What is Cadence and what role does it play with my E- bike?
It’s how fast you spin your legs & it effects comfort, range, speed, fun, exercise & endurance. It also keeps those in uniform from thinking too hard about how you manage to go 25 mph without moving your legs.
With all of the information available on E bikes and e- bike conversions I find it puzzling that the topic of selecting gear ratios for our e-bikes is so seldom discussed. Part of this, I’m sure stems from the fact that the majority of today’s E bike conversions are front or rear wheel hub motors and run completely independent of the bikes original drive-train. In addition to a lack of a physical attachment, the subject of cadence, gear ratios, crank sets, freewheels and the 100 year history of everything just mentioned would be large enough to dictate a forum dedicated to that alone. However, whether it’s independent or just to complicated, people, pedals & gears must remain an integrate part of the bicycle’s drive-train. Check out any road bike or mountain bike forum or website and pedal RPM, (cadence) gearing and shifting will be discussed in great detail, yet most electric bike forums rarely discuss the subjects at all. This is, in my opinion an oversight that needs addressed. Regardless of which E-Bike Kit you choose for your conversion project, in order to get the best range and most performance from your newly converted bike, your legs must remain a part of the equation. Since every rider has a certain speed at which they like to spin their legs and we don’t ride in a vacuum we need gears in order to maintain that speed. At this point you might be tempted to say that the hub motor is now doing what the legs and gears were doing before and you would be right. Except that this is not a motorcycle. It’s an electrically assisted bicycle.
That said, I did not pay too much attention to the gearing on my 1st e-bike conversion either. It was on an 1990 Mongoose with a 500 watt Crystalyte hub motor on the front. My gears actually quit working properly after about 6 months from lack of use. I mean aside from needing a place to rest my feet, I’m only going to peddle when I’m climbing a grade or my battery dies. I was far more focused on things like the battery voltage, amps, motor controllers, etc. Perhaps it was the “motor head” in me but It was only after the novelty of the electric motor had worn off and I got into the routine of using my bike for practical transportation that I began to pay attention to practical items like range, cargo capacity, comfort, etc. Let’s face it, in retrospect, the primary reason for electrifying my bike was to increase it’s practicality. NOT taking pedal power into consideration was ,…….. well, very unpractical.
As I said before, when we convert our bike into an electrically assisted bicycle we are not building an electric motorcycle. (Read the 50 mph electric bike e-book for that) We are simply making our bicycles easier to ride. We are augmenting our human leg power with some electric wheel power. Whether it’s a little power or a lot of power, gear ratio’s comes in when trying to match your leg speed (cadence or pedal RPM) to the bikes electrically assisted wheel speed (travel speed) while maintaining the optimal motor speed (RPM) on any given stretch of road. Keeping everything pulling together is critical for maximizing your battery range as well as the life of your hub motor & motor controller. The average 500 watt Direct Drive e-bike kit on the average stock MTB has a gear ratio that will work fine up-to about 15 MPH.. The problem is that this bike will now go about 20 MPH. Regardless of how strong your legs are, the speed at which you can comfortably spin them is not going to increase substantially even with help from the e-bike kit. This means that in order for your legs to keep pace with this higher travel speed you will have to have to either pedal like a maniac or change your gearing so your legs can keep up You can also just quit pedaling at these higher speeds or slow down. Stock gearing for the average mountain bike is along the lines of 42, 24, 34T on the front and 14T to 28T in the back. Using any one of the following gear or cadance calculators below, count the teeth on your front & rear sprockets and plug those numbers along with the other required information into the calculator form and see what you get. Having a speedometer on your bicycle will be a big help in verifying the figures that you will get. Calculator #’s 2 & 3 below are almost spot on with my Bell 100. #1 has me going about 2 mph. to fast.
If you are an average rider in average condition you will probably learn that you can peddle a bicycle with stock MTB or Hybrid gearing to a speed of about 18 mph and you can probably maintain a consistent top speed of around 13 mph. For those of us with distances to cover & places to go speeds closer to 20 mph would be much more viable. In addition, you’ll probably be carrying additional weight and possibly towing a trailer. If we expect to get a reasonable range from our batteries our legs must be part of the total drive train. Man, bike and motor must all work as one. Changing your bicycles gear train to remain in sync with your new electrically powered hub motor is not the only solution for increasing your speed. It is however the most economical and practical. The bicycle is already the most practical and cheapest form of transportation that there is. If we simply add an electric motor to the bicycles power train we have made it easier to peddle at slow speeds and we have increased it’s top speeds. However, if we can no longer help to propel it at higher speeds then we’ve actually decreased it’s efficiency. For about a $100 more and a few hours of work we could double our battery range per charge, get most of efficiency back, increase it’s practicality and do our part in significantly reducing traffic congestion & pollution.
