's Forum Archives - General

Archive Home >> General(1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 )

what do these specs (angles) say about purpose of frame?(16 posts)

what do these specs (angles) say about purpose of frame?Js Haiku Shop
Nov 7, 2001 1:15 PM
purpose meaning built for touring, racing, whatever...

seat angle 72.39
fork rake 5.2
setback is 17
chainstay length 40.8
b.b. height 26.5
head tube angle 73.5

re: what do these specs (angles) say about purpose of frame?cioccman
Nov 7, 2001 1:50 PM
Well, right off the bat, in my experience, and in my general size range, the only bikes I've seen with that type of seat tube angle are time trialers, most of the time with shaped seat tubes. Generally, in my size range, climbers or more standard road geometry bikes are 74 degrees or 73.5 degrees. Quite a big fork rake though. Head tube angle is close to standard, though most I've seen are a half a centimeter more upright. Quite a short chainstay length.
umm, isn't that in the wrong direction?lonefrontranger
Nov 7, 2001 2:24 PM
I know my geometry is pretty "whacked", or so I'm told, because I ride such a small frame.

However, my TT bike is a 77 degree ST, my road bike is a 74 ST, and my 'cross bike is 72.5.

I am too blonde to be a math whiz, but I think the smaller the number, the more "laid-back" it is (?). Logically, 90 degrees would be perpendicular to the ground.

Sounds like it's leaning towards a long-distance randonee (sp?) or touring type geometry. Many Euro steel "stage race" frames still use a similar type geometry. But without other specifics like wheelbase, BB height, chainstay length, etc... it's hard to tell.
umm, isn't that in the wrong direction?cioccman
Nov 7, 2001 2:44 PM
Standard, simple geometry, exactly. The smaller the number the less steep the angle. 10 degrees would be close to parallel to the ground, 90 being perpendicular.

That angle puzzled me, I do know that many TT bikes are set up a bit upright like tri bikes, and others such as the Trek, have very standard seat tube angles, but, as I said, and to the contrary, the only bike I've seen with that type of slack angle is a TTr with a shaped seat tube to limit the distance between the tube and tire to as little as is legal. I'll try to find some specs on this one.

Don't know really. Good guesses above, probably set up for a classic.
Nov 7, 2001 3:07 PM
Was the TT-bike you referred to with the shaped ST one of those "old-school" lopro bikes? (small front wheel)? Some of these had *very* slack ST angles to make up for the crazy geometry and handling the small front wheel engenders. I used to borrow a lopro from my coach that had a 70 or 71 degree seat angle, and it still handled like a squirrel on crack.

If not, then maybe the shaped ST slackened the "actual" angle, but the "effective" angle was more upright (know these can be quite different, scratching head to explain...) Ah yes: moving the saddle and/or changing to a "set back / set forward" post will change the "effective" ST angle. A shaped seat tube can be hard to determine angle on, depending on the curvature.

Does that make any sense? Or am I still too blonde for this thread...
what's the standover height?nfm
Nov 8, 2001 4:52 AM
32.4" nmJs Haiku Shop
Nov 8, 2001 5:58 AM
re: what do these specs (angles) say about purpose of frame?brider
Nov 7, 2001 1:54 PM
You left out wheelbase. The slack seat tube angle pretty much rules out triathlon. Chainstay length is short enough to be racer (I think it's short for touring), but more in the 39 neighborhood gets you into crit types (but with the slack seat tube angle, that's prety much impossible without a bent tube). Havent' resolved the head tub angle and fork rake to determine trail, but it sounds in the road racing range. If the wheelbase is on the short side, I'd say it's set up for crits.
Just Guessingzelig
Nov 7, 2001 2:21 PM
Road bike, size about 58-61 ctc based upon the seat/head angles and setback. Not tourist or Audax but road racing based on chain stays and relatively standard bb height. The fork rake's got me as with the head angle, its a fairly quick turning machine unless the wheel base is fairly long. Given that, I'd say the bike and was purpose built for a race such as Paris-Roubaix where the amount of rake's for shock absorbtion..
Just Guessingcolker
Nov 7, 2001 5:14 PM
wow! does that rake means means there's a big/ long "curve" on the fork?
bike geometry is really intriguing, i love the subject. i was just telling this friend i find a road bike more comfortable over rough roads than a mountain bike. the rb has a shorter wheelbase, shorter chainstays and it's stiffer but the it feels more controlled, stable and comfortable over small sized bumps... and i don't know why!
cause of the wheelsgtx
Nov 7, 2001 10:05 PM
hey, it's Hank, I have to post under this name here

it's da wheels. Big wheels. That's why 29" mtbs (and cross bikes) are finally getting popular. They roll better over the small stuff.
some simple info for tri specific geometry.....dupe
Nov 7, 2001 3:54 PM

i wish i could find a similar site for objective and easily understood info regarding roadbikes.

hope this may be of help for demystefying (sic?) the subject of tri or time rial frame geometry.

ciao, ben
merckx strada o.s.Js Haiku Shop
Nov 8, 2001 10:52 AM
actually sort of a cross-post, since i violated the sanctity of the non-cycling discussions board and drooled over this one on that forum.

any comments/opinions on the frame?
merckx strada o.s.Nessism
Nov 8, 2001 12:25 PM
The Corsa Strada OS uses Columbus Brain tubing. This tubeset is made from what Columbus calls Cyclex steel and is similar to normal non-heat treated chromoly. The wall thickness on the tubes is fairly thick so the frame should be quite stiff - very stiff actually.
Overall this is a very nice frame however I would not expect it to be a lightweight.
merckx strada o.s.gtx
Nov 8, 2001 9:08 PM
I was going to say those numbers sounded like my Merckx, except I think the chainstay numbers are wrong--should be longer. Nice riding bike.
Those numbers are surprisingly similar to.....cioccman
Nov 9, 2001 9:41 AM
the Litespeed Ghisallo.