Groupset for roadbike question

Discussion in 'Cycling Equipment' started by Nickldn, Jun 5, 2011.

  1. Nickldn

    Nickldn New Member

    Joined:
    Jun 5, 2011
    Messages:
    13
    Likes Received:
    0
    Hi, I wonder if anyone could give me a bit of advice about which groupset I should be looking at for a bike I'm building. It's the first time I'm building a bike from scratch, so there's a lot to think about!! So far I have a Sigma Nemesis carbon triathlon bike frame, with some Shimano Dura Ace 700C metal wheels. I need a groupset which will work with the Dura Ace wheels (I've been told it has to be 10 speed), but don't want to spend an absolute fortune, so the Dura Ace 7900 is out of the running. I'm seriously considering the cheaper 7800 though, or maybe a lower end model. My question is, would I really notice a lot of difference? The other thing I want to find out is which tooth configuration I should go for on the sprocket and cassette to facilitate road efficient road riding, with not a huge amount of emphasis on steep hill climbing. Any advice would be greatly appreciated. Nick
     
    Tags:


  2. tafi

    tafi Member

    Joined:
    Jul 31, 2003
    Messages:
    1,038
    Likes Received:
    17
    Yes there is a lot to think about. And no matter how much you think about it there is always some small detail which catches you out.
    A couple of points:

    1. Make sure you get cables with your groupo
    2. Check what type of bottom bracket you need. There used to just be two threaded styles (Italian and English/BSA). Now there are also the press fit styles BB30, BB86, BB90 etc.
    3. Make sure the front derailleur is the correct type for your frame. If there is an attachment bracket on the eat tube then you just need a "braze-on" style. If not then you need to be very carefull that you get the right sized derailleur clamp. In correct sizes can cause frame damage as they have to be pretty tight to keep the derailleur in place.
    4. If you are in triathlon, be carefull about your choice of bars and levers. Do you want standard racing bars with road levers? Or do you have bullhorns and time trial bars? If the later then you will need separate bar end shifters and brake levers.

    Now as to choice of grouppo, you'll get pretty much the same performance whether you go for Ultegra or Dura Ace these days. The only real difference is slight changes in style and weight savings with Dura Ace.
    These are really your only choices. If you went for 105 you'd probably be better off, financially, buying a complete bike.
    Be careful when choosing parts since not all the 7800 and 7900 gear is interchangeable. I'm a Campagnolo man myself so I'd have to go and read up (again) about the incompatibilities, but it suffices to say: unless you know very well what you're doing, it's best to get all the components from one model of groupset.
    The mainstay gearing these days is the 11-23 cassette combined with 39 and 53 chainrings. You won't be able to go any faster with another choice of cassette and really if you want to race at a good level, you need to be able to live with a 23 for climbing anyway.
     
  3. Peter@vecchios

    [email protected] New Member

    Joined:
    Dec 30, 2007
    Messages:
    2,111
    Likes Received:
    4
    STI or tribars with bar end shifters?

    Hard to beat a 6700(Ultegra) group and if you need barends, get 7900, no 6700 barend shifters.

    11-23 as has been mentioned.
     
  4. Nickldn

    Nickldn New Member

    Joined:
    Jun 5, 2011
    Messages:
    13
    Likes Received:
    0
    Thanks very much for your advice, it is greatly appreciated!!

    I've done a bit of research and found out I need an English type bottom bracket and a front mech with a 34.9 band on bracket......so that particular mystery is solved. Not sure of the chain length, but I'm sure I can take a few links out if it's too long.

    I've got standard racing bars, as I don't really think I'll benefit from proper tri bars at the moment, so I can use normal levers/shifters.

    Now for the choice of grouppo. I'm really erring towards a Shimano Ultegra 6700. It's a bit cheaper than the SRAM Force and probably just as good. The only fly in the ointment are cheap Dura Ace 6800 parts available on eBay. I figure I could 'build' a 6800 grouppo for £300, which would be a bargain compared to spending £750 on a new Ultegra 6700 (although my bike shop said they'd fit it for free, which is very tempting). I'm a bit sceptical about the condition of second hand bits sold on eBay, they might be fit for the bin.....I'm also not sure how long replacement 6800 parts will be available for.

