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  1. #1
    hors category TandemGeek's Avatar
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    Forking With Our Calfee

    Back in May I mentioned I'd picked up a Reynolds Ouzo Pro Tandem fork on close-out with the intention of seeing how using the 55mm Reynolds on our Calfee might alter the handling vs. the 44mm True Temper Alpha Q X2 that it was originally fitted with.

    For those who haven't followed my writings over the years, I've had a strong preference for tandems that are designed for use with the shorter rake since first making the shift from a '96 Santana to our first custom Erickson in '98. While I've jumped on different tandems with different rake forks over the years I've never had the opportunity to truly go back and revisit the 55mm rake spec to see if perhaps my preferences and riding style may have changed such that the longer rake & resultant shorter steering trail might not be attractive once again. I say once again only because it seemed like a good choice for a first tandem... but then again, perhaps even that was an illusion.

    Anyway, I finally found got around to cutting the steerer, pressing on a base plate and setting the Reynolds Compression Plug into the steerer. In regard to the latter, I must say that the compression plug is pretty slick and a lot easier and faster to work with vs. the True Temper approach of using an insert that must be set in place with epoxy and then cure for 24 hours.



    Anyway, as I said, getting the Reynolds from the box onto the tandem was a very quick and easy task. More importantly, now that the fork is all set with the base plate and compression plug in place swapping out with the Reynolds for back-to-back comparison rides is about a 5 minute task: 2-4mm stem bolts, 1-5mm fork pre-load bolt, and 1-5mm brake caliper fixing nut are what hold everything together.

    On to the first ride impressions....

    I was immediately surprised by how much trouble I had making the tight right turn and descending the driveway as we left the garage: I was basically over-steering the thing. Interestingly enough, I'd become so accustomed to the heavier slow-speed steering of the 44mm rake forks that the very light touch needed for the 55mm fork with it's shorter steering trail made me quickly realize that I would, in fact, need to be on my toes for this first time out on the different fork.

    In general, the steering definitely felt finger-tip light at slow speeds and while climbing and stayed centered without much attention while cranking along on the straight and narrow. While this sounds like a good thing, I found it to be exactly what I grew to not like about our '96 Santana Arriva... in a word: a sluggish. Now, one man's sluggish is another man's easy to guide / low task-load so as always handling qualities remain very subjective. In fact, for those who time-trial on tandems I suspect the shorter steering trail would be a very good thing IF the qualities remained unchanged by the far-forward / weight over front wheel captain's TT posture.

    As for steering it was a mixed bag. The Calfee handled the big sweeping turns at 40 mph with ease and lots of confidence, carving a lovely arc with almost no effort to initiate and complete or transition right to left through the turns. However, the very tight 90 and even tighter 110 turns that we take fairly hard were a wholly different experience in that instead of simply thinking "lean, carve and exit" as we negotiated the turns it was "LEAN, steer, steer, steer and exit" and even then the apex of our turns was well outside the norm and in one case we even found ourselves on the centerline of the road we were turning onto.

    Interestingly enough, what I also found to be quite different was the lack of the very plush feel that I've always enjoyed on the Calfee. In fact, I felt like I was back on the Erickson as we crossed the usual rough patches at a couple bridges and some new road / old road transition points: lots of sharp road jolts and a buzzy feel were almost always present.

    Finally, because the Reynolds fork has a somewhat normal crown to drop-out length of 395mm compared to the Alpha Q's 374mm, the tandem's attitude was a little more upright. Therefore, and since I didn't change any of our touch-point positions (i.e., set-back, reach, etc.) even though we retained our normal riding posture we were both technically riding a bit more upright on the Reynolds fork. I'm not sure how much that might influence how we felt on the ride so perhaps in the future I may include a test ride where I reset all of the touch points with the trusty old Fitstik so that we truly are in the exact same riding position on the Reynolds as we are on the shorter Alpha Q.

    More to follow as we do log a few more miles on the Reynolds fork. However, at least for tomorrow's ride with friends over on the other side of town, the Alpha Q is back on so that we re-calibrate and compare what we experienced today with what should be a more 'normal' set-up on our Calfee.


  2. #2
    PMK
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    I read through your write up quickly.

    Not having tested this stuff on a tandem, but rather on other vehicles, it all sounds similar.

