Whats really important when buying a base bike?

[bando_red]

I know that it needs to have room for the motor and that the frame should be fairly beefy, but does it matter If I buy an off brand or a name brand or what? It just seems like a waste to spend 400+ dollars on something you're gonna gut. Is it really gonna kill me if I buy a bike from walmart or a yard sale? as long as its structurally sound then itt should be fine, but I'm not super knowledgeable about bicycle quality tiers. I've never owned a buck that cost more than 150 dollars in my life.

 

[Fabian]

From my experience the most important aspects of a motorised bicycle are the brakes.
Others may disagree with me but disk brakes are the "only" method to be used, so the bike must have hard points to accept front and rear disk brakes or be fitted with front and rear disk brakes as standard equipment.
From there the front disk rotor needs to be upgraded to the largest currently available, being the Hayes V9 disk rotor and caliper adapter. The rear disk does not need to be larger than a 150mm, usually the standard size on mountain bikes, as hard braking requires no more than 50% mechanical advantage compared to the front, similar to a car braking system or a motor bike braking system with linked front and rear brakes.


Currently the most powerful ""mechanical"" braking combo is the the Hayes V9 (9 inch) disk rotor and BB7 caliper.
To allow caliper fitment on an I.S. post mount the V9 I.S. post mount adapter needs to be slightly modified.
The V9 rotor combined with a BB7 caliper and EBC Red brake pads front and rear will ensure adequate braking capacity.
Even so, there are times when such a combination is only barely adequate; my preference being a custom 12 inch disk rotor with dual BB7 calipers.
Heaven help you with only rim brakes, trying to stop from 30 miles an hour down a 15% gradient in the rain.


Moving on from brakes, the next question is: Single speed or multi-speed gears.
If using multi-speed gears with a SickBikeParts Shift Kit, the best option is an 8 speed cassette and 8 speed grip shift (twist shifter) mounted on the left hand side.
From my experience, the 9 speed cassette has sprocket spacing too tight for even the slightest error, leaving no room for mechanical misalignment as the adjacent larger sized sprocket virtually rubs on the chain.
It's inevitable at some point that there will be misalignment through chain induced pantograph inertia, and when this happens under power, the result is a ghost shift to the next gear, following by a shift back to the preselected gear, usually tearing out a chain side plate if lucky or bending the sprocket or both.

8 speed systems are much more tolerant of misalignment, yet can still be fitted with a 36 tooth sprocket from a 29'er cassette whilst retaining the 11 tooth sprocket, when disassembling and reassembling a "jail break" sprocket stack.

At the end of the day you're going to have to spend around a minimum 0f $400 to $500 dollars.
From there you'll have to spend money on SRAM X7 Gripshift, and SRAM X7 or X9 rear derailleur as the SRAM Grip Shift allows more rotation between the rotary index mechanism than Shimano, making it easier to feel your way through the gears.
In my experience, trigger shift is a waste of time, considering i've tried many permutations of the gear shift theme.


If you send me a PM i can give a web link, showing the simple modification required to allow fitment of the Hayes V9 disk rotor and BB7 caliper to an I.S. post mount.
.
.
.

 

[Fabian]

A round seat tube and down tube are also required, making life much easier when it comes to attaching engine to frame.

A set of quality rear view mirrors is also essential. I can send a web link for such a set of mirrors in a return PM

 

[motorbikemike45]

I've built 4 gas engined bikes and 3 electric powered bikes. All were built using an inexpensive big box store bike as a base. All cost $200.00 or less, but all needed upgrades in wheels, tires, and brakes. One needed a bearing upgrade right out of the box. That particular bike was such a piece of garbage that I eventually gave up trying to make it work well and scrapped the frame, moving all the good components to a different, new bike. The cost of a new bike is an indication of quality, at least to some extent. You should pick the base bike with care so you avoid the mistake I made. Stay away from any new bike under about $150.00.

As Fabian said, disc brakes are by far the best, but I don't consider them an absolute necessity. If you live in an area with lots of hills, then go with, at the minimum, a disc brake on the front wheel. I would also upgrade the front disc brake to a BB5 caliper, or better. I think quality linear pull rim brakes are acceptable in mostly flat country. A friend of mine blew 2 tires on a long, fairly steep downhill, with a bad, loss of control crash due to the blowouts. The blowouts were caused when the tires/inner tubes melted on the rim due to the high heat generated by trying to control speed on the downhill. It can happen, but not with discs. When I am using rim brakes, I upgrade the brake pads with better quality pads from Rav-X or Quietstop or the like. If you go with an older used bike, be aware, the 1970s bikes with side pull or center pull brakes have such short brake arms there is little mechanical advantage and the brakes won't stop you in a short distance! Replace them with new brakes!! Some of those bikes also had steel wheels, chrome plated or not. Replace all steel wheels with alloy wheels if you use rim brakes. Steel rim brakes don't work worth a darn when wet! Also carefully check any used, steel frame bike for rust. Once rust has started it is fairly difficult to stop completely.

With any inexpensive or used bike you should take the bike completely apart, right down to the frame. You will be amazed that some bolts and screws are WAAAAAY overtightened, and some are very loose. That lack of care when cheap bikes are assembled is nearly criminal, one reason they are so cheap, and can kill you at speed. Regrease all the bearings with high quality grease, like good auto wheel bearing grease, and locktite all the fasteners as you put it back together.

 

[abikerider]

I would add that a cruiser frame with a curved downtube willfit a four stroke engine much more easily.

 

[Richard H.]

Is it really gonna kill me if I buy a bike from walmart or a yard sale?

Not necessarily the same thing, by a long shot. Depends on the yard sale bike, I've picked up some great finds at yard sales but NONE of them were walmart bikes.

 

[abikerider]

The 7 speed Schwinn steel cruisers from Walmart are decent bikes to motorize. The frame is strong and they have v-brakes. I have built two Schwinn Clairmonts and they turned out really well. You do need to check and adjust all the bearings. The wheel bearings in particular are really tight from the factory. Also the Clairmont comes with painted rims which I found will eat brake pads and degrade the braking performance. I recommend removing the paint on the braking surface using a polycarbide abrasive wheel like this http://www.harborfreight.com/4-inch-polycarbide-abrasive-wheel-brush-94015.html and some sandpaper. Also the fender struts and mounting brackets need to be replaced with thicker metal or removed as they will eventually fail and cause a crash.

If later you feel like you need a disk brake up front you can buy an RST 1" steer tube suspension fork with disk brake tabs for under $100 and an Avid BB7 cable operated brake for around $60. I live in the relatively flat Sacramento, CA and I feel the v-brakes are perfectly adequate here.