I am asking after use of e bikes for certification. Wondering what bikes are the best for this procedure. Any advice is useful.
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I don't have an e-bike, but there may be some benefits. You would of course have to be able to mount the Jones Counter and it would also be important that it has skinny high pressure tires. I think that those e-bikes with fat tires should not be used as the temperature variation of the working constant may be too great.
Hi Gary,
Sorry I missed your post. I have been using an e-bike for about a year now. Its made by a company called SERFAS. I can tell you that overall my experience is positive. I usually measure at about 15mph (which is faster than I can pedal) but the bike does go faster. I think the biggest impact it has had is the improvement when starting out from a standstill. On my old self-powered Trek, when I was beginning to pedal from a hard stop or if I was on an incline, there would be some wobble in the front tire, with the e-bike, that beginning wobble is gone...the throttle power eliminates it. Thus helping to ensure a more accurate course. On my bike, the seat is very comfortable compared to the thin road bike seat from my Trek. This has become increasingly important as I get older!! I also added a rear (on the advice of the LBS owner) basket. The rear basket is perfect for carrying the stuff that I used to haul in a backpack.
Obviously, courses are measured quicker with the e-bike, which is nice because time is money!
The downsides: Weight: the bike is heavy, bulky and I have to remove the battery to put it on the bike rack on my car. The battery doesn't add too much weight but it takes up space on the frame thus the need to remove it to get it on the rack. Wider front hubs: I had to look for a long time to find a bike that would accommodate a right side (disc brake) Jones counter. I don't know if this is an industry wide shift for all bikes or if it is specific to the e-bike industry but almost every bike I looked at would not tolerate a Jones Counter.
Another positive I forgot to mention is that I now ride my bike around town a lot more. If I need something from the store, it is much quicker to jump on my bike and ride there than deal with the vehicular traffic.
The E-bikes I have seen have GREAT BIG tires which takes me back to bad experiences with second measurement agreement. What has your experience been?
Robert, may I ask what model is the SERFAS that you found accepted the right side Jones counter?
It is the SERFAS E-DART 500. I just checked the website and it looks like this model is no longer in production. This looks like the replacement:
https://www.serfas.com/shop/pr...0w-e-bike-step-over/
Hope this helps.
@oscarwagner The tires are definitely wider than a traditional road bike and I must admit that I like the added stability they offer. For measurement, I have found that keeping the tires inflated to the maximum air pressure is the best bet. I have not had any verification ride or post calibration discrepancies, but I do check the tire pressure at the beginning of every measurement day. Most of my measurements are 5k solo rides but I did measure a half with a collaborator and we came up spot on. Overall, it has made me more "counter-productive"!! Sorry, couldn't help myself with that one. 
What nominal pressure do you target?
The ideal gas law says the change in pressure for a given change in temperature will be the same regardless of the size of the tire or the initial pressure.
There may be a difference between two different tires in the way their calibration constants change as the temperature changes, but it is not due to a difference in how much the pressure changes between the two.
Big wide tires tend to have thicker tread(and often knobby tread), and the material properties of most rubbers change significantly with temperature, so that can change the calibration constant. But a big wide tire with thin smooth tread will result in a calibration constant that probably won't be more sensitive to temperature change than a small narrow tire with thin smooth tread.
@oscarwagner The tires are manufactured by Kenda and the max recommended pressure is 50psi. These are not knobby trail tires. The are made for riding on the street. You can find the full specs of the bike at the link above.
Also, I feel I should point out that the selling point of e-bikes is the ability to move forward under its own power, not the bike or more specifically, its components. I found during my research that the lower end e-bikes (the ones in my price range) had lower end components, therefore, shifting gears is not always a smooth operation. That being said, I don't shift gears all that much. If I ever find the need to get into a lower gear, I generally just use the throttle to assist. So the components are really just a nit-picking issue.
I hope all of this info helps. I really do think e-bikes are the future for us measurers, especially the aging ones, like myself.
Here is a link to the tire:
@Admin posted:The ideal gas law says the change in pressure for a given change in temperature will be the same regardless of the size of the tire or the initial pressure.
There may be a difference between two different tires in the way their calibration constants change as the temperature changes, but it is not due to a difference in how much the pressure changes between the two.
Big wide tires tend to have thicker tread(and often knobby tread), and the material properties of most rubbers change significantly with temperature, so that can change the calibration constant. But a big wide tire with thin smooth tread will result in a calibration constant that probably won't be more sensitive to temperature change than a small narrow tire with thin smooth tread.
