Which way would you go?

[Nvreloader]

Guys
I need a slower speed while in the 34t gear, it's to fast for rough riding, rock gardens, rock steps etc,
34t with max throttle power = 15.0-15.2 mph, flat road, (Eco 1 only)
34t with power on/pedaling speed= 7.1-7.5 mph, (Eco 1 only)
34t with NO power, just pedaling =6.4-7.0 mph.

I would like to get into the 2-4 mph range, with the use of the throttle, in (Eco 1 only) mode.

Thinking about changing the rear cassette to 9x15-46 to 15,19,24,28,34,38,42,44,46,
with either a 38T - 44T ring gear.

I have this now, 11,13,15,17,20,23,26,30,34/44T RG, I never use the 11/13T gears,
so I could lose them,
I like slow speeds and under control when on the trail.

Change out the cassette, ring gear or both, other options?

Your thoughts and suggestions...........
Tia,
Don

 

[Jeremy McCreary]

I also wanted a significantly lower gearing than stock. Took 3 tries and changing both chainring and cassette to get it dialed in, but a huge improvement in riding experience in the end. Thinking in gear-inches instead of ratios really helped.

Within rounding error, most off-the-shelf cassettes come with a fixed multiplier F from one cog tooth count to the next. This gives a perception of evenly spaced effort levels. With my current 11-42t 10-speed cassette, F = 1.16, meaning that each larger cog has approximately 16% more teeth than the last.

If you plan to build your own custom cassette with n cogs ranging from T1 teeth on the smallest cog to Tn on the largest, you can take the same approach with these spreadsheet formulas:

F = (Tn / T1) ^ (1 / (n - 1))
T2 = T1 * F
T3 = T2 * F
and so on. Round the results to the nearest whole numbers as desired.

Pleasantly surprised when my mechanic suggested going from the stock 9-speed cassette to a 10-speed after the first try. Had to change derailleur and chain to make it happen, but we were going to upgrade these components anyway. Whether this an option on your bike will depend on the final chainline and other details.

Enjoying the larger selection of lower gears now with no problems 600 mi later.

 

[PedalUma]

Go to Sheldon Brown's Gear Calculator. All you need to do is change the ring to lower the ratios.

Sheldon Brown's Bicycle Gear Calculator

A JavaScript calculator for analyzing bicycle gearing

www.sheldonbrown.com

 

[Jeremy McCreary]

Go to Sheldon Brown's Gear Calculator. All you need to do is change the ring to lower the ratios.

Sheldon Brown's Bicycle Gear Calculator

A JavaScript calculator for analyzing bicycle gearing

www.sheldonbrown.com

View attachment 160343

Tried that on mine. Big win in the lower gears, but realized after a few weeks that it lowered my top gear too much. That's when the cassette change entered the picture. Now the gearing's exactly to my liking.

 

[PCeBiker]

Tried that on mine. Big win in the lower gears, but realized after a few weeks that it lowered my top gear too much. That's when changing the cassette as well entered the picture.

@Nvreloader doesn't use his top two gears, so changing out just his chain ring may be enough, and bring his top gears into range.

So what's the math on "converting" an 11t to a 15t using a smaller chain ring?

 

[Jeremy McCreary]

@Nvreloader doesn't use his top two gears, so changing out just his chain ring may be enough, and bring his top gears into range.

So what's the math on "converting" an 11t to a 15t using a smaller chain ring?

NB: Edited to correct formula for advance A and add formula for ground speed S

Working all this out in advance could easily save time and money. The math's not hard. A spreadsheet makes the what-ifs a lot less tedious. Let

Tf = front (chainring) teeth
Tr = rear (cassette cog) teeth
R = Tf / Tr = gear ratio for that cog
Dw = nominal outer tire diameter in inches
G = R * Dw = gear-inches for that cog
A = G * pi = inches advanced in one crank revolution for that cog
C = cadence in RPM
S = C * A / 1056 = speed in MPH for that cog at cadence C

At a minimum, you'd want to figure the ratios R or gear-inches G for the gears you already have. Use that info and how those gears feel to pick the new top and bottom ratios or gear-inches to try next.

Assuming a single chainring, juggle chainring and smallest and largest cog teeth till you can hit both targets with one chainring. For a custom cassette, work out the cassette teeth in between from there.

 

[Nvreloader]

Guys
Let me ask another question,
What is the maximum number of tooth jumps, 4 teeth, 8 teeth etc per sprocket size,
to keep and even smooth shifting?

I have this shifter on my bike,

• Sram X-5 9 speeds
• DNP 11T-34T with KMC Chain

 

[PDoz]

Guys
I need a slower speed while in the 34t gear, i

34t with power on/pedaling speed= 7.1-7.5 mph, (Eco 1 only)
34t with NO power, just pedaling =6.4-7.0 mph.

