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What is an "aggressive" geometry?

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What is an "aggressive" geometry?

Old 03-12-13, 07:55 AM
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What is an "aggressive" geometry?

I hear this term a lot without fully understanding.Is an aggressive geometry one with a higher seat relative to the drops and a longer top tube relative to the seat tube for a more stretched out riding position?My road bike is a pure Italian racing bike from the 80s.I assume the geometry is aggressive am I right?Is aggressive synonomous with less comfy?
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Old 03-12-13, 08:04 AM
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Usually people talk of an aggressive riding position when they are looking at someone who is more aero - stretched out, big saddle to bar drop, as you describe. Classic racing frames from the 80s would naturally put you in a fairly aggressive position, though in general even "racing" bikes were ridden with less drop from saddle to bars than is common now.

As for aggressive being synonymous with less comfy, that depends what you like and are used to. People who are used to riding in a relatively upright position on hybrids or touring bikes find it difficult to believe that one can be comfortable on a racing saddle, riding with a flat back and stretched out in the drops. But one can.
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Old 03-12-13, 08:05 AM
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Originally Posted by trek330
Is aggressive synonomous with less comfy?
That's the usual tradeoff for the racer types, but I don't know the particulars.
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Old 03-12-13, 08:22 AM
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The most dependable indication of aggressive bike frame geometry is head-tube angle. Any angle 73.5 degrees or more is considered to be aggressive on a midsized frame. Good framebuilders will increase the headtube angle on larger sizes to mitigate the longer wheelbase on the larger sizes.

A steeper headtube angle makes the steering more responsive. This is important in pelotons where many small adjustments are quickly made to avoid other racers.

Don't confuse aggressive geometry with bike fit. It's possible to have a bike with aggressive geometry and still have the handlebars above the saddle.
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Old 03-12-13, 08:32 AM
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Aggressive = shorter wheelbase and steeper frame angles.

For me, the most suitable bikes are either touring bikes or ca. 1960 to 1980 racing bikes.
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Old 03-12-13, 08:43 AM
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If the rear tire is real close to the seat tube... that's a sign of short wheelbase.

Rake and trail of the fork is what is really important.
Look/see... https://davesbikeblog.blogspot.com/20...le-bit-of.html

Hope that helps but there is alot out there if one searches.
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Old 03-12-13, 09:11 AM
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I think the combination of the above posts are about spot on. The geometry has steeper angles, the fork rake puts the trail back. The overall wheelbase is shorter, usually because of shorter chain stays. Keep in mind that "geometry" being aggressive is different than an aggressive "position" on any bike. I can create a relatively relaxed position on my touring bike or a more aggressive position. However, there are limits to overall agressive positions based on the bike's geometry.
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Old 03-12-13, 12:31 PM
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Just found this in our garage. https://yojimg.net/bike/web_tools/trailcalc.php

Fun to throw in different data and see what ya git.
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Old 03-12-13, 01:56 PM
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Originally Posted by pursuance
Just found this in our garage. https://yojimg.net/bike/web_tools/trailcalc.php

Fun to throw in different data and see what ya git.
That is a nice tool :-)
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Old 03-12-13, 02:07 PM
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Track geometry would be considered aggressive. It usually comes with STA at 75 or steeper, HTA greater than 74 and shorter HT lengths. Also, the chainstay length is usually shorter than what would be normal for a road race bike. A bike like the Specialized Tarmac would be standard road race geometry. IOW, slightly more relaxed angles than a track bike, with a slightly longer wheelbase. There are many combinations of the road bike geometry, from steeper more crit oriented bikes to more relaxed endurance bikes. All would fall within the genre of a race bike. Beyond the race oriented bikes would be the touring models. These have yet more relaxed angles, taller HT lengths and longer wheelbases which include longer chainstays and trail. Each bike serves it purpose. Can you ride a track bike on the road? Yep. Can you ride a touring bike in a crit? Probably, though expect the other riders to avoid you like the plague! lol
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Old 03-12-13, 02:49 PM
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Too Much replacement T Hormones; Down on all 4's snarling and pulling on your chain. ??
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Old 03-12-13, 06:24 PM
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Originally Posted by John E
Aggressive = shorter wheelbase and steeper frame angles.
Minimal fork rake often went hand-in-hand with this, too.
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Old 03-12-13, 06:40 PM
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Originally Posted by pursuance
Just found this in our garage. https://yojimg.net/bike/web_tools/trailcalc.php

Fun to throw in different data and see what ya git.
That's pretty cool. What else do you have lying around in your garage?
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Old 03-12-13, 08:11 PM
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These days most recreational or "sport" bikes duplicate the frame angles and wheelbases of serious road racing bikes. So the most significant criteria are long top tube and short head tube.
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Old 03-12-13, 08:18 PM
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Originally Posted by CraigB
Minimal fork rake often went hand-in-hand with this, too.
By that criterion a Trek 1.2 would be considered aggressive.
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Old 03-13-13, 07:24 AM
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high trail, steep head tube and seat tube angles, short chainstays, short wheelbase, high bottom bracket (small BB drop).

