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Ymmv

Old 08-06-13, 08:22 PM
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Planemaker
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Ymmv

When I started riding in March I thought a 5 mile ride was a lot. Five months later 30 miles seems like a walk in the park.


FYI - Switching to 28mm tires from 32mm tires seems to have increased my speed by greater than 1 mph and headwinds seem a lot easier.
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Old 08-06-13, 08:34 PM
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Did you set your computer for the new smaller tires?
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Old 08-06-13, 08:39 PM
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I have a Garmin 510 it senses the tire size but, I will check.
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Old 08-06-13, 08:46 PM
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Originally Posted by ericm979 View Post
Did you set your computer for the new smaller tires?
You buzzkill, you.
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Old 08-06-13, 09:06 PM
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Originally Posted by Planemaker View Post
I have a Garmin 510 it senses the tire size but, I will check.
It uses GPS to calculate your speed. It can't sense your tire size.


Anyway, good for you! That's good progress. The smaller tires should roll better if they run at higher pressure.
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Old 08-06-13, 09:25 PM
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Originally Posted by GeneO View Post
It uses GPS to calculate your speed. It can't sense your tire size.


Anyway, good for you! That's good progress. The smaller tires should roll better if they run at higher pressure.
Not sure how it works but, the tire size is set to Auto in the setup. I think what is does is constantly calculate the miles based on GPS miles and wheel revolutions. That being said my ride did seem that I had to go just a bit further to get my 10 mile marker.

I just did a check and the unit is calculating Auto2096 which according to Garmin is actually 23mm tire size, 2136 is the tire size for 28mm. So, I am actually going faster and further than I thought I was.
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Old 08-06-13, 09:42 PM
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Your progress is due to more to physical conditioning than to your tires. Congratulations! LIfelong fitness is what it's all about.
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Old 08-06-13, 09:49 PM
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If BF has a "kudos" button like Strava does, I'd give you one. Well done.
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Old 08-06-13, 10:18 PM
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I suspect that you're getting stronger and hitting heavier gears more often, that's what I suspect. When that rolling weight is lighter it usually makes for better acceleration more so than the steady pace.

So congrats.
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Old 08-06-13, 10:35 PM
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Originally Posted by Planemaker View Post
Not sure how it works but, the tire size is set to Auto in the setup. I think what is does is constantly calculate the miles based on GPS miles and wheel revolutions. That being said my ride did seem that I had to go just a bit further to get my 10 mile marker.

I just did a check and the unit is calculating Auto2096 which according to Garmin is actually 23mm tire size, 2136 is the tire size for 28mm. So, I am actually going faster and further than I thought I was.
I think you are right about how it calculates the wheel size. But if GPS is on it will use GPS to calculate your mph, regardless of the wheel size. It will use the wheel size and revs from the Cadence sensor if GPS is off. That is used to measure speed on trainer - where the GPS doesn't work because you aren't really moving.
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Old 08-07-13, 03:16 AM
  #11  
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Well done. Now imagine being on 23's.
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Old 08-07-13, 05:58 AM
  #12  
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Good stuff! Now are your golf scores coming down as well??
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Old 08-07-13, 09:05 AM
  #13  
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Ditch the 28's get yer self some 25's. You'll notice the difference.
And keep up the good work!
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Old 08-07-13, 09:25 AM
  #14  
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Congrats, went through the same process last year. Was huffing and puffing after 5 miles, now I do 20 miles most evenings after work and 35 or so on the weekends. Keep it up.
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Old 08-07-13, 10:01 PM
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Originally Posted by Planemaker View Post
Not sure how it works but, the tire size is set to Auto in the setup. I think what is does is constantly calculate the miles based on GPS miles and wheel revolutions. That being said my ride did seem that I had to go just a bit further to get my 10 mile marker.

I just did a check and the unit is calculating Auto2096 which according to Garmin is actually 23mm tire size, 2136 is the tire size for 28mm. So, I am actually going faster and further than I thought I was.

If you have the magnet and sensor installed the Garmin set on auto does calculate wheel diameter based off of the GPS distance calculations and the number of wheel revolutions. It uses the magnet if it loses satellite connections like in a tunnel, etc.
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Old 08-08-13, 05:51 AM
  #16  
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OK, I have done some research. If the wheel magnet is installed on the bike and the settings for the wheel size are set to auto to detect, the GPS will calculate the distance and automatically update the wheel size based on the number of revolutions the wheel makes over a GPS calculated distance. According to my research this is the most inaccurate way to set wheel size because the slight inaccuracies of the the GPS. The most accurate method is roll the wheel out on pavement several times, measure the distance each time, calculate and average distance and record that distance as the wheel size. The second most accurate method is to enter to measurements manually based on a chart provided Gramin.

One last thing if the wheel magnet is installed and working correctly the speed and distance are calculated based on the number of revolutions the wheel makes. If the speed/cadence sensor fails or the magnet is lost the GPS will calculate speed and distance. I actually proved this yesterday because I manually input my wheel size (auto detect had used 23mm tire and I input the correct size 28mm) and rode my normal route. The 10 mile point in my route was at a slightly different spot, closer than the day before.

The bottom line is that since installing 28mm tires my rides (33, 33, 25 and 50 miles) have all been faster. Part of it can be explained by better riding techniques like making sure I pedal an entire hill (I had a habit of trying to coast part way up and that really kills speed and once it is lost can't be regained while going up) but, some of it also has to be the narrower tires.
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Old 08-08-13, 06:08 AM
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The main thing is that you are improving, regardless of the cause. Knowing why will be helpful but, enjoying the improvement and being motivated to continue the improvement will be the big pay off. You are experiencing less rolling resistance most likely. Higher tire pressure and to a lesser degree the tire's quality and its rolling performance are helping along with the other aspects, like your pedaling efficiency. Good tires can make a great bit of difference in your performance, nothing drastic but you usually feel the improvement.

