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Help, why is my second bike so much slower??(9 posts)

Help, why is my second bike so much slower??glia
Dec 21, 2003 8:49 AM
My main ride is a 15lbs, nicely equipped 2003 Specialized E5 S-works bike with all Dura-Ace, FSA compact carbon cranks, USE aero seatpost, Speedplay pedals, Deda Mag stem, 3T carbon bars, USA Ti brakes, titanium cassette.. For fun and to use during the off season I just build a second bike mainly from EBAY components. I was able to maintain essentially the same geometry by using a frame with similar geometry, namely a E5 frame that came from a Specialized Allez SLX. I maintained all critical measurements from seat to handlbar and crank arms so that the bike fit is essentially the same. However, I have been using mostly cheaper components. I like to blast out on my daily 30 mile training ride through hilly country and average between 20.3-21 mph on my main bike, never dropping lower than a 3mph average. The new one, I am at least 1 or even 1.5mph slower on average no matter how hard I try. I come in as much as 7 minutes slower on a 30 mile ride! I have a hard time figuring out just what it is. I went back and forth between the bikes and it is not just in my head. The slower bike weighs 17.25lbs, has Ultegra cranks on an Ultegra BB, but also uses Dura-Ace derailures. The faster bike weighs 15.0lbs, uses the FSA carbon with a Dura-Ace-BB. Could that be it? I did switch wheels and that makes no difference. I am riding Topolinos on the fast bike and Ksyrium SSCs on the other. All the other components like shifters brakes seatpost are not in the power train and I think shouldn't matter. Somehow it seems as if the power doen't get on the road. Any thoughts...
Too many factors, too little informationContinental
Dec 21, 2003 9:25 AM
The reason for the slower speed could be measurement errors, or it could be environmental, physiological, psychological, or mechanical factors. The first thing you need to do is to check the calibration on the speedometers. Then, if you really want to do this right, you'll need to have a rigorous design of experiments with several different riders repeatedly riding each bike over the same course in very well controlled experiments before you can conclude that the problem is mechanical differences between the bikes. Otherwise, you'll just be speculating.
re: Help, why is my second bike so much slower??seyboro
Dec 21, 2003 9:28 AM
Same computer? Same wheel setting? Same size tires?
I also agree. nmDave Hickey
Dec 21, 2003 10:28 AM
some thoughts..C-40
Dec 21, 2003 10:17 AM
If you ride the exact same route and your computer registers the exact same mileage, you can rule out computer error.

Be sure you're not ignoring wind conditions. I can ride the same route many times and my average speed may vary from 18 to 20.5 mph depending on the wind and how much effort I felt like exerting on a given day.

The weight difference is not the culprit. On moderately rolling terrain, the weight difference would not reduce your speed by more than a few seconds.

I would carefully check your knee over pedal (KOP) position to see if you are sitting in the same position relative to the bottom bracket on both bikes. KOP is not easy to measure accurately. You should place each bike on an indoor trainer in a level position and ride for at least 10 minutes to be sure that you're fully back in the saddle before having a helper drop a plumb bob from the knee. Trying to do this without a helper is difficult. It's easy to shift position and get a false reading by yourself.

Saddle height is also tough to get perfect on two bikes, unless the same saddle is used on both. If the same saddle is used on both bikes, then a plumb bob dropped from the nose of the saddle would provide a valid comparison of your position relative to the bottom bracket and you can skip the KOP comparison.
Thanks for all the inputglia
Dec 21, 2003 12:49 PM
Thanks for all the input. I am using the same speedometer, same wheels and tires, I actually swop the whole thing. I do use the same seat and have carfully measured the seatposition with regards to center of crank. I was not suspecting the weight to be an issue. I am wondering if you can get a gain of 2-3% in power output to the wheel from using a different crank-BB combination. I am using the same chain and rear cassette. Nevertheless, there are some very valuable suggestions presented. If anyone has additional ones, I will be checking back.
cold air is denserContinental
Dec 21, 2003 3:09 PM
If you ride your "slow" bike in weather that is 25 to 30 degrees F cooler, the wind resistance is about 5% higher. This could easily account for a large part of the difference in speed. There are many plausible causes and no way to know which ones are significant. If you have more details about conditions, and actual times and speeds for many rides on each bike, it might be possible to eliminate some factors. If you've only ridden each bike a few times on the same course, you're probably jumping to conclusions. Generally, it takes about 12 data points for each bike to make an analysis to identify a difference that stands up to statistical scrutiny. If your times for the same bike are like clockwork, it would take fewer data points. If your times vary widely for the same bike, ti would take more data points. In any case, 2 or 3 rides won't show anything,
It’s mental – you like it more...TFerguson
Dec 21, 2003 2:28 PM
That's why none of the weight and aero discussions really mean anything. If you think it will be faster and have the means to make it so, it will be faster.

There's a story in one of the cycling books (Serious Cyclist?) where the author discovered the secret of cycling. He found that the caffeine in coffee flavored yogurt decreased both his training and his competitive TT times. He had the numbers to prove it. Much later, he found out that there never was any caffeine in the yogurt, just the coffee flavor.

I'm only a newcomer to this sport, but the mental portion seems to be way under rated, at least on this board.

TF
It’s mental – you like it more...Barton
Dec 22, 2003 7:32 AM
Have to agree. The "better" bike has to be faster.