Head Tube length....please explain

[Kingfisher]

So i'm looking at head tube length on various frames I have. Frames vary from 58-60 cm. Some have a long 190 head tube and some noticeably shorter.

Now I'm looking at a used 59 csi that has a 190 head tube...even longer than the 60cm Zanc that I just purchased.

Does head tube length affect ride quality, stability, etc.?

Just wondering

[Bentley]

So i'm looking at head tube length on various frames I have. Frames vary from 58-60 cm. Some have a long 190 head tube and some noticeably shorter.

Now I'm looking at a used 59 csi that has a 190 head tube...even longer than the 60cm Zanc that I just purchased.

Does head tube length affect ride quality, stability, etc.?

Just wondering

I think the taller head tubes are more about riding position, but it makes some sense that it would not handle the way a bike with a shorter head tube would handle. I am pretty sure you would not find that on a race bike, unless it was to address an issue with lower back.

Ray

[eddief]

people (me) choose a tall headtube to avoid a mountain of spacers under the stem...and to get the bars up high without a massively upjutting stem angle. I prefer the aesthetics of more headtube to both of those other things...and I still have quite the spacer stack anyway.

[ultraman6970]

Affects it in some way, the longer the front tube the more higher the position over the bike, theoretically more comfortable but thats just an debatable because depends of the rider.

But this is the thing, in regular no sloping bikes the head tube has the size it must have (unless they do like pegoretti, colnago and others do to put a neck at the top), then you have sloping bikes that pretty much they can put the front tube any length they want.

My only concern with stupid big front tubes is that the weight will be more focused in the rear wheel and the handling gets weird, the usual symptom is that the rider cant ride no hands and no way to keep that bike straight, in short the handling sucks. Sure you have one bike than handles different than the other ones and one that handles superbly nice aswell, but again depends a lot of the fit aswell.

Sure you have seen postings here of weird set ups, like 62 cm custom sloping frames with front tubes as long as my legs, super short top tube and the sten with such an angle that looks like the dude is riding a chopper, comfortable? debatable because the weight distribution is wrong, but sure the handing sucks. But since that was the ride the guy wanted the bikes were made like that. Extreme cases ok?

[Clancy]

Part of the overall fit process, a shorter HT will place more weight on the front wheel which changes handling. Headset spacers raises the stem/bar which shifts weight towards the back wheel. Shorter stem vs longer stem, seat post with or w/o set back, all effect fit and handling.

But I do agree with the confusion that I believe is the basis of your question. I typically ride a “54” TT ish frame. A Gunnar might have a 110 HT where another might be 140. There’s some frames out there that I wish I could ride (Ritchey) but the HT’s are so short that I’d have to use a stack of spacers which I believe looks like crap plus can be a little wonky if stacked too high.

[David Kirk]

I think many (most?) think of head tube length in the wrong way. It seems that many look at head tube length as something that is designed in and that it determines fit or handling or something. I can tell you from a design perspective that I have never sat down to design a bike and thought that the head tube should be XXX mm. Not once.

Bikes are typically designed to give a certain fit and handling by putting the rider's three contact points in given spots in space and then putting the wheels in a happy place below them. This will then determine a seat tube length, a top tube length, stem length, a certain amount of spacers under the stem to allow fine tuning, and a given BB drop and these things (along with lots of other small factors) determine a head tube length. In other words head tube length is a resultant of the rest of the design as opposed to being a direct input into the design.

To address your question more directly...given a certain bike fit head tube length has no effect effect on ride or handling. You could make the head tube shorter and use more spacers or make it longer and use fewer spacers or a lower angle stem and the bikes will ride the same as long as the other things are the same.

I hope that makes sense.

dave

[Kingfisher]

I think many (most?) think of head tube length in the wrong way. It seems that many look at head tube length as something that is designed in and that it determines fit or handling or something. I can tell you from a design perspective that I have never sat down to design a bike and thought that the head tube should be XXX mm. Not once.

Bikes are typically designed to give a certain fit and handling by putting the rider's three contact points in given spots in space and then putting the wheels in a happy place below them. This will then determine a seat tube length, a top tube length, stem length, a certain amount of spacers under the stem to allow fine tuning, and a given BB drop and these things (along with lots of other small factors) determine a head tube length. In other words head tube length is a resultant of the rest of the design as opposed to being a direct input into the design.

