Results 1 to 7 of 7
  1. #1
    mtbr member
    Reputation: elsinore's Avatar
    Join Date
    Jun 2005
    Posts
    405

    Rush Geometry/ Lefty A2C Question?

    Hi All

    I just purchased a 2006 Rush 1000 frame that I plan on building up. The rush is going to be my XC bike for faster paced days, I also own a Nomad so I am looking for a slackish xc bike.

    I really like the Geo on the rush and I was hoping to slack the bike out about 1 degree of head angle from stock by running a slightly longer fork than it came with. Ideally, I am looking for a 68 degree head angle.

    My question is this: What is the axle to crown height on the Lefty Speed Bonded DLR2, 110 mm that came on the 06' Rush?
    I have heard 470mm and 480mm both on this site. My thought is to run a Reba 120 maxle that has a 493 A2C to get the HA around 68. If however, the Lefty is actually 480 then it looks like I would need a 500mm A2Cfork to slack the Rush out to 68 degrees...

    Thanks

  2. #2
    mtbr member
    Reputation:
    Join Date
    Dec 2006
    Posts
    536
    from what i found from a quick google search waas 468mm, though i'm not 100% sure in your case. Keep in mind though that a reba at 120mm ends up at roughly 505 due to the need to run an external bottom headset spacer to avoid the adjuster knobs on the crowm of the fork hitting the downtube. I know cannondale spec'ed their bikes that way with fox forks and considering RS at 120mm are both a bit taller ac wise and usually sport burlier knobs it will def be an issue without it i believe.

    if you want a ac of 500 go for a 09 130mm lefty pbr. The only one i found was outside of my price range and with the alternative for me being a reba (i wanted a 20mm axle) with the ac of 505 i rather went for a 2010 lefty max pbr at 510 - though it remains to be see how it will work out (it is 10mm more than the max allowed under warrenty i know). It only slackens the bike out less than half a degree as the difference in ac between the lefty 140 and fox 120 with the added cup is only 6mm. I'm not 100% sure that the cup specced on rushs are the same 12mm as the one i got with the 1 1/8 conversion headset from cannondale - but i believe they are identical.

    hope ths help a bit. Sorry that i can't comment on how it rides yet, but there's a guy in the post your rush thread that has put on a 2010 lefy max (140mm) and he seemed to like it quite a bit

  3. #3
    mtbr member
    Reputation: elsinore's Avatar
    Join Date
    Jun 2005
    Posts
    405
    Quote Originally Posted by klinkekule
    from what i found from a quick google search waas 468mm, though i'm not 100% sure in your case. Keep in mind though that a reba at 120mm ends up at roughly 505 due to the need to run an external bottom headset spacer to avoid the adjuster knobs on the crowm of the fork hitting the downtube. I know cannondale spec'ed their bikes that way with fox forks and considering RS at 120mm are both a bit taller ac wise and usually sport burlier knobs it will def be an issue without it i believe.

    if you want a ac of 500 go for a 09 130mm lefty pbr. The only one i found was outside of my price range and with the alternative for me being a reba (i wanted a 20mm axle) with the ac of 505 i rather went for a 2010 lefty max pbr at 510 - though it remains to be see how it will work out (it is 10mm more than the max allowed under warrenty i know). It only slackens the bike out less than half a degree as the difference in ac between the lefty 140 and fox 120 with the added cup is only 6mm. I'm not 100% sure that the cup specced on rushs are the same 12mm as the one i got with the 1 1/8 conversion headset from cannondale - but i believe they are identical.

    hope ths help a bit. Sorry that i can't comment on how it rides yet, but there's a guy in the post your rush thread that has put on a 2010 lefy max (140mm) and he seemed to like it quite a bit
    Thanks, that was more or less what I was looking for. Unfortunately I don't plan on getting a lefty as I already have a nice 20mm front wheel. I had no idea that the knobs would hit the head tube. Is the min. external headset spacer over 10mm of stack height? Do I have to order that part from Cannondale directly? I guess I am pretty set on a Reba or a Minute, and it would be nice to keep the AC height close to 490-500 as that should give me about a 68 degree HA. Sounds like the trick is going to be to find the proper size external Headset spacer.

  4. #4
    mtbr member
    Reputation:
    Join Date
    Dec 2006
    Posts
    536
    the stack height i'm talking about (12mm bottom cup - prob 13mm or 14mm with the bottom spacer attached to the forks steerer) is the headset supplied through cannondale for their carbon frames with integrated headsets. I don't know if any other manufacturers produce compatible headset for your frame with less stack height, but they prob do - any 1.5 (to 1 1/8) headset should do the trick. The Cannondale headset is just a spacer cup that you install a bearing into - so semi-integrated i guess one could call em at the bottom, integrated up top (at least for my carbon frame). They are pretty affordable. I'm not sure there is any min stack height for Rush frames, but iif there is it is bound to be mentioned in the pdf on Rush frames found at www.cannondale.com

    getting the ac to be in the 490-500mm range with a RS120mm fork is prob a no can do (especially the 490 part.. ) due to the adjuster knobs that in all probability necessitates a stack height greater than 5mm with the reba 120 ac at 495mm. The only thing i can suggest is installing the lower part of a 1 1/8 - or 1.5 - headset, putting the fork on the bike and seeing if things are gonna be ok or not - though that would mean you would have to purchase the dam n parts first (so not the best advice i guess). I have no idea how the bottom tube vs knob clearance is - i've just noticed that all Rushes with non-Headshok forks has installed headsets with a bit of stack height, no internal ones - and sadly i have no Reba so can't find out either. I guess you could post a question in the "post your Rush"-thread for a quick an accurate answer as far as how big the clearance is or needs to be. It might be that you don't need a spacer at all and that Cannondale only put it on there to slacken the bike out a bit, but that is just pure speculation on my part.

    my initial plan was to use a set of crossmax sx wheels i had and a RS Reba 120mm with a maxle, but as the numbers ended up in the leftys favour and i also had a lefty wheel i went with the lefty instead. So far so good.

    good luck

  5. #5
    mtbr member
    Reputation:
    Join Date
    Sep 2007
    Posts
    119
    Someone on a local board did a flush 1.125/1.5 (Cane Creak XXcII flush or whatever) and the knobs on his Fox fork wouldn't hit the frame, they would however hit the cables. This is only an issue during a crash or transporting the bike with the handlebars turned 90 degrees.

    -Steve in NJ

  6. #6
    mtbr member
    Reputation:
    Join Date
    Apr 2010
    Posts
    11
    I have a 06 rush. It came with a 100mm R-7 which I swapped for a Fox 120. The cane creek flush headset (like Steve said) works fine w/ my 120 but it does hit the cables and if they werenít in the way (the cables) it would just touch the bottom tube. I've road this bike hard for 4 years and crashed more than a few times, and there are no marks on my down tube so Iím thinking itís a non-issue. I can't tell you the exact angles but I love the set up/ ride position much better than the stock one, fast & fun. I can definitely get more aggressive with the 120.

  7. #7
    mtbr member
    Reputation:
    Join Date
    Dec 2006
    Posts
    536
    great feedback from the last two posters there, so i guess i was a bit too pessimistic.

    and yes, the lefty max pbr 140 equipped Rush works as a charm. A little bit high up front for very steep climbing, but super nice for everything else. Might slap on a low rise bar just to try it

Posting Permissions

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