Braking power: Rotor size, front vs. back

[dirtrider]

This is true - they stop fast enough the first time - BUT - do they stop well enough after a 1500m of fast decent with lots of hard braking corners....  THAT is the question you need to ask yourself.

 

Bigger brakes work better for longer - but are unneccesary if you don't need the added capacity of the bigger brakes - so despite haveing monsters on one of my bikes, my XC bike runs 160/160 - and that has been enough for me on everything I am willing to take that bike on so far.

 

Ok now I see , so you use your brakes to slow your down going down into the Hell (example) and then they overheat ? Never had that problem before and believe me when I say , I have done a lot of big downhills in the last 20 years . 

[rouxtjie]

I thought a rotor was a rotor was a rotor ..

 

Then I put XT rotors on one of my bikes on recommendation .. Gees what a difference.

Previously where I was running a 180 rotor, It was replaced with a 160 and was 10 times better !

 

It's not all about the size, but about the quality ...

 

Ja ja, and before I get chirped about the size thing ... 

I dont have the biggest boat in the harbour, but I row the fastest .. 

Best I have used...hope floating and shimano ice tech....

[ChUkKy]

I also have 203/180 on one of my bikes.... 63kg.....

 

But slowcoaches like you don't need brakes....

 

I weighed 63kg in Standard 6.

 

My balls have grown somewhat since then

[rouxtjie]

Ok now I see , so you use your brakes to slow your down going down into the Hell (example) and then they overheat ? Never had that problem before and believe me when I say , I have done a lot of big downhills in the last 20 years . 

lol....tell us more about these big downhills

[rouxtjie]

I weighed 63kg in Standard 6.

 

My balls have grown somewhat since then

yoh yoh yoh....so...if that is the case come hit haka with us...

 

Next weekend?

[V12man]

 

My balls have grown somewhat since then

Peas do grow as they get older.... till about 7mm...... 

[V12man]

Ok now I see , so you use your brakes to slow your down going down into the Hell (example) and then they overheat ? Never had that problem before and believe me when I say , I have done a lot of big downhills in the last 20 years . 

Where is the hill in De Hell that needs all this braking?

 

Overheating brakes is caused by a combination of several factors - sheer volume of disk/caliper only slows it down somewhat - the trick is to find the minimum brake size that your combination of braking style/terrain/speed/kit etc will not overheat/stress to the point you lose braking capacity/modulation.

 

For me - on my XC bike that's 160/160 - but my enduro bike has more (came that way) and it works for me to have excess capacity on that bike. (both bikes run guides with the same pads)

[V12man]

To add: bigger rotors not only dissipate heat better, they have more leverage because the contact areas are further away from the rotational centre. Meaning you can stop with less force using a 180mm rotor than a 160mm rotor.

The rotor speed at the pad is also slower because of the bigger diameter - this has a beneficial effect on heat production as well, and thus pad life is extended. Modulation is also improved with the bigger diameter.

[Spoke101]

I weigh 61kg and I also have a 203mm front and 180mm back ......more for unduro riding 

 

 

 

 

But i could probably stop faster than my car if I try hard enough

I think you might be needing better brakes . For your weight a 180 is overkill with good set of brakes.

I weigh roughly the same and if I had a 203 on the front the wheel would lock up with me just thinking about braking.

Good brakes and a 160 is enough to put the back wheel in the air even with your weight behind the saddle. Managing the heat then becomes the problem, thus a 180.

[BaGearA]

I think you might be needing better brakes . For your weight a 180 is overkill with good set of brakes.

I weigh roughly the same and if I had a 203 on the front the wheel would lock up with me just thinking about braking.

Good brakes and a 160 is enough to put the back wheel in the air even with your weight behind the saddle. Managing the heat then becomes the problem, thus a 180.

I run metal pads for that exact reason , not such a big initial bite but more off a ramp up feel .....I love it

[NotSoBigBen]

On my Flash HT I have a 160/140 combination and that works fine for my type of riding, no crazy technical stuff ..... weigh about 75kg's depending when (pre or post pooh). On all my other bikes I have 160/160

[BaGearA]

On my Flash HT I have a 160/140 combination and that works fine for my type of riding, no crazy technical stuff ..... weigh about 75kg's depending when (pre or post pooh). On all my other bikes I have 160/160

Resin pads right?

[V12man]

I think you might be needing better brakes . For your weight a 180 is overkill with good set of brakes.

I weigh roughly the same and if I had a 203 on the front the wheel would lock up with me just thinking about braking.

Good brakes and a 160 is enough to put the back wheel in the air even with your weight behind the saddle. Managing the heat then becomes the problem, thus a 180.

There is a formula for calculating the benefit of a bigger rotor in additional brake force - but it's not huge - like 5 - 10% from memory - if you keep all the other elements the same (caliper/pad/lever) - so no - you won't have problems controlling your braking if you add rotor size only.

 

I have the formula somewhere if you are interested - usually only racing gearheads are interested...

[NotSoBigBen]

Resin pads right?

 

Mmmmm can't say either way but the 'normal' pads the brakes come with?

[V12man]

One of the things that nobody has mentioned is the fact that no matter how good your brakes are, the brakes only stop the wheel.....

 

TIRES stop the bike (and you - assuming you are still on top of said bike) ..... or more specifically the tire/ground friction....  don't forget that as an important element of improving your braking....

 

and also why Enduro/DH bikes run bigger brake setups than XC bikes - because that big aggressive knobbly tire on the E/D bike can generate more braking before lockup than that lightweight low rolling resistance XC tire....

[ChUkKy]

yoh yoh yoh....so...if that is the case come hit haka with us...

 

Next weekend?

 

I dont have the right type of bike for that place, thats like going to a pub with R10 in your pocket.