Need some experienced advice: can a few pounds of bike make this much difference?



river251

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Mar 4, 2011
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I spent a couple days comparing a Scott CR-1 ($3800) and Specialized Roubaix Elite SRAM Apex ($1800). The Scott is the SL frame, and has had SRAM Red and SRAM S30 wheelsets installed (not clear why but that's what it is). The Roubaix weighs in at a bit over 19 lbs, and the CR1 is 15 lbs. I'm 245 lbs, and am making this purchase to get back into lots of riding to lose weight and have fun.

The difference when comparing these bikes is very dramatic. When I get on the Scott and start pedaling, it's like it takes very little pressure to get going. Light pedal pressure. Like I'm starting downhill. When I get on the Roubaix and start going, it's like the cranks don't want to move, or I'm starting on an uphill or in quicksand. (tried different gears as the Roubaix has larger cogs on cassette).

Add my 245 to 15 lbs, and we're 260 on the Scott, 264 on the Roubaix. That's a 1.5% weight difference which shouldn't be noticeable as I ride around. I would say the difference in effort needed to get underway is more like 30% (I'm probably wrong but subjectively that's how I feel). They feel different all the time when riding, it's just most noticeable when starting off. The Roubaix is sluggish and effortful.

Is it the lighter wheels' inertia? Or just the overall weight? The cranks are carbon on the Scott and alloy on the Roubaix. Could it be crank stiffness?

I'm just baffled.

Thanks,
Jim
 

dabac

Well-Known Member
Sep 16, 2003
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Speaking about energy use, it's the weight of the whole package that's important, and even then, it's only when doing serious climbs and a lot of stop & go that it may have a real impact.
But us humans are buggers for noticing small nuances that are hard to capture scientifically.
You may well be faster on a bike that feels faster, even if all the easily measurable characteristics(weight, rolling resistance, frame stiffness etc) are very similar.

But, to cut 4 lbs out of a bike will require that a lot of parts will have to be picked for being lighter, which often coincides with being "nicer". You may be seeing that cumulative effect.

On top of that, if there's a thought behind the Roubaix name, you've gotta remember that that's a really punishing race (cobblestones and whatnot). It's just possible that a bike with Roubaix name is built to be a softer ride.
Rigid is good for power transfer, but if it knocks the rider into a pulp, then the bike won't be going anywhere anyhow.

It's really unlikely to be the material in the cranks making the difference.
"Stiff cranks" is better as a selling argument than it is as an explanation for why a certain bike/rider is faster.
 

kdelong

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Dec 14, 2006
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I agree with dabac. There are also a few other variables to take into account. The tires used on the bikes is one. Did both bikes have tires with the same rolling resistance? The Scott probably had a little higher grade of tire on it. Did both bikes have optimum tire pressure when you did your test ride? This alone could explain why one felt effortless to pedal whle the other felt like quicksand. How were you feeling when you did your test rides? Did you test ride the Scott early in the day and the Roubaix after work or in the evening? Were you riding on the same surface? Cement and asphalt give different impressions of rolling resistance. One or all of these factors, as well as what dabac puts forth, could have combined to effect your percieved pedalling effort.
 

jpr95

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Oct 11, 2010
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At your size, I still wouldn't go with the 15 lb. bike. It may feel faster and seem more fun at first, but you're going to tear the snot out of that bike. You're going to be hard on the wheels--spokes and rims both, particularly if you have a low cadence (larger folks tend to pedal slower in a larger gear ratio).

You might seriously consider looking for a used bike on Craigslist or in the classifieds to use until you drop a few pounds and then have a better idea of what might suit you for a longer term purchase.

Just some thoughts.
 

river251

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Mar 4, 2011
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Thanks for your thoughts and advice. I tried the bikes switching back and forth in early afternoon. I see people here saying take them for a 2 hour ride but I don't know any bike shop that will let you do that. Tires were equalized at 110. Maybe then it really was the bikes' different weights and had that effect.

