[Lombard]

I created an account to specifically support your efforts with a search for a 180mm flat mount fork adapter. These other responses are pretty elitist at best (if you don’t have something or constructive to say, keep your keyboard to yourself).

Welcome to RBR where anonymity breeds hostility! Seriously, some posters can be harsh and like to throw their weight around, but can be helpful anyway.

Perhaps this was the wrong forum for the question as my application is a gravel bike that use largely road bike parts. I routinely hit 15-22% grades and long steep descents in Northern California. Any help with confident, reliable braking is welcome.

Well I guess if you are descending 20%+ long hills, you need all the braking help you can get. Are you climbing those same 20%+ hills? Heck, anything more than around 16-17% and I'm walking!

 

[Okcorrell]

Thanks for welcome! Yes, decency is often lost in a faceless world.

Welcome to RBR where anonymity breeds hostility! Seriously, some posters can be harsh and like to throw their weight around, but can be helpful anyway.





Well I guess if you are descending 20%+ long hills, you need all the braking help you can get. Are you climbing those same 20%+ hills? Heck, anything more than around 16-17% and I'm walking!

Yes, but I am not breaking any records in any respect. Grind, grind, grind my way to the top. The descents are made even trickier with loose gravel on the majority of double track fire roads. Happy and safe riding!

 

[nova_rider]

I'd argue that pros can and will descent steeper, faster, and brake harder than anyone here, yet I am not aware of any complaints about 160mm not being sufficient from any of the top-tier pro teams.

Effective braking has more to do with knowing the proper technique than having fancy hardware.

 

[Lombard]

I'd argue that pros can and will descent steeper, faster, and brake harder than anyone here, yet I am not aware of any complaints about 160mm not being sufficient from any of the top-tier pro teams.

Effective braking has more to do with knowing the proper technique than having fancy hardware.

I'm also guessing if the OP is doing mostly gravel and off-road riding, he's not bombing down the hills super fast in the first place.

 

[ogre]

I'm also guessing if the OP is doing mostly gravel and off-road riding, he's not bombing down the hills super fast in the first place.

Bombing down the hills is a lot easier on the brakes than creeping down.

 

[Lombard]

Bombing down the hills is a lot easier on the brakes than creeping down.

Bombing down and then trying to slow down after getting up to 40+ mph or more?

 

[nova_rider]

I'm also guessing if the OP is doing mostly gravel and off-road riding, he's not bombing down the hills super fast in the first place.

Ok, so I will ask what is the problem again?

 

[Lombard]

Ok, so I will ask what is the problem again?

My point was in confirming your point in case it wasn't obvious.

 

[Okcorrell]

I'd argue that pros can and will descent steeper, faster, and brake harder than anyone here, yet I am not aware of any complaints about 160mm not being sufficient from any of the top-tier pro teams.

Effective braking has more to do with knowing the proper technique than having fancy hardware.

I agree with you. Despite the elite advice, I am not a pro rider. I also would not consider 180MM fancy hardware.

 

[duriel]

Are u using cable or hydraulic brakes? Due to the long descents that I do, I changed to hydraulic, and it is a world of difference drag braking.

 

[Chantecler]

Increasing the rotor size will not increase modulation, and may actually decrease it. Also, difference in surface area between a 140mm rotor and a 160mm rotor is negligible (do the math), so that won't affect heat dissipation. And the OP started this thread over two years ago so I bet he or she has moved on from this topic.

But hey, welcome and thanks for joining! This place is a ghost town. Yeah, some posters can be acerbic but there's a lot of knowledge you can get from this site.

Pi R squared would be entire volume of a disk, move r from 70 to 80 and r squared goes from 490 to 640 times Pi (3.142) and the difference (150 delta x 3 is massive). Or just diameter, 2Pi x r = about every millimetre increase in radius is over 6 times increase in diameter... so a 140-160 disk increases diameter from c6x70 to c6x80 = 420mm diameter to 640mm diameter. So the diameter increase is over 50% From 140 to 160. I mean just in my head, no calculator or anything.

 

[Chantecler]

Btw I have a canyon lux (xc) that runs flat mount 180 front and 160 rear. Nothing unusual with those sizes even for weight weenie world champions, who would shift down if they could but don’t want to lose heat dissipation, modulation etc.

 

[cxwrench]

Pi R squared would be entire volume of a disk, move r from 70 to 80 and r squared goes from 490 to 640 times Pi (3.142) and the difference (150 delta x 3 is massive). Or just diameter, 2Pi x r = about every millimetre increase in radius is over 6 times increase in diameter... so a 140-160 disk increases diameter from c6x70 to c6x80 = 420mm diameter to 640mm diameter. So the diameter increase is over 50% From 140 to 160. I mean just in my head, no calculator or anything.

