modern forks, rake, geometry (The old way made more sense to me)

[KneadEd]

I'm returning to building after years away. And yes, I did try searching the archives for this type of information- but this forum is new to me, so I might have missed it.

I'm confused about geometry as it seems to have become standard "boring".

When I started riding in the 80's each region had their own "fit", it seemed. the Italians had "square" frames, and the head tube angle and seat tube angle were about equal, the French went with long top tubes, steep head tubes and shallow seat tubes. Frames came in CM increments and stems were in 0.5cm choices. Of course some companies measured C-T others measured C-C... And there were French threaded BB's...

But now it seems that every carbon bike has 45mm offset fork, sizes are S, M, L, XL. I swear that the standard rake used to be 43mm. I swear I've made a steel frame with a 40 rake with steep head angle that was great fun to ride.

A few months ago I set my steel frame in front of my pickup, and forgot about it oops... and my Cinelli carbon is a quality bike, but doesn't cause me to giggle when I ride. The last steel frame I made was a fine rocket of fun. Over rough roads I found that I would automatically "gun it", and the bike handled a like fun crit bike (Trad tube sizes- ie 25.4 TT, 28.6 DT, thin walls). However, descending the steep mountain, hard corners in the wet, the back wheel didn't feel "secure". The fork and frame are now fully bent and flattened, so measuring it isn't an option.


My favorite riding frame is my early 80's Colnago, followed by my custom TIG welded SOMEC. The Colnago is a bit short for me, and is retired and now on the wall. The Somec is getting built back up with cross parts, as it was made as "sport-touring" frame with low-rider mounts and canti brakes and set long for 40c tires.

I have a few lug sets left, so I have a couple of attempts ahead of me to to make my perfect Colorado Training bike: Fun to do 12,000 vert feet, 90+ miles. If I ride "around my block" (four consecutive left turns) I have two 18% grades, and the descents have annoying intersections. If I go east there are annoying false-flats on the way home. For those that know Boulder: Lefthand/ Olde Stage/ Lee Hill/Nelson/Neva is my neighborhood.

The next frames will be pressed lugs and trad diameters, then moving on and finishing with OOS lugged frames. Pinned, of course :) I've kept my skill with a torch to a working level (brazed up the shift linkage in my last car), but can't find all the parts to my frame jigs...

Your thoughts and opinions on geometry are appreciated. I am aiming for a 4-6 hour frame that makes me want to giggle and keep riding. I'm 50lbs heavier than I was when I raced (and failed) in Brussels, so the frame weight don't mean shit... I want a frame that will help me ride enough to lose some "fluff".

Thanks!
Ed

[e-RICHIE]

Geometry is the wrong word. It’s design. The design is chosen for two goals only; to position a rider above and between two wheels, and to ensure that the wheels are the right distance apart, and that the machine acts like the vehicle it’s maker intended.

Not much has changed since I began looking. The dots are in essentially the same places, but the lines connecting them are different lengths, and also less likely to be horizontal.

[KneadEd]

I hear ya, good sir.

however in your list of "two goals only", you list three objectives :)




I'm going to beg to differ that not much has changed since the esteemed MrSachs began looking.. now is there carbon and Ti, but it's my understanding that you you started back before fire was invented... just kidding.

But seriously, back in the 80's Bianchi's rode differently than Gitanes, vs Fuji, vs Pinerello.

Any bike can get you to the line first. Sean Kelly would win major sprints on a bike that Bicycling said "too whippy for any one over 150lbs." But I no longer care about the finish line, I care about why I first got into cycling - because it's fun!


Anyhow, this inspires me to write about the fun of great frame, but I don't have the time today.

have a great day y'all

[e-RICHIE]

Hey there - it's a get three pay for two gig we're running here.

Across the board, points and dims haven't changed that much, and the ones that do change do so over generations, not seasons.

I think you may be focused on the market-driven aspect of design rather than the actual real world differences and advantages.

Kelly wouldn't ride a Vitus now, nor Gimondi a six speed freewheel. Despite what any of these cats are using, the rolling speed isn't that much different among them. It's an even playing field.

And, while I'm charmed by old parts and the history of my predecessors, I'd never wanna make things the old way, nor use drivetrains that were older than a season or three.

I hear ya, good sir.

however in your list of "two goals only", you list three objectives :)




I'm going to beg to differ that not much has changed since the esteemed MrSachs began looking.. now is there carbon and Ti, but it's my understanding that you you started back before fire was invented... just kidding.

But seriously, back in the 80's Bianchi's rode differently than Gitanes, vs Fuji, vs Pinerello.

Any bike can get you to the line first. Sean Kelly would win major sprints on a bike that Bicycling said "too whippy for any one over 150lbs." But I no longer care about the finish line, I care about why I first got into cycling - because it's fun!


Anyhow, this inspires me to write about the fun of great frame, but I don't have the time today.

have a great day y'all

[EricKeller]

If you had a bike that you liked, why wouldn't you copy those dimensions?

People know more about bikes now than they did then, but it still comes down to what you like. Don't let marketers tell you what you should like, they'll tell you to like something different when they want to sell you a new bike.

[Andrew R Stewart]

I think the need to place a label on this or that frame is getting in the way of doing something. One of the reasons why I build frames (and I'm not calling myself a framebuilder) is because I can design and make whatever I can without regard to others. Andy (who uses labels like "club, touring and station wagon)