The good news is that since E bike kits using hub motors are completely independent of your bicycles original drive-train, whether you make this change right away, down the road or not at all is completely up to you & should not in any significant way affect your purchasing decisions or the outcome of your project. Assuming you have already done your home work on the best type of bike to use for an e-bike conversion the following information should help you to maximize the overall efficiency of your e-bike conversion & save you money in the long run.
TIME & MONEY. Use them wisely but don’t skimp on quality. If you can’t afford to build it right the 1st time around how will you ever be able to afford to build it better the 2nd time?
As important as having the correct gear ratio is to the overall efficiency of your bike when it comes to choosing a bicycle or new gears for your existing bike you don’t need to spend extra money on high-end race-bread drive-train components. Much of the drive-train stress & abuse that expensive drive-line parts are built to handle will be eliminated with the installation of a hub motor. Concentrate on your bicycles frame & brakes instead. Providing the derailleurs are in good working order & properly adjusted & you have crisp clean shifts you should be golden. Since all e-bike kits using hub motors come already laced to a front or rear wheel you might even save money by finding a bike with a bad rim. Almost any “decent” multi-speed mountain or hybrid bike built since 1990 with external gears will have more than enough gears of sufficient quality to handle whatever conditions your likely to encounter. If you decide on using a front wheel drive e-bike kit you can also check out bikes with internal gears. Sturmey-Archer makes 7- and 8-speed hubs & SRAM makes a 9-speed model. These offer all the gears you’re likely to need with the convenience of having just one shift lever. The gear range is usually a little higher than mountain bikes with an external gears and if you do want to raise the overall gear ratio you just have to put a larger sprocket on the front. Since this is a fairly new system the options available may be somewhat limited. That said, I recently converted a Schwinn Sierra DSX using the Sturmey-Archer 8 spd.rear hub & a 36 volt front mounted gear driven hub from E-BikeKit.com & it was almost a perfect match right out of the box. The bike, rider & hub motor all topped out at about 18 MPH & although I would have preferred a more leisurely cadence at speed it’s still pretty darn good.
One contradiction to the above is the subject of gear shifters. It may be more of a personal choice than anything but I prefer a motorcycle style throttle on my e-bike. Just about all E bike kits today will come with both a thumb throttle and a twist grip throttle. A lot of today’s bicycles however, especially the cheaper ones, will come with twist grip shifters. A twist grip shifter negates the use of a twist grip throttle. Shimano makes a very nice trigger shifter that is found on many mid-range mountain and hybrid bikes. This set-up integrates well with most twist throttles & makes shifting very smooth. I find myself wanting to shift gears just for the fun of it. Although changing throttles after-the-fact is very easy to do, switching from a twist shifter to a trigger shifter is a bit more of an ordeal. Just some food for thought.
My current ride is a 22″ 2012 Marin Pioneer on 26″ rims & 26×2.0 Kenda Kwick Roller Sport tires with a 21 Spd. Shimano equipped drive-train & Shimano trigger shifters. ( Read “Night Rider” ) It came with fairly typical MTB gearing. 42,34,24T front chainrings & 14, 28T rear gear cluster. I had also installed a basic Bell 100 Cyclometer & a “Watts-Up-Meter” for monitoring the battery & motor. This was going to be a rear drive set-up which meant the rear hub already had a gear cluster attached & in this case the gear clusters where identical. When you order a rear drive e-bike kit you will usually have the option of choosing your wheel size, a 6, 7 or 8 spd gear cluster & sometimes a single speed. What you usually can’t specify is the type or the size of the gears. With my stock MTB gearing all of my riding for the first few weeks was done in high range & most of that was in 7th gear. Around town & in trafic I would sometime downshift into 5th or 6th. I’m pretty sure I never needed to downshift for a hill. I was running a 48V 10amp LiFeP04 battery pack & had a top speed of 26 MPH on a leval road with my 200 LB ass on the seat. However, I had usually quit pedaling somewhere back around 15 MPH. At 20 MPH I could no longer keep my feet planted on the pedals. Guess that’s why those professional types use toe clips.
