Best ways to increase biking speed

Two things will help your bike times. The first is, obviously, improved fitness. The second is, unavoidably, better equipment. 

If you really want to hit those big speeds, here's the recipe:

a) buy an indoor trainer and a good training program. I have the Kurt Kinetic Road Machine paired with the Trainer Road software and I recommend this combination highly. Measure your FTP regularly to see how you're improving - you will see a pronounced difference in your bike times.

b) you need a fast bike. I've no idea what kind of budget you may have but a good tri bike is essential if you really want to hit the heights. And you're going to need some aero wheels as well - more $$$. And then an aero helmet...and then a aerodynamic hydration system...the list is (nearly) endless!  But f your bank account doesn't allow for those things at this time, then there a couple of things you can do to speed up your Felt. The first is clipless pedals and cycle shoes - that is an absolute no-brainer. The second is clip-on aero bars.

Yes, it can get expensive but at least you don't need to spend too much on the swim and run! :-)

Good luck!

Very very simple answer:

1. Bike more

2. Bike harder

No secret. Just work harder.

Riding hard, getting a good trainer, etc. -- all good advice.

But one of the biggest barriers to speed is your body position on the bike. The drag that your body creates is huge, so reducing that is key. A tri bike helps greatly with that. But much of that benefit can be had from clip-on aerobars. Or even by improving your position on your roadie. 

Play around with the tools on bikecalculator.com - the speed gains from changes in position are dramatic, and often larger than the gains from a significant fitness increase.

I'm going to guess, but I'll be pretty confident guessing that you're not spending enough time on the bike regardless of what you do to get really good on it.

Those guys doing 21-23mph are often doing 3hr long weekend rides in addition to 2-3 solid weekday ride sessions, if not more. 

Up that time in the saddle, and then once that's done, increase quality (intensity) and you'll get there. If you're hitting 20 mph for 20miles, you're essentially there - just need a small boost to get into the next category.

I'm gonna post twice on this because it's important.  It does not matter what kind of bike you have, or how heavy it is, or how aero you are, if you do not ride.  Lots.   I have friends that are insanely strong cyclists that do most of their training on heavy mountain bikes in decidely un aero positions.  I do all of my off season road training on a non-aero position road bike, and I get faster each season. 

So the aero bar, lighter bike, etc suggestions don't answer the question.  If you ride your bike  - whatver that is, however heavy that is, in whatever (comfortable) position you have - you will get better (i.e. faster).

Now, in races, equipment will make more of a difference.  Bike shoes and clipless pedals will transfer power better, better aero position will reduce drag, etc.  But you don't get faster by how you ride in races.  You get faster by how you ride in training

Sorry to highjack thread, if someone is a spinner with high cadence should the harder weekday workouts be in a slightly higher gear with slower cadence and vice versa? or split? (1 hard workout at normal cadence and one pushing big gears) or does not matter?

Thanks.

I have been using a slightly harder gear at a lower cadence to get into my uncomfortable/pain zone.  After reading some posts from Feltgood.

Well said!

Riding more is the largest part of getting faster. There is another aspect as well. You need to ride harder. Having something to help you judge "harder" is useful. You don't have to go all out and buy a power meter but a heart rate monitor can be helpful. You just want to be able to go by more than speed since a tail wind or a particularly smooth road can make you go faster.

Training inside gives you a controlled environment for dosing out the intensity of your workouts. Riding hills (especially the same ones) also helps you tune in to working harder in a measured way. Like many other triathletes, I have fun overthinking how to get faster but so long as you ride, ride, and ride some more, mostly hard - you'll get stronger and faster.

Keep riding and have fun riding faster!

X2

But if I may add, to ride at higher speeds for longer periods of time, you need not only the aerobic endurance, BUT more importantly you need the leg strength.  I've done cycling off and on for 25 years, but it wasn't until this past year that I realized that beside riding more, I need specific leg strength.  What does this mean?

I found an article on the internet last fall (I can't find it at the moment or I'd post the link, and will post when I find it) that showed the relationship between wattage power in newtons on the bike to gym weight kilograms.  Once I read this a light went off and I changed the way I do my gym workouts and my goal weights to lift.  Consider also that you are using only 20 to 25% at best of your maximum leg strength when cycling, the rest of the energy is lost to sweating and other inefficiency losses.  And the article further stated that assuming all cyclists are equal in vo2max ability then the cyclist that wins is the one that is using the most force for the longest time.  Simple.

What doese this mean?  To go 21 to 23 mph avg. requires about 210 to 240w in aero positon for most people depending upon size and position, etc. but let's assume all is equal... 225 watts requires any person to push down on the pedal with approximately 20 to 24 kg (45 to 55 lbs.) of force with each pedal stroke and each leg independently (test whether you can do this on a leg press with a single leg, also consider the sled weight, but if you can't do a single 50lb leg press, then you're not going to be able to ride very long at 21 to 23 mph.

I continue... a newton converts almost 1:1 with kg... but you have to do this continuously over the length of the race, whatever that length is... furthermore, we're triathletes that have to run afterwards, so you're not going to use your entire energy reserve.

Also keep in mind that improving speed is logarithmic, that every increase in speed (i.e. 1 mph avg more) requires a greater increase in strength and so forth, that to go from 18 mph to 20 mph avg. is easy, but then to go from 20 to 22 requres 2x more strength than the previous 2 mph avg. increase.

What does this mean?  it means that to go an avg of 21 - 23 mph, you'll need a maximum gym strength of around 2 to 2.5x or more of your body weight... since you'll only actually be using about 20% of that power to go the distance of say 56 miles of an HIM bike leg.

The conclusion: once you've established what you'll need in strength, then you can work toward that goal.

Then go out and ride more and train properly... I'm not going to profess a certain training regime, since they can be very individualized within the proven methods of training.

I don't think a bunch of time in the saddle is the only way to get faster either, at least not at the sprint distance.  I am now 50, and have steadily improved to 23+ mph average for a sprint over the last 4 years of doing tris (coming from a strong running background) with only 2 or 3 rides per week usually between 15 and 25 miles and some hills, but with lots of intensity.  I averaged about 1400 miles a year (about 27 per week) for 2010, 2011 and 2012.

Also, get some clipless pedals ASAP!

I am confused.  Isn't that "a bunch of time in the saddle"?  Of course, getting as much as you can out of the time you are able to put in matters, too.  That's just as true if training for sprints or training for IM.  It's all endurance.