Tangent inner-drive chainring replacement/BCD

Hi Folks,

I've been immensely enjoying my 6kW tangent kit on my bike. It's seen about 500miles of use.

The inner chainring is now very worn and needs replacement. It's aluminum, I'd like to replace with a steel/hardened steel for greater durability.

It is mated to a freewheel crank mech, through a custom spider that also carries the final drive chainring. The final chainring has a BCD or 104 which is fine and standard sizing. But the inner chainring is the one that seems to have a custom/unorthodox BCD of about 66.5mm. This makes it impossible to source standard bicycle components for replacement.

Can anyone point me in the right direction?

Got word from Dave that the chainring for the kit is this one here.

Link for reference.

http://sickbikeparts.com/chainring-freewheel-24-tooth/

So your 6kw tangent lasted only 500 miles and you're still immensely happy ? That sounds like a design fail to me or cost cutting, or maybe that's how they get such low weight using aluminium chainrings...?

I guess long life or reliabilty is not on their priorities

You would think even steel ones would not be happy at 6kw ! Maybe it's not designed to run at this power for long in reality...

500miles sorry to say is a miserable distance to achieve.

If you are wanting performance gains and increase durability and reliability you need to look aftermarket. The out of the box kit works well, but not when you pump 5KW through it.

I found a mob called AFT (google aft ebikes and the link will come up) and they offer a series of professional modifications to address quality and performance short falls in the off the shelf system.

As such, like you i originally blew my gears (in the engine) after approx 1000kms. Since then, i moved to AFT aftermarket parts and only recently did i blow my engine gears again...after 5500Kms. So for the extra $$ you par for the part, as you can see i got over 5 times longevity in parts. As such, this saved me down time, embarrassment and ultimately cash (given the original component would've failed 5 times over by now). This time around i am trying AFTs latest product made from Carbon Fiber. Expensive but it should translate to improved performance and reliability yet again. I am expecting these gears to last me between 7500-8000kms before needing to be changed again (and yes no drop in my power output - still sitting on 5kw peak).

Since the motor is down and out and in bits ive also decided to buy AFTs full ceramic greaseless motor bearings. Interesting times - stay tuned for further updates.

In summary default kits are cheap and nasty if you plan to pump up the power. AFT is a MUST if you tweak your kits beyond what is recommended. I hate pushing bikes

more to come

I wouldn't say that the failure of the chain ring was a failure of the system..... and to assume that would be naive imo....

There's a bit more to the story.

I can say with certainty that I have had several instances of branches making impact with the chain/tensioner and throwing the chain off the chainring. I also had an instance where under speed and throttle the same thing happened and wedged the chain between the chain rings and bent the original tensioner and the jockey wheel. These are due to my prefered riding... balls out, have fun first, heal later :lol:

Contributing to that would likely be that the chain ring is aluminum.

Apart from this the system is flawless and delivers insane power. The flaw in the system is the rider and the fact that it's on a bicycle.... if you can consider that a flaw.... I view the bike as high performance machine (according to my riding style) much like a race machine that gets torn down for rebuild and maint. Given what it delivers and what I ask of it, it needs regular and more frequent maintenance. And quite honestly, the maintenance interval is not much different than that advised for a DH bike anyways.... It's not a commuter. If it was none of these would be an issue.

There have been no other failures of the components as provided to me when I bought the kit.

But riding it as I do so far I have managed to
1) sheer the rear cog from the hub (riding style coupled with overly weak base bicycle component, surprised it lasted this long. Much stronger unit on order- was expected)
2) chain ring wear- expected given the use and unfortunate tree branch incidents.
3) rear derailleur failure (solely attributed to a separate incident where a branch go caught between the cage)

None of the following were related to weaknesses of the component or design. Most due to bad luck, some compounded by typical wear.

The thing rides as close to a MX bike as you can get despite being a bicycle.

I was also looking for the inner chainring as I know I will need it one day. Thanks!

Zulu seems to be confusing a different kit than the tangent. Daves kit is top notch. I can't expect anything else than to chew through bicycle components with 6kw of power on tap. That said I keep both spare chains on hand when I ride. No fun being caught out.

Probably should ask Dave himself for this but is there any maintenance needed on the freewheels, either the motor or crank? Embarrassed to say I may have got a tad bit of cleaning agent in the chainring freewheel and trying to decide if I should take it apart or if it will be okay. Dave makes an awesome kit, I still boggle how he manages to pay his own time making them. That said I am very glad for all the effort he has put into them. Up next is going 12s to 14s for a little extra kick. Can't be anymore right with this being as close to MX on a bicycle as the components allow.

Tangent supplied the chaining as part of this Kit right ? so either they are saving costs on crap parts or cheating to save weight with aluminum ? But I would call that a design fail and not be happy if any part of my mid drive kit lasted only 500 miles lol maybe it’s not designed for a long life or compromises durability to have such a low weight ?

It's a chain ring. The chain ring failed due to mishaps and high power being put through it at the same time. Call it what pleases you.

I have no reason to be worried about the rest of the system.