Bacciagalupe

I've been riding an old (as in, downtube shifter old ) entry-level road bike for a few months, and picked up a cross bike (Surly Cross-Check) a few weeks ago. I've kitted it out with 120psi 25c's, but on the stock rims.

So far the cross bike is far more comfortable and rides more stable than the road bike, but it also feels slower. That worthless measure known as the "average speed" on the cyclometer suggests they are the same. And from what I know, there really shouldn't be a significant difference between the two.

Since I don't have a power meter: Is there a way to figure out whether one bike is more efficient than another? Is this just a road-feel thing, or a genuine loss of efficiency due to other factors (geometry, wheels, tires, familiarity with the position)? Or would any type of real-world test run into too many variables to present an accurate assessment?

mayukawa

Most of that will be in aerodynamics and drive-train friction.

merlinextraligh

my guess is the wheel/tire combination on the Surly is heavier than the Road Bike's.

Heavier wheels make a bike feel slower. (I understand the actual power difference to spin up a set of wheels that are say 1/2lb heavier really is pretty small, but it definitely affects the subjective feel of the bike.)

oilman_15106

Nothing other than a feeling that the lower rolling resistance any part has, as in the hubs of the wheel, the more efficent the bike will be.

Bacciagalupe

Well.... Aero is about the same, as my body is in pretty much the same position on both bikes. Any particular aspect of the drive train? The cross bike is brand new, so the drive train is in about as good a shape as it will ever be in.


This is my current guess as well, although I'm not sure how to test that fine theory other than to buy a different set of wheels. I *think* the older road wheels with 23c's are 3 or 4 ounces lighter. The rims are definitely wider on the cross bike, so I doubt I could put 23c's on them.

I'm also figuring that some of the "slower feeling" is from the long wheelbase, which produces more stable handling. I prefer that, even if it winds up making the bike feel a little less snappy.

My main concern though, is: Is the difference is real or merely perceptual?

Bacciagalupe

I'm reviving this thread from the depths, as I never quite figured out what I was originally looking for, namely:

Without using a power meter, is there an objective way to reasonably determine whether one bike is, in fact, more or less efficient than another?

I'm especially confused as I've made several changes to the Surly -- like adding racks and fenders, and raising the bars -- that in theory should slow it down. It seems about the same, though, so I'm itching to figure out if the Surly really is slower....

StephenH

Maybe double-check the calibration on the speedometers to make sure that isn't throwing you off.

A friend of mine mentioned that one of their bikes would coast noticeably farther than the other. Not sure what that shows exactly, but if there is a big difference in aerodynamics, that might demonstrate it.

Maybe pick out a good course, and just alternate riding the two bikes over it as fast as you reasonably can on different days and time yourself. Your speed will probably vary a lot from one day to the next, but over time, it ought to average out pretty well and show you which bike is doing what.

I don't know that efficiency is really the quantity being measured here. Things like having different gearing on the two bikes would make them feel different to you, and surely affect performance somewhat, but wouldn't really be a matter of efficiency, either.

weavers

ride your bike to work, or on a typical route you like, for atleast two weeks or months. alternate them each day. note the real world time it takes, traffic lights, weather and how you feel makes for huge impacts on time, but you should see a general differnce. try to pick something more than 5miles, really a +20mile is probably better with lots of flat straight road, but its really what you ride daily that is important.

keep in mine that CX bikes are gonna be heavier than road bikes atleast 5lbs. thats for durablity more than anything cause its supose to go a bit off road and onto gravel/paved roads, but still go faster than a mtb. my mtb seems horrbile slow compaired to my road bike. riding my road bike to work/school if just more fun and enjoyble, even thought its just three miles. any trip over 10miles its road bike no matter what. 20lbs of alum/cf frok >>>>40lbs of steal and front shocks. for me anyways. i like my road bike cause when i wanna get up and go i can, where at the mtb it feels like i top out at 15, maybe 20mph at a full sprint, but the same sprint on a road bike gets me 25-32mph.

also you could put the road bike wheels on the cx bike. it should fit, see if that makes a difference in feel.

Bacciagalupe

StephenH: Yep, they're calibrated.... There is a nearby loop, just hoping to figure out some additional measures that would eliminate or manage some of the variables. In particular I'm curious if there's a way to correlate heart rate and bike speed.


Weavers: Yeah, I may try swapping out the front wheel; right now wheel type is just about the only thing I can imagine that's impacting performance.

However, the kicker is: How would I definitively determine that it's the wheel, and not some other variable, that makes a difference? MTB to road is pretty obvious; cross to road is so small that I'm not sure if it's even real. Hence, wondering if there's something I can do to make these tests a little more accurate & objective.....