After a week or so of riding with fairly dismal battery range (about 20 miles ) I decided some taller gearing was in order. It’s at this point that I should have referenced one of the handy online gear or cadence calculators that are posted above. Sadly I discovered them after the fact. Ultimately I ended up changing both the front crankset and the rear gear cluster in order to keep my legs in their “zone”. When I first considered this job I had thought I was just going to replace either my smallest 14 tooth gear in the back or my largest 42 tooth chain ring in the front. Fortunately I had a good friend, customer and former bicycle mechanic in State College PA that convinced me otherwise. His suggestion for replacing my gears as complete sets turned out to be spot-on. So after figuring out what I had and then sourcing the parts required, it did indeed turn out not only to be easier, but the results were great and any additional costs (if any) was offset by the time and work that had been saved.
The specific parts, tools, time & speed increase for this job are as as follows:
Click the headings to find those products at Amazon.com
- Replaced my 14,15,17,19,21,24,28T Shimano Freewheel gear cluster with A DNP Epoch Freewheel 7spd 11,13,15,18,21,24,28T at $26.98 from Amazon
- Special Tools required where a Park Tool FR-1 Freewheel Remover at $6.24 from Amazon
- Total time was 1.5 hour.
- Speed increase in High range high gear was approximately 3 mph.
- Replaced my 42 x 34 x 24 Shimano with A SRAM 48 x 38 x 38 S650 SQ TAPER at $44.29 from Amazon
- Special Tools required where a Park Tool CCP-22 SQ Taper Crank Remover at $12.23 from Amazon
- Total time was 1 hour.
- Speed increase in High range high gear was approximately 3.5 mph & at least 2 mph in all gears.
- TOTAL TOP SPEED INCREASE WAS APPROXIMATELY 6 MPH. WHICH IS VERY CLOSE TO THE TOP SPEED OF THE KIT.
That said, changing your gears as complete sets will, to some extent, limit your otherwise almost unlimited gearing choices. On the other hand it will also eliminate the need for changing your derailleurs your shifters and possibly your cables plus all the additional work & expense that goes along with it. AND, when you are done you will still have a significantly higher gear ratio and your gears will shift in the same way that they had shifted before. It’s truly the best of both worlds . For the three bikes, I have done so far, these jobs were straight forward, easy and inexpensive. The larger chain rings in the front will require you to raise the front cable mount. The back gear cluster required only a minor cable adjustment. From a technical stand point, determining just what type of gears I had, learning the proper terminology and then matching the original parts to the aftermarket parts was the hardest part of the job. When all was said and done however I was very pleased with the results. The shifting is now spot-on and I now shift for the fun of it. Most of my riding is still done in high range although I will sometimes use my middle range in town.
Most importantly I have just about doubled my battery range. Prior to the gear change my legs where contributing very little to the total power output. After the gear change that went up considerably & my hub motor is now spinning almost 100% of the time with help from my legs and or gravity. This makes for both maximum battery range & maximum component life.
Using the charts posted above my average cadence while cruising is somewhere around 60 RPM. I’ll often crank it up to 80 or faster to keep things interesting but I can’t go for long at that speed. This translates to between 21 MPH to 26 MPH as per my $20 Bell 100 Cyclometer. Leisurely riding is done at speeds up to 15 MPH & and I can stay with it all the way to 30 MPH. As you know or will soon find out there are many variables that go into determining what your actual travel speed is or will be. Your personal goal however should remain constant. For me it’s very simple. My bike & I work should work as one while maintaining a reasonable level of performance, comfort & safety that fit my needs. You’re needs will be different than mine and will almost certainly change over time. So keep it simple and keep it loose. Anything too complicated will usually lead to frustration. Remember, if it ain’t fun we won’t do it.
