Ditching the aero bike

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Ytse
Posts: 287
Joined: Thu May 05, 2022 11:53 am

by Ytse

CampagYOLO wrote:
Mon Aug 08, 2022 10:17 am
hannawald wrote:
Mon Aug 08, 2022 9:30 am
TriJoeri wrote:
Mon Aug 08, 2022 9:01 am
SixThirteen wrote:
Mon Aug 08, 2022 1:53 am

When you are going uphill, even in the Alps, are you usually doing more than 15 kph*? If so then even going uphill aero trumps weight for all values of reasonable weight, given this forum.

* I can't find the reference right now, I think maybe its a video. This is also fairly informative https://www.swissside.com/blogs/news/ae ... ?locale=en
I'd say between 12 and 16kph except for the really steep bits. But as one other member said, I'm probably going to lighten up a few things (thru axles, derailleur hanger, found a carbon saddle that saves 100g and then possibly I'll buy the Hunt 32 aerodynamicist wheelset which saves 500g compared to my Reynolds wheels). Then I'm already saving 6-700g and I won't be compromising on aero too much.
32mm wheels on aero frame will look ugly, you can´t do it to your bike:)
Agreed, probably a 45mm minimum IMO with a Systemsix frame.

Also those Hunt wheels are so old school with a 25mm outer width, best of luck finding tyres that comply with the 105% rule with those narrow rims. They clearly went super narrow to chase low weight.
105% rule is not applicable, according to some wheel designers / manufacturers when rims are that deep (eg 50mm). You'll probably lose only 1-2 watts using 28mm tyres on a 25mm wide rims, meanwhile ride comfort will be night and day. If you are not chasing the last 1% to win a TT or crit, forget about 105%.
2020 Scott Addict RC / 2021 Trek Emonda SLR / 2023 Specialized Tarmac SL8

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C36
Posts: 2471
Joined: Fri Mar 03, 2017 3:24 am

by C36

Ytse wrote:
CampagYOLO wrote:
Mon Aug 08, 2022 10:17 am
hannawald wrote:
Mon Aug 08, 2022 9:30 am
TriJoeri wrote:
Mon Aug 08, 2022 9:01 am
I'd say between 12 and 16kph except for the really steep bits. But as one other member said, I'm probably going to lighten up a few things (thru axles, derailleur hanger, found a carbon saddle that saves 100g and then possibly I'll buy the Hunt 32 aerodynamicist wheelset which saves 500g compared to my Reynolds wheels). Then I'm already saving 6-700g and I won't be compromising on aero too much.
32mm wheels on aero frame will look ugly, you can´t do it to your bike:)
Agreed, probably a 45mm minimum IMO with a Systemsix frame.

Also those Hunt wheels are so old school with a 25mm outer width, best of luck finding tyres that comply with the 105% rule with those narrow rims. They clearly went super narrow to chase low weight.
105% rule is not applicable, according to some wheel designers / manufacturers when rims are that deep (eg 50mm). You'll probably lose only 1-2 watts using 28mm tyres on a 25mm wide rims, meanwhile ride comfort will be night and day. If you are not chasing the last 1% to win a TT or crit, forget about 105%.
Few points
- the effect will be particularly visible on high yaw angles with more drag and stronger, more irregular, torque returns on the handlebar.
- the tire width and comfort… that’s not how physics work. A large tire inflated at the same pressure than a narrower tire will be way harder, a large tire with the pressure adjusted to its width will have the EXACT same confort level (same spring rate, same impedance losses). A wide tire will allow to go MUCH lower in pressures with less risk to snakebite it and that where you gain confort, a narrower tire could do it but with a risk to pinch.

Ytse
Posts: 287
Joined: Thu May 05, 2022 11:53 am

by Ytse

C36 wrote:
Mon Aug 08, 2022 1:06 pm
Ytse wrote:
CampagYOLO wrote:
Mon Aug 08, 2022 10:17 am
hannawald wrote:
Mon Aug 08, 2022 9:30 am


32mm wheels on aero frame will look ugly, you can´t do it to your bike:)
Agreed, probably a 45mm minimum IMO with a Systemsix frame.

