Sardines

A 40 to 44t chain will gain you a couple of km/h at the top end, and you're still have 28+" of gearing, so you should be good in terms of climbing ability. A XL saddlebag in lieu of panniers does help a lot with aero. I did that for a while, but then I moved to bigger laptops and even trunk bags couldn't fit it.
Also switching from a wide tire, say durable 40mm to a fast 32mm, will help with aero and rolling resistance as well. And improving aero at over 20+km/h will help with speed. So in combination, you may just get significant minutes of time on the flats, with the same effort.
That is the one thing I miss about COV19... traffic was lighter when people stayed home! haha

Leisesturm

Even better ... drop bars! If the o.p. bike is flat-bar a drop bar setup WILL shave some minutes. It's all about the aero. Savvy bike commuters are ditching backpacks and going to panniers and are much happier. I just spent a lot of money on a specialist pannier for business attire so my wife doesn't have to wear the 40L backpack she used to stuff with clothes, laptop, and etc. FWIW.

Badger6

I live outside of Brussels and commute into the city for work. So, I can relate to everything you’ve said about riding in the city. I wonder what exactly is the route you use through the city. Do you have the option of using some of the protected bike lanes or designated bike routes? I’ve found that some routings through the city are very fast, while others are horribly slow. I tend to ride mostly on the eastern and southern side of the city, and avoid the center at all costs…unless filling in streets on Wandrer.earth.

Also, for commuting, not sure what tire you’re on, but the Specialized Roubaix 30/32 (if you can find it in Belgium) is excellent. Rolls fast, and is very durable. I run mine tubeless, and I’ve had exactly one flat in 2 years here. And one other in the previous 4 years using those tires.

Sardines

My recollections of Belgian roads are mostly riding out of the cities en route to the next country. What sort of flats are you guys getting? Punctures and/or cuts from sharp debris, sidewall damage or pinch flats from too many potholes? Going tubeless will usually take care of punctures and especially pinch flats, and you save a little weight and rolling resistance. The other damage you will have to get a much tougher tire, which can affect rolling resistance and aero.
Funnily I've been experimenting with Google Maps bicycling routes and my own devised routes. Google is great at telling me where traffic is, and I am willing to be annoying and ride on curbs (kerbs for you UKers) to wind round traffic if unavoidable.
poeli , I would first try get a baseline time for the commute, averaged over a week, then install the chain ring upgrade to see if there is an improvement over a week. Once you get a new baseline with the chainring, then try the tires,etc. Basically try to upgrade one element at a time so you know which one has the biggest gain, and which one is negligible. Also grade on comfort, for eg, the backpack vs panniers/saddlebag, or the tire pressures vs speed gains. Took me awhile to figure out but I found a custom padded bag with uniklip attachment, helped me the most aerodynamically, as did the faster GP5kSTR tires. Thanks to you I am also looking at testing a pair of GP5kTL to see if there's a difference, cos those tires are 30% cheaper, and being at EOML, will be easier to stock up.

Sardines

So how did it go?

poeli

I wish I could say I tedted it already. Installed it but then lying wheel bearings gave out and did my bike to my local bike shop. Fixed and continued. Then my derailleur was broken, back to the bike shop where its been for 2 weeks already (almost 3). Holidays now so I will certainly give them a call when i can pick up my ride (and finally test!!)

Sardines

Yikes, sorry to hear that. But yeah that's the problem with derailleur systems, it's a chain of things to break down. With Pinion and Gates belt, I only worry about oil change every year, and belt health. It's a dream to maintain. But 3 weeks to change a derailleur? Is it that busy in the summer?

poeli

spare parts are difficult to get apparently. But still. I want my ride so I can test!

beng1

Leave earlier in the morning for work, then you can get to work on time easy and without stress, works on a bike or if driving an automobile.

Ridinglurker

I'm impressed with your ride. My commute is 9km and I don't get over 20 kmh on average. 5 traffic lights ruin all gains.

If you have flexible work hours, try finding a better time to have less traffic. Not only is it faster, but also safer.

Don't use a backpack! Consider a frame triangle bag. That is aero and lower center of gravity. Maybe a bag on rear rack would not as much drag ad panniers.

On rough roads wider tires and rims may actually be better since you lose less energy moving up and down. Get really expensive tires for less rolling resistance. Consider tubeless to avoid flats. Obviously a flat ruins all time gains. I have Schwalbe Allmotion touring tires. Very robust and so smooth rolling at 2.15".

Tight clothing and good seating positions. But there is a tradeoff between power, aero and comfort. Don't sacrifice comfort for speed.

jakez

:d:d:d