Bike Geometry 2

This is the second part of the Bike Geometry discussion. (Please check out part 1, here) 
In this post, we're discussing the second important aspect of geometry:

Designing a bike for Intended Use Case Scenario.

As discussed in the previous blog, the 1st priority is to position the 3 contact points of the rider on an X,Y,Z axis. These points are then connected with the 9 tubes of the frame, 3 tubes of the fork and the last 3, of the stem. The angles at which these are joined and lengths of each tubes can be altered even when the 3 contact points remain in the same positions. 

For example, lets consider the saddle center to handlebar distance. Say this distance is 660 mm. 

This can be approximately achieved with a 100 mm stem and a 560 mm Top Tube. Or a 60 mm Stem and a 600 mm Top Tube combo. (Note that TT + Stem is not exactly equal to saddle center to Handlebar distance. However it serves as easy reference figure.) 

Now lets see what happens in each case:

A shorter than usual top tube will require a very shallow steering angle. This, (combined with the fork offset) can hamper the steering characteristics of the bike. 

On the other hand, very short stems can make the handling of the bike twitchier.

As can be seen, each of these design choices affects the character of the frame. A custom steel bike not only addresses the perfect fit of the rider but also is the sum total of a large number of decisions, taken in the background, but affecting the rider and bike usage.  

When each choice has a consequence, the best way to make these design choices are to define the end objective and work back from there. Take the case of an endurance bike (like the VELOPILGRIM MOKSH.) The key considerations for such a frameset are:

1) Comfortable riding position for long hours on the saddle: 

a) High stack & Short reach: Riders can sustain an aggressive posture for short and fast rides. This is especially true for athletes. Picture Tadej Pogacar on a Colnago or Marc Marquez on a Ducati MotoGP motorcycle. The classic low and long riding position. It looks great! But when normal folks or even athletes ride longer - say a 600 km brevet or a multi day tour covering 200 + km's every day - the opposite works better for the body. A higher bar and shorter reach to it is the need of the hour. (or hours!)

b) This means a shorter saddle to handlebar drop as well. How much lower the handlebar is compared to the saddle height was mostly dictated by the maxim, "Slam that stem!" But for endurance rides, that's not a great idea. Ideally it should be based on the rides' body proportions. For a bike like MOKSH, The handlebar drop is lesser. This may mean the rider and bike combo may be less aero. And that's ok as long as the rider is comfy. But, care needs to be taken to put enough body weight on the handlebars to load up the front. (More on this later.) This makes sure there is enough grip in the front tire. Playing around with the front center and chain-stay length helps find a good weight balance for each rider. Having a custom steel fork helps as well.   

2) Stable handling bike on good and bad roads: 

Imagine you are riding non-stop for 4 days with hardly a few hours of sleep in between. You are riding alone. You are also tired, sleepy and hurting in a lot of places. Having friends in such a situation can help. Let me introduce you to the 3 friends of a long distance cyclist.

a) A comfortable bike is your friend. 

The buzz that a rider feels on less than smooth roads are non filtered micro vibrations being transmitted from the road to the tire to the rims to the spokes to the fork and then reaching the riders palms, arms shoulders and buttocks'. Thin, steel tubes - like curved fork blades - absorb these micro vibrations from the road. Over 100's of kilometers, this insulation can make a major difference to the fatigue level of a rider - especially compared to stiff carbon and alloy bikes - on similarly wide (or even lesser!) tires. 

b) A stable bike is also your friend. 

Sometimes a rider is tired, sleepy or worse, both. Stability is a massive plus point in these cases. Also, in most cycling groups, some riders have a reputation to fall off their bikes, often. Now imagine a bike that can balance itself well even when your hands are not on the handlebars. Bikes can be made stable by adjusting some key figures in the geometry chart. For example, having a slightly longer wheel base than pure road racing bikes. Or having a bit higher "trail" figure. Or having a slightly lower Bottom Bracket drop etc. A combination of these as per the typical ride scenario or the specific rider concerned can usually be worked out to get the desired bike characteristics. (This is the case for each individual VELOPILGRIM MOKSH.)  

c) This brings us to the 3rd friend: A bike with intuitive, predictable handling. 

