"The 33"-Road Bike Racing - Max rim section depth for crit/road racing??

Hi All,

Is there a max legal rim section depth for USCF crit and road racing? I couldn't seem to find this info on the USCF or UCI websites.

Any helpful info is greatly appreciated!

Thanks!

nope, you could run a disk if you wanted.

I know you can run a disc but I've always wondered about a front disc.

Track is going to be the only place alowed to run a front disc(maybe USA Tri, but I think it's outlawed there too).

If you show up with a disc front wheel to a crit, I am going to make sure I am at least a few bike lengths in front of you at all times.

If you show up with discs front and rear, I will put a frame bump in your spokes. I'll need a hole saw.

Track is going to be the only place alowed to run a front disc(maybe USA Tri, but I think it's outlawed there too).

What USCF rule says this? I'm not familiar with any such regulation.

Track is going to be the only place alowed to run a front disc(maybe USA Tri, but I think it's outlawed there too).

Disc wheels (front or rear) are not allowed for triathlons. However there is no maximum depth for the rims so you see some wheels with over 250mm deep rims (700c wheels are 622mm in diameter). They are basically disc wheels with the disc attached to the hub by really short spokes.

Disc wheels (front or rear) are not allowed for triathlons. However there is no maximum depth for the rims so you see some wheels with over 250mm deep rims (700c wheels are 622mm in diameter). They are basically disc wheels with the disc attached to the hub by really short spokes.

Disc's not allowed in tri's? Sorry, but you're wrong. They are perfectly legal for the rear. And the biggest non-disc at the moment is the Zipp 1080 at 108mm deep. Blackwell has claims of a 200mm deep wheel, but that would be the deepest out so far.

I would be wary of running any type of deep rim on the front in criteriums. Deep rim wheels catch a lot of air, which makes you squirrely, which is not what you want to be in a thick pack, especially going around corners.

The aero advantage of deep rims is minimal in a crit and completely cancelled out by so many other factors.

i would think that a lighter wheel that spins up easy is more inportant than aero, at least that's my feeling...the surges suck...most the time in your in a pack sooo..

i would think that a lighter wheel that spins up easy is more inportant than aero, at least that's my feeling...the surges suck...most the time in your in a pack sooo..

Light and nimble only rules in the most technical of crits and the biggest of mountain races.
Otherwise, aero always takes precedence.
Lots of studies out there.

What USCF rule says this? I'm not familiar with any such regulation.

USCF was/is supposed to adopt UCI regs which state:



For massed start road races only wheel designs granted prior approval by the UCI may be used. Wheels will have minimum 12 spokes; spokes can be round, flattened or oval, as far as no dimension of their sections exceeds 10 mm. In order to be granted approval wheels must have passed a rupture test as prescribed by the UCI in a laboratory approved by the UCI. The test results must show that the rupture characteristics obtained are compatible with those resulting from an impact sustained during normal use of the wheel. The following criteria must be fulfilled:

On impact, no element of the wheel may become detached and be expelled outwards.
The rupture must not present any shattered or broken off elements, or any sharp or serrated surfaces that could harm the user, other riders and/or spectators.
The rupture characteristics must not cause the hub to become separated from the rim in such a way that the wheel becomes detached from the forks.
Without prejudice to the tests imposed by the laws, regulations or customs, standard (traditional) wheels are exempted from the rupture test referred to above. A traditional wheel is deemed to be a wheel with at least 16 metal spokes; the spokes may be round, flat or oval, provided that no dimension of their cross sections exceeds 2.4 mm; the section of the rim must not exceed 2.5 cm on each side.
Notwithstanding this article, the choice and use of wheels remains subject to articles 1.3.001 to 1.3.003.



Has this not happened? I really haven't paid attention.

I've never seen any official ever checking anyone's bike, save for Junior roll-out.

Has this not happened? I really haven't paid attention.

No it has not. Only a few races under restricted conditions require UCI equipment. It's easy enough to check this stuff out before posting incorrect information.

