Beginner Q's

axiomflash said:

Hi, I am just starting to get into amatuer road racing, but I have a number of questions I can't get a clear answer to anywhere locally. Any help I could get here would be greatly appreciated. I'd like to get these concepts cleared up in my mind before I go out and buy a bike.

I understand how to determine an appropriate frame size, but how should one go about selecting the correct tire size. How much is this dependent on the frame?

Wouldn't larger diameter tires naturally have a mechanical advantage over smaller tires when travelling at high speeds? ex: 26" tires would move 163" per revolution, but 28" tires would turn 176" per revolution. This might be a disadvantage at lower speeds, but at the highest gear it seems this 13" per revolution would make a massive difference in total bike speed. Am I completely wrong here, or how does this work?

The same question applies to the gears. I can't find much information on the different cassette sizes that are available, but it seems that a larger than typical front cassette would make higher speeds achievable. I often find that I am peddling as fast as my bicycles gearset will let me rather than at my own personal max.

THANK YOU FOR ANY HELP!

Current road bikes are predominatley 700c wheels unless you ride a very small size and use 650, which will be a bit slower for the same gear combination and cadence. Basically forget the tire business and move on. Gears are about gear inches and tooth combinations front and rear. Road double cranks for racing would typically have 53/39 chainrings unless you go with a compact double and 50/34, so worry more about cassette cogs. You would have to be pretty good to max out a 53 chainring and 11 rear cog. Sheldon Brown has a gear inch chart at www.harriscylery.com

I wouldn't get too hung up over wheel size and maximum speeds as an amateur getting into road racing. Your level of cycling fitness is what ultimately counts re. sustaining effort on the bike, not the diameter of your wheels.

As far as 26" (650) or 28" (700), I think this is a matter of preference. Generally, the smaller 650 wheels are more suited to shorter riders using smaller frames. 650 wheels weigh a bit less and accelerate a bit quicker (less inertia), but is not likely to be a significant concern for you, starting out.

You find that your current bike's gearing is too low - are you riding a mountain bike? These are geared for off-road, going up slopes etc., as opposed to being geared for higher speed road cycling.

yes, right now I am just using my touring bike which I have learned now doesn't have nearly as many as the 53 teeth on a typ. racing bike. i rode my friends old race bike the other day and basically maxed it out, so my concern is that I don't want to spend $800 on a bike that I can max out at some point even if not likely now. also, Im just trying to learn a bit more about the mechanics and efficiency of bikes as that is kind of my niche. thanks for the advice, it was very helpful 🙂

one last question, if i were to buy a bike with 650 wheels standard, would I be able to put 700's on it, or are framesize/wheelsize directly tied? im a tall dude so bigger is better for me really.

axiomflash said:

yes, right now I am just using my touring bike which I have learned now doesn't have nearly as many as the 53 teeth on a typ. racing bike. i rode my friends old race bike the other day and basically maxed it out, so my concern is that I don't want to spend $800 on a bike that I can max out at some point even if not likely now. also, Im just trying to learn a bit more about the mechanics and efficiency of bikes as that is kind of my niche. thanks for the advice, it was very helpful 🙂

one last question, if i were to buy a bike with 650 wheels standard, would I be able to put 700's on it, or are framesize/wheelsize directly tied? im a tall dude so bigger is better for me really.

You don't even want to think about 650 wheels.You couldn't put 700c wheels on a 650 frame anyway. If friends bike has a 13 or 14 small cog you may well have maxed it out. You won't max out an 11. besides, chainrings and cogs are not a permanent part of the bike.They get changed out all the time.

axiomflash said:

Wouldn't larger diameter tires naturally have a mechanical advantage over smaller tires when travelling at high speeds? ex: 26" tires would move 163" per revolution, but 28" tires would turn 176" per revolution. This might be a disadvantage at lower speeds, but at the highest gear it seems this 13" per revolution would make a massive difference in total bike speed. Am I completely wrong here, or how does this work?

The same question applies to the gears. I can't find much information on the different cassette sizes that are available, but it seems that a larger than typical front cassette would make higher speeds achievable. I often find that I am peddling as fast as my bicycles gearset will let me rather than at my own personal max.

The problem is that the faster you travel, the more wind resistance there is pushing against you. If you run too tall of a gear, then your cadence starts to slow down, as your legs don't have enough power to fight wind resistance and other forces against you, so you have to down shift.

The trick with gearing is to use a combination that allows you to spin at the proper cadence for the most amount of time in your typical ride. If you try to accomodate the steepest ups and downs, then your gearing range is so broad that the jumps between gears makes it impossible to find the right gear on slight hills or flats. So, the right gear combination is the one that has an acceptable range (difference between highest and lowest gear), yet maintains the tightest gear spacing possible.

If you are often tapping out your highest gear, then perhaps you can gain by using a smaller rear cog, which will sacrifice the tightness of the gear spacing elsewhere in the range. But you will only be able to gear up a little bit before you are trying to push a gear that's just too tall to be useful. Because wind resistance increases exponentially with speed, you will find it progressively more difficult to push taller gears as your speed increases. This is why it's easy to increase your speed from 5 mph to 10 mph, but damn near impossible to increase your speed from 25 mph to 30mph.