jaretj wrote:
I'm only at 8 bikes :(:-( indeed
TriDork
"Happiness is a myth. All you can hope for is to get laid once in a while, drunk once in a while and to eat chocolate every day"
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Re: Who are these people that think everyone should be on 700C wheels? [jaretj]
[ In reply to ]
:-( indeed
TriDork
"Happiness is a myth. All you can hope for is to get laid once in a while, drunk once in a while and to eat chocolate every day"
Re: Who are these people that think everyone should be on 700C wheels? [AutomaticJack]
[ In reply to ]
AutomaticJack wrote:
Travis R wrote:
What is a GCE?Gross Conceptual Error. It is a common military term, along with RTFQ-ATFQ -> Read The F**king Question-Answer The F**king Question.
Wheel Weight and its affect on performance has been discussed on ST for years. There is a core group that explains over and over to people that the construction of a bike wheel does not lend itself well to a flywheel. Most of the mass is in the hub, rim, and tire/tube. A 650 is moving the weight that is off center (the weight that affects rotation effort) closer to the center and that helps, that is true, but there just isn't enough movement or weight change to have a measureable performance effect.
Could you notice spin up effort from 0 to 20 mph? Maybe, even probably, but does anyone in our sport actually accelerate hard from 0 to 20 mph? Even a crit racer only routinely accelerates from low 20's to high 20's, and at that speed and momentary effort it just doesn't matter.
The person writing the article states that a lighter wheel is always faster as though its a lot faster and a selling point. It isn't in either case. If it was everyone on ST would be looking for 650 wheels
Ummm...no.
http://bikeblather.blogspot.com/
Re: Who are these people that think everyone should be on 700C wheels? [trail]
[ In reply to ]
trail wrote:
AutomaticJack wrote:
but there just isn't enough movement or weight change to have a measureable performance effect. Could you notice spin up effort from 0 to 20 mph?
I ran some ballpark #'s in the Criterium Jump Calculator. I made everything equal except wheel radius and dropped rotational inertia by 30% (I pulled 30% completely out of ass)
Then doing a 30-second jump from a standing start, max power 500W, average power 350W.
The "650" ended up ahead by 0.02 seconds and 18cm. So that's hugely significant for a criterium rider - sprints are sometimes won by less than 18cm. So the your answer is you may not be able to "notice" the spin up effort, but it'd have a very real effect. (Unless my 30% is way, way off)
Also my model had the same Crr for both wheels, which may narrow that 18cm by some cm. I could re-run it once I have time to sort out plausible sets of numbers across the board.
The 650 is also more aero - less frontal area. But whether that makes the whole bike-rider-wheel system more aero, I have no idea.
30% rotational inertia drop is a ridiculous assumption...and NO crit sprints are contested from a standing start.
http://bikeblather.blogspot.com/
Re: Who are these people that think everyone should be on 700C wheels? [Tom A.]
[ In reply to ]
Quick math in my head... about a 3.5% crr penalty? I'm not sure how to assess any aero benefits from a smaller wheel but... going on feel... I'm guessing a 1-2 watt penalty for something like a Jet 6 650c vs a Jet 6 700c with both sporting a GP4000S II.
Even though I'm 6'1" I've contemplated having a custom frame built with 650C wheels and something like 8.5cm of BB drop. Even though I run 165mm cranks I still get a bit of toe overlap as my cleats are pretty far back.
Even though I'm 6'1" I've contemplated having a custom frame built with 650C wheels and something like 8.5cm of BB drop. Even though I run 165mm cranks I still get a bit of toe overlap as my cleats are pretty far back.
Re: Who are these people that think everyone should be on 700C wheels? [Tom A.]
[ In reply to ]
Tom A. wrote:
30% rotational inertia drop is a ridiculous assumption..
I did say I pulled that out-of-ass! I don't know what it would be. More than 10%, at least?
Quote:
.and NO crit sprints are contested from a standing start.I was responding to the question, "Could you notice spin up effort from 0 to 20 mph?". And I have seen a crit won with a full sprint off the start followed by a 90-minute TT! (2012 San Marcos crit, I think). I knew the sprint was coming, but missed my first clip-in attempt and that ended my chance for latching on to the sprinting group.