Light and nimble only rules in the most technical of crits and the biggest of mountain races.
Otherwise, aero always takes precedence.
Lots of studies out there.

Exactly. At all of the races I've been to, the Pro's are rolling on deep rims. Sure, their sponsors want them to display their products, but a pair of 404s flying by at 30+ is just as blurry as a pair of 202s.

And maybe I'm the only one who does this, but moving up the outside if/when the pack slows is often a very good idea, and I'd rather do that with some 50mm carbon wheels than my Ultegra/OP's. Not to mention the standard breakaway, which puts a premium on being aero.

No it has not. Only a few races under restricted conditions require UCI equipment. It's easy enough to check this stuff out before posting incorrect information.


Okay, I stand corrected. A few of the races I am doing this year are reported to be UCI rules, so I have them on the brain. I'll ammend my statement: Anyone who runs a front disc off the track is not the brightest bulb in the bin.

Sorry for my misinfo.

And while you're citing rules, go get Yoshi. He is obviously out to misinform the world too. :rolleyes:

And while you're citing rules, go get Yoshi. He is obviously out to misinform the world too. :rolleyes:

I'm not a USAT official. I wouldn't want to comment on something I don't know anything about.

As a mainly crit rider, I think aero wheels help a lot in most crits. The ones with super slow hairpin turns (say, under 15 mph) are the exception. And this doesn't even apply to breakaway/chase efforts where aero definitely matters.

If you're in any sort of a normal crit, you'll be going pretty fast most of the time. It's unusual to slow down a lot for turns, and if you ride smart, you don't have to actually sprint out of turns too much - and that's no matter where you are in the field, not just the top 10 or whatever. You'll probably cruise at 22-32 mph (turns and straights included) and spike up to 40-42 mph (mainly flat course).

The aero wheels really help when the speed goes through the roof - a 5-10 mph surge for example, or you need to move up. If the field is already riding over the 30 mph range, you'll need to make a 35-40+ mph effort to move up. A box section wheel is hard pressed to go over 42 mph (just from experience, no backing data). However, it's not unusual to be able to move up at 44-46+ mph with aero wheels if you have a slight wind/draft or hill assist. Such a spike in speed is very difficult to make with box section wheels.

Aero wheels are especially helpful when the field is strung out or there's a crosswind (esp those wheels that do well in a crosswind). Once the field is strung out, the draft is not as significant as when the field is bunched up. You're going to have to work to keep your spot and an aero wheel will help you do that. I specifically bring my Specialized TriSpokes (HED3) for windy, flat airfield crits. I used to run a rear disk as well.

Finally, in a sprint, aero wheels could potentially increase your top speed by as much as 6 mph (personal experience). It seems that many riders have about the same wattage output in a sprint (i.e. 1500 watts peak seems sort of normal). Even if you jump at the optimal time, your 1500 watts only gets you a given amount of speed (frontal area, slope, wind, etc). If you can get even 2 mph by using more aero wheels, then you should.

I don't know for sure but I think the whole deep rim thing (and disks) have to do with limiting the speed the *spokes* hit the air. This is because the spokes are by far the fastest moving object on the bike. If you can reduce the spokes' drag, you'll reduce the bike's overall drag significantly since the rest of the bike is going at a much slower speed aerodynamically.

If your bike is going 30 mph, your tire is stationary on the ground (unless you're skidding). The top of your tire is going 60 mph. You can imagine your wheel sectioned so that the hub is 30 mph, 1/3 down is 20 mph, 2/3 down is 10 mph, all the way down is 0 mph. Then you go the other way - 1/3 up from the hub is 40 mph, 2/3 is 50 mph, top is 60 mph.

Based on a standard wheel (with tire) height, going 30 mph, the top of the spokes for the following shape rims hit the wind at the following speeds:
box (9mm) = 57.5 mph
slight aero (22mm height) = 56.25 mph
50 mm rim = 53.8 mph
66 mm rim = 52.4 mph
There's various other factors like rim surface area, the way air flows, etc, but nothing can dispute the fact that if you have a 700c wheel and you're going 30 mph, the spoke (or perhaps the spoke nipples) will be traveling at the speeds above based on rim depth and a 19 mm tall tire (I used 673 mm for overall wheel and tire height).

The spokes on the very deep section rim are hitting the air 5 mph slower compared to the box section rim. If you can go 30 mph on the box section rim (turn the wheels so the spokes hit the wind at 57.5 mph) and you switch to 66 mm deep rims, you'll be able to do about 33 mph for the same effort. Nothing except swapping wheels. Keep in mind this doesn't account for your body's drag - but it's a good way to compare spoke speeds to see what potential gains you might achieve by using different wheels.

On 50 mm rims, you'll be able to go 32 mph. Again, no additional effort. Same position, just gear up a bit for the higher speed.

On 22 mm rims, you'll go about 1/2 mph faster, about 30.5 mph.

I have a spreadsheet which does the calculations based on overall wheel height, bike speed, and rim heights you specify if anyone is interested.

The only time aero wheels don't work for you is if you have a very "jumpy" course - things like hairpins, wide straights dumping into a narrow and steep uphill, or a finish line less than the required 200 m from the last turn. Then accelerating to a very high speed in 1-2 less pedal strokes (from personal experience - 4 or 5 pedals strokes instead of 6 or 7) would be better than being able to accelerate to a higher top speed (which would take a total of perhaps 8-10 pedal strokes).

As for handling, aero wheels are definitely usable in crits with winds up to 30+ mph. You have to train on your front wheel so you get used to steering the wheel versus steering your hips - aero wheels get steered like a rudder. Once you do that you'll be comfy with aero wheels virtually all the time.

My helmet cam vids have me running either a DV46 (46 mm rim) or a Specialized TriSpoke in the front. You can see that my handling isn't affected by the wheels (and some of the races were quite windy).

For those that race in CT, NY, NJ, MA, and RI crits, this advice does not apply to you :)

cdr

I'm not a USAT official. I wouldn't want to comment on something I don't know anything about.

I see what you did there. :D

For those that race in CT, NY, NJ, MA, and RI crits, this advice does not apply to you :)cdr

:lol: no worries here at least, I have to get through my first crit at Bethel before I can dream of getting to the 3's!

Awesome advice as usual CDR.

If your bike is going 30 mph, your tire is stationary on the ground (unless you're skidding). The top of your tire is going 60 mph. You can imagine your wheel sectioned so that the hub is 30 mph, 1/3 down is 20 mph, 2/3 down is 10 mph, all the way down is 0 mph. Then you go the other way - 1/3 up from the hub is 40 mph, 2/3 is 50 mph, top is 60 mph.


I hate to nit-pick, but I'm gonna.

:)

I understand the point you're illustrating here, but your physics are off. Rather, you're not thinking about the situation from a physics point of view.

(It should be noted that what follows is a mathematician's interpretation of the physics of a rotating bicycle wheel. I only had to take Physics I & II, so my analysis is not nearly as in depth as something you'd see in, say, a fluid dynamics book.)

When dealing with a rotating object it's more helpful to think in terms of angular velocity. Every point on the wheel, regardless of distance from center, has the same angular velocity. If drag is represented by area x velocity (in the simplest of forms) then it becomes obvious how a deep dish rim would be advantageous. Note that I'm not even going to begin to touch on things like laminar flow as I am not knowledgeable enough to say anything on the subject, but there are other factors such as laminar flow that contribute to the equation.

Maybe there is a Mechanical or Aeronautical Engineer around that would care to give a more accurate description?

Maybe there is a Mechanical or Aeronautical Engineer around that would care to give a more accurate description?

