Re: [CR]geometry, materials or the power of suggestion...

(Example: Framebuilding:Technology)

From: "john hawrylak" <jphawrylak@phd-computers.com>
To: <classicrendezvous@bikelist.org>, "ADP" <aphillips9@mindspring.com>
References: <5.2.1.1.2.20030525140051.0393ea58@pop3.norton.antivirus>
Subject: Re: [CR]geometry, materials or the power of suggestion...
Date: Mon, 26 May 2003 11:43:46 -0400


As Geoff pointed out, the top tube and distance behind the BB should be different for the same the frame size just from the trig of the problem. The Trek should have more distance behind the BB and a longer top tube for the same frame size. Additionally, the standover heights should be different. since the BB drop are equal, with the Waterford being higher above the ground (assuming same tires and rims and air pressure).

The following differences exist for the same frame size (seat tube length) form the trig, with all numbers in units of cm:

Frame 49 50 51 52 53 54 Diff in setback 1.69 1.72 1.76 1.79 1.83 1.86 Diff in SO Height .48 .48 .49 .50 .51 .52

Note, the Diff in Setback is the increased distance behind the BB (due to the seat angles) and is equal to the increase in TT length if the head angles were equal. The Trek TT should be slightly longer due to the steeper head angle. However, the head tube length is needed to compute the difference.

As an aside, I thought the shallower seat tube angles were beneficial since the increased setback bought other muscles into play.

John Hawrylak
Woodstown NJ


----- Original Message -----
From: ADP
To: classicrendezvous@bikelist.org
Sent: Sunday, May 25, 2003 2:46 PM
Subject: [CR]geometry, materials or the power of suggestion...



> I'm hoping someone here has some insight for me on geometry and ride
> characteristics.
>
> First of all, it seems awfully suspicious that a degree here or there in
> angle would cause me to be a noticeably far more effective cyclist and have
> the ability to change the "feel" of the bicycle so radically.
> Since both the bikes I've ridden a lot recently fit me so well, and I can
> document fairly detailed geometry specs, I thought I'd check this out with
> the brain trust here. Maybe someone can explain this to me!
>
> Trek:
> Seat tube 73.25 degrees
> head tube 73.5 degrees
> bottom bracket drop 7.5 cm
> wheelbase 99.6 cm
> fork offset 4.2
>
> Waterford:
> Seat tube 75.3 degrees
> head tube 72.8 degrees
> bottom bracket drop 7.5 cm
> wheelbase 984.9 cm
> fork offset 4.2
>
> The Trek is full 531, frame and fork. The Waterford is 853, triangle, 531
> fork, 531 head tube and TrueTemper platinum stays. Obviously there is a
> significant weight difference...
>
> What I've noticed specifically, is the Waterford is much more responsive to
> increased pedaling speed, corners nicer, is more responsive to steering and
> it is easier to get a nice rhythm out of the saddle.
>
> Since the wheelbase differences are pretty minor, are all these differences
> just due to the head and seat angles?
>
> If so, that means that my Montelatici will handle more like my
> Waterford. Stevan tells me that the head tube is 72.5 and the seat is 75.0.
>
> I know this stuff is probably uber-geek to be concerned with, and Ray (my
> really nice boyfriend - credit him and mom with the Birthday Waterford)
> tells me to stop quantifying fun, but it is my nature to know why, and
> thats what I wanna know!
>
> On another, more classic tack, when did all this attention get paid to
> geometry in bicycle manufacture? Did the people riding the 49 Giro know
> this stuff, or at least the people making their bicycles? Did everyone
> follow the same school of thought??
>
> Ann Phillips, Atlanta Ga - where the sun has shone for the last three days
> and bicycles got ridden!