Thanks
Jim
 

sitzmark

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Jan 12, 2010
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I'd side with the :cumulative effect". As much as it is written that $$ can't buy speed, it can buy "smoothness" and precision. The Red components have ceramic BB bearings and ceramic pulley bearings - the groupset is optimized for low friction. That has an effect. 4lbs can be felt in side-by-side comparisons. Pick up a 5lb dumbbell and propel it , then a 10lb - you can feel the difference in effort needed. Not huge, but perceptible. The S30 wheelset may be lighter and may have lower resistance bearings. If you've inline skated, you can tell the difference between ABEC3/5/7 bearings and rolling resistance. So again, little things that add together. A lighter bike tends to feel a little more nimble at slow speed/start up. As momentum builds and inertia factors in the difference in weight has positive and negative effects depending on terrain and other variables.

I like Scott frames - I have CR1 and Speedster. My wife has same. They are light and stiff, but I doubt the frame has much bearing on what you're perceiving. I run SRAM force on my bikes, my wife Ultegra/105. I perceive a difference, but more so with wheelsets. I swap Mavic Ksyrium, Zipp Team Issue, and Zipp 404 in my frames and each gives the bike a different feel. The Zipp hubs are just silky smooth and seem to roll smoother/easier. Never scientifically measured it, so it is a seat-of-the-pants thing only. My same course times are generally faster with the 404s, but on diffeent days and different conditions, so again uncontrolled data..

You're talking a couple thousand $ difference. For that you want to determine if the overall ride experience is worth the added cost. Can be difficult to determine at an average bike shop. Most are parking lot demo shops. A shop owner that is trying to build loyal, long-term customers is more willing to offer extended demos or rental so that you get a bike that is right for you and keep you returning for service and other purchases. This is not a "give-me-the-best-price-I-can-find" arrangement. Requires trust and investment by both parties.
 

AlanG

Active Member
Dec 26, 2010
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Originally Posted by river251 .
I would say the difference in effort needed to get underway is more like 30% (I'm probably wrong but subjectively that's how I feel). They feel different all the time when riding, it's just most noticeable when starting off. The Roubaix is sluggish and effortful.
Is it the lighter wheels' inertia? Or just the overall weight? The cranks are carbon on the Scott and alloy on the Roubaix. Could it be crank stiffness?

I'm just baffled.

Thanks,
Jim
I think there is something wrong here. Are you certain you were starting off in exactly the same gear on both? I would expect someone who is an experienced lightweight cyclist could see a small difference between your two bikes but would not expect you to see any significant difference. Could there be something wrong with the Roubaix? Did you try lifting the Roubaix off the ground and turning the wheels and cranks by hand to see if anything is stiff or rubbing? On even the very cheapest bikes the crank should spin effortlessly if the chain is off. The wheels should spin effortlessly too. With your weight, I would think most bikes will take about the same effort to pedal whether this is starting out or to keep going.

Before buying my Ultegra equipped carbon bike with carbon cranks, I rode quite a few bikes over a wide price range including some aluminum frames with Sora components and there was not that big a difference. I weigh about 160. My old heavier steel framed Giant Kronus with RSX components did not feel that much slower starting out than my new bike feels. Maybe you should consider testing some additional bikes.

I do concur with the other poster who suggested you consider buying a cheaper or used bike until you get your weight down some if you are concerned with cost vs. value at all. (Of course I don't know how much weight you feel you need to lose. There is a 300lb Redskins football lineman who is a rider in my area and he tries to not lose weight.) If buying an expensive lightweight bike can the store make sure that it is strong enough and stiff enough for you and will hold up? (I don't know much about this.)
 

An old Guy

Active Member
Feb 12, 2011
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A few weeks ago I did club century. I was going up hills putting out 350w and being passed by little old ladies on bikes much inferior to mine.

It turned out that my rear wheel was a bit loose and every time I pushed hard on the pedals the wheel would rub on the brake. The harder I pushed the harder it rubbed on the brake.

Lots of different mechanical issues can make a bike feel slow. Not much makes a bike feel fast.

