lukeforster2002

I have a Voodoo Bantu 2016 model, and the bottom bracket has began to wobble quite severely. Both cranks move with the wobble which makes me think it is a problem with the bearings. I have attached images of the cranks.

Is this a job I can do myself with limited tools or will I have to take this to a bike shop? It has the internal threads inside the crank so I am assuming its a job I wont be able to do. Can anyone give me any advice?

13ollocks

You're going to need a few tools - some specialized. Unless you were planning on getting into regular bike maintenance (and it can be a fun part of the hobby), I wouldn't bother - take it to the shop and give them the business.

Iride01 

The BB is inexpensive. Likely the local bike shop will also be fairly inexpensive to change it out.

If you want to change it, then you have to determine what type BB it is and what exact tools are needed to remove it and the crank arms. Those will cost you more than having the bike shop change it several times. Plus the tools you get might only be used for that bike. Any other bike you buy might have a different BB requiring different tools.

QR Cycles says this Voodoo Bantu has a FSA BB-7420, 73x122.5mm, square taper.
https://qrcycles.com/products/voodoo-bantu-27-5

But I can't guarantee you have the same BB. Sometimes the BB type changes between years. And for bike models that come with different tier levels of components, then sometimes even the same year model will have different BB's and BB shell. You'll have to look. And if you aren't the original owner there is no assurance that they didn't put in a different crank that requires a different BB than what originally came with the bike.

That is a cartridge type BB. So most would just get a new BB for about $18.00 USD if they are going to DIY it. Here is the instructions .pdf from FSA about changing that type BB. ISIS/JIS/PowerDrive Installation Instructions .pdf (0.47 MB )

Park Tools website is full of useful info on various bike DIY topics.... https://www.parktool.com/en-us/blog/...&area%5B%5D=47

grumpus

You'll need a crank puller and a bottom bracket tool, available cheaply online, then all you need is a ratchet or adjustable spanner to turn the tools. Bottom brackets are also available online, note that they come in different lengths, you'll have to measure the one you have, or read the label once it's removed. The links above are just the first/cheapest I found on eBay, you can spend more for better quality, but even the most basic bike stuff mostly seems to be of adequate quality. Crank removal . Bearing replacement .

veganbikes

So first I would take off the cranks and then reinstall properly and see if the problem is gone. I would also inspect the crank arms and make sure nothing is damaged or the taper is gone as that could be the problem and then you need new cranks not necessarily a BB. If the cranks are removed and the axle has the wobble then it would be a new BB but I would go through everything first.

Of course you have already checked and made sure your pedals are not loose in any way. I had a pedal once that needed a rebuild and the bearing was damaged so it wobbled but a rebuild solved that. However you may just need better pedals that are rebuildable if you don't have that.

Kai Winters

It's not terribly hard to replace the BB. But if there is a problem removing the old BB it can be a real pain even for a shop mechanic.
You need the correct tools and BB...the axle lengths available make it a bit of a pain to get the right one...measure twice before you buy and make sure you can return it if you get the wrong size...or get the tools, remove the BB, take it to the local shop...let them measure it and sell you the right BB then take it home and install it yourself saving maybe $30 labor...shmaybe...that's what we charge.
If you like working on your bikes and like having tools you may use only once every year or so go for it. Watch videos on the procedure...it's not very hard all in all.
If you don't want to spend my $50 bucks on tools and another $50 more or less on a new BB then take it to a shop and let them do it. I will cost maybe $75 plus parts and labor depending on the price of the BB...not too expensive for your bike.
The biggest problem imo is your inexperience in removing/installing a BB/Crankset...how much force may be required can be a bit intimidating to the inexperienced...you'd be surprised how much force may be required to remove the BB. I've had to use our 3 foot pipe on the wrench to get enough leverage to break the seize on some BB's I've replaced...if you're not used to it it can be a bit scary lol. For the average wrench monkey...meh, just another day.
Good luck and keep us informed.