But to make you happy, reducing the inertia difference to 10% and starting the jump at 20MPH (reasonable after a 180-type turn, say the Manhattan Beach crit), you get 0.01s and 12cm (same Crr, CdA, and wheel weight). Still, I'd argue, significant for a crit rider, when done say, for 40-50 times over a longer criterium. And 10cm can certainly be significant when trying to open a gap. Successful splits are sometimes a game of centimeters of "elastic." The game takes place in the margins of the draft effect.
I think the aero nazis are "trying too hard" in arguing that things like weight and inertia aren't important. They certainly look important in lots of non-TT situations. At least based off the simple physics involved. If you have two really aero wheels, and one is lighter, pick the lighter wheel! The differences may be in the margins. But on this site people have no problem arguing about the Conti SS vs. Conti TT or 15t pulley wheels vs 17t. So why not talk about the marginal performance differences due to weight and inertia?
Re: Who are these people that think everyone should be on 700C wheels? [jaretj]
[ In reply to ]
AFAIK frame geometry 'degenerates' under a certain size so 650 are needed for smaller frames, however, because of Economies of Scale and Stuff(tm), frame makers elect to just build those smaller frames around 700c anyways, all consequences be damned.
I'm not a frame builder though, nor understand the intricacies of frame design, just a person of average height, so as to why people would argue in favor of 700c uber alles, I can only speculate ¯\_(ツ)_/¯
Actually a roadie in disguise, please don't tell anyone!
I'm not a frame builder though, nor understand the intricacies of frame design, just a person of average height, so as to why people would argue in favor of 700c uber alles, I can only speculate ¯\_(ツ)_/¯
Actually a roadie in disguise, please don't tell anyone!
Re: Who are these people that think everyone should be on 700C wheels? [Travis R]
[ In reply to ]
Travis R wrote:
A while back, I started a thread on the availability of 650C bikes and components: http://forum.slowtwitch.com/...0650%202017#p6202120
The triathlon industry seems to have all but abandoned 650C, which is unfortunate. I think what we're experiencing is an attempt to standardize on one size for manufacturing simplicity at the cost of a few people. I can understand this, but I think the bike industry has done itself a disservice here. At some point in life, almost all of us fit a 650C bike, at least temporarily. Some of us stayed there, some of us kept growing. I work with a couple of devo cycling teams and would really love to see some more 650C options for those kids. Handling and toe overlap are a couple of things that are especially problematic with a small geometry/big wheel bike, and I think a 650C wheel on a small bike for a kid is a safety issue. It's nice to see Emma Pooley doing something about it.
The same can be said for the lack of 26" MTBs on the market now. Considering it was the de facto size just a few years ago, maybe "lack" isn't the best term there, but as a percent of wheel sizes available, that number is shrinking and the development is all going to 27.5, 29, and plus bikes.
While I'm bitching and ranting here, I would also like to see more 36cm or even 34cm road bars and affordable cranksets with 150, 155, or 160mm crank arms. I'd really like to see those as OEM spec on smaller bikes, too.
Getting quality cranks in shorter lengths is difficult. My daughter is 7 and 140cm tall. We've just moved from 20" wheels to 24". Hee mountain bike came with 165mm cranks.
I found some 140 cranks that are poor quality but now she can turn the pedals without hitting her chest with her knees.
Some kids bikes come with adequate crank length but buying them on their own is a headache.
I'm considering putting my adjustable cranks (90mm-200mm) on her bike. The issue is they are on an SRM 130bcd crank.
I understand why companies limit size runs. I've considered starting a component company selling parts for little people.
Cranks from 110mm to 160mm
Short reach brake levers and adjustment chocks for regular road levers. Maybe slimmed down hoods.
Narrow bars and smaller diameter tubing
650 wheels and TYRES.
Smaller saddles?
Narrow Q factor must be an issue for smaller people too.
Etc