What size rotors do you recommend?

Discuss light weight issues concerning road bikes & parts.
Nikoras
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by Nikoras

If you have hilly rides I highly recommend 160's. Cooked the 140s I had previously.

joejack951
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by joejack951

Nikoras wrote:
Sun Dec 08, 2019 7:48 pm
If you have hilly rides I highly recommend 160's. Cooked the 140s I had previously.
It’s hard to not assume that you are way over-using your rear brake if you are ‘cooking’ a rear rotor on downhills. The front brake is far more effective at slowing you down than the rear. Perhaps if you used it more you wouldn’t be destroying rear rotors so easily? Or is there some other factor I’m not considering that has you heavily on the rear brake? This is the road forum, right?

by Weenie


TobinHatesYou
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by TobinHatesYou

joejack951 wrote:
Mon Dec 09, 2019 12:07 am
Nikoras wrote:
Sun Dec 08, 2019 7:48 pm
If you have hilly rides I highly recommend 160's. Cooked the 140s I had previously.
It’s hard to not assume that you are way over-using your rear brake if you are ‘cooking’ a rear rotor on downhills. The front brake is far more effective at slowing you down than the rear. Perhaps if you used it more you wouldn’t be destroying rear rotors so easily? Or is there some other factor I’m not considering that has you heavily on the rear brake? This is the road forum, right?

I guess I'll use my example.

I live on a hill that is 15% average. It's residential. I don't go bombing down the road because there's the risk of cars pulling out of driveways, so I tend to brake equally front rear for a bit, then let go and build up speed where there's no driveways, and sometimes alternate between front/rear bias toward the bottom when I know the rotors/pads are hot. 140mm was barely cutting it, and worse, my pads weren't making complete contact on the rotor (no, the adapter was not attached.) I never got fade, but I also never got the amount of brake effectiveness I was used to with 160mm rotors.

The difference between 140mm and 160mm rotors is maybe 25g including the adapter. I'll take the very noticeable improvement in braking over that weight savings.

hannawald
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by hannawald

I use 160/140 with my 82kgs. With 160 on rear i was able to lock my rear wheel too easily so i needed to be quite careful..

TobinHatesYou
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by TobinHatesYou

hannawald wrote:
Mon Dec 09, 2019 9:17 am
I use 160/140 with my 82kgs. With 160 on rear i was able to lock my rear wheel too easily so i needed to be quite careful..

You can always play with contact point adjustment / free stroke. I find that 160s give me way more feathering/trail braking feel. And of course anyone hamfisted enough can lock-up any brake-type. That doesn't mean a brake has too much power...it just means you need to adjust yourself or adjust your brakes to your liking.

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Alexbn921
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by Alexbn921

I was extremely disappointed when I learned that flat mount brakes have a max rotor size of 160. I wanted a 180 up front for the extra power, but have been happy with my 160 setup. I don’t think I would want to down size the rear to 140 even if it would give better balance with the available traction during threshold braking.
Rear rotor size is dependent on braking style and if you like to drag the rear.

mattsurf
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by mattsurf

I weigh 157lbs, live in Switzerland, and love riding mountains. I have 160F/140R XTR M9000 post mount on my Gravel bike (due to tight clearance on frame) and 160F&R 8150 on my normal road bike. The XTR calipers are both lighter and better than the 8150 calipers. As far as I can see, there is no benefit from running 160 on the rear, I would also question whether it is necessary on the front as well

joejack951
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by joejack951

TobinHatesYou wrote:
Mon Dec 09, 2019 12:45 am
I guess I'll use my example.

I live on a hill that is 15% average. It's residential. I don't go bombing down the road because there's the risk of cars pulling out of driveways, so I tend to brake equally front rear for a bit, then let go and build up speed where there's no driveways, and sometimes alternate between front/rear bias toward the bottom when I know the rotors/pads are hot. 140mm was barely cutting it, and worse, my pads weren't making complete contact on the rotor (no, the adapter was not attached.) I never got fade, but I also never got the amount of brake effectiveness I was used to with 160mm rotors.

The difference between 140mm and 160mm rotors is maybe 25g including the adapter. I'll take the very noticeable improvement in braking over that weight savings.
I think your point about 'I also never got the amount of brake effectiveness I was used to with 160mm rotors' explains why we differ. You've experienced and got used to a 160mm rear rotor on the road so the 140 feels weak. I got used to having no rear rotor so even having a 140mm rear seems like a lot.

I still think anyone 'cooking' a 140mm rear rotor on the road needs to evaluate how they brake.
Last edited by joejack951 on Thu Dec 12, 2019 4:02 pm, edited 1 time in total.

ruklaw
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by ruklaw

Alexbn921 wrote:
Mon Dec 09, 2019 4:50 pm
I was extremely disappointed when I learned that flat mount brakes have a max rotor size of 160. I wanted a 180 up front for the extra power, but have been happy with my 160 setup. I don’t think I would want to down size the rear to 140 even if it would give better balance with the available traction during threshold braking.
Rear rotor size is dependent on braking style and if you like to drag the rear.
It is possible to accomplish this (180mm rotor on flat mount fork), but it'll be ugly as hell - use a 160mm flat mount to post mount adapter, then a +20mm post to post mount adapter on that, then a post mount caliper.

It is also likely to invalidate your warranty, as more braking force means more stress on the fork.

But yeah, as the rest of your post indicates, 160mm front is fine for even very heavy riders - I should know as I am one - although I do run ice tech rotors and finned brake pads to be on the safe side.

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nycebo
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by nycebo

To everyone who keeps bringing up the 25g difference as though it's not that big a deal, do remember that you're in the Weight Weenies forum.

Secondly, at 80kg in the mountains of Italy, 160f/140r felt very strong for extended 10 mile descents at speed. However, if one is pushing 85kg or more, then 160 all the way around is very reasonable. Anyone lighter than me has flexibility to do whatever they want that feels comfortable and confident.

Lastly, from years of motorcycling and cycling, one should never ride the brakes for extended periods of time. Brake into the corner or intersection, and then release. Riding the brakes for minutes at a time is a sure fire way to cook the fluid and ruin rotors.

Ride safe gents.

SandwichNP
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Joined: Sat Nov 16, 2019 3:22 pm

by SandwichNP

207lb and on 160/140, no problems with fading nor power. Those rotors should be plenty for you. I'm a bit disappointed that my new build kit has dual 160s, as I just don't think they're necessary on such a light bike used for pretty normal riding conditions. You'll overwhelm your tire contact patch before you end up needing more rotor. I'd save the weight where possible.

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mortirolo
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by mortirolo

I highly recommend 700mm disks made by Campagnolo and lightweight . That's solution was good for winners of Giro and Tour this year.
Marco Pantani - Momenti Di Gloria

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Alexbn921
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by Alexbn921

mortirolo wrote:
Wed Dec 11, 2019 7:18 pm
I highly recommend 700mm disks made by Campagnolo and lightweight . That's solution was good for winners of Giro and Tour this year.
I believe you mean 622mm, but since you can't read it probably doesn't matter.

Nikoras
Posts: 93
Joined: Thu Sep 26, 2019 1:59 am

by Nikoras

joejack951 wrote:
Mon Dec 09, 2019 5:04 pm
TobinHatesYou wrote:
Mon Dec 09, 2019 12:45 am
I guess I'll use my example.

I live on a hill that is 15% average. It's residential. I don't go bombing down the road because there's the risk of cars pulling out of driveways, so I tend to brake equally front rear for a bit, then let go and build up speed where there's no driveways, and sometimes alternate between front/rear bias toward the bottom when I know the rotors/pads are hot. 140mm was barely cutting it, and worse, my pads weren't making complete contact on the rotor (no, the adapter was not attached.) I never got fade, but I also never got the amount of brake effectiveness I was used to with 160mm rotors.

The difference between 140mm and 160mm rotors is maybe 25g including the adapter. I'll take the very noticeable improvement in braking over that weight savings.
I think your point about 'I also never got the amount of brake effectiveness I was used to with 160mm rotors' explains why we differ. You've experienced and got used to a 160mm rear rotor on the road so the 140 feels weak. I got used to having no rear rotor so even having a 140mm rear seems like a lot.

I still anyone 'cooking' a 140mm rear rotor on the road needs to evaluate how they brake.
Nah, if you're riding unfamiliar roads with big descents and poor visibility it will happen. No need to be a dick about it.

joejack951
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by joejack951

Nikoras wrote:
Thu Dec 12, 2019 5:02 am
joejack951 wrote:
Mon Dec 09, 2019 5:04 pm
I still think anyone 'cooking' a 140mm rear rotor on the road needs to evaluate how they brake.
Nah, if you're riding unfamiliar roads with big descents and poor visibility it will happen. No need to be a dick about it.
I've talked with quite a few 'experienced' cyclists who think the rear brake is the best one to use to stop quickly. I'm not saying you're one of them but in the past it has benefited the discussion to mention that the front brake is the more effective one to use. If you already know this, my apologies for coming off like a dick. I should work harder at re-reading my post to avoid sounding dick-ish.

by Weenie


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