cwr2427

Have an old Mongoose Brawler that I want to fix up for the kids. Didn’t want to post on the BMX forum as I’m not really wanting to keep it as a pure BMX right now.

What should I get to replace the crankset (part between the pedals?) as it’s grinding some. Also, what is a good budget brake system to add? I don’t really want front brakes, so possible rear/hand or coaster brakes.

icemilkcoffee 

The One-Piece-Crank probably just needs the bearing greased and adjusted. Start reading here:
https://www.sheldonbrown.com/opc.html

If your financial situation allows, I would start with a higher quality bike, like the Specialized Hot Rock with aluminum frame and coaster brake, instead of trying to upgrade a heavy steel Walmart bike.

50PlusCycling

I’d stick with the Brawler. A new bike is nice, but your kids may not use it enough to make it worth the expense. You can get a good, dual pivot brake from Amazon for cheap, installation is not rocket science, and it will stop the bike. If your kids are going to ride down hills, you would be better off with a front brake as well. One of my more memorable rides as a kid was flying down a steep hill on an ancient Schwinn. A broken chain meant no rear brake, and the bike didn’t have a front brake. I did an Eval Knievel off the cliff at the bottom of the hill, which impressed the hell out of my friends, but which earned me a ride in an ambulance, and a cast on my arm.

cwr2427

Thanks for the help. Fortunately, I found out the bottom crank is fine... it was the rear assembly that was the problem area causing friction. The area and bearings are shot and needs to be replaced. What's the best course of action? I'm having a hard time finding an exact replacement axle/bearing/hub assembly. It has a sprocket with 9 teeth.

veganbikes

If it is the rear hub you can potentially rebuild it with new bearings and grease or you can just buy a new bike for $69 at wally-mart or get the Hotrock and get a quality bike without the issues.

soyabean

How about curb finds on garbage days?

Folks are finding out that they can't even sell their entire collection of BSOs for more than $20 because of post-covid demand drop, compounded by winter.

Kids' bikes are even worse as free ads linger around for weeks with bottom feeders asking if they can get it delivered. Just easier to toss them out from the start.

cwr2427

That’s a nice stable of bikes you have there!

I was able to buy a bearing from my local bike store, and all is running smoothly now and my son’s back on the road. I appreciate the help. Only issue is the protective housing that keeps third out of where the bearing sits shredded off at some point so I couldn’t put that back on.

Up next are brakes, a paint job, chain, seat and grips.

Any advice on conversion kits for disc brakes? I found a set of $30 disc brakes on Amazon as mentioned above by another poster, but we need to incorporate a conversion kit I imagine.

I’m looking forward to fixing up this project bike. I’d post a picture, but I need to make a few more posts before the system lets me graduate from newb status (although that will definitely take more than just 10 posts at my experience level).

Iride01 

Be certain that you really want to upgrade the bike. I did that once to a old and worthless bike that only had sentimental value, but the only thing it did was give me more experience. The bike itself for the most part wasn't any better riding. It just had some novelty of having more gears that when original.

Putting disc brakes on a bike that wasn't made for them will entail quite a bit more cost and changing of the old bike than just buying the brake disc, calipers and brake lever. You'll likely need a new wheel hub to hold the brake disc. And the dropouts will need to be widened. Mounting points on the stay and/or fork blades will have to be figured out and all sorts of other things.

Don't let sentimentality about the bike cloud your judgement on whether it will be monetarily worth more. It won't. I'd just recommend doing what it takes to keep the bike running as is. And putting up with things that aren't perfect. Save the money for a better bike, or a better bike frame that you can DIY into the bike with components the bike was made for.

I wound up getting rid of my old bike I'd become sentimental about. There was no inexpensive or expensive way to make it a better bike than it already was.

Your future mechanical questions should go in to this sub-forum....Bicycle Mechanics

Welcome to BF!

13ollocks

If the rear hub is shot, it may not be cost-effective to buy parts, assuming you can even find them - just get another bike. If your kids are anything like mine, they treated their bikes like crap - left them out on the street in the rain etc. I quickly learned that buying them "good" bikes was wasted $, so I dumpster-dived or thrift-stored as needed, rehabbed them for use, and then gave them away or trashed them when the kids outgrew them.

Arrowana

On a bike like this, a disc conversion would be close to impossible. Disc brake adapters are either flimsy garbage, incompatible with a 20" BMX bike, or usually both. Disc brakes require hubs that are disc brake compatible, which would mean you would have to get an entirely new set of wheels. The new wheels would have a wider rear hub, requiring you to cold set the rear triangle to fit them, which might not go well with a 20" BMX bike. The new wheels almost certainly would not accept a 9t cog and driver, which would force you to get a new chain ring and chain unless you want absurdly low gearing. And even if you did all that, chances are pretty high that the seatstay would not have enough clearance to fit a disc rotor, so it wouldn't work anyways.

If you just want the brakes to work better, there are options. The brake pads that come on a Wal-Mart bike tend to be pretty crappy, swapping them out for something name-brand should give a noticeable improvement. Since you don't care about it being a bike for BMX, replacing the cables and housing would let you ditch the gyro for the rear brake, and if you can swap where the barrel adjuster and the cable pinch bolt are on the front brake, you can route the cable from the lever straight to the front brake instead of through the fork, which would greatly reduce the amount of resistance in the cables and housing, making it require less force to use the brakes. If the brake levers have a plastic body or lever, swapping them for something made of real metal will get some improvement, and greatly reduces the chance of them snapping in two. Brake levers come in short pull and long pull, your brakes need short pull levers. Tires play a large part in how well a bike stops, so higher quality rubber will help.