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Big Caliper Little Rotor vs Opposite

Westy

Westy

the teste
Nov 22, 2002
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Sleazattle
Jm_ said:
But they don't. They only need to absorb more energy in terms of time, not in terms of peak, so having them built for "peak" is totally inappropriate IMO. It's the kind of usage that causes you to go through pads quicker, but you are only ever operating at a fraction of the forces of the front. That's rotor size for heat dissipation and absorption, not lever/caliper leverage.
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If someone offered a bike with a different rear caliper with different pads the "this is what's wrong with the industry" would blow up for weeks. This seems very much like a Jm specific problem. I can swap rotor diameters, wheel size, or pad material on one end of my bike and adapt with no problems in about 3 seconds. I can even jump on a motorcycle right after a bike ride or vice versa and have no issues with completely different body parts operating brakes with different power.

Maybe you can sell your idea to some roadies so they can save 3 grams on rear brakes
 
Jm_

Jm_

sled dog's bollocks
Jan 14, 2002
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englertracing said:
Not


Sm and sports bikes have gigantic 3xxmm diameter front rotors. Moar pistonz up front.
Dual discs in the case of the sports bikes.

They have engine braking...

Mtb doesnt.
So same size discs, rear thicker or vented, or freeza makes sense
Im not sure i love having two different lever feels....
The amount of weight youd save is.....
Maybe having slightly smaller rear pistons would be "optimal"? On brakes with spongey hoses the rear is softer.... that would stiffen/quicken it a bit.....
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Yeah, it's not about saving weight. Some people are making this out to be me claiming that we should be running XC calipers on 203mm rotors. I'm not saying that, I'm saying at least a closer-matched setup to the application, front brake vs rear brake. You'll still be able to lock up a rear wheel on command with a T3E4 even, but you'll at least have more matched front/rear braking feel and should have better feathering performance. I mean, yeah, we are very adaptable, we can make different brakes front and rear, by type and brand, work "just fine", but we can be better too IMO and not try to make it worse by putting the same brake on the rear end. Everyone trying to convince me that I need the same leverage and everything else on the rear seems to be bat-shit-crazy and then the ones saying they like to run a smaller rotor are just proving my point, except they miss out on the heat dissipation/longer pad life.
 
Westy

Westy

the teste
Nov 22, 2002
55,944
21,974
Sleazattle
englertracing said:
Not


Sm and sports bikes have gigantic 3xxmm diameter front rotors. Moar pistonz up front.
Dual discs in the case of the sports bikes.

They have engine braking...

Mtb doesnt.
So same size discs, rear thicker or vented, or freeza makes sense
Im not sure i love having two different lever feels....
The amount of weight youd save is.....
Maybe having slightly smaller rear pistons would be "optimal"? On brakes with spongey hoses the rear is softer.... that would stiffen/quicken it a bit.....
Click to expand...
Not to mention moto brakes have a rear brake lever you can literally stand on, you do not want "power" vs a front brake where you use fingers.
 
englertracing

englertracing

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Mar 5, 2012
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Westy said:
Not to mention moto brakes have a rear brake lever you can literally stand on, you do not want "power" vs a front brake where you use fingers.
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There is that but at full brake on a sport bike gentle touch of the toe will do to lock the rear

And on dirt bikes too much stalls em... and in the case of a 4t bastards dont relight
 
Westy

Westy

the teste
Nov 22, 2002
55,944
21,974
Sleazattle
englertracing said:
There is that but at full brake on a sport bike gentle touch of the toe will do to lock the rear

And on dirt bikes too much stalls em... and in the case of a 4t bastards dont relight
Click to expand...

I honestly have never been super comfortable with the rear brake on street bikes. Engine braking with the clutch feels a lot more natural.
 
OGRipper

OGRipper

back alley ripper
Feb 3, 2004
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NORCAL is the hizzle
Jm_ said:
Everyone trying to convince me that I need the same leverage and everything else on the rear seems to be bat-shit-crazy and then the ones saying they like to run a smaller rotor are just proving my point, except they miss out on the heat dissipation/longer pad life.
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Not trying to convince you of anything, you do you.

