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istepinyards
Wrecked
Joined: Feb 13, 2007
Posts: 6,118
Location: Rooting for the SunDevils
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 Posted: Sat 5/Jul/08 2:49pm Post subject: |
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| inzane wrote: | | danose wrote: | | istepinyards wrote: | Thats why I used to smash Danose down Dyres  |
ahh, the old stepinyards smashing sessions, them's were the days  |
nah... you were going faster cos Danose was using his brakes a lot too! |
And to think I thought that smell was his farts. 
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danose
Mangled
Joined: May 27, 2004
Posts: 10,986
Location: Nose City
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| Posted: Sat 5/Jul/08 3:01pm Post subject: |
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| inzane wrote: | | danose wrote: | | istepinyards wrote: | | Thats why I used to smash Danose down Dyres |
ahh, the old stepinyards smashing sessions, them's were the days |
nah... you were going faster cos Danose was using his brakes a lot too! |
oi!I may be a complete nana on the dirt, but on the road I can descend with the best - if you don't believe me go try holding 70km/h down from gibraltar to gebbies Though I don't recommend trying today 
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danose
Mangled
Joined: May 27, 2004
Posts: 10,986
Location: Nose City
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| Posted: Sat 5/Jul/08 3:03pm Post subject: |
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| istepinyards wrote: | | inzane wrote: | | danose wrote: | | istepinyards wrote: | | Thats why I used to smash Danose down Dyres |
ahh, the old stepinyards smashing sessions, them's were the days |
nah... you were going faster cos Danose was using his brakes a lot too! |
And to think I thought that smell was his farts. |
stop giving away my secrets! The surreptitious stink bomb is the ultimate weapon of paceline destruction! 
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jeremyb
BRAP BRAP BRAP BRAP
Joined: Jan 12, 2003
Posts: 32,882
Location: Derailled
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| Posted: Sat 5/Jul/08 3:07pm Post subject: |
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| inzane wrote: | I was just saying that in a real world racing situation you are constantly changing velocity, which means you will have to be constantly accelerating that extra weight (expending extra energy). If you were going for the hour record, where you get the bike up to speed on a closed track and then hold that speed... then a heavy and very aerodynamic wheel will be an advantage. Even a long flat time trial stage a heavy wheel might not make much difference... but a road race where having a good race depends on you being able to accelerate quickly and many times during the race... well a light wheel would be my only choice! 
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A lighter wheel will not always accelerate faster, its about weight distribution as well, moments of inertia, if you're obsessed with the whole idea of acceleration being the be all end all then you need to look for a light rim with low spoke count and nipples at the hub, plus the lightest tyre and tube combo you can find, but to finish first you must first finish, even the Tour riders are often riding heavy gear
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inzane
Wrecked
Joined: Feb 23, 2005
Posts: 6,642
Location: churchur
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| Posted: Sat 5/Jul/08 3:16pm Post subject: |
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| jeremyb wrote: | | inzane wrote: | I was just saying that in a real world racing situation you are constantly changing velocity, which means you will have to be constantly accelerating that extra weight (expending extra energy). If you were going for the hour record, where you get the bike up to speed on a closed track and then hold that speed... then a heavy and very aerodynamic wheel will be an advantage. Even a long flat time trial stage a heavy wheel might not make much difference... but a road race where having a good race depends on you being able to accelerate quickly and many times during the race... well a light wheel would be my only choice!
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A lighter wheel will not always accelerate faster, its about weight distribution as well, moments of inertia, if you're obsessed with the whole idea of acceleration being the be all end all then you need to look for a light rim with low spoke count and nipples at the hub, plus the lightest tyre and tube combo you can find, but to finish first you must first finish, even the Tour riders are often riding heavy gear |
Yes... I know all of that too... I did physics to second year at uni 
I will take that statement above as being in agreement with me 
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Tristan
Scuffed
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Joined: Apr 15, 2003
Posts: 447
Location: Building wheels
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| Posted: Sat 5/Jul/08 5:08pm Post subject: |
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| jeremyb wrote: |
A lighter wheel will not always accelerate faster, its about weight distribution as well, moments of inertia, if you're obsessed with the whole idea of acceleration being the be all end all then you need to look for a light rim with low spoke count and nipples at the hub, plus the lightest tyre and tube combo you can find, but to finish first you must first finish, even the Tour riders are often riding heavy gear |
Nipples at the hub save less than 1% on a most wheel's MoI compared to traditional alloy nipples at the rim, but this depends on how the spoke is attached to the rim...for example the Shimano wheels use a heavy steel spoke head and steel washer at the rim which increases the wheels MoI (counter productive)
Unfortunately light rim + low spoke count = parc wheel to ride. A deeper, stiffer rim with a lower spoke count usually results in a *lower* MoI for comparable lateral stiffness to a higher-spoked traditional rim.
