Hi Guys,

I am going to purchase a SRAM Force Groupset to replace my out of date Shimano Tiagra Groupset that came with my '09 Cannondale CAAD 9/6. I need some help on the sizing. I know cranksets come in like 170mm or 175mm sizing and say like 39/53 GXP and such. What is all that? Braze-on or Clamp-on Front Derailleur? Teeth in cassette? I am at a total loss on what to buy. The frame is 58cm. I am about 6'1" 165lbs. I have no clue if you need other sizing information about my personal self. Just looking for some information on what is right for my bike. Remember, SRAM Force Groupset!

This is my bike's specs.
https://www.bikepedia.com/QuickBike/B...&model=CAAD9+6

EDIT: To save anyone new to this post from reading everything that has probably been answered, this is my final post below to catch you up!

"Okay guys, here is where I am at. I am looking at a SRAM Force groupset. The Crank is Carbon Compact 50/34 172.5mm. My current Tiagra Crank is a Standard 53/59 175mm.

From what I understand in making this change, I am decreasing the size of my crankset which means I will be able to spin slightly more. Also, compact cranksets are more suited to climbing, or should I say, make climbing slightly easier.

My last question is about the cassette. I currently have an Ultegra CS-6500 12x25 cassette. The Force groupset comes with an OG 1070 cassette and is available in multiple different 'teeth count' I should say? Would switching from the 12x25 I have now to something different offer lower gears for climbing?"

Thanks,
deCycles

I would say ride more, read more before you make a wholesale change. What's your current gearing? What's your terrain like? What's your fitness level? How old are you? What are you trying to get out of cycling?

For example 53/39 cranksets certainly seem out of favor for recreational cyclists, but if your terrain is mild or you're very strong, then you might be ok. My mid-30's son is fine with a 53/39 and a 12-28 cassette for climbing, but he's very strong. I'm late 60's and I've got a triple with a 12-30; that's lets me do 100K rides with 5K-6K of climbing. No way I could do that with a double (well, I could use an 11-36 cassette, but the spacing is awful).

Provide more information and enjoy the thread, but most of this you've got to work out for yourself.

I'm 20. Have been on 3 cycling trips. 2010 Seattle to Los Angeles, 2011 Bloomington, IN to East Coast and Virginia, 2012 Sanfrancisco to Bloomington, IN. Raced solar bikes in Japan. Been on numerous cycling events such as the Hilly Hundred, RAIN, Crane Cyclefest, etc.

I am in what I consider to be peak shape. I am a huge fitness buff and love being in shape. The terrain is generally good quality roads. They plan trips so we get the best roads while throwing in scenic stuff too like bike paths etc.

Trust me, I'm ready for a new set. My current gearing is what I understand to be an 18 gear range. It's a double front and a cassette with 9 teeth rings.

My first instinct was that your question proved you weren't ready to be spec'ing a group this way.

Yet you have plenty of cycling experience. So the question is, why are you asking strangers? Either you should have opinions based on your experience, or if yet unsure, at least well formed ideas. I suggest either make your own decision based on experience, or find a local fitter, discuss your likes and preferences, then get good fit advice from someone who at least can see you on a bike.

While I consider myself to yes, have a fair amount of cycling knowledge, I still want to hear other people's opinions. The specifics is where I become useless haha.

Based on an instructional YouTube video, I know understand that based on my height I would probably want a crankset that is 170mm or 172.5mm. Can someone break this down for me?

SRAM Force GXP 170mm 50-34 Crankset Black Rings

170mm is the length of the crank arm?

What is 50-34?

There are no rules, only BS. Everybody is different, and while short people may have issues with cranks that are too long, taller people choose cranks by preference. As a rule spinners prefer shorter cranks, and guys who push bigger gears tend to prefer longer cranks, but the general doesn't always apply to the specific.

After all those miles, YOU should have an opinion about what you like and don't like about the existing bike. If you don't have dislikes that you can specifically identify, then simply duplicate what you have in the new group.

Just look at your current parts and see what you have.. Some are set (like if you have a braze-on FD) but the rest are personal choice. Frankly if you have to ask these questions you probably should not be piecing a group out for yourself.

Crank length, compact vs. standard, and cassette choice are things no one can answer for you, but we could give some more useful advice if you tell us what your current parts are and how they're working for you. For example, do you want lower gears or tighter spacing between gears?

50/34 = compact crank. The number of teeth on the chainrings. 53/39 is a typical "standard" crank.

If you don't know if your frame takes a braze-on or clamp style front derailleur, it's time for you to take your bike into your favorite Local Bike Shop. Tell them what you are looking to do and let them make recommendations. Another plus, they can install what they sell.

Crank arm length is relatively insignificant, unless you're very short or very tall (and you're neither).

170 mm is crank arm length.

50-34 means that the big ring has 50 teeth and the small ring has 34 teeth. (You do understand the relation between the number of teeth, cadence and speed, I assume?)

GXP is the bottom bracket design. This is a complicated question but I believe that your CAAD9 has a standard 24 mm threaded bottom bracket shell, which means that GXP is the correct choice (as long as you're going with SRAM.)

This is my bike's specifications everyone.

https://www.bikepedia.com/QuickBike/B...&model=CAAD9+6

In terms of what I don't like, really it is not like I don't like anything in particular. More so, I want to get rid of this Tiagra, upgrade to lighter carbon fiber parts. Something that will give me even more power. Possibly more gear range for climbing easier and pulling harder on the flats? I also am more of a spinner, I like a relatively high cadence, more momentum I feel.

The bikepedia link photo shows what looks like a clamp-on rather than braze-on front derailleur. You should confirm this by looking at how the derailleur is attached. If it has a band that circles the seat tube, it is clamp-on. If it mounts to a tab on the right side, it is braze-on.
A 170 or 172.5 crank would be fine for your height. If you are a high cadence spinner, the shorter 170mm might be a better choice.
The standard 53/39 chainrings vs. compact 50/34 is a HEATED argument trap. If it were me and I was looking at faster cadence AND more power on climbs, MY choice would be the compact because it has lower gearing for climbs and if you spin higher rpms, the 50 tooth will give you higher rpm on each of the cogs. An 11 tooth on the first cog on the cassette will make up for the 3 teeth you loose on the front. In the old days, 14t was the smallest cog, so you needed a larger front chainring. Not so much anymore.
EVERY one of these suggestions has room for opposing argument, which is why people are hesitant to jump in with quick suggestions. Component choice is a bit science and a bit art.

Which I completely understand. Everyone is different, but it is opinions like this that I am looking for. It helps me see what other people like in a specification-nitty-gritty type science I am not familiar with.

Here's a question for you. How much do you want the following:

- higher gears for flats/downhills?
- lower gears to spin up long/steep climbs?
- tight gear spacing?

Take 10 points and divide between these three categories.

Also, is there a specific reason why you want to go with SRAM Force? And have you ever tried electronic shifting?

Power comes from you, not the bike. Weight reduction under a pound or even two is inconsequential, as it only affects rolling resistance, which itself is a small factor, and has to be taken as a percentage of the bike's weight with you on it. Some cranks may transmit power slightly more efficiently, but again a very small effect. The easiest thing you can do for more power/efficiency/comfort is get properly fitted - not frame size, as you already have the bike, but seat height and fore-aft, distance and height of bars, bar profile and width and possibly get some coaching.

If I were you I'd go out and ride a SRAM equipped bike before you make a wholesale swap of components. It's good stuff- but different. Some like it- some don't. If you wish to upgrade from Tiagra, you may want to stay in the Shimano camp.

Weight savings? Not much when you compare the upper end components between brands.

If you think that Tiagra groupset is outdated, you might as well send it to me for disposal

Also, I'd second the suggestion to try a SRAM bike before you buy one, a club-mate of mine had a bad experience with SRAM stuff on a new bike, not because it's bad-quality but because he preferred the shape and shifting action of Shimano brifters. As I recall, it was a big enough deal that he spent quite a bit of money on Shimano kit.

a chainring tooth count.

Okay guys, here is where I am at. I am looking at a SRAM Force groupset. The Crank is Carbon Compact 50/34 172.5mm. My current Tiagra Crank is a Standard 53/59 175mm.

From what I understand in making this change, I am decreasing the size of my crankset which means I will be able to spin slightly more. Also, compact cranksets are more suited to climbing, or should I say, make climbing slightly easier.

My last question is about the cassette. I currently have an Ultegra CS-6500 12x25 cassette. The Force groupset comes with an OG 1070 cassette and is available in multiple different 'teeth count' I should say? Would switching from the 12x25 I have now to something different offer lower gears for climbing?

That would of course depend on what the difference is. Larger tooth count on largest cog would of course be a lower gear. Google bicycle gearing and educate yourself.

I wasn't aware my question was that complicated.. I simply asked if a cassette different than 12x25 is more suited to climbing. I am aware when it comes to cassettes the first number is the number of teeth on the smallest cog and the second number is the number of teeth on the largest cog. What is adding or taking away teeth from the cogs going to do? It seems like a simple question which is why I am asking bike enthusiasts such as yourself for assistance, if I wanted to become an expert on the topic I wouldn't be here asking for help.. For instance, my options are OG 1070 Cassette: 11/23, 11/25, 11/26, 11/28, 11/32, 11/36 or 12/25, 12/26, 12/27, 12/36.

Your question is not sensible, as if the cassette is different one way it will not be offer lower gears, another way it will. Even if you ask which cassette(s) would be more suited to climbing than 12-25, it's not the question but the answer that is complicated. I directed you to a search because all we would do here is repeat what is in those references.

Although larger rear cogs (or smaller front chainwheels) give you lower gears you have to understand gearing and how the gears relate to each other in respect to gearing range, overlap, and shifting patterns in order to make decisions about what combo will work for you in particular. You can choose how much you want to learn - we can only guess what you need to know and how you need to learn it. If someone here wants to tutor you or act as a consultant on gearing that's fine, but you still need to learn how low a gear you need, how wide a range you want to tolerate, and then look at the compatibility between the derailleurs, cassette, and chainwheels.

"Use the Force, Luke." This graphical gear calculator is pure Art... and a pleasure to use. Here's a hint: Open several instances of this link, and use them to compare various cassette-chainring combinations -- nothing beats the added oomph of the interactive.

Here's a link to your planned setup (34/50 + 12-25). Have fun!

THIS. This is extremely helpful! It really shows me the difference between a 12-25 cassette and a 12-27. Thank you so much it makes so much more sense!

I'll probably go with the 12-27 since it offers a slight increase in revolutions when climbing. I wish someone would've mentioned that sooner.. Oh well!