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    New Trek 820 Build

    Hi Everyone, I have a 1999 Trek 820 Aluminum that I love. My advanced age forces me to add a motor to the bike to help in riding. I contemplated a new ebike, but seems that in my price range (~$1k to $1.5k) there isn't anything decent.

    The frame of my Trek is 18 inches with 26x1.95 wheels, and rim brakes. I would like to get a rear hub motor (48v 750w) kit, but am totally confused and frustrated as to which one to buy. It seems that Ebikeling, Voilamart and the no names on Amazon have a lot issues. Bafang only offers a 500w rear hub kit for rim brakes, and the ones available from Grin are way beyond my budget. I have no problem in building the bike from different sources, but thought a kit might be the way to go.

    Any suggestions as to which to buy including a reasonable sized battery would be greatly appreciated!


    A quick look at images of the bike it looks like a pretty typical old school bike so should not be a big deal to convert. Rim brakes can be an area of concern but possibly acceptable for certain types of e biking.

    Sounds like you have done some research already and I think I agree with what you mentioned above. Grin does seem to be THE name when it comes to quality hub motors. Depending on your answers to below questions 500w may not be a problem. One of my loaner bikes has a 350w front hub motor and I thought it was going to be useless compared to my fleet of 1500w mid drives but it still really helps and was fairly low cost and about as easy to install as it gets.

    What sort of weight range are you in these days and are you going to be carrying any significant cargo? Or just usual bike stuff like some water and a small pack?

    How fast would you like to be able to go? Are you kinda thinking still more or less regular bike speeds just with less effort or would you like a little more?

    At this point you are planning on doing some pedaling not just throttle?

    How far are you thinking you will be going between charges?

    Florida is pretty flat so I don't expect there will be a lot of hill climbing but maybe you live and ride where I think its Retrorocket lives where slightly excessive performance is required just for safety? If that is the case then I think the rim brakes are out.


      Thanks for responding 73Eldo. I am about 210lbs, do not plan on carrying any additional weight on the bike, other than maybe a water bottle and a chain lock.

      Yes, the terrain is flat, with no major hills in our area (Extreme NE Florida right on the Georgia border).

      Because it is necessary to ride with auto traffic (albeit light traffic), I would like to get up to at least 20-30 mph, and peddle most of the time along with electric assist when I'm tired.

      I'd like the range to be 20-30 miles per charge.

      Thanks for your help!


        For that sort of weight and speed I think you are looking in the 1000w range so perhaps the BBSHD mid drive to take advantage of the gearing? I don't know a lot about how to select hub motors in that class so I would be reading up on Grin's website and seriously considering buying from them. An issue with hub motors is you kinda have to pick the 'gear' when you buy them. You can select one that is fast and powerful off the line but lower top speed or one that needs you to help pedal off the line but has a good top speed or something in the middle that kinda sucks at everything. Mid drive you get to use your gears so you can sort of have it all so to speak. Hub motors do work and have their place but I don't know that its for someone that wants speed and power. I think they are more for the riders that are still going more or less bicycle speeds and were never into shifting gears. I know there are stupid powerful hub motors but I don't think they come cheap.

        Also for that weight and speed I would say the rim brakes are a no go. That bike was probably designed for a 150-175 pound rider to safely stop from more like 15 mph. You got a bit more weight and possibly twice the speed so any safety margins that were there are long gone. I think I would be looking for a disc brake bike to convert or go back to looking at complete bikes. $1500 budget including buying a bike is going to be pretty difficult with your requirements. $1500 will get you a BBSHD kit with a decent battery and you should be able to find a decent bike for $500 to convert. I think there may also be a few $2000 pre built bikes that may work for you.

        For the kind of power you need I would be thinking 2 miles per amp hour so at least 15ah pack which isn't typically an option in this class (48 or 52v). The small ones tend to be in the 10-14 and the bigger ones like 17-22. Its really going to depend on how much of that 20-30 mph you end up doing. If you are for the most part under 20 mph and pedaling 30 miles out of a 14ah should not be a problem. The larger packs are larger and heavier and more expensive so its nice to not have to deal with all that if you really don't need that much range but it is nice to not have that as a worry. At that point your range limit is still AH except it it then stands for ass hours as in how may hours your ass can stand being on a bike seat. For many of us older and heavier folks that really kicks in after about that 14ah size packs. 40 miles is generally going to be in the 4 hour range of ride time which can be a lot of seat time. With my 14 ah pack its the back that runs out. With my 21 its my ass.


          found the specs for your bike

          I have to agree with 73Eldo Rim brakes and a BHSD motor not a good idea . Perhaps You could look around for a good used bike with disk brakes to convert over or if Your budget permits buy a New bike . I have seen decent bikes on Walmart in the 300 dollar range that would be a good upgrade as You go
 WjWy4USuTxyNR4x2iEwAB1ceUkAS1hzpw2DOU40&veh=aff&wm lspartner=imp_2241907&clickid=WjWy4USuTxyNR4x2iEwA B1ceUkAS1hzpw2DOU40&sharedid=&affiliates_ad_id=565 706&campaign_id=9383

          Review of the bike
          The Schwinn Junction 27.5-inch Mens Hybrid Bike from Walmart is one of the few big box commuter bikes that are worthy of being considered for a daily commute...

          That's How I got started , Like You I am a senior up in my 60s . I started with a Gt aggressor pro from Dicks sporting Goods and over a few years built My bike up

          As far as motors defiantly go with a bafang mid drive at least a 750w , , preferably a bafang 1000w drive . And stay away from amazon sellers , I suggest these guys
          BAFANG BBS MOTORS BBSO2 750W MOTOR KIT BBSHD 1000W MOTOR KIT POWER.DURABILITY.FUN.   Turn your bike into a beast. You've discovered the powerhouse family of mid-drive motors and they deliver all of that power quietly. These motors run more silent than more expensive less powerful mid-drive motors. Between the Bafang BB

          The BHSD puts out 160NM of torque VS 120Nm of torque and I suggest a 52v 20ah battery with the BHSD with a 42 tooth chain ring to get to Your 20-30 mph

          EDIT The GT Aggressor pro is on sale marked down from $799 to $299
          a steal of a deal !
          Last edited by brothergc; 05-22-2023, 03:07 AM.


            73ELDO makes a good point. I've converted two 1990's era Trek MTN bikes using Bafang BBSHD and BBS02 Mid Drives. The thing on these bikes that concerns me the most is the breaking requirements with the combination of rider weight, battery/motor weight and higher speeds. IF you can purchase a good donor bike with disk brakes, you'd be better off converting it, or just purchase a new eBike. Both of my bikes will not upgrade because the frame will not allow for rims with disk brakes, nor have mounts on the frame for calipers. On the other hand, I must say I am not disappointed with the performance of the Bafang mid drive system on our Trek bikes. If you are driving the bikes for distance and not speed, then you can program the controller to suit your needs.