Results 1 to 10 of 10
  1. #1
    mtbr member
    Reputation:
    Join Date
    Nov 2006
    Posts
    189

    Sag and Geo on Mach 5

    Hi All,

    I've been absolutely in love with my Mach 5, but have some things I'd like to improve. Mainly it's XCish riding position and feel. I'm 6' tall and ride a Large with 90 mm stem. Forks is Pikes at 140 mm.

    I mainly run sag in 28-30% range (16-17 mm). Is it really a good idea to run 30-35% sag to lower the BB a bit and slacken the HA?

    The shock is RP23 2009 HV non-boostvalve. I have put a shim in the outer sleeve b/c otherwise it would blow through travel too easily under my 210-220 lbs with some occasional bottom out. Now it seems to be better and maybe there is some space for dropping the pressure.

    I fully realize that the proper answer is Mach 5.7 but this ain't going to happen for a while to my dearest regret

    There's another way of slackening the HA - try to use longer forks like Reveleaions 150 and I know some guys even run Lyrics, but I feel it's going to set me up in the clouds and will negatively affect cornering which is probably not the best thing to do. Am I right here?

    Any opinions/recommendations are more than welcome.

  2. #2
    Paterfamilias
    Reputation:
    Join Date
    Feb 2006
    Posts
    417
    http://www.pivotcycles.com/bike_deta...etry_chart_tab

    Sag is 30% check out the interwebs the link above shows the geometry for the Mach 5.

    I would stick a FOX 32 RLC 150mm fork on that, and it would stop that XC feeling you talk about, if you got a tapered fork you could run the Cane Creek XX 44 headset and that would lift the fork up a little more a slacken the angles just a little more.

    We have tested the Mach 5 with a 150mm and it rolls and corners great. Long steep climbs is when you will notice it change a little as it could get a little light on the front end with the slightly higher BB.

    If I didn't work here I would have hung on to my Mach 5 and done the above changes. But of course I made the change to a Mach 5.7
    "The face of a child can say it all, especially the mouth part of the face".
    Jack Handy

  3. #3
    mtbr member
    Reputation:
    Join Date
    Nov 2006
    Posts
    189
    Thanks for you reply,

    One more thing - what 150 fork are you talking about here? AFAIK Revs should be a little taller than Fox 32?

    I sometimes do feel perched on the bike - I have rather long legs for my 6' height so saddle needs to be high-ish.

    EDIT: Just realized that I have a real chance to get knowledge from the source!!

    The geo numbers - they're true for 30% sag at the rear, but what sag should I have at the front to actually have 69 degree head angle and 72 seat angle?

    I was assuming that 30% as well (both sides have 140 mm) but then the front end seems low.

  4. #4
    Paterfamilias
    Reputation:
    Join Date
    Feb 2006
    Posts
    417
    http://www.foxracingshox.com/bike/11/forks/32_FLOAT

    I would roll with that fork had I stayed on my Mach 5 this year.
    "The face of a child can say it all, especially the mouth part of the face".
    Jack Handy

  5. #5
    mtbr member
    Reputation:
    Join Date
    Nov 2006
    Posts
    189
    That's cool, thanks!

    What sag should I be running on the forks to maintain the stated geometry?

  6. #6
    Paterfamilias
    Reputation:
    Join Date
    Feb 2006
    Posts
    417
    Well, I would run the recommended air pressure for your fork and your weight always.

    The changes we have talked about above were to help, or change the XC feel, so if you run a taller fork (150mm) then you will change the geometry by a half degree and raise the BB by about a 1/4 of an inch. That would slacken it up so you don't have that XC feel you mentioned above.
    "The face of a child can say it all, especially the mouth part of the face".
    Jack Handy

  7. #7
    mtbr member
    Reputation:
    Join Date
    Nov 2006
    Posts
    189
    I never run recommended pressures b/c they're way off quite often. For RS forks for sure. I've been using sag as a measure for the last 5 or 6 years and have always been fine.

    Difference between 25% and 30% sag on a 140 mm forks actually is 7 mm which is what I will get by switching from 140 to 150 and maintaining the sag - when adding extra 10 mm mind that 2.5-3 mm of them will be sagged.

    So I still have the question - what sag do I need to run on 140 mm forks to maintain the stated bike geometry with 30% sag at the rear?

  8. #8
    Paterfamilias
    Reputation:
    Join Date
    Feb 2006
    Posts
    417
    Agreed on the RS, however on every FOX, I'm generally spot on within 5 PSI.

    The Geometry chart is for a 140mm fork.
    Most every chart is stagnate before any compression, so I'm not sure I can answer your question.
    "The face of a child can say it all, especially the mouth part of the face".
    Jack Handy

  9. #9
    mtbr member
    Reputation: bauhaus's Avatar
    Join Date
    Feb 2007
    Posts
    289
    I run a RS Revelation U-Turn. It is adjustable between 120 and 150 mm. I use the adjustment a lot. I keep it totally open for most of my riding and lower it on the climbs. I do not know if it is my riding style, or what, but the front end on my bike always wanders, no matter how much I scoot up on the seat. Being able to lower the fork really helps.

    The RS Revelation is much better than the 2007 Fox Talas that I had on it before. I could never get full travel on that fork. I have heard that the new Fox forks are very nice, but I have no experience with them.

    Also, to help with the XCish feel, you can run a shorter stem and wider bars. I run a 70 mm stem and 711 mm bars and it has worked really well.

    That being said, I am probably going to switch to a Mach 5.7 or new Turner 5 Spot once I get a chance to demo them. I would love for the Mach 5 to be a little more plush and a little more slack. From what I have read, the Mach 5.7 covers the plushness part of the equation and the 5 Spot might just cover both. Cannot wait to try them out.

  10. #10
    My other ride is your mom
    Reputation: Maadjurguer's Avatar
    Join Date
    Mar 2008
    Posts
    4,407
    Perfect post and perfect timing....I was just going to do a search on how to mute some of the XC feel on my 09' Mach5....and then I read this.....need to go sell some plasma so I can get that 150mm fork....

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •