Surprised and now Really Confused!

[getfit]

Hi All,

I was reading through a few threads and came across the Gear Ratio thread and went onto the http://www.sheldonbrown.com/gears/ page.

I put in the gears of the road bike I am interested in 39/50 chainring and 12/25 10 speed cassette and also my current Hybrid set up, 28/36/48 chainring and 11/32 cassette.

The confusion comes when I compared the results and was surprised at the close results.

The highest gear with the Hybrid comes in at 8.5 while on the road bike it's 8.4. I have to admit to expecting to see a higher figure on the road bike. I currently only use the top chainring on the Hybrid but live in a hilly area so do find myself using the 48/32 combination and this comes in with a figure of 2.9 while the lowest setting on the road bike is 39/25 with a figure of 3.1.

Now I'm happy that the lowest setting on the road bike will be low enough for me, my concern is that the highest gear is less than the Hybrid.....Will I see a noticeable improvement in my average speed?
Thanks for taking the time to read through and looking forward to your thoughts.


GF

 

[Big T]

That's because the Hybrid has an 11 sprocket and the road bike only has a 12. Even though the road bike has a larger chainring, the smaller sprocket makes more difference.

You'll actually find that you hardly use your top gear, as you've got to be really motoring to be able to push that around on the flat. It's a gear for fast descending.

In old terminology, 50x12 = 112.5 inches, 48x11 = 117.8 inches.

If you're that bothered by it, you can always put an 11 up cassette on the road bike.

 

[jack the lad]

You'll probably find yourself going faster more of the time, even if the absolute top speed isn't much greater. Also bear in mind that the top speed isn't necessarily achieved in top gear. In some conditions, like a headwind, you might achieve a much higher leg speed & bike speed if you drop a gear or two.

Also a word of advice - try to avoid using gears like 50/25 and 39/12 if you can. The chain is working at quite an acute angle which is less effieicent and will wear out the gears quicker. If you look at the full range of gear options on sheldon brown you should find other gears that use the big ring at the front with the smaller ones at the back and vice versa with reasonably even steps between them. So assuming it is 2 at the front and 9 at the back you would go up through the gears from 1/1-2-3-4-5 then 2/5-6-7-8-9. If 1/5 to 2/5 is too big a step, try 1/6 or 2/4 for an in between gear, but no more than that.

On your hybrid, for example, 36/24 is the same gear as 48/32 or even (near enough) 28/17, but would have the straightest chain line and be better than the other two options.

 

[getfit]

Cheers Guys,

I can see where I was becoming transfixed on the highest gear and agree that with proper gear selection as well as a more road focused bike I should see my average speed increase.

Regards

GF