You've forgotten your maths.
Every mm increase in radius = 2mm increase in diameter. Circumference is the word you were looking for. A 140 or 160mm disc is just that...140mm or 160mm diameter. Trying to sound smart only works when you get everything right.

 

[Lombard]

You've forgotten your maths.
Every mm increase in radius = 2mm increase in diameter. Circumference is the word you were looking for. A 140 or 160mm disc is just that...140mm or 160mm diameter. Trying to sound smart only works when you get everything right.

I'm no smartypants, but it's surface area that is significant here. Doing the calculation Pi * R * R:

For a 140mm disc, 3.142 * 70 * 70 = 15,396 sq mm

For a 160mm disc, 3.142 * 80 * 80 = 20,109 sq mm

Difference = 4,714 sq mm

So, the 160mm disc has 30.6% more surface area than the 140mm.

Of course I am reminded of a quote from one of my favorite posters on this forum, DCGriz, who wisely said, "With bicycles in particular, it is important to separate what is merely true and what is important". A bike with 140mm disc brakes still has more stopping power than a similar rim brake bike. Unless you plan on riding your brakes down 1-mile long steep hills or longer, the 140mm disc brakes will slow and stop you just fine without melting.

 

[duriel]

If your going to do an exact calculation, are those are the outside diameters? The actual center line of the caliper may a significantly different than those numbers.

 

[Lombard]

If your going to do an exact calculation, are those are the outside diameters? The actual center line of the caliper may a significantly different than those numbers.

Oooops! You are correct! The usable surface is not Pi * R * R because of the spider. So you would need to know the radius of the inner disc surface As I said, I'm no smartypants!

 

[duriel]

I think one could flip the bike with rim/120/140/160/180 brakes, so in reality, we are discussing modulation & heat dissipation. The bigger the brakes the better the modulation & heat dissipation, no calculation is required.
My new moto has sexy twin front brakes, don't ask me why.

 

[ogre]

I'm no smartypants, but it's surface area that is significant here. Doing the calculation Pi * R * R:

For a 140mm disc, 3.142 * 70 * 70 = 15,396 sq mm

For a 160mm disc, 3.142 * 80 * 80 = 20,109 sq mm

Difference = 4,714 sq mm

So, the 160mm disc has 30.6% more surface area than the 140mm.

Of course I am reminded of a quote from one of my favorite posters on this forum, DCGriz, who wisely said, "With bicycles in particular, it is important to separate what is merely true and what is important". A bike with 140mm disc brakes still has more stopping power than a similar rim brake bike. Unless you plan on riding your brakes down 1-mile long steep hills or longer, the 140mm disc brakes will slow and stop you just fine without melting.

I'm no smarty pants either but you're forgetting something. Say the rotor surface is 10 mm 'wide'. So the surface area is a 160mm rotor is (3.14 * 80 * 80 = 20,096 sq mm) LESS the surface area of a 150mm circumference circle (3.12 * 75 * 75 = 17,663 sq mm), so total surface area is 20,096 - 17,663 = 2,434

Same calculation for a 140 mm rotor - (3.14 * 70 * 70 = 15,386 sq mm) LESS (3.14 * 65 * 65 = 13,267 sq mm), total surface area is 15,386 - 13,267 = 2,120

So the 160mm rotor has about 15% more surface area.

 

[duriel]

I don't know why you guys are worried about the surface area of the disk that the pad hits. If the rotor is connected to a plate that is the full internal diameter, that calc isn't right either. My disks have a metal heat dissipater that goes from the disk all the way into the hub, and it's vented!

The only braking is done by the pad! Which is virtually the same size on most brakes. The only thing that changes is the distance from the axle.

 

[Lombard]

I don't know why you guys are worried about the surface area of the disk that the pad hits. If the rotor is connected to a plate that is the full internal diameter, that calc isn't right either. My disks have a metal heat dissipater that goes from the disk all the way into the hub, and it's vented!

The only braking is done by the pad! Which is virtually the same size on most brakes. The only thing that changes is the distance from the axle.

You are correct. DOH! So it appears the only advantage to larger discs is greater heat dissipation - unless you also have larger pads.

Didn't I say I was no smartypants?

I'm no smarty pants either but you're forgetting something. Say the rotor surface is 10 mm 'wide'. So the surface area is a 160mm rotor is (3.14 * 80 * 80 = 20,096 sq mm) LESS the surface area of a 150mm circumference circle (3.12 * 75 * 75 = 17,663 sq mm), so total surface area is 20,096 - 17,663 = 2,434

Same calculation for a 140 mm rotor - (3.14 * 70 * 70 = 15,386 sq mm) LESS (3.14 * 65 * 65 = 13,267 sq mm), total surface area is 15,386 - 13,267 = 2,120

So the 160mm rotor has about 15% more surface area.

As I corrected myself in Post #36