Tyres, tubes and rim tape make a big difference of course! Just please don't run wafer-thin tyres because the weight savings is countered by the extra spare tubes you need to carry
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Oli
Mangled
Joined: Aug 03, 2005
Posts: 32,945
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| Posted: Sat 5/Jul/08 5:20pm Post subject: |
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Joel
Wrecked
Joined: Mar 26, 2002
Posts: 6,112
Location: Welly
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| Posted: Sat 5/Jul/08 5:24pm Post subject: |
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Latex tubes with pro race 2/3 tires FTW
that wheel builder mentioned in the post your roadie thread must walk on water or something for something to be considered than better than your two 
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specializedman
Worn
Joined: Jan 13, 2008
Posts: 799
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| Posted: Sun 6/Jul/08 4:38pm Post subject: |
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Im a junior rider and own a 06 Avant Giro which is lovely and comes standard with shimano R500's which are bullet proof.
I wanted to get into racing more so i bought a set of Easton Ea90tt's which are way lighter than the R500's and way more Aero. For me as a junior I use 25-17 cassete on my training wheels and 23-17 on the race wheels for close ratios. Also on my training wheels i use specialized all condition tires for extreme puncture resistance and peace of mind.
As for less spokes being flexy... I have only heard things about mavic Ksyriums being all floppy and useless unless you are 60kg and not strong. my eastons are 16 spoke front and 20 rear and are perfectly stiff for me.
Its all in the spoke tension!
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Tristan
Scuffed
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Joined: Apr 15, 2003
Posts: 447
Location: Building wheels
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| Posted: Sun 6/Jul/08 4:56pm Post subject: |
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| specializedman wrote: |
Its all in the spoke tension! |
I'm sure your Easton wheels are great, however spoke tension has nothing to do with how stiff a wheel is. Only when the spokes go slack to they lead to any measurable decrease in lateral tension.
Generally wheel stiffness is a result of the rim's stiffness, the number and type of spoke, and the flange dimensions of the hub.
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istepinyards
Wrecked
Joined: Feb 13, 2007
Posts: 6,118
Location: Rooting for the SunDevils
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| Posted: Sun 6/Jul/08 4:59pm Post subject: |
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| Tristan wrote: | | specializedman wrote: |
Its all in the spoke tension! |
I'm sure your Easton wheels are great, however spoke tension has nothing to do with how stiff a wheel is. Only when the spokes go slack to they lead to any measurable decrease in lateral tension.
Generally wheel stiffness is a result of the rim's stiffness, the number and type of spoke, and the flange dimensions of the hub. |
hehehe Tristan said flange 
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musket
Mangled
Joined: Sep 28, 2002
Posts: 8,847
Location: Transient
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| Posted: Sun 6/Jul/08 5:00pm Post subject: |
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| Tristan wrote: | | specializedman wrote: |
Its all in the spoke tension! |
I'm sure your Easton wheels are great, however spoke tension has nothing to do with how stiff a wheel is. Only when the spokes go slack to they lead to any measurable decrease in lateral tension.
Generally wheel stiffness is a result of the rim's stiffness, the number and type of spoke, and the flange dimensions of the hub. |
Laterally, or radially?
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Tristan
Scuffed
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Joined: Apr 15, 2003
Posts: 447
Location: Building wheels
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| Posted: Sun 6/Jul/08 5:36pm Post subject: |
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| musket wrote: | | Tristan wrote: | | specializedman wrote: |
Its all in the spoke tension! |
I'm sure your Easton wheels are great, however spoke tension has nothing to do with how stiff a wheel is. Only when the spokes go slack to they lead to any measurable decrease in lateral tension.
Generally wheel stiffness is a result of the rim's stiffness, the number and type of spoke, and the flange dimensions of the hub. |
Laterally, or radially? |
I've only tested in relation to lateral stiffness. Assuming we're talking about a single wheel (not a comparison) the wheel stiffness is a result of some of the spokes elongating because of the applied load. If the rim is not able to move laterally more / less because of spoke tension then I can't see that vertical / radial stiffness would be affected either, however I've never tested this.
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musket
Mangled
Joined: Sep 28, 2002
Posts: 8,847
Location: Transient
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| Posted: Sun 6/Jul/08 5:42pm Post subject: |
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It seems (I've no test data) rims could be stiff (or flexy) in one axis, but not another...
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Tristan
Scuffed
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Joined: Apr 15, 2003
Posts: 447
Location: Building wheels
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| Posted: Sun 6/Jul/08 6:05pm Post subject: |
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| musket wrote: | | It seems (I've no test data) rims could be stiff (or flexy) in one axis, but not another... |
Definitely...the rim itself will be stiffer in one axis compared to another. But if a change in spoke tension doesn't affect how stiff the rim / wheel is in one direction then it shouldn't affect the rim in another direction.
It's also worth mentioning that a meager load of 10kg applied laterally will result in a couple of millimeters of deflection, whereas 100kg of load applied radially will apparently* only result in 0.16mm of deflection...pretty much insignificant compared to how much the tyre will deform. 
*http://www.astounding.org.uk/ian/wheel/patterns.html
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