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Please explain how the geometry of road bike frames have changed over the decades..

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Please explain how the geometry of road bike frames have changed over the decades..

Old 10-24-15, 06:59 PM
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exmechanic89
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Please explain how the geometry of road bike frames have changed over the decades..

Hey everyone, as I've mentioned before I just got back into riding about a year ago. I and my wife have been mostly riding hardtail mtbs I've converted to trail/street bikes (hate the term 'hybrid' for us). I also have an '88 Peugeot Triathlon road bike I just picked up a few days ago - shown in another thread of mine.

Anyway I was hoping some of you that have been around for a while might explain to me how frames (geometry-wise) have changed over the years, and why. For instance my Peugeot has the classic (old fashioned?) triangle frame design, with a horizontal top tube, a raked fork, and pretty short chain stays. But most modern road frames now have a sloping top tube and a long seat post. What does this accomplish exactly and does it make sizing different? Also the forks often have straight blades with no rake at all, I'm guessing for quicker handling?

Just too add I'm not a retro-grouch. As much as I love older bikes - both mountain and road - I like the new designs too. I think of this as a golden era to live in bike-wise, with lots of cool new designs and technologies, as well as access to older bikes at great prices.
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Old 10-24-15, 08:18 PM
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These are largely cost-saving measures for mass-production bicycles.

The modern style "compact frames" with sloping top tubes allow manufacturers to offer fewer sizes while accommodating a wide range of body types, at the expense of a longer, un-braced seat post in larger frame sizes. Straight-blade forks eliminate a production step (raking the fork blades) while retaining the steering geometry of a raked fork, at the expense of some shock absorption.
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Old 10-24-15, 10:02 PM
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Yeah, the sloping top tube allows lots of standover height for a wider range of riders.

There was a trend to "integrated seat posts" a few years ago. The frame extended upward, with a very short fitting on the top to hold the saddle. It was supposed to be stiffer and lighter. But it didn't sell, probably due to having to cut it to fit and then the rider was committed to a small range of adjustments.

The forks still have rake, the straight blade angles forward from the steerer tube. The older steel forks follow the axis of the steerer, then bend forward. The straight blades are a styling thing, it looks pro, I suppose. They all have "aero" cross sections, too. And with carbon forks, the design of the fork blades determines how stiff or flexible the fork is.

Comparing frames:
Most bike geometry charts will have "effective top tube", which measures the distance a horizontal top tube would take.