Duragrouch

Hence, my hesitancy to use Loctite (anaerobic thread locking adhesive), even low-strength "blue". I DO use anti-seize on BB threads, it prevents seizing, and is less slippery than grease, it's not supposed to change the friction coefficient from clean, dry, no rust parts.

redshift1

I looked into this quite extensively a few years ago and while I agree that anti-seizes are less slippery in general than greases ( also bearing in mind that anti-seizes vary amongst themselves quite widely ), I believe they most certainly do significantly change the c of f's compared to dry threads. ( The threads should be clean and non-rusted in both cases ). Probably makes little difference in the case of a bicycle bottom bracket if specific torque values aren't called out, but in some applications, like perhaps engine cylinder head bolts, it really does matter.

Duragrouch

Agreed. I'm still freaked out about Torque To Yield (TTY) head bolts.

lukeforster2002

Thanks, Ill order the parts today and try and give it a go myself over the next week or so.

Duragrouch

You only need to buy the tools once. And now you have online videos. And if you do a LOT of riding, you'll be surprised how often you may need to replace a BB cartridge. If not buying Park tools (which seem to always be good), if buying on amazon, check buyer reviews on the tool (and parts as well), I've found that to be very helpful.

lukeforster2002

Thanks man appreciate it a lot. I cycle to work most days and have owned the bike for 6+ years now, and try and do as much maintenance myself as possible. I've just bought a tool set so i can strip the bottom bracket on amazon for about 15 quid. It seems as though the whole bottom bracket comes as one (not where i've seen on youtube where the bearings are separated by a metal pipe and theyr'e all individual parts, although I wont be sure until Ive took it all apart.

Will keep this thread updated i appreciate the help

Duragrouch

Glad to help. More knowledge:

What you have purchased is an "internal cartridge" bottom bracket, design been around many decades. It replaced "cup and cone" BBs which had loose or caged balls, solid axle (usually square taper ends), and bearing cups (outer races that threaded into the BB shell).
Advantages:
+ Huge labor savings for service; no need to remove and clean bearings, repack with grease, reassemble. The cartridge just screws in and you're done.
Disadvantages:
- Once the cartridge starts to "loosen up" from wear, there is no way to adjust it out. It'll still be a while until the BB fails, but the axle will be looser, which stretches the seals (letting in rain if applicable), accelerates wear on the bearings (because a loose bearing only loads 2 or 3 balls at a time, whereas a "snug" bearing loads about half, 180 degrees of the bearing balls under load), and makes the chainrings wiggle.
- Cost; More expensive in parts than cup and cone bearings which can be rebuilt for ten pence in grease, two quid for new bearing balls if needed. For this reason, cup and cone bearings still dominate low-cost bikes, and most especially bikes in the third world.

The other style BB bearings that you may have seen are "external", 2 parts, each a bearing that mounts between the BB shell end faces and the crank on each side.
Advantages:
+ Allows a larger diameter, hollow BB axle, which is stronger, stiffer, and lighter.
+ Like internal cartridge, quick to replace.
+ Because external, bearing balls are larger and/or more of them, making the bearings more durable.
+ Bearings are closer to each crank arm, reducing bending moment on axle and loads on bearings, making the bearings more durable.
+ Unlike internal cartridge, ***slack over time can be adjusted out, to back like new***, you just loosen the left crank arm, adjust preload, replace crankarm. Restoring the preload reduces load on individual bearing balls. This makes the bearings more durable. (Are you sensing a theme?)
+ Backwardly compatible! Can fit in BB shells whose design dates back 100 years.
Disadvantages:
- Requires replacement of the entire crankset for (one example) "Hollowtech II" style; This has hollow (pipe) BB axle permanently attached to the right crank arm, it slides through both bearings, the left arm attaches with a clamp around splines on the end, and there is a cap on the end to adjust bearing preload.
- Requires a special wrench for the outside splines on the bearings, which vary greatly, but the most common standard is "ISO External"; I bought a 4-way wrench that has that pattern, as well as 3 others, in case I need in future.

The good news is, Hollowtech II style is now available generically, so a whole double chainring crank with chainrings, and ISO-External bearings, cost me USD$65, cheaper than just the chainrings would cost. I ordered a 2nd one for spare parts, cheaper.