WHAT YOU NEED TO KNOW
As I had mentioned earlier, the hardest part of swapping gears on my bike was learning the the terminology used in describing the various components and the different configurations those components can comment come in. Replacing the front crank set and rear gear cluster took less than two hours for both jobs. Parts may be parts but if you don’t know how to describe those parts you’ll never get what you need. Since the Internet already contains a wealth of information on this I won’t duplicate it here. Instead, I’ll identify the basic definitions for the drive-train components you’ll be working with and provide you with the links for locating the parts, the tools and the instructions.
WHICH GEARS TO REPLACE & OTHER DETAILS
Determining which gears to change and what to change them too if at all, is completely up to you. For the average person that simply wants to build the most efficient e-bike he or she can with out re-engineering the entire driveline you’ll probable go as high as you can go by changing both the front crankset & the rear gearset. That said, the variety of bicycles, e- bike conversion kits and riding styles makes for an enormous combination of possibilities. Consequently if this is your first E bike conversion your best bet is to do nothing until you have the kit installed and you’ve had enough time to ride it and become acquainted with the electric motor set up and get a good feeling for what it will and will not do. If you find that you are now consistently riding your bicycle at speeds faster than your legs can go you know that there is room for improvement. However, if the distances that you ride never come close to depleting your battery and getting exercise is not one of your goals then perhaps you don’t need to make any changes at all. it’s all up to you.
Assuming that you do want to make a change to your bikes gears let’s look at the steps. Although both front and rear hub motors are completely independent from your bicycles drivetrain with the exception of the drive wheel itself, changes to the bicycles gearing will not directly affect the performance of your E bike kit. However because the hub motor for rear drive E bike kits comes pre-laced to a rear wheel it will arrive complete with the rear gear cluster that you had specified when you ordered it. This may or may not be identical to the original gears but it will be close.
In order to raise the overall gear ratio you will need to increase the size and tooth count of your front sprocket (s) and decrease the size and tooth count of your rear sprocket (s). Both jobs require some inexpensive specialty tools and with those tools both jobs are relatively easy. Replacing the front crank set is marginally more expensive than changing the rear gear cluster but has the advantage of raising the gear ratio through the entire range of gears as opposed to changing the rear gear cluster which will usually have just to or three higher gears and the entire set.
What you can or cannot do will be completely dependent upon what is available for your particular bike. So, be for going any further you need to determine exactly what type of gears you have on your bike.
Starting with the front crankset count the teeth on each individual chain ring (sprocket). Assuming you have three sprockets in the front and you are working on a mountain bike you should and up with something like 42 on the outside sprocket, 34 on the middle sprocket & 24 on the smallest inside sprocket. Now do the same for the rear. The tooth count for the rear gear cluster will be something like 14, 15, 17, 19, 21, 24, 28T.
These are the type of gears usually found on mountain bikes or hybrids. In the unlikely event that you would be working on a road bike the gearing will be much higher and quite possibly need no changes at all. The largest sprocket I have been able to find for this type of bike has been a 48 tooth. A 48 tooth will give you about a 3 mph increase over a 42 tooth Next try to determine the manufacturer of your sprocket. This is usually written on the crank and also on the chain rings themselves the manufacturer is not critical but it can make your job easier. Your crank set will at the very least consist of the chain rings and both cranks. In order to get the correct ones, measure the length of the crank from the center of the attachment holes at either end of the crank. This can be anywhere between 165mm & 180mm with 170mm &175mm being the more common sizes. You can also replace your crank with one that is a different length from the original. ( Read “Does Crank Length Matter?” )
Next, determine the type of end found on your bottom bracket axle. There are three styles of bottom bracket axles and a couple of variations for each one of those styles. The two oldest styles usually found on bikes prior to 1980 use pins to hold the crank on to the bottom bracket axle. Occasionally you will also run into a one piece crank where the crank and the bottom bracket axle are all cast as one piece and the chain rings will be bolted to a flange that is cast into the one piece axle and crank assembly. Given the age of this type of set up you will want to carefully check the condition of both the axel & the bearings to in sure that everything is still in good working order. Many older cranksets that are fastened with roll pins or cotter pins can usually be removed with basic hand tools found in most toolboxes. In order to remove this type of bottom bracket axle assembly you will probably need a spanner wrench of some type. Most newer bike are cotterless and the crank & chainrings are pressed fit and held in place with a bolt. The most common type of bottom bracket axle in this category is the square tapered shaft. Less common is the splined shaft. This comes on and off in the same manor as the square taper but there are different type of splines used depending on the manufacturer. Determining the exact type of end on your bottom bracket axle is critical to getting the proper crankset. After you have determined what type of parts you’re dealing with you will want to order the proper removal tolls at the same time that you order the parts. Basic tools required for this job will consist of common
