I've noticed a trend in road bikes in the last year or so, perhaps longer, that tends towards super steep seat tubes and super slack head tubes, especially in smaller frames (I lean towards the smaller end of the spectrum).

Once upon a time, the generally accepted standard road geometry was 73/73; 73 degree seat tube, 73 degree head tube.

Lately, especially the smaller sizes, look closer to 70-71 degree head tubes and 74-75 degree seat tubes.

The obvious effect of this is the bikes ride great in a straight line, but feel like steering a cadillac into a sharp corner. I noticed this specifically when comparing the 3 bikes I've owned. My Neuvation FC100 (while arguably not a perfect 'race' bike) has the typical 73/73. The bike fits me well and handles great. It's a bit flexy in certain key areas which hold it back a bit, but the bike handles great otherwise. My favorite bike of the bunch is a Mercier Kilo TT (also the cheapest of the bunch, go figure). Sure, it's fixed and a 'track' bike. The reality is it's a steel road bike with relatively classic road geometry with track dropouts. ST/HA is 74/73. On this bike I ride a ~20mm setback post with the saddle almost all the way back, so effective angle is likely close to 73.
Now enter the outlier... for reasons I can bring up in a separate discussion, I purchased a 44cm (way small for me) Specialized Dolce and fitted with a 400mm seatpost and 110mm stem (to stretch it out to fit; I normally ride a 47-49). Anyway, this silly bike has a seat tube angle of 75.75 and a head angle of 70.25. I noticed the bike tended to "lag" a bit on the front end in corners and was very noticeable in a particular criterium where I noticed myself entering turns much earlier than most of the other riders, and tracking much wider. So I went researching.

What I found was there are almost no bikes left on the market (in size 50 or smaller and sometimes in larger frames also) that are anywhere close to the 73/73 geometry!

What gives?

Smaller bikes tend to have problems with toe overlap. Hence, a little less angle on the head tube puts the front wheel a little further away from your shoe. Handling is complicated. Fork rake & the setback on the wheel play just as much, or more, of a role in handling(depending on scenario). The beast handling bikes I've ridden had a 74 head tube angle with a wheel setback at "around" 2"(I have my own secret formula). Seat tubes seem to play, if done right, more of a roll in comfort, than performance. This obviously leaves out a lot of variables in frame construction.

lately?
meaning sometime time since the '50's ?

general road geometry for HTS and STA hasn;t changed much in 40 + yrs, with some exceptions.
54 to 58 has generally fallen in to the 73+- x 73 +- (lemonds tended to slacker STA...) with smaller sizes progressively having Slacker HTA and steeper STA. Reverse for 59/60 cm and larger.
Track bikes have always been 'steeper'. Track dropouts - Track bike, track geometry. Fixie maybe. Bike meant for derailleur/road setup, not likely.
Since compact became common, sizes hereto never heard of (47 and smaller) were available. Those very small sizes, from what I've seen, all come with slack HTA and steep STA.
There's lotsa reasons for this. I actually won;t get into these, since I don;t think you can rustle up ANY Road Geometry chart showing a 50 or smaller frame with any angle approaching 73, now or from any distance time in the past.
The only frames I've seen, off-the-rack 'ROAD' bike below 52 with anything even close to 73 angles were the Italian steel frames from the 70's and early 80's.

Sizes 47 and smaller were never heard of before compact geometry simply because of compact geometry in itself. "Compact" geometry really only refers to the shortening of the seat tube and sloping of the top tube. Today's size 47 is very equivalent to a size 50-52 of yesteryear. In example, the size 47 typically has a c-c seat tube measurement of 47cm while the top-tube measurement is typically between 51cm and 52cm. Before classic geometry, this same bike would have a 50cm seat tube and be measured as such. Also, prior to compact geometry, (with some exceptions) any bike with smaller sizing than this would mandate the use of smaller wheels, i.e. 650c, etc.