I'm only a Chemical Engineer, but since I have a few publications on the subject of fluid mechanics, maybe I can comment. carpediemracing's description is accurate enough for me in the context of a bike forum. (and fluid drag is caused by the relative motion of a fluid past a body, angular velocity is relevant only so far as can be used to describe linear velocity.)

angular velocity is relevant only so far as can be used to describe linear velocity

I guess that is my issue. The linear velocity of a bike wheel at a point near where the tire contacts the road is certainly greater than zero. If it weren't there would be problems.

Maybe I'll ask my Aero Engineer uncle for a thorough description.....

I guess that is my issue. The linear velocity of a bike wheel at a point near where the tire contacts the road is certainly greater than zero. If it weren't there would be problems.

Maybe I'll ask my Aero Engineer uncle for a thorough description.....


This isn't horseshoes, "near" is not the same as "at" the point of contact.

Next time why not ask your uncle before wading in.

Only problem ive had with deep rims in Crits is on rough pavement. To me they dont feel quite as planted on the road as a traditional rim/sewup in that situation. I've always been willing to trade the aero for a little more confidence under those conditions (they occurred often in MI racing, crap roads). If you want the opinion of another ChE :)

A box section wheel is hard pressed to go over 42 mph (just from experience, no backing data).

When I'm riding them, ANY wheel is hard pressed to go over 42 mph. In fact, I've never pushed more than 34 mph on the flat, and that's a flat-out sprint - you can see why I avoid crits like the plague, can't you :D



However, it's not unusual to be able to move up at 44-46+ mph with aero wheels if you have a slight wind/draft or hill assist. Such a spike in speed is very difficult to make with box section wheels.

This may no be unusual for you, but I doubt many on here could hit 44-46 mph on any sort of wheel :eek:. Or maybe I just especially suck.

Either you meant km/h, or else you're an absolute gun ;)

When I'm riding them, ANY wheel is hard pressed to go over 42 mph. In fact, I've never pushed more than 34 mph on the flat, and that's a flat-out sprint - you can see why I avoid crits like the plague, can't you :D



This may no be unusual for you, but I doubt many on here could hit 44-46 mph on any sort of wheel :eek:. Or maybe I just especially suck.

Either you meant km/h, or else you're an absolute gun ;)

Ahhh you have much to learn. All the seppos who hang out on bikeforums ride Pro. No need to ask them they will tell you. :p

As a general rule divide everything said on bike forums by 1.17 to approximate reality.:)

where the tire contacts the road is certainly greater than zero.

For the purpose at hand, when the tire contacts the road it has zero velocity.

I'll ammend my statement: Anyone who runs a front disc off the track is not the brightest bulb in the bin.

And even track riders don't run front disks in mass start races, just time trials. And even then probably only on indoor tracks or in very still air.

I understand the point you're illustrating here, but your physics are off. Rather, you're not thinking about the situation from a physics point of view.

When dealing with a rotating object it's more helpful to think in terms of angular velocity. Every point on the wheel, regardless of distance from center, has the same angular velocity. If drag is represented by area x velocity (in the simplest of forms) then it becomes obvious how a deep dish rim would be advantageous.

His physics is fine. The wheel isn't just going round and round, it's moving through space.
Each point on the wheel is moving with some instantaneous velocity V_t (which is a vector) with respect to the hub. The hub is also moving through space (and most importantly, the air) at some velocity V_h, which is also the velocity of the bicycle.

At the outermost radius of the tire, (the magnitude of V_t) = (the magnitude of V_h), but the directions are very different--V_t at any point is tangent to the tire.

To get the velocity of any point on the tire through the air, you have to do the vector sum of V_t and V_h. At the contact point V_t+V_h=0 (as long as the tire is rolling without skidding). At the top of the tire, V_t+V_h=2V_h (directed parallel to V_h). At other points around the tire it has various values in between the two.

It makes it much easier if you draw a picture or two.

