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The Itch(10 posts)

The Itchsnapdragen
Oct 10, 2002 5:36 PM
Well, I'm starting to get the new bike itch. First of all I feel so left out---I only have 1 bike! (Well, I did give my mountain bike to my niece, she needed transportation)

So, I'm sure it's been talked about before, but could someone give me a general idea about the different frame materials. From what little I understand, I'm thinking I'll want another steel frame. But how does Aluminum, Ti, etc. differ? Are there differences in types of steel too?

I'm no racer, never will be. But I would like to improve my riding and speed -- new bikes make you faster right? ;-)
Big question. Starter answerfbg111
Oct 10, 2002 7:39 PM
Steel - heavy, absorbs shock & vibration (not sure how much, but more than aluminum), inexpensive.

Aluminum - light, stiff, harshest ride, inexpensive.

Titanium - light, stiff, absorbs shock & vibration, expensive but most frames seem to come with a lifetime warranty.

Carbon - lightest, stiff, absorbs shock & vibration, expensive.

For more detailed differences, somebody who has ridden a lot on these frames will have to educate you, as I've only ridden aluminum and have test ridden carbon.

If you want to a frame that will improve your speed, reducing weight is priority #1. Get a lightweight carbon or aluminum frame, or maybe a Ti one. (Carbon is lightest, not sure how Al and Ti compare by weight). After that, you can improve your acceleration (and to a lesser extent speed) with a stiffer frame. Stiffer frames flex less on each pedal stroke, especially when standing and accelerating, so less power is lost to transfer and more is applied to the pedal. Stiffness is a function of several things - material, frame geometry, tubing, and more.

I'm sure other, more experienced folks will weigh in. I've only been at it a few months. But in the meantime, here's a few links I've collected that you may find informative:

http://www.littletoncyclery.com/html/bike_basics.html
http://www.sjsu.edu/orgs/asmtms/artcle/articl.htm
http://www.sheldonbrown.com/frames/index.html
http://www.analyticcycling.com/ForcesLessWeight_Page.html
http://www.sheldonbrown.com/rinard_frametest.html
http://forums.consumerreview.com/crforum?viewall@@.efb7312
Reducing Frame weight to improve your speed?Spunout
Oct 11, 2002 3:44 AM
Okay, if you can reduce the weight ten pounds compared with what frame you're riding now, then you will be flying.

Seriously, the difference in a 4.5 lb steel, lugged frame and a 3 lb Aluminum/Ti/Carbon frame will not be noticed by the non-competitive rider.

MOre important: Fit. Comfort.
In my experience, yes.fbg111
Oct 11, 2002 4:49 AM
My first bike was a Giant OCR1, which I rode for 1 month. Then exchanged it for a lighter TCR2, and immediately registered a .5 mph increase in my average speed over my usual 20 mile course. The lighter bike accelerates better and I believe takes less energy to propel at the same speed over distance. Under 20mph, I believe weight is a factor. Over 22mph, I think aerodynamics and wind resistance becomes the most limiting factor. I could be wrong, as I've only been at this for a few months, but this is what I've observed so far.
in your case, could be other factorsweiwentg
Oct 11, 2002 5:35 AM
a) new bike joy (I'm serious! I know what it feels like, because I upgraded to a TCR myself!)

on a more serious note b) increased frame stiffness.

c) frame aerodynamics. specifically, the fork.

d) position. you probably had a lower position on the TCR.

e) you were just getting better.

f) if the course was hilly then yes, weight.

lesson learned: get the TCR :)
Good points, but...fbg111
Oct 11, 2002 6:47 AM
1) possibly. :D
2) probably.
3) same fork. TCR rear wheel is faired behind the seat-tube, and the OCR down tube is thicker. Maybe those have some aerodynamic effects. Otherwise they're pretty much the same.
4) Pretty much same position. Same seat height, lowered bars on both as much as possible. But maybe the OCR's head tube and stem are higher than the TCR's and I didn't notice. not sure.
5) possibly. But I jumped .5 mph on my first ride on the TCR, which is a bit of a coincidence. I could also just tell the difference, weight-wise, between the two bikes. TCR accelerated quicker and feels easier to maintain a slightly higher speed on.
6) no hills on my usual course.

How exactly does weight affect performance? Is there any scientific data on this? Stiffness improves acceleration and climbing, and to a lesser extent constant avg. speed. Weight certainly improves climbing and accel, but wouldn't it improve avg. speed too? I think there's probably a correlation curve with weight:speed, but how steep or shallow it is, I don't know. Certainly your speed will increase much more if your bike weight decreases by 10lbs as opposed to decreasing by 1.5lbs, and as bikes get lighter there's probably a point of diminishing returns where other factors like wind-resistance become larger factors. Wish there was some quantitative evidence for this, now I'm curious...
Did you get a new cyclocomputer as well?HillRepeater
Oct 11, 2002 7:38 AM
Or maybe a change in gearing? Running new tires with less rolling resistance? Better fit on the bike, maybe?

If you're on a flat course that doesn't have a lot of starts, stops or speed changes, weight is going to have almost no impact on speed. Weight is noticable during acceleration and climbing, but once you get the mass moving, weight has little impact on keeping it moving.

A lite bike is a joy to have, though.
Did you get a new cyclocomputer as well?fbg111
Oct 11, 2002 8:52 AM
Same computer, but perhaps different gearing. OCR had a triple, TCR has a double. Not sure what the ratios are though. Don't remember what tires were on the OCR, but the air pressure in them is the same = 120psi. Fit is same (both medium compacts, same stem length I think).

Actually, now that I remember my college physics courses, I can think about this more clearly. Objects in motion tend to stay in motion, unless acted on by a force. Such a force as rolling resistance, wind resistance, and internal mechanical friction. So theoretically, once rolling, the bike should continue rolling no matter how much it weighs, except as wind resistance, mechanical friction, and rolling resistance slow it down. Weight affects only rolling resistance. How much that contributes to slowing you down, I'm not sure, but I'm pretty sure wind resistance is the main force working against you, except perhaps at very low speeds. Also, rolling resistance depends on the weight of the bike + weight of rider. Combined, that's probably about 200lbs. Shaving 2lbs off that due to a lighter bike is only 1%. I wonder if that's enough to make a noticeable difference.
Good points, but...weiwentg
Oct 11, 2002 9:33 AM
well, in theory (www.analyticcycling.com) if it's pancake flat, decreasing weight will have no effect.
if you had to stop and start a lot, then the weight would have an effect. or even if there was a false flat somewhere.
I forgot the OCR had an aero fork. and I don't know how much aero effect the seat tube adds (can't be much, it isn't that great a fairing). another things to consider would be be spoke count and gauge, and rim depth. these are identical, however.
in short, no definite answer, but likely A) new bike joy. :)
Good points, but...fbg111
Oct 11, 2002 10:13 AM
Yeah, if you see my post above I realized that once you're up to constant speed, weight has little effect, and the higher the speed the less effect relative to wind resistance.

The aero seatpost actually has no aerodynamic effect whatsoever, and may even increase drag, according to wind-tunnel tests:

http://www.slowtwitch.com/mainheadings/techctr/compact.html

But they sure as heck look cool on a compact frame! Usually I don't go for form over function, but with all the recent talk of paintjobs and Italian panache and colored bar tape, I think I must be slipping!

However, I do stick by my assertion that I can tell the difference between the TCR and OCR. All it took was one sprint test ride to convince me to exchange the bikes. The TCR simply accelerates better. Whether that's due to increased stiffness or lighter frame, I don't know.