hand tolls such as metric open-end or box wrenches as well as a 3/8 inch drive metric socket set preferably a six point, some penetrating oil,a medium sized ball paean hammer & a pair of pliers with some drifts or punches assuming your you’re working with cotter pins or roll pins. For square taper or splined axles you will need a crank tool remover designed for just that. They come in different styles & configurations. I prefer the Park universal crank puller M# CCP – 22. It cost $23.53 from Amazon. ( See TOOLS below ) it is a good universal puller that fits many different cranks. After your crankset has been replaced you will need to re-position your derailleur mount in order to accommodate the larger gears. Once you have determined the proper position you will need to re- tighten it and then make some final cable adjustments. This is a trial and error method and about the only way to easily do it is to get your rear wheel raised off the ground by a few inches you can also turn your bicycle upside down but because gravity will pull your chain in the wrong
When we move to the back wheel there are two things to take into consideration. If you have installed a front mounted E bike kit on your bike then the gears you’ll will be dealing with in the back will be the original gears that came with your bike. If we installed a rear mounted E bike kit it will have come with the gears all ready attached. Rear E bike kits will usually give you the option of ordering six, seven and sometimes an eight speed gear cluster. (you can usually order a single gear as well)There is generally not enough room to install a nine speed gear cluster. If you are determined to keep your original gears it may be possible to remove the gears from the E bike kit and replace them with your original gear cluster by changing or removing some spacers & spreading the chain rails out a little further. Keep in mind if you go this route the gear ratio is far more important to the overall performance of your E bike than having more gears. Most people riding E bikes are rarely using more than a few of their total gears. Re-calibrating your gear shifter to work with a smaller number of gears is really very simple and will not affect the quality of your shifting. It will however leave you with a ghost gear that does nothing. So let’s start with determining what type of gears you will need. There are essentially two types of gear clusters used with the two types of hubs that are available since the early 80′s. The traditional freewheel uses a set of the gears that have the freewheel mechanism in side of the gear cluster and this gear cluster along with the free wheel mechanism threads on to the rear hub this was common right up through the late 80s and early 90s until the newer style introduced by Shimano started to become popular. direction this does not always give you the best results. If your bicycle has a rear rack the easiest thing to do is to rest that rear rack on a small piece of wood that you have C-clamped to your workbench. this is easily done and works for many different situations I barely use my bike stand any longer. A good center stand can also work very well. If want to obtain higher gears than your stock derailleur & shifters where designed to work with & or you will be mixing & matching parts from different manufacturers I strongly suggest reading some of the following links below as I have covered only a very small part of the a bicycles gear train.
Starting with the traditional (older) rear hubs, they came with a standardized set of threads that screwed on to the freewheel style sprocket cluster. This had the advantage of allowing just about any brand of free wheel style sprocket cluster to fit on to your bikes rear hub. If you wore out your sprocket cluster or you wanted to change your gear ratio you could simply on screw the sprocket cluster and replace it with a new one. If you wore out your sprockets, or wanted different gear ratios, you could unscrew the cluster and install a new one. Since rear hubs seldom wore out the only reason for replacing a hub was if you bent or broke it.
Shimano Free Hubs however had the free wheel mechanism inside of the hub and the sprocket cluster slid on to a splined shaft protruding from the freehub. The name Freehub is actually a trade mark name licensed by Shimano. Changing either one is a very simple job the only difference is determining what you have and getting the correct tool. Once you have accomplished that, the job can take any where from 15 minutes to 45 minutes. As in any job, unless you have a well equipped shop, gathering your tools, parts and preparing your work area often takes more time than the job itself.
Now that you you know what I know please read some of the following websites starting with “Freewheel or Cassette” link for the specific repair, maintenance and modification of a bicycles drive train.
