That's a decent wet tire if you are running reasonable pressure. 25 would be a bit better, especially at lower psi.

There's so much talk about brakes (which stop wheela) and less about tires (which stop bicycles)...

Stopping depends on so many factors. A Clydesdale running 100 psi in some paper thin Vittorias using rim brakes on carbon is going to have a far different experience than a 140 lb rider in the same situation. I personally prefer alloy with rim brakes, but I acknowledge that my next bike will certainly be disc brake, which will presumably resolve the 2-4 times per year that I have a "Holy sh**..." moment in my current set up.

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Carbon brake tracks, regardless of design, suck at braking.
Disc brakes FTW.

Agreed. Braking surfaces are best when they are metallic...or ceramic coated over metallic...especially with "texture", be it by holes or grooves, or whatever...

I just like to use the largest diameter braking "disc" possible...even better if it doesn't add aero drag ;-)

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http://bikeblather.blogspot.com/

Side question - are you toeing in with the front of the pad touching first or the back? I've read conflicting opinions on the best way to do this.

I guess after a few rides it won’t matter, the contact point will be worn and the whole pad will touch. I usually place the pads flat on the braking surface.

On a side note, to answer the OP yes I switched from carbon to aluminium (hed jet black). And considering the current prices of disc brake TT bikes I’m planning to stick with rim brakes for a while.

Unless you are racing up and down mountains, its difficult for me to imagine how carbon rim braking power is a problem, even in the wet. On a flatish course, my cheap Asian knockoff rims and blue pads are all the braking I need. I mean, it's a race, how much are you really braking? Earlier this year I was at what was predicted to be a dry race. Showed up to spitting rain and a saturated course. Did I wet my bibs because my race bike had carbon rims in these conditions? Nope, worked fine.

For my Madone road bike I sold my 404s and went back the Jet Black 6s. I liked them so much I swapped out my C2 generation Jet disc and Jet 9 for the equivalent Jet Blacks. My TT bike is a Speed Concept and the Blacks are a big improvement.

I also N+1ed and added a System6 disc road bike to the fleet last year. The disc bike maybe has a bit more stopping power and better modulation than the brakes on the Madone, with a heavy emphasis on maybe. Calipers and levers can by pretty iffy on TT/Tri bikes, so I think disc brake performance is probably significantly better. Paying for a new disc brake TT bike is a whole other issue and none of your rim brake stuff transfers over.

Oh man, I have the total opposite of you (as I suspect most) - the moment it's wet, and carbon braking for me goes to pretty terrible. Like scary-level, like 3x or 4x the normal stopping distance of an alloy brake. This is with SwissStop Black Prince too, which is supposed to be one of the best for wet carbon braking. Luckily I don't ride in wet almost ever - was unlucky with light rain in a short race recently and I didn't like the descent at all!

I find it strange that you accept mountain riding may be a problem and yet have difficulty imagining "how carbon rim braking power is a problem". First a few questions: How heavy are you? Do you only ride on pretty flat terrain? Do you think racing means not using brakes?

Incidentally, the moment someone says something like "it's a race, how much are you really braking?", their credibility is shot. The faster you want to go, and especially the faster you want to approach corners, or descend, the more important braking becomes. That's leaving emergency braking to one side, and that should never be left to one side!
What is the relevance of your anecdote about turning up to one wet race and not being scared? If anything, mentioning it makes it seem like this was a novelty for you, casting even more doubt over your credibility.

Let's just consider the relative requirements from brakes for different uses:

Kinetic Energy = 1/2 MV^2

So the energy your brakes need to dissipate increases in proportion to your mass and in proportion to the square of your speed.
My mass is between 80kg and 85kg depending on the season, my current focus, etc.
I descend reasonably quick (and I descend reasonably fast whether I'm racing or not). I regularly hit 80km/h+
My Tri bike is a Felt IA which is not a lightweight at about 9.5kg IIRC and I'll add another 3kg as a conservative figure for water bottles, shoes, helmet, clothing, repair kit, bike computer, phone & keys.

So I could very easily find myself with a rolling mass in excess of 97.5kg and speed in excess of 80km/h.

