Tiagra is a really impressive groupset. It does everything you want from a mid-level road bike with only a few minor quibbles. The biggest decision is whether you're really fussed about having the 11-speed of Shimano's more expensive 105.

If you do want to take the upgrade route, you need to upgrade a large number of the Tiagra groupset components at once to make it work.

Chainset

For riders who need a shorter crankset, they will need to opt for 150 R7000 as it is available in 160mm. If you have smaller hands, then the R7000 brakes are likely to work better. This is because the lever does sit more closely to the handlebar than ST-R7020 levers. While bikes with Shimano Tiagra are usually substantially cheaper than those equipped with 105, the margin between the cost of components is often a lot smaller The hoods are comfortable to perch on and the levers to use, and there’s a solid feel to the shifting and braking.

Both groupsets use the same material to make the front derailleur. This is aluminum coupled with a chain guide that is stainless steel and then chrome-plated. The Shimano 5800 has gone 11 Speed for the latest incarnation of the 105. The 5800 has been inspired by the innovations of the more upper end Shimano Ultegra and Dura Ace; you can see the technological influences across the design of the 5800 components. More advanced and lighter than its predecessors and with a more eye catching design, the 5800 promises high performance and is one of the latest cycling must haves. With a 105 set-up, it does come with a direct mount option - you will need to ensure that your fork and frame are compatible. A direct-mount option means that the brake arms won't need a central bolt to attach to. Instead, they can be bolted straight to the fork/frame.Are the latest Tiagra rear derailleurs compatible with 105 (5700) 10 sp. shifters? (And vice versa, ie are new Tiagra shifters OK to work with a 5700 105 derailleur?) When you look at these derailleurs, they are different in appearance. The 105 R7000 groupset uses Shimano's "compact toggle design". Shimano claims (and I have no reason to doubt them) that the 11-speed 105 groupset is the most popular in the world. Aside from the chainset, the new shifters are the most visible change from the previous Tiagra groupsets. The gear indicator windows have been lost and the size and shape are much like 105. I have what is mainly a 10sp triple Shimano 105 setup (5703) and a Shimano XT Shadow 9sp (M772) rear derailleur on my 'winter' bike. In my experience it shouldn't require any special contorting at the pinch bolt (the so-called 'hubhub' method?) and the only adaptation I've had to make is to cut the cable outer to insert a Jagwire inline adjuster as this particular model of rear mech does not have a barrel adjuster.

Nobody needs 11t, who is not racing. And 2t jumps are just incredibly annoying, making it impossible to keep a comfortable cadence.The Tiagra brakes are impressive too. They don't fail to offer the stopping power riders want (and need).

The latest caliper brake design from Shimano is called SLR-EV Dual Pivot - this is available on 105, Ultegra, and Dura-Ace, so not Tiagra.

microSHIFT Acolyte H083 8 Speed MTB Cassette

Right now my fitness isn't what it was so finding myself spinning on the smaller front ring just for bigger hills, which I never used to need to do. However I think this will only be tempory as fittness is noticably getting better again day by day. It's not as simple as upgrading your Tiagra groupset components one at a time. You can't make the 10 and 11-speed parts work together. Overall, a Shimano Tiagra groupset is quite a bit heavier than a 105 groupset, but almost 200g of the difference is in the chainset