    A new Ultegra would be the safer option......but sooo expensive compared to second hand bits!

    Incidentally, I've been told that I'll struggle with a 11-23 and would find the combination of 34-50 compact chainset with a 12-25 cassette much more versatile. I might get the 11-23 and then switch to a 12-25 if I struggle.

    Should I spend all my money on an Ultegra, or be brave and go for an eBayed 6800?




    p.p1 {margin: 0.0px 0.0px 0.0px 0.0px; font: 12.0px 'Lucida Grande'}
     
  5. tafi

    tafi Member

    Joined:
    Jul 31, 2003
    Messages:
    1,038
    Likes Received:
    17
    Whether you like it or not, you will need to be able to turn the big gears to keep up (let alone compete) in racing. You will know your tri courses better than I do, but the vast majority of tri bike courses I have seen have either been pan flat or gently rolling. So there is no reason at all why a standard 53/39 crank and 11-23 cassette shouldn't suffice for this. Since there is no need to sprint and probably no long downhills, you may be able to get away with a 12 tooth small sprocket and therefore use a 12-25.

    The whole point of the standard crank is that you will have access to the right combinations of gears on varying terrain at racing speed. If a course happens to be a bit hillier then you will also be able to use a 12-27 or 12-28 cassette with the normal derailleur.

    The compact crank is not designed for racing, but for recreational riding as a replacement for the older triple crank. Recreational riders aren't as likely to use the same big gears required in racing and they also aren't needing to get over long climbs at 20-25km/h, so they can save the pain by chosing a generally lower gear set (smaller chainrings). The only time a compact has been usefull in racing is on particularly hilly courses (I mean big f*ck-off climbs) where climbing speeds are low enough to make it useful.

    In my view, if your aim is competition, it is better to choose a racing crank and swap out the cassette to suit the course, than to hamstring yourself with a compact crank.

    I'm personally no great shakes as a racer but all of my racing and training over the last 10 years has been conducted using a 53/39 (or 53/42 if fit) crank and an 11-23 cassette. This comes down to the simple reason that, if I can't push these gears over the climbs, then there is really no point in me turning up at the start line at all.

    Cue flaming :).....

    As for choice of parts, I would proably go for new stuff. You are new to building up bikes so it is best to minimise the chances of hidden "surprises". Unles you're certain of what you're doing, buying used can end up costing you a lot more in the long run.
     
  6. Peter@vecchios

    [email protected] New Member

    Joined:
    Dec 30, 2007
    Messages:
    2,111
    Likes Received:
    4

    Get a 11-25 cogset, get Ultegra(far better than anything sram), ebay is probably 7800, last gen DA 10s. Not bad stuff but the levers tend to 'eat' der cables...plus no warranty for second hand stuff. If the lever doesn't work, you are SOL.




    p.p1 {margin: 0.0px 0.0px 0.0px 0.0px; font: 12.0px 'Lucida Grande'}
     
  7. swampy1970

    swampy1970 Well-Known Member

    Joined:
    Feb 3, 2008
    Messages:
    10,057
    Likes Received:
    185
    Racing... trainging... it doesn't matter. A gear ratio is a gear ratio. Whatever you need for a given course is what you need for your given level of fitness and your prefered cadence. Maybe an alternate solution would be to go for a chainset that allows the spider to be swapped out between a 130 or 110mm - like the Cannondale Hollowgram or Specialized S-Works.

    Probably the best climber in the world - Alberto Contador. Seen here at the 2011 Giro. Note 34x32. What you need is what you need - Alberto needed that gear. "The compact cranks is not designed for racing" - hmmm, seems as though this one was designed to crush the worlds best.

    [​IMG]

    Peter,

    I've heard that alot about DA7800 levers "eating their cables". I've been running 7800 for the past couple of years on my training bike and it receives next to no maintenance other than maybe one or two washes a year and a chain clean/lube every month or so. No evidence whatsoever that my Dura Ace inner cables have been damaged, frayed, chomped at, hacked up or split when inspected. I was slightly paranoid out this due to the amount of "talk" about this at the local bike shop so I check pretty frequently. The only 'extra' maintenance that the gear system has received has been cleaning out and re-lubing the rear external cable when I inspect the inner cable ends (in the STI shifter) and jockey wheels.

