alij2018

Hi, I have a hardtail with Deore setup. Cassette is 11-42T and chainring is 30T. I ride on tarmac more than offroad. I do climbing on tarmac as well as offroad too. I noticed on tarmac, it seems I lose cadence a bit with the 30T and even when I on the highest gear at the back.

I have a commute with 7 speed with a cassette of 14-28T and 34T chainring. I ride much better on it on tarmac when I am on my highest gear.

I did a gear ratio calculation for my hardtail. I calculated for my current setup then with chainring size 32T and 34T. I attached the results' screenshots.

My questions are:

1/ The more the ration is bigger in number, the better is? (Sorry, I don't understand gear ratio well).

2/ According to you, will a 32T or 34T better for me on tarmac and even on offroad? Bear in mind I do climbing on both as well.

Thank you

Retro Grouch 

So it sounds to me like you want to set up a single chainring rig.

If that's the case, a 34/11 will give you an 80 gear inche fastest flat road gear. If it was my bike, I definitely woulden't want to go any lower than that.
34/42 will give you a 21 gear inch easiest hill climb gear. That's pretty easy.

Iride01 

Are you saying that you are spinning out when in your highest gear ratio? Or put another way, you are pedaling crazy fast and not getting the speed you want?

If so then you have to do something to get a higher ratio front to back. Essentially the front gear has to get bigger with more teeth. Or you need a smaller rear gear with less teeth.

2¢ Might just need to get a road bike if you are going to be on pavement all the time.



as for these:
1) Ratio is the tooth count of the front divided by the tooth count of the rear. The higher the ratio, the faster you will be at any given cadence than a lower ratio at the same cadence. However, it takes more power to pedal that higher ratio. So you have to figure out what works for you.

2) My big gear on the front is a 52 tooth. It works fine for the small hills I have around me with a 11-30 eleven speed cassette on the rear for the 40 mile rides I do. If I get a little tired or ride where a hill is unusually steep or long, then I might have to shift the front to the 36 tooth ring.

So I don't know that a 32 or 34 tooth front is going to do much for you long term on pavement. You'll probably quickly find even they are to low a ratio for you.

cxwrench

For now I'll say 40.

Moisture

The number one problem is that it seems you are using a mountain bike for pavement.

Number two, there are many factors which change your gearing other than teeth count such as tire diameter and crank arm length.

Third, I dont fully understand how you have concluded that you need more teeth in the front chainring. It seems understandable considering what sort of bike you are riding.

70sSanO

You lost me.

You ride a 34/14 (2.42:1) 7 speed commuter and your hardtail has a 30/11 (2.72:1).

Are you saying the 34/14 is better on pavement?

John

cxwrench

Wait...what?

PeteHski

The bigger the ratio number, the harder it will feel to pedal and vice-versa. So if you find it too easy to pedal on tarmac in the highest gear (30-11) then a larger chainring will help. But your comment in bold above doesn't make much sense. If you are losing cadence in the highest gear, then you simply need to shift to a lower gear!
For tarmac a 34T chainring or larger should be fine, but it depends on how strong/fit you are. The bigger you go, the stronger you need to be.

wolfchild

You're inventing problems which don't even exist...There is nothing wrong with using a mountain bike for riding on pavement.

ofajen

This is probably referring to Sheldon Brown’s gain ratio, a way of calculating bike gears that factored in crank length. Gain ratio = distance traveled by bike divided by distance traveled (around BB) by the pedal axle. So longer cranks would reduce the gain ratio. Probably at least some merit to his thinking but not enough, IMO, to justify the complexity of the system. Also, I find the effect of a change in crank length to mean more to pedaling than just a change in gear ratio.

Otto

Moisture

What on earth?

How is the geometry, tires, suspension fork in particularly, or the gearing at all suitable for riding on pavement?

If you used slick tires in a similar diameter, changed to a rigid fork and made some changes to gearing it would work okay, but I'm having trouble seeing the comparison between trails and pavement being compatible.

Moisture

Each 2.5mm increase in crank arm length accounts to a roughly 3% increase in gear inches, however, provided that the crank arms are not too long, your ability to push that heavier gear will go up a certain percentage as well...

