which computrainer

slowfoot said:

i'm looking to buy a used computrainer

can you guys fill me in on the pros or cons of the models?

i frequently see 8001's for sale much cheaper than the pro 3d models. does it matter much?
it will get a lot of use due to long off seasons and much bad weather here.

thanks

dave

i don't know the gory details on the older units. Personally I think I'd stick to one no more than five years old and preferably less than that.

Some of the older units can be way off. Personally I experienced that with one the LBS brought in for a junior team in the mid 90's. That sucker made everyone feel like Indurain!! That's not to say they cannot be adjusted in the field but I'm not *sure* that can be done. I believe the load-gen max. power was 1000W back then vs. 1500W currently. That would likely make little difference unless you want to try sprint workouts indoors.

Basic vs. Pro3D vs. ProLab are your options now and there no difference in the hardware either way. Add on software and the Basic goes to 3D. Add extra calibration checks (linearity) and you have a Lab version. They are all good.

thanks,
it's always tempting to pounce on a cheap unit..
i guess that's a reason the pro and lab go for much more.

now back to ebay "watching"

dave

slowfoot said:

i'm looking to buy a used computrainer

can you guys fill me in on the pros or cons of the models?

i frequently see 8001's for sale much cheaper than the pro 3d models. does it matter much?
it will get a lot of use due to long off seasons and much bad weather here.

thanks

dave

computrainer.commodel notes.htmOpen ↗

Check this link out from racermate's site -- it gives you the specifics of the various models and how they have changed over time. If you go the used route, you should be able to figure out if it's upgradeable (to 3D if an older unit, etc) and approx. when the unit was made.

As for my own experience, I first bought my unit as a Nintendo Pro version back in early '96. It's bomb proof, very accurate and I've upgraded it to the 3D system a couple of years ago for a $200 or so. Agree with rmur, I would avoid one over 5 years old -- it's a piece of electronics and you just don't know how it may have been treated.

Plus, the older ones on ebay may also be the Nintendo "donkey-kong" version. I suspect that you would want to upgrade to 3D for when you aren't using ergo mode. It's much nicer to look at and you can download files for review in WKO+, etc. You would need to add that cost to the equation. You also need to note that some of the old NES models aren't so cheaply upgraded to 3D (depends on load generator model).

No doubt a CT is a pretty expensive piece of equipment new (and the ebay prices I've seen really aren't that much of a discount) but my CT is, hands down, the single best piece of cycling equipment that I have ever purchased in 22+ years of racing. This is the 13th winter I've been on it. I don't know how may frames, wheelsets, etc. I've been through in that same time period.

I posted a Racermate Computrainer PRO #8001 Bicycle Indoor Trainer yesterday in the classified ads. It was used about 2 seasons and then moth-balled. It's practically perfect. The software is included, but it was purchased in 2000, so you may want a later version. I ran the unit mostly without the software interface.

Kim

I tried out a used 8001 Computrainer today I spotted on a craigslist ad. The copyright on the CD case was from 1999-2000, so I assume this is about how old it was? After doing the warm-up and coast down per the manual it read about ~50 watts lower than my Power Tap. I went through a range of 50 to 250 watts, and when it was set to 200 watts my powertap was reading about 250. Is this typical of the Computrainers? Is the 8002 any better in this regard?
My Powertap is only a few months old and seems very consistent. I plan to put a bike on the CT with no power tap, so I'd like them to track reasonably well.

strader said:

I tried out a used 8001 Computrainer today I spotted on a craigslist ad. The copyright on the CD case was from 1999-2000, so I assume this is about how old it was? After doing the warm-up and coast down per the manual it read about ~50 watts lower than my Power Tap. I went through a range of 50 to 250 watts, and when it was set to 200 watts my powertap was reading about 250. Is this typical of the Computrainers? Is the 8002 any better in this regard?
My Powertap is only a few months old and seems very consistent. I plan to put a bike on the CT with no power tap, so I'd like them to track reasonably well.

50W low I'd suggest is way outside the norm. A batch of 2002 models I tested (and later corrected) were off from 4-8% - all reading low but here you're talking ~20%?

It's possible there's a problem with how you checked the unit (assuming you're not really familiar with them). Or the load-generator could be way off on this unit.

Would you mind describing exactly how you did the RRC check? Are you sure the check was repeatable and you accepted the final setting? Did you zero out the PT?

Not saying you did anything wrong but over the years, when folks have reported large discrepancies - procedural issues have been the root cause rather than either of the devices per se.

If everything is up to snuff, then there could be a slope (correctable) problem with the l/g or there could be a problem with the RRC (zero-ing) hardware ... in which case it's back to Racermate!

rmur17 said:

Would you mind describing exactly how you did the RRC check? Are you sure the check was repeatable and you accepted the final setting? Did you zero out the PT?

