I'm currently riding a 2014 Trek 1.2 with SRAM PG-950 rear cassette, Shimano Sora shifter and Sora rear derailleur. I'm trying to work out some incremental improvements/tweaks to my ride and want to upgrade to 11-speed. Looking at probably the Shimano 105 ST-5800, but want to make sure it fits my hub. I know I need the derailleur and shifter as well, just want to make sure the cassette will fit before I take the step

What hub do you have? If the cassette has a 1.85 mm spacer you are probably ok. 11 speed needs a 11 speed hub. you can run 8/9/10 speed on 11 speed hub using spacers

Your 9 speed hub will probably not be able to accept an 11 speed cassette- it's too wide.


You can upgrade to 10 speed 5600/5700/6600/6700 with just a new cassette and shifters. You can change the RD if you really want to, but not necessary.


In any case, neither an upgrade to 10 speed nor the more expensive change to 11 speed would necessarily make you any faster. Definitely better shifting feel and feedback, but that's about it. If you're in a place where the bike is actually holding you back (e.g. weight, wheels) then you would be better off saving up for a new bike.

+1

Frame. Wheels. Even brakes. But 9 speed is not that bad, I'd change that last.

Even if your hubs are wide enough and you do upgrade to ST-5800, they're not compatible with the Sora derailers. It's true that 11 speed needs a wider freehub, but that's not necessarily a good reason to get 10 speed parts over 11 speed parts if you plan on eventually upgrading wheels. You can run a 11 minus 1 cassette with a couple shims on a 10 speed freehub, similar to Sheldon's procedure for "9 of 10 on 7" for short 7 speed freehubs. It's not a particularly useful way to upgrade if you intend on staying 10 speeds, but it can help you carry over parts when upgrading incrementally.

Incidentally, my opinion is if any part of the bike is holding you back, it's your fit, tires, or having inappropriate gearing choices for your strength and terrain.

The upgrade from 9 speed to 11 speed is not incremental. Most of the time you are looking at a full groupset and new wheels. 10 speed is less of a stretch if you can acquire last generation Tiagra shifters that will work with your current derailleurs

I have the same bike with the stock wheels. Trek told me the hub is 8/9 speed compatible only.

BTW, I have a bike with the 105 and love it! I was intrigued by your question so I contacted Trek once I read your post, hoping it would be easier to do than get new hubs or wheels. My 1.2 has a triple up front and it is awesome even with the Sora.

Kind regards,

Oshkosh

Well, actually it's 8/9/10-speed compatible but that doesn't help the OP if he really want to go to 11-speed.

alcjphil phrased it extremely well; "The upgrade from 9 speed to 11 speed is not incremental." It can and will be expensive.

Why? What do you expect to gain by going from 9 to 11 ?

For the vast majority of riders, going for 9 to 11 is just taking money out your pocket with no real return.

Mechanical Design on 11s not there yet. what gearing is your cassette 11-32 12-24

why go to 11 cogs in the rear? there is no real world advantage, and you will need to change your entire drivetrain and the shifters too... even the front chainrings and crankset will need swapped out to use the 11 speed cassette....
my advice... DON'T Do It! Fix what you have, and RIDE MORE.

Last generation Tiagra (4700) don't work with older RDs. They require 11 speed compatible RD.

Shifting is better than older 10 speed though, more cable pull per gear change.

Agree.

Just to note that front chainrings will be fine - no need to swap them.

Assuming you use the same gear range (11 - 32), all 11 speed does over 9 speed is, give you 1 tooth jumps for the 4 smallest cogs (11, 12, 13, 14) rather than for the two smallest cogs (11, 12) with the 9 speed. If you want more closely spaced gearing, you could always stick with 9 speed and go with a 12 - 23 or 12 - 25 cassette to get smaller jumps between cogs.

This is one of those things where it really only makes sense to upgrade when your drivetrain wears out, or of you are thinking about buying a new bike.

++Probably 95% or more of the people obsessing over number of speeds, weight, stiffness or "upgrading" to a higher model component would be better served by just addressing things such as the fit of the bike or simply riding more instead.

Tiagra 4700 is current generation. Tiagra 4600 was the last generation and would work just fine with the OP's derailleurs

By last you meant previous, and I thought it was the last out of production, i.e. the current.

As long as the OP doesn't make a mistake, it's all good.

Does the 10 Speed cassette need a 1.0 mm spacer? Also, could my Sora accept the ten speed cassette? Do I need a different chain?

Just pondering the possiblity.

Kind regards,

Oshkosh

So Job giving you a Big Bonus to burn through ASAP?

Is it of your concern?

You can remove one cog and one spacer and run 11 speed cassettes on a 8/9/10 freehub. Gives you an extra click on the low end but otherwise functions fine.

Easiest way to go to 11 speed is sell the bike you have and get a different one.

If you want to upgrade what you've got, there are plenty of options.

What's your budget?

If it were me, I'd go:

ST-5700 shifters, used 7800 Dura Ace front and rear derailleurs, and some kind of upgraded crankset with an external bottom bracket.

Those changes would sharpen up your shifting a lot, give you the contemporary under the bar tape shift cable look, and lighten up the bike -- it looks like the cartridge bb and crank are probably anchors. the FC-7800 is really an amazing crankset, and they're not expensive if you look around a bit.

You are right, my post was ambiguous, I should have specified that I was talking about Tiagra 4600

How do you expect the bike will be improved by adding 2 cogs. Said differently what is your goal. You will spend a fair amount of money but the bike may be no more rideable than it is.