PT SL, Huge difference between two units.

[Shawneebiker]

Here's the situation.

I just purchase a new PT SL Harwired unit. Version 4.xx.

I have a year and a half old PT SL Hardwired software version 2.xx unit that was serviced approximately 6 months ago from Saris.

The new unit is reading approximately 45-50 watts difference using my rollers testing at speeds of 20 mph. My old unit reads approximately 270 watts at 20mph and the new one shows approximately 225 watts.

I noticed after I had trouble completing my 2 x 20's the last few times. PE of these efforts caused me to check.

I have zeroed both units before testing. The torque reading on the old one is 520 and the new one 518. I have equal tire pressure in both and tires are only about 5mm difference in size.

The only noticeable difference in the two units is when I go under the diagnostics the new one under section #5 it shows cadence sometimes when there is no cadence. The old unit shows no cadence immediately after cadence has stopped. The new one fluctuates wildly before stopping and then sometimes showing cadence again.

I've never had any reason to question my power numbers from the old unit in the past.

Any ideas?

I plan on calling Saris tomorrow.

 

[Alex Simmons]

Here's the situation.

I just purchase a new PT SL Harwired unit. Version 4.xx.

I have a year and a half old PT SL Hardwired software version 2.xx unit that was serviced approximately 6 months ago from Saris.

The new unit is reading approximately 45-50 watts difference using my rollers testing at speeds of 20 mph. My old unit reads approximately 270 watts at 20mph and the new one shows approximately 225 watts.

I noticed after I had trouble completing my 2 x 20's the last few times. PE of these efforts caused me to check.

I have zeroed both units before testing. The torque reading on the old one is 520 and the new one 518. I have equal tire pressure in both and tires are only about 5mm difference in size.

The only noticeable difference in the two units is when I go under the diagnostics the new one under section #5 it shows cadence sometimes when there is no cadence. The old unit shows no cadence immediately after cadence has stopped. The new one fluctuates wildly before stopping and then sometimes showing cadence again.

I've never had any reason to question my power numbers from the old unit in the past.

Any ideas?

I plan on calling Saris tomorrow.

What happens when you do a calibration check with a known weight in the same gear for both hubs?

 

[Shawneebiker]

What happens when you do a calibration check with a known weight in the same gear for both hubs?

Here's what I found out. Not the results I was hoping for.

Used measured weghts of 49.54lbs. Hung it on the right crank arm at 3 o'clock. Zero'd torque on both units before hand.

New unit results were: 78 inch pounds displayed. So 49.54 x 175 x 1 /25.4 x 12/53=77.28. Pretty darn close.

Old unit results were: 88 inch pounds displayed. So if I'm correct that is about a 14% error with my old unit.

Am I doing this correctly???????

Guess I'm going to need to adjust my FTP.

 

[frenchyge]

Sounds like we need to set up a calibration party.

I called Saris yesterday about my older (yellow) PT Pro. They are trying to phase those units out and have limited parts availability, but they said they could do an "electronics overhaul" on my unit for $200, or give me credit towards a new purchase.

 

[rmur17]

Here's what I found out. Not the results I was hoping for.

Used measured weghts of 49.54lbs. Hung it on the right crank arm at 3 o'clock. Zero'd torque on both units before hand.

New unit results were: 78 inch pounds displayed. So 49.54 x 175 x 1 /25.4 x 12/53=77.28. Pretty darn close.

Old unit results were: 88 inch pounds displayed. So if I'm correct that is about a 14% error with my old unit.

Am I doing this correctly???????

Guess I'm going to need to adjust my FTP.

check out this thread first ...

http://www.cyclingforums.com/t451863.html

 

[Shawneebiker]

Sounds like we need to set up a calibration party.

I called Saris yesterday about my older (yellow) PT Pro. They are trying to phase those units out and have limited parts availability, but they said they could do an "electronics overhaul" on my unit for $200, or give me credit towards a new purchase.