Yeah, it's definetly possible I screwed something up in the calibration. The people who had it bought it to train for a tri, and then never used it. They did not know how to calibrate it or put it in erg mode (or know what ergometer mode was). Basically what I did was hop on the machine, pedal for a few minutes at 150 watts, enter the calibration menu (+ and - key) and spin up until it stops displaying "UP", then do the coast down and go back to erg mode by pressing F2. I rode for a few more minutes in erg mode, noticed how far off the wattage numbers were, and tried the calibration a second time to see if the unit just needed more warm up time. Same result.
As far as my powertap... I have it set to auto zero, and I've read you still need to perform the manual coast down, which of course I didn't do. :o The numbers it was displaying felt right based on RPE. I think if I did a ftp test on that computrainer it would put my FTP at around 220 watts. I'd like to think my race results this season are better than what 3.2 w/kg would indicate. 😉
Thanks!

strader said:

... Basically what I did was hop on the machine, pedal for a few minutes at 150 watts, enter the calibration menu (+ and - key) and spin up until it stops displaying "UP", then do the coast down and go back to erg mode by pressing F2. I rode for a few more minutes in erg mode, noticed how far off the wattage numbers were, and tried the calibration a second time to see if the unit just needed more warm up time. Same result....

Something that the manual doesn't really make clear is that the roll down calibration number is directly related to pounds of press on force. If your roll down numbers don't come pretty close to 2.00 then you should start by increasing or decreasing roller tension until you get a number close to 2.00. You should also warm up for longer at a higher power. It takes me 15 minutes or more to get stable roll down readings at 150 watts but if I ride warmups up to 220-250 watts I get stable roll down values in five to six minutes.

If you're consistently getting stable roll down values near 2.00 and your CT power readings still don't agree with your PT then it's time to talk to rmur about the going price on his very valuable calibration protocol. I ran through that with mine a few months ago and now my PT and CT track each other within a couple of watts.

-Dave

Right I forgot about that part. It displayed 3.1 after the second coast down. In the manual I thought it said any coast down value under 5 was okay?
I'll have to think about whether I want to drive clear across town again to check it out. They said $800 was their firm price, but if I end up having to send it back to Racermate I might be better off paying more up front for a newer unit.
Thanks for the help guys.

strader said:

Yeah, it's definetly possible I screwed something up in the calibration. The people who had it bought it to train for a tri, and then never used it. They did not know how to calibrate it or put it in erg mode (or know what ergometer mode was). Basically what I did was hop on the machine, pedal for a few minutes at 150 watts, enter the calibration menu (+ and - key) and spin up until it stops displaying "UP", then do the coast down and go back to erg mode by pressing F2.

But did you hit F3 in there anywhere to accept and set the 'calibration' number? Do you recall the 'cal' numbers you were seeing?

I rode for a few more minutes in erg mode, noticed how far off the wattage numbers were, and tried the calibration a second time to see if the unit just needed more warm up time. Same result.

okay - no problem as long as you accepted/set the value. IIRC, if uncalibated the Watt display continues to flash in ergo mode. Then again, it's been a while since I messed with that. I shoot for rrc #'s around 2.00 +/- 0.10 (units are lbf so I'm told).

As far as my powertap... I have it set to auto zero, and I've read you still need to perform the manual coast down, which of course I didn't do. :o The numbers it was displaying felt right based on RPE.

what I do (every so often when I check the CT against the PT) is to pop the bike on the CT stand w/o the roller applied and spin over the rear wheel unloaded - the auto-zero routine picks that up just fine.

I think if I did a ftp test on that computrainer it would put my FTP at around 220 watts. I'd like to think my race results this season are better than what 3.2 w/kg would indicate. 😉
Thanks!

no problem ..

strader said:

Right I forgot about that part. It displayed 3.1 after the second coast down. In the manual I thought it said any coast down value under 5 was okay?
I'll have to think about whether I want to drive clear across town again to check it out. They said $800 was their firm price, but if I end up having to send it back to Racermate I might be better off paying more up front for a newer unit.
Thanks for the help guys.

there is a reasonably good chance there will be a cheaper option than sending it back. I figure it's worth another check! $800 is about half-price on a new unit ...

daveryanwyoming said:

If you're consistently getting stable roll down values near 2.00 and your CT power readings still don't agree with your PT then it's time to talk to rmur about the going price on his very valuable calibration protocol. I ran through that with mine a few months ago and now my PT and CT track each other within a couple of watts.

