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Old 07-06-09, 02:50 PM   #1
mpotapa
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Is there a way to make a bike faster?

My girlfriend has a trek 7.5 FX and I have a redline 510. Her bike is really quick and I have to peddle a good amount more then her to keep up with her. Any suggestions or am I out of luck?
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Old 07-06-09, 03:15 PM   #2
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I'm not sure what the Redline 510 is. If it's a mountain bike, you might try slicks rather than knobby tires on it. Otherwise, work out more, get a new bike, or ask her to slow down a bit.

It may be her that's quick, and not her bike.

Also, check your air pressure, make sure you're okay there. Make sure everything's spinning freely- pick the bike up and give the wheels a whirl, should be obvious if something's binding up or a brake is rubbing.
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Old 07-06-09, 03:41 PM   #3
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Switch bikes on a ride. Does the quickness shift over to you, or does she still kick your butt? There's your answer.
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Old 07-06-09, 03:48 PM   #4
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Is this it?
http://www.joebikeler.com/store/product/redline_r_510/

I would guess that most of the problem is how heavy it is and how huge the tires are (700 x 55?)
The gearing looks fine to me (28/38/48, 11-34). I had a hybrid geared like that and it was pretty quick. Besides, I figure the Trek has similar if not the same gearing.

If the tires are knobby, you can start there and swap them for smooth/slick tires.
Make sure they're inflated fully. Check if the brakes are rubbing. Assuming none of the bearings or wheel hubs are worn out, that's probably all there is to it.
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Old 07-06-09, 04:50 PM   #5
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Originally Posted by mpotapa View Post
My girlfriend has a trek 7.5 FX and I have a redline 510. Her bike is really quick and I have to peddle a good amount more then her to keep up with her. Any suggestions or am I out of luck?
You're out of luck.
The Redline 510 is a true hybrid. The Trek 7.5 FX is a flat bar road bike.
Hybrids are inherently slow. Flat bar road bikes are designed to be faster than a hybrid but not as fast as a traditional road bike.
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Old 07-06-09, 06:15 PM   #6
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I have to peddle a good amount
What are you selling, and how does selling something make a bike go faster?
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Old 07-06-09, 06:26 PM   #7
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I would say the Trek 7.5 FX is a hybrid - but the pendulum swings closer to road-bike than mountain-bike. All hybrids go a bit one way or another in this way. But the Trek 7.5 FX is a very quick bike. No match for a actual road-bike - a good one - but for a hybrid, it trucks quick.
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Old 07-06-09, 06:28 PM   #8
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The Redline is also a much more upright bike, so she is almost certainly in a more aerodynamic position than you are, with her torso probably tilted forward at 45 degrees.
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Old 07-06-09, 07:49 PM   #9
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Hope she waits for you at the top of the hills, and meantimes, enjoy the view.
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Old 07-06-09, 08:56 PM   #10
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Try using a narrower tire, down to 28mm width, with the tire pressures all the way to the max. Check bearing preload at the hub cones to make sure the cones aren't too tight.
The 7.5 has higher gearing as well.
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Old 07-06-09, 09:10 PM   #11
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Ride more ... outside.
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Old 07-06-09, 09:49 PM   #12
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You're out of luck.
The Redline 510 is a true hybrid. The Trek 7.5 FX is a flat bar road bike.
Hybrids are inherently slow. Flat bar road bikes are designed to be faster than a hybrid but not as fast as a traditional road bike.
What's "flat bar" mean?
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Old 07-06-09, 10:04 PM   #13
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Straight handlebar instead of the curved-under style used on a road bike.
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Old 07-06-09, 10:19 PM   #14
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Straight handlebar instead of the curved-under style used on a road bike.
Gotcha! That curved-under style bar is a "drop bar"? Bare with me guys... I'm getting it slowly but surely


While I've derailed the thread maybe I could ask another question about something I've seen discussed in this thread. What exactly makes one bike style so much faster than another bike style, especially when they seem so similar? I could understand tires making a big difference, but it seems as if subtle changes in the frame and handlebars (like the difference between a hybrid, cyclocross, and road bike) make a large difference in speed. I'm just curious how.
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Old 07-06-09, 10:57 PM   #15
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The main differences why some bikes are faster are in the frame geometry. Subtle changes in frame geometry can alter performance in huge amounts.

For instance: I have a Trek 1100 which I used to ride a lot. It's a 60 cm frame with a 57 top tube. The seat tube angle is 73.5 degrees. I now have a carbon framed Orbea Orca that I ride. It's also a 60 cm frame size but has a 59 cm top tube. The seat tube angle is 74 degrees.

The difference between the 2 bikes is astounding. On the Trek I averaged around 13-14mph on just about any ride over 20 miles. On flats I could maintain 23mph for around 2-3 miles before I would blow up and couldn't push the gears anymore.

The Orbea is a joy to ride. I can AVERAGE 19 mph over 25 miles on it over the same roads and I never get winded doing it.

Same frame size, different geometry.
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Old 07-07-09, 05:18 AM   #16
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That is amazing Rob, a half of a degree of difference in seat tube angle making the bike that much faster.
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Old 07-07-09, 06:05 AM   #17
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Quote:
Originally Posted by SteelCity View Post
Gotcha! That curved-under style bar is a "drop bar"? Bare with me guys... I'm getting it slowly but surely


While I've derailed the thread maybe I could ask another question about something I've seen discussed in this thread. What exactly makes one bike style so much faster than another bike style, especially when they seem so similar? I could understand tires making a big difference, but it seems as if subtle changes in the frame and handlebars (like the difference between a hybrid, cyclocross, and road bike) make a large difference in speed. I'm just curious how.
A big difference is aerodynamics. Recumbents are fast because much of the rider's body is horizontal. Time Trial bikes are fast because the rider leans forward on the front jutting aero bars to make the torso almost horizontal and keep the arms in a streamlined position. Racing bikes are fast because the handlebars are set lower than the seat to get the torso tilted far forward. Comfort bikes are slow in part because you sit upright in the wind.

