RobertMillar84

Looking for some second opinions... I'm going on a cycling trip in the Alps in a few weeks time. Was looking to give myself a slightly easier lower gear for climbing, without having to fork out for various parts. I'm running an 11-28 just now with a shimano 105 RD 5700 rear mech, on a compact front. But I notice I can now get a 12-30 tiagra cassette and was wondering if I could get away with running this cassette on my current rear mech - which technically states a 28t is the max. However, I've noticed my b-screw can still be turned in quite some way, which I'm thinking would give it some more capacity?

However, when I asked the mechanic at my LBS about this the other day, he said it wouldn't work, the way the rear derailler and hanger would need to be angled would mean there was less contact with the chain on the cogs and the shifting would be poorer. I can accept the shifting may be slightly poorer.. but was thinking it wouldnt be so bad that I couldnt live with it, if it gave me that lower bottom gear. I also appreciate some people will say the difference between the 28t and 30t is minimal and not worth it.. but I'm thinking over a week of climbing in the Alps every day it may just make a difference, marginal gains and all that!! Plus it would just give me that bit more piece of mind if there was a lower gear to go into if need be.

So, would do people think, is my LBS just covering themselves and going by the book? Or would this change more than likely be OK?

Thanks in advance.

BykOfALesserGod

Trek specs 12-30 Tiagra cassettes on one of their 105 bikes, the 2.3, so if they could make it work then so could you and your wrench.

https://www.trekbikes.com/us/en/bikes...d_1_series/2_3

Mike F

My bike came with a 5700 long derailer and a Tiagra 12-30 stock. I switched back to an 11-28 because I missed the 11 going down grades. I would definatley switch back if I was lucky enough to ride the Alps

RobertMillar84

Mike F, yes I am very lucky to be cycling the alps I had a look at your road bike, its actually running the new 105 RD 5700-A rear mech.. which can take 30T cog max, mine is the 2011 105 RD 5700, which has a stated max of 28T. My question is, can I still get away with running a 30T on this.. I know what shimano are saying, but are there not usually some tolerances with these things?

BykofalesserGod, trek don't seem to be specifying what rear mech they are using with that one.. but I wouldn't be surprised if it was the same as above.

Guess I can only try it and see if it works.. but anymore views would be welcome

rdtompki

Without knowing any of the specifics (age, fitness, etc.), just put on Deore RD and whatever cassette strikes your fancy. Your going to the Alps and RD are relatively inexpensive. You'll need a new chain of course.

revchuck 

I don't know where you live, but in the US the Tiagra 4600 RDs are in the $40 range. I put one on one of my bikes to go with the 12-30 Tiagra cassette, and it worked like a champ. This is what I'd do rather than come up with a fix that might work.

storckm

I would think you can get away with it. You might not be able to use your small chainring with the smallest few cogs, but other than that, there shouldn't be a problem.

shelbyfv

Ribble has the cassette for $25. I use one with a 6603 RD which has the nominal 28t max. Works well.

RobertMillar84

storckm - glad to see there are still some mavericks left out there! intrigued as to why you say I might not be able to use small-small combinations though? I expected big-big might be a no-no, but I tend not to cross chain like that anyway.

ericm979

You may or may not be able to do it. It depends on your frame's derailleur hanger geometry. The only way to find out is to try it.

Make sure that your chain is long enough to go over the large chainring and large cog. If it isn't and you accidentally shift into that combo your ride will be over. It's better to have the chain a little loose in the small-small combo. That just makes noise but doesn't break things.

Homebrew01

Makes sense to me.

ColinL

I wouldn't bother for 2 more teeth.

david58

That was my approach as I prepped for a major climbing ride coming up in a week or so. I bit the bullet, put on the RD, and had an 11/34 installed (50/34 on the front, compact double). Did it two weeks ago, and finally got to assault a couple of big climbs today - one I made it .6 of the mile to the top before blowing up - I doubt I would have made 100 yards on my 11/28, I needed the 32 off the bat, and blew up in the 34.

