What size rotors do you recommend?

Discuss light weight issues concerning road bikes & parts.
dricked
Posts: 190
Joined: Tue Jan 09, 2018 1:57 pm

by dricked

I ride 140mm rotors at 80kg. The terrain is rolling hills with no technical decents (unfortunately) so the rotors don’t really get a workout. A few hard stops after 60-70km/h hills and stop signs and they work just fine.

Obviously terrain/rider weight dictate rotor size.

by Weenie


icantaffordcycling
Posts: 956
Joined: Wed Jan 09, 2019 5:03 am

by icantaffordcycling

Image
From VeloNews

Does anyone know if these are a Shimano part or a custom part? I am guessing that if they were a Shimano part more teams would be using them but it looks like it just replaces the stock flat-mount adaptor. Looking at the 360 view on the Merida site, it doesn't look like it comes with the reacto or sulctura.

Nefarious86
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by Nefarious86

They would be specific to the frame.

As for rotors I find at 180lb 160/140 gives a nice balanced feel without having an easily overpowered rear brake.

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TobinHatesYou
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Joined: Mon Jul 24, 2017 12:02 pm

by TobinHatesYou

Merida has been using those fins for at least 2 years.

One thing that was pointed out to me last weekend by one of icantaffordcycling’s teammates is how fat the carrier arms are on the Shimano DA rotors compared to those of the SRAM Centerline XRs.

spdntrxi
Posts: 3714
Joined: Sat Jul 20, 2013 6:11 pm

by spdntrxi

icantaffordcycling wrote:
Thu Jan 23, 2020 7:41 pm
Image
From VeloNews

Does anyone know if these are a Shimano part or a custom part? I am guessing that if they were a Shimano part more teams would be using them but it looks like it just replaces the stock flat-mount adaptor. Looking at the 360 view on the Merida site, it doesn't look like it comes with the reacto or sulctura.
looks more like a fairing to me... but I guess if you dont call it a fairing it's more likely to approved by the UCI.

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Dan Gerous
Posts: 1587
Joined: Sun Aug 12, 2007 6:28 pm

by Dan Gerous

I'm pretty sure those are not fairings or to disrupt air on the Meridas, they're heatsinks. If the front caliper gets hot, heat transfers to the heatsink/mount, the bigger the heatsink and the more surface area it has, the more it can help release the heat, and having air flow on and through it helps this, how much though, no idea...

TobinHatesYou
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Joined: Mon Jul 24, 2017 12:02 pm

by TobinHatesYou

Also the NDS chainstay also has fins in a vertical orientation. They’re obviously heat sinks, come on.

TheRich
Posts: 635
Joined: Tue Jan 01, 2019 1:36 am

by TheRich

Looks like woo to me.

I finally broke down and went 160/160, although most of the reason is because it's a dual purpose road/gravel bike, it does make spares easier to deal with.

PoorInRichfield
Posts: 120
Joined: Sun May 17, 2020 9:38 pm

by PoorInRichfield

Can anyone confirm the Shimano recommendation stated in this relatively recent Road.cc article, "Everything you need to know about disc brakes - read our definitive guide"?
This goes against the trend for smaller rotors, which is largely the result of Shimano recommending 140mm rotors for all but the largest cyclists.
Where does one find this "Shimano recommendation"? In doing an image search, it's easy to find photos of pro racers using 140mm rotors front and rear... but then again, they're not being paid to stop :D

Image

(Just noticed all the blood... maybe he should've used 160mm rotors? :P )

wfmahaoran
Posts: 6
Joined: Sun May 20, 2018 8:28 pm

by wfmahaoran

I'm 63kg and do a lot long climb round my place, 140mm f/r is definitely enough for me

PoorInRichfield
Posts: 120
Joined: Sun May 17, 2020 9:38 pm

by PoorInRichfield

In researching this topic, I've noticed that quite a few of the light weight bikes that were offered just 2 years ago, like the Giant TCR Advanced Pro 0, came with 140mm front and rear. However, the most recent models have 160mm front / 140mm rear.

I think a challenge that bicycle manufacturer has is that they don't know who's going to ride the bike. If a 65kg rider buys a bike with front and rear 140mm brakes, there's no issue. But if a 105kg rider buys the same bike, now there's potentially a problem. Equipping bikes with 160mm front and rear will work for both riders and reduce the manufacturer's liability, even if the brakes are totally overkill for the 65kg rider.

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^^^ "Look ma, small discs!" :P

PoorInRichfield
Posts: 120
Joined: Sun May 17, 2020 9:38 pm

by PoorInRichfield

(Talking to myself I think...)

Looks like most of the pro bikes from this year were doing the "biggy-smalls" thing... 160mm up frond and 140mm in back. The following article has 4 parts showing bikes from various pro teams, with very few doing 160/160 and none doing 140/140 that I could find:

https://cyclingtips.com/2020/01/pro-bik ... part-four/

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