Any question answered...

mmmm just been looking at those. On the shortlist.

Maybe the only good thing Halfords sells: http://www.halfords.com/motoring/garage-equipment/tool-kits/halfords-advanced-professional-12-piece-ratchet-spanner-set

Had mine for years and they're all still perfect.

I think it would be more about leverage and the speed of the rim under the pads but I haven't quite figured it out.

So yes, the smaller wheel would turn faster. And thus be harder to stop. But it's lighter and thus easier to stop.

The smaller wheel requires more frictional force to brake (at the same rate) because of the smaller acting radius where the brake retards the rotating surface.

Archimedes, innit.

Let's say, two bikes, same speed, same weight (weight saved by smaller wheels is compensated by riders belly fat)
So yes, the smaller wheel would turn faster. And thus be harder to stop. But it's lighter and thus easier to stop.
I guess the difference is negligible, but it's interesting nonetheless...

Think of it on a grander scale and conservation of energy.

(You can ignore the rotational momentum of the wheels, just think how easy and quick it is to stop a wheel that is spinning fast (not in contact with the ground) with the brake, you can even just grab the wheel with your hand to stop it. That's nothing compared to slowing down 100kg of rider+bike from 20mph.)

So you're left with the job of the brake converting the kinetic energy of the bike+rider into heat via friction, which will be the same whether the rim is 28" or 20". This is assuming you're using the same pads on both rims and the contact area of pad/rim is the same for each.

Larger rotors on disc brakes increase the available surface area (larger rotors often have larger pads) so braking performance also can be improved this way. This is akin to using larger pads, not changing the rim size. The increased rotor surface area is also better for heat dissipation as the heat generated is spread over a larger area.

For long descents (e.g. mountains like the Alps) you'd prefer larger/thicker/heavier rims to provide a higher specific heat capacity and avoid the rim heating up enough to blow the tube (it happens!). Tandems especially suffer from this (even with some long descents in the UK) and you'll find they often have a rear hub containing a drag brake to spread the braking load.

Yes. Also it's rotating faster. And since the weight of the system the brake has to stop is the same, the same rim brake would feel weaker on a bike with significantly smaller wheels.

That makes sense.

Solution: disc brake ALL the things.

Also yes to all of this, but you seem to have left our poor Archimedes.

Larger rotors on disc brakes also increase the leverage of the brake (if that makes any sense. English is not my native language...)

Also yes to all of this, but you seem to have left our poor Archimedes.

I hadn't got to that bit yet.

Disc brakes work because you can use a much bigger lever to apply the frictional force - the pads can be set closer to the rotating surface, you can set the fulcrum closer, you can use a longer brake lever, you can use bigger pads etc...

It's our Greek friend all over again.

As Greenbank mentions, the force needed to slow the rotation of the wheel is negligible in comparison to the force required to slow the whole system.

Howard- I have the Halfords pro socket set, is good. Often available for "proper cheap" also- I bought mine on Boxing Day last year I think, for half rrp.

So you're left with the job of the brake converting the kinetic energy of the bike+rider into heat via friction, which will be the same whether the rim is 28" or 20". This is assuming you're using the same pads on both rims and the contact area of pad/rim is the same for each.

...cont...

So, if the braking force at the pad/rim interface is the same (same brakes, same pads, same contact area) then the larger rim will provide greater retarding torque as this will be proportional to rim radius.

So larger rim will brake better for the same force at the brake levers (with the various assumptions made above).

Something someone more knowledgeable than me about the internet and stuff may be able to answer?

My work has installed some kind of Dell internet filtering thing. PCs have IE installed by IT and this works ok. I prefer Firefox (well Cyberfox, Firefox is blocked by our IT policy) though due to adblockers, noscript, etc. This used to work fine but now seems to have issues with secure connections. I'll often get told that certificates aren't valid and adding a security exception can lead to a half-broken website (e.g. the times of posts don't show up on here). The same pages load in IE

Is there any way round this or am I condemned to using IE?

Cheers

Sounds like Cyberfox is missing (or lacking up to date) root certificates.

Can someone help my brain out?

Probably not.

In your problem, you can essentially disregard the rim size for most purposes, since the difference between the tyre radius (the lever trying to turn the wheel) and the brake track radius (the lever trying to stop it) is only a small fraction of either dimension.

The problem with small wheels is rarely the slight difference in heat capacity, it's the moving of the tipping pivot to a lower position, which lowers the limiting deceleration before you endo.

Yup, I live in SF, just back from holiday hence the delay.

what's up ?

It's our Greek friend all over again.

apolloxl?

apolloxl?

Gesundheit.

The problem with small wheels is rarely the slight difference in heat capacity, it's the moving of the tipping pivot to a lower position, which lowers the limiting deceleration before you endo.

Ah, that makes sense. Thanks for the reality check.

I think he goes by @apollo now

Trollololololll

Has he shrunk in the wash?

My question may seem simple in comparison to some of the previous, apologies.

I have a new bike (secondhand) and have just switched to fixed from the freewheel as I've removed the brakes as I've swapped the handlebars from bullhorns to risers. I hope to have the front brake set up tomorrow so I won't be brake-less. However, I just went for a little test ride around the block to check the tension in my straps and noticed a slip when attempting to accelerate away quickly. I presume it's the rear sprocket. Is it just a matter or tightening the lock-ring?

Probably not.

Probably not.

A new rear sprocket? Though, this one doesn't look like it's been used.

Try it again, see if it continues to slip.

Try it again, see if it continues to slip.

It slipped three times.