Also those Hunt wheels are so old school with a 25mm outer width, best of luck finding tyres that comply with the 105% rule with those narrow rims. They clearly went super narrow to chase low weight.
105% rule is not applicable, according to some wheel designers / manufacturers when rims are that deep (eg 50mm). You'll probably lose only 1-2 watts using 28mm tyres on a 25mm wide rims, meanwhile ride comfort will be night and day. If you are not chasing the last 1% to win a TT or crit, forget about 105%.
Few points
- the effect will be particularly visible on high yaw angles with more drag and stronger, more irregular, torque returns on the handlebar.
- the tire width and comfort… that’s not how physics work. A large tire inflated at the same pressure than a narrower tire will be way harder, a large tire with the pressure adjusted to its width will have the EXACT same confort level (same spring rate, same impedance losses). A wide tire will allow to go MUCH lower in pressures with less risk to snakebite it and that where you gain confort, a narrower tire could do it but with a risk to pinch.
Totally agree with your point about tyre width. I thought it is kind of obvious that someone chooses a wider tyre over a thinner one because of the ability to ride it on lower pressure leading to increased comfort.
2020 Scott Addict RC / 2021 Trek Emonda SLR / 2023 Specialized Tarmac SL8

ricerocket
Posts: 596
Joined: Mon Sep 27, 2010 8:38 am

by ricerocket

CampagYOLO wrote:
Mon Aug 08, 2022 10:17 am
Also those Hunt wheels are so old school with a 25mm outer width, best of luck finding tyres that comply with the 105% rule with those narrow rims. They clearly went super narrow to chase low weight.
Ha. I love how 25mm outer is "so old school" now. :)

CampagYOLO
Posts: 706
Joined: Thu May 06, 2021 3:58 pm

by CampagYOLO

ricerocket wrote:
Mon Aug 08, 2022 2:23 pm
CampagYOLO wrote:
Mon Aug 08, 2022 10:17 am
Also those Hunt wheels are so old school with a 25mm outer width, best of luck finding tyres that comply with the 105% rule with those narrow rims. They clearly went super narrow to chase low weight.
Ha. I love how 25mm outer is "so old school" now. :)
I feel it is when we're talking about carbon wheels that are a very recent design.
Also these are under Hunt's banner of "Aerodynamicist" which is probably just marketing but suggests that aerodynamics played a factor in their design.

calleking
Posts: 386
Joined: Sun Sep 13, 2015 3:20 pm

by calleking

I'm also of the opinion that weight is something that starts to become important once the gradient gets steep. A light bike feels great but is far from the fastest option as an all-rounder and like someone pointed out the weight difference isn't that big compared to the performance additional aerodynamics give you.

I'm very tempted to find a SystemSix frameset (54cm Hi-Mod) and cherry pick parts over the winter. Had a 2019 SystemSix Ultegra stolen last fall as I was coming back from being brutally hit by a car last summer. Anything below 7,5kg would be grea as I don't thinkt there is any weight weenies seatpost for this frame.

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Hexsense
Posts: 3270
Joined: Wed Dec 30, 2015 12:41 am
Location: USA

by Hexsense

ricerocket wrote:
Mon Aug 08, 2022 2:23 pm
CampagYOLO wrote:
Mon Aug 08, 2022 10:17 am
Also those Hunt wheels are so old school with a 25mm outer width, best of luck finding tyres that comply with the 105% rule with those narrow rims. They clearly went super narrow to chase low weight.
Ha. I love how 25mm outer is "so old school" now. :)
It kinda is. Considering my wheels in 2015 is already 28mm wide.
7 years later when 23c tires are no longer common, and someone still release rim that is best pair with 23c tires.

RimClencher
Posts: 195
Joined: Tue Jan 14, 2014 1:00 am

by RimClencher

If your Conti Race inner tubes are not the "light" version they are about 100 g each.
Replacing with TPU tubes (RideNow or something more expensive) saves 130 g plus rolling resistance gains (and 10 g for valve extenders when you have shallower rims).

