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Cross bikes - Race vs Slack Angled frames

springtide9springtide9 Posts: 1,731
edited July 2013 in Road buying advice
Firstly, apologise in advance if this seems fairly obvious, but have been caught out before with making assumptions!

Quick question to the Cross people out there....

So looking for a Cross bike.. I see a lot of bikes are defined as having "Slack Angled Frames" which from my MTB knowledge basically means it's a little more upright for going over the rough stuff. I assume that this has a similar meaning on the Cross frames.

My question is the frames that are described as having "Race geometry" - I assume that this means that the frames are not designed with "slack" and have geometry that is similar to a road frame???
Simon

Posts

  • passoutpassout Posts: 4,425
    That would, more or less, be my assumption. Some cross frames seem to be do it all machines - winter trainers, commuters and maybe off road adventure - taking guards and even racks eg Revolution cross bikes. I guess cross racing is one thing you could do on them. Others seem much more focussed on cross racing - steeper / more racy angles, maybe lighter. Basically faster across a cyclo cross course.
    'Happiness serves hardly any other purpose than to make unhappiness possible' Marcel Proust.
  • Monty DogMonty Dog Posts: 20,614
    Whyte Bikes seemd to have pioneered the concept of a slack-angled CX bike and from many accounts the ride is rotten. I have 2 CX bikes plus a rigid 29er - go too slack on the head angle and you'll get front wheel-flop on the tight, technical stuff which can be an issue with some 29ers. I'd stick with tried and tested CX geometry rather than go for some half-cocked solution that some product manager has dreamt-up in order to give niche appeal. I've commissioned a number of custom ti CX frames for myself and others - they get used for racing and all-day, offroad adventures and every bike handles great - Tom Ritchey knows how to design and good frame and I'd trust his judgement everytime.
    Make mine an Italian, with Campagnolo on the side..
  • holiverholiver Posts: 729
    I did some research into angles and geometry yesterday as I was considering a cross bike as a commuter. I looked at the Kinesis Tripster and Pro 6 and Cotic X. The Kinesis frames share geometry (71.5, 73 degrees head and seat angles), with the 6 having a shorter head tube. The Cotic is a little slacker at the head tube (71, 73 degrees) although it has a longer head tube. Overall the Cotic is more compact too

    Not sure how this stacks up to the Whyte bikes.
  • springtide9springtide9 Posts: 1,731
    Thanks... looks like my thinking was correct.

    I am actually trying to avoid getting an upright comfortable frame s I really want it as a decent (tough) replacement for my road bike over the winter months (when I want a bit more traction and not have to worry about hitting hidden water filled potholes)

    The appeal of also taking the bike offroad and maybe (if I ever get around to it)... having a go at a cross event (just to make sure I have something to aim/train for over the winter)

    Unfortunately I don't understand what I'm looking for with geometries and how they make the bike ride.

    Can someone give an opinion about the PX Cross bikes?
    The numbers are for: Small, Medium, Large and Extra Large

    Uncle John
    bike_frame_geometry.gif
    A Head Angle (°) 71 72 72 72
    B Head Tube Length (mm) 110 140 170 190
    C Effective Top Tube Horizontal (mm) 522 542 568 588
    D Seat Angle (°) 74 74 73 72
    E Seat tube Length Centre to Top (mm) 510 540 570 590
    F Chainstay Length (mm) 435 435 435 435
    H Standover Height 780 810 840 880

    On-One Dirty Disco
    bike_frame_geometry.gif
    A Head Angle (°) 71 71.5 72 72.5 73
    B Head Tube Length (mm) 100 120 140 160 180
    C Effective Top Horizontal (mm) 523.5 535 547.1 561.9 575.7
    D Seat Angle (°) 75 75 74 74 74
    E Seat tube Length Centre to Top (mm) 500 515 530 565 595
    F Chainstay Length (mm) 425 425 425 425 425

    Planet X XLS
    bike_frame_geometry.gif
    Head Angle (°) 71.2 71.3 71.5 72.7
    Head Tube Length (mm) 120 133 147 162
    Effective Top Tube (mm) 515 535 553 568
    Seat Tube Length Centre to Top (mm) 510 540 570 590
    Seat Tube Length Centre to Centre (mm) 470 500 530 548
    Seat Angle (°) 74.3 73.9 73.5 73
    Chainstay Length (mm) 425 425 425 425

    If you are stating that the smaller the angle the racer the frame, then it seems that the order is from top to bottom (slackest at the top)

    What I find confusing is that the Orange RX9 is states as being a slack cross:
    http://www.orangebikes.co.uk/bikes/rx9/

    But the angles appear to be less for the RX9 than the PX XLS.
    Simon
  • passoutpassout Posts: 4,425
    Thanks... looks like my thinking was correct.