I

I have this now, 11,13,15,17,20,23,26,30,34/44T RG, I never use the 11/13T gears,

Ah, got it - you have 44T chainring and want to reduce from 6 to 4 mph ( 30%) - so drop the chainring by 30% , ie try a 30 T if you are certain you never use the fastest 2 gears, or a 32 if you might be wrong.

 

[Jeremy McCreary]

Guys
Let me ask another question,
What is the maximum number of tooth jumps, 4 teeth, 8 teeth etc per sprocket size,
to keep and even smooth shifting?

I have this shifter on my bike,

• Sram X-5 9 speeds
• DNP 11T-34T with KMC Chain

See my post above. For a feeling of evenly spaced gears, you want the teeth on adjacent cassette cogs to differ by a fixed multiplier (1.16 in my case), not a fixed number of teeth.

 

[PCeBiker]

Ah, got it - you have 44T chainring and want to reduce from 6 to 4 mph ( 30%) - so drop the chainring by 30% , ie try a 30 T if you are certain you never use the fastest 2 gears, or a 32 if you might be wrong.

He's also got the fat tooth/skinny tooth chain and chain ring (whatever that's called?) so he has to keep that in mind,..

 

[PCeBiker]

See my post above. For a feeling of evenly spaced gears, you want the teeth on adjacent cassette cogs to differ by a fixed factor (1.16 in my case), not a fixed number of teeth.

If he only changes his chain ring, he will have the same spacing and feeling with his gearing, except it will all happen at slower speeds.

 

[PedalUma]

@Nvreloader doesn't use his top two gears, so changing out just his chain ring may be enough, and bring his top gears into range.

So what's the math on "converting" an 11t to a 15t using a smaller chain ring?

I did that calculation. It is about ten fewer teeth on the chainring to make an 11 act like a 15 cog. In this example a 31 tooth rig to an 11-t cog, goes 18 MPH at a cadence of 80. And in the lower right a 41 ring to a 15 cog, goes 17.6 at a cadence of 80 RPM. Basically, everything is shifted down by almost 1/3rd.
I use some cassettes with large jumps, but they require special shifters and derailleurs.

 

[PCeBiker]

I did that calculation.

Thanks,..
I haven't done that kind of math since 1984, and I haven't used a spreadsheet in almost 25 years.

 

[PedalUma]

He's also got the fat tooth/skinny tooth chain and chain ring (whatever that's called?) so he has to keep that in mind,..

That is a narrow/wide chainring. It holds the chain better and delivers better power. Other factors: BCD and number of ringbolts. He is one for about $10.

 

[PedalUma]

Thanks,..
I haven't done that kind of math since 1984, and I haven't used a spreadsheet in almost 25 years.

Sheldon Brown's Bike Gear Calculator did the math. It is so easy. I have a chainring on my wall that is 58-t. When I didn't know better, I wanted to go 50!

 

[Jeremy McCreary]

He's also got the fat tooth/skinny tooth chain and chain ring (whatever that's called?) so he has to keep that in mind,..

Typical narrow-wide chainrings take standard chains. You can only seat the chain one way, so if the chain links and chainring teeth are both even, the phasing takes care of itself.

Proprietary drivetrains like Specialized's Wave system might be a different story.

 

[PCeBiker]

Typical narrow-wide chainrings take standard chains.

I think that's the case for @Nvreloader ?

Something about needing to remove two full links to shorten the chain, but he has adjustable horizontal rear dropouts (whatever thats called. ) to help him make adjustments

 

[Nvreloader]

Thanks Guys
You are helping me out.

Also some other info that may be needed,
Tire circumference = 2474mm = 30-1/4" dia x 26 x 4.5" wide
BCD = 130 mm + Narrow/Wide chain/CR
5 bolt Chain Ring

I am also comparing the results with this calculator, that was shared with me.

Ritzelrechner - Graphical Gear Calculator for Bicycles

The bicycle gear calculator displays graphically the gearing of derailleur gears and gear hubs. It can be used to compare different setups to find the optimal gearing for all kinds of bicycles.

www.gear-calculator.com

There is a difference between them.

 

[PCeBiker]

Also some other info that may be needed,
Tire circumference = 2474mm = 30-1/4" dia x 26 x 4.5" wide

That shouldn't matter unless you intend on changing your tires, in which case, tires with a smaller diameter/circumference will help slow you down as well.

 

[PDoz]

He's also got the fat tooth/skinny tooth chain and chain ring (whatever that's called?) so he has to keep that in mind,..

That's why he needs either a 30 or 32 chainring - even number of teeth so the narrow / wide remains in sequence with his chain

When he drops from 44 to 30 , he needs to remove "7" links from his existing chain , which is actually going to need to be 6 links

If he then finds one end of his gear range doesn't quite match his needs , that's when he replaces the cassette ( or even just one cog on it)