1.4 mile (2.2km) Hill Climb @9.2% - which wheels?

Discuss light weight issues concerning road bikes & parts.
zcfbg06
Posts: 5
Joined: Mon Feb 01, 2016 12:29 pm

by zcfbg06

I have a hill climb of 1.5 miles at 9.2% av gradient. I have previously averaged 11.8 mph and hope for around 12mph next time. The final 0.4 miles (600m) average 12.5% but the first mile is more like 8%. Which wheelset/s would you recommend? Last time I used enve 4.5 tubs: great aero-to-weight ratio, but at 1312g for the pair they are more of an aero/all-round race wheel. For the first mile at 8% I'm sure I'd benefit from a little depth to the wheels... 30-38mm type of thing... but for the top section I'm confident ultra-light ultra-shallow rims are the best. For the quickest time overall I'm unsure. I feel at 12mph I'm just on the cusp of getting any noticeable aero gain. Should I just go ultra-lightweight? Should I go for something with rim depth in the 30's? I'm really fishing for a reason to buy some sub-1000g tubs!! Please ask if you need more details. Thanks!

by Weenie


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ergott
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by ergott

The race is too short for any significant time gains, but go with the lightest you can get your hands on. Obviously they shouldn't be noodly.

Marin
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Location: Vienna Austria

by Marin

At low yaw, low profile wheels with narrow tires have very good aero, so unless there are crosswinds you don't need tall rims.

Rolling resistance will be better with fast clinchers. Plug the numbers into Kreuzotter to get a feel for what the gains could be: http://kreuzotter.de/english/espeed.htm

I'd ride my 1280g 25x25mm set with 24mm Turbo Cottons / Latex and be confident that I'm not losing much if anything to ppl on sub-1kg tubs, but I'm not doing the race and didn't do the math ;)

zcfbg06
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Joined: Mon Feb 01, 2016 12:29 pm

by zcfbg06

Yes, I too am a big believer in the clincher Crr benefits. I don't think you lose much using the corsa speed tubs (or even track tubs!!) though, but I also favour tubs as the climb has around 20 hairpins where you have to accelerate out of... which in my head makes weight savings on the rim a little more valuable than they'd normally be on a straighter climb. I'd imagine yaw will be low: not a windy area - plus the constant hairpins and sinuous route mean wind effects are largely negated. Ergott is right though: in such a short race (6 mins 40 - 7 mins) there's very little to be gained.

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kgt
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Location: Athens, Greece

by kgt

@ zcfbg06
ΙΜΗΟ you should better try to be as calm as possible before and during the race and worry less about your wheelset's profile. Good psychology is all the boost you need...

zcfbg06
Posts: 5
Joined: Mon Feb 01, 2016 12:29 pm

by zcfbg06

Agree with the focus on psychology. I can stay calm before and during, but I always feels there's plenty of room regarding pain threshold and going real, real deep. Equipment on the levels we're talking are icing on the cake... but I want the icing too!

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kgt
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Location: Athens, Greece

by kgt

As ergott said the race is too short in order for a wheelset to offer you actual gains. Even if you do the math calculating gradients, weights, crr, Cd etc. etc. nobody can guarantee that reality will confirm theory.

MXGimp
Posts: 21
Joined: Wed Feb 15, 2017 7:26 pm

by MXGimp

Marin wrote:At low yaw, low profile wheels with narrow tires have very good aero, so unless there are crosswinds you don't need tall rims.

Rolling resistance will be better with fast clinchers. Plug the numbers into Kreuzotter to get a feel for what the gains could be: http://kreuzotter.de/english/espeed.htm

I'd ride my 1280g 25x25mm set with 24mm Turbo Cottons / Latex and be confident that I'm not losing much if anything to ppl on sub-1kg tubs, but I'm not doing the race and didn't do the math ;)


Thanks for this link! So cool.

Marin
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Joined: Wed Jan 22, 2014 11:48 am
Location: Vienna Austria

by Marin

kgt wrote:Even if you do the math calculating gradients, weights, crr, Cd etc. etc. nobody can guarantee that reality will confirm theory.


Not a big believer in science?

GothicCastle
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Joined: Mon Jul 04, 2016 1:52 am

by GothicCastle

You think you need a special wheelset for a five-minute climb?

Wookski
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Joined: Tue Feb 23, 2016 5:51 am

by Wookski

Ax Ultra 25T with ceramic upgrade (mine tip the scales at 780g). Veloflex record tubs.
Surprisingly stiff and after one ride you won't want to climb with anything else!


sp3000
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Joined: Thu Aug 21, 2014 7:12 am
Location: Sydney

by sp3000

I think stiffness should be a big priority here, once going I I don't think ultra ultra light will help unless they are ultra ultra stiff. If money were no object Lightweight Milensteins would be a very good choice. Also DT Swiss Mon Chasseral RC28's would be very good, you can run tubeless, not super wide, 23mm tyres work very well and they are an aero profile so no brick but they are very very stiff and the hub engagement is excellent. They are stiffer than my Ax lightness Ultra 45C's and the extralite hub engagement is slow. If you need to make bursts of power the LIghtweights or the DT Swiss at 1250g tubeless are good options.

Wookski
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Joined: Tue Feb 23, 2016 5:51 am

by Wookski

sp3000 wrote:I think stiffness should be a big priority here, once going I I don't think ultra ultra light will help unless they are ultra ultra stiff. If money were no object Lightweight Milensteins would be a very good choice. Also DT Swiss Mon Chasseral RC28's would be very good, you can run tubeless, not super wide, 23mm tyres work very well and they are an aero profile so no brick but they are very very stiff and the hub engagement is excellent. They are stiffer than my Ax lightness Ultra 45C's and the extralite hub engagement is slow. If you need to make bursts of power the LIghtweights or the DT Swiss at 1250g tubeless are good options.

I have LW obermeyers and although great wheels the AX's are much better for climbing (no issues with perceived flex either- although at 64kg I'm hardly a watt monster). I can't believe people are recommending wheels over 1kg for a hill climb :noidea:

by Weenie


TheKaiser
Posts: 516
Joined: Thu Sep 05, 2013 3:29 pm

by TheKaiser

zcfbg06 wrote:I also favour tubs as the climb has around 20 hairpins where you have to accelerate out of... which in my head makes weight savings on the rim a little more valuable than they'd normally be on a straighter climb.


If the lighter weight of your tub setup gives you a mental benefit, then certainly use it. The whole "rotational weight counts 3x vs static weight" thing is not as true as originally believed though. The greater acceleration of the light setup (during the power phases of each pedal stroke and during periods of higher total output) will generally be offset by the greater speed losses of the lighter setup (during lower power phases and outputs) due to a reduced flywheel effect. If you are going to be braking going into these 20 hairpins then, yes, use the lighter setup, because you will be burning off your hard earned angular momentum in the braking event, but if there is no braking involved then their should be no losses from the heavier wheels, other than the standard increase in energy required to move the weight to a higher elevation, the same as for the rest of the bike.

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