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Slowtwitch Forums: Triathlon Forum:
Bike trainer speed vs. road speed

 

   


akrievins

Jul 3, 13 12:04

Post #1 of 24 (2502 views)
Bike trainer speed vs. road speed Quote | Reply

I have a tough time averaging much more than 30km/hr on my bike trainer, but I'll do that fairly easily on the road over a similar distance. It might also depend on how tight the clamp is on my CycleOps Fluid trainer.

What are observations from others on ST?


uphillisgood

Jul 3, 13 12:21

Post #2 of 24 (2469 views)
Re: Bike trainer speed vs. road speed [akrievins] [In reply to] Quote | Reply

 
I use my Kurt Kinetic for intervals or base training. I find that it mimics the road resistance pretty well, but overall, getting my power numbers up is harder on the trainer. I think some of it is lack of movement of the bike and the other is that it is hard to shed the heat when riding indoors...even with 2 fans going full blast.

Bob


Toby

Jul 3, 13 12:26

Post #3 of 24 (2454 views)
Re: Bike trainer speed vs. road speed [akrievins] [In reply to] Quote | Reply

Speed on the trainer is relevant only so far as the resistance curve of the trainer in question. Forget speed.

It also does depend on clamping force, and tire pressure, and on the trainer you can't coast and can't get nearly as much cooling on your skin.

Really, the solution is TrainerRoad, or PeriPedal, or anything else that will estimate your power output from your trainer, then prescribe workouts based on that. Wattage is what matters.
---
The point is, ladies and gentleman, that speed, for lack of a better word, is good. Speed is right, Speed works. Speed clarifies, cuts through, and captures the essence of the evolutionary spirit.


Dave_Ryan

Jul 3, 13 12:36

Post #4 of 24 (2430 views)
Re: Bike trainer speed vs. road speed [Toby] [In reply to] Quote | Reply

Toby wrote:
..... Forget speed.... Wattage is what matters.


Too true, but pretty ironic given your signature line ;)

Quote:
The point is, ladies and gentleman, that speed, for lack of a better word, is good. Speed is right, Speed works. Speed clarifies, cuts through, and captures the essence of the evolutionary spirit.

But yeah, trainer speed is only relevant to your make and model of trainer and even things like the tires and pressure you run as well as press on force. In a general sense it has no relationship to speed on the road. But for specific trainers there can be a rough mapping like the way a Kurt Kinetic trainer attempts to emulate a 160 pound rider on a 1% uphill grade but it still won't map to flat riding in arbitrary wind conditions.

-Dave


(This post was edited by Dave_Ryan on Jul 3, 13 12:39)


dfroelich

Jul 3, 13 12:41

Post #5 of 24 (2408 views)
Re: Bike trainer speed vs. road speed [akrievins] [In reply to] Quote | Reply

Speed on the trainer is almost a worthless metric. Even if you ensure that every ride uses the same tire pressure and clamping force it would only be used to compare day to day trainer rides. But, that would still not have any bearing as a comparison to road riding.

Instead use RPE (good), a heart rate monitor (better) or a power meter (best) to equate trainer riding to road riding.


akrievins

Jul 3, 13 12:42

Post #6 of 24 (2404 views)
Re: Bike trainer speed vs. road speed [Dave_Ryan] [In reply to] Quote | Reply

Great replies so far. Very good information. I'm very Impressed with ST today! :)


BCDon

Jul 3, 13 12:54

Post #7 of 24 (2365 views)
Re: Bike trainer speed vs. road speed [akrievins] [In reply to] Quote | Reply

The two are really different. On my Computrainer I don't get to coast and the energy conserving techniques I use on the toad just don't work.

I haven't done the comparison but I definitely have to put out more on the CT than outside for the same given speed. Plus, if I decide to do a 40 Km flat TT on the Computrainer, there is no respite of any kind, I have to pretty much keep the same power output whereas on the road I'll have small bumps (or larger hills) which allow me to change cadence, pedaling style etc.

This past weekend I road for 3 1/2 hours on pathways around the city and had no issues with sore spots or anything similar. If I attempted that long a ride on my CT I would have been seeking relief from being in the same position all the time. Now, my speed outside on pathways wasn't all that great but I was out for an easier day to put in some saddle time.
BC Don
Pain is temporary, not giving it your all lasts all Winter.


tburke

Jul 3, 13 13:51

Post #8 of 24 (2306 views)
Re: Bike trainer speed vs. road speed [dfroelich] [In reply to] Quote | Reply

I would not call trainer speed a worthless metric when it is compared to day to day trainer rides, which can happen when outside riding is not possible. No doubt a power meter is best for trainer to road speed comparison.


