Weight Weenies

1800w sprinters, 1250w climbers, and .5 mile "hill climbs" ..this thread has a lot going for it!


At least there are some beautiful pictures and SD going above and beyond!

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Imaking20 wrote:.5 mile "hill climbs" :

It's Ohio.


As for 1250W obviously I can't sustain anything like that for more than a couple seconds, but in trying to ascertain flex, mashing hard is the best I'm going to do short of a four-point MTS load frame and my AR1 isn't going in one.

I'm old. Sorry.

I noticed. As much as I hate going uphill - the variety is nice!

Doing a few days down in Georgia soon with some good hill work. Looking forward to leaving the Tarmac at home

spud wrote:twinning,

I'd bet you are dealing with wheel flex. I do a big group ride, and one of the guys I know has direct mount brakes on his chainstays. When we are working a pace line at moderate load, say 300 watts (an educated guess), I can see the rim deflecting towards the pads during each pedal stroke.

I suspect the rim deflection comes from two places - axle deflection that occurs as chain tension rises during the downstroke, in conjunction with the rim twisting around the hub due to the torque reaction through the spokes. My guess is that you would do better with a wheel which has crossing spokes on both sides of the hub, as well as perhaps higher spoke tension than the Zipps typically have.

I think that direct mount brake bikes put a higher premium on wheel stiffness than conventional brake position. Anecdotal evidence suggest it, and if chain tension induced axle displacement is a contributing factor, the rim deflection is maximized at the chain stay position, and nearly minimized at the seat stay position.

I'm not doubting the wheels are flexing. This is why I am comparing this set up to my previous set up. I used to be able to run my brakes tighter than before using the same wheels without getting rub. Yes I know I am comparing a sram aero link rear brake to a direct mount dura ace brake but again I am saying that the brakes were closer together on the other frame with the exact same wheels and I would not get rub. If it were solely just the wheels then I wouldn't have a problem if I was running the brakes even wider than before right?

Something just doesn't add up. I don't know if you have ridden the bike yet but when and if you do, you might feel it. I am 205 and can put out just over 1700 max so maybe that is why I am getting these issues.



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You're getting issues because you're 205 lbs. Plain and simple. Your mass is much higher than most that ride bikes (no offense, most people that ride are just tiny) and, simply put, F=MA and stuff.

Lots of things could be contributing to the rubbing. Zipp rims are stiff, so when you are sprinting the rim is trying to deflect beneath the axle but it can't so it causes the whole rim to "rock." You'll have to pardon my explanation as I'm not an engineer, but it should make sense. This is common on most wide, deep wheels.

Also, there could be a brake compatibility issue. The 9010 brakes are meant for 28mm max width. When you are at the upper limit of width they require you to use their thinner pads. If you are using zipp or swissstop pads, they aren't thinner and may even be thicker then standard duraace pads. Your zipps are 26mm at the brake track so you are pushing the limit of the brake. I'm assuming you're using shimano levers, but if not, that would be part of the reason your lever pull is so long.

I should add that I have no experience with this frame, but the issue of wide aero wheels rubbing brakes is very common and when you add in funky aero brakes and non standard mounting locations you run into these problems.

Twinning,

to be more direct, I think all of your bikes flex under that kind of power. The reason you don't get as much brake rub on the old bike may not be down frame stiffness but rather to the location of the brakes. Running direct mount brakes on the chainstay means having to run a stiffer wheel to clear the pads. Otherwise you end up with a bad compromise in braking. this tendency has been noted on the Madone 7 for example.

For reference sake, I had to open the quick releases on my old Zipp 404 with 24 spokes in the back when I was sprinting. Can't even imagine how flexy the 20 spoke versions are. I noted big improvements in brake rub when I moved to a Enve 66 built on DT. It's not a notably stiff wheel according to testing, but the fact that it has crossing spokes on both sides contributed to its stability and lack of brake rub.

