showlow

I watched a bunch of videos, read a bunch of articles, and it still doesn't make sense to me...


I have never bought a new frame before. I've only ever bought used bikes from dentists who get bored of them at a fraction of the original price. It's a system that works but there's zero chance I'm going to find what I want used in the next few years. This is what I'm trying to achieve. What I want is a road bike that takes fat-ish tires (35mm+), has disc brakes and thru-axles for easy wheel swapping, and is more comfortable over long distances than my Lemond. I am looking at the All-City Zig Zag. What I really want is an Allied All-road, but I can't afford one. The All-City isn't cheap and I have been pouring over the numbers to try to understand how it will handle and feel. Ultimately, I just don't want to be disappointed with it, you know? What I want is a bike that feels as fast as my Lemond Zurich but is lighter, and more versatile by taking fat tires to tackle some dirt roads.


So, I compared the geo of the Zig Zag to some other bikes I own and it... just doesn't make any sense to me. All-City's marketing for the Zig Zag claims it has their "famed road geometry", but the Zig Zag's geo is nothing like the Mr. Pink it's probably going to replace.


Questions...


1.) Why is the wheelbase on the Zig Zag so long?

2.) Why is the head angle so slack?

3.) Will this bike be (feel?) slower than my Zurich?


Zig Zag

HTA - 72.5

STA - 72.5

BB drop - 70

WB - 1043.5

Chainstay - 420

FR - 51

Trail w/ 25mm - 55


Lemond Zurich

HTA - 73.5

STA - 72.5

BB drop - 70

WB - 1000

Chainstay - 41.5

FR - 43

Trail w/ 25mm - 57


Cross Check

HTA - 72

STA - 72.5

BB drop - 66

WB - 1029.9

Chainstay - 42.5

FR - 44

Trail w/ 25mm - 65


Mr. Pink

HTA - 73

STA - 73.5

BB drop - 70

WB - 1023.1

Chainstay - 42

FR - 45

Trail w/ 25mm - 58

AnkleWork

That approach almost guarantees disappointment. Guessing that you will like a certain geometry+material+build that you have never ridden is a great way to fail.

Spend a lot more time riding than buying/selling. Soon your head will clear and you will begin to think about something important.

mpetry912 

yes, I agree with the above. Many have spent 1000s of bucks on "custom frames" built to their exact specs and been disappointed. I'm not going to get into a hypothetical discussion based on measurements. Keep reading. Keep studying. Have someone let you ride a "steep" bike like a Raleigh pro, and a touring bike. Read the article on steering dynamics of 2 wheeled vehicles in Bicycling Science by Jim Papadopulous and David Gordon Wilson, this is as good an explanation of fork rake, trail, and head tube angle as you are likely to find.

Also try swapping front wheels and see how that effects "handling" and road feel. I don't ride as much as Sholow, but I ride a lot and I have a fleet of nice bikes. They are all different. Understanding frame geometry and how it affects bike handling is not something you can learn in a 10 min YouTube video.

Mark Petry
Bainbridge Island, WA USA

Mad Honk 

I think I spent six months of study on frame geometry before I ever picked up a brazing torch to repair frames. It is amazing how as much as 1/4" in the bottom bracket height will affect the handling of a bike. And it didn't take long to understand there were definite limits on wheelbase of what is and is not ride-able. Sometimes I think it is just a test, test, test, situation to find what really feels good while riding. I've been riding over 50 years and my needs and requirements of feel change daily. There are some general geometries that will fit you, but will need final tweaking of seat position,bar width, and stem length. And the list could go on but most is found by riding and feeling the set-ups. Hope your quest goes well, MH

mpetry912 

Find someone who will let you ride a Richard Sachs for an example of a highly refined, pinnacle example of the framebuilder's art.

Don't just take it around the block, ride it for 20 miles and note your perceptions.

That ride will tell you more than anything we can write here.

Mark Petry
Bainbridge Island, WA USA

TiHabanero

What I have discovered about what makes a bike feel "fast" are the wheels and trail. Light wheels jump nicely, and are interpreted by the brain as "fast". 60mm trail in my book is the perfect medium between stable and "quick" steering. I like trail longer than 60, but I am not interested in a lively feel to the bike, but more interested in stability as I no longer race.

Just built a touring frame with an experimental 9cm of bb drop and 60 mm of trail. The bike is stable like a touring bike, yet corners just fine. Another frame I built has a 7.5cm bb drop and 68mm trail. The bike is stable, but does not corner tight, and requires a lot of input to carve a tight turn.

I have yet another frame with 7cm and 55mm trail. I is stable as the other two frames, but requires little input to carve a corner. A natural crit machine, yet still a joy out on the open road.

