avhed

Are there any around new or used? I am only after the small diameter frame tubes.
I have seen a couple that are lugless (from Soma & New Albion), but I guess they are generally not available lugged unless a builder purposely bent the bottom lug.
A frame that takes disc brakes would be a bonus, but that is unlikely on a light gauge frame like Tange Prestige.

T-Mar

What do you condider to be a steep seat tube angle?

avhed

~73 degrees is standard. Anything more would be steeper.
Some Somas and the New Albion Homebrew is ~73.5( both lugless TIG welded). Anything more would be super.

verktyg 

56cm C-t-C is 57cm C-t-T.

A lot of classic frames from the 70's and 80's in that size had 72° to 73° seat tube angles whereas some smaller sized 54cm - 56cm frames had 74° angles.

In 1974 Motobecane started making frames for their 57cm-58cm performance models with 74° seat tube angles: Grand Jubile, Grand Record, Team Champion/Champion Team.

Gios Torino frames from the mid 70's to the early 80's had b*ll busting 75°-76° head and seat tubing angles (what used to be track geometry). I picked up an early 80's Gios a few years back. I forgot how harsh they ride.

I have a long torso with short thighs and neck. I prefer riding frames with a 74° seat tube and a short top tube because it allows me to ride in a more upright position. I like the seat all the way forward too and I use 70mm - 80mm stems depending on the top tube length and bar reach.

I have some moderately priced frames and bikes I'm going to be selling. PM me with your price range and what you're looking for.

verktyg

Kontact 

A variety of Italian bikes might run with 73.5 in a 56. But you understand seat tube angle doesn't do anything, and adding .5° is like sliding your seat forward 5mm?

verktyg 

Most published frame geometry specs range from bull pucky to wishful thinking. The majority of European frames were built without the benefit of any jigs or fixtures. A number of old Brit frame builders prided themselves in that they never measured anything, they did everything by eyeball!

The standard procedure was to put a BB shell in a vice or on a hearth then start cutting tubes to estimated lengths, hand filing the miters and brazing the main triangle. After the frames were brazed they were "cold set" to align them. During the brazing process the expansion and contraction caused by heating and cooling could easily change the angles by a degree or more!

Think of those frames as being "hand crafted". Great builders produced great riding and handling bikes (but not precision machines).

In the US bike manufactures like Schwinn, Trek and most of the custom builders used jigs and fixtures so those frames were more accurately brazed and required less cold setting to align them. The tubes were machine mitered too which gave better tube to tube contact. By the late 70's many European manufactures (not necessarlly small builders) started using fixturing which produced better quality frames.

Fusion welded steel, aluminum and titanium frames assembled with jigs can be produced to closer tolerances than lugged brazed frames. Lugless frame accuracy goes back to whether they're built in jigs or not and how well the tubes are mitered. The clamps holding the tubes should be loosened and re-tightened after heating each joint to relieve built up stresses which can change the angles.

One other thing to consider, the angle of the dropouts can change the head tube angle and thus the seat tube angle by at least a degree depending on the front to rear location of the rear wheel. I've seen a 2+ degree head tube angle change due to the rear wheel position on some frames.

Hand crafted frame building:










Published frame geometry specs. In reality these angles and dimensions are nominal at best. There was no way that they could consistently produce .5° angles!




@avhed Maybe, the question should be asked, why are you looking for a steeper angled seat tube?

verktyg

T-Mar

By the mid-1980s the majority of racing frames in a 56cm size. had a seat tube angle steeper than 73 degrees. The mean was probably closer to 74 degrees, circa 1985.

John E

Interesting, and consistent with my own observations.

My ca. 1960 Capo frames are 55cm C-T, with 72 degree parallel head and seat tube angles. My ca. 1980 Bianchi, also 55cm, has 73 degree parallel head and seat angles. The Bianchi is somewhat stiffer, but I attributed this mainly to the shorter chainstays and reduced fork rake.

Kontact 

While there may be many frames that weren't very dimensionally accurate, there is no reason that a frame built without a fixture can't be accurately made by aligning each joint after each brazing operation instead of waiting until the end. If the head tube to DT angle is accurately cold set, and then the DT to TT is accurately set, followed by the TT to ST and the ST to DT, there's really no way the frame can be any less aligned than when it is all done at once. The tubes set the distances and the lug angles + cold setting form the angles.

The rear triangle is a triangle, so if the tubes are the right length there is no real way for the angles to be off.

So I think you are confusing poor quality control with the build method.

Kontact 

Your tri bike is designed for you to be laying on your forearms. A 78° STA on a regular road bike would be terrible for use with regular handlebars because you'd have to support so much weight on your hands.

verktyg 

How many frames have you built? How many have you cut apart to repair? How many have you realigned?

verktyg

Kontact 

Zero. So you can now explain why it is impossible to build a frame with the correct angles working one joint at a time.

avhed

You understand sliding your seat forward requires the same amount forward on your stem, which shifts your weight forward?

avhed

Great, it would Motobecane and Gitane. All I need to hear is Peugeot now, because the French frames need french sized parts.

avhed

Built the same as their track frame?

Kontact 

That's incorrect.

If you want to sit on a saddle that is 80cm high and set back 7cm from a vertical line running through the BB, you can do that without needing a specific seat tube angle.

On a bike with a 72 STA, you will have the saddle seemingly more forward on the seat post than a bike with a 73 STA, but both will be in the same spot from the BB.

Your legs don't know or care with the seat tube angle is. Your reach is also completely independent of the seat tube or nominal top tube length - it is based on your seat location. It is highly unlikely that you need a special seat tube angle for anything. That concept is why saddles have long rails and seat posts with different set backs are sold.


What is it that you are trying to do?

verktyg 

Never saw a Gios track bike.

In the mid 70's when Gios was becoming one of the premo brands, they started producing frames with 75° angles. Back then only track bikes used that kind of geometry and it was unheard of for road bikes.

Road bikes with steep angles like these tend to have twitchy handling and a harsh ride. Track bikes were built to ride on smooth track surfaces plus be highly maneuverable to make fast changes and avoid crashes.

Except in the Fixie fantasy world, track bikes were always such a small portion of bikes produced that they were rarely even listed in catalogs. Many track frames were custom built especially in the UK.

verktyg

Kontact 

Dude, I've worked for frame builders, I have a set up to do it, I'm a blacksmith and welder. I don't need a lecture from you on stuff I've known for decades.

You said there was "no way" they could be built to spec, today you have a different story. I'm not interested.

verktyg 

plonk

jamesdak 

LOL, for a minute there I thought I was on the Road Forum vs the usually chilled out C & V.