For any of the above, be careful:
- The cup or bearing on the left (non-drive-side) of the bike is RIGHT HAND THREAD (normal; righty-tighty, lefty-loosey).
- The cup or bearing on the right (drive-side) of the bike is LEFT HAND THREAD, left rotation (anti-clockwise) tightens, right rotation (clockwise) loosens.
This helps keep the bearings tight. This assumes you have a BSA*/English BB shell standard, the most common.

There are more rare BB designs (such as "Italian") where the right cup is right hand thread, and they have a habit of coming loose.

* Birmingham Small Arms (yes, that Birmingham, UK); Guns, bicycles, motorcycles, etc.

dedhed

https://www.parktool.com/en-us/blog/repair-help

​​​​​​https://www.youtube.com/@RJTheBikeGuy/videos

​​​​​​https://www.youtube.com/@parktool/videos

​​​​​​https://www.sheldonbrown.com/

lukeforster2002

UPDATE: Managed to change the bottom bracket no bother, but by god the bracket was screwed do damn tight had to get a 3ft pipe to get the leverage to break it loose. Thankyou everyone for the help - pretty straight forward job really - glad i didnt pay a shop to do it.

Next, how viable is it to change my crankset from a 3 speed to a single speed? Ive read online its pretty pointless but I literally never use the top or bottom ratio - always in the middle.
Cheers guys

grumpus

Satisfying, isn't it? An impact driver can be very useful for that particular job - did you grease the new one?Ah, you should have asked that first, as you'd really need a shorter bottom bracket. OTOH if you can find a narrow-wide chainring that fits your current crank, and fit it where the middle ring is now, then the chainline (distance from the bike's centre plane) will be good. You could just remove the inner and outer rings, shifter and mech, as long as the chain doesn't need the mech to keep it on. Then the next job will be a 10/11/12 speed cassette/chain/shifter. :-)

dedhed

Fast simple easy way - Don't shift the front

lukeforster2002

My bad! Yes i greased the new bracket. It seems to not want to go into the top ring anymore - to be honest I believe that the bracket i have been supplied with may be slightly different dimensions, hense it is hesitant to shift to the top gear - although Im sure i will be able to adjust it which ill give a go tomorrow when im back home.

Yes i could just not shift it - great option . Theres just something about a single front speed that looks clean and premium to me - it wasnt actually a functional change I would like to make. Maybe its best off to upgrade the bike if Im desperate because this voodoo bantu is pretty heavy and old (albeit its a great bike and ive looked after it for a long time now). Was looking at a lapierre hardtail - pick one up second hand for a couple hundred quid We will see...

As I say, i appreciate all the help!

grumpus

Is the drive side cup fully screwed in? Have you checked the drive side crank bolt is really proper tight? Hopefully the limit screw has enough movement to compensate for a slightly longer axle, although chainline may be sub-optimal.

Duragrouch

As others suggested, you could just stay on the middle ring. If you wanted a "cleaner look", and yes, bike ownership is emotional so I understand about you wanting a certain look, you could very easily remove the largest and smallest rings, leaving just the center ring; The only issue is the chainring fixing bolts, on the back side, the bolt will screw past the 2-notch nut, which is a problem only in that my nut wrench for that would then be blocked by the bolt protrusion, and if the same for you, you would need either shorter fixing bolts, or a washer under each bolt equal in thickness to the outer chainring that you removed, and both are commonly available.

You are in a period of knowledge expansion, so I would recommend minimal changes in cost until you have a better idea of what you may want.

Please be aware, on my original 1X folding bike, I would occasionally drop a chain, and it would be a mess putting it back on in the field, which is why I carried disposable gloves. Your bike may not drop the chain, because you have longer chainstays and the middle ring should be close to the center of the cassette. But when I went 2X crank on my folder, I still occasionally drop a chain, but then I shift the front derailleur and it pops right back on, that is one of the benefits of a front derailleur.

Have fun biking, and enjoying learning new knowledge and doing your own bike service, which to me, I find very satisfying, plus I don't need to drop off or pick up my bike at the bike shop (not within walking distance, and I hate using my car, I bike everywhere I can). Plus it saves me tons of money. I don't often praise amazon, but it saves me a ton of money on bike parts, especially for an older system like my 7 speed cassette with V-brakes.