All that said, I have not ridden an AR frame.

spud wrote:Twinning,

to be more direct, I think all of your bikes flex under that kind of power. The reason you don't get as much brake rub on the old bike may not be down frame stiffness but rather to the location of the brakes. Running direct mount brakes on the chainstay means having to run a stiffer wheel to clear the pads. Otherwise you end up with a bad compromise in braking. this tendency has been noted on the Madone 7 for example.

For reference sake, I had to open the quick releases on my old Zipp 404 with 24 spokes in the back when I was sprinting. Can't even imagine how flexy the 20 spoke versions are. I noted big improvements in brake rub when I moved to a Enve 66 built on DT. It's not a notably stiff wheel according to testing, but the fact that it has crossing spokes on both sides contributed to its stability and lack of brake rub.

All that said, I have not ridden an AR frame.

Guess I should just stick to the track then huh?


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Guess I should just stick to the track then huh?

No, too many other places where that kind of sprint is useful. Maybe try a 28 spoke wheel with at least 2x on both sides.

A sprint is only useful if you can get to the end of the race fresh. But we digress.

Sounds like a wheel problem. I found my Zipp 404 and 808 Firecrests to be sorta flexy and I weigh 160-170 depending on time of year.

^Yes, not to go off topic, but the wheel section of the forum, we have discussed this ad-naseum. The reason of flex on the older Zipps was the radial DS lacing and sad 188 hub.

The new v9 188 hubs solves this issue along with basically 2x both sides, plus the cross of the spokes right at the hub it does.

So, flex will still exist, with basically most wheels, but they have resolved that likely or the most part.

mitchgixer6 wrote:Twinning. Your post worries me on so many levels! Let's hope that one day you don't need to emergency brake to avoid a cat/dog/person/car/truck.

Here is how we calculated some of the stiffness numbers. For example, for torsional stiffness:

Torsional Stiffness Test:
The bike is mounted horizontally and fixed at the rear axle. The head tube is supported in the middle by a cylinder providing a pivot point.
A 1 inch steel bar is inserted into the head tube. The weight (10 kg) is hung 500 mm from the center of the head tube and the deflection is measured 500 mm from the center of the head tube opposite the weight.
The angle of the bar is calculated using the following equation:
θ - tan-1 (δ/500) 180/π
θ = Angle of bar (degrees)
δ = Measured deflection (mm)
The stiffness is expressed in units of N-m/deg and is found by using the equation:
S = 4.91Nm/θ

Some of the numbers of other aero bikes we've tested:
Model
2. Felt AR FRD
3. Scott Foil
4. Specialized Venge
5. Giant Propel
6. Cervelo S5
Size
2. 56
3. 56
4. 56
5. M
6. 56
Weight (g)
2. 912
3. 1020
4. 1022
5. 1181
6. 1324
Stiffness
(Nm/deg)
2. 140
3. 141.6
4. 102.1
5. 127.7
6. 104.0
Stiffness:
Weight
2. 154.0
3. 138.8
4. 99.9
5. 108.1
6. 78.6

These numbers have an absolute and relative (STW) value that are compared to other bicycles we've tested during development of bikes like the F-series and the new F FRD. This is why I claim that the AR FRD is as stiff as most road bikes (not just aero road bikes - all) from an absolute stiffness as well as a STW standpoint.

We also measure vertical compliance measured in y-axis deflection at the saddle rail clamp and dozens of other tests such as one-stay, two-stay, fore-aft, fork deflection, BB, HT, etc...

I don't ride the bike up a hill at 1250w, then coast down and grab another brand and do the same and provide my impressions of stiffness.

-Dave

SuperDave wrote:

mitchgixer6 wrote:Twinning. Your post worries me on so many levels! Let's hope that one day you don't need to emergency brake to avoid a cat/dog/person/car/truck.