All else being equal, even it's true a smaller rotor might dissipate heat better, won't it also absorb more in the first place? And isn't that where you get issues with fluid temperature, friction loss, etc. (experienced as fade), especially on longer descents? Are you saying faster dissipation of more heat is better than slower of less? Isn't it better to avoid higher heat in the first place?

This makes me want to try a reverse mullet brake set up.
 
Electric_City

Electric_City

Torture wrench
Apr 14, 2007
2,047
783
Sram brake question. When you're asking "how long is the lever?". Are you referring to the length of the lever or how many weeks till you have to warranty it?

Lever too long?

Screenshot_20240227_124957_Chrome.jpg
 
FlipSide

FlipSide

Turbo Monkey
Sep 24, 2001
1,432
888
Somewhat related to this thread:

I happen to have sets of G2 RSC, Code RSC and Mavens Ultimate at home and I measured their weight yesterday evening.

All brand new sets (F + R) with stock pads and uncut lines. No rotors, no bolts, no bar clamps, no plastic pad spacers, no adaptors.

G2 RSC: 515g
Code RSC: 615g
Mavens Ultimate: 720g

Given how big the Mavens calipers and lever bodies are, I was expecting an even bigger difference between the Codes and Mavens.
 
Muddy

Muddy

ancient crusty bog dude
Jul 7, 2013
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FlipSide said:
Somewhat related to this thread:

I happen to have sets of G2 RSC, Code RSC and Mavens Ultimate at home and I measured their weight yesterday evening.

All brand new sets (F + R) with stock pads and uncut lines. No rotors, no bolts, no bar clamps, no plastic pad spacers, no adaptors.

G2 RSC: 515g
Code RSC: 615g
Mavens Ultimate: 720g

Given how big the Mavens calipers and lever bodies are, I was expecting an even bigger difference between the Codes and Mavens.
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Are certainly the top-tier of any weight categories - however for AM ~ DH ~ eBike that's not going to be focused upon as much. Appears alot of co-mingled performance, alot likely a result of the heft, external bracing and however all these materials soak heat for the pads. I do doubt this is a product rushed into production.

Have maintained HFX-9, Tech2 M4 EVO, Code RSC and Code RSC Ultimate T-Type. All great for their time, another set of Code RSC Ultimate T-Type gen. is going on a mountain bike build project. 203mm F / 180mm R all the time. Am not racing and not w/ plans to be riding a lift more than 2 times a year and use my brakes how they were meant. Maven were an option but likely not needed in my case.
 
A

Andeh

Customer Title
Mar 3, 2020
1,182
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sbabuser said:
9 bikes in my garage with SRAM brakes, none of them have issues with stopping or needing more power. Sounds like a "you" issue.
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Yeah, when I ran Codes they had lots of power after I replaced the stock pads. My issue with them was just how stiff the pull force was until engagement, especially after I tried Dominions.
 
P

Pneuma

Chimp
Nov 5, 2021
77
61
Andeh said:
Yeah, when I ran Codes they had lots of power after I replaced the stock pads. My issue with them was just how stiff the pull force was until engagement, especially after I tried Dominions.
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What pads did you end up with that you liked?
 
englertracing

englertracing

you owe me a sandwich
Mar 5, 2012
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La Verne
sbabuser said:
9 bikes in my garage with SRAM brakes, none of them have issues with stopping or needing more power. Sounds like a "you" issue.
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How good are your nose manuals? Can you go round switch backs? How much do you weigh? what kind of dirt are your local trails? How steep?
 
Jm_

Jm_

sled dog's bollocks
Jan 14, 2002
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OGRipper said:
Not trying to convince you of anything, you do you.

All else being equal, even it's true a smaller rotor might dissipate heat better, won't it also absorb more in the first place? And isn't that where you get issues with fluid temperature, friction loss, etc. (experienced as fade), especially on longer descents? Are you saying faster dissipation of more heat is better than slower of less? Isn't it better to avoid higher heat in the first place?

This makes me want to try a reverse mullet brake set up.
Click to expand...
A smaller rotor would dissipate heat better? What?