The "famed" geometry of the Zig Zag looks very similar to the Bstone RB1.

3alarmer 

.
...keep buying from those dentists. SAves money, and eventually you'll figure out what feels good to you.

Andrew R Stewart 

If I can put my words to what I've come to believe Richard Sachs bikes are about it is that they are specific to the customer and intended purpose. I wonder if he would agree that a bike he built for one rider was a good example of what he would build for another rider.

While I agree with Th's basic drop and trail range he feels good within I have to blend this with front/rear centers and general fit. That I am on the small end of the size range makes the geometries challenging. Andy

mpetry912 

A Richard Sachs built for any rider is a very special bike. It may not be the right bike for you but it is an example of a hand crafted precision made frame. The RS I show here (25th Anniversary Limited Edition #19/25) is RAZOR SHARP. When you ride it, you get it.

Again, it may not be the right bike for you but it's a very special bike. and if you wanted to "learn about frame design" one ride on this bike would tell you more than 100 miles on a 20 year old Cannondale.e

And I won't even mention the DiNucci.

sorry

Mark Petry
Bainbridge Island, WA USA

showlow

It's amazing that you could pick that out. You're right, it's almost exactly like an RB1, but with longer chainstays, I suppose to accommodate the larger tires. The RB1 is a bike I've always wanted to try and have heard a lot of good things about. I suppose that the ZZ has a totally different HTA than the RB1, but with the fork offset, you end up with basically the same trail.

Zig Zag vs RB1

HTA - 72.5 vs 73.5

STA - 72.5 vs 73

BB drop - 70 vs ?

WB - 1043.5 vs 1000

Chainstay - 420 vs 410

FR - 51 vs 45

Trail - 55 vs 54

reconnaissance

Shiwlow - I had to laugh at your observation about buying used bikes from dentists. I once bought a nice vintage BMW motorbike from a dentist in Prescott Valley. he put a lot of money into it and then tired of it and I got it along with boxes and boxes of spare parts for not a lot of money.

As for road frame geometry I will first say there isn’t really any “best” geometry because it depends on what you want. In general, the longer the wheelbase the better the bike will track a straight line. The shorter the wheelbase the “sportier” it will handle, and stiffer it will feel. A Head tube angle which extends the front wheel forward is the greatest contributor to the feeling of tracking a straight line. A shorter chain stay lends to less frame flex on the power stroke. This translates to how the bike “feels” to the rider, like the others have said. Pay attention to the contributions of Mr. Sachs.

The length of your legs, the length of your torso, and the length of your arms are also important factors in selection of the frame measurement. Commercial production bikes are targeted at achieving sales numbers and do so by appealing to the greatest population within the target range. This is done in part by choosing a popular frame geometry for the target market. But if you have shorter than average legs and longer than average torso length, a “popular” geometry might not feel right to you. A good bike shop will be able to help tailor the bike to your bones.

Since minor variations can be compensated for by seat setback and stem length, I recommend you focus on whether you want a bike that tracks the line better—which will be less tiring on a long ride, or a stiffer, quicker feel for sprints and hills. Frame material is another variable with it’s own twists and turns.

Cheers,

Mike

mpetry912 

I'm skeptical that you can "understand frame geometry" by doing A/B comparison of the tube lengths and frame angles. You might better spend your time developing your impressions of how a particular bike feels. If possible ride many bikes on the same route and note the differences. Remember too that the tube guage (wall thickness) and manufacturer are all related to the overall "feel" of a bike along with the frame geometry.

Finding a way to describe how a bike feels is not easy. there's no common language that can accurately characterize terms like "responsive", "dead", "relaxed" etc. In engineering flight test there are terms like "linearity", "dynamic stability" and my favorite, "stick breakout force" that pilots use to convey their impressions about how a plane feels in various flight regimes. Another way to think about it is to imagine a ball in a bowl - the bike is riding along and you want to initiate a turn, you are going to roll the ball up the slope of the bowl. How steep is it ? does it get steeper ? Is the bottom of the bowl "cupped", causing the bike to naturally return to riding straight? That's "positive dynamic stability".

There have been a couple experiments where 2-3 identical frames have been built with one variable like tube manufacturer or fork rake and those articles, while inconclusive, are worth reading. One was in Bicycle Quarterly about 2010, and there was one in the 80s in a magazine called Bicycle Guide. Also, read Al Eisentraut's section on frame building in Tom Cuthbertson's "Anybody's Bike Book" which is a classic work if you can find it.

An ongoing discussion for sure but building spreadsheets of frame dimensions is not going to get you an understanding of how the various aspects of frame geometry contribute to the bike's feel and overall ride experience. Builders at the top of their game are able to adjust many aspects of frame design to get the finished bike to handle in a way that is pleasing to the rider and his / her intended use of the bike. All the variables (fork rake, tubing guage, chainstay length etc) work together. And don't overlook tires and tire pressure - they are a huge variable in terms of how a bike feels as you ride it.