choochoo46
Posts: 180
Joined: Fri Mar 15, 2019 4:19 am

by choochoo46

Ytse wrote:
Mon Aug 08, 2022 2:01 pm
C36 wrote:
Mon Aug 08, 2022 1:06 pm
Ytse wrote: 105% rule is not applicable, according to some wheel designers / manufacturers when rims are that deep (eg 50mm). You'll probably lose only 1-2 watts using 28mm tyres on a 25mm wide rims, meanwhile ride comfort will be night and day. If you are not chasing the last 1% to win a TT or crit, forget about 105%.
Few points
- the effect will be particularly visible on high yaw angles with more drag and stronger, more irregular, torque returns on the handlebar.
- the tire width and comfort… that’s not how physics work. A large tire inflated at the same pressure than a narrower tire will be way harder, a large tire with the pressure adjusted to its width will have the EXACT same confort level (same spring rate, same impedance losses). A wide tire will allow to go MUCH lower in pressures with less risk to snakebite it and that where you gain confort, a narrower tire could do it but with a risk to pinch.
Totally agree with your point about tyre width. I thought it is kind of obvious that someone chooses a wider tyre over a thinner one because of the ability to ride it on lower pressure leading to increased comfort.
Actually, as C36 points out if you set up a narrow tire and a wider tire for the same rolling resistance / same impedence losses, you'll get the same comfort level. But yes, a wider tire allows for lower pressures at the expense of higher rolling resistance.

And to echo C36... depending on your riding style, adhering to the 105% rule provides more safety when hit by cross winds during a fast descent.

ricerocket
Posts: 596
Joined: Mon Sep 27, 2010 8:38 am

by ricerocket

Hexsense wrote:
Mon Aug 08, 2022 9:20 pm
ricerocket wrote:
Mon Aug 08, 2022 2:23 pm
CampagYOLO wrote:
Mon Aug 08, 2022 10:17 am
Also those Hunt wheels are so old school with a 25mm outer width, best of luck finding tyres that comply with the 105% rule with those narrow rims. They clearly went super narrow to chase low weight.
Ha. I love how 25mm outer is "so old school" now. :)
It kinda is. Considering my wheels in 2015 is already 28mm wide.
7 years later when 23c tires are no longer common, and someone still release rim that is best pair with 23c tires.
I have 25s on my 25mm rims, there's a smooth transition to the rim and pair fine IMO.

I'd love to see data 105% vs 100% (or other widths), I bet its less watts than disc brakes vs rim, or aero gloves vs regular gloves, or some other silly minute amount.

Hexsense
Posts: 3270
Joined: Wed Dec 30, 2015 12:41 am
Location: USA

by Hexsense

ricerocket wrote:
Tue Aug 09, 2022 9:08 am
Hexsense wrote:
Mon Aug 08, 2022 9:20 pm
ricerocket wrote:
Mon Aug 08, 2022 2:23 pm
CampagYOLO wrote:
Mon Aug 08, 2022 10:17 am
Also those Hunt wheels are so old school with a 25mm outer width, best of luck finding tyres that comply with the 105% rule with those narrow rims. They clearly went super narrow to chase low weight.
Ha. I love how 25mm outer is "so old school" now. :)
It kinda is. Considering my wheels in 2015 is already 28mm wide.
7 years later when 23c tires are no longer common, and someone still release rim that is best pair with 23c tires.
I have 25s on my 25mm rims, there's a smooth transition to the rim and pair fine IMO.

I'd love to see data 105% vs 100% (or other widths), I bet its less watts than disc brakes vs rim, or aero gloves vs regular gloves, or some other silly minute amount.
This is the repost of content in 2014 or so that start it.
https://silca.cc/blogs/silca/part-5-tir ... rodynamics
Even the same tire that become different width because of different tire pressure can have noticeably different drag, if it happen to cross the tipping point.
This trend is observed on U shape rim where it is widest below brake track. Different rim shape where it's widest right at the brake track may tolerate 100% rather than 105, but we don't have data to make statement.

I've used 25c tire on 25mm rim before. It end up with 90-95% ratio since 25c measure well over 25mm when mounted. From those past experience, I stick with the 100-105% when possible. For 25mm wide rim, I'd use 23c tire. If I want 25mm tire but not having rim wide enough then I'd just sell old wheel and buy a new wider one if budget allow.