    I am actually trying to avoid getting an upright comfortable frame s I really want it as a decent (tough) replacement for my road bike over the winter months (when I want a bit more traction and not have to worry about hitting hidden water filled potholes)

    The appeal of also taking the bike offroad and maybe (if I ever get around to it)... having a go at a cross event (just to make sure I have something to aim/train for over the winter)

    Unfortunately I don't understand what I'm looking for with geometries and how they make the bike ride.

    Can someone give an opinion about the PX Cross bikes?
    The numbers are for: Small, Medium, Large and Extra Large

    Uncle John
    bike_frame_geometry.gif
    A Head Angle (°) 71 72 72 72
    B Head Tube Length (mm) 110 140 170 190
    C Effective Top Tube Horizontal (mm) 522 542 568 588
    D Seat Angle (°) 74 74 73 72
    E Seat tube Length Centre to Top (mm) 510 540 570 590
    F Chainstay Length (mm) 435 435 435 435
    H Standover Height 780 810 840 880

    On-One Dirty Disco
    bike_frame_geometry.gif
    A Head Angle (°) 71 71.5 72 72.5 73
    B Head Tube Length (mm) 100 120 140 160 180
    C Effective Top Horizontal (mm) 523.5 535 547.1 561.9 575.7
    D Seat Angle (°) 75 75 74 74 74
    E Seat tube Length Centre to Top (mm) 500 515 530 565 595
    F Chainstay Length (mm) 425 425 425 425 425

    Planet X XLS
    bike_frame_geometry.gif
    Head Angle (°) 71.2 71.3 71.5 72.7
    Head Tube Length (mm) 120 133 147 162
    Effective Top Tube (mm) 515 535 553 568
    Seat Tube Length Centre to Top (mm) 510 540 570 590
    Seat Tube Length Centre to Centre (mm) 470 500 530 548
    Seat Angle (°) 74.3 73.9 73.5 73
    Chainstay Length (mm) 425 425 425 425

    If you are stating that the smaller the angle the racer the frame, then it seems that the order is from top to bottom (slackest at the top)

    What I find confusing is that the Orange RX9 is states as being a slack cross:
    http://www.orangebikes.co.uk/bikes/rx9/

    But the angles appear to be less for the RX9 than the PX XLS.

    That confuses me too. Have a look at the regular kinesis cross bikes too.
    'Happiness serves hardly any other purpose than to make unhappiness possible' Marcel Proust.
  • FransJacquesFransJacques Posts: 2,148
    "I am actually trying to avoid getting an upright comfortable frame s I really want it as a decent (tough) replacement for my road bike over the winter months (when I want a bit more traction and not have to worry about hitting hidden water filled potholes)"

    I'll take you "away from the numbers" before you part with your "pretty green" to buy a bike with "all mod cons" (oops, wrong thread for that) b/c this comment seems to be at the nub of your requirement.

    If you're seeking a road-bike replacement which you can also ride off road I'd stay away from Whyte, older Konas, pre 2010 Spesh Cruxs, and some others too. They all lean towards MTB type handling and several riding buddies were not impressed with the Spesh and Kona. I've never seen a Whyte cross bike in the flesh. Of my two CX bikes, I do enjoy the twitchier one in races.

    One thing I'll say about upright angles/low riding position (as opposed to slack angles/upright riding position) is that you'll enjoy it immensely on-road but you might need to learn how to tame it off-road b/c it could be twitchy & scary at first. But once you master the racey cross bike geo off-road you'll develop a massive grin on your face.

    One big shift over the last 2-3 years is towards lower BBs (i.e. measurement G above). A 7 cm BB drop (vertical distance between BB center and the horizontal line between the wheel axles) is getting more common than a 5 or 5.5 cm drops. A 5cm drop yields a higher BB which is great for clearing obstacles or pedalling around corners but move your center of balance/gravity upwards. Theoretically, lowering the BB should lead to more stable handling which can offset a very twichy front end. So you end up with a quick-steering bike that's not too scary to ride off-road and carves corners well (but w/o pedalling to the extreme).

    Just my random thoughts on off-road geo.

    Oh, and lastly, go carbon!
    When a cyclist has a disagreement with a car; it's not who's right, it's who's left.
  • springtide9springtide9 Posts: 1,731
    "I am actually trying to avoid getting an upright comfortable frame s I really want it as a decent (tough) replacement for my road bike over the winter months (when I want a bit more traction and not have to worry about hitting hidden water filled potholes)"

    I'll take you "away from the numbers" before you part with your "pretty green" to buy a bike with "all mod cons" (oops, wrong thread for that) b/c this comment seems to be at the nub of your requirement.