I think what I was saying is a lot of people will downsize their rear rotor due to this very issue, that if too large, it makes the rear brake too sensitive. The issue though with that is you then get into the situation of burning through pads and possibly not having enough heat-management. The ones that run a bigger rotor generally have the heat management and pad-life going for them, but they are left with fairly extreme asym brake operation, which yes, you can adapt to most of the time...but why force this non-optimal situation? I think that just comes down to the industry and it's much simpler for them to sell you the exact same rear brake as front brake.

Ideally, I'd want something like a Hope T4 front lever and T3 rear lever (which I run on 3 bikes)...or some other way to have slightly less leverage for the rear brake, other than a smaller rotor, to avoid the heat issues. I'm not sure what the equivalent would be for all brake brands, but I'd imagine for some it would simply be a matter of running a different rear lever.
 
OGRipper

OGRipper

back alley ripper
Feb 3, 2004
10,732
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NORCAL is the hizzle
Jm_ said:
A smaller rotor would dissipate heat better? What?
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I misunderstood your earlier comment, which appeared to say just that.

Jm_ said:
The ones that run a bigger rotor generally have the heat management and pad-life going for them, but they are left with fairly extreme asym brake operation, which yes, you can adapt to most of the time...but why force this non-optimal situation? I think that just comes down to the industry and it's much simpler for them to sell you the exact same rear brake as front brake.
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I think this where I (and others) just disagree. Call it "extreme" if you want to be dramatic, but yes we adapt. And personally I don't want to self-handicap by lowering rear brake performance based on a desire to equalize. I prefer brake performance that is too good than not enough.
 
Sandwich

Sandwich

Pig my fish!
Staff member
May 23, 2002
21,784
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Didn't have time to read page three, but here are my thoughts:
Gustavs were the only brake I've ever wished were weaker. Even the gentlest touch locked up my wheels on a muddy, slippery day at highland, even with relatively tacky tires. I simply could not brake gently enough to not skid. Maybe I was used to the dreadful Hope DH04s, but the maguras were obscene.

I run MT5/MT5 on my trailbike 29er with 203/180mm rotors. I have an MT Trail caliper in the box, but everything I've read suggested they have a very different feel to the MT5 caliper, so you get noticeably different lever feel which I didn't want. Add to that two identical calipers gives you identical pads front and rear to swap as you like and I don't see a good rational for different calipers vs different rotor sizes. Maybe that's something for the MFGers to try, but it seems like 95% of people are happy with a downsized rotor on the rear and two identical brake systems
 
Gary

Gary

my pronouns are hag/gis
Aug 27, 2002
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Been working on DH bikes today so measured lever pivot to lever blade end distances for anyone delusional.
Hope tech 4 90mm
Code RSC 80mm
Saint 75mm

Also super modded T4s to quieten down annoying bite point adjuster "tap tap tappy tap tap"
_20240229_144328.JPG
 
Jm_

Jm_

sled dog's bollocks
Jan 14, 2002
20,065
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AK
OGRipper said:
And personally I don't want to self-handicap by lowering rear brake performance based on a desire to equalize. I prefer brake performance that is too good than not enough.
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To me though, that means that your front brake is then still woefully inadequate?, because of the giant disparity between front and rear power? So your rear brake is way overkill, fine, but your front is barely doing it's job comparatively?
 
Gary

Gary

my pronouns are hag/gis
Aug 27, 2002
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In reality though. On occasion you do actually want to be able to lock the rear wheel instantly. Front. Not so much.
Ie. Each hand knows fine it's doing a different job. And even ambis have a weaker less skillful hand. That SHOULD be operating the rear
 
OGRipper

OGRipper

back alley ripper
Feb 3, 2004
10,732
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NORCAL is the hizzle
Jm_ said:
To me though, that means that your front brake is then still woefully inadequate?, because of the giant disparity between front and rear power? So your rear brake is way overkill, fine, but your front is barely doing it's job comparatively?
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You're just debating theoretical aspects at this point. No, just because I may be over-braked in the rear does not mean my front brake is inadequate. :crazy:
 
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