Which rotors?

[quixoticgeek]

I need to replace my disk brake rotors. I had been planning to get the Shimano Ice tech ones, with the fins and stuff (not sure if the road or mtb version). But have seen some anecdata of these delaminating. I have a fear of my brakes failing for me on a long alpine descent and me going over the crash barrier (literally night mares, and losing sleep over it). So I want the best I can get in braking performance, but it also needs to be reliable. Esp on long 20+km descents, with 100kg of fat dike, and about 15kg of bike.

What brake rotors do you lovely people prefer?

I'm running 160mm front and rear.

J

[Sea of vapours]

Hope CL. They're not laminated so they can't delaminate. They also look pretty and appear reassuringly well made to go with the reassuringly high price tag.

[LittleWheelsandBig]

Mass counts, if you are sticking with steel rotors. Avoid the lightest options.

[Sergeant Pluck]

I’ve been using Shimano RT 64 and 66 with no problems to report - no 20km descents on my commute though!

[Hot Flatus]

Campag steel if you want decent life at almost half the cost of Shimano...but 100kg down 20k descents? Shimano Freezas are supposedly designed for heat dissipation but mine certainly ping more when hot compared to steel.

[quixoticgeek]

Campag steel if you want decent life at almost half the cost of Shimano...but 100kg down 20k descents? Shimano Freezas are supposedly designed for heat dissipation but mine certainly ping more when hot compared to steel.

You're the second person to suggest Campag steel (other is on youtube).

They are of course all out of stock...

J

[zigzag]

as well as new rotors, i would make sure my braking system freshly bled (if hydraulic) before the mountain trip to prevent brake fade. avoid dragging brakes.

it's quite easy to reach speeds of 80-90kph in the mountains, so it's good to feel confident about the setup.

[Ham]

I don't much care for alpine descents, I don't have time to look at the view and I get scared. In short, I'm a crap descender. I also worry more about the pads than the discs, and fitted Ceramic Pro with spares for just that reason, previous experience of brake fade (rather frightening) on alpine descent drove that decision. Not dragging the brakes is important and remember also you also are obliged to test the front disc to see how hot it has got using your finger tip. Disc wise I have Shimano ice tech fitted.

[iandusud]

If you are concerned about performance and not overheating you ought to consider bigger rotors.

[quixoticgeek]

If you are concerned about performance and not overheating you ought to consider bigger rotors.

I'm not sure if I could install 203mm rotors on my bike.

It's a Genesis Vagabond, using Shimano M8000 two piston Postmount calipers.

J

[rafletcher]

I think you'd be OK on the front with one of these:

https://www.amazon.co.uk/Shimano-Front-Mount-Adaptor-203mm/dp/B008K2HXGY

[Lightning Phil]

If you are concerned about performance and not overheating you ought to consider bigger rotors.

I'm not sure if I could install 203mm rotors on my bike.

It's a Genesis Vagabond, using Shimano M8000 two piston Postmount calipers.

J

You can also get 180mm rotors, if they will fit front fork.  It tends to be front brake only that sees the larger rotor.

[The Family Cyclist]

Swap out the rear wheel for a drag brake?

[zigzag]

160mm rotors will be not far from their limit, having big descents and a total mass in mind.

there are several options. the simplest and free - don't let the bike run away and start braking at 50-60kph*. another one to upgrade brakes - either by installing a larger rotor (if fork's strength and clearance allow) or/and by installing four-piston mtb caliper (not sure how well it would work with road levers).


*braking distance is proportional to the square of the initial speed, better safe than sorry

[grams]

The other option is pausing and letting the rotors / pads cool off a bit. There can’t be that many 20 km descents on your ride.

[FifeingEejit]

If you are concerned about performance and not overheating you ought to consider bigger rotors.

I'm not sure if I could install 203mm rotors on my bike.

It's a Genesis Vagabond, using Shimano M8000 two piston Postmount calipers.

J

The Limitation on rotor size for post mount is in the forks, both in design and approved stress.
I've not been able to find anything on t'interweb for the vagabond but I'm not exactly trying hard.
Might be worth an e-mail to Genesis although they may tell you 160mm both ends.


I had 203mm rotors on a carbon rigid fork for a bit, it didn't snap but apparently I shouldn't have gone over 160mm on them.

As for 4 pot calipers, I used Zee 4-pots on my full sus bike and they definitely worked better... to the point I was just locking up so not sure if they would help or hinder on the road; lever compatibility seems a bit odd according to this:
https://bicycles.stackexchange.com/questions/72316/compatibility-between-shimano-4-piston-hydraulic-calipers-and-levers-possible-c

I'd say that I've had little problem stopping 100kg of eejit with either rim brakes or disc, but I don't have that length of descent available to me, and I popped a tube on the tandem the other week with nearer 200kg plummeting down a 8% brae with visibility issues (although captain confidence issues were probably the bigger).

[andrew_s]

The Limitation on rotor size for post mount is in the forks

The limitation on rotor size is clearance and the availability of suitable adapters.

At the same braking force (i.e. rate of deceleration), big discs apply the same forces to the forks as do small discs.
The force multiplier is the ratio between the wheel size and the distance of the disc mount from the axle.
Braking force is limited by geometry, and since you can lift the back wheel with small discs, what a bigger disc gets you is reduced hand force and a bigger heat sink.

[FifeingEejit]

The Limitation on rotor size for post mount is in the forks

The limitation on rotor size is clearance and the availability of suitable adapters.

At the same braking force (i.e. rate of deceleration), big discs apply the same forces to the forks as do small discs.
The force multiplier is the ratio between the wheel size and the distance of the disc mount from the axle.
Braking force is limited by geometry, and since you can lift the back wheel with small discs, what a bigger disc gets you is reduced hand force and a bigger heat sink.

So what you say is the manufacturers lawyers talk pish.

Sent from my BKL-L09 using Tapatalk

[quixoticgeek]

Just ordered a pair of 160mm campag steel rotors.

Thanks all for the replies.

J