TT/triathlon bike: disc or no disc

The trend in road bikes is definitely all-in on discs brakes. I can’t see many new models being announced from 2022 onwards that include a rim-variant. And most wheel R&D investment is going into disc wheels. Rim wheels will continue to be sold, but technology for them will remain relatively static.

Given the conditions most TT bikes are ridden in (straightish roads, moderate descents, not in a bunch), there is little reason to want disc brakes on the bike itself.

But if you are running a fleet of wheels that you (intend to?) swap between your road bike and your TT bike, then it may make sense to switch everything to a disc system.

I am, that’s why I wrote in my first post that rim brakes are an option if he finds a good deal on a used bike. If you buy new, then go disc.

That’s a wild exaggeration, if you talk to firemen, you’ll hear of fires. If the shop has many customers on mountain bikes, they’ll have 20 years worth of experience with disc brakes.

Funnily enough, this is how I got my current road bike at a steep discount: the previous owner couldn’t figure out how to align the brakes properly. He claimed he brought it to a shop (in Japan where few shops sell proper mountain bikes and presumably have way less experience with disc brakes). They couldn’t fix it. He sold it to me, and it literally took the guy in my shop 5 minutes to fix it. (I would’ve done it myself, but I accidentally dropped the rd cable in the frame and couldn’t get it out as I didn’t have the proper tools.)

I’m confused by this: rotor sizes and bleed ports have been standardized years ago. Ever since I got my first disc brake-equipped bike in 2004ish, rotors came in 160 mm, 180 mm and 203 mm. I don’t remember when 140 mm rotors were added or whether they have existed all along. On XC mountain bikes disc brakes started with 180 mm in the front and 160 mm in the rear, many have now migrated to 180 mm front and rear. Also, I can use the same bleed kit on my 8-year old XT brakes than on my 4-year old 105-equivalent hydraulic disc brakes. I use the same hydraulic oil for both of them, too. Sure, there is no cross-manufacturer compatibility, but that is true for many other parts as well.

I wouldn’t worry about axle pitch difference as a major issue at this point, covid supply/demand issues aside… if it turns out my bike has a “non-standard” TA in three or four years, I’ll just buy a spare or two from an aftermarket company.

But the fogey in me would still be riding cantis for cross this year if I trusted the oft-crashed carbon fork on my 2007… Hell, it would still be 2x9 if I didn’t break a shifter in a race one year.

I’d go rim, and get two or three sets of used aero WHEELS on the secondary market. Not worried about the used bike/frame/group market in this instance, as they are generally thought to be less important to aerodynamics than wheels and rider kit.

I understood the difference in our recommendations, I just have a different opinion on what the best solution is. If you want to go rim brake, I see no advantage in getting a new frame. That’s because most manufacturers have essentially stopped developing their rim brake frames. There are exceptions, yes, but if you look at road bike frames, for example, then rim brake models often use older frames (BMC comes to mind).

So if you want to go rim brakes, IMHO you should go whole hog used.


No exaggeration at all. EVERY single point you mentioned pertains to mountain bikes, where there is a need. The poster was talking specifically about TT/Tri bikes. That is where the issue is. Swap a wheel on a tri bike with disc brakes and see how long it takes to align the rotors again…

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Why would it take longer on a TT bike? Why do you assume that rotor alignment is necessary when you swap wheels? Seems you base that off of worst case scenarios rather than lived reality for most people. Rotor alignment isvery consistent with thru axles, btw.

Almost all bikes, including TT and tri bikes are going disc brakes. We are just arguing until what point new rim brake bikes remain a viable option.

No, better, more consistent braking in all conditions with less lever force applies to all cycling. You have to contend with stuff like traffic and rain on a TT bike just like on any other bike.


Ok, obviously you prefer to argue with my opinion. That’s cool. I only see 20 to 30 bikes per week and base that on what I see. The fact that a rotor is 2mm thick, can bend and has a clearance of 1mm on each side at most tends to make me feel that there is a lot more “play” in a rim brake should anything happen and if one has to get a hand up wheel in a race. Add the fact that some are 140 discs, some 160 and it can be an issue. Add in that to date no rim brake bike has been shown to be more aero than the rim brake equivalent, I would not want to throw away watts. Where things are going in the future is somewhat obvious, but I prefer to wait until these various issues are solved in a better fashion. As I said, strictly opinion, and many years of top level experience has served to form my opinion. Obviously we’ll agree to disagree and I’m sure each will be sure our solution is right. The OP has a lot of various opinions and can use whatever he needs to make his/her choice.

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This is indeed a valid point of criticism. Brake lever feel is something that is carefully engineered, and I vastly prefer how mountain bike brake levers act: there is a first “indent” where you have a force minimum, where the brake is fully disengaged but at the ready. Then going from free spinning to locking up the wheels is just a subtle squeeze. I wish the brake levers on my drop bar bike (currently Shimano 105 equivalent, mixed with Ultegra 6800 components) acted the same.

Shimano explained their hydraulic brake lever feel to be the result of deliberate engineering, talking to roadies. So it seems to have been a conscious decision. IMHO that was a big mistake, because it seems to me they just replicated a worse brake lever feel. I reckon they had to do this, because on their mechanical drive trains their drop bar brake levers also act as shift levers (another big fail IMHO, although this is evidently not true for TT bikes).

What issues are those (I’m not being argumentative, I am curious)? Supporting rotors of various sizes isn’t new, my previous hard tail had 180 mm/160 mm. My current and my next road bikes are 160 mm all around, though. Personally, I think 140 mm rotors are for the most part pointless. The weight savings are irrelevant, and they are better at stopping (the result of a larger mechanical advantage and being able to store and dissipate more heat).

I think you misconstrue my opinion as having solely advised against rim brakes, when my advice was much more subtle. I only advised getting a new rim brake frame. Like you admit, the war is over, not because someone won an argument over the internet, but because manufacturers have by and large moved on.

If you prefer/don’t mind rim brake bikes, I think there are some excellent deals to be had now. A few weeks back, someone asked whether to get a BMC SLR01 Teammachine with rim brakes for essentially half price. If you don’t mind rim brakes, that is a great deal. The “new” rim brake Teammachine uses the same frame, because BMC built their new frame as disc brake only. So you are losing exactly nothing. Shimano hasn’t released a new, 12-speed groupset either, so this bike was as good as the “new” rim brake team machine in every respect.

You can thank the UCI for that, which forbids aerodynamic devices. I grant you that disc brakes probably are never going to be better than “hidden” rim brakes, but then you pay for with often worse braking performance (even compared to other rim brakes). I think aerodynamic disadvantages could be mitigated to a large degree if the UCI opened up their rules and regulations to modern times.

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Actually, consumers have moved on…the switch to discs was primarily fueled by consumers. They were demanding it. For a number of years, suppliers tried both versions in their product lines and it was overwhelming which was preferred by consumers.

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I mean, you see a subset of bikes which, are by definition, broken. And then presumably you fix them? So after they’re fixed, the user has a good experience on discs. I absolutely despise the 100% of time I’m riding with carbon wheels on my rim brakes. Worst part of my tri bike, even in the dry.

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Thanks all for the comments and healthy discussion.

My current bike has carbon fiber wheels and although I do not love how they brake, I don’t mind.

I live in flat florida. The only time I do hills (like real hills) is when I go to race at clermont (central fl about 30 min from Disney). The rest of the time the bike will be at the trainer and once a week will be riding long on mostly flat roads.

If I get wheel brakes i could potentially get a disc rear wheel for races used in good condition for much less than a similar wheel but for disc brakes .

In the other hand, the canyon bike is slightly less expensive than trek, plus potentially without sales tax. That makes a good case that I could get a wheel later on with the Saves.

I really hate myself for taking myself into believing spending 6k bike instead of 7k is some kind of good thing…


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IME, they are a pain. I had XT disc brakes on a mountain bike that sent reverberations through the whole frame. In fairness, it was probably the frame’s fault. I had a Marin hardtail with these hair trigger disc brakes that were so loud that they were pretty obnoxious. Currently, I have a FS MTB with SRAM XXX and a gravel bike with Force 1 and I hate the DOT fluid required for those brakes. I’ve had various bleeding and rubbing issues on both bikes. So overall, big PITA in my experience.

Maybe Shimano road disc brakes with mineral oil fluid are way easier to deal with?

If you are doing triathlon and flying to events, my concern would be having to bleed after landing. I’ve read that the pressure changes when flying that mess with disc brakes. You may also have to take discs off wheels to prevent them from getting bent during travel.

If you can get a great deal on a rim brake bike right now, I’d go for it without hesitation. You’ll be able to find wheels and parts for years and years.

I’ve been thinking about a new road bike frame and I keep thinking that maybe I should go rim brake one more time. I see no downside. If I was riding in inclement weather all the time or descending in the alps frequently, I might go disc brake.

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You should do that, period. Not a big deal, especially with Centerlock wheels.

This is a myth or perception that just needs to die. Disc brakes give you superior braking, all the time. Not just in bad weather or descending, but every single time you touch the brakes. I live in pancake flat Chicago and I’m not going back to rim brakes, ever.

And if I ever get another TT bike, it will absolutely be discs…and I’m a pretty diehard aero nerd when it comes to my tri races.


How is it a myth to say what I’d do??? I said that if I needed a higher level of braking I’d go disc. You make it sound like you can’t stop for a stop sign with rim brakes.

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The myth / perception is that there is only improved braking in wet conditions or on long descents.

There is improved braking every time you touch your brakes…wet, dry, flat or descent.

And I never implied any such thing re: rim brakes…clearly rim brakes have worked fine for decades. But that doesn’t mean discs don’t provide superior performance. “Better” is always possible…and let’s face it, most brakes systems on TT bikes are at the bottom of the performance curve.

i did a thing…


That thing is a hunk of carbon.

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I like big bikes and i can not lie!


I take it you are not thinking about UCI TTs :wink: That’s some serious weapon :+1:

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