Interesting article - https://enduro-mtb.com/en/rotor-size-myth/
Rotor Size Article - Larger Rear Rotor?
- Thread starter djjohnr
- Start date
except my dj bikes, i've never run anything smaller than 180mm rotors(i also only run 26" wheels) and never really understood why others did except for the weight watcher nerds. there is a hugely noticeable difference using smaller rotors...
riders upwards of 175 lbs?
i think that's one major thing a lot of bike media orgs are ignoring, is that there are a lot of riders well north of this.
i think that's one major thing a lot of bike media orgs are ignoring, is that there are a lot of riders well north of this.
also, i run 160 rotors on the back of both my enduro and xc bikes, but there's not enough riding locally with long/steep enough descents to warrant more braking power via a larger rear rotor. i'd also note here that i'm of the mindset that rear brakes are for controlling speed, and front is for stopping.
i will say i run 200mm rotors front and rear on my DH bike.
i will say i run 200mm rotors front and rear on my DH bike.
Likewise. Most of my "long" descents are about 1 minute on the trail. I've never had an issue w/ power in the rear. I have gobs of power even with a 160mm rotor. Traction is always the limiting factor.
I'm running 200mm F/R on my 29 trail bike and 27.5 DH bikes. Both rear rotors are discolored, both fronts are fine. Local trails are mostly steep renegade fall line stuff with shitty traction. I'm going to try 220 on the rear of the DH bike; I'd like to try them on the back of my trail bike as well but I haven't seen 220 IS adapters yet.
I always go with the smaller rotor in front? Is this news?
Yeah, I've always questioned the conventional wisdom on rotor size as applied to bikes. I also question the mixed caliper set up like Magura, with a 4-piston in front and a 2-piston in back. If I need a mix I'll take the opposite. I may be guilty of brake-dragging sometimes, but still.
I'm around 200 lbs and do some pretty long descents.
I'm around 200 lbs and do some pretty long descents.
My only trepidation is snaking the rear end of the bike through tight rocks on the über-chunk...220 would be really, really succeptible to getting knocked, IMO.
at that point, your rear derailleur would have been gone about an hour ago, so i don't think the issue is as problematic as you think...
8"/200/203 F&R on both 29er trail and 27.5 enduro bikes. It's easier to carry spares for trips and racing if they're all the same size.
180 rear was fine on the trail bike till I used it for a couple of enduro races last year where I noticed the E4s were starting to suck badly at the end of the steeper stages. Thats probably more a reflection on E4s than the rotor though.
fuck I wish they'd sort the 200/203 malarkey
180 rear was fine on the trail bike till I used it for a couple of enduro races last year where I noticed the E4s were starting to suck badly at the end of the steeper stages. Thats probably more a reflection on E4s than the rotor though.
fuck I wish they'd sort the 200/203 malarkey
190 lbs (and dropping!) with many long descents. Awaiting new hooks, but will be 180F/R. Currently Saints w/metal pads and 180/160 rotors.
Trail bike with no longer fashionable wheelsize has been 180/180 for a long time. DH bikes have always been the 200/203 size F+R. 29er DH bike would definitely be looking at the newer 220 rotors F+R
Most "older" trailbikes didn't necessary allow for greater than 180mm out back, and lots of current bikes etc aren't cleared for the new 220 sizes...
Most "older" trailbikes didn't necessary allow for greater than 180mm out back, and lots of current bikes etc aren't cleared for the new 220 sizes...
I run larger in front than back, aiming at braking equalized in effectivity with roughly equivalent finger pressure front and back. It helps, I guess, not to be a lardball...
Let me throw a wrench in the gears: if you want the system truly optimized, run a larger diameter rotor up front for power, and a smaller diameter but thicker rotor in the rear for heat capacity with a better braking power balance f/r.
Sounds like a way to get added heat soak.
That's like slapping a big ol' capacitor in a doof doof car with an inadequate charging system.
EDIT- High carbon steel would probably be a better rotor choice as it is a fair bit more conductive than stainless but people probably wouldn't tolerate rusty rotors. I guess you could call it patina and double the price.....
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Or a rotor with more surface area: https://brake-stuff.de/en/brake-discs/6-hole-is2000/75/disc-rotor-in-punch-design-6-hole-shimano-compatibel
I think they are ripping off Intend Aero discs, or license the design from Cornelius, not sure.
Hi, they made the rotors for Cornelius, He dont sell them anymore. Thats a shame because they were amazing, these will be probably as good as the Aero rotors, but I dont like the design of the rotors spokes.
Same
I've always advocated same size rotors at each end. In MTB there's too much rear brake dragging and ability to shift weight back to use the motorsports idea of smaller rear rotor. I don't know about this article's idea of a larger rear rotor but I am about to put same size rotors on a mullet.
If a person is switching from Codes with 200mm SRAM rotors to SLX with 203mm Icetech rotors, does that person need new adapters? Could that person just cheap out and use a couple of washers if this is a short-term thing? Or just keep using the existing SRAM rotors and adapters? Asking for a friend...
165 lb brake dragger running 203 front/rear. I call BS on the article. I noticed I get a lot less blueing and warping on the rear once I went from 203 f / 180 r to 203 f/r. And that's with running Magura's thick rotors. It's hard to articulate, but I also like the feel better of the balanced setup when suddenly coming nearly to a standstill when lining up on a steep roll-in.
My bike's already like 34.5 lbs, it's not like dropping to a 180 is suddenly going to get it down to 30.
My bike's already like 34.5 lbs, it's not like dropping to a 180 is suddenly going to get it down to 30.
Washers are absolutely fine, IME.
just make sure your bolts have enough purchase.
totally fine considering old school disc brakes used to use a stack of flat and conical washers to line everything up
This "doctor" has hit the crackpipe a few too many times...
1) Larger rotors have a place on larger wheels because of the torque proportioning, not rotational inertia. The application of tractive force at the tire versus lever pressure is a linear, direct, and discrete relationship between two diameters (rotor and tire), friction values at the pad and the dirt, hydraulic leverages and system stiffness. It's analogous to a linkage suspension system and throwing a longer swingarm on and adjusting accordingly.
2) The CTE of a SS rotor means fuck-all at the temperatures and clearances we're talking about. The ribs are directional struts to resist the braking force direction from the caliper....not thermal expansion. Not even one tiny bit. In the automotive world, there are CTE concerns to be had in the construction of a rotor. Sometimes in the street bike moto world. Rarely in the dirt bike world. Never in the mtb world. In fact, the usual layout for mtb rotors would be a TERRIBLE architecture for CTE consistency.
Follow-up edit: A 400C change to 110mm radius material of 304SS would be a .7mm change (about .028"-.030"). IF, and ONLY IF all of the material of the rotor were brought to that temperature....and it isn't. It's localized heating. And that's a very extreme case for MTB brakes. And typical radial clearance inside a caliper is outside of that expansion. If there were a CTE concern, having arc'd spokes versus radial spokes would have zero effect in a linear CTE situation. I hope his graduate advisor sees this shit.
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I would love it if someone made a high carbon steel rotor for a mtb. Similar weight, lots stronger for impacts, and much higher friction coeffecient with most common pad compounds. I run these on my moto (which are surprisingly hard to find) and they're wicked. If rust is an issue, coat them before you install them and let the pads burn off the coating on the braking surface.
Artisan rotors hand forged in charcoal fired kilns from responsibly sourced scrap iron. You've heard it here first.
If we ran supercritical plutonium rotors, would lights be needed for night riding?
Sounds great for ebikes though.
Yeah, with a Peltier generator you wouldn't need batteries.