FTP - whats yours?

['Dale]

Has anyone know why I'd be putting out more power on my road bike VS my mountain bike? I used both on the road and there is probably a 40-50watt difference in power. I'm not sure if anyone has answered this in the 20 000 previous comment

That's a big gap

 

I run power on both my bikes

The variable terrain affects my pedal stroke which renders different numbers

Could that be it?

[Slakkepas]

Has anyone know why I'd be putting out more power on my road bike VS my mountain bike? I used both on the road and there is probably a 40-50watt difference in power. I'm not sure if anyone has answered this in the 20 000 previous comment 

Power output over different brands differ.  I have vectors of roadbike and stages on mtb and its not the same.  I also differ outside on the bike and on the idt 

Edited May 27, 2016 by Slakkepas

[Eon du Plessis]

Power output over different brands differ. I have vectors of roadbike and stages on mtb and its not the same. I also differ outside on the bike and on the idt

The differences should be a few percentage points though, nothing as large as 50W.

['Dale]

The differences should be a few percentage points though, nothing as large as 50W.

Definitely

????????????????????????

[Vetplant]

Has anyone know why I'd be putting out more power on my road bike VS my mountain bike? I used both on the road and there is probably a 40-50watt difference in power. I'm not sure if anyone has answered this in the 20 000 previous comment

Where on the drive train are your power meters installed?

 

Are you using the same sensor and moving it between the two bikes?

 

If you are using different crank lengths and not adjusting for that you could see big differences..

[Slakkepas]

The differences should be a few percentage points though, nothing as large as 50W.

I use my road bike (vector pedals) on my tacx genius, so have the power from both.  Running them simultaneously the power difference is 10%.  But yea 50w is a lot.

[Eon du Plessis]

I use my road bike (vector pedals) on my tacx genius, so have the power from both. Running them simultaneously the power difference is 10%. But yea 50w is a lot.

Look that I can understand. The trainer measures at the wheel, so whatever losses you have through your drive train, won't be taken into account. Feathering the brakes while pedalling will have the trainer show you a way lower power reading than the pedals.

The pedals are probably the more correct of the two, if I had to guess.

[Saudiq]

I’ve been switching my stages PM between my road and mountain bike (and yes, I know the Q-factor is out by 4mm but with one leg 2cm longer than the other and number of other factors, this really hasn’t bothered me at and all both cranks are 175mm) I’ve only been riding my MTB since the Argus and when I did threshold training 2 weeks ago I struggled to maintain 250w. When I jumped on my road bike this week I managed 2 intervals at 300 – 310w which was hard but very manageable. My peak in November was 350w for 20min interval. 

[Slakkepas]

Look that I can understand. The trainer measures at the wheel, so whatever losses you have through your drive train, won't be taken into account. Feathering the brakes while pedalling will have the trainer show you a way lower power reading than the pedals.

The pedals are probably the more correct of the two, if I had to guess.

The trainers reading is 10% higher than the pedals.  think the software is the key factor in the differences shown.  Actual can have many factors

Edited May 27, 2016 by Slakkepas

[Eon du Plessis]

The trainers reading is 10% higher than the pedals. think the software is the key factor in the differences shown. Actual can have many factors

I assume everything is calibrated?

[Slakkepas]

I assume everything is calibrated?

before every ride 

[jcza]

I’ve been switching my stages PM between my road and mountain bike (and yes, I know the Q-factor is out by 4mm but with one leg 2cm longer than the other and number of other factors, this really hasn’t bothered me at and all both cranks are 175mm) I’ve only been riding my MTB since the Argus and when I did threshold training 2 weeks ago I struggled to maintain 250w. When I jumped on my road bike this week I managed 2 intervals at 300 – 310w which was hard but very manageable. My peak in November was 350w for 20min interval. 

 

Sounds very strange, lost 100W?

[usxorf]

I’ve been switching my stages PM between my road and mountain bike (and yes, I know the Q-factor is out by 4mm but with one leg 2cm longer than the other and number of other factors, this really hasn’t bothered me at and all both cranks are 175mm) I’ve only been riding my MTB since the Argus and when I did threshold training 2 weeks ago I struggled to maintain 250w. When I jumped on my road bike this week I managed 2 intervals at 300 – 310w which was hard but very manageable. My peak in November was 350w for 20min interval. 

Fatigue maybe? Did you test on the same stretch of road? Unless you have some serious fit issue on mtb compared to road.

 

I have power on road and mtb and the numbers are very similar depending on terrain.

 

As an aside, spinscan showed a discrepency of 65-35 or more at low cadence for me (49/51 at 95-100rpm). Stages being one-sided and road usually at 95rpm vs 75rpm on mtb, might just be a reading error. Borrow someone's powertap for your mtb if you can.

Edited May 27, 2016 by usxorf

['Dale]

Sounds very strange, lost 100W?

Very strange indeed

Mystery

[V12man]

I’ve been switching my stages PM between my road and mountain bike (and yes, I know the Q-factor is out by 4mm but with one leg 2cm longer than the other and number of other factors, this really hasn’t bothered me at and all both cranks are 175mm) I’ve only been riding my MTB since the Argus and when I did threshold training 2 weeks ago I struggled to maintain 250w. When I jumped on my road bike this week I managed 2 intervals at 300 – 310w which was hard but very manageable. My peak in November was 350w for 20min interval. 

Are you recalibrating the stages each time you move it?

[Saudiq]

Fatigue maybe? Did you test on the same stretch of road? Unless you have some serious fit issue on mtb compared to road.

 

I have power on road and mtb and the numbers are very similar depending on terrain.

 

As an aside, spinscan showed a discrepency of 65-35 or more at low cadence for me (49/51 at 95-100rpm). Stages being one-sided and road usually at 95rpm vs 75rpm on mtb, might just be a reading error. Borrow someone's powertap for your mtb if you can.

 

No, I also used heart rate variability to check how fatigued I am and it was pretty similar. Yes, same stretch of road as well.

 

Could this possibly be due to my MTB setup? I've checked saddle height and used plum bomb to check fore-aft and seems right