I agree with you, that with the same starting pressure the pressure change would be the same for the same change in temperature (PV=nRT). But, do you think that the diameter of the tire will change more on a fat tire than an thin one, given the same change in pressure?
That is kind of the reason I asked the question about starting pressure. They look huge. Mountain bikes run a nominal 65 PSI. I saw a picture of a Pete Riegel bike with a Jones Counter on the front hub. Figured that must be the right one and ran out and got one. First ride on a cloudy day was OK. Then on a clear, fast heat up day (and this is on a 5K) agreement was so bad I had to reride one of the miles. Put a 65 yo 95 on same bike and had same kind of problem running it at about 80 PSI on an 8 mile out and back. After that, I ran a 120 PSI or airless.
"But, do you think that the diameter of the tire will change more on a fat tire than an thin one, given the same change in pressure?"
When you sit on a bike a small part of the tire flattens out and the tire is no longer a circle, so there isn't really a "diameter" of the tire. What you really want to know is how much the perimeter of the tire changes when you sit on the bike, and also when there is a change in pressure.
How much the perimeter of the tire changes as a function of the mass on the bike, the width of the tire, the pressure in the tire, etc. is quite complicated. There was a thread many years ago when Mike Sandford and I discussed parts of this. I'm traveling right now, but when I return I will try to find that old thread and then we can try to figure out the answer to you question.
YES, I do think it will. The first lesson in calculus is the concept of a limit - what happens if you take a situation to extremes? In this case, what would happen if you compared an airless tire to a marshmallow tire? It would be like the difference you see riding uphill versus downhill. The back tire compresses going uphill from the shift in body weight so the front tire will show fewer counts. We were shown this at measuring seminar in Akron in 2017. My hard personal experience is that a 50 lb tire (designed for rider comfort) would have a much bigger problem with agreement than a 120 lb tire (designed for efficiency of effort).
As much as an argument for/against e-bikes for certification measurements, this discussion appears to me to also constitute a recommendation for solid tires, such as Duane Russel used to use.
A potentially better solution using NASA - developed shape memory alloys: https://www.smarttirecompany.com/cycling . The SMART Tire company claims its bike tires will last and will perform well indefinitely without failing.
"The estimated price for the METL™ bicycle tire is $100-$150 at launch, or competitively priced as an integrated high-end wheelset. METL airless tires will be available to order Q4 2023, sign up today for our wait list."
FYI - I have no financial interest in this company or its products.
I have several solid rubber tires in storage because I never could get them to fit or find a rim to fit them. SO be very careful and lucky what you pay $100 for.
The Smart Tire folks say they sell entire wheel & tire combinations only, so this seems like a plus.
Here is the tread from years ago that I mentioned above.
https://measure.infopop.cc/top...3#585516546019974693
Unfortunately the equations and diagrams in that thread are now lost. I'm going to contact the host company of our forum to ask why. However, Mike references his 1998 article in Measurement News that gives the equation for the "effective radius" of a rolling bicycle tire. As you can see in the thread he finally managed to penetrate my thick skull and convince me that his equation was correct.
The effective radius of a rolling tire all depends on the behavior of the contact patch. If there is a "stick" condition in the patch, meaning that as soon as a point on the tire touches the road surface it sticks to that point, then the length of the tire in the contact patch shortens, and the "effective radius" of the tire is smaller than the original radius of the tire. This is the situation for which Mike's equation applies. At the other extreme is the case where there is no friction between the road and the tire, or the tire is so strong that the friction with the road is not great enough to cause it to compress, there is no shortening of the contact patch, and the "effective radius" is the same as the original radius. The actual answer probably lies somewhere between these two extremes.
Note that this is most likely why it has been observed that cal constants on unpaved surfaces are always smaller than cal constants on paved surfaces. Unpaved surfaces have less friction than paved surfaces, which means there is less shortening of the contact patch, which in turn means the effective radius is larger than the effective radius of the paved surface case. Larger effective radius means smaller cal constant. This is why people say if you calibrate on a paved surface and then measure a course on an unpaved surface, the course will be long.
At the end of the thread mentioned above people asked what is the practical significance of all of this theory. In this thread we may be able to see some practical significance to understanding the theory behind calibration constant variations. In practical terms, we would like to understand what tire setup will result in the smallest change in cal constant as a function of temperature. Is a wide or narrow tire better? Is initial high pressure or initial low pressure better? Are airless tires better than pneumatic? Understanding the theory of what causes cal constants to change can probably help answer those first two questions. Because the third question depends mostly on material properties which are unknown, it will probably require some experimentation.