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frame geometry vs handling, upright geometry ok on a race bike?

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frame geometry vs handling, upright geometry ok on a race bike?

Old 01-07-12, 10:32 PM
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Nick Bain
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frame geometry vs handling, upright geometry ok on a race bike?

can you tell how a bike handles by looking at the top tube angle?

I would like to generalize that the more slopped a top tube is, the more twitchy or quick it can turn.

Conversly it seems a parallel top tube is slower in response but tracks more straitley.

I bought this 2010 base level tarmac rival last fall, but Im not sure I like the slopping top tube, it seems to take more effort to control the bike on group rides.

Do you consider the Tarmac base model to be a valid road race machine?
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Old 01-07-12, 10:34 PM
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Nope. HTA, front/center, wheelbase are better indicators of handling than top tube slope.

If it seems like too much of a handful, try a longer stem. Wider bars. Lower bars. Bigger tire on the front than in the back.

Steering damper. (just kidding about that one, but might work for ya)

Totally valid road race machine.

Originally Posted by Nick Bain View Post
it seems to take more effort to control the bike on group rides.
more effort than what? Do you also have a horiz. top tube bike?

Last edited by LesterOfPuppets; 01-07-12 at 10:40 PM.
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Old 01-07-12, 10:48 PM
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mine caad 8 is pretty close. Also raleigh R700, raleigh persuit, fuji royale, raliegh grand prix.
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Old 01-07-12, 11:00 PM
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Some sizes of the CAAD8 are half a degree slacker in HTA than the Tarmac, which could increase stability. Not gonna look up geo charts on the others.

For me the biggest twitch inducer is having too little weight on the bars. A lotta times if the front end is getting squirrely I just put my head down.

My DB road bike is slacker than my Pinarello. Has a shorter stem also. Front wheel feels all floppy at lower speeds but get it up to about 30 and you can barely turn the wheel (exaggeration, but that's what it feels like cuz it's just tracking super straight and solid). Pinarello doesn't have that floppy feel at low speed. Up around 30 you don't want to make any steering input whatsoever, because it will respond to it.

Pinarello is obviously a more "valid road race machine" but the Diamond Back is one that steers itself so you can be really sloppy and it still goes in a straight line.\

Just gotta add, I'm pretty sure you could take your Tarmac to a carbon specialist and have them make the top tube level and it would still handle almost exactly the same as it does now.

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Old 01-08-12, 01:26 PM
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Originally Posted by Nick Bain View Post
can you tell how a bike handles by looking at the top tube angle?
No, you can't. Top tube angle has no effect on handling.

Head tube angle and fork trail (called "rake" in bicycles) have the most effect on steering quickness. 73-74 degrees head tube angle is typical for road bikes. MTBs use 69-72 for more stability. Larger numbers result in quicker steering, smaller in slower steering. Fork rake is usually 43mm on most road bikes. More fork rake means less trail which means less self-centering force (think of a shopping cart caster). Wheelbase also has an effect- longer causes slower handling- as does stem length and handlebar width. A short stem or narrow bars makes the steering feel quicker because it takes less hand motion to turn the front wheel a given amount.

If the Tarmac's a handful, Lester made some good setup suggestions. But mostly, you need to learn to relax your upper body. Make sure your elbows are bent. If you ride with locked elbows every bump will throw you off your line.
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