I try to run as good a quality tire as my budget will allow, right now that is the Continental Gatorskin in 700X25, in place of the original Schwalbe Lugano in 700X23. I went to the 25 width because the routes I ride most often have some long stretches of large diameter gravel in the paving topping and it is worn fairly badly. Some additional width helped me greatly. I usually run 110 psi in the rear and 100 in the front and have felt very good about the rolling feel and vibration abatement.

Bill
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Old 08-08-13, 06:21 AM
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Originally Posted by Planemaker View Post
OK, I have done some research. If the wheel magnet is installed on the bike and the settings for the wheel size are set to auto to detect, the GPS will calculate the distance and automatically update the wheel size based on the number of revolutions the wheel makes over a GPS calculated distance. According to my research this is the most inaccurate way to set wheel size because the slight inaccuracies of the the GPS. The most accurate method is roll the wheel out on pavement several times, measure the distance each time, calculate and average distance and record that distance as the wheel size. The second most accurate method is to enter to measurements manually based on a chart provided Gramin.

One last thing if the wheel magnet is installed and working correctly the speed and distance are calculated based on the number of revolutions the wheel makes. If the speed/cadence sensor fails or the magnet is lost the GPS will calculate speed and distance. I actually proved this yesterday because I manually input my wheel size (auto detect had used 23mm tire and I input the correct size 28mm) and rode my normal route. The 10 mile point in my route was at a slightly different spot, closer than the day before.

The bottom line is that since installing 28mm tires my rides (33, 33, 25 and 50 miles) have all been faster. Part of it can be explained by better riding techniques like making sure I pedal an entire hill (I had a habit of trying to coast part way up and that really kills speed and once it is lost can't be regained while going up) but, some of it also has to be the narrower tires.
Given the considerable differences in tires despite nominal sizes, I find that hard to accept. Charts provided by different speedometer makers give different recommended settings for the same tire sizes.

I don't think that's correct but I don't want to start a big argument over it. Can't remember my source.
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Old 08-16-13, 04:06 PM
  #19  
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Pushing pedals is better than pushing up daisies!!!!
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Old 08-17-13, 03:03 AM
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Originally Posted by billydonn View Post
Given the considerable differences in tires despite nominal sizes, I find that hard to accept. Charts provided by different speedometer makers give different recommended settings for the same tire sizes.

I don't think that's correct but I don't want to start a big argument over it. Can't remember my source.
Tire sizes are not standard, if you measure 3 different 25mm tires, you will often get 3 different actual measurements. Part of this is that a 24mm tire weighs less then a 25mm. In an industry where people will spend $500 on one component over another because it's 5g lighter, that 1mm cheating the width, can add up to a lot of sales. Another part of it, is that a tire rated at 90PSI and a tire rated at 110PSI will have a different squish factor, at those pressures therefore a different actual diameter.

If one manufacturers number is based on one tire, and another manufacturer is based on a different tire they could get different numbers for the same size tire. It's still going to be far better then the 5% your car's odometer is required to be, by law.

If your really anal about accuracy, the best way is to measure it. Using sidewalk chalk, and tires pumped to your normal riding pressure, get the valve stem at bottom dead centre, make a mark on the ground that lines up with the stem. Ride 5 revolutions, of the tire, make another mark with the valve stem in the same position. Measure with a metric tape measure to the nearest mm, if the only tape measure available is in inches, measure to the nearest 1/16th inch and multiply by 25.4. Divide the result by 5 and round to the nearest 1mm, this is the number you want. I measured mine, only because I didn't want one bike to have an advantage over the other.
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Old 08-17-13, 06:27 AM
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Just keep riding much further and a little faster. The fitness benefit is a result of regular effort, not equipment changes. Keep the bike comfortable and ready to ride and this will improve your fitness more than other equipment factors.
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Old 08-17-13, 06:36 AM
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Originally Posted by qcpmsame View Post
I went to the 25 width because the routes I ride most often have some long stretches of large diameter gravel in the paving topping and it is worn fairly badly. Some additional width helped me greatly. I usually run 110 psi in the rear and 100 in the front and have felt very good about the rolling feel and vibration abatement.

Bill
Ditto on the reason for using 25's. I find a noted increase in performance in light sand/gravel with the 25's over the 23's and especially over 20's or 19's. I have a couple of sections with gravel/sand on one of my routes - about a mile - and the 25's do just fine.

Due to my "heft" I keep everything at 120 psi.
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Old 08-17-13, 07:44 AM
  #23  
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Originally Posted by rydabent View Post
Pushing pedals is better than pushing up daisies!!!!
Amen.

To the OP...congrats.
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Old 08-17-13, 10:03 AM
  #24  
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My understanding is similar to that described by GenO. If the cadence sensor is on, then the Garmin calibrates the wheel circumference by comparing the wheell revolutions to the distance indicated by GPS. This can be quite accurate if the Garmin averages a significant number of individual measurements (I don't know how many it uses). Except perhaps on a trainer, the Garmin does not care about the width of your tire. In fact, comparing the GPS distances to wheel revolutions should be more accurate than the measuring methods that several of you have mentioned because the Garmin is measuring the diameter of the wheel whilst you are riding it and hence whilst the tire is compressed by your weight.

Even if the uncertainty in an individual GPS measurement produces low accuracy in calculated speed, it is a random error, so with many measurements, the accuracy of this kind of calibration can be quite high.

Great going Planemaker - I am sure you'll think more about enjoying your longer rides and your improved fitness than the silly details of exactly how fast you are going.
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