Take the 2-minute tour ×
Bicycles Stack Exchange is a question and answer site for people who build and repair bicycles, people who train cycling, or commute on bicycles. It's 100% free, no registration required.

I have access to two mountain bikes, a lighter one (lapierre) and a Giant. The maintenance I do to both is really similar, just tires and oiling the chain every few weeks. I always though that the lapierre was harder to ride but the other day I did an actual test. Before I set off I checked the tires and oiled the chain and did the same distance, at the same time and similar weather and the lapierre was much more work and did a slower top speed and average speed, can anyone suggest any reasons for this and how can I fix it?

I took a bunch of pictures of both bikes first the slower Lapierre then the two bikes and then the giant here http://imgur.com/a/G1MST#7

Tyre pressure is for both bikes on the 30s

I think tyre size is 26" (not sure) tho, as you can probably see from the pictures, they are the same size

Edit: very similar tires (if anything the giant has more grip), suspension exists and set to as stiff as possible on both (the test was performed on road), As for different gearing I have no idea how to check rider position feels very similar Will take pics today and these tests are done on roads (ie while commuting)

My measurement was done using strava but also I felt it was harder to ride and thought I might have been slower

Cheers

share|improve this question
6  
Any other differences in the bikes, like style of tire, suspension (exists and also how stiff it is), different gearing, rider position, etc. All these things can make a difference in bike performance. Also, have you checked that the brakes aren't dragging on the slower one? –  Kibbee Jan 2 at 13:28
1  
For gearing, count the number of teeth on the each of the front chainrings, and the number of teeth on the smallest cog in the back, as well as the number of teeth on the largest cog in the back. This will give us an idea of the range of gears available. The largest front with the smallest back gives the hardest/fastest gear, and the smallest front and largest in back gives the easiest/slowest gear. –  Kibbee Jan 2 at 13:58
1  
Or alternatively, just look at the part numbers or the cogs themselves (Shimano stamps them on there somewhere on a lot of them). As for how you tested them, if you rode them back to back and rode the lapierre second, it would seem harder to ride, so you may want to test this to see if there are any confounding variables. –  Batman Jan 2 at 14:07
1  
Also, how are you measuring top speed and average speed. If using a speedometer, is it set up accurately (did both read the same distance at the end of the ride). Do a test with a stop-watch over a fixed course to eliminate errors in the speedometer from the equation. You can even record times at certain points in the ride (stopwatches often have a lap feature) to see which parts are slower than others. –  Kibbee Jan 2 at 14:39
3  
The only possible factors that could cause the difference would be tires, suspension, gearing, and riding posture. The easiest way to check gearing is to ride the bike for, say, ten turns of the crank and see how far it goes. –  Daniel R Hicks Jan 2 at 16:16
show 7 more comments

3 Answers

If you're measuring via Strava, keep in mind there are a lot of factors that can play into your time. Unless you're averaging many rides over time on each of those bikes, thing like wind, clothing, what you ate, etc, can all play in to the time you post to Strava.

share|improve this answer
add comment

it might be the tire tread, the lapierre tire seems to be knobbier in the section which contacts the road, while the giant has a fairly constant height section which is used when going straight.

:)

share|improve this answer
add comment

There's a lot of possible explanations for why one might be quicker than the other.

One factor is: you, for a whole range of potential reasons,

  • Maybe you pedalled harder (e.g because of fatigue)? A power meter on each bike would help isolate this, but.. a bit expensive (unless you could, say, borrow a Stages or Polar power-meter from a friend for the day?)
  • Maybe you could are comfortable one one bike (e.g better fit, or just more familiar with the handling of one bike)
  • If you believe one bike is faster than the other, you may subconsciously ride it faster - these sort of issues come up in scientific studies all the time (e.g observer bias, the placebo effect)

Another factor is how you compared the bikes:

  • A single run over the same course is unlikely to give meaningful results. It would be useful to ride the course several times on each bike - the more times the better. The variation of a single bike is an important factor - e.g if bikeB was slower, but
  • GPS isn't perfect. If you are calculating speed from GPS, any positional error will skew the average speed.

In addition to the wheel related differences (rolling resistance via tread, pressure etc), there's countless other mechanical reasons one bike might just be faster.. I guess the main thing is to consider all the places where friction could occur. E.g unlikely but maybe the brakes are rubbing a bit on one bike? Or maybe the wheel-hubs or bottom-bracket are a bit gummed up? Maybe one chain is more worn and in need of lubrication? etc etc

share|improve this answer
add comment

Your Answer

 
discard

By posting your answer, you agree to the privacy policy and terms of service.

Not the answer you're looking for? Browse other questions tagged or ask your own question.