125mph

Jul 3, 13 15:45

Post #9 of 24 (2221 views)
Re: Bike trainer speed vs. road speed [Toby] [In reply to] Quote | Reply

My Kinetic Kurt is spot on with speed, consistent day in and day out. I usually do intervals of 2x20', 3x10' or 4x10' and aim at going 20.5mph. Each time, the effort is very similar. From looking at my power meter numbers, the effort to achieve 20.5mph on the intervals is very consistent with the power meter as well.

My tire pressure is between 100-110psi and I always turn the clamp number 5 turns after it first makes contact with the tire. Anyway, to reiterate, I think speed on the training is a good number to rely on if you don't have a power meter and your training is delivering consistent pressure as mine is.


uphillisgood

Jul 3, 13 16:07

Post #10 of 24 (2199 views)
Re: Bike trainer speed vs. road speed [125mph] [In reply to] Quote | Reply

125mph wrote:
My Kinetic Kurt is spot on with speed, consistent day in and day out. I usually do intervals of 2x20', 3x10' or 4x10' and aim at going 20.5mph. Each time, the effort is very similar. From looking at my power meter numbers, the effort to achieve 20.5mph on the intervals is very consistent with the power meter as well.

My tire pressure is between 100-110psi and I always turn the clamp number 5 turns after it first makes contact with the tire. Anyway, to reiterate, I think speed on the training is a good number to rely on if you don't have a power meter and your training is delivering consistent pressure as mine is.

5 turns? I think the recommendation by KK is 2 1/4 turns. I've broken the "Z" bolt at 3 turns, but made a new one that has held up. I do get tire slip at 3 turns when ramping up the power. I'm not saying 5 turns isn't doable...just want to verify that that isn't a typo?

Thanks,
Bob


125mph

Jul 3, 13 16:09

Post #11 of 24 (2196 views)
Re: Bike trainer speed vs. road speed [bobonker] [In reply to] Quote | Reply

bobonker wrote:
5 turns? I think the recommendation by KK is 2 1/4 turns. I've broken the "Z" bolt at 3 turns, but made a new one that has held up. I do get tire slip at 3 turns when ramping up the power. I'm not saying 5 turns isn't doable...just want to verify that that isn't a typo?

Thanks,
Bob

Sorry, not 5 full turns. I just turn it 5 times and each one of my turns is about 1/2 a revolution.. so that ends up being around 2.5 turns.


asad137

Jul 3, 13 16:22

Post #12 of 24 (2181 views)
Re: Bike trainer speed vs. road speed [bobonker] [In reply to] Quote | Reply

bobonker wrote:
5 turns? I think the recommendation by KK is 2 1/4 turns.

FWIW, the manual says 2 to 5 turns.


astig

Jul 3, 13 16:36

Post #13 of 24 (2166 views)
Re: Bike trainer speed vs. road speed [akrievins] [In reply to] Quote | Reply

my KK road trainer (2.5 revs) is very close to the speed I get on my road bike with about the same power based on my quarq. The tri bike is about 2 mph faster outdoors vs trainer.


(This post was edited by astig on Jul 3, 13 16:37)


scofflaw

Jul 3, 13 16:50

Post #14 of 24 (2147 views)
Re: Bike trainer speed vs. road speed [astig] [In reply to] Quote | Reply

astig wrote:
my KK road trainer (2.5 revs) is very close to the speed I get on my road bike with about the same power based on my quarq. The tri bike is about 2 mph faster outdoors vs trainer.

"I used to wait two turns before I called my baby, but now it's like everybody waits two turns and two turns has become, like, industry standard . . . "

There was a thread on this not too long ago and if I remember, the only official line was "between two and five turns", like you microwave popcorn may take 2-5 minutes. Frustrating, but the consensus seemed to be then, as now, that 2.5-3 full turns will get you close if you're using Virtual Power.

The most important think is doing it the same every time, also as noted above.

And to partially answer the OP on the speed question, I am several mph slower on the KK than outdoors; I go 3 full turns.
_____________________________________
I've been left for dead before but I will fight on
Don't wait up leave the light on
I'll be home soon.


Nate Pearson

Jul 3, 13 19:55

Post #15 of 24 (2077 views)
Re: Bike trainer speed vs. road speed [dfroelich] [In reply to] Quote | Reply

dfroelich wrote:
Speed on the trainer is almost a worthless metric. Even if you ensure that every ride uses the same tire pressure and clamping force it would only be used to compare day to day trainer rides. But, that would still not have any bearing as a comparison to road riding.

Instead use RPE (good), a heart rate monitor (better) or a power meter (best) to equate trainer riding to road riding.

It is a worthless metric :). We don't show it in our software because it doesn't mean anything. We do allow people to export their files and speed is in there...much to my pain :).