KE = 0.5*97.5*22.2^2 = 24026 Joules

For comparison, a reasonably light guy (say 60kg), riding a road bike (say 7kg plus the same 3kg of extras) on the flat at a respectable 40km/h:

KE = 0.5*70*11.1^2 = 4312 Joules

The fact that the first example is on a descent can also add considerably more to the potential braking demand, but I'll ignore that now to keep things simple and very very conservative. So as you should now be able to understand, I regularly need my brakes to do at least 5.7 times more work to stop me compared to the lighter guy travelling at typical racing speed on flat roads. Even if we leave the mass of the rider and bike out of it, My same 97.5kg mass at 40km/h only requires 1/4 the work to stop compared to 80km/h (difference is square of the speed diff). Now, I've REALLY simplified things here. I'm not talking about braking power, just the total work they need to do for a given stop, ignoring aerodynamic, gravitational, and other influences. Braking distance depends on how quickly the brakes can do this work, i.e. brake power, and that's where the traction available from carbon rim brake tracks becomes a liability. The difference in brake power required will be considerably greater again than the difference in the brake work required. I would expect to need well in excess of 12 times the brake power to stop in a given distance compared to the 60kg & 40km/h example above. As others have mentioned, tyre traction is also a factor, but I've never skidded my front tyre (typically 25mm GP5000 on 19.5mm rims at 70-80psi) and I have pulled my brakes hard on a few occassions. Equally important, I've modulated my braking while decelerating hard, which is facilitated by not being at the very limit of the brake's traction.

Whether or not you rode a flattish race in the wet without concern has little bearing on whether anyone else should think your setup performs adequately.

Ditto. I ride a HED Jet Black front and rear and the stopping power in wet is incredibly good. No issues Saturday either.

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Mark Saroni
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COACHING | TRAINING PLANS
MS Kinesiology | USAT LII | USAC L3

The real deal with disc brakes is when you compare mediocre equipment. Mediocre disc brakes will outperform mediocre rim brakes with mediocre wheels, specially in extreme conditions. But higher end rim brakes with high end wheels are as good, if not better that disc brakes. That is why the podium of the GCs has been so hesitant to leave rim brakes.

I’ve since gone to disc brake, but honestly, I never understood why any
AGer was riding carbon. So, yes, if yiu are still riding rim brakes, I would suggest switching back. In fact, I would go stronger and do what other in here suggested and buy HED black. They aren’t any more expensive than your carbons and the braking is great. Want another reason/option? Flo aluminum/carbon disc is actually slightly faster than it’s carbon version.

In May I replaced some 50mm carbon clinchers for a set of Flo 90/disc aluminum brake faired wheels and I could not be happier. I started the season out with 3 wet races and was SO FREAKING HAPPY I had better braking. I'm from a flat state and can turn a 25mph split in short course so aggressively attacking the corners and descents is a really important part of my races as they're so short. I have a forever frame (QR CD0.1) with all the upgrades... In this era of peak aero I am probably only missing a super stem so I have no need or want to upgrade *just* for disk brakes at this point.

Even in the dry they are better. I was out of state for a race 2 weeks ago and hit 44 mph on a downhill portion of the course and was very happy to have the repeatability of aluminum brakes. I had experienced slight inconsistency in initial bite and threshold braking modulation even in the dry with carbon tracts.

I run HED Jet+ Black wheels for road racing, cannot see the need for any additional stopping power, especially at the expense of additional complexity on my bike. I had a Jet+ Black disc for my TT bike, but ‘downgraded’ to the standard silver rim’d disc because the braking power of a Omega X brake on the Black disc was too strong on a bike with my weight more to the front.

I’m a huge fan of the various HED offerings, seem to me to be the best all-around combo of aerodynamics, reasonable weight, great braking, low price, and flawless tubeless setup. Chicken Dinner!

I would never ride carbon clinchers before switching to disc brakes. I'm heavy and I like to be able to brake hard without fearing that my wheels could fail in a 90+ km/h descent and kill me.
The only wheels I own are a jet 6 front and a Citec disc wheel, its great, light, cheap and braking power is awesome, best of every world in my opinion except for the ugly alluminum brake track.

I haven't discussed disc brakes. I'm talking about alloy brake tracks being a sensible idea and carbon brake tracks being a poor engineering choice driven by the marketability of carbon.

However, I'm very skeptical of the notion that pros are choosing their wheels/brakes based primarily on objective performance analysis. It's heavily driven by advertising interests with the disagreement stemming from the differing stances of conservatives, traditionalists, weight weenies, neophiles, and vested interests. I'm just an outside observer and may be very wrong, but I'm neither an irrational conspiracy theorist nor naïve.

Typically, very little. But when that car decides to blow through the police person. Or the police person waves the car through when they shouldn’t, or when there’s a sharp turn at the bottom of the steep hill that you didn’t anticipate, brakes matter more than 3 seconds faster race time. At least to me.

Have you tried the carbon offerings with ceramic coatings? I have not, and am curious to your comment about ceramic over metallic vs ceramic sprayed on carbon. I remember maybe 8-10 years ago a startup Swiss brand doing carbon wheels with a ceramic coated alloy strip bonded to the carbon. The idea was to get the improved braking performance without the heavier aluminum rim structure. I think they sponsored a cyclocross team for a year before disc took over. Your comment made me think of that.