Aggressive riding position is where the handlebar tops are significantly below the saddle top.
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Old 03-13-13, 07:49 AM
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Originally Posted by Road Fan
high trail, steep head tube and seat tube angles, short chainstays, short wheelbase, high bottom bracket (small BB drop).

Aggressive riding position is where the handlebar tops are significantly below the saddle top.
Yes, as others have noted in this thread as well, it is critical to distinguish between aggressive geometry and an aggressive riding position. I get the latter to some extent on my extremely non-aggressive UO-8, which has a 72-parallel classic touring geometry, by raising the seat on a small frame with a long head tube.

The high bottom bracket is fashionable for criterium bikes, to permit pedaling through turns.

For the average rider, what really counts are tire clearance, which dictates one's choice of tires, steering stability and sensitivity, bottom bracket flex, and resilience on bumps. As always, the secret is to find a rider-specific and application-specific sweet spot compromise among conflicting engineering design goals.
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Old 03-13-13, 08:47 AM
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Originally Posted by John E
For the average rider, what really counts are tire clearance, which dictates one's choice of tires, steering stability and sensitivity, bottom bracket flex, and resilience on bumps. As always, the secret is to find a rider-specific and application-specific sweet spot compromise among conflicting engineering design goals.
Amen
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Old 03-13-13, 11:19 AM
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Originally Posted by oldbobcat
By that criterion a Trek 1.2 would be considered aggressive.
Taken solely on that criterion, most all non-specific (non-CX, non-touring) recreational road bikes today are aggressive. Compare your "average" fork today to ones from the '80s. Back then, minimal rake was seen on what were loosely termed "criterium" bikes.

But, it really all needs to be taken together as a package, along with the rest of the frame geometry.
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Old 03-13-13, 11:34 AM
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Originally Posted by John E
Aggressive = shorter wheelbase and steeper frame angles...
Aggressive = a bike that exhibits violent front wheel side-to-side oscillation, (i.e., 'death wobble'), on high-speed freewheel descents.
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Old 03-13-13, 03:14 PM
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Originally Posted by oldbobcat
These days most recreational or "sport" bikes duplicate the frame angles and wheelbases of serious road racing bikes. So the most significant criteria are long top tube and short head tube.
That describes my PRE rather accurately. The Trek 460 is touted as an entry level offering chiefly due to the True Temper frame (non-531) and suntour components. But the geometry is finicky compared to that PRE.

Both have nearly same wheelbase but it's the top tube where they differ. I know they are older but still very competitive, aggressive and responsive. Oh and fun to ride .
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Old 03-13-13, 03:43 PM
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Fixie hipsters love "aggressive".
Ghoulies higher than ears while riding
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Old 03-13-13, 03:56 PM
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Do note "Agressive" geometry does not equate to instability. My Habanero classic road bike with 23mm tires on it runs straight as an arrow down the road, is very forgiving, descends in a very confidence inspiring fashion, and goes through corners and climbs much nicer than my touring or cyclocross bikes.
A well engineered bike with the correct tubing for size will be stable and enjoyable regardless of "aggressiveness".
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Old 03-13-13, 07:58 PM
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Originally Posted by John E
Yes, as others have noted in this thread as well, it is critical to distinguish between aggressive geometry and an aggressive riding position. I get the latter to some extent on my extremely non-aggressive UO-8, which has a 72-parallel classic touring geometry, by raising the seat on a small frame with a long head tube.

The high bottom bracket is fashionable for criterium bikes, to permit pedaling through turns.

For the average rider, what really counts are tire clearance, which dictates one's choice of tires, steering stability and sensitivity, bottom bracket flex, and resilience on bumps. As always, the secret is to find a rider-specific and application-specific sweet spot compromise among conflicting engineering design goals.
That's just the way I was thinking it! I can't use an aggressive riding position even on my fairly aggressive Mondonico. When I'm positioned right on it I'm about as comfy as on my UO-8 or Terraferma.
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Old 03-13-13, 09:13 PM
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Originally Posted by TiHabanero
Do note "Agressive" geometry does not equate to instability. My Habanero classic road bike with 23mm tires on it runs straight as an arrow down the road, is very forgiving, descends in a very confidence inspiring fashion, and goes through corners and climbs much nicer than my touring or cyclocross bikes.
A well engineered bike with the correct tubing for size will be stable and enjoyable regardless of "aggressiveness".
I wouldn't consider your bike to have aggressive geometry. It's just plain road geometry.
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