Test the faster bike with and without 2 full water bottles. If you can tell the difference good for you. If not, the slower bike has some mechanical issue.
 

sitzmark

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Jan 12, 2010
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Originally Posted by AlanG .
Are you certain you were starting off in exactly the same gear on both?
Certainly a possibility. The Apex gruppo could be 130bcd 53/39 and the Red 110bcd compact 50/34. The standard Apex set up generally has a wider range cassette (long cage der/28t or 32t low gear), which would largely offset the effect of a 39 front ring. Sram Red is usually equipped with a 23t or 25t cassette, but many options up to 28t are available. In the "typical" Apex 130bcd configuration, the Apex equipped bike should have about the same or or less gear inches at start up as a Red compact, making the Apex easier to pedal. So many configuration options tho, so would have to look closely to know for sure.

As far a wieght, I started my riding at 220lbs +/- and my bikes have held up fine - about 4k-5k miles per season for past 2 seasons. Now riding at 185-190. I am more careful with the Zipp 404 wheels, slowing for things like RR tracks and rough road sections, whereas with other wheelsets I usually bunny hop them at speed. Frames are solid.
 

houstanrojas

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Aug 4, 2011
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It surely depends on your demands and all relevant information. Nothing can be said till you dnt provide full details and demands.
 

blackZEBRA

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Aug 13, 2011
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It also depends on your budget and how much you can comfortably spend.

I have a 18-19 lb alum bike and rode a friends carbon 16 lb bike. It was noticabilty stiffer and power transfer was a lot better then my AL bike. but his bike costed 2k more then mine did.

You also have to consider that Carbon frames fatigue over time (depends on your riding) and needs to be replaced after a certain amount of years for safety reasons. If I had money to spend on a new frame every three to four years, i'd def go with Carbon.
 

AlanG

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Dec 26, 2010
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Originally Posted by blackZEBRA .

You also have to consider that Carbon frames fatigue over time (depends on your riding) and needs to be replaced after a certain amount of years for safety reasons. If I had money to spend on a new frame every three to four years, i'd def go with Carbon.
I think you may be off track here based on what I've read about carbon bikes being stronger and being less prone to fatigue.

http://www.calfeedesign.com/tech-papers/technical-white-paper/
 

davereo

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Jun 17, 2010
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Just my .02. I have two road bikes a CAAD 9 53/39 double and 12-25 cassette and a Synapse carbon 50/34 compact and 12-26 cassette. 99% of all my riding starts out in my driveway so all my rides are basically the same conditions when starting out. I find that the compact group feels like it takes less effort to get the bike moving vs the standard double. This is definetly the result of being in a lower gear. This is where the difference ends. Once I am out riding and settle in to my desired level of resistance I am using the same gear ratios to propel the bikes along. All of my measured results distance and times are closely related regardless of what bike I choose to ride. So with that said I would not base my selection of a new bike on how easy it was to get moving. Once you have the bike moving along which one was the most fun to ride. The Synapse is easier to push up large hills the CAAD is more stable charging down them ect.... Find out what you really want from your riding and go out and get your bike. Go to a few more shops and try out others in your price range. Look to a shop that allows your to go around the block a few times instead of just the lot.
 

dabac

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Sep 16, 2003
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Originally Posted by blackZEBRA .


wow, thanks for the reading material.

a friend who races in the pro 1 and 2 category told me that CF frames only last X amount of years. He switches out frames every other season.

But here's where you have to differentiate between the design and the material.
If you're racing, you'll be chasing every possible advantage you can get (that's still within your budget). If there was a race advantage to a bike that would literally spontaneously self-destruct moments after passing the finishing line, some riders would certainly go for it.
Now, this is obviously an extreme case. UCI rules puts a stop to some of it, and necessary design margins is another limiter. Most of the time, a 2nd place is better than a DNF due to equipment failure.

I'd have no qualms about riding a somewhat chunkier CF part year after year, but I'd be wary about extended use of really sleek racing parts regardless material.