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3292 Views 3 Replies Latest reply: May 21, 2012 11:04 PM by MotiveForcer
giloren Rookie 3 posts since
Jan 30, 2012
Currently Being Moderated

Apr 26, 2012 8:28 AM

Help Please: New Components Question

I am upgrading the components for the first time on my Giant Defy Advanced 4 2011. 

I am 6 foot 5" tall and 220 lbs. and I ride 25 to 45 miles every time on mostly flat terrain in South Florida with occasional rides over the 1 mile bridge with high elevation increase.  I want maximum speed with the mix of new components and my budget and taste calls for the Shimano Ultegra 6700 Group Set.

I found a great deal online, however, I am being asked a few questions I don't understand when trying to choose the components I'm ordering.

1.  Cassette type:  11/23 OR 11/25 OR 11/28 OR 12/23 OR 12/25 (Which one should I get and what does this mean?)

2.  Front Derailleur:  Braze on OR 32mm Clamp or 35mm Clamp (Which one and what is the difference?)

3.  Bottom Bracket Cups:  English Thread OR Italian Thread (Which one and what does this mean?)

4.  Crank Set:  175mm 39/53 is what I was told to upgrade to...not sure that affects the above one way or another?


Thank you for the assistance in advance!!!!

  • Colbagger Rookie 2 posts since
    May 9, 2012
    Currently Being Moderated
    1. May 9, 2012 10:24 AM (in response to giloren)
    Help Please: New Components Question
    1. These are the number of teeth on the smallest (11) and largest (25) cogs on your back wheel. Smaller is for higher speed, largest is for steeper hills. The smaller range (say 12/23) gives you a very close set of ratios which is nice for group riding or racing. If you want to understand more about gearing check out this site:
    2. This is determined by your frame's down tube. For braze on the tube has a little tab just above the chain set. For the others it's the diameter of the seat tube.
    3. Again, your frame determines this. The threads are different, the obvious difference being the the English thread is left handed on the RH side.
    4. See 1. There are two issues here. The length of the crank and the number of teeth on the rings. 175mm is pretty much the standard length; some shorter people (not you!) and those who pedal fast tend to go for shorter cranks. Longer than 175mm is getting into oddball territory and pricing. For the ring sizes there are two basic set ups:39/53 and small variations thereon or 34/50 and variations. The latter is called "compact" and is used in hilly country so given your location and desire for speed I'd go with their recommendation.
  • MotiveForcer Community Moderator 448 posts since
    Jul 9, 2007
    Currently Being Moderated
    3. May 21, 2012 11:04 PM (in response to Colbagger)
    Help Please: New Components Question

    Tell me Giloren,

    How come you bought a bike with components that needed new components a year later? Did you buy it used? That would be a good reason. If a shop sold you a new bike that was not dialed in I would ask for a different set up and at a discounted price. It is their job, in my opinion, to dial you in in the first place.


    I agree that the longer crank arm (175 in this case) is the way to go for you at your height. I would no way recommend the compact drive for your flat landing riding and in fact if you haven't done so already consider getting a 53/42 set up.  (Sorry for the lateness of this response. The last three times I tried to log on to active there was some sort of glich.) Why a 42?

    Well, the biggest hill you ride isn't even a hill really. I have not been on that bridge but my guess is that you can get up that hill without going to the easiest gear.  So as Colbagger mentioned you want a tight block in the rear (say a 12/23 instead of a 12/25 or 27) so that each shift is smooth and drops right into that sweet spot.  I've noticed that when shifting from the big ring (53) to the smaller ring (39) that it usually takes two shifts of the rear deraileur to get to that sweet spot.  This happens when shifting up to the big from the small as well. With a 42 only one shift to get dialed in is necessary.  (On Brown's site you will notice that, in effect, three teeth on the front chainring equals about 1 tooth in the back.)


    Around here in SE Michigan we certainly don't have any mountains but we do have some significant hills.  Stronger riders ride up them in their 53 but they approach "crossing over" in the rear and many of them ride a 12/25 in the back to avoid using their front shifter.  It appears that stronger riders here who have a 39 don't use it much.  I have a 42 and I use it. As it is a closer configuration than a 39 my chances for dropping a chain are less too. I've made the suggestion to several riders who were opting for new chainrings to consider getting a 42 instead and everyone who did so loved it.  Only one guy swapped back and that was on the bike he took out and leaves in Arizona for long mountain rides.


    When I rode to LA from Marin two years ago I rode my 53/42 and had only a 12/25 cassette for a the climbs in the Big Sur and some switch backs on day three and a long 7 mile climb that seemed to go forever. I admit, on that one long climb if I had one more gear I would have used it but I was fine in the 42/25.  I swapped back to the 12/23 (I actually also use an 11/23 most of the time) upon my return and didn't regret having that 42 at all while in the hills around Marin or on the coast ride.  (One of my bikes came with an 11/23 and I got used to it. I can ride the 42 down to the 12 without crossing over as it happens. I don't think I'm a sprinter enough to require a 53/11 for sprinting but it works for me.)


    Note: Crossing over is when you use your big (hard) gear in the front and your big (easy) gear in the rear or vice versa with small and small. In general this should be avoided. It puts a sideways torque on the chain and is as a result, less efficient and wears (stretches) your chain prematurely.



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