Video: Syndicate Pit Gibberish - Why Would You Run a Smaller Rear Rotor?

 I like big rotors and I can not lie

 Personally. I like the smaller rear because I dont want to break traction on the rear if possible. When I squeeze the levers equally, on a downhill, my front wheel has more weight in it and so less likely to skid with that force. The rear with less weight will skid with less force. So a smaller rotary equalizes the braking. Plus the steeper the terrain the more you rely on the front brake anyway. Try skidding to a stop in steep terrain it just doesnt work. That's me anyway. But I've run 200/180 and 180/180 and If your brakes are strong enough you'll be fine.

Maybe it's a cop out for when they spec shit brakes? They aren't downsizing the rear but up sizing the front?

 I believe the word they are looking for is "Modulation". Something Shimano brake owners have not seen in a long time...

 I tacoed my rear wheel once and ended up doing a 15 mile DH with about 25% of my rear brake functional (rim brakes), and it wasn't at all that bad. That day I learned how much more work the front brake does in comparison to the rear.

 Why wouldn't you?
Honestly, if you're pointed downhill 80% of your weight will be on the front contact patch, meaning the rear will skid out with very little input.
Same reason some motorcycles have dual front discs, but a smaller rear one.

 I wanted a big disc on the back for instantaneous reaction, not more power, just a quicker response. I did a lot of back wheel steering. But I also smashed a few rotors on rocks, so sometimes I would go smaller if the track needed/allowed for it.

 I think they do it because it takes effort to engineer rotor clearance on the back of the bike. Realistically, it is probably difficult for a bike with 6" or less travel to take advantage of a 203 in the back, due to weight and traction shifting forward under braking.

That said big rotors all the way!

 Same reasons as with motorcyles and cars - weight transfer and forces needed to brake before traction breaks dictate the size of the brakes. I have never seen a car with the same size brakes front and rear, even on a front wheel drive car where engine braking wouldn't add to rear braking power. IMO smaller rotors cause less mass (especially unsprung mass), less rotational inertia, and more clearance for less impacts with objects - rocks, tree stumps, etc.

That being said, 203 rotors in back would perform better, like anything else, it's a trade-off.

 I run the largest rotors my bike will fit, so 200 front 200 rear. I agree there is no point in running smaller rotors unless you're trying to save weight, and the weight difference is pretty minuscule. Assuming that you can exert enough force on the brakes to lock up the rear wheel with the smaller rotors, which should be a given with modern hydro brakes, the only difference is the amount of force you have to exert at the lever with your fingers. Smaller rotor, higher force pulling on the brake lever.

 Weight transfer.

 I run one pad on the rear.

 Front to Stop, rear to slow down.

Combination of the two. Usually more front than back in any ratio.

Experimenting with contrast exercises will reinforce the first statement.

For the same amount of lever pressure I get a bit more front than back. I would use the same size on a DH bike due to dragging the rear more often (durability and heat dissipation)

 the biggest brakes you can possibly get all the time every time ...........next

 I started out with a V-brakes front and rear. After too many crashes I upgraded my front brake do a hydraulic disc brake but stuck with the V-brake in the rear simply because my frame wouldn't accept a disc brake. So that's how my riding developed over the years. Relying on front brake and front suspension and basically ignoring the rear. Even though after years I got both front and rear disc brakes (190mm front, 160mm in the rear) I never really started using the rear brake much. I had a few rides with 160mm in the front. That brake rotor turned blue within a single ride. I'm this is riding down overgrown landfills turned recreation area type trails in The Netherlands! Steep, twisty maybe, but definitely short. After that, I never have ridden smaller than 180mm in the front. Actually it is since May last year that I got brake and fork without IS brake tabs that I had to move from 190/140 (f/r) to 180/160. But I never had trouble with that 140mm in the rear.

Yes of course you can't apply the front brake in corners. It just never made me use the rear brake instead. I just learned the hard way to brake hard before the corner if I need to and then just let it roll. If I want more oversteer I shift more weight to the front wheel and at some point the rear wheel loses traction. That slows me down too. Now of course despite what Jason says, I'm probably still slower than him .

 Larger rotor brakes are snappy. snappy brakes keep hands fresh.fresh hands and nice to have. would like to try some of the 220 rotors on the 27.5 keep it extra snappy

 Personally I like hard biting 200mm rotors, however I only use a little finesse to control them. For me, this keeps arm pump down and lets my old ass finish a big run. I kind of see Marshy's motorbike analogy, but seems like it only applies to downhill tech terrain on a dirtbike. On open race tracks, you don't have time for engine braking to make a difference.