Here is how we calculated some of the stiffness numbers. For example, for torsional stiffness:

Torsional Stiffness Test:
The bike is mounted horizontally and fixed at the rear axle. The head tube is supported in the middle by a cylinder providing a pivot point.
A 1 inch steel bar is inserted into the head tube. The weight (10 kg) is hung 500 mm from the center of the head tube and the deflection is measured 500 mm from the center of the head tube opposite the weight.
The angle of the bar is calculated using the following equation:
θ - tan-1 (δ/500) 180/π
θ = Angle of bar (degrees)
δ = Measured deflection (mm)
The stiffness is expressed in units of N-m/deg and is found by using the equation:
S = 4.91Nm/θ

Some of the numbers of other aero bikes we've tested:
Model
2. Felt AR FRD
3. Scott Foil
4. Specialized Venge
5. Giant Propel
6. Cervelo S5
Size
2. 56
3. 56
4. 56
5. M
6. 56
Weight (g)
2. 912
3. 1020
4. 1022
5. 1181
6. 1324
Stiffness
(Nm/deg)
2. 140
3. 141.6
4. 102.1
5. 127.7
6. 104.0
Stiffness:
Weight
2. 154.0
3. 138.8
4. 99.9
5. 108.1
6. 78.6

These numbers have an absolute and relative (STW) value that are compared to other bicycles we've tested during development of bikes like the F-series and the new F FRD. This is why I claim that the AR FRD is as stiff as most road bikes (not just aero road bikes - all) from an absolute stiffness as well as a STW standpoint.

We also measure vertical compliance measured in y-axis deflection at the saddle rail clamp and dozens of other tests such as one-stay, two-stay, fore-aft, fork deflection, BB, HT, etc...

I don't ride the bike up a hill at 1250w, then coast down and grab another brand and do the same and provide my impressions of stiffness.

-Dave

How does the ar1 compare? The ar frd is only compared to the old ar1.


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Great Prices ✓    Broad Selection ✓    Worldwide Delivery ✓

www.starbike.com

SuperDave wrote:

mitchgixer6 wrote:Twinning. Your post worries me on so many levels! Let's hope that one day you don't need to emergency brake to avoid a cat/dog/person/car/truck.

Here is how we calculated some of the stiffness numbers. For example, for torsional stiffness:

Torsional Stiffness Test:
The bike is mounted horizontally and fixed at the rear axle. The head tube is supported in the middle by a cylinder providing a pivot point.
A 1 inch steel bar is inserted into the head tube. The weight (10 kg) is hung 500 mm from the center of the head tube and the deflection is measured 500 mm from the center of the head tube opposite the weight.
The angle of the bar is calculated using the following equation:
θ - tan-1 (δ/500) 180/π
θ = Angle of bar (degrees)
δ = Measured deflection (mm)
The stiffness is expressed in units of N-m/deg and is found by using the equation:
S = 4.91Nm/θ

Some of the numbers of other aero bikes we've tested:
Model
2. Felt AR FRD
3. Scott Foil
4. Specialized Venge
5. Giant Propel
6. Cervelo S5
Size
2. 56
3. 56
4. 56
5. M
6. 56
Weight (g)
2. 912
3. 1020
4. 1022
5. 1181
6. 1324
Stiffness
(Nm/deg)
2. 140
3. 141.6
4. 102.1
5. 127.7
6. 104.0
Stiffness:
Weight
2. 154.0
3. 138.8
4. 99.9
5. 108.1
6. 78.6

These numbers have an absolute and relative (STW) value that are compared to other bicycles we've tested during development of bikes like the F-series and the new F FRD. This is why I claim that the AR FRD is as stiff as most road bikes (not just aero road bikes - all) from an absolute stiffness as well as a STW standpoint.

We also measure vertical compliance measured in y-axis deflection at the saddle rail clamp and dozens of other tests such as one-stay, two-stay, fore-aft, fork deflection, BB, HT, etc...

I don't ride the bike up a hill at 1250w, then coast down and grab another brand and do the same and provide my impressions of stiffness.

-Dave

How does the ar1 compare? The ar frd is only compared to the old ar1.


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