Rotor Size Article - Larger Rear Rotor?
- Thread starter djjohnr
- Start date
When I got into the whole weight thing I still managed to get sub 16kg on all dh parts, saint brakes, no xc or enduro shit 10 years ago and I still never had the idea of running a small rotor in the rear. Sorry but sometimes you go riding somewhere where the descent is long and I will never compromise on the brakes. Race fluid, good hoses, large rotors (203mm in the rear, 220 on the front for my dh bike).
I smoked a set of brakes coming down with my buddy Compton on a back line of cables at big bear....had little to no brakes coming in through the woods and rocks hotter than hell when it spit me out onto the rock chute I had to drag feet and lay it sideways at bottom right hand hook to keep from shooting off trail and down....used my camel back to pour water on rotors...after that I had to keep stopping and pouring water on em rotors were smoked.....we kept riding I had to watch speed gauge descents...replaced rotors and pads when we got back...thats pretty much when I decided weight of a rotor is non negotiable to upsize...
I had my brakes fail on me in Alpe D'Huez on the FR Nationals track. IT was a long straight and after it there was a turn. If you didnt make that turn there was a rather steep hill after it going down so the consequences were bad. So I had to lay my bike in that turn, jump over the bars and start running (and later tumbling since humans can't run down the hill at 30-40kph) . After that I don't care about the weight there.
That's what I farking hate with a DH/Enduro bike with a mainstream brake setup. When you ride the terrain where you are basically just fighting for survival, hanging on the glazed/fading brakes and unable to enjoy it because you are trying to clamp your fingers shut for all you are worth. What I mean by "mainstream brake setup" is that most of these have been severely lacking when you get into these situations. We've just dealt with it, but we can do better.
Someone tells me that the bike would be over-braked with 220/200 and I will show them the extended 45% grade.
Trans BC 2018 had one stage that dropped 1000m in less than 3km (3280' in 1.8 miles). Not crazy rough - but narrow and without catches on the turns so you really couldn't let the bike run away on you or you'd blow through a turn into the bushes.
I was running 203mm rotors on Hope V4s on a 27.5 bike, but a lot of others were using a lot less. I wish I had a Go Pro of my run because the track was littered with riders who's brakes had just given up in the conditions. I maintain that sometimes popular OEM brakes feel great or better than the more reliable brands in the carpark, but you can't compare them at all after even a short section of proper sustained heavy braking.
I wish PinkBike would have one reviewer that likes a lot of beer and is carrying some extra weight and get them to test the new brake releases on fall-line descents. I think a few products might lose some review stars under a Clydesdale.
I hear you. I pretty much ignore many of the M&M reviews nowadays since they tend to say nothing of value or consequence, and I personally couldn't put much stock in a review of something that includes either EXO or EXO+ in the spec list. Seems like they've slid into the spot left behind by RC.
I will say that odd German lot at Enduro MTB seem pretty on point on many things. Also that Seb guy PB got from Bikeradar seems to be pretty forward about product issues and IMHO has historically made observations and drawn conclusions that tend to reflect what hard chargers that abuse products experience with equipment.
Did I hear that right that he's running a larger rear rotor while running mullet? That's would make for a big difference in front/rear brake torque. A 220 rotor on a 27.5" wheel with 4 piston caliper sounds touchy to me. Lets see if he keeps this setup at a mud race.At 4:00min he starts talking about rotors. Seems like Troy and his team did some data collecting and came to the same conclusion. Interesting
Love the cooling teeth, dislike the spokes. They look inefficient/flexy.speaking of big rotors, cooling & such, these look rad:
Shoot I didn't even catch that...gonna be more power than just bigger rotor with less leverage on it...yeah slippery may get a bit too snappy on and off power...
Mullet with identical rotors already tames front down compared to rear..
The spoke design on a rotor needs to be shaped to compensate for the thermal expansion of the braking surface to prevent warping.
Yeah, but those spokes look more "lateral" than most. They also have to resist bending from being hit and be easy to straighten.
After a mostly wet trip to Whistler running 200F/220R I'm sold; that setup resulted in easier even braking control on wet rocks and I never felt like I needed a 220 up front. I felt the same way in the dry at Northstar.