Let me know, I'm available.

I talked to Saris and basically they said that since the torque offset was within range the unit was working properly. I knew that, my problem is the two units aren't accurate between them.

Really sucks I'm going to have to lower my FTP by 40 or so watts.

I'm sending it to Saris for re-calibration.

 

[frenchyge]

I'm sending it to Saris for re-calibration.

Will they do it for free since it was just reworked so recently? What was the problem when you sent it in before?

 

[Shawneebiker]

Will they do it for free since it was just reworked so recently? What was the problem when you sent it in before?

No there's an $89 charge. The problem before was my LBS (you know who) installed ceramic bearings and while doing so messed up the torque tube so it had to be sent to Saris for repair.

 

[J-V]

No there's an $89 charge. The problem before was my LBS (you know who) installed ceramic bearings and while doing so messed up the torque tube so it had to be sent to Saris for repair.

Perhaps Saris did not repair it correctly, and it was never completely fixed? I'd pursue that angle pretty hard before paying them $200...

 

[kennf]

The power/speed levels on the newer unit sound more reasonable. 270 watts seems like a lot of power for 20 mph.

 

[Hitchy]

The power/speed levels on the newer unit sound more reasonable. 270 watts seems like a lot of power for 20 mph.

...not if you're riding up a 13% gradient!

 

[swampy1970]

Here's the situation.

I just purchase a new PT SL Harwired unit. Version 4.xx.

I have a year and a half old PT SL Hardwired software version 2.xx unit that was serviced approximately 6 months ago from Saris.

The new unit is reading approximately 45-50 watts difference using my rollers testing at speeds of 20 mph. My old unit reads approximately 270 watts at 20mph and the new one shows approximately 225 watts.

I noticed after I had trouble completing my 2 x 20's the last few times. PE of these efforts caused me to check.

I have zeroed both units before testing. The torque reading on the old one is 520 and the new one 518. I have equal tire pressure in both and tires are only about 5mm difference in size.

The only noticeable difference in the two units is when I go under the diagnostics the new one under section #5 it shows cadence sometimes when there is no cadence. The old unit shows no cadence immediately after cadence has stopped. The new one fluctuates wildly before stopping and then sometimes showing cadence again.

I've never had any reason to question my power numbers from the old unit in the past.

Any ideas?

I plan on calling Saris tomorrow.

270watts for 20mph - I'd take off the cyclo-cross tyres and mount something a little smoother or stop riding on the tops! 270watts should be getting you about 24mph on the roadbike on the drops.

 

[Tim Lamkin]

...not if you're riding up a 13% gradient!

...and a head wind...

 

[Shawneebiker]

Here's the situation.

I just purchase a new PT SL Harwired unit. Version 4.xx.

I have a year and a half old PT SL Hardwired software version 2.xx unit that was serviced approximately 6 months ago from Saris.

The new unit is reading approximately 45-50 watts difference using my rollers testing at speeds of 20 mph. My old unit reads approximately 270 watts at 20mph and the new one shows approximately 225 watts.

I noticed after I had trouble completing my 2 x 20's the last few times. PE of these efforts caused me to check.

I have zeroed both units before testing. The torque reading on the old one is 520 and the new one 518. I have equal tire pressure in both and tires are only about 5mm difference in size.

The only noticeable difference in the two units is when I go under the diagnostics the new one under section #5 it shows cadence sometimes when there is no cadence. The old unit shows no cadence immediately after cadence has stopped. The new one fluctuates wildly before stopping and then sometimes showing cadence again.

I've never had any reason to question my power numbers from the old unit in the past.

Any ideas?

I plan on calling Saris tomorrow.

Or just read the OP!

 

[swampy1970]

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Or just read the OP!

Do I have too? I spent many an hour today getting in some quality miles and neigh on 7,000ft of climbing... It doesn't take rocket science to figure out that the unit showing 270watts for 20mph needs some attention.