Crr Comparison - Tufo Tape vs. Mastik 1

Triathlon Forum
1

Might be of interest: http://biketechreview.com/...c.php?f=1&t=2478

The Tufo tape used on the tested wheel was the Extreme (clear) tape not the standard tape as I originally thought.

2

Thanks Al! Good stuff. Any idea how long ago the taped tire was installed vs. the glued tire? I wonder if the Extreme Tape tests any different than the standard.

3

Thanks Al! Good stuff. Any idea how long ago the taped tire was installed vs. the glued tire? I wonder if the Extreme Tape tests any different than the standard.

The glued tire was tested after 2 months and the taped was tested after 8 months. Not sure about the differences between the standard and extreme tape ?? Thicker and softer I would guess would be going in the wrong direction.

4

Thanks Al! Good stuff. Any idea how long ago the taped tire was installed vs. the glued tire? I wonder if the Extreme Tape tests any different than the standard.

Please see the correction above - the tape used on the wheel I tested was actually the clear Extreme tape not the standard which is yellow ??

5

So what does the .0002 in difference mean in the real world. Are we talking seconds in an IM or minutes?

6

So what does the .0002 in difference mean in the real world. Are we talking seconds in an IM or minutes?
While the exact differences varies with your speed and mass, a rough rule-of-thumb is that a 0.0005 difference in Crr equates to a 0.5 s/km difference in time. The reported difference in Crr would therefore theoretically result in a 36 s difference in the time required to complete an IM distance bike leg.

7

thanks Al!

8

Thanks for supplying so much information over the years. I appreciate it and have made equipment choices based on it.

I do have a quick question about the relationship between Crr and rider/bike weight… (hope it makes senses)

Is the test Crr of a tire/tube combo more, less or equally important to a rider as their rider/bike weight goes up and/or down?

I assume Crr goes up as the weight of the rider/bikes goes up.

IOW - do the relative differences between different tire/tube combos get further apart or closer together for a 220 lbs rider/bike when compared to a 170 rider/bike?

Thanks.

David K

9

Happy to help although Harvey Nitz told me that the results on BTR are full of sh** last weekend (:-). He is a nice guy and was embarrassed when I disclosed that I had done all the testing. He was very busy at the time so I’m trying to find his email to continue the discussion - we both might learn something.

We always assume that Crr (coefficient of rolling resistance) is a constant. Their is data showing a possible dependence of Crr with ground speed but that might be an effect of wheel aerodynamics on the rollers ?? There have been discussions on some of the other forums.

Assuming a constant Crr the relationship of power required to roll the tires is linear with respect to load (total weight) supported by the tires – Power = Load X Crr X (ground speed). So if your weight goes up it take more power to roll the tires at a given speed. The A in CdA also probably goes up so the aero losses increase as well. But the added weight might result in greater power supply.

10

Thanks a lot. So, in an attempt to paraphrase…

Whether you weigh 130 or 200 (plus a 20 lbs bike) the fastest tire/tube combos are the fastest and the slowest are the slowest and the relationship between fastest and slowest stays the same.

Thanks again.

David K

11

Thanks a lot. So, in an attempt to paraphrase…

Whether you weigh 130 or 200 (plus a 20 lbs bike) the fastest tire/tube combos are the fastest and the slowest are the slowest and the relationship between fastest and slowest stays the same.

Thanks again.

David K

Correct. Crr is just the ratio of the “retarding force” divided by the weight force. So, as the rider weight varies, the retarding force also varies in proportion to the Crr ratio. Make sense?

So, in practical terms, for a given Crr tire/tube combo, the “retarding force” is going to be higher for a heavier rider than a lighter rider (Force = Mass x gravity x Crr). That means that rolling resistance effects become are more of a concern for the heavier rider since it will be a slightly higher percentage of the overall drag (rolling resistance + air resistance).

12

Thanks. The last bit is the thing I was wondering about…

That means that rolling resistance effects become are more of a concern for the heavier rider since it will be a slightly higher percentage of the overall drag (rolling resistance + air resistance)
**
David K

13

Thanks. The last bit is the thing I was wondering about…

That means that rolling resistance effects become are more of a concern for the heavier rider since it will be a slightly higher percentage of the overall drag (rolling resistance + air resistance)
**
David K

It’s too bad it wasn’t properly formed English though :wink: