arny56

Hi all, new here so please let me know if this isn't the right place to ask this.

I'm considering buying a new Giant Escape RX0. I like the bike but think I will have trouble with the gearing because of my bad knees and some short steep hills on my daily workout.

The bike is equipped with Shimano 105 derailleurs and 34/50 compact crank and a 10 speed Tiagra 12x28 cassette.
I know I can swap to a 12x30 Tiagra cassette fairly inexpensively but I don't know if the bigger cog will work with the 105 rear. I can't find a 105 cassette bigger then 12x28 in Shimano's catalog.

Anyone have any experience with this or perhaps another suggestion?

Thanks!

cxwrench

It doesn't say anything more on the spec sheet than '105', but looking at the photo i'd say it's the newer 5700'A' cage derailleur which will indeed work w/ the 12/30 so i'm betting you'll be fine...but i'd have someone at the shop take a look at the derailleur cage and confirm.

bikemig 

Also since the bike is new, you could ask the shop to swap out the rear cassette and derailleur. A deore 591 (which costs less than the shimano 105) will allow you to run a 32 or, I believe, even a 34 tooth on the rear.

You might also want to think about a different bike as it sounds as if a triple makes sense given your knees and the hills you ride.

arny56

Great cxwrench, thanks for the response! I may try to have the shop include it with the sale :-)


Thanks for the suggestion bikemig. I actually started out looking for a triple but they are hard to find in a flat bar bike with decent parts. Seems the market is going to compact doubles now :-(

NJgreyhead

My new Specialized Roubaix, w full 105, came with a 12-30 cassette (even tho the spec sheet lists 11-28). So apparently 30t is fine for the 105 rr der.

bikemig 

Depends on which 105 RD the bike comes stock with; short or medium cage. Shimano's specs say the medium can handle up to 28 teeth but these are conservative: https://www.shimano.com/publish/conte...-.rd_road.html.

cxwrench

The 'new' 5701 derailleur has a max cog size of 30, and has sort of a medium cage to wrap a little extra chain. The 5700 SS & GS both are limited to a 28 according to spec.

deep_sky

The 5700 gs can run a 30t just fine. You have to put the B screw out quite a bit, but it shifts great. This is just my experience, but I have been running once since my previous derailleur got taken out by the chain imploding in March of this year(not recommended during a ride, a lot of hassle to have to stop and shorten the chain every mile or so as another link breaks and hope you make it to an LBS before you run out of chain). If you can get the new 5701, that should work too.

NJgreyhead

Sheldon Brown wrote that Shimano rr ders could handle 30t even tho Shimano said 28t was the max. So on a 2007 bike, 105 rr der, I replaced a worn 12-26 cogset with a 12-30 with no problem. I really like the increased range for a compact double.

NJgreyhead

d_s, why did the links continue to break?
TIA.

cxwrench

Sheldon's site is not always correct...it will work on some bikes but not all. Directly related to derailleur hanger length.

arny56

Well, I certanly wasn't expecting this big of a response, and no flame wars! This really is a great forum.
Thanks for all the helpfull and informative feedback.

deep_sky

Unbeknownst to me, a pin was working it's way out, and when I started climbing a steep gradient (16% if I recall correctly), the chain skipped badly, and we speculated that the pin worked its way so that half the link was undone, and the chain got torqued by the pin being half out and many links were twisted before the link with the pin half out gave way. All happened so quickly. Luckily a friend with me had a chain tool, and we limped to the next town which had a bike shop to buy a chain at. Otherwise I would have had to walk a very long way back to the car.

Had nothing to do with the derailleur I was running at the time (it was an old 5503 derailleur with a longer B screw in it to allow the top pulley to clear the 30t cog), just an unfortunate and odd circumstance that ended up destroying the chain, bending the inner plate of the derailleur cage, and bending the hanger. I was able to run a limited selection of gears after we bought a new chain, but we didn't have time to properly size it or any way to fix the derailleur and hanger, so I had to be careful for the rest of the ride. The next day I hunted down my current derailleur, installed it, and realized that the hanger was damaged and the hanger tool could not get it back to straight. Had to hunt down a hanger (this is a 2004 Specialized Allez pro) and managed to procure one. Hell of a weekend

surreal

OP: before you spend extra money, try the stock gearing. 34x28 is a crazy low gear. You can always switch to a bigger cassette if it doesn't work out, but at least give the stock gearing a try?

arny56

Thanks for the suggestion. The reason for my concern is that on bad days, when the wind is against me, I currently need to use a lower combo to keep my knees from complaining. Admittedly this is with my 32 lb comfort (?) bike which I'm sure isn't the best of climbers. Guess I'm just being cautious about my purchase.

ThermionicScott 

+1. The 34x30 combo won't be much lower, about 2 gear-inches. Might want to consider a triple if your knees are bad enough.

HillRider

Uhhh, 34x28 isn't at all "crazy low" unless you are on the roster of a ProTour team. Come to my area and I'll show you hills for which 34x28 is marginal to inadequate for mere mortals.

surreal

"arny56
Junior Member

Join Date
Jul 2013
Location
Midwest..."

Arny is from the prairie, not the alps. Regardless, 34x28 is low. It's about as low as a traditional road group gets. If one really, desperately needs something lower than 34x28, one ought not be looking at 105-equipped bikes. FWIW, mortals ride SS in Pittsburgh, so...

deep_sky

I love my 26x30 low gear (for double digit grades, of which there is no shortage of here), and would never give it up so I can look pro. I'd prefer to keep my original knees.

surreal

That's cool; to each his/her own. But, with a 26x30 low gear, you're either riding non-road stuff, or modified road stuff. (Even folks who rock triples are running a 30t granny stock; obviously, the 74mm bcd allows smaller stuff, but you'll never get it that way from Shimano, Campy, or SRAM on a factory crankset.)

I'm not telling the OP that s/he doesn't need a gear lower than 34x28; I'm just saying that s/he oughta try the stock set-up before deciding. I think that's just simply practical advice. The super-low gear ratios are definitely en vogue these days, but they don't work for me at all. I'm definitely fat, lazy, and non-pro-looking, but spinning super low gears around here just doesn't work for me. So, why not try before preemptively replacing the cassette?

deep_sky

Nope, pure road riding. I have bad knees courtesy of bad genetics, and grinding away at a 12% grade at a low cadence is just going to bring pain, not make me any stronger or better a cyclist. I don't know what your terrain is like where you ride, but around here it is hilly, even mountainous in places. Only people who got the luck of the draw genetically or who race ride standard doubles, and most people who aren't on triples have large cassettes with their compact double. I am not suggesting that the OP run out and buy a triple then modify it as low as can be done (24t), but 34x28 for someone with bad knees and steep hills in their daily riding, I would definitely think about going to a bigger cassette first, then if that is not low enough, get a triple. 34x34 would require an MTB derailleur, but it would be plenty low unless the OP does longer climbs on the weekends than what they do in their daily commute.