When I'm riding them, ANY wheel is hard pressed to go over 42 mph. In fact, I've never pushed more than 34 mph on the flat, and that's a flat-out sprint - you can see why I avoid crits like the plague, can't you :D



This may no be unusual for you, but I doubt many on here could hit 44-46 mph on any sort of wheel :eek:. Or maybe I just especially suck.

Either you meant km/h, or else you're an absolute gun ;)

I think he qualified that statement with both 1) downhill and 2) tailwind.

And if not, there are SOME races that could be possible at. Elk Grove Criterium (won by your boy Hilton Clarke in 2006) is a race where the pace can hit 35 on the flats with ease, and ramp up to 40+ in the sprint. Given a good leadout, and that course, definitely possible to go 42 if you're a horse.

I don't know for sure but I think the whole deep rim thing (and disks) have to do with limiting the speed the *spokes* hit the air. This is because the spokes are by far the fastest moving object on the bike. If you can reduce the spokes' drag, you'll reduce the bike's overall drag significantly since the rest of the bike is going at a much slower speed aerodynamically.



It's not just the speed at which the spokes hit the air, it's also the frontal surface of them-- each spoke has some frontal surface that it has to push through the air, doing work on air molecules. By having fewer of them and filling in the fastest part of the wheel (the outer ~3-4 inches or so), you reduce both the speed and the area of stuff that's pushing air out of the way. A disk is the limit as you decrease the spoke length to zero (i.e. going from Zip 202 to 404 to 808) or increase the spoke thickness to fill in the wheel (going from Specialized Trispoke to Mavic 5 spoke to disk).

I think he qualified that statement with both 1) downhill and 2) tailwind.


That'll teach me to read posts properly.



And if not, there are SOME races that could be possible at. Elk Grove Criterium (won by your boy Hilton Clarke in 2006) is a race where the pace can hit 35 on the flats with ease, and ramp up to 40+ in the sprint. Given a good leadout, and that course, definitely possible to go 42 if you're a horse.

If you'll excuse me, I have a LOT of training to do :eek:

This isn't horseshoes, "near" is not the same as "at" the point of contact.

Next time why not ask your uncle before wading in.

:rolleyes:

Fine. For arguments' sake lets say that we're examining a point on the wheel exactly 45mm from point of contact between the tire and the ground.


fluid drag is caused by the relative motion of a fluid past a body

Correct me if I'm wrong, but isn't air considered a "fluid?"

To get the velocity of any point on the tire through the air, you have to do the vector sum of V_t and V_h. At the contact point V_t+V_h=0 (as long as the tire is rolling without skidding). At the top of the tire, V_t+V_h=2V_h (directed parallel to V_h). At other points around the tire it has various values in between the two.


Right.

Any college student who has managed to pass a first course in physics understands this.

All I'm saying is that, while the wheel (at the ground) may have an instantaneous velocity of zero it is still traveling through space. And technically, wouldn't the instantaneous velocity of the wheel (at the ground) be considered the instantaneous velocity relative to the hub?

I really wasn't trying to start a pissing contest here, I just want to be sure people understand that the wheel (at the ground) is, in fact, moving.

:)

We all agree that deep dish wheels are beneficial in a criterium, and I'm pretty sure there are studies to back up the statement.

That'll teach me to read posts properly.



If you'll excuse me, I have a LOT of training to do :eek:

Yeah a friend of mine got to race next to Horner, Christian Vande Velde and Dave Zabriskie there.

You could feel the vacuum pulling you in as they went by. Just like a train. It was amazing.

Any college student who has managed to pass a first course in physics understands this.


Apparently not.



All I'm saying is that, while the wheel (at the ground) may have an instantaneous velocity of zero it is still traveling through space. And technically, wouldn't the instantaneous velocity of the wheel (at the ground) be considered the instantaneous velocity relative to the hub?


you can measure it with respect to whatever you want, including a duck traveling perpendicular to the course. Velocity is relative. The velocity we care about is with respect to the air, not the hub, but it's usually easier to diagram if you do the wheel separately from the bike and then with the bike.



