PapaMac67

I currently have a Shimano Tiagra 4600 groupset (F + R derailleurs, brakes, STI brake/shift levers, Tiagra, 10-speed, 12-28 cassette and Tiagra FC-4650 34/50 crank. The road bike they are on has 0 road miles (Long story – Life got in the way) so all the parts are brand new condition. I want to start riding again but due to my age (53) and back surgery 2 years ago I can’t go back to a road bike. I want a more upright position and be able to ride on pavement and some gravel/dirt. What I’d like to do is buy a used mountain/hybrid bike and install my Tiagra parts and a set of drop bars and make a nice nimble gravel bike. Searching around I found a nice candidate. A GT Talera 4.0 men’s bike with F + R disc brakes which is great because I want to switch to disc so won’t be using the Tiagra brakes and it has a suspension fork. I just wanted advice from more experienced folks as to whether I can just switch over my Tiagra parts to this bike (minus the brakes) and maybe upgrade the brakes and be good tov go? Will tiagra 4600 road parts work on most MB type frames? thanks

thook

i believe you're going to need a wider bottom bracket so the crank arm will clear the wider chainstay of a mountain bike. also, be aware mountain bikes have a longer top tube and usually a lower stack height (google for definition) than road bikes. so, you'll need to accommodate for the longer reach and lower handlebar height with a taller/shorter reach stem and possibly shorter reach handlebars. otherwise, you might wanna hop on over to the classic and vintage section to the thread on drop bar mountain bike conversions. lots of examples and perhaps someone who a has a set up your considering

https://www.bikeforums.net/classic-v...nversions.html

Andrew R Stewart 

So many conflicts- Wanting a nimble handling but has a suspension fork. Mentioned BB/crank fitting issues. Disk brake/road STI levers issues. Ft der mounting and it's outward travel issues. Gear range likely being way too high ratioed for dirt/gravel.

I'll suggest you might be far better off selling the road bike (while the pandemic is still making a seller's market) and invest in a real gravel or cycle cross bike if nimble handling is still the goal. Or a race focused hard tailtB if real off road is the greater goal. Andy

jimc101

Crank won't fit, you need a MTB width one, for the positioning, without seeing what your looking to work with, experience says it may work, but with a lot of adjustment

These are incompatible, you need road disc calipers (mechanical) for the 4600 STI levers.

Simple answer is no, some will work, some won't, I understand what your attempting to do, and have done it myself, but it's not a simple process of moving road parts to an MTB frame, and most MTB's make poor conversion, due to their geometry, the best ones to use are old, as in very early 90's/ late 80's with long wheel bases/long head tubes, worst are mid-late 90's with short head tubes, bringing in discs (brakes) bring a host of other issues, which can easily be fixed, normally by throwing more money (and even more for hydraulics) at the issue than you would by just buying a purpose built bike in the first place.

From your question, what your asking is doable, but it's not for the beginner, and you need to do a lot of research into compatibility and be prepared to adjust and adjust, and even then it will end up as somewhat of a compromise, and never be as good as a purpose built gravel bike, and will probably end up costing similar unless you have lots of spares to use.

If your 4600 groupset is mint, sell it (it may be worth even more than the bike it's on your market dependent), and use that money to put towards a 2021/22 gravel bike which will do what you want out the box.

PapaMac67

That's it then. I will sell the bike. It appears there's too many issues/compatibility problems to make this a simple and cheap project. The bike is a 2014 Specialized Allez Comp Smartweld size 56. It originally came with AXIS brakecalipers and an FSA Gossamer crankset but my OCD made me replace them with the Tiagra calipers and the Tiagra crank. The idea of putting an ad up to sell it and fielding phone calls doesn't work for me since I work nights and sleep days so I think I'll call some local bikes shops in the Buffalo NY area and see if any of them would buy it or trade it towards a decent gravel bike. Based on my research its gunna be a $1000+ and upward for something with disc brakes and quality components. Originally in 2014 the Allez Comp sold for $1200+. I bought it in 2017 for $750. I'm not really sure its worth now? $500-$600? I'll see what happens. Thanks for all the help/replies!

Andrew R Stewart 

More like half what you are hoping for. less if a shop will be the buyer, which I doubt will be offered. Andy