Brake rotors for XT brakes

[Mopkop]

Hi guys

 

Im in need of new disc rotors but theres so many options and prices. I've got XT brake on my bike and I used Baradine rotors, braking was not bad but the baradines were sold.

 

Ive been looking @ getting shimano rotors, they're pricey though but I'm sure they'll be worth it.

 

Options are:

 

RT66 R280 for 160mm

RT76 R420 for 160mm

RT86 R565 for 160mm

 

The 180mm are abit more in price. I had a 180mm front and 160mm rear.

 

My questions are:

 

* what difference will there be when running a 160mm rotor infront?

* which disc will give me performance and good value?

 

I currently weigh 69kgs and LOVE the technical stuff!!

 

All advice welcome

[MrJacques]

You'll have less stopping power with the 160 up front than with the 180. Most people will be fine with 160 though. 

 

Check out this ad, some nice prices  https://www.bikehub.co.za/classifieds/100177-160mm-180mm-disc-rotors/

[Captain Fastbastard Mayhem]

Just go for the Alligator Pizza rotors from CWC. 180mm is about R 250 or so, if I remember correctly, and they're plenty strong and have loads of material. 

 

Just don't go for the Windcutters or any of the other "fancy" designs. They don't have sufficient material on them to allow the brakes to perform at their optimum level. I have the 203mm versions of the Pizza rotor on my bike, and they're wonderful. Strong, good performers and cheap. They're not that light when compared to other rotors, but they're plenty good enough. 

[hayleyearth]

Rotors are very expensive! I have been looking for 160mm but damn the prices!

 

Also be aware some rotors can only be used with resin pads (I use sintered, so the 'cheap rotors' wont work for me).

 

What type of terrain do you ride?

 

Like mentioned the 180mm will give you more stopping power up front. I actually went for a ride this weekend (did a few jumps etc) and the bike only had a rear brake which is 160mm. I wont advise that though if you going 30km/h+ and need to stop in a short distance..haha

[Daniel J Méssem]

bugger rotor gives more braking 'torque', smaller can give better feel.

 

a 180mm rotor on a 29er wheel gives roughly the same braking torque as a 160mm on a 26er wheel

 

bigger rotors also reduce fade, as do Al cored rotors (ice tech) finned pads, which you may have on the xts also decipate heat and help with fade

 

fade is usually only important on long decents.

 

too much torque can give less brake feel, resulting in locking up, too little torque can result in one nor being able to lock up when wanted (trial stuff, intensional slides)

 

that's my 2c, pretty happy with 180mm front and 160mm rear on my 29er, no fade on long decents and im 100kg kitted up

[Jigghead]

I'd stick with same spec/sizes as the bike came with. Most come with 180mm in front so I'd stick with that. cost difference is not that dramatic AFAIK.

[DR ◣◢]

bugger rotor gives more braking 'torque', smaller can give better feel.

 

Care to elaborate on that? I have the exact same brakes setup on my DH bike and AM bike. Both with a 203mm rotor in front and the AM has a 180mm on the back compared to the 203mm on the DH bike. 

 

There is absolutely no difference in how they feel.

[Mopkop]

Thanks for all the replies!! Any advice on the difference in rotors?

[Daniel J Méssem]

Care to elaborate on that? I have the exact same brakes setup on my DH bike and AM bike. Both with a 203mm rotor in front and the AM has a 180mm on the back compared to the 203mm on the DH bike. 

 

There is absolutely no difference in how they feel.

 

So with a smaller rotor, more force is required on the brake lever to produce the same braking torque to the wheel - this results in a larger range of brake lever force required for the same range of breaking torque, meaning better resolution at the brake lever 

 

The difference will be smallish, around 12%, very hard to tell any difference especially on different bikes. Fabien Barel reckons he can feel the difference, and thus uses smaller rotors whenever racing a course that does not demand larger rotors. 

 

As for testing the idea, a double blind test does not seem very practical - so I cannot provide actual proof

[DR ◣◢]

So with a smaller rotor, more force is required on the brake lever to produce the same braking torque to the wheel - this results in a larger range of brake lever force required for the same range of breaking torque, meaning better resolution at the brake lever 

 

The difference will be smallish, around 12%, very hard to tell any difference especially on different bikes. Fabien Barel reckons he can feel the difference, and thus uses smaller rotors whenever racing a course that does not demand larger rotors. 

 

As for testing the idea, a double blind test does not seem very practical - so I cannot provide actual proof

 

The theory seems sounds. Thanks for the info.

[Mopkop]

Another question: Is there a noticeable performance difference between the brake rotors i.e. ZEE(RT66) vs XT(RT76) vs ICE-TEC(RT86)? I've got the resin pads with the cooling fins installed.

[tunariaan]

Check the Awa shima rotors

Evo bikes sells them

They are also superlight and i have been using them for over 2 years now on mostly technical stuff

They are super

[camelman]

If it is XC you are doing and love the technical stuff, then a 160mm will do up front for your weight. although I would always advise a 180 up front, just much better stopping power.  There are no descents in CT that are long enough for XT brakes with Ice tech pads to fade.  

So I would not even bother with Ice Tech Rotors.  Get normal solid stainless steel rotors, the Zee's if you wanna stay with Shimano or any other disc that fits your pocket (even the Pizza cutters like Mayhem suggested).  I ride Magura Storm SL's on all my XC bikes(180/160), regardless of the brake type and they work perfectly well for my weight and shave off a few grams.