[angelotrek]

i need some advice for my disc brake performance. i'm 245 lbs and don't feel safe going downhill with my stock avid juicy fives 160mm rotors. they also make noise as they heat up. i was told by my lbs to go with a bigger rotor for more stopping power. if this is true what size should i get or should i be looking for a whole new brakeset.

i ride xc with a few steep downhills.
2007 specialized stumpjumper comp hardtail.

 

[lebikerboy]

Going with 8" rotors will get you approx. a 40% increase in rotor size. This will result in a significant increase in braking power and cooling cause of the increased surface area. I'm about 10 lbs. lighter than you and run Shimano XT's with 203 mm rotors. The difference is huge.

Your Juicy 5's are basically the same as the Juicy 7's with out the pad contact adjustment.

 

[angelotrek]

brake rotor upgrade

thank you for the reply. it helps alot. now i'm wondering if i should get both front and rear rotors in 205mm. i noticed that some people use larger front rotors.

 

[crisillo]

I recommend you get a front 203mm rotor for the front... and keep the 160mm rear or upgrade to 185mm.......... since your mass moves to the front when braking, having a 203 rotor in the rear won't really stop you faster unless you are traveling really fast.....

 

[SLX]

Take it easy with the finger pressure till you get used to the power or you will endo.

 

[Djponee]

203mm in the front and 185mm in the back

i've heard that running a 203mm rotor on a hardtail can rip out your dropouts Right out of your frame im not sure if im correct but i heard it on MTBR so...

This actually almost happened to my bike shop owner
He was riding downhill and he braked around a corner to slow before the next descent and his dropouts cracked- he was still able to ride but he was unable to use his back brake

 

[crisillo]

i've heard that running a 203mm rotor on a hardtail can rip out your dropouts Right out of your frame im not sure if im correct but i heard it on MTBR so...

Depends on the frame... it is a bad generalization, but MOST hardtails are not designed for 203mm rotors.... DH hardtails and some HT trailbikes can handle them without issues...just check the manufacturer for that...

 

[brianb00]

I recommend you get a front 203mm rotor for the front... and keep the 160mm rear or upgrade to 185mm.......... since your mass moves to the front when braking, having a 203 rotor in the rear won't really stop you faster unless you are traveling really fast.....

While the physics is correct don't you really generate more stopping force in the rear in order to prevent endo's ? While on a road you could certainly generate more force in the front on dirt it woudl seem dangerous as you possibly lock the front tire.

In the crowd I ride with, disc and rim users, everyone wears out the rear pads first indicating the majoirty of energy is cooked off on the rear brake.

In off road motorcycle racing the front brakes are often backed way off to prevent lock up ,or at least minimize the chance. Why would bikes be different ?

 

[damion]

Wrongo....

While the physics is correct don't you really generate more stopping force in the rear in order to prevent endo's ? While on a road you could certainly generate more force in the front on dirt it woudl seem dangerous as you possibly lock the front tire.

In the crowd I ride with, disc and rim users, everyone wears out the rear pads first indicating the majoirty of energy is cooked off on the rear brake.

In off road motorcycle racing the front brakes are often backed way off to prevent lock up ,or at least minimize the chance. Why would bikes be different ?

most of your braking force is up front. I go through front pads faster than rear, but spend a bit of time BEHIND the saddle, if you know what I mean. Gemini, 8"front6" rear rotor, 230lb rider. Using too much rear brake results in lots of skidding, loss of control, and trashed trails.

To the OP: Start with an 8" rotor up front, and train yourself to rely on it.

 

[adamantane]

your a big dude, just get 203 mm front and back, you'll need the appropriate mounting brackets...

 

[crisillo]

most of your braking force is up front. I go through front pads faster than rear, but spend a bit of time BEHIND the saddle, if you know what I mean. Gemini, 8"front6" rear rotor, 230lb rider. Using too much rear brake results in lots of skidding, loss of control, and trashed trails.

To the OP: Start with an 8" rotor up front, and train yourself to rely on it.

Yeah.. Damion is correct... if you use correct braking technique you should be using the front to stop and the rear to keep the bike inline.... I run 203/180 on my FS and 185/160... and it is better for thetrails too...

 

[brianb00]

Yeah.. Damion is correct... if you use correct braking technique you should be using the front to stop and the rear to keep the bike inline.... I run 203/180 on my FS and 185/160... and it is better for thetrails too...

You guys are good to be able to control the braking that well and not fly over the top or highside. I stopped by two LBS's today and spoke with the mechanics. Seems the replace rear brakes much more frequently than front brake pads. I wonder why the that is ? Given they are using the same pad size and material in most cases.

Brian

 

[Chris130]

You guys are good to be able to control the braking that well and not fly over the top or highside. I stopped by two LBS's today and spoke with the mechanics. Seems the replace rear brakes much more frequently than front brake pads. I wonder why the that is ? Given they are using the same pad size and material in most cases.

Brian

It's because many, many, many MTBers have poor braking skills and use their back brake far too much. If you are braking "correctly" out on the trails, you will burn thru your front pads faster, as others have already stated.

Not a slam here on folks who bring their bikes into the LBS for work, but, for the most part, the people who brake properly also are the ones who do routine maintenance themselves at home - their bikes are rarely at the LBS for routine service (like brake work). This is why LBSs see more fried rear brakes for maintenance.

Cheers, Chris