I have a Quintana Roo PRFour and will be upgrading my wheels to some Roval CL50’s from the stock rs170’s.
Since I will be upgrading my wheels I can also upgrade my rotor size. Right now I have 140 mm on front and back. I am going to keep the rear at 140 but am questioning about upgrading the front to 160 mm.
Is that a worthwhile upgrade or should I just keep it consistent at 140 mm. I know I will have to get an caliper adapter if I do 160 but would the extra braking performance (less heat buildup for same stopping power) be worth the hassle.
After 1 season of riding in the flat midwest, I haven’t noticed any issues with the 140 mm as long as I have the brakes set properly. I tend to sign up for more tri’s in hilly areas which is why I am considering the 160 mm (madison70.3 and full lake placid this year for example).
Suggestions on rotors would be nice, so far the 105 level rotors I currently have seem to work well.
What do you weigh? I rode 140mm front and back in a fairly hilly area at 170lbs + 25lbs bike weight. Never had an issue but there were lots of people recommending against someone of my size riding 140. I imagine you’ll probably have zero issues staying with 140mm, however the only downside is probably a tiny, tiny aero penalty.
Are you going to ride hillier areas in the next couple years? If not, I wouldn’t bother (disc brakes in general are overkill for a tri bike in the midwest cornfields).
At 170lbs, I definitely prefer 160 when I’m in the mountains though
I weigh 170 lbs and have since I finished college. I have always been skinny and dont ever think I will gain too much weight but as I get older I cant imagine Ill lose weight and weigh <160 lbs. Maybe if anything Ill get out of triathlon for a couple years and gain weight but I wont let myself get too heavy.
Researched this myself as I wanted to go from 160 to 140mm when I was upgrading my rotors due to being able to get them off a buddy cheap but after a ton of research the consensus was that 99% of the time you will be good with 140 however if there is one time when you use them too much on a descent, its not a matter of reduced braking power but you will have zero brakes at all if they overheat. Considering some of these courses you can hit 55mph+ and may have to slam on the brakes for a number of reasons it doesn’t seem like a risk worth taking for the negligible aero penalty (Probably like .25w?) and 10g. My P5 came stock with 160 as do most tri bikes so if given the choice I would upgrade your front to a 160.
Researched this myself as I wanted to go from 160 to 140mm when I was upgrading my rotors due to being able to get them off a buddy cheap but after a ton of research the consensus was that 99% of the time you will be good with 140 however if there is one time when you use them too much on a descent, its not a matter of reduced braking power but you will have zero brakes at all if they overheat. Considering some of these courses you can hit 55mph+ and may have to slam on the brakes for a number of reasons it doesn’t seem like a risk worth taking for the negligible aero penalty (Probably like .25w?) and 10g. My P5 came stock with 160 as do most tri bikes so if given the choice I would upgrade your front to a 160.
As far as I’m aware, that type of braking isn’t the concern. The bigger problem is constantly riding the brakes on a descent. Short bursts of hard braking won’t be a problem on any type of brake.
Researched this myself as I wanted to go from 160 to 140mm when I was upgrading my rotors due to being able to get them off a buddy cheap but after a ton of research the consensus was that 99% of the time you will be good with 140 however if there is one time when you use them too much on a descent, its not a matter of reduced braking power but you will have zero brakes at all if they overheat. Considering some of these courses you can hit 55mph+ and may have to slam on the brakes for a number of reasons it doesn’t seem like a risk worth taking for the negligible aero penalty (Probably like .25w?) and 10g. My P5 came stock with 160 as do most tri bikes so if given the choice I would upgrade your front to a 160.
As far as I’m aware, that type of braking isn’t the concern. The bigger problem is constantly riding the brakes on a descent. Short bursts of hard braking won’t be a problem on any type of brake.
100%. I didn’t really explain it this way but I am more thinking about if you are going down say the 30mile descent at IM St.G, depending on your comfort level you may not want to go 55mph around tons of rider so you may be hitting your brakes here and there heating them up and then if there is a moment you really need them it might be a bit much for them. I could be still wrong but thats what I found online.
Ah okay yeah that makes more sense. I would hope people would be aware of the “air brake” method and just sit up super high but that’s probably asking a bit too much.
I fluctuate between 165-175 lbs and ride the same bike for road, cross and gravel. I went from 160s to 140s and just didn’t like the feel of the 140s when on longer road and gravel descents and went back to 160s. I do have some long descents on both road and gravel on my staple rides. For cross-type braking the 140s were just fine though.
If you are riding Shimano flat mount disc brakes, going from 140 to 160 is simple flip of the brake mounting adapter. I like the feel of 160 regardless if I am riding a lot of descents.
Thanks guys. I think I am going to go with the 160 mm option. Now to decide what type of rotor.
A smart choice. For a med weight rider like you on mostly flat terrain, for 99% of the time, 140mm rotors on the front will likely be fine. But the problem is that for that other 1% of the time (on a road/tri bike with a lot of potential energy), not only will they not be fine, undersized disc brake rotors could be dangerous or deadly. Not an exaggeration.
Yes thats exactly what I did. It took me a second to figure that out when I was searching for a 160 mm adapter to only realize the 140/160 are the same. Good to know they designed that correctly and its a simple fix.
Not that I am concerned about it but I do not think their should really be any aero penalties. 20g of extra weight that close to the center of the wheel wont be an issue either, especially since I will be saving 1.5 lbs when my new wheels arrive.
Wanted to bump this thread, got my first disc brake road bike and want to upgrade the rotors and not sure what size to go with. I’m 140 lbs, ride in a hilly but not mountainous area. Bike came with 160 front 140 rear but I like the idea of 140 front and rear. At my weight I feel the 160 may be overkill, I dont do lots of heavy prolonged braking, and frankly I don’t like the look of mismatched rotor size on the bike. Am I nuts? I want to get ice tech shimanos…the internet says that helps a lot with the overheating that 140s are subject to.
You’d have to check if your bike can even take a 140mm front… my road bike is 160 front/140 rear, and there is no adaptor on the front. That’s just how the bike was designed (flat-mount to the fork)
At your weight you’d be fine on 140s, although you might notice slightly decreased braking performance. But you shouldn’t have any issues overheating the rotors given how light you are.
The one thing I’d say is why go through the hassle of swapping it? Just for the looks? On the chance you ever travel with the bike to somewhere with huge mountain descents, I’d probably just stick with the reliability of the 160. At your weight you’d have a really tough time overheating that thing!
Thank you, that’s very helpful. It’s a slightly used bike, and while the rotors are in decent looking shape, I do want to get “fresh” ones for my own peace of mind that they’re not overworn or anything, and while I’m at it I can greatly improve the look of the bike lol. That, and my thought that 160 is overkill for my weight.
Makes sense, if you are going new anyways just go for it. It’s also a lot easier since you can always buy your rotors in pairs now (I made that mistake before…I now have an excess of 160 rotors).