I understand that toe overlap occurs in smaller frames, but that seems like a small price to pay for a bike that actually handles well. The slack angle issue really only seems to occur in bikes 52cm or smaller for the most part, excluding bikes explicitly labeled as "endurance" or "comfort" models.

I can't speak to the 'what gives' question you posed, but if you're looking for bike options that work with your numbers, the Breezer Venturi size S (45 ST, 525 ETT) has a 75º ST, 73º HT.

My size M/L (54 ST, 570 ETT) Venturi has a 73.5º ST, and 74º HT, so it's also an outlier by the numbers amongst the larger sizes. Trail, by the way, is 62mm (2.16") with the stock fork.

https://www.breezerbikes.com/bikes/specs/venturi-fmst

That's a really good spot for trail @ 74deg. Should take corners like it knows what it's doing. The Compact Fad has done a lot for tightening up frame triangles, stiffening up frames. I say fad because, with carbon frames you can build a tube shaped to take all of this out of the bike, if you wanted to. You can argue weight but, even that is a non issue, these days. A lot of what you see in frame design is experimental, to a certain extent. Even back in the LA days they had software to predict aero/strength & stiffness characteristics. Ride quality is really where experimentation is needed. Even that has a lot to do with components. As a rule, & the rules are pretty loose these days, there are certain known perameters that effectively make a bike corner well.

It truly does. It's an absolute blast to ride because it's ridiculously precise; it turns in instantaneously, so when you push on the bars it leans over and goes. A dab of power at the pedals, a slight twist at the hip, look where you wanna be, and bang! it's off on another line. I love it.

As a rider that had 50-52 cm frames for close to 30 years I've had my experience with slacker head tube angles and steeper seat tube ones. Remember to keep them separate though - head tube angle has to do with handling, seat tube angle with fit. (If you want to get technical seat tube angle can be part of the frame and since weight distribution, chainstays, BB height, fit, etc all come into play then technically ST angle has to do with handling but it's really about fit, within a certain normal range).

Virtually all my 50 cm frames had a 71-72 HTA. They had 74-75 STA.

When I went to a compact (Size M Giant) the frame was really meant to be a bit more versatile and it was meant to be closer to a 54-56 cm frame. They went with a 73 deg HTA. I forget the STA but it was in the 73-74 deg range. The 73 HTA was spectacular. I went to a size S Giant and it was still good, I think 73 HTA.

I then went to a Cannondale 52, 73/75 or so. This was the best handling bike I'd ever ridden, 73 HTA with 43mm rake, a front end that didn't mush around in the corners, and I had noticeably faster cornering speeds on fast curves. I think the laterally rigid set up really helped because I felt like there was no deflection to the side. At the same time it was comfy enough for 7+ hour rides.

If I could ask for any combo of angles on a bike it'd have a 73 HTA and a 75.5 STA (to fit my short quads). This is what I got when I got my first custom frame.

As a note on STA with fit etc I found that my particular set up, with a longer TT (56.5), longer front end (14 cm stem with compact bars or 12 cm with regular), I need to have shorter chainstays to keep enough weight on the rear wheel. Instead of the very neutral 40.5 cm stays on the Cannondale I found that a 39 cm chainstay works much better.

The Dolce is a women's specific geometry frame, so its not surprising that the geometry is different than a unisex or men's frame.

Women's specific geometry really has nothing to do with this discussion.
@aki, I might end up having to go custom in order to achieve the characteristics I'm looking for. I referenced seat tube angle just to make the point for the trend changes in geometry. A 73 degree seat tube just happens to be ideal for me as I have relatively long legs/arms and a relatively short torso. There are a lot of factors at play that associate seat tube with handling, but my primary focus towards that point was head angle and respectively trail. Coincidentally, my Kilo has geometry that works really well for me. It's just I haven't been able to find any road bikes that have similar geometry in the same size metrics. FWIW if the STA was 73 instead of 47, I'd likely just move the seat a bit forward to compensate.
Geometry chart here: https://www.cyclesmercier.com/geometry_tt.html (47cm)

Edit: I'm also considering rebuilding my Peugeot with modern components (cheaper than custom). It's geometry is (I'm almost certain) is 74/73 STA/HA in size 50cm.

What comes first? Stack and reach? Or all these angles?

Not necessarily. Many, if not most, manufacturers size their compact frames based on what the seat tube length would be if it had a horizontal top tube. Your 44cm Dolce, for example, has a 37.6 seat tube.

This has nothing to do with compact geometry and everything to do with market realities. People don't want 650C wheels and manufacturers don't want the extra SKUs. If you run 650C wheels, it's hard to share tubes on group rides, you have a smaller selection of tires and you have to use a bit different gearing in the rear.

Toe overlap is more of an issue as frame sizes get smaller. I think Cervelo specs standard angles all the way down their sizes and they sell their bikes with the caveat that the little ones will have toe overlap.

These are compromises that the bike industry has dealt with for decades and different manufacturers have dealt with them in different ways.

I don't understand what you mean by this, or more accurately, how you could make such a determination. Care to explain?

halfspeed, thank you for clearing that up. That's something I wasn't aware of.

chaadster, I came to that determination by reflecting on my seat position relative to the bottom bracket.

Aside from the fact that seat potion relative to BB can be set in other ways than the seat tube angle (e.g. saddle rail position in seat post clamp, seat post head layback), what I was getting at is how did you relate seat tube angle to long arms/legs and short torso? It seems to me that top tube length, bar size and stem length would be more important to fit than ST angle... I'm not saying I have perfect understanding-- which is why I'm asking-- but I simply have never thought of seat tube angle as an indicator of how a rider will fit on a bike.

I can see slack ST angle affecting the ride character of a bike, but relating it to fit based on body type is foreign to me.

Seat tube angle is more about feel than anything, unless we are talking TT Bikes. Seat tube angle can change a whole host of things, handling is mostly from the handlebars to the front axle. TT length has nothing to do with bike fit. The reason being, BB to handlebar distance on a horizontal plane is the dimension that matters. If you change the angle of the seat tube, the TT length changes. If the BB is still in the same position & you are measuring the TT, you will be in for a surprise. Case in point,my MX leader has a 58.2tt & my Pinarello Montello a 56.5 TT. The Montello fits a half CM bigger. Put the frames side by side & the MX is a much bigger frame, real estate wise. However, bb to front end is that half CM shorter. The have nearly identical front geometry. The MX has a 72.2 deg ST, Pinarello 73.5

I agree with this. I fit from BB->saddle->bars so seat tube angle is really the first factor in frame fitting for geometry (the seat tube length is a close second but that part is easy).

When I spec'ed out my frame I used my current saddle-BB position/relationship to figure out a good seat tube angle. My "methodology" was pretty simple - I figured out the angle of a straight line between my BB and the center of my saddle rails. This was 76 degrees, based on having a zero set back post. The builder recommended going slightly less aggressive at 75.5 degrees. This has worked out fine.

In the past my saddles were always slammed all the way forward. Now they're slightly forward of center, with plenty of room to go either way. I thought I'd end up experimenting with more forward positions, since those positions weren't available to me with slacker seat tube angles, but after trying a slightly more forward position I returned to what appears to be a pretty optimal position for me, that 76 degree position (give or take a few mm).

(In terms of seat tube length I knew I wanted a compact type geometry based on how a lower top tube bike felt when out of the saddle, and I just asked for the same size seat tube length as I had on that bike - 40 cm c-c, about 44 cm c-t. I knew I'd have plenty of seat post left so that wasn't a concern. With a level top tube I'd been riding a 52 cm.)

The seat tube angle affects where your body will be positioned in relation to the bottom bracket. On most bikes, with most people, this relationship is irrelevant. However, on smaller bikes, the tendency is to steepen the angle which can cause a rider to sit too far forward on the bike if they have relatively longer legs than the mean population the bike is designated for. I brought up my personal dilemma to state that solely based on my height, I should be able to ride a size 50 or possibly a 52, but due to issues with body position on the bike and reach, I fit best on bikes towards the smaller end of the spectrum. This is in a way the entire basis of the dilemma, as larger sizes typically do not have the same issues with geometry.

