How deep is too deep? Weight vs aero

[e4rthm0ver]

I need some wheel advice!
For the last 2 years I’ve been riding my pretty racy Specialized Roubaix with 38mm deep Carbon wheels built by local builder with some rims 21mm internal width with dt350 hubs and sapim spokes. Wheels weight ~1475g.

I’m 70-72kg and ride mostly rolling hills and short punchy climbs (south of Poland). My typical rides are 100-200m of elevation per 10km depending on how much climbing I want for a day For example on my usual 70km loop I do 850m of elevation with avg speed of ~31km/h.
There are some windy days here but nothing crazy, I’ve never felt unsafe on my current Chinese 38s, I ride solo and never let go more than one hand from the bars to have a drink.

Now for the summer I’m thinking of going deeper and more aero for looks and some extra speed. I’m pretty much set on DT Swiss ARC 1100 Dicut set but not sure about how deep to go with rims.

50mm front and rear seems like safe choice, weight is pretty much the same as my current set but deeper and more aero

50mm front + 62mm back is ~100g heavier, a bit more aero than pair of 50s and looks good

Pair of 62s is additional ~100g heavier (200g in total) but should be faster

Last setup that I’m considering is pretty crazy one but looks cool as hell: 62mm front + 80mm back (42g heavier than pair of 62s, ~240g heavier than my current 38mm set)

I’m kind of between 50+62 and 62+80 as I like the look of deeper rear wheel but I’m wondering how much that 140g matters between those two setups for my type of riding? Would aero gains offset some extra weight?

I’m running GP5000str 25C tubeless and intend to keep doing so with new wheels

Current bike pic:

[alanyu]

62 mm vs 50 mm is usually 2~3 Watts faster, and let's say 2.5. However, the front wheel contributes 70% or so based on cervelo's wind tunnel study. Then, 50+62 vs 50+50 is only 0.8 Watts faster. 31 kph @ 70 km loop w/ 850 m elevation, so assume your power is around 4.0 Watts/kg? That would result at roughly a critical grade of 2.1% where weight is equal to aero under then condition of 0.8 Watts vs 100g, without considering the wind.
The same rough calculation resulted in 2.9% and 3.2% for 62+62 vs 50+50 and 62+68 vs 50+50.

[e4rthm0ver]

62 mm vs 50 mm is usually 2~3 Watts faster, and let's say 2.5. However, the front wheel contributes 70% or so based on cervelo's wind tunnel study. Then, 50+62 vs 50+50 is only 0.8 Watts faster. 31 kph @ 70 km loop w/ 850 m elevation, so assume your power is around 4.0 Watts/kg? That would result at roughly a critical grade of 2.1% where weight is equal to aero under then condition of 0.8 Watts vs 100g, without considering the wind.
The same rough calculation resulted in 2.9% and 3.2% for 62+62 vs 50+50 and 62+68 vs 50+50.

So basically going as deep as possible (62+80) should still be the fastest setup overall (except on very steep gradient) despite being 200 something grams heavier?

[Singular]

Yes. If moving in the line of one brand/manufacturer (where depth and weight are the only factors), it is almost impossible to "outweight" oneself except for very, very specific events and situations. Deeper is faster, practically always. The faster you are, the more difference it makes. The only downside to a really deep wheel is control - that one is not capable and confident to ride them in strong(er) winds. Rim depth is also a case of pretty rapidly decreasing gains - there is a huge diffence from the usual punching bags in these tests (Ksyriums and Open Pro's) to a 38/40ish mm profile, but then it is not as apparent.

With that said, a shallow/light wheel FEELS great. And feeling counts for a lot when racing.

[alanyu]

62 mm vs 50 mm is usually 2~3 Watts faster, and let's say 2.5. However, the front wheel contributes 70% or so based on cervelo's wind tunnel study. Then, 50+62 vs 50+50 is only 0.8 Watts faster. 31 kph @ 70 km loop w/ 850 m elevation, so assume your power is around 4.0 Watts/kg? That would result at roughly a critical grade of 2.1% where weight is equal to aero under then condition of 0.8 Watts vs 100g, without considering the wind.
The same rough calculation resulted in 2.9% and 3.2% for 62+62 vs 50+50 and 62+68 vs 50+50.

So basically going as deep as possible (62+80) should still be the fastest setup overall (except on very steep gradient) despite being 200 something grams heavier?

Yes, that's the theory and you should note that's based on an ideal situation.

The reality is: 1, it's a loop, so the climbing part is at least twice as steep as 0.85/70, and one usually doesn't go full power pedalling or not pedalling during descent. 2, during a climbimg steeper than the critical grade, with deeper profile wheels, one spends more time = consuming more stamina, but during the desending, one spends less time = regenerating less. 3, crosswind, that depends on how much you will be impacted on deeper wheels.

Thus, you may give a bit deduction on the critical grade.

