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Originally Posted by Drew Eckhardt
(Post 18993385)
Lots. With mere mortals unlikely to tolerate low cadences better than professional riders we need gears half the size at 50% less power.
This ignores the fact that pros are considered over-weight at 7% body fat, while 74% of American adult men are over-weight and 36% obese. A 5'9" guy like Alberto Contador who should race at 137 pounds is overweight at 169, and obese at 203. Riding a 15 pound bike at the UCI minimum weight with 4 pounds of water/shoes/gear makes combined weights of 156 pounds when racing-fit, 188 over-weight, and 222 pounds obese; calling for 21% and 42% increases in gearing. Climbing a moderate 8% mountain like l'Alpe d'Huez where pros use 39x23, at half the power 5'9 guys who look like POW survivors should be riding gears like 30x36, the barely over-weight 26x36, and obese 22x36. Those of us with 10% grades should use 20% smaller granny rings when going all-out. Obviously things like all day endurance rides in the mountains and loaded touring call for even lower gears. |
Originally Posted by B. Carfree
(Post 18989990)
There's always this option: https://www.compasscycle.com/shop/co...-double-crank/
Get as small as you need. Again, as small as you need. Also is compatible with 11-speed drive-trains, and (if it matters), made in US. |
So turns out Praxis is using a typical 110mm BCD with standard chainring positions. I searched on bike rumor and found an article from earlier in the year.
"Shown here with their new Micro Compact rings, gravel riders will appreciate getting down to a 32 tooth ring thanks to the stepped mounting tab machined down to allow enough space for the chain on that tiny gear. Yep, that’s a 110BCD road ring setup that gives you a tiny 32 granny gear, while pretty much everyone else doesn’t go below a 34 because of the chainring bolts and tabs of the spider otherwise hitting the outer plates and rollers of the chain with a gear that small." http://brimages.bikeboardmedia.netdn...6/03/Micro.png |
according to a tinkoff mechanic, for super hilly stage, its 50/34 with 11/30 or 53/39 with 11/32
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Originally Posted by Bostic
(Post 19007552)
So turns out Praxis is using a typical 110mm BCD with standard chainring positions. I searched on bike rumor and found an article from earlier in the year.
"Shown here with their new Micro Compact rings, gravel riders will appreciate getting down to a 32 tooth ring thanks to the stepped mounting tab machined down to allow enough space for the chain on that tiny gear. Yep, that’s a 110BCD road ring setup that gives you a tiny 32 granny gear, while pretty much everyone else doesn’t go below a 34 because of the chainring bolts and tabs of the spider otherwise hitting the outer plates and rollers of the chain with a gear that small." http://brimages.bikeboardmedia.netdn...6/03/Micro.png |
That looks a little like the mod required to run a 41T ring on a Campy 144 crankset.
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Omg
To the rocket scientists on here that don't quite get it: 4 bolt 110BCD is smaller than 5 bolt 110BCD, THAT'S how it can fit smaller tooth numbers. If you still don't understand, picture a square with sides of 110mm versus a pentagon with sides of 110mm. Which is smaller? LMFAO!!!
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Found these rings for the Ultegra 6800.
https://absoluteblack.cc/oval-road-c...for-110-4bcd/# 30/46 & 32/48. Reading the page, they are doing several optimizations. First of all, the Ultegra 4 bolts aren't oriented on a square, but rather on a rectangle. That allows an oval ring to be used that fits onto the bolt holes better. Second, they're adding an extra spacer, spacing the small rings off of the spider, and I assume the large ring overhangs slightly to compensate. Third, they use special bolts. 7mm for the 32, and a mix of 5mm and 7mm for the 30. |
Originally Posted by redlude97
(Post 18988450)
what does what a pro that puts down twice the power a normal cyclist does have to do with it?
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Originally Posted by RG604
(Post 20694570)
To the rocket scientists on here that don't quite get it: 4 bolt 110BCD is smaller than 5 bolt 110BCD, THAT'S how it can fit smaller tooth numbers. If you still don't understand, picture a square with sides of 110mm versus a pentagon with sides of 110mm. Which is smaller? LMFAO!!!
The 110mm isn't the sides of the square, it's the diameter of the circle through the center of the bolts. (That's why it's named "Bolt Circle Diameter"...) The circle is the same either way -- 3,4,5 bolts. https://cimg6.ibsrv.net/gimg/bikefor...001e4c8e8e.png |
Originally Posted by CliffordK
(Post 20694638)
Found these rings for the Ultegra 6800.
