A lot of smart people on this thread so going to throw out another scenario.
Unbound is happening this Saturday. Alexey Vermeulen, who rides on ENVE wheels said he feels at the speeds the pros will be riding that aero wheels still matter and he will like run Enve 4.5s likely with a 40 or 42nm tire rather than the light and more compliant, but non-aero G23.
My understanding is if you mount a 40 or 42 on an aero wheel like the 4.5s, that pretty much all the aero benefit is negated. Or is there still some benefit in a situation where the pros may be in the 20 - 25 mph range at times.
Bumping this thread as Iām pondering a new set of wheels for my road bikeā¦
In one of the Escape Collectiveās Performance Process episodes a while back one of the guys from Swiss Side made a comment to Ronan that they didnāt feel that the rule of 105 was as big of a deal anymore based on their testing. Then the other day I came across Huntās white paper for their Sub 50 wheels. They had data from a lot of different width wheels and tried 28mm tires and 30mm tires (and measured the actual tire width on each rim). Hereās a link to their white paper. And a few snippets of data below:
Rim widths to put the above in context
Roval Rapide CLX: 35/30.7 mm
Enve 4.5: 32 mm
Hunt Sub50: 34/30 mm
ZIPP 454 NSW: 27.8 mm
Dura Ace C50: 28 mm
In the appendix at the bottom of the linked paper they do also list a number of other wheels they tested including the DT Swiss Dicut 50 (27 mm external I believe). It was 2-3 watts slower with the 30 mm vs the 28 mm
I remember this. Basically, with how modern rim shapes are, they should be less sensitive to slight violations of the rule of 105 than older rims.
I have 2019-ish rim brake carbon wheels now. Iām definitely violating the rule for comfort, and Iād expect this generation of wheels to still be a bit sensitive to the Rule of 105. I expect I would be losing something like 4W or less at 45 km/h versus a 25mm tire.
To test the 105 rule we need to pick a tire and put it in wheels that are identical except in rim width. Then do it for different tire sizes and models.
Thatās not feasible because most wheel models are only available in one width.
Now, if you take a wheelset and test different tire sizes, you can find gains or losses regardless of the rule of 105. However, that is not a test of the rule per se.
Not sure I agree with that. Per Josh Poertner āThe Rule of 105 states that the rim must be at least 105% the width of the tire if you have any chance of re-capturing airflow from the tire and controlling it or smoothing it.ā
So to test it you could compare a tire width that allows the rim to follow the rule and then compare it to a a narrower tire width that does not allow the rim to follow it. You could theoretically use a whole batch of tire sizes to see if there is a different between 105% and 110% etc.
But I think at the heart of it is that for decades aeroweenies have tried to get a rim/tire combo that follows Joshās rule in order to maximize gains. But current school of thought based on testing more modern shaped rims is that the differences between a 100% and a 105% combo are minimal and likely within the margin of error of a wind tunnel
Latest from Swiss Sideās Jean-Paul Ballard claims that 105% Rule is an aero myth based on their wheels and tire testing. I get that Josh is a big industry name who has generously shared tons of valuable guidance to the cycling community, and he is seen by many as the godfather to modern tire knowledge.
But like Josh, Jean-Paul has been sharing tons over the recent years with a focus on the aero front. Jeanās results and takeaway of āthere are no observed rule of thumbs (yet)ā intuitively sits much better with me, given the unpredictable nature of aerodynamics.
Yeah, but in those cases youāre changing the frontal area of the tire. Granted, if you put the same tire on different rims the area is also going to change.
The latest? That is from February and heās the only person in the industry suggesting this. And it says:
āJP doesnāt believe the rule of 105 is as critical as we once thoughtā
Well, that doesnāt mean not valid or invalidated.
Iāve seen zero data that suggest this idea is dead.
The thing is, for us recreational and amateur punters, it just doesnāt matter that much. The 105% rule is for those doing events at the highest levels. It always was. It was never a blanket recommendation.
For amateurs, the take home message is donāt create a big light bulb profile if you want to maximize aero (like a 28mm tire on a 23mm rim - back when this idea was born.) Now a days, that might mean a 32mm tire on a 28mm rim.
FLO clouds the issues in this blog:
The data clearly shows that the smaller tire is faster but then they mix in rolling resistance and conclud that the wider tire/wheel is the fastest package. But they donāt mentioned tire pressure. We know that wider tires at the same pressure as narrow tires will be faster (BRRās site). We also know that when you run less pressure in the wider tire, rolling resistance equalizes (again BRR). And in reality, people donāt run 28-30-32mm tires with high pressures to maximize rolling resistance.
I donāt see where maxim809 said it is dead. But rather implying via JP Ballard that itās not the golden rule that everyone felt they needed to follow for decades. Did you happen to read the white paper I linked to in my post? It is certainly not the end-all be-all, but there is some interesting data to glean from there about the effects of tires and rim size. In some cases the 30mm would follow the rule of 105 while the 28mm wouldnāt and the difference was quite small
Though it doesnāt have the ring of āthe rule of 105ā much of this and my impressions from Portnerās tone during a couple recent āask josh anythingā podcasts suggests more a āguideline of 105ā and less a rule. It even sounds like when it comes up he has the tone of āthis has gotten out of hand.ā From my interpretation for the most part it seems if you need to wring every last āfreeā watt out of the system for every possible gain then yes, 105ing or better is something to strive for. But thatās for specific yaw angles and doesnāt always apply. And as was said in above posts being at 1:1 tire width the rim width is not far off, difference of a watt or 2 maybe and that varies based on wind conditions. I doubt most of us could feel or would suffer because of leaving at most 5 watts on the table.
The title of the thread suggests that the 105% rule may be invalid. Iām not picking on Maxim other than weāve been discussing the JP Ballard comments for months so they arenāt new.
I looked at that white paper. Regardless of 28 or 30mm tires, the tire width is still less than the rim width and still in line with the spirit of the 105% rule. If the rims are 33-34mm wide, then it just doesnāt matter much whether you use a 28mm or 30mm tire.
The other thing that stands out in the conclusion is that there is less than a 1 watt difference between the various rims.
32-622 on the Conti S TR box, measure 32.8mm wide on 21mm IW / 35mm/30.7mm EW wheels.
More #gainzzz on crappy pavement = less rolling resistance. See NorCal Cycling tire size shootout on these wheels for why I say that (until I get a chance to test myself).
Having ridden 26c, 28c, and 30c and 32c tires on the Tarmac, I agree with their results. At least on the roads out here. I tried a 28c recently and it felt harsh, removed it immediately and bought another 32c S TR.
Respectfully, whatās the aerodrag percentage from the wheel of the whole system? More or less than 5%? I know they kept the rest the same but there are still variables you canāt account for. Iām all for wide tyres but other sources test narrow wheel, narrow tyre combos faster than the rovals. So whoās right and whatās faster? I personally prefer comfort of a wide tyre over the last watt advantage. I just race myself
The NorCal Cycling tests are testing both aero and rolling resistance. Plus itās a stop watch test and not very scientific. They show at least that you arenāt losing anything by going with wider rubber on a Roval.