That Kilo has a lot of trail, believe it or not, meaning it's more stable than a "regular" bike. Based on this site (first time I've used it) it results in 64 mm trail. My set up, 73 deg with 43mm rake, results with 58 mm trail.

The 37.5 mm rake is normally for a track frame, with a steeper head tube angle. With a 74 degree head tube angle a 37.5 mm rake results in the 58 mm trail. A 75 degree head tube angle, which I think would be aggressive (but I'm not a track expert), would result in 52 mm trail.

One thing about a custom frame is that you can ignore foot overlap to specify whatever HTA and rake you want. Most manufacturers want to minimize overlap and compromise handling to do so (slack head tube angle with more rake = similar trail but more clearance). A local woman that raced at a high level rode a bike with a 47 cm top tube with a 73 degree head tube angle and normal 43 mm rake (I'm assuming that last bit since I can't tell visually if it was a 40, 43, or 45, but realistically it would have been a 43). She had massive foot overlap but that bike was her favorite one. She rode it in lieu of virtually all of her (free) sponsor frames. Eventually she got some carbon frame that worked for her and that became her "go to" bike. She even had decals produced each year to imitate her then-current sponsor's frame so the bike looked right. The story here is that she would much rather have a nice handling bike overall than one that was a touch more forgiving when making u-turns on sidewalks at low speeds.

In terms of custom I think that if you have specific geometry needs, like a shorter or longer top tube for a give seat tube range, then custom frames can really, really work out. I waited a long time to get a custom frame, suffering through too-short-length frames for a long time. When I got my first custom frame (I have two, same basic fit/geo) it was just amazing. I got a second the next year, with a slight change (shorter chainstay), then had the first frame modified to reflect that shorter chainstay. The frames weren't light, about 300g and 500g heavier than my SystemSix, but I wouldn't trade (and haven't) the right fit to save a few relatively meaningless grams.

It's interesting that toe overlap with clipless pedals is not quite as much of a problem for me as it was with toe clips back in the day. I used to have a problem even on my 54 cm steel frames with normal head and seat tube angles. Even selecting the best size clips they were just a little longer out front than my preferred position puts my shoe front on clipless pedals.

The last key is wheel size, which really effects things like BB height. The frame geometry would be much easier to hold constant with a 650c wheel on the smallest sizes, since the overall bike would essentially be scaled from a ~58cm frame.

It also holds at the other end of the spectrum. A sometimes ride with a gentleman who is about 6'8". He rides the largest size bike Trek makes, and yet, when you see him coming you wonder why he's riding a kiddie bike.

Oh, I see...yes, that does make sense. Thanks for the clarification.


If a steeper ST is coupled with a longer Front-Center, would that be workable? Would combining a setback post with a long rail saddle give the positioning you want?

@chaadster, technically yes, but it would feel like riding a noodle backwards.
@Everyone else, I've decided to retrofit the old Peugeot. The geometry is almost identical to the Kilo (Same head tube angle, fork rake is just a hair steeper) and should end up being a really nice all-around frame.

Should end up with a decently nice bike for a fraction of the cost of custom. The only downside is the front end will be very heavy with the stainless threaded fork, threadless adapter, etc etc. Maybe I'll eventually upgrade to a Wound-Up fork or something, but it'll do for now.

Don't discount a carbon threadless fork. By itself good for a 0.75 to 1.0 lb weight reduction depending on what you have and what you get. But that is just the beginning. That fork will enable considerable other weight reductions in the lightweight threadless headset, stem, and modern light bars. Not being a preservationist, I consider these upgrades essential to the refreshing of a vintage steel frame. (My shields are up!)

Finding some parts, especially modern ones, for old French bikes can be a bit challenging.