But I looked at "Stack" and "Reach" when comparing some new bikes last year. It makes it quite easy to see the differences of where the handlebars will go on two different frames. Or how many stem spacers and what different stem length to match an existing bike.

~~~~~

The best of the new trends: (in my opinion, of course.)

Shallow drop handlebars are fairly new. They started as aftermarket bars, but now many or most bikes come with them. The shorter reach to the drops works very well for me. I can ride in the drops a long time now.

Wider tires are very common now. 25c instead of 23c, and some bikes are even wider. And wider rims allow even more air volume in the tires. So riders can have lower air pressure for smoothing rough roads. Rolling resistance is still low, and the slightly higher aero drag from wide tires isn't critical for most riders.

Electronic shifting is very nice. (It's still expensive, though.) The buttons are like clicking a mouse. I have instant, precise shifts in the back even when climbing. And the front shift is fast with no drama. On rolling terrain, I'll shift the front even for very small hills, where I wouldn't take the trouble to do it on mechanical shifters.


The jury is still out:
Disk brakes -- I'm not sold on them yet. But some riders really like them. The mechanical disk brakes would often squeal on other rider's road bikes. They seem a little better now. I mostly ride when it's dry, and rim brakes work great and are very lightweight. (Disks are good with carbon rims, which don't brake as well with rim brakes.)

Press fit bottom brackets These can make a stronger, lighter frame and they look good. The frame might be a little cheaper to produce, too. But pressing in the bearings can cause creaking and wear problems. It's probably here to stay.

Last edited by rm -rf; 10-24-15 at 10:29 PM.
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Old 10-24-15, 10:03 PM
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Along with the economic element mentioned above, there have also been massive changes in materials used in the frames and how those materials are fabricated. E.g., a manufacturer's rep once stated that there were over 200 pieces of carbon fiber in differing weaves and densities that went into the construction of their better frames. That level of variability allows for some interesting frame designs (tri or time trials frames). Also, the dampening ability of carbon makes some of the old design requisites less necessary in terms of compliance and smoothness, so fork design, rear stay design, and tube profiles. A lot of freedom has been opened up by materials.

That said, if I'm going to be on roads or path/trails, I almost always hop on my 1985 Gazelle.
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Old 10-24-15, 11:00 PM
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The greatest change has been to proportional-sized frames.

On my old Lemond Zurich, with the long top tube, I felt stretched out and was never comfortable.

My new GT Eightball with a proportional top tube, feels right and the bike fits me like a glove.

The other notable change is the transition to wider tires.

I run 40 c tires on my new bike. On my old bike, I ran 23 c tires.
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Old 10-24-15, 11:25 PM
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I have one lemond tourmalet 2002 57cm. My height is 5` 7" and my inseam is 32" That bike is too big for me? The handlebar is 46 cm but in my other road bike i have 42cm handlebar is feel much better. And is 56cm. or 54cm is better for my height?
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Old 10-25-15, 01:20 AM
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Originally Posted by bobbyl1966 View Post
I have one lemond tourmalet 2002 57cm. My height is 5` 7" and my inseam is 32" That bike is too big for me? The handlebar is 46 cm but in my other road bike i have 42cm handlebar is feel much better. And is 56cm. or 54cm is better for my height?

I'm the same height. They were sold only in odd sizes. I have a 30" inseam and I would go for a 53. You would feel at home on a 55.
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Old 10-25-15, 02:15 AM
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I disagree that compact frame design was a production economy move. It was popularized by Giant in the early 90's on their top race bikes as a performance enhancement: shorter tubing runs resulting in less flex and tighter handling.
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Old 10-25-15, 05:43 AM
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Thanks for those indepth replies. I have to say things have changed massively since I worked in shops in the 80's. So many new and often proprietary designs, and so many smaller companies now making parts and bikes. I'm seriously blown away, lol.

A few comments I wanted to add, when I first saw compact frames I really didnt care for them, but I now have to admit the design probably works better than the traditional triangle shape. On all my 90's era mtbs I've been forced to buy shorter stems, and truthfully even my 'new' '88 Peugeot could use a shorter stem, as I'm pretty stretched across it - and I have a long upper body, I can imagine the situation for someone with a very short upper body. Also the compact frames should be stiffer I would think - a good thing for sure.

One thing I dont care for though is how massivley short the wheelbase has become on modern frames. What manufacturers now call 'touring' used to be considered a short race/performance frame, and the actual peformance frames are so short it seems like they would be pretty uncomfortable on a long ride. To me this is classic bicycle manufacturing 'çhange for the sake of change' design. Of course I havent ridden a modern frame so I might feel different when I do.