Mark Petry
Bainbridge Island, WA USA

DaveSSS 

The differences are not that large, except for the wheelbase. You did not post the TT length or the stack and reach, to know that the frame will fit your body.

The Mr. Pink has quicker handling geometry.

You shouldn't expect a fat tire bike to handle the same as a road bike with racing geometry. I'd want more stability, which means more trail. Famous brands like Colnago use less HTA and more trail than many others. They handle just fine.

Looking at the all city website, I'd say that there are mistakes in the geometry table. You can't have different STAs with the same 58cm TT length and the same reach.

If the STA on the zig-zag is really 72.5, that could cause a tire interference problem, unless the chain stays were made longer.

AeroGut

I agree with this. I also can't figure out how the wheelbase could be so long given the other dimensions provided. If there isn't a dealer near you, you could try posting a question for anyone who has that bike to measure the dimensions for you to check against the published numbers.

More generally, if you want to visualize differences in geometry, the folks at 99spokes.com have a tool on their site that will create overlaid images of different frames. That wa you see exactly how the frames differ.

But as for which "feels faster", that depends a great deal on what you notice as a rider, which is fairly personal and not directly correlated with geometry. The subjectivity of feel is why you're getting a lot of non-answers to your question.

davidad

Find a touring bike like the Rock&road. most will allow for wide tires, fenders when necessary and carrying a load. As far as speed goes, the engine is the most important factor.

noglider 

This is not at all as crazy as it sounds. You might be able to sell for prices similar to what you pay, maybe even more. And you can sample lots of bikes that way. It might be quicker than coming to an understanding of how geometry works. Even knowing what a head angle or chain stay length does, you might make a decision and find you don't like it. So keep buying the dentists' bikes. That's basically what I do. I wait for a good value and then get rid of a bike I find I don't like. Since I build the bikes up myself, I save a bit of money, which allows me to own several bikes.

showlow

I've been doing this forever. Like, years and years. It's a great system. I've been able to try out so many bikes. I've also got a keen eye for a bargain, so I've lost track of how many people I've helped to buy bikes for over the years. 20+?

Anyway, like I said in my original post, what I'm looking for just isn't likely to come up used. I'm looking for a modern, fat tire, gravel friendly road bike (I want an Allied Allroad but can't afford one) that has a fast, road bike geometry, but manages to have some big tire clearances due to modern technology like disc brakes. That brought me to the All City Zig Zag, but when I tried to understand the geo charts and compared it to other bikes I've ridden, I found no consistency.

AnkleWork

<35mm is "modern, fat"? Can geometry make "fat" fast?

Well since you are blindly all up in love with a bike you've never ridden, plunk down some cash and get married. Just pay someone to measure your object of affection and copy it. You won't need to understand geometry to have a happy honeymoon.

BTW, if you carefully measured* the bikes you've owned you would know that published "geometry" is mostly marketing wank -- and that's what you're marrying.


* to more than one significant digit

79pmooney

I actually can get a pretty good idea of how a bike will feel from the geometry but it takes a) some work and b) years of riding, bikes that have fit me perfectly and decades of tracking those geometries (and a fork rake vs head tube graph that doesn't output trail but does give me a good idea how quick the bike will be.

I have used AutoCAD for years in my work and own an old high end copy. Many of my bikes, past and present are entered on to one drawing always using the bottom bracket as the reference point. I identified my contact points decades ago (seat and handlebars). When considering a frame, I input the geometry from the specs or my measurements. Calculate the weight distribution between the wheels. See what hoops I have to jump through stem-wise to locate the bars where I like them. Likewise the seatpost. I take the head tube angle and fork rake and go to my chart and see where that lies in relation to the line on that chart of angle vs rake that I like best. (That line calculates to trails that vary with headtube angle. I know we are all supposed to like "X" trail for everything but I don't. I have bikes on that chart with head angles from 75 degrees to shallow with a fork from the 1930s - 1973 Raleigh Competition with its geometry that was ancient when it was built.

I have designed two bikes from these drawings, had them built in titanium, not been surprised and love them still many miles and years later. But I could not do this for someone else, nor could I do it without the 35 years of observation and experience before that first ti bike. And none of this tells me what the tubes, materials, details and workmanship are going to feel like.