    You might also find, the light steering with reduced trail and additional required steering input to get the thing around a corner, may have a point where the front will seem to turn in well. After this point during turn in, sometimes these setups will begin to tuck under, knife or whatever you prefer to call it, basically falling to the inside of the corner. On the KTM, this then immediately resulted in a snap to oversteer, which I doubt the tandem could accomplish. The tandem though may wind up the chassis like a spring, that, when unloaded, induces more handling woes.

    On the other hand, you did mention raising the front. This would alter the headtube angle, slowing the steering, and adding trail back in.

    So next thought, since you know the forks effective dimensions, do you know the Calfee headtube angle at a given fork dimension. Some simple sketches will see if the trail was changed causing the lighter steering or if the wheel was "flopping" more from the altered fork length.

    PK
    2006 Co-Motion Roadster, flat bars, discs and carbon fibre fork, size 22 / 19
    2006 Ventana ECDM full suspension mountain tandem
    Some single bikes and a couple of KTM's
    And most important, someone special that enjoys them with me (except the KTM's)

  3. #3
    hors category TandemGeek's Avatar
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    Quote Originally Posted by PMK View Post
    On the other hand, you did mention raising the front. This would alter the headtube angle, slowing the steering, and adding trail back in.
    One of the math major can check me here, but I'm pretty confident the length of the wheelbase (~175 cm) makes any change in effective head tube angle that would result from the 2.1 cm difference in fork length negligible.

    In fact, and again this is just a guess, I suspect the implications are probably on par with something like switching from a 23 mm tire to a 25 mm front tire, i.e., vis-a-vis changes in pneumatic steering trail.

    Of course, it's really a moot point. The Calfee's geometry is what it is and the various carbon production forks are what they are so if you are swapping out forks you get what you get... and that's what I'm evaluating here: the influence of a 55mm Reynolds Ouzo Pro Tandem for on a Calfee originally designed around an Alpha Q X2.

  4. #4
    PMK
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    FWIW, I did a quick Cad sketch and the headtube angle changed .547 slacker with the longer fork based on a 1750mm wheelbase and 73 headtube initial headtube angle. Installing the longer fork would place the angle at 72.453.


    With both forks set at a 73 headtube angle, the trail dimensions are 61.00mm with the True Temper Alpha Q2 374mm crown to axle and 44mm rake. The Reynolds comes in at 49.49mm trail with 395mm crown to axle and 55mm rake.

    Installing the longer fork at the new 72.453 headtube angle changed the trail to 52.99mm.

    If you know inflated tire dimensions for various sizes these could be plugged in. I based everything off a front and rear tire OD of 700mm giving me a level ground/terrain basis.

    Not disputing any of your comments, just took a moment to see exactly what is happening. Please others, if possible, please check my numbers.

    PK
    Last edited by PMK; 08-02-09 at 06:43 PM.
    2006 Co-Motion Roadster, flat bars, discs and carbon fibre fork, size 22 / 19
    2006 Ventana ECDM full suspension mountain tandem
    Some single bikes and a couple of KTM's
    And most important, someone special that enjoys them with me (except the KTM's)

  5. #5
    PMK
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    So what was your final outcome, old fork back on, new fork on the shelf.

    PK
    2006 Co-Motion Roadster, flat bars, discs and carbon fibre fork, size 22 / 19
    2006 Ventana ECDM full suspension mountain tandem
    Some single bikes and a couple of KTM's
    And most important, someone special that enjoys them with me (except the KTM's)

  6. #6
    hors category TandemGeek's Avatar
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    Quote Originally Posted by PMK View Post
    So what was your final outcome, old fork back on, new fork on the shelf.
    The Alpha Q was put back on for last Sunday's ride with friends and is still on the bike. I'll likely leave the Alpha Q on for our Saturday ride and then put the Reynolds fork back for another 'back-to-back' comparison during our Sunday ride. After that the Reynolds fork will stay on for a couple weeks so I have a chance to fully acclimate to it and then I'll switch back to the Alpha Q to evaluate the differences once again.

    As to the future and which fork will remain on the Calfee, it will depend on what comes out of the entire evaluation process. Moreover, it may be that we'll use both forks to leverage their strong suits for different types of riding. In the back of my mind I envisioned using the Reynolds fork in conjunction with our credit card touring configuration -- Tubus rack w/Ortlieb panniers and mud guard -- to leverage the shorter steering trail for better straight line stability / less reactive steering / reduced captain task load. We'll see....

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