I just did a super wet trip to Whistler 3 weeks ago on my 170 29'er bike with 220F/200R. At no point did I think "I need less bite up front and more in the rear", especially on the Blackcomb trails in the mud. I did, however, rent a couple of DH bikes that were 29'ers with 200F/R, and immediately wanted my 220F back.
I'm all for fiddlefucking with things in the name of experimenting and learning, but between Satan's Torx drive fasteners and adapter fuckery, I don't envision a scenario in which I'll be putting in the effort to try out a larger rear. Especially since it's contrary to every other vehicle development cycle on earth (dirt bike, street bike, car, truck, etc).
Which one of those vehicles is predominantly raced down steep hills and low grip surfaces with no engine (braking)?
If you're heavy and a rear brake dragger it probably makes tons of sense so I tend to just live and let live on this one.
If you're heavy and a rear brake dragger it probably makes tons of sense so I tend to just live and let live on this one.
To be fair, none of those applications tend to involve having the rear brake dragged nearly as much as in MTB.
FWIW, I just run the same size F&R so I don't need to carry too many spares.
I've actually considered going 220F/R just for the spare parts reason.
And watch one of the outdoor MX races or a hard enduro race if you want to see the most rear-brake draggy action of any vehicle anywhere. Those guys literally stand on the rear brake pedal coming down hills.
So?
The MX bikes will have engine braking. The hard enduro bikes will have barely any being mostly two-strokes.
The MX bikes will have engine braking. The hard enduro bikes will have barely any being mostly two-strokes.
This is exactly where I was on this.
Really?
You're complaining because some mountainbikers might want to use a 220mm rear rotor for a more powerful brake and less hand effort/fatigue and less chance of fade because you've seen MX bikes using their rear brakes with both foot operated and engine braking.
Surely you've noticed the size and thickness of MX bikes rear rotor? not to mention their massively larger calipers and pads
I think I preferred shite I read here last week from RMs golf experts
Obviously you'd be the one to know if it's worth experimenting for yourself. I use a torx bit on an impact driver, so swapping rotors takes about 30 seconds, and I have plenty of rotors.
It’s not that I’m against a bigger rear brake rotor, but in every application that does this, like cars, etc, the rear caliper is less powerful so you don’t lock the rear all over the place. It’s the heat capacity that we are after IMO and larger rotor is one way to do it, but increasing rear power may not be necessary or wanted here.
Even with a smaller rear rotor and smaller caliper, the name of the game in every other vehicle application is the modulation and sensitivity of the rear brake(s) because there's so little weight back there under braking, in an effort to keep from locking up. Cars go with smaller rotors and calipers, motorcycles with foot brakes try to reduce leverage and increase feel as much as they can with the boot/lever, etc.
Increasing your likelihood to lock the rear and depriving the front of proportional power is bassackwards. It speaks to some really weird braking technique that's more of a rider problem if there were some perceived benefit there.
Increasing your likelihood to lock the rear and depriving the front of proportional power is bassackwards. It speaks to some really weird braking technique that's more of a rider problem if there were some perceived benefit there.
Plus in a car, you can't control the front and rear brakes separately, or shift your weight to impact the front to rear grip bias in any meaningful way. That comparison is irrelevant.
I've done a bunch of experimenting and one size bigger rotor up front (assuming equal wheel size) works well for me, just from a control and modulation perspective. But I'm all for running big rotors in general, and have a 223f/203r combon on my personal bikes when I'm not testing other stuff.
I've done a bunch of experimenting and one size bigger rotor up front (assuming equal wheel size) works well for me, just from a control and modulation perspective. But I'm all for running big rotors in general, and have a 223f/203r combon on my personal bikes when I'm not testing other stuff.
and yet there are better riders than you or I out there who don't even bother to run a front brake at all
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The weight shift under braking loads in a car is very meaningful. When the rear brakes can lock, the weight on them plummets, down from ~40% of the vehicle mass.
Additionally, most street cars and trucks have proportioning valves going to the rear brake lines to address this exact issue. It's the ability to fine tune that power delivery to the rear to keep it from locking and optimize deceleration.
Side note - why does this business of 200/203mm and 220/223mm rotors still exist? Wtf was the point of this originally? I seem to have forgotten. Perhaps deliberately.
Obviously, yes. My point was that you can't shift the weight of the bag of meat piloting the thing to counteract that in a car in the way you can on a bike.