And yes, as I often say to my wife, it's material science that has really changed things up. Not just in bicycles of course but almost every other machine/device. Carbon frames in particular have evolved into absolutely incredible works of art - super light, yet super rigid/strong. Compared to the early days of carbon frames when some tubes were glued together it's just amazing to me. Also I'm very surprised to see carbon used in just about every part now - cranksets, bars, stems, seatposts, etc. Never thought that would be possible.
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Old 10-25-15, 07:18 AM
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I buy the lemond used. The person had the bike is had one lemond 55 cm and is had columbus steel frame. i have forget what model is was. I deside not buy that bike the 55cm because is was 8 speeds i buy the bike with the 9 speeds the 57cm. Maybe i should buy the 55cm. That two cm difference in my bike other than feel little big and the handlebar too is can affect perfomance? I have do sprint with the lemond in flat bike trail i do max speed 27 miles i do tried pass the 30 miles but i could finally. I wonder if i had 55cm if i do higher max speed
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Old 10-25-15, 07:19 AM
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carbon fiber is worth to buy? And what carbon fiber bikes is good today. What about the carbon fiber frames from china is worth to buy?
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Old 10-25-15, 07:57 AM
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Originally Posted by chaadster View Post
I disagree that compact frame design was a production economy move. It was popularized by Giant in the early 90's on their top race bikes as a performance enhancement: shorter tubing runs resulting in less flex and tighter handling.
Giant may say that, but the rest of the industry seems to think it was a change that allowed them greater efficiency by making fewer frame sizes.
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Old 10-25-15, 07:59 AM
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I dont know about the "decades" part but losing a bike off a roof rack can change a geometry in less than 2 seconds.
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Old 10-25-15, 08:03 AM
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Originally Posted by bobbyl1966 View Post
carbon fiber is worth to buy? And what carbon fiber bikes is good today. What about the carbon fiber frames from china is worth to buy?
Carbon fiber is pretty great. Usually, it makes for a light and stiff frame that isn't as harsh as aluminum.

Carbon fiber from China can be legit; most major bike manufacturers have carbon-fiber facilities in China.

HOWEVER

OPEN MOLD, NO-NAME carbon fiber from China is a gamble. You have no clue who designed or made that frame, and no clue if the frame was actually tested. The seller will not support the product post-sale, so you're on your own if something goes wrong.

Some folks have good luck with no-name carbon from China, others get a frame that's way heavier than advertised, others get a frame that rides like garbage, and others have the frame disintegrate underneath them.

Buy your bike from a seller that will guarantee it and support it in your country.
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Old 10-25-15, 08:11 AM
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If you go way back, back before WW2 the frames resembled what the general population rode ,search out pictures of the 20's ..

rather like Dutch traditional bikes are now.. just stripped down, drop bars and glued on Light Tires ..

much more about the riders than the tech of the bike companies.
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Old 10-25-15, 08:42 AM
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i have now steel bikes and aluminum road bikes. carbon fiber no have ride never. and i hear so many not good thinks for carbon like cracked frame i not have deside yet for carbon and for not racer steel bikes or aluminum is not stay good? I have one canondale R300 aluminum frame and with that bike i have pass carbon fiber and titanium bike. I not ride much i am bussy and this two riders looks like do many miles very often
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Old 10-25-15, 03:36 PM
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Originally Posted by NormanF View Post
The other notable change is the transition to wider tires.

I run 40 c tires on my new bike. On my old bike, I ran 23 c tires.
That kind of tyre increase is 100% rider preference, not a change in design philosophy.
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Old 10-25-15, 04:41 PM
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Originally Posted by bobbyl1966 View Post
i have now steel bikes and aluminum road bikes. carbon fiber no have ride never. and i hear so many not good thinks for carbon like cracked frame i not have deside yet for carbon and for not racer steel bikes or aluminum is not stay good? I have one canondale R300 aluminum frame and with that bike i have pass carbon fiber and titanium bike. I not ride much i am bussy and this two riders looks like do many miles very often
Bikes dont make you go fast, YOU do. It's mostly the rider that makes a bike fast or slow, so I would worry more about riding than what kind of bike I had..
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Old 10-25-15, 05:21 PM
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Originally Posted by Tim_Iowa View Post
Giant may say that, but the rest of the industry seems to think it was a change that allowed them greater efficiency by making fewer frame sizes.
That notion keeps getting mentioned. I don't know if that's true initially but most manufacturers produce a large number of sizes now. If you compare old versus new number of sizes, it's not much different.
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Old 10-25-15, 06:15 PM
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I have seen difference not in my bikes but when i use different size crank and cassette i see difference in hills.
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