To address your question more directly...given a certain bike fit head tube length has no effect effect on ride or handling. You could make the head tube shorter and use more spacers or make it longer and use fewer spacers or a lower angle stem and the bikes will ride the same as long as the other things are the same.

I hope that makes sense.

dave


That answers my question, much thanks Dave

[Mark McM]

I think many (most?) think of head tube length in the wrong way. It seems that many look at head tube length as something that is designed in and that it determines fit or handling or something. I can tell you from a design perspective that I have never sat down to design a bike and thought that the head tube should be XXX mm. Not once.

Bikes are typically designed to give a certain fit and handling by putting the rider's three contact points in given spots in space and then putting the wheels in a happy place below them. This will then determine a seat tube length, a top tube length, stem length, a certain amount of spacers under the stem to allow fine tuning, and a given BB drop and these things (along with lots of other small factors) determine a head tube length. In other words head tube length is a resultant of the rest of the design as opposed to being a direct input into the design.

To address your question more directly...given a certain bike fit head tube length has no effect effect on ride or handling. You could make the head tube shorter and use more spacers or make it longer and use fewer spacers or a lower angle stem and the bikes will ride the same as long as the other things are the same.

I hope that makes sense.

dave

Exactly as Dave says. Similar discussions come up regarding things like how seat tube angle affects fit and handling - well, it doesn't (at least not directly). Saddle setback is what affects fit and handling. You can use an offset seatpost with a steep seat tube, or a no offset seatpost with a shallow seat tube, and as long as the saddle (and the handlebars and wheels) were in the same place, the handling would be the same.

[e-RICHIE]

Exactly as Dave says. Similar discussions come up regarding things like how seat tube angle affects fit and handling - well, it doesn't (at least not directly). Saddle setback is what affects fit and handling. You can use an offset seatpost with a steep seat tube, or a no offset seatpost with a shallow seat tube, and as long as the saddle (and the handlebars and wheels) were in the same place, the handling would be the same.

???

If two bicycles are different sizes and geometries, and the fit between them was mirrored by moving the saddle back/forth and the handlebars back/forth and up/down, then only the fits would be the same.

The handling would be different because the rider is over and inside of frame designs that are dissimilar. He may notice it, or not, or may be able to control the differences (or not). That's the abstract part of the equation that can only be addressed first hand by a user.

The head tube length question - that's one spec I never got, cared about, or even measure here. The dimension starts at the lower end, and that cutoff point is determined by fork span and bottom bracket drop. All things staying the same, frames with longer fork spans and/or more drop will have shorter length head tubes right out of the gate.

[bocobiking]

I love my big head tube:)

[Mark McM]

???

If two bicycles are different sizes and geometries, and the fit between them was mirrored by moving the saddle back/forth and the handlebars back/forth and up/down, then only the fits would be the same.

I probably didn't describe that well. What I meant was this:

Say you had two identical frames. Take one of them, and slacken the seat tube angle, but lengthen the top tube and shorten the seat stays so that all of the other frame tubes remain in exactly the same place as before (same stack and reach, same chain stay length, same front center, same head tube length and angle, etc.).

Fit the rider to the same position on both frames; achieving the same saddle set back may require a zero offset seatpost on the slack seat tube frame, and an offset seatpost on the steep seat tube frame. Now, even though these two bikes have different seat tube angles, they will ride and handle the same.

[Kontact]

I probably didn't describe that well. What I meant was this:

Say you had two identical frames. Take one of them, and slacken the seat tube angle, but lengthen the top tube and shorten the seat stays so that all of the other frame tubes remain in exactly the same place as before (same stack and reach, same chain stay length, same front center, same head tube length and angle, etc.).

Fit the rider to the same position on both frames; achieving the same saddle set back may require a zero offset seatpost on the slack seat tube frame, and an offset seatpost on the steep seat tube frame. Now, even though these two bikes have different seat tube angles, they will ride and handle the same.

The two will fit the same and have the same handling characteristics on paper, but I don't know how you could possibly conclude that two bikes with different length seat stays will ride the same.

That's like saying what tubeset they are made of doesn't matter to the ride. Shorter stays will most definitely change how vibration moves through the frame, unless both frames are made of heavy gauge pipe.