A side effect of a stable bike - especially ones with mid to high trail figures - is a bike that handles and steers in a very predictable manner on every kind of surface. There will be no surprises in directional changes whether riding over broken roads or smooth roads or when the rider is sleepy. The VELOPILGRIM Moksh comes with mid trail figures in every size (again, only possible with custom forks!) Which means, the bike steers predictably during fast, wide downhill turns (even under braking) or slow acute hairpin curves. Which also means, a lack of nervousness or twitchiness on the handlebars.  

For all the above criteria to work, a custom steel fork is indispensable. Yes, steel forks are not light-weight. But that's the compromise needed for all the above to work (And that's why VELOPILGRIM MOKSH will always have a custom steel fork.)  

3) Weight Distribution - 

We have reached the most important topic: Weight! 

Most steel bikes weigh between 8 to 12 kilos. 

Most riders weigh between 45 to 100 kilos. Lets add another 6 to 8 kilos for hydration, fuel, spares, navigation, tools, change of cloths etc. So a total system weight of between 60 and 120 kilos.

Now, most endurance bikes have a wheelbase of 950 to 1050 mm. And the total weight is concentrated on 2 very small contact patches of the tire that are placed on the road around a meter apart. This weight is either balanced well between the front and rear contact patches, or not. 

When the bike is made keeping in mind the riders body dimensions, and the planned luggage placement, both wheels are loaded correctly, there is less wear of parts/components like hubs, spokes etc. and the bike handles well on different surfaces. The rider is placed at an ideal position between the front and rear wheels by altering the chain stay lengths, seat tube angle, front center, and the fork dimensions. This is pretty hard to achieve on a bike bought off the shelf.  

4) Aesthetics: 

Nature worked out the laws of attraction, over millions of years and distilled it into a secret code. This code was then put in to our eyes. Hence the saying, "Beauty is in the eye of the beholder." Well kind of... :)

That secret code is proportion. Everything in proportion "feels" right. Everything out of proportion "feels" weird. Some folks understand this consciously and the others feel it subconsciously. So when making anything humans consciously or unconsciously try to make it look good (a.k.a proportionate.) For example, a building built to the golden ratio. This is a deliberate act and takes time and energy.

When custom building a bike, its possible to take time out to see how the whole bike comes together elegantly. This is so because a majority of all components are hand made and hence non standardized. Also each aspect is considered deeply during the 6 week build period of a frame build. But when making a bicycle in a factory, this is the 1st element that gets thrown out of the window as production process requires efficiency and standardization of parts. While the benefit is an immediate purchase in case of an over the counter model, a custom built bike involves some lead time. But having a bike built not only to the proportions of the riders body but also proportionate in the eyes of the beholders is something special indeed. 

1) Race bike vs Endurance bike: https://hedcycling.com/blogs/tech-performance/what-size-road-bike-do-i-need?srsltid=AfmBOoqboEuijXrPMXT4elIxFCDGWNyDbjKkTEa0UMHZH5kL0PUCWTmz

2) Saddle to bar drop: https://www.reddit.com/r/bicycling/comments/9ug9qc/how_good_your_bike_looks_is_all_about_saddletobar/

3) https://www.bollywoodhungama.com/news/bollywood/3-idiots-sequel-titled-4-idiots-makers-search-fourth-lead-accompany-aamir-khan-r-madhavan-sharman-joshi-report/

4) https://cicli-berlinetta.com/product/nos-omni-chromed-steel-road-bicycle-fork-1-threaded/?srsltid=AfmBOooJZ6kbWL0lOgjOGZUGQ9WdCIhaiyOhiE74zG1LqqtBhMSVJzG0

5) https://www.cyclingboutique.in/products/look-road-bike-765-optimum-plus-disc-brake-shimano-ultegra?srsltid=AfmBOop-96f7zkKzULXw8Si1TsASsuFmGeicgnitqQk96pelFu8mzHgS

6)https://bishopbikes.com/lugged-fillet-brazed-bikes/#&gid=2&pid=2