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Why no disc on road bikes?
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My tri bike was stolen a few weeks ago out of my storage locker. Not the end of the world as it was an older bike but terrible nonetheless. I'm looking at buying a road bike (perhaps cervelo s2) since now that i have two young kids i'm more interested in doing olympic and sprints rather than 70.3 etc, plus i want to do some group rides.

The thieves left my disc wheel that was sitting close to the bike. It got me thinking, why do I never see discs on road bikes? Do they not fit? Do they not work properly with the road frame set-up? Or is it just because if you're doing a crit race you will be draftign and if you are doing a non-draft race (i.e. time trial) you will be on a time trial bike? What is the difference then with having a disc wheel vs. deep dish wheels?
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Re: Why no disc on road bikes? [blueQuintana] [ In reply to ]
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1) Heavy
2) Harder to pump up (valve adapter, etc)
3) Flying rocks dent and damage them over time.
4) Handling can be harsher depending on the construction.
5) May be illegal in mass-start events depending on governing body.
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Re: Why no disc on road bikes? [blueQuintana] [ In reply to ]
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There could be rules barring them from use in normal road racing formats, but practically speaking they're much heavier than normal spoked wheels, thus harder to accelerate and maneuver, very important for crits. Plus when racing in peloton or even in small group, you will be doing lots of drafting so the aero benefits aren't truly realized this the weight isn't worth carrying around. I'd also imagine they're harsher to ride and less durable compared to spoked wheels which in addition to weight is why they aren't used by weekend warriors on training rides.

Others can probably add to this reasoning.
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Re: Why no disc on road bikes? [PBT_2009] [ In reply to ]
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Personally I think it's just fashion.

Track mass start racers widely use discs. Which kind of throws out the acceleration/weight/handling issue, since those are critical in a track mass start race - maybe even more than on the road. Also kind of throws out the drafting rationale since there's plenty of drafting in mass start track.

They're not banned by USACycling for any road event. I've toyed with the idea of checking with a race director/official, then showing up to a RR or crit with a disc, but have never had the nerve. You pretty much have to win if you do that, and I'm not nearly good enough to guarantee myself a win. :)

Edit: I also think the comfort rationale is kind of bogus. I've never had comfort issues on the road with a disc. Maybe there'd be some risk of damage from flying rocks, etc. But that's pretty small risk, in my opinion.
Last edited by: trail: Mar 27, 17 12:25
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Re: Why no disc on road bikes? [blueQuintana] [ In reply to ]
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I've done some tris that were pretty technical and hilly, so I used my road bike and threw my tri race wheels on it. Zipp 404 front and Zipp 808 rear with wheel cover. It looked super cool and handled great. So you could use a disc on a road bike, just totally depends on the case. And if you use a wheel cover, you don't have a lot of the weight and damage issues of a real disc.

That being said, my son wanted a wheel cover like mine and we got him one for xmas, but he had to take it off for his draft-legal youth tri races - they didn't allow them.

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Re: Why no disc on road bikes? [trail] [ In reply to ]
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In the future, all bikes will be made of wood and pipes and have disks front and back! Look at them happy kids riding! (at 3:20 into the movie [The Giver], the kid on the right almost falls off the path).



Two wheels good. Four wheels bad.
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Re: Why no disc on road bikes? [DrTriKat] [ In reply to ]
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Covers are not allowed in UCI racing, they must be permanently attatched.
Speeds on a velodrome are much higher, disc offers real advantages in all events.
A disc will get you shunned in a pack for fear of crashes in heavy sidewinds.
On average, a proffessional road racer only pedals for a little over half the distance of a road race.
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Re: Why no disc on road bikes? [lyrrad] [ In reply to ]
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lyrrad wrote:
Covers are not allowed in UCI racing, they must be permanently attatched.

USACycling allows covers, though. And maybe other national bodies.


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Speeds on a velodrome are much higher, disc offers real advantages in all events.

