Question regarding rotors and disc brakes

Vacancy

Hey, all! Newbie here. I've recently acquired myself a job, and with my first salary I'm looking to upgrade my bike. I've done a fair bit of research on the best parts, where to get them and I've just been looking at hydraulic brakes and some information regarding rotors. The website I was looking at states that for every extra 20mm you have in your rotors, it will equate to around 15-20% extra stopping power. I currently have a GT Aggressor XC1 with Avid Juicy Three's, I'm looking to stick some Hope Tech M4's on it. Will I be able to upgrade the size of my discs? The rear one is 160mm, and the front is 180mm. Would I be able to put a 180mm on the rear bracket and a 200mm on the front bracket? Or will I need to stick to 160/180mm discs? Thanks for taking the time to read this and I look forward to seeing some useful replies

supersonic

You would new new mounting brackets. Hope Tech M4s are heavy and expensive, better for less.

Vacancy

How do I go about choosing mounting brackets? They all look like they have strange screwholes, and if I was to try and attach some of those to my bike I would end up with brakes on at 90 degree angles.. What brakes would you recommend? The reason I chose the Tech M4s was because they have a lot of stopping power, I'm looking for something that can stop me dead in my tracks on a huge decline, if you could be of assistance; that is.

Edit: I know that I'm definitely going to have to go for Floating Rotors, as my stock disc warped a little on the front wheel.

supersonic

Find out what type of mounts are on your fork and frame - then get the adaptor to suit that mount and the size of rotor you want to use. The mounts are either IS or PM, most brakes nowadays are PM.



So if your fork is IS, and you want to use a 200mm rotor, then you need an adaptor for IS forks mounts to PM brake mounts for a 200mm rotor.

http://superstar.tibolts.co.uk/product_ ... cts_id=359

I'd go for Shimano XT brakes.

cooldad

Bigger rotors will also give you less modulation and lock up easier, generally. Do you need more power or better brakes? The two are not always the same thing.

Vacancy

I need as much braking power as possible in a shorter amount of time.. Would you recommend I went for a slightly smaller disc? Maybe 180mm? Thank you both very much for your replies; and thank you for the image aid, supersonic. I'm gonna go and measure the distance between the two holes, as I'm aware that they can vary in size in that aspect, too. Does it matter what brakes I get, or are all brakes compatible with all rotors, depending on the matter of having the right bracket?

Sorry, what did you mean by modulation? That's not a term I'm aware of. Just tried a quick Google search but can't find the relevant information.

cooldad

How much control you have over the brakes. Not much use if they just lock up at the slightest touch, or you'll be over the bars all the time. Basically how sensitively you can brake.
Rotor size is personal, I manage fine with 160mm each end, mainly fairly natural XC and some trail centres. Nothing seriously steep (or if it is steep, not very long.)
180mm front is fairly common on the front, bearing in mind if you are planning seriously gnarrly DH stuff, you probably have the wrong bike.
A number of people I ride with have XT's as SS suggested, and they are seriously good brakes. Powerful and sensitive.
Just like me.

Vacancy

I see, so by modulation, is this what you meant?


I manage fine as well with what I currently have, but I wanna make some improvements and my brakes are currently terrible, they need a good service and I've been thinking about getting new ones for a while now anyway so I've decided I'm going to get some new ones, just looking at them XT's now, they seem to have a lot of good reviews. M785s is that? A lot more affordable than the Hope equivalents, too.

Whilst I'm at it with the question asking, could somebody fill me in as to what BPC is an acronym for?

Like on the brake lever on this:

cooldad

Adjusting the bite point. Bite point control or something I guess.

The Rookie

You need to be clear what you want/need....on a bike like yours XT brakes with 160/160's would be more than adequate, I can put my (similar geo) hardtail on it's front wheel using the XT front brake with 160mm disc with one finger, you don't need more!

mrmonkfinger

before you swap the brakes, what is wrong with the existing setup?

are they spongy?
do they need bleeding?
do they 'bite' well or have the pads become contaminated or glazed?
maybe they just need a set of new pads and make sure the disc is clean?


if you're dead set on changing, then the current models of shimano brakes get strongly recommended by everyone in the know here

craigw99

but those levers have green on them......

EH_Rob

If you've got some money and you want to spend it on brakes I say spend it. I had Juicy 3's once and thought they were rubbish, so I sympathise.

Given the XC nature of your bike, I would suggest against 203mm rotors - way more than is required I would think. I'd go 180mm front and 160mm rear.

As for the brakes, other manufacturers are available, but Shimano's brakes are the best bang for the buck. I have XTs and they're great, but various folks on here have/have had Deore and SLX and have rated them too.

I've actually got a set of M4s I want to sell if you're still interested in them. The modulation is good on them, but the overall power is not.

Giraffoto

If you want to save a bit of that hard-earned cash, you could try just moving up a disc size (price of disc + price of bracket and bolts) and either getting your LBS to thoroughly service your existing brakes, or sorting them out yourself. If that doesn't do it for you, Shimano Deore and SLX are highly regarded here

M Velo

I have 203mm in the front and 185 in the rear. The braking power has improved but now I can see some flex in the fork, which is due to a bigger rotor I believe. I would say that 185 should be good enough.

If you want to upgrade your brakes then XT is my preference.

Curious Yellow

Put 200mm rotors on an old XC bike as a stopgap for a while.

Oh how people laughed at me. Stopping power was brilliant though!

Feels like it's overkill for anyone on the lower side of 70kg who doesn't do any downhill or reach ridiculous speeds (maybe 50kmph plus?). I'd even question 180s, but to each their own I guess.