As for me - I am still holding on to my ancient Mavic Classics SSC tubulars. Grippy ceramic rim there, although it does wear off over time. Combine those with the green ceramic specific brake pads, and it is a thing of beauty for cross. In everything but snow, I even get bite without the one wheel revolution wipe down.

I haven't tried ceramic over carbon...I think the issue there would still be the quality of the resin used in the composite and whether or not it has the ability to resist softening at the elevated temps of braking on carbon (a problem due to the low heat capacity and poor thermal conductivity of a carbon composite).

My main experience with "ceramic" is with some PEO (Plasma Electrolytic Oxidation) coated Boyd Altamont rims. The braking on those is nearly as good as with the Hed Jet Black "Turbine track" treatment (which I believe is just a "normal" black anodization over the engraved braking surface). The interesting thing about the PEO coating is that when run with the relatively soft recommended SwissStop BXP pads, there's basically little to no wear of the surface (the PEO coating is quite hard).

I was EXTREMELY disappointed to learn last year that Boyd had no plans to continue producing their PEO coated rims...thanks A LOT disc brake fanbois :-/

I'm pretty sure FSA still has a range of wheels with a PEO coated brake track though...actually, NOPE...just checked. Looks like they have NO rim brake wheel offerings at all any longer. So stupid.

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http://bikeblather.blogspot.com/

Really? For all of the excellent math you provided, you neglected to add the potential energy of descending down a mountain. Let me help. The PE that must be converted to heat by braking is PE = Mg(delta H). So, for you (M = 97.5 kg, with the bike +), descending 300 m (not that much) at a constant velocity (no change in KE) would require PE = 97.5 * 9.81 * 300 = 286,943 J. WOW. That's more than 10x the energy required for the KE change you calculate below. And a 300 m descent is hardly 'mountain riding' (my term). So do you see why braking might be more important for mountain riding than for stopping from 80 km/h? The bottom line is that the braking energy required to reduce velocity on flat ground under any reasonable bike racing scenario is so far below the capabilities of rim brakes of any modern design (or disc brakes) as to be irrelevant to the selection of the braking system. Problems and failures occur resisting the conversion of PE to KE when descending long and/or steep grades.


Have you been Google stalking me? I am, in fact, about 60 kg - just as in your 2nd example! I'm in TN, but not on the eastern side where there are some real mountains. My rides and races are 'rolling' hills - frequent, but rarely more than 200 m of elevation per climb and more like 100 m.


Well, I try to minimize using the brakes because for every J I convert to heat from KE or PE by braking, I'm probably going to use *my* energy to replace that J. And since I'll run off the bike, I'd like to keep my energy as high as possible. Do I have to brake in a race? Of course - your question is pretty silly (unless you think that I've never raced).


Well, earlier in the thread there was talk of using aluminum wheels for more braking power and, especially, in the rain. I was simply pointing out that it is, in fact, possible to have full carbon wheels that provide good braking in the wet. Disc brake zealots (not that you might be one or anything) seem to think that such a claim is a complete lie, but I can assure you that it is not, as reported by others in this thread (and elsewhere).


Are you saying that your disc brakes, even when 'pulled...hard' are incapable of locking your wheel up (skidding)? Huh! I can do that in the dry and in the wet with my rim brakes on a full carbon wheelset. Now, it's easier to lock up the wheel in the wet (all other things equal) because the coefficient of friction between the tire and road surface is reduced by the lubrication of the water. But, still, the fact that I can lock up my wheels with my braking setup suggests that the potential stopping distance of my rig (again, all other things equal) is no worse than for disc brakes.


Ah, so you thought that my post was about *you*. My setup performs more than satisfactorily *for me*. If I were, say, discussing braking a loaded cargo bike down an Mont Ventoux, my thinking would be different. But the OP (and others) claim that the braking performance of full carbon rims is so inadequate that a move to aluminum rims might be warranted. That is certainly possible in some situations, but there is a pretty large envelope of rider/bike mass, descending conditions, desired velocity changes, etc. for which rim braking on full carbon wheels is totally safe and not inferior to disc brakes.

All of this is pretty moot though, don't you think? It won't be long before market forces dictate that practically any new bike purchased will have disc brakes, relegating untold metric tons of high quality bike parts (wheels, mostly, that can't be converted to disc brakes) to the landfill. Awesome.

Let's be clear, pro have full time mechanics and they don't pay for their gear... so who care if they need to change their wheels few time a year because their brake pads are a little too abrasive !! and they probably don't brake that much.

Otherwise cycling is an optimization problem, if you want to maximize :
- braking in the wet and cost than, yes aluminum wheels are your choice.
- If weight is your priority, then carbon is best.
- if Aero is your priority, once again carbon.
- if braking is your priority, hydraulic disc are the best.

Nothing wrong with having a good set of reliable aluminum wheels to but on your old trainer bike. Depending on your priorities, it's a great economical choice.