The biggest benefit I found when rim is wider than tire isn't about speed. It's the stability. 46mm rim and 56mm rim depth up front that follow 105% rule is noticebly more stable than 28mm and 32mm deep rim that has tire significantly wider than the rim.
Just think of how cross wind push the wheel at two different wheel positions. One where it leading the bike rotating down, and another time when wheel rotating up near the down tube.
Consider similarity vs difference between a shape that is widest at brake track or in the middle of the rim. Versus a shape that is widest at the tire, which is at the front most on down rotating part then at the back most on up rotating part. Then consider of how the force cancel out or adding up at the wheel mount. Then it isn't hard to see how a rim shape that is widest in the middle of the rim is more stable.

ricerocket
Posts: 596
Joined: Mon Sep 27, 2010 8:38 am

by ricerocket

Hexsense wrote:
Tue Aug 09, 2022 5:14 pm
This is the repost of content in 2014 or so that start it.
https://silca.cc/blogs/silca/part-5-tir ... rodynamics
Even the same tire that become different width because of different tire pressure can have noticeably different drag, if it happen to cross the tipping point.
This trend is observed on U shape rim where it is widest below brake track. Different rim shape where it's widest right at the brake track may tolerate 100% rather than 105, but we don't have data to make statement.

I've used 25c tire on 25mm rim before. It end up with 90-95% ratio since 25c measure well over 25mm when mounted. From those past experience, I stick with the 100-105% when possible. For 25mm wide rim, I'd use 23c tire. If I want 25mm tire but not having rim wide enough then I'd just sell old wheel and buy a new wider one if budget allow.

The biggest benefit I found when rim is wider than tire isn't about speed. It's the stability. 46mm rim and 56mm rim depth up front that follow 105% rule is noticebly more stable than 28mm and 32mm deep rim that has tire significantly wider than the rim.
Just think of how cross wind push the wheel at two different wheel positions. One where it leading the bike rotating down, and another time when wheel rotating up near the down tube.
Consider similarity vs difference between a shape that is widest at brake track or in the middle of the rim. Versus a shape that is widest at the tire, which is at the front most on down rotating part then at the back most on up rotating part. Then consider of how the force cancel out or adding up at the wheel mount. Then it isn't hard to see how a rim shape that is widest in the middle of the rim is more stable.
Thanks for digging up some data.

So converting the numbers from grams to watts...according to the test, at 0-20 degrees of yaw a 23 vs a 25c, your drag penalty will range from 10g to a peak of ~70g (at one measured angle), with the average being in the 20-30g range. Flo Cycling eqautes 50g of drag @ 30 mph to 6.5 watts, so your net penalty is 2.6-3.9 watts @ 30 mph.

I get marginal gains are gains, but I'm not tossing a $2k wheelset for at most 3 watts (less at the speeds I'm riding at).


I agree with you on rim profile and have felt the same, but that's tangential to this conversation, as my rims both blunt nosed and 25mm wide.

Ytse
Posts: 287
Joined: Thu May 05, 2022 11:53 am

by Ytse

Thanks for the interesting posts! 30 mph (~48 kmh) quoted in the Silca and Flo Cycling posts above is a speed achievable on downhills only (at least for me), and while it seems obvious to me that at higher speeds aero gains are more important, my experience tells me that wider tyres give much more confidence and make descending much more fun than being full aero. But again, I am not chasing marginal gains, just try to enjoy riding.
2020 Scott Addict RC / 2021 Trek Emonda SLR / 2023 Specialized Tarmac SL8

justkeepedaling
Posts: 1712
Joined: Thu Jan 03, 2008 6:14 am

by justkeepedaling

Ytse wrote:
Thu Aug 11, 2022 1:54 pm
Thanks for the interesting posts! 30 mph (~48 kmh) quoted in the Silca and Flo Cycling posts above is a speed achievable on downhills only (at least for me), and while it seems obvious to me that at higher speeds aero gains are more important, my experience tells me that wider tyres give much more confidence and make descending much more fun than being full aero. But again, I am not chasing marginal gains, just try to enjoy riding.
If you ride at 20 mph with a 10 mph headwind. That's the same thing

spdntrxi
Posts: 5791
Joined: Sat Jul 20, 2013 6:11 pm

by spdntrxi

justkeepedaling wrote:
Thu Aug 11, 2022 7:14 pm
Ytse wrote:
Thu Aug 11, 2022 1:54 pm
Thanks for the interesting posts! 30 mph (~48 kmh) quoted in the Silca and Flo Cycling posts above is a speed achievable on downhills only (at least for me), and while it seems obvious to me that at higher speeds aero gains are more important, my experience tells me that wider tyres give much more confidence and make descending much more fun than being full aero. But again, I am not chasing marginal gains, just try to enjoy riding.
If you ride at 20 mph with a 10 mph headwind. That's the same thing
do the maths

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