What to look (out) for when buying or upgrading a bicycle?

[BikeGremlin]

"There should be a special circle in hell for people who design those stems that have the hoses and cables going through them!"

 

[BlackOp03]

After watching some of your videos, I'm completely changing my mind about updating rim brake system on my old step-trough (90's) mtb into discbrake system. For some obvious reasons: 1. They're heavy, means less performance/speed ; 2. Didn't offer much better braking perfomance than proper rim brake (except on mud/wet areas just like you said); 3. Complexity. Never knew before, that through axle system is a must have for a proper discbrake system. Another fact that discbrake rotor burdening wheel spokes also doesn't sounds good for me. Less gaps and faulty rate also adds complexity layers. Can't help that lots of issues just appear one and another when I'm digging this matter; 4. They're expensive. Pretty much expensive that buying new spare rims and rebuild another one is still way cheaper than adopting a newer discbrake system.

Thanks for your previous advice about wheel lacing patterns, my bike is superb now. 4x lacing on my rear 26 rim just awesomely absorps unwanted vibrations. Better traction too. No puncture at all after 1 year or so.

So longer chainstay length is good for climbing (mine is about 46cm). From my observation, longer chainstay also bring better chain angle/ less severe cross chain effect. Then how about center-front length? Is there any benefit or unwanted effects from changing it? (Somewhat my current bike also equipped with fork that accomodates 3 axle positions)

(On picture is my current bicycle setup)

 

[BikeGremlin]

Good questions and good talking points that I'll further discuss in an effort to inform and educate anyone coming across this in one or ten years' time.

After watching some of your videos, I'm completely changing my mind about updating rim brake system on my old step-trough (90's) mtb into discbrake system. For some obvious reasons: 1. They're heavy, means less performance/speed ; 2. Didn't offer much better braking perfomance than proper rim brake (except on mud/wet areas just like you said);

Yes. The common misconception is that disc brakes are more powerful. The main advantage of disc brakes is the better modulation in the wet, but rim brakes have more than enough stopping power (if we compare apples-to-apples, i.e. good disc brakes with good pads and rotors to good rim brakes with aluminium rims and good pads).

Digression:
Rim brakes have a 600+ mm large disc. So, despite having lower mechanical advantage, because the brake pads stay further out and move over a longer distance to the rim (compared to the movement of the disc brake pads), the huge "disc" (the whole rim itself) can compensate (compared to a 160, or "even" a 200 mm rotor/disc).

• Mechanical brake working principle and mechanical advantage explained (article with sketches).
• Hydraulic brake working principle and mechanical advantage (video explanation/demo).
• Hydraulic brake hose and air bubble removal principle (video).

3. Complexity. Never knew before, that through axle system is a must have for a proper discbrake system.

Yes, that is a problem. You can ride safely if you check the quick-release lever before a ride (or daily) - drawing marks to check if there is any movement (rotation) between the QR and the fork can also help keep things in check. But QR is lees than ideal system for the front disc brakes. Reasons explained here (below picture 9):

https://bike.bikegremlin.com/11319/bicycle-frame-design/#3.1

Another fact that discbrake rotor burdening wheel spokes also doesn't sounds good for me.

That is partially true, but with mechanics, the devil is in the detail. Let me shead some light on this:

• Disc brakes put more stress on the fork (for reasons explained in chapter 3.1 of the above-linked article).
• They transfer torque from the hub to the rim (through the spokes, of course) when braking - in a similar way that the torque is transferred when pedalling, only in the opposite direction. This is why radial lacing is extra silly with disc brakes, even on the front wheel (radial lacing is always silly, but that is a tangent discussion ).

However, if we look at peak loads of particular spoke(s) at a given time, rim brakes actually put more stress on the spoke(s)! Why and how? Briefly put: disc brake uses all the spokes to transfer the braking force (all the leading spokes gain some tension, all the trailing spokes lose some tension, and so they all share the load). With rim brakes, only the few 9-o'clock spokes gain some tension, while only the few 3-o'clock spokes lose some tension, while the 12 and 6-o'clock spokes don't share the breaking load.

I explained that in the video called "Science behind the spokes - Bicycle wheel" (the link should start at 36:38 where I discuss rim, then disc brake loads).

Less gaps and faulty rate also adds complexity layers. Can't help that lots of issues just appear one and another when I'm digging this matter; 4. They're expensive. Pretty much expensive that buying new spare rims and rebuild another one is still way cheaper than adopting a newer discbrake system.

It's fair to note that this depends on the riding conditions. Whole year riding in say Scotland, with many hills and rain, can wear rim brake rims pretty fast if one breaks a lot on descends (depends on the steepness, road configuration, traffic conditions and rider's skill). However, for most use cases, that is not a big problem and I too prefer rim brakes - swapping the rims every now and then is not a big problem, compared to other disc brake expenses and downsides.

Thanks for your previous advice about wheel lacing patterns, my bike is superb now. 4x lacing on my rear 26 rim just awesomely absorps unwanted vibrations. Better traction too. No puncture at all after 1 year or so.

Generally, lacing pattern or even spoke tension does not affect ride comfort (many riders and even mechanics get that wrong), but the lacing pattern (provided the spoke tension is not too low) can affect the wheel's rigidity and stiffness when dealing with torque and side loads. This is an experiment and a discussion on that topic:

SPOKE LACING: What makes Sense and what is Nonsense! Efficiency Comparison using Advanced Engineering software

So longer chainstay length is good for climbing (mine is about 46cm). From my observation, longer chainstay also bring better chain angle/ less severe cross chain effect.

Yes. Definitely. That is another great benefit of having reasonably long chainstays. I would also add less front derailleur cage rub when cross chaining (because, as you noted, longer chainstays reduce the chain's angle).

Then how about center-front length? Is there any benefit or unwanted effects from changing it? (Somewhat my current bike also equipped with fork that accomodates 3 axle positions)

In my experience, most bicycle frames get that part right. Head tube angle and the fork rake differ for road, MTB, and touring bicycles, but that is usually done right for the bicycle's intended use.

• Front wheel to bottom bracket distance too small:
  Frame builders make sure to avoid toe overlap as much as reasonably possible, so, the front wheel's axle is practically never closer to the bottom bracket than absolutely necessary
• Front wheel to bottom bracket distance too large:
  Frame manufacturers also make sure to not have the front wheel too far forward, as that would generally increase the weight load on the rear wheel, which already carries most weight.

Moving the front wheel further forward would also affect handling and some other aspects, but this post is already quite long.

For anyone interested to go down this rabbit hole, I wrote a whole article explaining the bicycle frame geometry.

(On picture is my current bicycle setup)

That looks like a nice, reasonably assembled commuting bicycle. I would add a front mudguard - on a similar fork (with no mudguard mounting eyelets), I used some shims around the fork legs to serve as mudguard mounting points and it's worked well (must take a photo of the setup).

Relja

 

[VlPo]

"There should be a special circle in hell for people who design those stems that have the hoses and cables going through them!"