[weisan]

http://cdn.newsapi.com.au/image/v1/079906da6447415f71b3ca495ce8a69d?width=1024

[eddief]

one leg looks short :).

http://cdn.newsapi.com.au/image/v1/079906da6447415f71b3ca495ce8a69d?width=1024

[cmbicycles]

one leg looks short :).
That's just his way of saying, "I could beat you on this bike with one leg tied behind my back."

[TimD]

people (me) choose a tall headtube to avoid a mountain of spacers under the stem...and to get the bars up high without a massively upjutting stem angle. I prefer the aesthetics of more headtube to both of those other things...and I still have quite the spacer stack anyway.
This. Not everyone rides a 56 or can tolerate a bar drop like Axel Merckx.

I completely understand how HT length isn't an input parameter to a custom design which is made to fit one individual, and maybe others by coincidence.

However, if you are buying off the rack then you might start with the basics (ST, TT, angles), then consider BB drop and HT length to determine whether the frame can be made to fit without looking ridiculous. Frame stack and reach are very useful metrics; fortunately manufacturers typically (but not always) specify them nowadays - wasn't always the case - and they are doing this for a reason.

I've built up and disposed of enough frames that I know what fits me and what doesn't. I don't know how many times I've seen "XXL blah blah HT 205" and stopped reading. It just isn't going to work.

And yes, if you are a custom frame builder, I would fully expect you to say "get a fit and we'll build you a bike which fits, the HT length will be what it will be." Even still, that's different from completely ignoring it - because some day you might build a big frame for some anatomical oddball and find out the 300mm steerer on the client's must-have fork isn't long enough...

Tim

[cmg]

in looking at eddy's bike, anybody know what his dimensions are? the bike geometry can change underneath him but the triangle formed by the bars, saddle and pedals will stay the same.

[Kingfisher]

one leg looks short :).

Dang....what size frame did Eddy ride? It looks at least a 60.

[e-RICHIE]

people (me) choose a tall headtube to avoid a mountain of spacers under the stem...and to get the bars up high without a massively upjutting stem angle. I prefer the aesthetics of more headtube to both of those other things...and I still have quite the spacer stack anyway.


That works.

But for others who may isolate the head tube measurement, one really needs to compare across similar designs. If the two (or more) bicycles in question have different fork lengths and/or frame drop specs, the variables tossed in by the range out in the marketplace are so wide that they'd add up to a number larger than the amount of spacers some folks want to avoid.

The last paragraph in my other comment speaks to this.

[lhuerta]

Stack and Reach...Stack and Reach...Stack and Reach....

Look it up, figure out how to calculate for frame u own or want to compare to, and your life (and wallet) will be much happier....

[Mark McM]

The two will fit the same and have the same handling characteristics on paper, but I don't know how you could possibly conclude that two bikes with different length seat stays will ride the same.

That's like saying what tubeset they are made of doesn't matter to the ride. Shorter stays will most definitely change how vibration moves through the frame, unless both frames are made of heavy gauge pipe.

Seat stays are incredibly stiff, (compared to the other compliances in the system), so small changes in seat stay dimensions would be below the level of human perception.

Compact (sloping top tube) frames also typically have shorter seatstays than 'traditional' geometry frames of the same size. Tom Kellogg (of Spectrum Cycles) wrote a blog post about compact frames (http://www.spectrum-cycles.com/geometry.php#compact)and their ride differences compared to traditional frames (bolding added by me):

In designing the our first compact prototype back in mid '98, we wanted to discover what if any the real world differences there would be between traditional and compact frame designs. Our first compact frame (still my favorite frame) was an exact replica of my then current titanium frame in materials and geometry save for the sloping top tube. I designed it with a severe (17 degree) slope to ensure that any differences would be as obvious as possible. We had assumed that the new frame would be somewhat stiffer and lighter. It was lighter (about 4 ounces) but it was not appreciatively stiffer. Although we were able to measure a slight increase in stiffness, it was too slight to feel. The big change came when I stood to accelerate or climb. As I stood up, the bike appeared to loose three pounds. The inertia of the bike as I rocked it back and fourth was reduced so much that I felt as though I was on a twelve-pound bike. Interestingly, when seated, a compact frame feels exactly like a traditional design. The compact design has no effect on handling beyond the increases responsiveness during climbing and accelerating.