    Have you noticed this problem with aftermarket cables like Gore or with genuine Shimano DA cables too?
     
  8. tafi

    tafi Member

    Joined:
    Jul 31, 2003
    Messages:
    1,038
    Likes Received:
    17
    It didn't take long...

    My dear Swampy, if you had actually read my whole post, you would have seen that I did speak to the use of compact cranks in racing. I was refereing to just the use you describe (big f*ck-off climbs).

    Is it normal in road racing? Absolutely not. That sort of use will occur only once or twice a year. It just so happens to be faster (in this one scneario) to use a smaller chainring and big sprockets.
    What you haven't mentioned is the kinds of compromises which have to be made by the mechanics to allow the use of that gearing. The riders still need a 53-11 or so gear for the descents. You can't get that with a normal compact without compromising the shifting. Jumping from 34 to 53 is a lot to ask of a front derailleur with a capacity of 14, and the extra flex of the larger chainring on the smaller spider doesn't help either.
    Contador actually took a bike change at the bottom of the climb so he could ride a standard crank up to that point and then switch to wall-climbing mode for the Zoncolan.

    If you can afford two bikes, a team car and a helper for that one time per annum when it might be useful then, by all means, go for it.

    As a triathlete, the OP is not interested in climbing the Zoncolan but riding a tri bike course, which is usually flat to gently rolling and not much further than 40km. (If anyone has ridden up the Zoncolan as part of a triathlon then let me know!)

    For most of the flatter to rolling courses a rider on a compact will find themselves needing a chainring in between the 34 and 50 rings for the uphills (which leads to lots of cross chaining to find the right ratios - far from ideal).

    It is true that ratios can be adjusted to the course but (as I said) this is also far easier to do by swapping the cassette than the crank or spider.

    FWIW: I too have seen the cable eating capabilities of 7800 (and its Ultegra and 105 relatives). The rate is probably not really high (so plenty of people have gotten away without it), but certainly higher than it should be. It is one of the more common 7800 repairs.
     
  9. Eichers

    Eichers New Member

    Joined:
    Sep 17, 2010
    Messages:
    541
    Likes Received:
    4
    +1 ... I have not an issue with my 7800 levers or cables either ... sofar and luckily it would seem :)

    Actually, 34 x 32 is slightly lower gearing (depending on crank arm length) than 39 x 36 (which I ride for some hills) .
    Allows you to do higher cadence, which suits me but not all people. Some people prefer to grind (do lower cadence) :)

    Actually, 50 x 11 is slightly higher gearing (depending on crank arm length) than 52 x 12 or 53 x 12 (food for thought) :)


    Shame we can't have a 10/40 cassette x 50T or 48T or 46T (single chain ring). Should be less weight, stiffer crankset, better Q, easier shift control, etc (more food for thought) :)
     
  10. Nickldn

    Nickldn New Member

    Joined:
    Jun 5, 2011
    Messages:
    13
    Likes Received:
    0
    Unfortunately I've had to re-consider my budget again and I think even a second hand eBayed Dura Ace 7800 is going to be a bit too much. So now I'm thinking of an Ultegra 6600, there's still quite a lot of second hand parts knocking around and they all see to be compatible with newer Ultegra 6700 components, so I can upgrade it bit by bit over time. At least that's my theory. I suspect that old brakes, levers and deraillours should still work pretty well, as they seem to be quite durable components. I think the chain and cassette and probably the chainrng/crankset may have to be bought new though, as these are the high wear components. I think I will try to go for a new 11/23 and a second hand 11/25 cassette, try them both on the road and see how it goes. My thinking is to start off with the 11/25 and then progress to the 11/23. The 6700 double chainring sounds like it's a lot more capable in terms of shift quality than the older 6600, so I'll go for one of those too if I can afford it. I can't see the point on spending more on the 7800 as it won't work well with newer 7900 parts and the 'consumables' (chains, cassettes) are so much more expense. I know I should just probably get a brand new 6700 and be done with it, but it's all about having the cash........ Can anyone see any flaws in this plan (apart of course from second hand stuff not working?)
     
Loading...
Loading...