We did it. We did one of the most fabled cycle routes amongst cycle tourers. The D100 into Istanbul.
However, we made some changes we felt were of benefit but did make it a little longer time-wise.
The D100 is the main road (excluding the motorway which bikes aren't allowed on) from Edirne to Istanbul and beyond. We tried to avoid parts of it the further into Istanbul we got, but here's a vague description of the route in.
Edirne - Corlu (day 1) - 120km, 4000ft climbing
There is a man in Edirne who owns the bike shop Trayka Bisiklet. His name is Engin and he is a legend. He is a Warm Showers host and is possible one of the most commonly used hosts we've ever heard of. He has a guest book he asks people to sign and as we flicked through we recognised three people we knew. If you have seen our Vlog update, you'll know we were in a tight spot when we reached Edirne and we also had very little phone signal. We turned up to his shop and asked if he could help us and we instantly had a bed to stay for the night.
We left Edirne the next day a bit later than hoped because we needed to withdraw that money from MoneyGram via the bank and then we drank tea with Engin for a short while. He also sorted us a place to stay in Corlu with another Warm Showers host who also owned a bike shop. That gave us a 120km target for that day and off we went down the D100.
The hard shoulder is your friend for a really significant chunk of your way from Edirne to Corlu. In fact, it only disappears for about 50 metres the entire way. In some places it's almost a whole other lane wide. Leaving Edirne, it starts out flat and you can get quite a pace on if you haven't a head wind. The road will slowly start undulating and this will remain the nature of the road the entire day. It gets very tiring especially if you've got a head wind like we did. We concluded that since you're cycling between two bodies of water between two warm continents it's pretty clear a strong wind is the norm. The vegetation certainly had a permanent lopsided slope to them. The wind died down as the sun went down and after we stopped for dinner at Luleburgaz we managed to get much more of a pace on the rest of the way and caught up with ourselves. It no longer took effort to cycle down the hills!
If you don't need or want to stay in Corlu, we recommend you don't - continue on the D100 bypass around the city. Or at least get there way before it gets dark; it wasn't a pleasant city to cycle through after dusk. Also make sure you have a bit left in your legs because to get into the city there's quite a hill.
Corlu - Istanbul (day 2) 120 km 3000ft climbing
Another quick start to the day takes you out of Corlu flat and downhill. You still have the hard shoulder until you get towards the coast. Around kilometre marker 13 as you approach Silivri you lose the hard shoulder completely and significantly for the first time. This is really the point where you should take the service roads off to your right as often as you can as it's probably getting a heck of a lot busier. At one point you lose the shoulder and you're going up quite a steep hill. We got off and pushed, standing on the inside of our bikes right next to the barrier, because the potential for wobble into traffic was too high. We weren't given much room at all by overtaking vehicles and the traffic is moving too fast for you to be taking the lane properly.
We came off the D100 at Silivri and hugged the coast as much as possible. We had to come back into the D100 as you start to cross the sea inlets and we couldn't find a way to significantly avoid main roads until we got to Avcilar. Make your way down to the coast line and enjoy a peaceful cycle along the promenade with bike lanes. Our final dalliance with the D100 was crossing the narrow bit of land just after Avcilar, but even here we were on the service road - but it was busy. Come off towards Basinkoy Istanbul Cd. And you can join the promenade again at the Aquarium.
That pathway will take you all the way to Rauf Orbay Cd. Which is an unfortunately busy road, particularly at the time of day we reached it. Eventually you'll see a blue cycle path off to your right - join it! It takes you all the way (with a bit of normal pavement use) to the turn off for Sultanahmet (the old city).
Well done, you've made it into Istanbul! That's the best route we could find under our two day time pressure. They're long, hot days in the summer but if you've already crossed Europe, it's totally doable. We recommend you get yourself a good mirror for your handlebars, it can save you when you see a lorry not giving you much room.