Even if the crank arms are somewhat too long, you should still be able to output a bit more power at the expense of overall cadence speed. But the overall smoothness of your cadence will suffer at specific areas of your pedal stroke especially as you begin to fatigue.

In my experience, how smooth the bottom bracket was alone made a bit more of a difference than the length of the crank arms.

Also, while longer crank arms may have you pushing a higher gear, it certainly didn't feel that way for me when outputting higher watts, especially going up a hill. Overly Small crank arms can affect power out and the quality of your cadence all the same, even though you are supposedly pushing "an easier gear."

Iride01 

No there isn't anything wrong with a mountain bike on pavement. However the OP has a mountain bike that is being used on pavement and they are having problems.

So I might be that the OP's mountain bike isn't giving the OP the riding desired on pavement and something has to change. However the OP seems to have a 1x front and anything done to significantly change the ability to ride pavement faster will work against that bike when the OP goes back to gravel or entirely off road.

wolfchild

He said his cadence was off, whatever that means I don't know. I suspect that he may be spinning out because his gearing is a little bit too low. Not really a big problem, all he needs to do is put a slightly larger chainring up front.

wolfchild

I realize that a mountain bike will never be as fast as a road bike on pavement, but I am willing to live with that because I don't ride for speed. I prefer utility and versatility over aero performance and speed. I've done 100 mile century rides on my singlespeed mountain bike set up with about 64 gear inches.

PeteHski

That doesn't make sense. A longer crank arm gives you more leverage on the crank (Torque = pedal force x crank arm length), which should make it easier to push down. But if the crank arms are too long then you would struggle with the range of motion, especially at high cadence. Remember that power = torque x cadence. So high torque + low cadence can give the same power as low torque + high cadence. So it's a balance between the two. This is why long cranks will feel easier when pedalling at very low cadence out of the saddle. You are able to apply more torque on each pedal stroke because of the extra leverage. But in practice we are talking about a couple of mm difference, which will have more affect on the smoothness of your pedal stroke than anything else. In the context of this thread it is totally irrelevant.

PeteHski

Lol!

Maelochs

Longer crank arms increases the force needed to move them exactly as much as it increases the force applied. It is not easier to pedal at a given cadence with longer cranks, it is harder .... but it is also an issue of leg length. Really short cranks spin quickly and easily but might not be involving all the leg muscles adequately.

As for all the rest .... the OP hasn't really made clear what his issues are, and as for the rest .... I have learned not to get into ideological battles with "true believers" on BF.

I'd be out riding right now if it wasn't three times as hot as hades .... or i'll fix the flat on the one that I found flatted as I went out to ride last night. or I will clean the kitchen floor with a toothbrush ... anything is better than trying to fight with BFers who "know" that they "know" the "right way to ride."

PeteHski

Since when did a longer lever require a larger force applied to move it?

I agree with the rest about cadence, which is why I mentioned power = torque x cadence. There's no point in increasing torque if cadence drops in the process. I'm quite a fan of shorter cranks simply because I think they tend to reduce fatigue and injury (less leg/knee/hip angulation). But they don't have much effect on power output, at least not within the standard 170-175 mm range.

wolfchild

I know it doesn't make sense to most people, but that's how I've been rolling along for many years.

Iride01 

Yeah, I think we all got that. We are waiting to hear back from the OP to clarify exactly in what way.

However like I said, if the OP's bike is 1x and the OP wishes to ride off the pavement some, then getting a more appropriate gear ratio for pavement might cause the OP to loose lower ratios that they might wish to keep for gravel or real off road cycling.

Don't be so worried that the OP will give up their mountain bike for a road bike. They probably are mature enough to make that decision on their own and if it's not desired, they can tell us that getting another bike is not desired.

Letting the OP speak for themselves will save a lot of bickering.

PeteHski

This is the part that doesn't make much sense and needs clarifying by the OP. Losing cadence implies that he simply needs to shift into a lower/easier gear. But I'm now wondering if he's getting confused between the "highest" gear and "largest" gear on the cassette.

wolfchild

Personally I wouldn't even worry about keeping track of cadence. When it comes to cadence there is no right or wrong number...Just pedal and enjoy the ride.

Maelochs

Yup ... even I can't figure out that one. Whoever posted it needs to back to school ......

PeteHski

But you don't worry about anything bike related from what you post. A bit like my dog