Keep in mind that many people here will happily spend $10-15K on a new bike with the hope of saving few minutes on a IM. And depending on the course, you may just need your brake to slow down at the aid station.

I for one would really, really like to know the carbon wheel + brake combo that performs so well in the wet.

In rain or wet, I'm already finding alloy braking slightly dicey, and in the one race I did in a hilly course with a light drizzle, my carbon wheels were borderline hazardous on the twisty descent, and I don't consider myself a bad descender (with alloy wheels I'm usually one of the fastest descenders on local hillclimbs riding with similar-abilitied riders or with the local club).

Took just that one race to realize that I realize have to purchase a set of HED Jet Blacks or just be ready to use non-aero alloy wheels in races where rain or drizzle is on the forecast, as my carbon braking was so hazardous.

In dry conditions, which is where I do 90+% of my riding, and on nonmountain terrain, my carbon wheels work fine, with only a small penalty to braking compared to my alloys.

You seem to think you've caught me out on something?
First, quit the condescending bull about my providing excellent maths. It's pretty darn basic and simply an attempt to explain the error in your logic as simply as possible while remaining at least a little rigorous. To that end, I didn't discuss potential energy in any detail at all, but did state that I was omitting it intentionally. You failed to include the following in the quotes you provided from my post:

Ai_1 wrote:

The fact that the first example is on a descent can also add considerably more to the potential braking demand, but I'll ignore that now to keep things simple and very very conservative.

Quit the bull. Of course we don't brake unnecessarily while racing, although most of us rarely brake unnecessarily any time we're riding so I don't see the difference really. Safe braking is every bit as important during a race as at any other time. The argument that you don't need brakes when racing because you want to go fast is simply imbecilic.


No, your example doesn't demonstrate whether or not carbon wheels can provide good braking in the wet. It's hardly even an anecdote, never mind evidence. No context, and the finding you claim is simply a statement of how safe you felt. A non-technical flat ride in the rain is typically not very demanding on brakes, even if you're a fast and heavy athlete. You're not heavy, no idea how fast you are, and the course is a mystery. You told us nothing of use whatsoever.


I don't have disc brakes. I didn't say I can't skid the front wheel, I said I haven't. That's a good recipe for a fall and I don't try to fall. I said I have pulled the brakes hard and not skidded the front wheel. I did not say or mean that the front brake couldn't apply more braking to the wheel. I agree that if your braking can lock up the wheels, and also provides good modulation, it suggests you have adequate performance.

Eh, this is a rather confused paragraph to my mind! I'll just make a few comments.
No I didn't think anything was about me. Why would I, and what in the quote you provided from me suggests that?
You are arguing that carbon brakes are perfectly fine and offered a vague anecdote to support that assertion. I contested it's relevance. If your claim was not part of an argument for discussion, why did you post it as such? You did not at any point in your earlier comments suggest that you were only talking about your specific needs. You were suggesting that those saying carbon is a poor choice for brake tracks are wrong. Were you not?


My argument throughout is simply that carbon is a poor choice of material for a rim brake track and that it's ubiquity is not rooted in wisdom.


You have in this paragraph explicitly conceded that there are circumstances where carbon rim braking is sufficiently inadequate to warrant a move from alloy to aluminium rims. I've put it in bold for your convenience. So our only disagreement appears to be whether or not those who should skip carbon are a tiny minority, a significant proportion, or a majority of riders. Let me be clear: the entire point of my post providing some very conservative, massively simplified calculations regarding braking demand was to illustrate how varied braking requirements are even within very normal use and thus how the arguments of light riders, who rarely ride in the wet, and perhaps rarely descend at speed are not a good basis to support the ubiquity of full carbon wheels with rim brakes. It's like arguing seat belts are unnecessary because you've never crashed and you feel safe on your commute to work. Your arguments have not rebutted the assertion that alloy rims offer better braking potential and are generally a wiser option. With all due respect, your arguments have actually just been noise. This is shown by the fact you essentially contradicted yourself in the bold text above.
If you want to argue that some, or most people, are adequately served by carbon brake tracks and shouldn't consider changing to alloy, then do so. But you've just tried to argue that carbon is perfectly adequate as a blanket statement, only to concede otherwise at the end.


Nope, it's absolutely not a moot point. Plenty of us are still riding bikes with rim brakes. The point under discussion is whether there's a valid argument for switching from carbon to alloy brake tracks. That is the thread topic. I would not choose to ride full carbon rims on my rim brake bikes. I am not buying a new bike with disc brakes any time soon. The OP and many others are in the same position, so how is it a moot point?

You are in fact using rim brakes yourself, so it's baffling that you are saying rim brake performance is a moot point!


That's an abnoxiously long post - apologies folks!