  
Old 02-13-2020, 12:47 PM
tmadrecki tmadrecki is offline
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So - just to ensure I'm tracking... are you saying that offset seatpost shouldn't be factored into total reach calculation for fit purposes? And given that it shifts weight of rider back behind BB, wouldn't that have a corresponding impact on handling (however slight)?
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Old 02-13-2020, 02:48 PM
robt57 robt57 is offline
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The setback is factored in for required setback dependent on seat tube angle and even saddle rail lengths as far as usable adjustable range if you have a fav you can not live without.

Your TT length requirement can only be measured from the setback position required. If the STA is +74^ is it more likely you'd use a post with setback. A 71.8 STA where a Zero offset is more likely to be in the window of your setback.

Think of the correct saddle position for your required setback in space with only a dot below [BB Center] Now picture a seatube put into that picture.

If the STA is 74^ the rail/clamp connection point will be more forward on the rails and visa/versa if the STA is 71.8^. Setback or no setback on the post will be chosen to make that connection point closest to the center of the rails, and/or to have the adjust-ability be in range for your saddle in space.

The setback position is the constant for you/your/fit. The rest gets tweaked to accommodate it.

Thus, if you have a setback post and the saddle is slide all the way forward [to achieve setback], post can have less setback, or even Zero setback if in range.
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Old 02-13-2020, 03:23 PM
robt57 robt57 is offline
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I will give some opinion on the reach equation being you started by asking about reach.

Note that bike with lots of stack [endurance geom, to coin a phrase] tend to have TT shorter. Angle of your body riding the factor. Low stack, your body angle is steeper and your hypotenuse longer. Longer reach for more aggressive posture astride etc... But I think I made clear setback is the starting point.

And this is why I liked when they started using reach and stack specs. TT length comparing choice to choice is more deterministic that STA. Or less math to get worn anyway.
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Last edited by robt57; 02-13-2020 at 03:36 PM.
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Old 02-13-2020, 04:21 PM
tmadrecki tmadrecki is offline
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Thanks - all that makes good sense.

Just thinking about bikes I have enjoyed riding, what I've found interesting is to note handling difference relative to positional / fit changes. Longer reach and lower stack might be more aggressive / racier, but it also (to me at least) feels more planted - more weight on the front wheel? - and stable at speed.

Climbing out of saddle especially, I also feel like there's a point where your weight distribution / position above top tube and bottom bracket changes the perceived feel of bike underneath you and the steering stability. Does that seem fair?
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Old 02-13-2020, 06:25 PM
robt57 robt57 is offline
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Quote:
Originally Posted by tmadrecki View Post
Thanks - all that makes good sense.
No disagreement thus far.


Quote:
I also feel like there's a point where your weight distribution / position above top tube and bottom bracket changes the perceived feel of bike underneath you and the steering stability. Does that seem fair?
I think ultimately how it feels is what is really important.

But when looking at new/another you gotta understand what constitutes correct fit for ones self, or have someone you trust to rely on.

I also have always said that evolved aggressive position for road riding take many thousands of miles to 'evolve" into. Thus custom geometry for a newbie not likely a fruitful expenditure.

When I recall all the LBS shops in the 90s when I went from MTB to road putting me on 56CM bikes... My customs since 2000-01 and in have a 588mm TT.

But, had I got put on that long of a bike before logging 10k, also never would have worked... The 56 Trek 5200 lasted 2 months, then 58s, and 3rd season I was 59-60s. 56 bikes to 59/60 is way different fit.

I was a roadie as a teen I should say, but over 25 years as non roadie. No rider really.
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  #8  
Old 02-14-2020, 10:59 AM
tmadrecki tmadrecki is offline
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I'm laughing because I used to ride a 56... then a 58... now feel more comfortable on longer and lower versions of "58"...
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  #9  
Old 02-14-2020, 11:46 AM
robt57 robt57 is offline
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Quote:
Originally Posted by tmadrecki View Post
I'm laughing because I used to ride a 56... then a 58... now feel more comfortable on longer and lower versions of "58"...
So have you found as I have piles of miles evolved you to the much longer position?

My longest TT EFF is 603. [my customs=588] Now I have needed to fit the shortest reach bars and a eff stem [one piece w/mini aeros built in] I could get.

This is 15mm longer than I'd do on purpose [don't ask] on the outside. Having said that, I am on the mini aeros most of the time. [satellite Di2 button et al]. But I have always preferred longest stems and shortest reach bars [long femurs].

I used to bar/bang my knee occasionally hopping out of the saddle for a sprint in the old long reach bar days. Bar reach of 126mm VS the 70mm ish I use these days. Think about that reach dichotomy the industry has cast upon us in a few decades...

And the ramps on Modern bars near flat comparatively. So the shifter sit a lot higher for same bar height as bar changed too.
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Last edited by robt57; 02-14-2020 at 11:56 AM.
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  #10  
Old 02-14-2020, 11:53 AM
robt57 robt57 is offline
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I'd add:

My same 588mm TT Strong had 126mm reach bars, a 13CM stem, and 11CM saddle/bar drop 20 years back. Same bike today is 85 reach and a 12CM stem, and 8.5 CM Saddle bar drop.

And when the Strong was my #1 back then, I rode a lot with the STi top palmed in the middle of my hands as sue-do aero bars, a lot.

Lots of 'back thens' for this 'has been' I am afraid. But still stretch out a good bit for an old fart I guess. 29" saddle tip to very tops of the STIs. Ape arms to go with the long femurs...
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  #11  
Old 02-14-2020, 11:58 AM
tmadrecki tmadrecki is offline
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That. Is a lot of reach!

Thanks for all the feedback. Much appreciated.
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  #12  
Old 02-14-2020, 12:06 PM
robt57 robt57 is offline
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Quote:
Originally Posted by tmadrecki View Post
That. Is a lot of reach!

Thanks for all the feedback. Much appreciated.
I think I was supposed to be taller, but unfortunate adolescent very poor single parent deprived me of good nutrition during my most important growing years. And now I am shrinking, but that is mostly in the spine as we loose disc material as I understand it. Even 1mm x 23 discs in your spine, well do the math. I am about 7/8" shorter than 20 years ago @ 62. But seems to effect reach on bike minimally.

Any shorter cockpit I use today VS then is mostly a component of a shorter hypotenuse due to less stack.

I did gain about 2CM of bar drop back when I lost 40lb, now that there is room for my lungs to get air with all the missing bulk when not in the prone position.
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  #13  
Old 02-17-2020, 11:34 PM
giordana93 giordana93 is offline
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it's great to seek information and all, but really the conversation should be about choosing who will build the custom bike and trust the builder. they should know these things and if they don't (or allow you to design the bike) you should look somewhere else
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  #14  
Old 02-18-2020, 03:35 PM
tmadrecki tmadrecki is offline
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Totally agree - was really for some edification and also in the event that I don't go the full custom route, to better understand bike geometry and what I like / why
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