BTW, I wouldn't call 3.2% as steep. In Switzerland most climbings are > 6%

[Nickldn]

I would say that deeper wheels, say over 50mm, feel less nimble, especially on technical sections. This is why 60-80mm are usually used for TT and not general road riding.

But yes, undoubtedly deeper wheels are faster.

I think you should aim to strike a balance between wheel depth and the promise of a bit more additional speed (which doesn't matter if you're not racing), as very deep wheels can compromise your riding pleasure.

[e4rthm0ver]

Update: I got really good deal on top of the line DT wheelset from endurance series that I didn’t considered initially and decided to pull the trigger.

ERC 1100 Dicut 45mm with dt180 hubs, ceramic bearings, hidden nipples and all cool stuff. Wheels are deeper, lighter and stiffer than my previous set so there is an improvement in every aspect Really stable in crosswind gusts too, I would say more stable than my old 38mm

[pmprego]

62 mm vs 50 mm is usually 2~3 Watts faster, and let's say 2.5. However, the front wheel contributes 70% or so based on cervelo's wind tunnel study. Then, 50+62 vs 50+50 is only 0.8 Watts faster. 31 kph @ 70 km loop w/ 850 m elevation, so assume your power is around 4.0 Watts/kg? That would result at roughly a critical grade of 2.1% where weight is equal to aero under then condition of 0.8 Watts vs 100g, without considering the wind.
The same rough calculation resulted in 2.9% and 3.2% for 62+62 vs 50+50 and 62+68 vs 50+50.

So basically going as deep as possible (62+80) should still be the fastest setup overall (except on very steep gradient) despite being 200 something grams heavier?

Yes, that's the theory and you should note that's based on an ideal situation.

The reality is: 1, it's a loop, so the climbing part is at least twice as steep as 0.85/70, and one usually doesn't go full power pedalling or not pedalling during descent. 2, during a climbimg steeper than the critical grade, with deeper profile wheels, one spends more time = consuming more stamina, but during the desending, one spends less time = regenerating less. 3, crosswind, that depends on how much you will be impacted on deeper wheels.

Thus, you may give a bit deduction on the critical grade.

BTW, I wouldn't call 3.2% as steep. In Switzerland most climbings are > 6%

The thread was basically closed as the OP bought some wheels. Nonetheless... for the sake of discussion... that reasoning is all nice and pretty but I keep getting dropped on the climbs. Thus, this "deeper is faster" is really context-dependent. It seems to me that if I'm the weaker guy in the climbs, lighter is faster as I'll be able to keep with the group and draft the wheels on the flatter part (even if I have to pull from time to time).

That said... in race days, I use 40mm wheels but really dig the look of a rear deepish wheel. On a flatter day, for the future, I consider going 40front and something like 50-60rear. But mostly for looks

[alanyu]

62 mm vs 50 mm is usually 2~3 Watts faster, and let's say 2.5. However, the front wheel contributes 70% or so based on cervelo's wind tunnel study. Then, 50+62 vs 50+50 is only 0.8 Watts faster. 31 kph @ 70 km loop w/ 850 m elevation, so assume your power is around 4.0 Watts/kg? That would result at roughly a critical grade of 2.1% where weight is equal to aero under then condition of 0.8 Watts vs 100g, without considering the wind.
The same rough calculation resulted in 2.9% and 3.2% for 62+62 vs 50+50 and 62+68 vs 50+50.

So basically going as deep as possible (62+80) should still be the fastest setup overall (except on very steep gradient) despite being 200 something grams heavier?

Yes, that's the theory and you should note that's based on an ideal situation.

The reality is: 1, it's a loop, so the climbing part is at least twice as steep as 0.85/70, and one usually doesn't go full power pedalling or not pedalling during descent. 2, during a climbimg steeper than the critical grade, with deeper profile wheels, one spends more time = consuming more stamina, but during the desending, one spends less time = regenerating less. 3, crosswind, that depends on how much you will be impacted on deeper wheels.

Thus, you may give a bit deduction on the critical grade.

BTW, I wouldn't call 3.2% as steep. In Switzerland most climbings are > 6%

The thread was basically closed as the OP bought some wheels. Nonetheless... for the sake of discussion... that reasoning is all nice and pretty but I keep getting dropped on the climbs. Thus, this "deeper is faster" is really context-dependent. It seems to me that if I'm the weaker guy in the climbs, lighter is faster as I'll be able to keep with the group and draft the wheels on the flatter part (even if I have to pull from time to time).

That said... in race days, I use 40mm wheels but really dig the look of a rear deepish wheel. On a flatter day, for the future, I consider going 40front and something like 50-60rear. But mostly for looks

True, on a climb weight will catch aero earlier for a weaker guy. Take myself as an example, I was happy with 56 mm wheels last spring and summer when I was in good shape around 4.1 W/kg. However, I have a ton of projects to do and some requires a continuous 24 hrs since the autumn, much less time for training and weekend rides. Now my ftp is only 3.4 W/kg, and I had to order a pair of light wheels