 Those that ride very steep sustained terrain will appreciate a large rear rotor.

 My bike came with 180s on the rear but I now run 203 front and back (later on I also changed from double pot XTs to Zees, and that was a transformative upgrade to my bike). I still go through rear brake pads and rotors about twice as quickly as the front.

I weigh a lot and often ride in steep terrain. I'm also probably a hack rider.

Also I find it much easier to modulate a more powerful brake.

 And here I am with a 160 on the rear for the reason of not having a large rotor that may hit stuff and bend when playing on trials stuff and plus helps keep me from skidding but on long DH runs it turns blue.

 Just bought myself a 180 rotor today, so I know why people do so - or at least, why I did. The only reason was, that I found it incredibly cheap, and paid for 180 rotor 1/3 of what I would have to pay for exactly the same rotor with 203 mm diameter.

And I regret it already - although the difference was like 3x, it was still less than 20 GBP.

 Fabien Barel went down to 160 rotors for his world champ bike. Tried it and it worked really well...less chance to hit something also. I think better riders use the front brake more often...when changing to 29er wheels braking changed noticeable - more grip on one hand but also feeling to fast entering some turns/sections. 200/180 is not an extreme take, you should try and switch back to 200/200 if it doesn't work for you...

 Love the comments up top, Sir mix-lot would be proud.. Most bike brakes are crap, if they really wanted to make a brake that is durable and reliable it’s easy.. but would add a tiny bit of weight therefore we are left with squealing crap that goes thru pads like a kid thru candy! That’s what they want apparently? We have only been using disc brakes since the mid 90’s what do you expect? Simple brake problems fixed in your lifetime? Haha. Bigger pads with the proper compounds to run thicker rotors and more fluid capacity and bam...problems mostly solved. But why do that? when we can be bleeding brakes after every hard use and buying brake pads like crazy and rotors that squeal like a pig. It’s all about the brake companies making money!

 ive never understood this trend, my only guess as to why most bikes come with it is because a lot of trail and enduro bikes only have room for a 180mm max rotor, which is kind of annoying. my cotic bfe only has room for a 160mm max rotor in the back which is really annoying. heard some bikeshop bs that its for better modulating or something like that, if I had the choice too its 203 front and rear with the most powerful brakes I can get, brakes are not something to worry about weight or cheap out on, its the most important safety feature on your bike,

 If you want to under power the back brake (smaller rotor) so that it doesn't lock up when you pull both brake levers evenly then you should learn to modulate your brakes independently. A bigger rotor has more modulation and most of the time your aren't modulating the front and rear brakes evenly. The bigger the better as long as it fits and you don't care about the extra weight.

 only reason I can think of having bigger brakes on the front is when you go onto the brakes, the weight of the rider transfers forward therefore needing more surface area to displace the heat, similar to cheaper car (including my own) having disks on the front and drums at the back as most of the braking force and heat is generated at the front.

 Okay, so I've read through most of the comments and a lot of folks have this all wrong. I know that is a bold statement but I have the credentials to speak on the topic; for many years I was a successful motorcycle road racer. You can't race a motorcycle well without mastering the art of braking and understanding how they most effectively work.

On motorcycle road race type bikes they use two very large front brake disks and a single small rear disk. Right? But the application reasoning doesn't apply to enduro/downhill mtb. Why? When racing a motorcycle, coming down a straight full throttle you need to dump speed as deep down the straight as possible before being off the brakes to bend the bike into the corner, and you better be full off the front if you bang the bike over into a full lean, lest you tuck the front and low-slide off into the dirt. Race tracks have actual markers painted on the edge of the track to help you gage just when to let off the gas and go full brake, and they have these because you can't visually gage it otherwise (if you are competitive). And if you aren't braking hard enough to float the rear wheel most turns, well, you are going to be passed by everyone. All this braking is accomplished by the front brakes, and they get so hot they glow, necessitating ss braided brake lines to keep the hoses from going mush. If you apply rear brake while the rear wheel is that light or temporarily off the pavement, it will skip all over the place, which is bad. As for engine braking... One of the biggest differences between an expert and a novice road racer is the ability to softly downshift at high revs while pulling on the front brake hard (it is the throttle hand also), blipping the throttle perfectly to match engine rpm each downshift while maintaining a constant hard pull on the brake lever; engine braking is a subtle rather than overtly brutal affair, only somewhat successful at slowing the bike in a measurable way. It is an art. Regardless, the only time you use a rear brake on the track is to drag it in the corner if in too hot to tighten the turn without chopping throttle, which when asking all there is of the tires on edge can upset the suspension otherwise, putting you into the dirt. Oh, and there is one other time a road racer uses the rear; if you run off the track. Grass is slick and front braking in grass will put you on your head when the front tucks under. Been there done that, and it ends ugly. So that all being said...