I really wasn't trying to start a pissing contest here, I just want to be sure people understand that the wheel (at the ground) is, in fact, moving.


At the very bottom of the wheel, the instantaneous velocity of the wheel with respect to the air (which is what matters) is zero. It still has acceleration (towards the axle), but it's velocity is zero.

Right.

Any college student who has managed to pass a first course in physics understands this.

All I'm saying is that, while the wheel (at the ground) may have an instantaneous velocity of zero it is still traveling through space. And technically, wouldn't the instantaneous velocity of the wheel (at the ground) be considered the instantaneous velocity relative to the hub?

I really wasn't trying to start a pissing contest here, I just want to be sure people understand that the wheel (at the ground) is, in fact, moving.

:)

We all agree that deep dish wheels are beneficial in a criterium, and I'm pretty sure there are studies to back up the statement.

The wheel at the ground is infact NOT moving.

When a wheels rolls without sliding like on a bicycle there is no relative motion between the point of the wheel in contact with the ground and the ground itself.

I explained my wheel aero thing to a very, very smart guy at work why my bike (at my desk) had very tall rims. I drew a picture, brought the bike over to the lunchroom, showed him my theory on hubs, spokes, and splitting the wheel up into sections.

He's a very cool guy but he had to do all the angular velocity stuff (which I can't do) and came back to me the next day and said, "Yes, you're correct." Apparently he worked it all out and it came out okay - but he did it "officially". Then proceeded to talk about laminar flow stuff. He totally lost me there. Sort of a replay of the last few replies.

There's another way of seeing this in action - you ever see someone riding with the side reflectors in their wheels? The reflector goes down, pauses, the goes up, rapidly accelerating, then heads back down, slowing down. That's spoke speed near the rim. Even at a relatively slow speed (15-20 mph), that reflector is going pretty fast at the top of its arc.

re: sprint speeds

If any of you did SUNY Purchase sprints (they ended in the mid 90s), me (Cat 3), a former rider who sponsors Sakonnet Technology's team (demon sprinter, Cat 2 or 3 depending on his mood), a Cyclosport guy (forget his name, good crit rider, Cat 3), and a couple other guys (mainly 2s) would regularly hit 46 mph based on our computers (not just mine). Incidently I could never, ever beat the Sakonnet sponsor guy once he got STI - he beat me in every sprint where we were both sprinting for 4 or 5 years. Frustrating. The sprint is a slight downhill (1%?) but it's preceded by very tough 1 km downhill-then-rolling leadout which usually peaked at 38-40 mph (at 40 mph I'd usually be too cooked to sprint and I'd lose). I had at least one or two guys dedicated to leading me out for 10-15 or so of the 20-25 sprints. Field size was 100 or so regularly, sometimes up to 150-200, mainly Cat 2-4, a few regular Cat 1s (road and track), and sometimes guest appearances by local national level racers.

If you do Gimbles in NY, my Route 120 sprint speed (the first one) was about 42-46 mph, depending on how far out I went and how fit I was (top speeds in July/August). This is a slight uphill sprint (maybe 1%) but is preceded by a couple miles of fast, slightly descending roads and I'd use others as a leadout. I hope to do a helmet cam of this in summer 2008. The sprint is protected from any side winds (trees) so it's usually still air. I usually don't make it to the second sprint in Mamaroneck.

cdr

There's another way of seeing this in action - you ever see someone riding with the side reflectors in their wheels? The reflector goes down, pauses, the goes up, rapidly accelerating, then heads back down, slowing down. That's spoke speed near the rim. Even at a relatively slow speed (15-20 mph), that reflector is going pretty fast at the top of its arc.


I believe the shape the point on the wheel follows is called a cycloid.

And the top of the wheel pretty much always goes ~twice bike speed, as several people have noted.

I believe the shape the point on the wheel follows is called a cycloid.


It is indeed, and if you play around with them, cycloids have some interesting properties.