    If you're seeking a road-bike replacement which you can also ride off road I'd stay away from Whyte, older Konas, pre 2010 Spesh Cruxs, and some others too. They all lean towards MTB type handling and several riding buddies were not impressed with the Spesh and Kona. I've never seen a Whyte cross bike in the flesh. Of my two CX bikes, I do enjoy the twitchier one in races.

    One thing I'll say about upright angles/low riding position (as opposed to slack angles/upright riding position) is that you'll enjoy it immensely on-road but you might need to learn how to tame it off-road b/c it could be twitchy & scary at first. But once you master the racey cross bike geo off-road you'll develop a massive grin on your face.

    One big shift over the last 2-3 years is towards lower BBs (i.e. measurement G above). A 7 cm BB drop (vertical distance between BB center and the horizontal line between the wheel axles) is getting more common than a 5 or 5.5 cm drops. A 5cm drop yields a higher BB which is great for clearing obstacles or pedalling around corners but move your center of balance/gravity upwards. Theoretically, lowering the BB should lead to more stable handling which can offset a very twichy front end. So you end up with a quick-steering bike that's not too scary to ride off-road and carves corners well (but w/o pedalling to the extreme).

    Just my random thoughts on off-road geo.

    Oh, and lastly, go carbon!

    I think you know exactly what I want. I'm also happy if the bike is a little twitchy off road... seem to have much more fun on an old school MTB than on a modern FS XC, even if I do end up crashing when getting a little carried away!

    The only bit you've missed is what are the options (rather than what to avoid)... how do the people you know rate the Carbon PX CX bikes? They are cheap for a carbon cross, and I'm guessing PX didn't design the frame, but the question is how do they ride?
    Simon
  • passoutpassout Posts: 4,425
    Planet X have a a good rep for cross bikes as far as I can see. I did look into it as i was going to get one but I needed a frame that took full guards too, so not for me. Otherwise proper handling, fairly race focussed, cross bikes - the Uncle John is an exception to this & is more of an all rounder. There is a review of sorts on their website somewhere.
    'Happiness serves hardly any other purpose than to make unhappiness possible' Marcel Proust.
  • Monty DogMonty Dog Posts: 20,614
    My mate has both PX CX disc frames - he likes them both but they're not as quick as my CX bike! The DDisco is less race oriented - more of a trail / adventure bike than the other. Either would make a good road / training bike. I agree with FransJ comments on getting used to the handling - the fast steering means you can whip through the technical stuff and really put a grin on your face. I ride technical singletrack through the trees - I miss the line and it hurts - it's completely different from riding an MTB.
    Make mine an Italian, with Campagnolo on the side..
  • FransJacquesFransJacques Posts: 2,148
    MD, what is your frame?

    I have a Van Dessel FTB and a Giant TCX - the TCX is the slacker one, on the FTB I can crit race b/c it's so fast. Faster steering/handling CX bikes would be:

    - Focus carbon (72 HA, have ridden one)
    - 'Dale SuperX (have raced one once, not as fast as my FTB)
    - Van Dessle FTB (laser fast steering)
    - Cube (42.5 stays and a 72 deg HA, not ridden one)
    - Orbea Terra carbon (short stays 73 deg HA, short front-center, did a short ride around a parking lot)
    - Kuota Kross (very short front center & WB, never ridden)
    - X-Night/X-Fire (short stays, 72 deg HA, have ridden & liked but steering isn't the fastest)

    Above was the data I had captured in a geometry table I used for my carbon bike purchasing project. I'd get on the web and do some research (like you did with PX above) then ride some for sure. Since trail is the big determining factor and that's not an easy number to find, the proof is in the riding.
    When a cyclist has a disagreement with a car; it's not who's right, it's who's left.
  • springtide9springtide9 Posts: 1,731
    Thanks all. A decision has been made......

    Planet X XLS (pre-order)

    I looked at the others, but most were out of budget (C2W) - if you wanted disc brakes (which was a must for me). The endless loop appeared to keep leading back to the XLS.

    It seems most of the cycling companies are making slack "cyclo-x commuting bikes" on their lower end range, with more race specific frame designs on their higher end models.

    The other bike that looked very tempting was the Kinesis Crosslight Pro 6, but as you have to pay full price when using a C2W voucher, it was the same price as the XLS. I also prefer SRAM to Shimano although not enough to swing the decision on it's own (I have a "105" bike and have no complaints), and assume the Carbon will be lighter (to offset the disc brakes!)

    Thanks for the help.
    Simon
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