# 格兰诺拉麦片和货物崇拜

### 1 评论

• Alex Reinhardt

Hi guys,

Being an ex systems engineer (rockets/spacecraft for 21 yrs and medical devices for 14) , I love your podcasts! I really likely the conversation with Robert Chung; the first time I went through his math I thought, dang, why didn’t I think of that! But geez, why is this all so hard, isn’t the answer just 42??

Seriously though, I’m an average (not racing anymore) masters rider living in the Canadian (flat) prairies that still rides an old steel Raleigh team frame, albeit with new components. I just love how that frame rides and can’t justify the \$\$ to upgrade a bunch, the “\$/min” ratio on even a fast club ride is just not there!

So here’s my optimization quandary. Let’s say you have a given wheelset that is, for example, 24mm wide and 32mm deep that you don’t want to replace. With 25’s, that clearly doesn’t meet your 105% rule, but, it’s not horrible either. With the rough roads around here, 28 or 30’s would likely provide lower rolling resistance (given your comments on the podcast), but then the aero side goes farther to pot. I’ve tried to find some published data on relative contribution of front wheel drag vs total drag and that is not readily available/decipherable/believable from the myriad of articles on the net. Rolling resistance is easy to calculate so where is the sweetspot between aero and CRR for a given tire/wheel combination? The answer I know is it depends (a favorite of mine too), but systems wise, if you allocate x% of total aero drag to the front wheel, you can at least do the math of increasing front wheel drag by a given % = X watts at a given V which then equates to a CRR change of Y, and is Y consistent with what is achievable by changing from a 25 to a 28 or 30 or going down to a 23 or whatever? Somewhere the proportional to V vs V^3 tradeoff will happen. Also, this same thought process could get applied to the rear wheel but there, I’m thinking that biggest you can fit is likely best. The spreadsheet for that will be cool!

Anyway, the above topic falls in perfectly with your comment of “more gravel content” too….I can and do ride hundreds of miles of gravel from the end of our driveway! Keep up the good work and thanks!

Alex