Another issue is optimizing leg power. If you are leaning forward over the pedals you can push down harder using your body weight, and thus accelerate and sprint faster than if you are sitting upright. On a recumbent, that same effect is accomplished by having a brace behind your back.

A lighter bike is slightly faster to accelerate, and faster uphill, but a little slower downhill, and not much different from a heavy bike cruising on the flats.

High pressure tires (which are usually skinny) are a bit faster than low pressure tires (which are usually fat), but wide tires pumped up to high pressure are faster than skinny tires at the same pressure.

Slick tires are faster than knobby ones.

Small wheels accelerate faster than big ones, but don't have any weight advantage once your speed levels off. However, they are also slightly more aerodynamic than large wheels.

Aerodynamics and leg power (the first two) are the most important, and bike weight is somewhat important in really hilly conditions.

Last edited by cooker; 07-07-09 at 06:09 AM.
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Old 07-07-09, 06:23 AM   #18
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Optimize your aero. Slide the stem down as far as it'll go, then drop the angle on it (it's adjustable, right?) so it's parallel with the ground. Then flip the riser bars upside down so they drop down then pull back. Get 100psi road tires, no more than 32mm wide (1 1/4").

You reach the point of diminishing returns after that. So, if that's not enough to let you keep up, you'll need a new bike. WARNING!!! If you one-up her, she will one-up you and the arms race will be on! Which is to say, if you're gonna do it, you might as well go all the way now. Buying a $5K bike now will be cheaper than buying a series of $1K bikes.
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Old 07-07-09, 06:29 AM   #19
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What are you selling, and how does selling something make a bike go faster?

LOL! That was funny!
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Old 07-07-09, 08:10 AM   #20
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A lighter bike is slightly faster to accelerate, and faster uphill, a little slower downhill, and not much different from a heavy bike cruising on the flats.
I haven't thought about this in terms of bikes, but doesn't gravity accelerate all objects at the same rate, regardless of mass? Maybe it's a question of inertia or momentum?
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Old 07-07-09, 08:16 AM   #21
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That is amazing Rob, a half of a degree of difference in seat tube angle making the bike that much faster.
It's also the longer top tube, which stretches him out a bit, and thus puts his head lower, and there may be differences in tires, gearing and handlebar height that he didn't mention.
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Old 07-07-09, 08:26 AM   #22
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I haven't thought about this in terms of bikes, but doesn't gravity accelerate all objects at the same rate, regardless of mass?
If it were only gravity acting on it, then yes. But there is more to it, such as road friction and wind resistance, which I assume heavier weight will help power thru. Think of a bowling ball and a beach ball of the same size falling from high in the sky. I'm willing to bet the bowling ball hits the ground first.

Disclaimer: I'm not a scientist and the pay per hour motel I slept in last night was definitely not a Holiday Inn.
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Old 07-07-09, 10:09 AM   #23
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I haven't thought about this in terms of bikes, but doesn't gravity accelerate all objects at the same rate, regardless of mass? Maybe it's a question of inertia or momentum?
When falling yes, but bikes roll down a hill, so rolling resistence comes into play along with weight. For example, a heavy Hot Wheels car or a Pine Wood Derby car is faster on a steep decent track. The lighter car is normally faster on a track with a long level run at the bottom where it passes the heavier car. This illustrates the coasting effect with gravity and weight.

Many other factors are involved which someone in physics can describe.
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Old 07-07-09, 10:26 AM   #24
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rolling resistance would be slightly higher for a heavier bike (frictional force = mu*normal force). So that isn't it.

yes, something like a feather and a book fall at different rates, but that's due to air resistance. put the feather on top of the book and drop: they fall at the same rate.

the forces acting on two cyclists are the same: gravity, rolling resistance, and air resistance (ignoring internal mechanical inefficiencies). there is no difference in air resistance between two bikes, assuming they are of the same geometry. one could weigh 14 lbs, the other 30, and it's inconsequential to air resistance. as i said before, rolling resistance rises with weight. and gravity accelerates all objects at about 9.8 (m/s)/s.

even looking at in terms of kinetic energy, mass is irrelevant.
ke = 0.5*m*v^2
this rearranges to v = (0.5 ke/m)^0.5
which, assuming you are coasting from the top of a hill, is
v = (0.5 *m*g*h/m)^0.5 = (0.5*g*h)^0.5, ignoring energy lost from resistance.

where mass will come into play is just after the hill. the bike/rider combo with more mass has more kinetic energy (and momentum, if you choose to look at it that way), as they both are moving the same speed, but one has more mass. This means more work is required to stop the heavier bike. If both bikes continue coasting, the lighter one will stop first. This is also important if you want to brake very quickly. the lighter guy stops first.

Last edited by tadawdy; 07-07-09 at 10:46 AM.
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Old 07-07-09, 10:30 AM   #25
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You say that you have to pedal a good deal more than her in order to keep up with her, so you may want to look at your gearing. A larger chainring (up front) or a smaller cog (in back) will give you a higher top-end speed.

As the others have said, check your wind resistance and your rolling resistance. Are you wearing a big floppy shirt? Does your wheel rub against your brake?

Also, do you maintain your drive train? Is it noisy? Remember, every "squeak" out of your chain and gears is a little bit of lost energy.
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