Bicycle Repair & Maintenance. Web-Sites, Blogs, Links
In my humble opinion the web site named after the bicycle mechanic and enthusiast Sheldon Brown is the Encyclopedia Britannica of the bicycle world. Although Sheldon Brown passed away in 2008 his work lives on through the Sheldon Brown website as well as the Harris Cyclery website which maintains a brick and mortar bike shop in West Newton, Massachusetts where Brown worked as the parts manager, webmaster and technical consultant for Harris Cyclery. He was an enthusiast for and maintained pages about old and classic bicycles and cycling. Brown was a dynamic individual and wrote for many magazines including Bike World magazine, (USA) Bicycling magazine, (USA) the trade magazine American and wrote the “Mechanical Advantage” column for Adventure Cyclist,with a wealth of information that goes far beyond bicycles. However his work on bicycles is what he is best known for & began during his childhood long before the Internet made us all experts just by typing a question into Google. If I have any complaints at all about Sheldon’s teaching methods he is sometimes a little overly technical and detailed for those of us that are a little lacking in our mechanical abilities.. His information however, is always spot on, current and he takes the time to offer the tips and tricks that he has learned over his many years of turning wrenches. I do not know Sheldon so my assessment of his work comes directly from following his advice with excellent results.. For Sheldon Brown’s home page just click Sheldon Brown & Click Harris Cyclery for their website which is also a full-fledged bike shop and carries a full line of bike parts and tools.
I’ll try not to list sites that have obvious financial ties but I consider the Park Tool Corporation an exception to that rule. Just keep in mind that there are many other very fine tool makers in the world but I do not believe any of them specialize in bicycle tools in the way that Park tool does.The Repair Help and Education Blog from Park tools is independent from the Park Tool tool Catalog. It is not in the least bit surprising that they specify their brand of tools in the repairs, but that fact that not with standing it is still an excellent reference source. Simply click “The Repair Help and Education Blog” and you will go straight to the source book.
This is not a completely free site. However it has two sections to it. The written instructions are relatively complete and they are free. It also has a video section which is available for a fee. I have not used the video section myself but judging from the written material I will assume that the video section is pretty good. And many people in this day and age are able to comprehend videos much easier than the written word.
Bicycling Magazine is first and foremost a bicycle magazine. However it does maintain a separate section for the repair and maintenance of your bicycle. These articles are well written by professional bicycle mechanics and are both easy to read and follow. As a magazine it contains plenty of advertisements but also includes useful reviews, interesting stories and some interesting insights to the current state of the bicycling industry. It is generally not my first choice for repair articles but it is well liked by the many people that do use it.
E-Bike Repair & Maintenance. Web-Sites, Blogs, Links
Endless Sphere is the hands down go to source for E.V.’s. That means they cover more than just E-Bikes but the information found there is both technical & practical & the discussions can get very detailed. I simply do not try or buy anything of any complexity or cost without searching through this forum first. It is an invaluable source of information ranging from where to get obsolete parts or has this type of E-Bike been invented yet. (And if it hasn’t some member will no doubt have plans for it already started.)
V Is For Voltage is another forum similar to Endless Sphere. It is however is dedicated to only e-bikes. It too is a good source of information.
Electric Bike.com is a Web-Site & Blog that covers a lot of custom E-Bikes builds. Loaded with photos & practical hands-on information.
ebike ca.com has been Involved in E-Bikes longer than most. With their brick & mortar shop “Grin Technologies” located in Vancouver Canada hey have been a true innovator with many of the products they have produced. Their web site is wealth of information much of it learned right there on the shop floor. My kind of company for sure.
E-BikeKit.com Blog This is the blog page for Electric Bike Technologies. They are located in PA & build one best & most complete E-BikeKits available. I use them almost exclusively in my e-bike business.
ElectricScooterParts.com Although not specifically focused on e-bikes it contains some useful calculators, conversion charts & electrical information.
Special Driveline Tools & Parts
Although there are many good websites on the repair and maintenance of bicycles on the Internet, there are also many bad ones. It is not my job to discourage anyone from exploring the wealth of information available on the Internet, however I have repeatably come across one website called “WikiHow to do anything” that contains information that is so incomplete, so bad & just plain wrong, that it could easily put you or your bicycle at great risk.
That said, “WikiHow to do anything” does seems to cover about anything & I have only focused on a small portion of the articles written about bikes & e-bikes. However, should you come across this webpage use the information at your own risk. That said I use Wikipedia almost daily and find it to be quite accurate. I have no idea if the two are related beyond the similar sounding names.
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