sstang13

I was practicing a 16 km time trial on an indoor trainer, but obviously there no way to tell distance indoors without a computrainer. So instead I assumed by going 32 km/h, which is how fast I go pushing on the edge of my ability the whole time (based on my only TT's ave. Speed) that if I ride for roughly 30 min, it would be 16km. But I wanted to find out my speed and couldn't find any formula online.

Is there a way to calculate speed using cadence, what gear I'm using, and time? This could also help determine how far I will go if I know what speed I'll go using a certain gear and choose a predetermined time limit. Thanks in advance.

E.S.

https://sheldonbrown.com/gears/

https://www.machars.net/bikecalc.htm

/thread.

Mike F

My wife put a cateye with the magnet on her back tire for her indoor training. Dont know if this is practical for your situation but thought I would throw it out there.

WHOOOSSHHH...

Probably is, but my head hurts just thinking about how to figure it out....

RollCNY

I prefer this one: https://www.gear-calculator.com/#

But if you want to know the basis of the math, distance traveled in a crank revolution is crank chain ring teeth / cassette cog teeth x wheel dia. x pi. Tire size impacts wheel dia. Then multiply this number by your cadence. It gives you distance traveled per minute, which is speed, but it will be in whatever units you did the wheel diameter in.

rm -rf

You want to match the same speed on a trainer that you plan to use for the time trial? You should be wanting to match your effort instead. Due to wind resistance, the power for any given speed is a lot different on a trainer.

A fluid trainer increases the power required as it's speed increases, similar to wind resistance. But even a Kirk Kinetic, that matches wind resistance, is similar to climbing a 1% grade, higher than the power needed for a flat road.

If I was training for a TT, I'd decide how long I expected the TT to take. I'd pick a resistance level and a gear combination that let me spin at my best cadence with the hardest effort I could maintain for that whole time. That's what is needed for a race that has headwinds and elevation changes--shifting to the best cadence for the conditions.

(Some bike computers have the sensor on the rear wheel. Those would count distance on a trainer.)

sstang13

No I did measure effort, but I'm just curious as to how fast I could push on a trainer...I hate my TT time/speed, I did my first and only back in September, I have a lot of training ahead of me.

John_V 

Any bike computer with cadence should give you this information when using the bike on a trainer. If you are specifically looking for a gear calculator, there is the on-line one already mentioned or if you have an iPhone/iPod, you can download Bike Gear Calculator from the App Store.

svtmike

Trainers provide different resistance, so how fast and how far you go on a trainer is irrelevant if you're trying to figure out what your road speed would be. Power is the way to go for that.

If you don't have a power meter, and your trainer is on their list, www.trainerroad.com might be a way to go for you.

gregf83 

Yes, but the more direct method is to just add a speed sensor or combination speed/cadence sensor to your rear wheel.

That said, the speed you go on the trainer is not the same as your outdoor speed.

surgeonstone

Time for a garmin