I'd argue that road speeds are plenty high enough for real advantages. Crits can easily average 30MPH or higher, which is on par with a track scratch race. Sprint speeds can exceed 40MPH just like in track.

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A disc will get you shunned in a pack for fear of crashes in heavy sidewinds.

That's just perception, not reality, though, as we know here at Slowtwitch. Also I firmly believe that discs are safer in crashes than spoked wheels. I've believe I've had my ass saved by my disc twice. Both times were on the track when I was riding through the middle of the carnage of a crash ahead of me. One time a rider's foot slammed into my disc, knocking me sideways. The 2nd time it was a whole bike that flew right into my rear wheel hard enough to dent the disc wall in several places (and bruise the hell out of my leg) I didn't go down in either case. I'm pretty sure if I'd had spoked wheels I'd have been pretty likely to have gone down.

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On average, a proffessional road racer only pedals for a little over half the distance of a road race.

I don't see how that's relevant. No better time to have disc than balling a non-technical downhill at 50+ MPH while not pedalling.
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Re: Why no disc on road bikes? [trail] [ In reply to ]
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trail wrote:
They're not banned by USACycling for any road event. I've toyed with the idea of checking with a race director/official, then showing up to a RR or crit with a disc, but have never had the nerve. You pretty much have to win if you do that, and I'm not nearly good enough to guarantee myself a win. :)

Here ya go: http://www.youtube.com/watch?v=2QVCdYTx004

Forward to 1:20. Those in the know will know who that is :-)
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Re: Why no disc on road bikes? [blueQuintana] [ In reply to ]
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blueQuintana wrote:
My tri bike was stolen a few weeks ago out of my storage locker. Not the end of the world as it was an older bike but terrible nonetheless. I'm looking at buying a road bike (perhaps cervelo s2) since now that i have two young kids i'm more interested in doing olympic and sprints rather than 70.3 etc, plus i want to do some group rides.


The thieves left my disc wheel that was sitting close to the bike. It got me thinking, why do I never see discs on road bikes? Do they not fit? Do they not work properly with the road frame set-up? Or is it just because if you're doing a crit race you will be draftign and if you are doing a non-draft race (i.e. time trial) you will be on a time trial bike? What is the difference then with having a disc wheel vs. deep dish wheels?


For any mass start road racing conducted under auspices of UCI, they are not permitted.


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UCI reg 1.3.018: Wheels of the bicycle may vary in diameter between 70 cm maximum and 55 cm minimum, including the tyre. For the cyclo-cross bicycle the width of the tyre (measured between the widest parts) shall not exceed 33 mm and it may not incorporate any form of spike or stud.
For massed start competitions in the disciplines road and cyclo-cross, only wheel designs granted prior approval by the UCI may be used. Wheels shall have at least 12 spokes; spokes can be round, flattened or oval, as far as no dimension of their sections exceeds 10 mm.

For any mass start road racing conducted under auspices of USAC, then they are permitted, except for riders aged up to 14 years who are required to have wheels with a minimum of 16 spokes.

Disc wheels have different handling characteristics to spoked wheels which make them less suitable for this sort of racing. In a solo ride scenario, a side gust moving you a little laterally is no big deal. When you are suffering in the gutter hanging onto when the hammer goes down, well going off the edge of the road isn't a lot of fun. And neither is riding in a group when your lateral movements are unpredictable.


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Re: Why no disc on road bikes? [BrianB] [ In reply to ]
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Paul Curley?
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Re: Why no disc on road bikes? [bm] [ In reply to ]
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yes ... and the lesson is "if you're going to descend left of center, you shouldn't call attention by being the only one in the race with a disc"
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Re: Why no disc on road bikes? [blueQuintana] [ In reply to ]
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In most TT's I have entered there is a Merckx division for people who only own road bikes. One of the limitations is wheel depth can be no deeper than 50mm. Anything more and you would be racing against riders with full on TT bikes.
Last edited by: kkerns: Mar 28, 17 4:26
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