Another mis-perception I'm seeing cultivated is that a larger diameter rear rotor equates to more braking power. It does not, at least before heat dissipation becomes a factor. The braking power of a brake to disk interface is the size of the contact point. A SRAM Code brake will have the same contact point surface area regardless of disc diameter and therefore the same power regardless. That's just simple physics.

Why use a larger rotor in the rear? Heat dissipation. Plain and simple. As a bike mechanic I can assure that even the best riders go through rear pads faster than front; doubly so. And if you live in an area with long technical descents and have felt the rear go to mush, a larger rear disc will be a key upgrade. I think that is the point the video author is trying to make. As for braking power though, otherwise... There is no point. And you will feel no difference (well maybe mentally). But as for the need to dissipate heat on long downhills look at EWS bikes. Most are running at least 200 mm front and rear. And I would argue that novice riders riding similar trails are actually heating their butt brakes far more than a top pro. We use the fronts as much as we can, but it is the rear doing the constant heavy lifting down the tech stuff. We use the front with more precision. BAM!

 What about brake jack? Dose it make a difference on braking bumps?

 I dont see any disadvantage of running a bigger rotor front and back aside from weight, the front brake is used less but has alot more stress put on it when it is used than the rear which equals more heat I prefer two 200mm because i dont care a whole lot about weight but if i had one 180mm and one 200mm i would definitley put the 180 on the rear

 To flip the argument around, why are bikes spec'ed with small front rotors?

Many 'enduro' bikes come with f&r 180mm rotors. 180 is fine for most riders in the rear as there is only so much grip to be had with a rear brake, but ride down a sustained rock slab for instance and it's nice to have the extra bite and heat management from a bigger rotor up front. 200 / 203 for both is fine but it means upgrading two sets of rotors / adapters so I normally just go with upgrading the front rotor.

 Frame clearance, ground clearance, less weight, less locking up, less need for high braking forces. Pick one or all.

 Even though I brake equally with front an rear at the lever... Front an rear brakes have different jobs in that the majority of slowing down is done by the front brake as the weight is behind it, the rear controlls the balance an handelling of the bike under under braking as the wieght is in front of it

Think of it as the difference in front an rear wheel drive on a car

Ive recently down sized all my rotors to save around 5-6oz on all my bike but the DH rig. That will allways be 200 F & R because i'm a coward Big Grin

 At 43 years old with a life of pulling brake lever (most of it from the days of rim brakes) I will always take the biggest and strongest brakes I can have. That way its as easy on my hands as possible as I get deeper into a long run. It does take skill to use a strong brake properly.

 I have ridden with old crappy brakes from back in canti days, to v brakes, to disc brakes... This made me laugh because I just slapped some 203's on my bike front and rear, which was an sb6 yeti with 180 front and rear....

I rode a devinci at whistler, true downhill rig for the first time and was like 'holy cow'... this thing brakes so easily.... so why not put them on my yeti. I have to say, they are touchy, super touchy if you just XC ride, but I like it... I guess I"m a bad rider, but I like to slide like I"m 11 years old and have a good time, so on/off works for me.

Anything is better than canti rim brakes

 203 front ,183 back ,for my capabilities it’s more then enough cause for the speeds I get and the ability I have i need more the front brake in that steep hills than someone that can make cornering look easy on steep stuff,but yes I see the point in the real pros using a bigger rotor on the back and with that 29’s why the hell not ?and how about twin rotors

 In motor industry it is made like that bc rear is generating just about 30% of braking force so putting brakes from front at the rear wouldnt change a lot. At the bike it works the same way. Ofc you can compensate it with weight distribution but still the back will loose the grip easier. Static friction force(blocked wheel) is smaller than dynamic force (rotating wheel) so you will stop later with blocked wheels than with rotating wheels.
Less force at the back give less chance to block wheel. It is just physic during braking you and your bike, car whatever os trying to rotate around the front wheel so the back is going up.
Friction force on tire is F=N*f. N is force of your weight. f is constatnt of friction depends of rubber and what is ground made of.
So when you brake fork dives, back is trying to go up N force is getting smaler so the F is smaller too, than you are loosing grip and it is getting even more smaller. So you dont need so much force to block rear wheel and to avoid that you use less powerfull brakes at the back.

 Some weight weiner probably wanted to save 4 grams in the early 2000s and the trend just stuck as people tried to justify their reason for copying someone they thought was cool.

