Hung up on wrong thing...gear ratios

[helston90]

Gonna start one of those- "sorry if this is silly" questions.

Will I notice that much difference from different top gear ratios based on cog teeth?

Looking at the Giant Rapid range which has
Rapid 4- 52:11
Rapid 3- 52:12
Rapid 2- 50:11
Rapid 1- too expensive :P

This would make the 4 faster than the 1 right based on Sheldon's Calculator? or is there more to it than that?
It's tending to be one of the first things I look at when comparing bikes/ models and not sure if I should or not.

 

[Cyclist33]

My guess is that the combo in the 4 just happens to be because the components pick for that budget have those numbers of teeth.

I'd be quite surprised if a rapid 4 rider wanted to sustain 52-11 over any serious distance.

 

[busdennis]

the rapid 4 will be quicker than the 3 or 2 if you are capable at spinning the wheels at the same cadence
the rapid 2 will be quicker than the 4 if you can spin it at an higher cadence

lance armstrong used cadence
jan ullrich turned big gears

 

[MrJamie]

They do a similar thing with the TCX, with the better carbon fork models having a 34/46 front or something while the cheaper one has a 34/50.

IMHO thats a seriously fast gear for a flat bar bike, i find my 48-11 more than adequate for me

 

[helston90]

The 48- 11 is what the Sirrus bikes I'm looking at have but was suprised to see Giant vary that much in their range.

I'm going from a 48:14 on my very old hybrid so not sure what to expect or whether I'll really notice the difference.

A couple of down hill straights on my commute my speed is limited by my gears and wanted to avoid that happening on the new bike.

 

[black'n'yellow]

Unless you will be spending all your time in those gears (which you won't be) then the issue is quite simply irrelevant. All of those bikes will offer usable gear combinations for everyday riding and the only way you will achieve 'max speed' on any of those bikes is on a long downhill. Ultimately, your aerobic fitness will decide which gear you want to be in and how fast you want to go..

 

[Jdratcliffe]

depending on who your buying from i find most LBS' happy to swap out cassette of equal value i got my 105 12 27 swapped for a 10 25 due to my cycle style preference of torque rather than super fast spinning.

whoare you looking at buying from have you asked if you can swap out a few bits?

 

[Sittingduck]

I wouldn't worry about the top end ratio too much. You won't spin out on 50-12 often. On a sustained steepish downhill you can achieve around 45mph without spinning out. I would be more concerned with figuring out which combinations you are likely to use regularly and can be hit with minimal switching between front chainrings.

 

[Rob3rt]

None of the bikes are faster than the other! They will only go as fast as you can ride them.

Forget the gear ratio's right now, it is pretty much irrelevant, they will all offer plenty of usable ratio's and you can swap out the cassette in the future if you find it limiting (which I doubt you will).

 

[GrasB]

Once you've got your big ring in the >50t range most of what makes a bike faster on the flat (-1.5~1.5% gradients) is what the middle of the cassette is doing. A 12-23 cassette will tend to be faster than an 11-32 because the gear steps are smaller so you can balance your CV & muscular loads better. If you're going down hill to really make a bike faster you quickly find that you need a >60t chainring is needed to make a gearing difference in top speed.

 

[helston90]

None of the bikes are faster than the other! They will only go as fast as you can ride them.

Surely though if I (figuritively speaking) put 100 rpm through each then there would be a difference in speed?

But the overall consensus is right I'll rarely get to use them and won't out do them- I was just concerned I would spin out and wish I'd bought differently (having been riding a bike that did a lot of the time)

 

[boydj]

Unless you will be spending all your time in those gears (which you won't be) then the issue is quite simply irrelevant. All of those bikes will offer usable gear combinations for everyday riding and the only way you will achieve 'max speed' on any of those bikes is on a long downhill. Ultimately, your aerobic fitness will decide which gear you want to be in and how fast you want to go..

+1
Unless you have legs like Chris Hoy (or the new king - Jason Kenny), then top gear is something you will very rarely use. More important is that you have a bottom gear that lets you get up all the hills in your area. Getting down the other side takes care of itself.

 

[Rob3rt]

Surely though if I (figuritively speaking) put 100 rpm through each then there would be a difference in speed?

But the overall consensus is right I'll rarely get to use them and won't out do them- I was just concerned I would spin out and wish I'd bought differently (having been riding a bike that did a lot of the time)

Ofc for a given cadence, a large gear ratio would result in a higher speed, BUT the point is, if you cant turn the higher ratio over at that cadence for any meaningful amount of time, it's of no consequence what the theory says.

Eg. 85 gear inches at 90 rpm would result in a higher speed than 72 gear inches at a cadence of 90 rpm, however if you don't have the sustained power output to turn over 85 gear inches at 90 rpm for any length of time then you will either never use it, or your shift into that ratio and then after a short period of time you will slow down as your cadence naturally drops with fatigue. Chances are you will struggle along blowing your arse out for a short while, then shift back to an easier gear but being absolutely spent you will then be unable to even turn that over at 90 rpm for some time while you recover. The net effect is you will probably end up going slower than if you stuck to the easier gear ratio and spin that at 90 rpm. A wide ratio cassette will make such phenomena quite obvious as there is a larger step between adjacent ratio's and you will find the jump can be very noticeable, where a more compact cassette will allow more fine control of your load, as explained by GrasB, but on a hilly course you may find that you need a wider spread. Gear ratio's are something that you can (and should where appropriate) change depending on the terrain you are going to ride? It is not something you are stuck with once you have bought the bike.

So back to my point, neither bike is faster, they will only go as fast as YOU can ride them.

 

[helston90]

All very true and makes sense- thank you for taking the time to explain it!

As has been mentioned 11:48 seems more than adequate so I'll get over it and turn my time to other issues such as convincing my work to do the C2W scheme so that this mystical bike can come into fruition.