Based on an earlier ride (Tour de Hood) with 8500' in 70 miles, I found I was too buried in my 28 cog to feel like a mere 2 additional teeth would do the trick for me. But all I need to do is buy a wrench and I can swap the cassette back out to my reg'lar one, and with the long RD I will always have the option to use the bail-out cassette.

Commodus

It will almost certainly work.

merlinextraligh

I've used an 11-32 with a long cage 105 RD. Odds are pretty good it will work acceptably well.

I would echo EricM's advise on chain sizing. You don't want to be tearing off your RD in the Alps.

nhluhr

"Technically" it wouldn't be quite right but there is a very good chance it will work well enough. I setup a lady with an 11-32 a couple weeks back on her 105 GS derailleur (she already had a triple setup with 12-28 or something). Had to turn in the B screw all the way but it worked really well.

I think the main factor is specifically where your rear derailleur hanger positions the derailleur.

RobertMillar84

Thanks everyone for your responses so far.. I've actually just now tried this combination on the workstand and to be honest it seems to be working fine, haven't had it on the road yet but I have no reason to think it won't work now. Obviously I'll try it out on the road quite a bit before I head to the Alps The gears are shifting just as well as they did on the 11-28 set up... only thing I may do for extra piece of mind (as someone pointed out) is lengthen the chain slightly, as when its in the big big combo it does look a tad stretched out. I have no plans to ever ride in the big big but hey you never know I guess and really don't want to take any chances whilst I'm out there!

speedwobbles

The trip sounds awesome. Where are you going?

RobertMillar84

Staying in Bourg D'Oisans at the foot of Alpe D'Huez. Just going to get in as many legendary Tour de France climbs as my legs will take me over

echotraveler

Are you already using a compact crankset?

Get a new cheap RD. and the cassette... Why not get 11-32?

HokuLoa

Sounds fun! I've heard both positive and negative results with 12-30 and no long cage change. For the minimal cost of a new RD why not splurge for an optimal Col setup? You will probably spend more on lunch one day there...

speedwobbles

I just rode through there yesterday. Let me know if you have any questions about the area.

volosong

I slapped an Ultegra 12-30 on my 7900 Dura-Ace compact drive train. Other than re-setting the "H" and "L" screws, no modifications were needed. I think the D/A RD is classified as a mid-length cage, definitively not a long cage like the Tiagra/105/Ultegra triple RD is. Even though several shops say it won't work, that my shifting will be crappy if it shifts at all ... it works just fine for me; I don't race nor ride in pacelines. The shop that gave me a BG fit last week actually removed one link in the chain and warned me very sternly to never go "big-big", and showed me why. I'll need to stay out of the two big cogs when on the large chainring, but that is fine as the only times I use the largest three cogs is when climbing, and then I'm in the small chainring. Before hunting down and securing two of the Ultegra 12-30 cassettes, I purchased a Tiagra 12-30 off eBay to test it out on the bike stand. Anybody want to buy a very lightly used Tiagra 12-30 cassette?

To those who say two teeth won't make a whit of difference ... you must be very young and very strong .... or very stupid or macho. There is a difference...a large difference.

ColinL

I might be stupid, but I'm not that young or macho.

I'm from Kansas. I rode a lot for a week in Colorado quite recently on vacation. I had 11-23, 11-26 and 11-32 cassettes with me and a chain long enough to use all of them. Unfortuantely, my Rival RD would not accept the 11-32, so I presume it's a short cage. (It was supposed to be mid cage.) I rode my FIL's bike with the 11-32 though, so I know what it was like.

The 26T was very much worth having over the 23. (As was the 32. ) 23 to 26 is 4.5 gear inches.

In the case of a compact crankset, a 12-30 has a mere 2 gear inches less than a 12-28. It will barely matter, and it's not worth doing.

RobertMillar84

Ok.. so there seems to be an intriguing split in opinion.. so, bearing in mind I will be cycling over 2 possibly 3 cols a day for over a week, who thinks going from a 28T to a 30T is a complete waste of time and who thinks the marginal gain would help?