Comparing Wheels in Profile 4

Post Reply
AN2019
Posts: 37
Joined: Sat Oct 05, 2019 6:31 pm

Comparing Wheels in Profile 4

Post by AN2019 »

If the following conditions are met, can I compare different wheels using data collected on different days?

-Same bike, rider, clothing, closed loop

If so, how much data (i.e., how many loops) should I collect with each wheelset?

I would be looking at each wheelset as a system (i.e., using the tires for which each wheel is best suited. An example would be the new Enve SES 4.5s with tubeless 29c Enve tires at 70psi versus Roval Rapide CLs with 26c S-Works clinchers at 85psi and a latex inner tube.

There’s gonna be no way to access all of the wheels I’m considering on the same day unfortunately. I’d probably do the baseline calibration with the Rapide CLs and latex tubes.

Is this a crazy idea? Might it give me a good sense of which system is fastest for my bike, me, and my area (if I hold rolling resistance constant in Isaac)?

The closed loop is mainly flat, can probably be done without braking and has representative road surface for around here. If one or two loops get ruined by cars can I discard that data?

Thanks!!!!!
Velocomp
Velocomp CEO
Posts: 7793
Joined: Fri Jan 11, 2008 8:43 am

Re: Comparing Wheels in Profile 4

Post by Velocomp »

AN2019 wrote: Fri Jul 22, 2022 9:08 pm If the following conditions are met, can I compare different wheels using data collected on different days?

-Same bike, rider, clothing, closed loop

If so, how much data (i.e., how many loops) should I collect with each wheelset?

I would be looking at each wheelset as a system (i.e., using the tires for which each wheel is best suited. An example would be the new Enve SES 4.5s with tubeless 29c Enve tires at 70psi versus Roval Rapide CLs with 26c S-Works clinchers at 85psi and a latex inner tube.

There’s gonna be no way to access all of the wheels I’m considering on the same day unfortunately. I’d probably do the baseline calibration with the Rapide CLs and latex tubes.

Is this a crazy idea? Might it give me a good sense of which system is fastest for my bike, me, and my area (if I hold rolling resistance constant in Isaac)?

The closed loop is mainly flat, can probably be done without braking and has representative road surface for around here. If one or two loops get ruined by cars can I discard that data?

Thanks!!!!!
This is a tricky one.

For the wheel comparisons to be valid you will need to:

1) Make sure that your tires are inflated to the same tire pressure.

2) Ideally, you should also use the same kind of tire, both brand and size.

The purpose of these cautions is to get the same rolling resistance (Crr) from your various wheel setups. That way, any measured differences will be a result of varying CdA between wheel sets .

Do your testing in profile 4.

I would recommend 5 tests per wheel set. Yes, you should ignore tests where traffic zooms by.

It will be very interesting to see your results; please post them when you have completed them!
John Hamann
AN2019
Posts: 37
Joined: Sat Oct 05, 2019 6:31 pm

Re: Comparing Wheels in Profile 4

Post by AN2019 »

I will do my best!

I suppose one idea from the proposed testing is to fold in the differences in rolling resistance as part of a total system efficiency standpoint. I’m starting to sound like a commercial for Enve or Zipp now.

What I mean is that I know there are going to be some rolling resistance differences between the 29c tubeless tires I’d use on the Enve hookless wheels I have for the moment (at 65psi) and the 26c clincher tires I have on the Roval wheels that came with the bike (at 85-90psi). Not only can I not run tubeless tires on the Rovals, I can’t run clinchers on the Enves and I can’t exceed 80psi.

If I leave the RR figure the same between tests, then any differences in CdA should reflect both aerodynamic differences but also RR differences between the setups, i.e., which system is faster on the local roads here with me and my bike. Or have I completely lost my mind?
Velocomp
Velocomp CEO
Posts: 7793
Joined: Fri Jan 11, 2008 8:43 am

Re: Comparing Wheels in Profile 4

Post by Velocomp »

AN2019 wrote: Sat Jul 23, 2022 12:34 pm I will do my best!

I suppose one idea from the proposed testing is to fold in the differences in rolling resistance as part of a total system efficiency standpoint. I’m starting to sound like a commercial for Enve or Zipp now.

What I mean is that I know there are going to be some rolling resistance differences between the 29c tubeless tires I’d use on the Enve hookless wheels I have for the moment (at 65psi) and the 26c clincher tires I have on the Roval wheels that came with the bike (at 85-90psi). Not only can I not run tubeless tires on the Rovals, I can’t run clinchers on the Enves and I can’t exceed 80psi.

If I leave the RR figure the same between tests, then any differences in CdA should reflect both aerodynamic differences but also RR differences between the setups, i.e., which system is faster on the local roads here with me and my bike. Or have I completely lost my mind?
Presumably you're trying to assess CdA differences between wheel sets. There are two challenges:

1) My (biased) suspicion is that there is very little CdA difference between wheel sets. If true, you’ll need super-accurate tests to see small CdA differences.

2) CdA measurements will be affected by any differences in the actual rolling resistance Crr of the two wheel sets, so you’ll need to account for Crr differences in your testing.

The only thing I can think of is to create a "reference" Crr, say using your Enve wheels. With the tires and tire pressures you're using on your Enve, look up the manufacturer's Crr, and use that number in your profile 4 setup. Let's suppose that number for wheel set 1 is Crr = 0.0042

Also, you’ll need to find the Crr for the second set of wheels. Let's suppose the second set is Crr = 0.0039

Now, do your testing of wheel set 1 (say, Enve), making sure to enter the Crr of the Enve in the profile. Transfer that profile to your AP, then do five separate tests.

Then, use Isaac to adjust your profile 4 to the Crr of wheelset 2, transfer the profile to your AP, then do 5 tests of the second wheel set.

When you’re done post your ride files and I will take a look!
John Hamann
Post Reply