As others have said go RPE, HR or power.
---------------------------------------------------------
http://www.trainerroad.com - Indoor Cycling Training System


125mph

Jul 3, 13 21:01

Post #16 of 24 (2027 views)
Re: Bike trainer speed vs. road speed [akrievins] [In reply to] Quote | Reply

To answer the OPs question, on a 10min interval, I can hit about 21mph on the trainer, 25mph on my TT bike on flat course, and 23mph on road bike on flat course. All these speeds are when I'm pushing around 250 watts.

So there is a difference as far as I can see in terms of speed for similar powers.


akrievins

Jul 4, 13 7:19

Post #17 of 24 (1918 views)
Re: Bike trainer speed vs. road speed [125mph] [In reply to] Quote | Reply

Good comparison! Thanks!


Doubletime

Jul 4, 13 7:26

Post #18 of 24 (1914 views)
Re: Bike trainer speed vs. road speed [akrievins] [In reply to] Quote | Reply

Its a STATIONARY trainer. You should expect a speed of 0.

Trying to correlate it to road speed is fruitless. Wind resistance goes up exponentaily with speed on road, but trainer resistance increases depending on what type of non-newtonial fluid you use (and then there are magnets and fans)...

If you have a powermeter - that works best.
HR is a acceptable proxy.
Amateurs like me simply use preceived effort to compare to road riding.
---------------------------------------------------------
- Nothing to see here. Move on.


asad137

Jul 4, 13 8:39

Post #19 of 24 (1877 views)
Re: Bike trainer speed vs. road speed [Doubletime] [In reply to] Quote | Reply

Doubletime wrote:
Wind resistance goes up exponentaily with speed on road,


power law, not exponential. (paging ZackCapets)


(This post was edited by asad137 on Jul 4, 13 8:40)


tburke

Jul 4, 13 12:30

Post #20 of 24 (1796 views)
Re: Bike trainer speed vs. road speed [scofflaw] [In reply to] Quote | Reply

In addition to the tire pressure & number of turns of resistance on the roller, another condition enters in when the wheel/bike is removed from the trainer. The wheel must contact the roller in a marked spot each time, because no wheel is perfectly round. This does make a difference, as I have found.


Toby

Jul 4, 13 12:38

Post #21 of 24 (1791 views)
Re: Bike trainer speed vs. road speed [tburke] [In reply to] Quote | Reply

tburke wrote:
In addition to the tire pressure & number of turns of resistance on the roller, another condition enters in when the wheel/bike is removed from the trainer. The wheel must contact the roller in a marked spot each time, because no wheel is perfectly round. This does make a difference, as I have found.

Wait, so I need to always clamp the roller to the wheel at, say, the valve stem?
---
The point is, ladies and gentleman, that speed, for lack of a better word, is good. Speed is right, Speed works. Speed clarifies, cuts through, and captures the essence of the evolutionary spirit.


tburke

Jul 4, 13 17:36

Post #22 of 24 (1723 views)
Re: Bike trainer speed vs. road speed [Toby] [In reply to] Quote | Reply

I find the highest point on the wheel (where the tire touches the roller) & make that the mark on the wheel & tire. The valve stem likely will work also. If you have to take the tire off, put it on in the same marked spot.


scofflaw

Jul 4, 13 17:40

Post #23 of 24 (1715 views)
Re: Bike trainer speed vs. road speed [tburke] [In reply to] Quote | Reply

tburke wrote:
In addition to the tire pressure & number of turns of resistance on the roller, another condition enters in when the wheel/bike is removed from the trainer. The wheel must contact the roller in a marked spot each time, because no wheel is perfectly round. This does make a difference, as I have found.

True, and square wheels are the RDs' latest attempt to slow me down.
_____________________________________
I've been left for dead before but I will fight on
Don't wait up leave the light on
I'll be home soon.


ZackCapets

Jul 5, 13 12:57

Post #24 of 24 (1547 views)
Re: Bike trainer speed vs. road speed [akrievins] [In reply to] Quote | Reply

By virtue of your CdA and tire rolling resistance you have a certain relationship between speed and power that you've come to experience as "real world riding." When you hop on the trainer you still have rolling resistance, but the trainer seeks to replace your aerodynamic drag with mechanical drag. The trainer speed-power curve is a generalized one that works fairly well for everyone, but if you're a tiny aero dude then the trainer will feel harder than riding outside, if you're a hefty dude that has a drag area comparable to a tractor trailer than the trainer will feel easy.

The speed-power curves are available for most trainers at their respective manufacturer's website. When purchasing a trainer it's worth considering this information as ultimately the "realism" of the ride is dictated by how closely the trainer's speed-power curve matches your real-world speed-power curve.

I see you Asad137!
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