Ben

showlow

I give up. I'm just going to buy it because it's a pretty color and hope the marketing department isn't full of crap.

trailangel

Add this frame to your list:
https://blackmtncycles.com/frames/mcd-frames/

mpetry912 

I have personally known two (otherwise) very knowledgeable people who accumulated "lots of data" and ordered custom frames specifying every detail of frame angle, fork rake, tube guage, etc in the hope of getting their ultimate bike. The found a builder that would build their design.

and both were disappointed. One of those bikes has been food chained thru several owners here on Gilligan's Island, and each owner has managed to crash it. It has a nasty habit of "standing up" in corners. Prolly due to an odd combination of steep head angle, short trail and short top tube.

My point being that no matter how good you may be with your tape measure, and how many spreadsheets you create comparing geometries of various production bikes, you will not be able to design a bike that is better FOR YOU than that which an experienced builder (who has built 100s of frames) can create for you.

I would also challenge your assertion that (road bike geometry) + (fat tires) = (good gravel bike). Consider this. Since you are on gravel, you will want a somewhat longer trail than a road bike because you are "plowing" gravel rather than "rolling" on a hard surface. The contact patch moves forward on soft surfaces and you will find steering gets harder as you run out of trail. I had a conversation with Keith Bontrager about this years ago in the context of mountain bike design. Keith works for Trek now.

I recently received my "last bike ever" from master bike designer and builder Mark Dinucci. In the process of ordering my bike, there was NO discussion of tube lengths, frame angles, geometry, etc. ZERO. Mark simply got my measurements according to his own proprietary process, and built the bike to fit and perform according to his artistic vision and 40 years of experience in the industry. It is without question the best bike I've ever ridden, and I have ridden and own some really fine bikes. Several folks on this list have ridden it too and they found it to be very, very nice. Yes it does have tire clearance for 32mm tires and fenders (prolly could fit 35s) and it is without question a responsive, fast road bike. Looking at the CAD drawing Mark generated, it has a 71 degree head angle. Yes, 71 deg !

So my point is, thank about what you want from the bike, find a builder you can work with and who is familiar with the type of riding you want to do, and trust your builder! here in the Pac NW I'd suggest Corey Thompson.

Pick a color you can live with, and enjoy the ride.

Mark Petry
Bainbridge Island, WA USA

base2 

It seems to me that a simple fork swap would achieve the OP's objectives for a minimum of expense & risk.

My favorite bike came with 45mm of rake & 35mm tires. After a fashion I installed 23mm tires & it was too nimble for me at the time but that was no matter because the original fork broke. So I replaced the broken fork with one with 43mm of rake. I kept the 23's & it rode nearly the same as it did the day I bought it with 35's. (The product of trail was back to OEM spec)

Last year, I decided it was too stable so on a whim I installed a 47mm rake fork & kept the 23mm tires. I'd call it "twitchy" meaning super responsive but interestingly it's also more stable on account of wheelbase. Moreso than the high dollar road race bike I think. Which is what I decided was after. Now I swap between the 2 as weather dictates & there is a minimal of difference in ride as far as I'm concerned.

The difference is 6 pounds & $5000 between the two. My point is to support the above posters that endlessly searching geometry charts for the "holy grail" for such a thing that is by definitio is subjective as "feel" is unlikely to yield the results you expect.

Take your favorite bike, ask yourself: "In what way do not like how it handles?" & try a fork swap to that end. You'll either love it or hate it, but the barrier for entry is much lower & the potential upside is much higher.

Aaron

noglider 

You're right, I had forgotten the requirements you laid out, and those features are not available except in new bikes. But you might be flexible: disc brakes are nice, but I'm fine without them. 40mm tires are great, but you could put 32 or 35mm tires on lots of bikes. And you could wait a year or two until the features you want are on the used market. And what are the advantages of thru-axles? I haven't used them yet.

I recommend you test ride before you buy a new bike. As you know, they lose a lot of value on the first day, so it's important to like the one you buy. A test ride is better than an understanding of geometry.

showlow

Thanks for the response.

I would like to say for the record that I DEFINITELY know what I like. My favorite bike is a Lemond Zurich and it's fantastic for me. I've spent years tinkering and adjusting that bike and several others and I have zero complaints, overall. I also happen to have a Della Santa built Lemond from his earliest production and it's also fantastic. The thing is, I just have an expectation that, because of new tech like disc brakes and new manufacturing processes (carbon would be nice to try), that it's at least possible that I can buy a road bike that feels as fast as my Zurich, is lighter, and takes wider tires. Bikes like the OPEN UP and Allied All-Road advertise that this is possible now because of improvements in carbon manufacturing and disc brakes. Both are too expensive for me. The Zig Zag is beautiful to look at, steel, and for less than the price of an OPEN UP frame I can build a Zig Zag with a fantastic spec.

Anyway, I bought the frame. It's at my LBS now. Hopefully it lives up to the marketing hype!