I don't have a CT but I use one every so often. Just curious - is there a way to offset the torque (I assume that it is measuring torque) by a slope and intercept factor in the CT software so that the displayed power is "right"? Or does Rick's magic method involve fooling the CT by mucking with the coast down calibration?

Steve_B said:

I don't have a CT but I use one every so often. Just curious - is there a way to offset the torque (I assume that it is measuring torque) by a slope and intercept factor in the CT software so that the displayed power is "right"? Or does Rick's magic method involve fooling the CT by mucking with the coast down calibration?

There's a slope calibration potentiometer hidden in the unit. Tweaking the slope allows you to user calibrate the unit but it also voids the warranty.

-Dave

daveryanwyoming said:

There's a slope calibration potentiometer hidden in the unit. Tweaking the slope allows you to user calibrate the unit but it also voids the warranty.

-Dave

Pots (potentiometers) are usually sealed (held at a setting) with something akin to nailpolish. In fact, that's exactly what we used to use at one of my previous employers. (The Ruby Red shade clashed with my eye color though. 😉 ) If you tweak the pot then seal it again (assuming they sealed it at the factory), they might never know, unless they have some stored data from factory cal that they would refer to, if you ever sent it back to them.

I ended up picking up the Computrainer after all. I did a quick test on it after a 15 minute warm up at ~200 watts, and a calibration value of 2.05 lbs. Here's how it compared to my powertap (which I remembered to zero this time) over three 5 minute trials at 300, 250, and 200 watts:

Computrainer Powertap
300 watts 316 watts -5.1%
250 watts 264 watts -5.3%
200 watts 212 watts -5.6%

Not bad, but I'd like them to track a bit closer. 316 watts feels a lot harder for me than 300.
The unit also develops a nasty buzz at around 22 mph wheel speed. I can feel it though the bike. Could it just be an unbalanced tire? Something loose on the trainer? Right now I'm using a Michelin Carbon, but I have a conti home trainer tire sitting in a box waiting to be used.

strader said:

I ended up picking up the Computrainer after all. I did a quick test on it after a 15 minute warm up at ~200 watts, and a calibration value of 2.05 lbs. Here's how it compared to my powertap (which I remembered to zero this time) over three 5 minute trials at 300, 250, and 200 watts:

Computrainer Powertap
300 watts 316 watts -5.1%
250 watts 264 watts -5.3%
200 watts 212 watts -5.6%

Not bad, but I'd like them to track a bit closer. 316 watts feels a lot harder for me than 300.
The unit also develops a nasty buzz at around 22 mph wheel speed. I can feel it though the bike. Could it just be an unbalanced tire? Something loose on the trainer? Right now I'm using a Michelin Carbon, but I have a conti home trainer tire sitting in a box waiting to be used.

Hi

FWIW my advice would be as follows:

1. Fit Conti tyre.
   
2. Inflate to 110psi.
   
3. Run routine and set calibration with trainer and tyre cold, ensure press on force is about 3lbs at this stage.
   
4. Warm up tyre and trainer for 10 minutes, at least 8 minutes done @ 175W.
   
5. Recalibrate trainer, this should now give you a press on force of about 2.4-2.6lbs.
   
6. You are now properly calibrated, perform tests at about 90RPM , away you go, post results here 😉
   
7. Re-run calibration after tests, the reading should be VERY close to the reading obtained in step 5, if the unit and tyre were properly warmed up.
   

My experience is that with press on forces in the lower end of the range, and 2 is the absolute minimum, you may well get "micro slips" of the tyre, especially at higher wattages if the cadence is lowish, the above routine avoids this. Bear in mind if you are going to do any work standing up, steep gradient settings, high wattages, you may well need to set a press on force of above 3 to avoid "micro slips" which are not obvious when they are happening on any trainer.

Can't help you will the buzz!

Cheers.

PBUK

In case anyone is interested in the follow-up, after following rmur's calibration procedure my computrainer and powertap track much closer:

CT PT % diff
300 299 -0.3%
250 252 0.7%
200 204 1.9%
150 156 3.8%

The slopes cross over around 280ish watts, which I call Good Enough (TM). I figure workouts paced by either one should be within a couple of TSS points.

Hi Strader

strader said:

In case anyone is interested in the follow-up, after following rmur's calibration procedure my computrainer and powertap track much closer:

CT PT % diff
300 299 -0.3%
250 252 0.7%
200 204 1.9%
150 156 3.8%

The slopes cross over around 280ish watts, which I call Good Enough (TM). I figure workouts paced by either one should be within a couple of TSS points.

I've re-read the thread and am not quite clear in my own mind exactly which exactly is rmurs callibration procedure as based on your experiences I'd like to try following it. Any chance of a 1,2,3 noddy guide?

Thanks for your help.

PBUK