 Im surprised Marshy and the comment section isn't discussion brake modulation. The smaller the rotor, the more force it takes to stop it, and therefore the better the modulation. Better modulation because the more force required, the more room you have to slow instead of stop before braking traction. Minimal for sure, but worthy of being a part of the discussion if weight savings from a 180 to 203 is being considered.

 I have been messing around with this particular topic since my very first disc brakes on an mtb; Hope C2. I use my front brake much more than the rear on bike and moto. On DH I have the same size rotor front and back for the very reason he mentions in the final 1/3 of the video. I don't have a gear box and an engine I can use to brake as well and the speed, heat dissipation requirements and I once had a bike with Hope 6ti up front and the 4 pot out back. That was great in the UK but after 2 weeks in the summer in Portes Soleil I cooked the caliper and it was leaking. Same happened in Portugal later that year (note: Hope Service is next to none; sent in direct for £75 and fully rebuilt caliper and new pads both times). However on my trail/enduro or whatever you want to call it this and next season, the rear rotor is smaller. I save weight, I catch it less on rocks on narrow passages, I have yet to blue one, the speeds are not full on as in DH, and yes vanity it looks better imho. Size matters. Even when you do not understand the basics of physics, when a stick wacks you around the head it hurts. All about energy.

 It's simple. Your discs are blue or black: run bigger discs. You ride in the Alps or in any bigger mountains with long descends: run 200 mm > discs read and front.

I'm riding 180mm in the back of in my bike right now in the Alps. With 82kg and aggressive riding, it's not enough.

 I reduced my stock 203mm rear to a 180, the lack of weight over the back wheel on steep stuff, combined with a big ol' brake meant it locked up as soon as you looked at it.

would I get less brake jack (its a single pivot) if I could get away with a 160mm, even if it just kept me off the back brake a bit.

 200mm Avid in the front 185mm Hope in the rear cause that’s what came on the bike when I bought it. I’m also running Avid Elixcer CR’s which I think most everyone hates but they work for me. Got two sets of Trucker Co pads but haven’t put them on yet so no clue how they work.....

 Bigger isn't always better. Keep in mind this is at the highest level of racing as well. On my DH bikes i have run 200 mm front 180 rear. On my trail bikes 180 front 160 rear. HT 160 fr 140 rear. Modulation is key for control. And control trumps sheer power any day for me.

 lol. soon we will have 27.5 inch rotors and then we will just go back to rim brakes.
(in no way am i disputing the advantage of large rotors over small ones or rim brakes, just to be clear)

 Once you go 200/200 you never go back

 Let's put a camera in front of this idiot and see what happens.. You don't need the same amount of power for the rear. I run a 183, 4 piston front and a 160 2 piston rear. No issues. If I want to skid, cuz idiots need to skid to change direction, I would put a 4 pot or a 183 rotor on the rear. But I'm not an idiot. So I wouldn't do that.. Just sayin..

 ever been to Morzine´s hidden tracks?... check your rear rotor after a couple laps...^^

 The answer for a smaller rear brake rotor, it is because this cause less stres to the rear triangle, avoinding a posiible crack.

 Wouldn't imagine that motorcycle engineers would take into account engine breaking when sizing brakes. Its not out of the possibility to be in neutral. CG of a bicycle or motorcycle are quite high compared to their wheel base so the weight transfer in turn is more.

 The title is misspelled or I don’t get the joke

 Remind me, who was the guy built up Peaty's bike this way:
cdn.mos.bikeradar.imdserve.com/images/news/2009/12/22/1261478324249-1jwjz35o8e98p-960-540.jpg

 Agree 100%- maybe clearance, but really a 10mm (top and bottom) difference, giving up added heat dissipation and power. Make all your brakes Trump sized- huuuuuuuge.

 Front slows you down,back is for control-therefore can be smaller.
If you don’t know get out of the pits.

 I currently run a 180/180 set up, and the only reason I would run a 200/180 is because 1 new rotor is cheaper than 2.

 Funny tio ear the bike industries talking about the bike industries

 223Front 203Rear or 203 both nothing less!

 Fox tech guys, using RockShox digital shock pump. Funny.

 I'm a clyde....the bigger the better for me....both ends!

 I'm mostly 100% sure Jason's trolling the pits, and us.

 why do you need to even brake in the first place

 The guys got a good point

 Cuz it’s moto

 Who even uses brakes?

 So everybody will be laughing at my 140mm rotor on my Rocky?

 Maybe I'm just running a bigger front rotor. Ever think of that?

 Big front, Bigger back is more betterer

 Brakes only slow you down. Smaller real rotor looks cooler and less likely the be bashed on stuff.

 Works for Rossi.