Ttoc6

Yes, yes. In performance driving you want to avoid hitting that limit of ABS. You want to get it right up against the limit of your tires and then hold the brake presssure there as you slow down. Same on a bike.

As a positive to discs though.. In this crash a caliper brake would have been a head over heels crash as the rim came through and got caught in the brakes, possibly damaging the frame. I had a picture of it, but can't find it now... Rim was seriously dented probably 5cm out. No brake bridge / caliper means it was able to make that full rotation and he crashes upright rather than getting locked up.

Psimet2001 

That is a pretty good point about an advantage to disc. You can really trash a wheel and keep riding and braking.

in general about the skidding - we have enough power with modern caliper brakes to easily create enough braking force to overcome the tire's small contact patch's friction with the road. Thus skidding. We have the largest rotor available - the rim.

The assertion that there is more control in braking with a disc - yes. That's cool and all but....it is beneficial in activities like cross. Disc changed a lot of how the bike is raced in cross. Higher speeds into corners. more technical capability. but we had Cantis....can't stop won't stop cantis.

I would argue that the control in road is more nuanced and will find a place at some point...

Flatballer

Definitely an excellent point about the trueness of the wheel no longer being an issue. Might be the difference between calling a ride 30 miles out and limping home on a semi taco.

I'll buy psimet's self centering spring return system when it comes out. Until then I'll probably hold onto my rim brakes as long as possible.

spectastic

you can maybe also save 100g/rim when you don't have to add a braking surface.

Psimet2001 

100g is a TON of weight on a rim. You don't save 100g by eliinating the braking surface. Differences between Disc and Rim brake rims of the same model are nearly the same weight - albeit because they use the same rim and just don't machine it. On disc specific you are only dropping a few g. More like the ~20g difference between alloy or brass nipples.

Ttoc6

From Enve's website. Full wheel

3.4 Vs 3.4 disc -- 1372 vs 1420 g
7.8 vs 7.8 disc -- 1442 vs 1711g.

From Fairwheel bikes. Rim weights
3.4 vs 3.4 disc -- 445 / 448 grams vs 390/397 grams

So more like 50g per rim, but you give up a lot of weight in the hub. And through axles are heavy, which I'm pretty sure they aren't including in the full wheel weight.

Psimet2001 

Being a wheelbuilder - no - I have never picked up a set of disc wheels that were lighter than a comparable rim brake wheelset. Light wheels can be made - yes.

I was saying no to 100g a rim. It isn't 100g a rim. You say they list it as 50g a rim. In my experience with actual weights its more like 20-40g/rim. If the rim is completely redesigned it is something else, but in reality there isn't that much material in the brake surface.

spectastic

i was coming from the angle that cabon rims with alu braking surfaces tend to be quite a bit heavier than their carbon rim/carbon braking surface counterparts. why do they need to put that much more material to make aluminum braking surfaces?

in any case. the rim weight is the most important, because its rotational inertia is higher than a hub or a rotor. so in a heavier disc setup, the extra weight isn't so detrimental as one might imagine. besides, there are many other ways to save weight on a bike. and for non-gc-riders, weight shouldn't even matter.

gsteinb

Psimet2001 

Oooo I thought Aero was EVERYTHING!

spectastic

it is everything, almost

furiousferret

I've lost forty pounds for nothing. FML.

Psimet2001 

and here all this time I was mistakenly thinking I didn't do well because other riders were stronger and better.

mattm

You're probably more aero now, at least.

Voodoo76

(stronger and better)/CdA

dz_nuzz

Interestingly I am starting to lust over the new Tarmac Disc now after a particularly rainy race season.

rubiksoval

Was behind a Harley Davidson - Trek rider yesterday. They're all on disc- Emondas. Every time he stood up it was rubbing. Annoying.

Ttoc6

My mtb has a disc brake rubbing in the back because the freehub has gone out. Anyone ever have that problem on rim brake bike?

It's really a bizarre issue that I've tracked down and I can't find replacement parts for this freehub anywhere. Going to just deal with it until I can afford to upgrade wheels.

spectastic

they have thru axles, right? I thought they were supposed to help stiffen the wheel axle so the rotors don't rub. perhaps his thru axle wasn't properly tightened? I had a caadx ultegra which has 160mm rotors and quick release, and that thing rubbed when i put down maybe >800W. put some thought into getting a caad12 to replace the bike i recently broke, but that bike doesn't have thru axles.

btw, do people notice where the trend is going? it appears that the standard right now is 140 mm rotors and thru axles, but yet there are still some out there that are quick release. what about gravel bikes and cross bikes? are they sticking to 160 rotors and QR?

maybe buy a new free hub? anyway, how does a free hub cause disc brake to rub?

Ttoc6

Locating a source for the XD drive on these chines hubs is... difficult. And if you can figure out why.. let me know. I just know what's broke.

spectastic

if it's interfering with the disc, it has to be the hub itself, not the free hub body. is the wheel wiggling when the skewer is tight? if so, the bearings might need to be replaced.

Ttoc6

I'll give it another look, but it's through axle so things like to button down pretty tight in the frame.

Psimet2001 

Cross isn't as much of a mixed bag as it was. It and the road standards will be similar. Everything is going 12mm TA in the front and 12x142 or mavic Speedrelease in the rear. Rotor size is pretty much 140 across the board. Treks have still been using 160 on the fronts on cross bikes but they don't need it.

spectastic

dammit.. that means 12 speed too...

how long do you think the transition is going to take? a lot of disc brake bikes i'm seeing right now are still using quick release.

is 142 going to have better lateral stiffness than 135 or 130?

spectastic

see the new system six from cannondale? 140 rotors and thru axles, contrary to what they did with the caad12 and supersix..