In the case of two otherwise identical frames with different seat tube angles from my example, neither frame would be sloping top tube compact. So, there wouldn't even be the small differences in out of saddle rocking the bike back and forth feel that Kellogg mentions.

[weisan]

:rolleyes:No difference but "still my favorite."

[Kontact]

Seat stays are incredibly stiff, (compared to the other compliances in the system), so small changes in seat stay dimensions would be below the level of human perception.

Compact (sloping top tube) frames also typically have shorter seatstays than 'traditional' geometry frames of the same size. Tom Kellogg (of Spectrum Cycles) wrote a blog post about compact frames (http://www.spectrum-cycles.com/geometry.php#compact)and their ride differences compared to traditional frames (bolding added by me):



In the case of two otherwise identical frames with different seat tube angles from my example, neither frame would be sloping top tube compact. So, there wouldn't even be the small differences in out of saddle rocking the bike back and forth feel that Kellogg mentions.

I was using seat stays as an example of one of the things that change when you change start modifying the way the frame is assembled. The STA also changes the way that tube bears weight. A longer TT can twist more under load than a shorter one.

What I think you may be missing is that these angles are among the things that custom builders - like the ones who have been gracious enough to post in this thread - use to make small changes in the way a bike is going to ride. Kellogg set out to make as few changes as possible between the standard and his test compact. Kellogg also is 5'6", so his seat stays aren't very long. If he had been testing a 60cm frame it may have been different - IDK.


I just think it unwise to assume that the angles of the tubes and their relative lengths do nothing to affect the way a frame flexes under load to produce "ride".

[Mark McM]

I just think it unwise to assume that the angles of the tubes and their relative lengths do nothing to affect the way a frame flexes under load to produce "ride".

Sure, adjustments of tube length and angle must have some affect on stiffness and flex. But is it of a large enough magnitude to be perceivable by humans? There is a whole field of science devoted to Just Noticeable Difference (https://en.wikipedia.org/wiki/Just-noticeable_difference).

When Tom Kellogg made a frame with extremely sloped top tube (which shortened both the top tube and seat stays), he found that he couldn't notice the difference in handling.

In this test of 7 frames made with different steel tube sets (https://www.habcycles.com/m7.html)(with different diameters and wall thicknesses, the test rider found that he essentially couldn't tell the difference.

You might also want to read Josh Poertner's blog posts about Zipp's testing of wheels and frames for the Paris Roubaix, that found that even professional riders couldn't reliably distinguish the difference in comfort between "aero race" frames and "endurance geometry" frames in blind testing.

[Kontact]

Sure, adjustments of tube length and angle must have some affect on stiffness and flex. But is it of a large enough magnitude to be perceivable by humans? There is a whole field of science devoted to Just Noticeable Difference (https://en.wikipedia.org/wiki/Just-noticeable_difference).

When Tom Kellogg made a frame with extremely sloped top tube (which shortened both the top tube and seat stays), he found that he couldn't notice the difference in handling.

In this test of 7 frames made with different steel tube sets (https://www.habcycles.com/m7.html)(with different diameters and wall thicknesses, the test rider found that he essentially couldn't tell the difference.

You might also want to read Josh Poertner's blog posts about Zipp's testing of wheels and frames for the Paris Roubaix, that found that even professional riders couldn't reliably distinguish the difference in comfort between "aero race" frames and "endurance geometry" frames in blind testing.

It is true that the majority of people couldn't tell a Cannondale from Vitus when going straight down the road. But either the changes a builder makes are perceivable to the people that pay $6000 for a custom frame, or they aren't. And if no one is able to feel them, then the custom market shouldn't exist, because you're saying that any SL steel frame will ride like any other with the same steering.


As far as endurance vs race, I have yet to see an endurance geometry that isn't someone else's race geometry. A lot of these terms are marketing, not a promise of a measurable effect.

And then there are all the things people think they "know" which probably don't work they way they think - like frame stiffness.


But I do think we should allow for the possibility that a builder working in steel tubing is using the lengths and angles of the tubes to manipulate riding forces as much as they are using tube wall thicknesses and diameters. They are all factors - even if not everyone can feel them.

[simplemind]

one leg looks short :).

Thats because he got his jeans caught in the chainring! :eek:

[bikingshearer]

one leg looks short :).

I bet Dave Kirk or Richard Sachs could design around that slight difference in leg length. :p