https://absoluteblack.cc/oval-road-c...for-110-4bcd/# 30/46 & 32/48. Reading the page, they are doing several optimizations. First of all, the Ultegra 4 bolts aren't oriented on a square, but rather on a rectangle. That allows an oval ring to be used that fits onto the bolt holes better. Second, they're adding an extra spacer, spacing the small rings off of the spider, and I assume the large ring overhangs slightly to compensate. Third, they use special bolts. 7mm for the 32, and a mix of 5mm and 7mm for the 30. It appears they move the chain line in a little, use special bolts, and just barely clear the chain plates on the small chainring mount points. From the description: ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ IMPORTANT Due to very special 2.5mm offset construction of BOTH chainrings towards the frame and custom bolts: *30T can only work with 46T and special bolt set 46/30. (bolts included with small ring) *32T can only work with 48T and special bolt set 48/32. (bolts included with small ring)*No other combination or mix of rings will work. Due to special mounting construction, aesthetic bolt covers are not offered for this design *We Only recommend Dura-ace 11spd chain or Sram Eagle 12spd chain for proper clearance of mounting tabs ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Two normal bolts, two smaller bolts! This works with the ovalized ring. It's bolted from the outside. Stock Ultegra is bolted from the inside, without through holes to the outside of the big ring. Ugly, but a cool hack. https://cimg3.ibsrv.net/gimg/bikefor...96b6f232ab.jpg Big ring from outside: https://cimg9.ibsrv.net/gimg/bikefor...0ac2620deb.jpg Big ring from inside: https://cimg4.ibsrv.net/gimg/bikefor...41d90560ce.jpg .... Small ring: https://cimg6.ibsrv.net/gimg/bikefor...56d833a168.jpg A tiny bolt in this position, and minimal clearance! https://cimg9.ibsrv.net/gimg/bikefor...e040b750c5.jpg |
Originally Posted by RG604
(Post 20694570)
To the rocket scientists on here that don't quite get it: 4 bolt 110BCD is smaller than 5 bolt 110BCD, THAT'S how it can fit smaller tooth numbers. If you still don't understand, picture a square with sides of 110mm versus a pentagon with sides of 110mm. Which is smaller? LMFAO!!!
ride more. |
Originally Posted by mstateglfr
(Post 20694898)
you brought a 3+ month old thread back to life just to yell at other posters?
ride more. I'm always happy to learn something new. |
:popcorn
Anyhow ..gear down and watch, as you fall behind.. & Guys like Museeuw, pass you climbing on the big chainring.. |
Originally Posted by fietsbob
(Post 20695275)
:popcorn
Anyhow ..gear down and watch, as you fall behind.. & Guys like Museeuw, pass you climbing on the big chainring.. Big or little ring, I don't think I have to worry about keeping up with most pro cyclists, or retired pro cyclists. :backpedal: Some of my fastest hill climbs are those short climbs of < 1/4 mile, where I'm cruising along on the level at around 20 MPH (snappy for me), then transition from seated to standing on the hill, hardly dropping a gear. But, that only works for the short hills. I've started doing fewer standing hills, and more seated hills. But, the speed is still similar. Although, there is always the temptation to gear down too much, and creep up the hills. Still, my "climb cassette" is a 9/23 (great for going down too). I did have to go to a 34T small front sprocket though, primarily for one intense hill climb in Portland. :( |
Done the Skinner's Butte Criterium ?
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Originally Posted by mstateglfr
(Post 20694898)
you brought a 2 years and 3+ month old thread back to life just to yell at other posters?
ride more. |
Originally Posted by datlas
(Post 20695454)
fixed, and you must be new here, this is SOP for some people.
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My Praxis Alba 48/32 110BCD is a 5 bolt arrangement. Crank spider arms interfere with KMC 11 speed chain when on small chain ring. Very annoying! My conclusion is that 32 tooth chain ring is too small for 5 bolt 110 BCD chain ring.
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Originally Posted by baobao
(Post 18988427)
For a road bike, why would anyone even consider 46/30? What do the professionals in Tour de France use in mountain stages?
EDIT: Shoot.... just realized I am responding to a 4-year old post :o |
Originally Posted by Drew Eckhardt
(Post 18993385)
Lots. With mere mortals unlikely to tolerate low cadences better than professional riders we need gears half the size at 50% less power.
This ignores the fact that pros are too big to compete at 7% body fat, while 74% of American adult men are over-weight and 36% obese. A 5'9" guy like Alberto Contador who races at 137 pounds is considered overweight at 169, and obese at 203. Riding a 15 pound bike at the UCI minimum weight with 4 pounds of water/shoes/gear makes combined weights of 156 pounds when racing-fit, 188 over-weight, and 222 pounds obese; calling for 21% and 42% increases in gearing to maintain the same cadence. Climbing a moderate 8% mountain like l'Alpe d'Huez where pros use 39x23, at half the power 5'9" guys who look like POW survivors should be riding gears like 30x36, the barely over-weight 26x36, and obese 22x36. Those of us with 10% grades should use 20% smaller granny rings when going all-out. Obviously things like all day endurance rides in the mountains and loaded touring call for even lower gears. |
Originally Posted by baobao
(Post 18988427)
For a road bike, why would anyone even consider 46/30? What do the professionals in Tour de France use in mountain stages?
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Originally Posted by GBellairs
(Post 21718730)
My Praxis Alba 48/32 110BCD is a 5 bolt arrangement. Crank spider arms interfere with KMC 11 speed chain when on small chain ring. Very annoying! My conclusion is that 32 tooth chain ring is too small for 5 bolt 110 BCD chain ring.
Both were silent and produced no known run. One was for sure a kmc 11sp chain too. |
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