Chris!

I currently have a shimano 10 speed 11-34 cassette with a tiagra 4700 medium swing derailleur. I wanna switch to the shimano 10 speed 11-36 cassette. Shimano list the maximum sprocket for a 2x set up with that derailleur as a 34 sprocket. I know shimano is usually pretty conservative with there specs, so..... anyone have any experience with this? Or other general thoughts on of it will work?

shelbyfv

No reason not to try it. I've used 32T on 10 speed RDs that were rated for 27 or 28(?). Several variables involved so there is no way to know until you try. Be sure to verify your chain is still long enough for large/large

wipekitty

I agree - give it a go! I successfully used an 11-32 cassette with a 105/5800 derailleur rated for 28.

Definitely keep an eye on what happens when you cross chain (big-big). You don't want to cross chain anyway, and in my experience, accidentally doing it for a couple seconds was not catastrophic. One of my friends had a different outcome.

Sy Reene

I get the 'give it a try' advice, but I suppose the OP would have to factor in whether he can return the cassette from wherever he purchased it and if there'd be an associated cost?

msu2001la

Here's a video of someone running a Tiagra RD-4700 GS with an 11-36T. No idea what front chainring size they're using, as this also plays a role.
I've heard of people using a longer B-screw to keep the pully off the cog when in the 36t cog.

Retro Grouch 

My general philosophy is that, if I already own parts, I'll bolt most anything up and see if I can make it work. If I'm buying parts, I'll always buy components that are supposed to work together.

This is kind of a mixed situation. OP already owns the derailleur but wants to replace his cassette with one that offers an easier hill climb gear. Since it's only 2 teeth out of spec, I'd buy the cassette and try it in a heartbeat. I'm about than 80% confident a little B screw adjustment can make it work so it would be worth the risk to me.

How old is OP's chain? My philosophy is new cogs deserve a new chain. I might cheat on that if my existing chain was pretty new but I'd definitely check the chain length before reading the bike. With 2 additional teeth, you're about 50% needing a longer chain.

Retro Grouch 

You got away with it because your chain just happened to be long enough. The problem comes when your chain is too short. The derailleur arm is the weakest link in the system so it bends into the spokes and it will happen on your first strong pedal stroke. You wouldn't be shifting into the big rear cog if you weren't going uphill so your're going to be pedaling hard.

dedhed

Be careful of what cassette you use. Tiagra 4700, while a 10 speed group, uses the Shimano 11 speed pull ratio on the rear derailleur.

aggiegrads

I would use a 9 speed mountain RD. It easily clears a 36T cassette, and provides a ton of chain wrap for a 2x setup.

I am running 10 speed ultegra brifters with 10 speed 11-36 cassettes and 9 speed XT RD. The combo works flawlessly, because the 9 speed mountain, 9 speed road, and 10 speed road derailleurs all move the amount with the same amount of cable pull. 10 speed mountain is not compatible.

shelbyfv

Unfortunately his 4700 shifters aren't compatible with the 9 speed mtb rear derailleurs. Another good solution lost to progress

Chris!

I'm thinking I'll be ok with the derailleur combo. Chain is original to the 50-34 front crankset. I'm running a 46-30 now. Would that make up for the larger sprocket and allow the same chain? Not opposed to buying a new chain but it's a relatively new bike about 500 miles on it. Dont like to through money away.

Viich

This has no impact on the cassette - the spacing and cog width are the same, just different Rd and shifter.

Retro Grouch 

You've dropped 4 teeth on the front big sprocket and only gained 2 teeth on the rear. Your chain won't be too short.

Miele Man

I've put bigger cassette cogs onto bike for some people who really needed them. When I needed a longer B-screw I often used a dropout adjustment bolt instead as the threading was the same as for the B-screw.

Cheers

BengalCat

If the RD can't handle it properly just buy the Wolf Tooth Roadlink. It's a $20 SIMPLE single add on that will definitely give you what you posted about.

02Giant 

X2.
When I take my road bike to the mountains I swap the cassette (and chain) for a 12-36 and use a Wolf Tooth Roadlink.

MikeyMK

Derailleur drop links are fine for up to about 7-speed with certain aggressive chains, but not so good with 10-speed in my experience.

The problem is that the jockey wheel is so far from the cassette, the chain cross isn't aggressive enough for the next gear to take it. So indexing is ineffective and you find yourself having to go two clicks to engage, and then click back as soon as it bites..

studbike1

I currently run a 34t granny on a derailleur rated for 28t max.

How often do you use your granny gear?

It will definitely work but will make some noise and not be as smooth.