BBS02 PAS not torque sensing, will I be disappointed?

I'm doing research for my first build and trying to decide between two systems, both mid-drives.

My donor bike will be a new Specialized Roll Sport, or Elite comfort bike. I'm 64 and ride neighborhood streets and bike trails for fun and exercise. I'm not commuting and do not want a throttle because they are not allowed on bike trails, plus I ride for exercise as stated.

I was all set to order a BBS02 kit from Luna until I discovered the PAS system is not torque sensing. I've read that it can give unexpected bursts of power, which is a concern to me. Sounds like it's either on, or off.

The TSDZ2 system is torque sensing and from what I've read it sounds like it would work like a factory bike that uses a Shimano Steps, or Bosch system. I have ridden bikes built on these two systems and really like the simplicity and natural bike feel. Like riding a real bike, but with stronger legs. However, I get the impression that most builders are going with BBSxx motors, plus they are less money and seam to be reliable with available parts if needed.

What is it like riding a bike using only the PAS on a BBS02 bike? What can I expect? It's a lot of money to build a bike and I want to get it right the first time. Someone told me with up to 9 levels of assist, I could find a setting that works, is that correct? I see you can add a torque sensor from another company, but it sounds complicated and you need to drill a 10mm hole through the BB, plus the added expense.

Any thoughts on helping me decide would be much appreciated.

The two forms torque sensing and non sensing are like chalk and cheese on the trail, much less so on the road. The Bafung series were built to put on Chinese commuter bikes, the Chinese don't do exercise on the way to work, the Bafung therefore was designed as a pedal and go, push the pedals and the bike will ramp up the power until you reach the speed you want and hey presto you are at work without a sweat.

The TDSZ2 is a torque sensing beastie and if you don't put any energy in, it won't either. Simple, it makes you pedal harder and it will match you by a percentage depending on what mode you have it in, not unlike the Bosch and Yamaha versions.

On the trail the BB series are a pain in some ways, you have to be prepared to program it to your requirements, from the factory they are terrible off road. But there are plenty of programs available and they program pretty easily and you can get them sort of good particularly if you have some sort of impediment such as a damaged knee or fitness problems. I have mine now where its comfortable off road but more like a small motorbike than a pedal bike. They also require quite a lot more hardware on the bike such as brake cutoffs as they can be somewhat slow in shutting power down on single track style riding.

The TDSZ2 is very simple, doesn't need brake shut offs and stops instantly the second you stop peddling, but it needs you to get sweaty and put in some effort. On the off road trails its actually very good and an equal to the Bosch I have ridden with the plus of being able to remove the speed limit. Downside is the reliability is similar to the early Bafungs, improving as they get used more and if you ride them sensibly they are a rewarding ride. Forget to change into the gear before stopping that you need for the next start and with the added torque and you giving it a big heave, the blue gear can be an issue but resolvable by fitting the widely available brass gear, ride them as you would a mtb bike and you won't have any problems.

Good assessment above on the BBS02. I haven't tried the TD because there have been too many reports of quality issues (for me). I'm on my third BBS02 (my wife rides one of them) and all function well. The biggest challenge with the RPM-based PAS on the BBS02 is you need to keep pedaling or the system shuts down almost immediately. When I'm riding a tight uphill switchback or over a very gnarly obstacle I need to pedal smoothly or it's hike-a-bike time. I've ridden many torque-based OEM systems and this isn't a problem with them since as long as there is pressure on the pedals, the motor keeps providing assistance. Can't wait to try a TD when/if they solve their manufacturing inconsistencies.

I'm not sure you're being a bit harsh on the manufacturing problems, there's an awful lot out there now and only a few reports of damaged units due to over loading the unit on the start of peddling ( wrong gear selected ), many have done several thousand miles.

I think with the new 750W units then there must have been some revisions as there's no mention of failures on these.

I have had both of these systems on my bike. The BBS02 is more powerful, but the TDSZ2 torque sensing is pretty darn sweet. It really is a tough call, but consider your style of riding. For steep climbs and technical courses, then BBS02 using throttle is hard to beat. Bike paths and long level runs? then get the TDSZ2. If you ride with others, the PAS on the BBS02 can make it very difficult to keep the same speed as your friends without resorting to the throttle, but the TDSZ2 would shine in this area, you can fine tune your speed with your effort. But if you ride alone, then the PAS on the BBS02 is not so bad, its more like a cruise control that picks a speed NEAR the speed you want. Let us know what you decide!