Upgrade groupset or not worth it???

New cables is never a bad idea.  Good ones too.

Agreed no need to upgrade from the Tiagra, make sure the pivot points are all clean and lightly lubed, then fit new cables and outers, if you've got cash to splash try Jagwire pro gear set, make sure you've got a decent pair of cable cutters too.

Strongly second trying the cables first. Also want to throw in that if you've found you like the frame, keeping it and not jumping horses is worth more than you'd think. Last point, if that's the Sora with the thumb buttons to shift smaller, how convenient those are/aren't to you might be a factor to consider. If I'm off by a year well ignore me.

rb982 wrote:

Great advice thank you! I have Mavic Ksyriums - not sure if they are 11 speed compatible? I will consider the Tiagras aswell and see what pops up on ebay. Yes, I do have the thumb shifters to gear down - what do you mean by useful or not these are to me? Excuse my lack of knowledge - do the Tiagras and 105's not have thumb down shifters? Thanks again for your help

Ksyriums will be 11 speed so all good there.

For Tiagra and 105 (and possibly the current versions of the lower level groups) the thumb shifter is replaced with a second lever behind the brake lever. Makes it easier to shift down from the drops but slightly harder than a thumb shift if you're wearing thick gloves. 

Shimano 9 speed groupsets have had the second lever instead of the thumb button for a good number of years now and even the current 8 speed Claris shifters have the same setup.

Shimano SP41 outer casing and Fibrax stainless slick inner wires would be my recommendation. Avoid teflon coated cables, it comes off the wire and slowly gums up the casing. And check there are no places where the cable might be dragging.

If you're looking at replacement shifters you might find lots of perfectly good Sora 3500 sold secondhand as many people don't like having 'merely' 9 cogs when their mates use 10 or 11.

105 (5700 10sp and 5800 11ps) and Tiagra (4600 & 4700 10sp), Ultegra and Dura Ace all have the cables routed under the handlebar tape.

Like current 105 and upwards, 10sp Tiagra 4700 has a different amount of cable pull per shift to 4600 and lower groupsets so you would need to replace your rear derailleur. With 9sp 3500 & 4500, 10sp 4600, 5600 & 5700 it should work fine.

Just check your new wheels are 11-speed compatible - I'm sure they are but if they're not then you can't run 105.

It will be cheaper to buy a new bike, but you will notice a difference between 8 year old Sora and modern Tiagra/105 if you choose to upgrade the components. Much lighter shift, less lever throw, and better braking. Overall much more responsive and comfortable. And on the subject of comfort, if you're happy with your frame and position, try and stick with it. There can be a lot of faff and expense getting your position dialled in to a new frame. 

Personally I'd look for nearly-new Tiagra on eBay as it's the time of year people are buying whole bikes as donor frames and selling off the groups. Then it's just a question of time. Set aside a day and a half if you've never fitted a group before and follow the Shimano Dealer Manual instructions. Trickiest bit will be re-taping your bars, all you need for the group is a set of allen keys and maybe a BB wrench if you're changing the bottom bracket

+1 for Tiagra. I have one bike with Tiagra 4700 and one with 105 5800 (which was superseded by 7000 in 2018); neither is the full set but both have the levers and front & rear mech. I can tell the difference, though can't really say that the on the road the 105 is better - it's slightly less of a push on the lever to change, plus the extra gear on the cassette.

Tiagra parts are cheaper, sometimes significantly so, and to me seems in the bang for buck sweet spot. It's a bit like getting a Skoda instead of a VW - a bit less image, almost the same real world performance, for usefully less money.

And definitely new cables, whatever you decide. No point in re-taping the bars with aged cables, and while at it, lovely new tape will reinforce the "whoo, new stuff" feeling!