PT SL -- Loss of signal when coasting

JIM WV

Is this normal? After training for years with HR, I took the plunge and picked up a new PT SL last weekend. Went through my "normal" week with the PT mounted just to learn the thing. Anyways, I've put about 225 miles on the clock and it loses signal when coasting, probably about 50% of the time.

It seems to lose signal once I quit pedaling and the watts wind down to near zero -- then both watts and speed functions give the - - - - Sometimes, while I am still coasting, it regains signal and does display current speed and watts as zero. Otherwise, it stays dead until I pedal -- and then it does pick up immediately. It never loses signal or is erratic when pedaling.

Any thoughts? I would imagine that it is usual to lose signal from time to time, but today I lost more than a few miles on a 60 mile ride and it lost signal on virtually every significant descent. I've played around with the sensor and I can intentionally misadjust it and the thing works when pedaling. Since it is new, I can't believe the batteries would be weak -- and, like I said, it picks up straight-away when pedaling.

Can't wait to get the thing dialed in and run some tests, especially since I am riding well right now. After racing/training for 20 years, this thing has me more motivated than a new bike! Thanks in advance.

RapDaddyo

It sounds as though what is happening is that the hub is going to "sleep." If you have done setup to have the computer get cadence from the hub, this will cause a loss of basically all data (except HR) to the computer. According to the manual, the hub goes to sleep after 2 minutes, to conserve battery life. The computer sleep interval is user-definable (default = 4 min). My SL hub occasionally goes to sleep if I'm coasting, and it doesn't seem to take 2 minutes, but I rarely coast so it's not much of an inconvenience. If you put any kind of a load on the hub, it should come back instantly. You might contact Saris to see if there is any way to lengthen the hub sleep interval. I doubt it, but you never know.

beerco

There was a bad batch of PTs - sounds like you may have gotten one of them (NOS) send it back for repair.

pato123

I have the same problem. Probably need to update the cpu firmware but im not sure

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Gil

JIM WV

Thanks for the responses. After reading the manual front to back and tinkering with everything to no avail I swapped out the batteries in the hub. Voila. It doesn't drop the signal. Rock solid.

After reading Stormer's thread, I thought oh no, maybe I got a bad one (not as bad as his experience though!)

pato123

I will try that. Thanks

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Gil

peterwright

I also have the same problem and having changed the batteries have not got rid of the problem. PT have now said that there is a problem with the receiver and I should put more sponge underneath it to reduce vibration - they are redoing it in a few months but suggest that this should solve it in the meantime. Sounds very odd to me but maybe more vibration when not pedalling ?

Peter

JIM WV

Peter, this is kind of odd -- last week I adjusted the receiver a bit -- shimmed it with a piece of inner tube. I also changed out the batteries. It started working great and I figured that the batteries fixed the issue as the shim didn't really change the receiver alignment but for a few millimeters. Well, yesterday I took the whole thing off the bike and put it onto another bike of mine using the same measurements as the first frame. I didn't need to shim the receiver at all on the 2nd bike as the receiver was just about perfect to the hub. Figured it would work fine. Well, it started dropping the signal when coasting again. Can't be the batteries so I called cycleops and got the same information as you. I was told that the freewheel on the SL has much larger pawls than the Pro model such that it can create vibration interference with the receiver. It is a loud mechanism when coasting but not unduly so. My inner tube shim may have been reducing the vibration without me even realizing that was the initial problem -- heck, I thought the battery swap did it. I am a bit skeptical as well given that the first frame is a carbon C50 and I would think that folks riding alu frames would have reported this problem long ago. . . The thing just doesn't transmit vibration. I'll try insulating the receiver on my 2nd bike and I'll let you know if it works.

RapDaddyo

FWIW, I did a little testing on my ride today. I did 4 hillclimb repeats on a 3.3 mile course, so I had plenty of time to coast. I was able to get my SL to drop the hub/receiver link a few times, but only when I was completely coasting (not turning over the pedals at all). Each time I was able to instantly re-acquire the hub transmission icon by just turning over the pedals enough to reduce the freewheel to an intermittent clickety-click rather than the full-blown buzz when I'm not turning over the pedals at all. IOW, I didn't have to actually put a load on the hub and generate watts, but rather just quiet the freewheel a bit by turning over the crank. I was never able to drop the transmission icon when I was turning over the crank while descending. Since I rarely completely coast, I think this explains why I rarely get hub transmission dropouts. What I don't know is whether the freewheel causes a problem with the hub transmission or the receiver and whether it's a vibration issue or sound frequency issue.

JIM WV

Thanks, Rap. You have pretty much described how mine works as well. If I just turn my legs over a bit, no load on the hub, it will usually keep the signal. I don't coast much either, but there are more than a few descents around here that you have got to tuck in to stay on and soft pedaling all the way down just isn't feasible. I know it's a training device and coasting 'aint training. It's just annoying to lose the signal.

Anyways, I finally got some free time tonight to work with the attempt at insulating the receiver. I can get the thing to drop signal coasting and also if I mount the bike in a workstand and wind up a big gear and then "back pedal" while the rear wheel is free wheeling -- really get the freehub buzzing. First, I used a number of inner tube shims (single and also a few stacked). These didn't work. Signal was still dropped riding or in the stand. I tried the small piece of sticker foam that was factory supplied with the PT to stop the receiver from slipping. Likewise, it did nothing. Finally, I used a small piece of cut foam (the type that you get with a BMX bike crossbar pad). It seems to work. Despite my best efforts, I can't drop the signal on the workstand nor did I drop it during a short ride. I have my fingers crossed as tomorrow, I've got a long day in the saddle planned for my training for the Cheat Mountain Classic at Snowshoe. I'll post whether the fix ultimately works.

RapDaddyo

That's very interesting. As I said, I'm not sure this is a vibration issue. I'd bet you could get it to drop the signal even if it was mounted on something not attached to the frame at all. It may be a sound frequency issue. I have an idea that they have a fix in the works that will involve a new receiver. I just hope they don't charge full price for the upgrade. I suggest that you formally register your problem in writing, to benefit from any upgraded receiver pricing to units within warranty. I plan to send a letter about my unit even though the signal drops are pretty infrequent. I think the warranty is 1 year.

JIM WV

Well, I got back from a five hour run through what started as a grey day and ended with three hours in a downpour. Pleased that the PT didn't drop the signal at all. Went down many of the same descents that would cause it to fall off quick and it stayed connected. I did lose the signal the last 20 minutes -- the computer contacts finally got wet despite the plastic bag that I slipped over it when it really starting coming down. No biggie, that can happen obviously and it was a soaker. I wouldn't have taken it out if I knew that the sky was going to let loose that bad. I am going to pull the hub battery cover off just to air everything out and regrease the o-rings, etc.

Rap, good suggestion regarding the registration/letter. I am going to register it and send a some type of letter formally complaining. When I called the lady on the phone did explain that they were working on a new receiver to remedy the problem and, frankly, I am with you -- it should be supplied at a discout, at least. Given how I have heard from others with PT problems and the customer service, I would bet that they will take care of us. It really shouldn't take backyard engineering with a piece of foam to fix something that costs this much.

RapDaddyo

Good solution. So, did you wrap the foam around the stay and then put the zip ties around the foam? Or did you just put a piece of foam between the stay and the receiver?

JIM WV

Just a nice thick piece (maybe 1/4 inch) between the stay and the receiver. It's not too noticeable especially since the foam is the same color as the black stay and receiver.