6" vs 8" rear rotor?- Mtbr.com
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  1. #1
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    6" vs 8" rear rotor?

    I'm sure this topic has been beat to death but I can't get the search function to cooperate today. What are the pros/cons of using an 8" rear rotor over a 6". I'm building up a Kona Coiler and have two Hayes 9 brakesets. One set is on my current Hardtail which has 8" front and rear the other set is an 8" front and 6" rear setup. My Coiler build is getting pretty heavy but I don't want to sacrifice performance to save weight. Which should I use?

  2. #2
    Portland, OR
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    use an 8" up front and a 6" in the back. thats the way I run mine.
    Ibex bikes

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  3. #3
    Gnarbot rider
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    go 8 in front and 6 in back. ive seen 8s in the rear, and recently i saw a guy bend his like a taco, a rear 8 sacrifices too much ground clearance
    "Who wants a body massage?"

  4. #4
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    6" is probably the best. The front wheel does most of the braking so an 8" rear won't improve things much. I run 8 and 8 on my RM Switch but that's because it's my do everything bike and I like have the 8" rotor when I'm hopping around on my rear wheel. For general freeride the slight improvement in braking isn't likely worth the cost, weight, and ground clearance sideeffects.

  5. #5
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    BAH - especially if you DH, get that 8 - runs cooler!!


    If you dont wreck derailleurs, you wont have a prob with the disc!

  6. #6
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    You can always split the difference and run 7" rear setup. Get a little bit of weight savings and a little bit bigger rotor.

  7. #7
    TNC
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    Couple of options. If your bike is over 40lbs. and mainly used for DH or shuttled runs then you'd probably benefit from the 8" in the rear. But unless the terrain is consistently steep with lots of traction, the 6" rotor is usually enough. Even when my bike was 41lbs., I ran the 6" in the rear with EBC "red" pads, and they gripped like crazy on the rear. The red pads wear quicker than my standard Hayes pads, but they have a high friction design that works amazingly well. Even at a place like Moab where you get some steep downhill runs with a ton of traction on the rock there, I still had to be careful of rear wheel lockup with 2.5 tires. I don't use EBC red pads in the front with the 8" rotor as it is too strong IMO.

  8. #8
    conjoinicorned
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    i can lock up my 6" rear so easily, an 8" would be a waste and probably harder to control. the vast majority of braking comes from the front.

    i suppose it runs cooler with an 8", but i've never had a problem on 10 000' steep descents on a 43lb bike, so 6" is good enough that way.
    what would rainbow unicorn do?

  9. #9
    my girl rides also
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    I was running a 6", and moving up to a 7" in the rear made quite an improvement, without locking up. I may go 8" before too long.
    Moving to Montana soon, gonna be a dental floss tycoon.

  10. #10
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    What is the real weight savings here anyway?

    I have an 04 coiler with 8 inch rotors front and rear, but I am considering swaping the rear back to a 6 inch until keystone opens again.
    It's not a good ride if you don't scare yourself at least once.


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  11. #11
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    What is the real weight savings here anyways?
    It's not a good ride if you don't scare yourself at least once.


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  12. #12
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    Weight savings? You're talking about a half of a handfull of papers clips. Take a gulp of water from your camelback and you've saved just as much weight.

  13. #13
    TNC
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    Wrong!!!

    Quote Originally Posted by Seanbike
    Weight savings? You're talking about a half of a handfull of papers clips. Take a gulp of water from your camelback and you've saved just as much weight.
    You must stop for a pee break before you're awarded any true weight savings.

  14. #14
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    Quote Originally Posted by TNC
    You must stop for a pee break before you're awarded any true weight savings.
    Exactly how I felt, thats why I have 8" rotors front and rear. A little weight savings isn't worth losing braking power.
    It's not a good ride if you don't scare yourself at least once.


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  15. #15
    [email protected] NYC Freerider
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    8 in the rear is good---not really for more power, but because a larger rotor runs cooler. after a couple of trips to the mountain, my rear 6 inch rotor(hayes) would start turning a light blue and after that, a darker blue, and my rear brake would start feeling sketchy. switched to 8 and the problem stoped. And no, I wasnt holding my brakes the whole way down . 6 inches deff does the job and if thats what you currently have, stick with it. if your buying new tho, get 8.

  16. #16
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    Quote Originally Posted by drum714
    What is the real weight savings here anyway?

    I have an 04 coiler with 8 inch rotors front and rear, but I am considering swaping the rear back to a 6 inch until keystone opens again.

    prob 100g per rotor weight difference between 6 and 8"

  17. #17
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    Different perspective.....

    I ride my Heckler on some DH, but mostly trails. I was running 8/6 like a lot of you, but I switched to 8/8. Mostly because of my weight being 250lbs. I felt better rolling rocks and getting a little more stopping power when I was just using the rear....Avid mechs btw

  18. #18
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    Quote Originally Posted by claycooper
    prob 100g per rotor weight difference between 6 and 8"
    Yeah sound about right...the only things different are the rotor and the little adapter that goes between the frame and the main caliper unit. I'd say it's an extra 10g in the adapter and 100g for the rotor. Just picture an 8" rotor and then imagine how much lighter it'd be without the outer 1" all the way around.

    Decline Mag said like 6mths back that Push Industries was coming out with some Ti rotors that are like 1/2 the weight and don't need special pads or anything because of some cool coating.

  19. #19
    Mileage Junkie
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    6 in the rear for me......

    I run 6's in the rear all the time for my DH-type rigs. I'm 145 pounds though, and never shuttle the bike anywhere really.

    Just from riding XC so much, the rear brake mainly steers you through a turn (creates a pivot point). If you lock it up, the 8 vs. 6 thing doesn't even count though, a locked wheel is a locked wheel.

    80-85% of the braking forces go to the front wheel, so run an 8 there, and for most people, I'm guessing a 6 is probably plenty. Never had a cooling issue, but if people are posting it, then maybe that's something to consider if you are a heavy DH'er.

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  20. #20
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    Quote Originally Posted by TNC
    Couple of options. If your bike is over 40lbs. and mainly used for DH or shuttled runs then you'd probably benefit from the 8" in the rear. But unless the terrain is consistently steep with lots of traction, the 6" rotor is usually enough. Even when my bike was 41lbs., I ran the 6" in the rear with EBC "red" pads, and they gripped like crazy on the rear. The red pads wear quicker than my standard Hayes pads, but they have a high friction design that works amazingly well. Even at a place like Moab where you get some steep downhill runs with a ton of traction on the rock there, I still had to be careful of rear wheel lockup with 2.5 tires. I don't use EBC red pads in the front with the 8" rotor as it is too strong IMO.
    great advice...I would like to add if you are under 160 or ride stuff that isn't to steep (long steep runs not the occassional) then go for 6" front and back
    the trick is ENJOYING YOUR LIFE EACH DAY, don't waste them away wishing for better days

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