8-FUN BBS01 Crank kit on Boardman MTB PRO 29er

[Dog George]

Happy new year to all. I'm thinking of buying a Boardman MTB & fitting a Crank drive kit so i can keep the Sram 11 gear cassette & Mavic wheels. But i'm not sure about the Bottom Bracket scenario, the bike i'm looking to purchase has a Sram PF30 bottom bracket others have got Square Taper? The BBS01 Websites i've been looking at state the BB has to be standard 68-73mm & not have long shells?? Can someone please help with my dilema, I don't want to buy a certain model MTB then find the Crank drive motor won't fit the bottom bracket. Please do not suggest asking Halfords i've already tried that.

 

[anotherkiwi]

You remove the BB so the type doesn't matter except for eccentric which doesn't work in most cases. The BB specs should be on the tech sheet for the bike you are buying. Long shell is found on fat bikes or other and there are even adapter kits for those.

With an 11 speed you want to mount a chainring on the front that maintains a better line than the one supplied with the motor.

 

[Deleted member 4366]

It won't fit without adaptors. You need PF30 to BSA adaptors, but the problem is that they can rotate in the BB, which means that the motor anti-rotation crimp thing will be ineffective, so you need to fabricate and fit a tie bar somewhere on the motor to stop it rotating around the BB.

http://www.wiggle.co.uk/sram-pressfit-30-to-bsa-adapter/

Here you can see my torque arm. We made a replacement part for the standard one out of aluminium. The only place it could be tied to was the suspension pivot because the frame is carbon fibre. You can put a strap around the seat tube or downtube and rub a tie bar from one of the two fixing holes to it.

 

[brightonebikes]

Unless you're dead set on that particular Boardman, I think I'd suggest to do a little more research and find something similar but with bsa 68-73 BB.
It'll just make things simpler and far more straight forward.
It seems you have a good budget for the bike (think those Boardmans are about £800?), so plenty of choice.
Another thing to look out for is how wide or proud the rear stays are and how close behind the bb that they start to widen. In order to allow for larger rear tyres to be fitted and still have mud clearance, some of the more recent hardtails' rear stays protrude too far out to allow the motor to slide all the way through the bb shell. Hope that makes sense!
Also, don't be put off by 10 speed trans. rather than 11. Part of me prefers 10 or perhaps even less on an e-bike providing the spread is sufficient. Sram's new eMTB specific trans., EX1 is 11 tooth to 48 tooth across just 8 sprockets.
Hope that helps

Sent from here to there with computer wizardry.

 

[anotherkiwi]

Also, don't be put off by 10 speed trans. rather than 11. Part of me prefers 10 or perhaps even less on an e-bike providing the spread is sufficient. Sram's new eMTB specific trans., EX1 is 11 tooth to 48 tooth across just 8 sprockets.

At the bargain price of only 56.25 € per sprocket too!

I agree on the number of gears - 8 speed being the ideal cassette for mid drives because you can get an 11-32 for about 12 €. Wider chain, better chainline...

If you need more gears you can always mount a double chainring on the front as I have done with my GSM.

 

[Deleted member 4366]

At the bargain price of only 56.25 € per sprocket too!

I agree on the number of gears - 8 speed being the ideal cassette for mid drives because you can get an 11-32 for about 12 €. Wider chain, better chainline...

If you need more gears you can always mount a double chainring on the front as I have done with my GSM.

I have seen a double chainwheel on a BBSxx, but I don't think it's easy.

 

[anotherkiwi]

I don't have a front derailleur which makes things a lot easier, I haven't found one that can reach that far yet (in my price range). I have the precialps 104 BCD spider for the BBS01 which is compatible with my GSM and 42 and 32 tooth chainrings. The chainline is actually quite OK when compared to the stock chainring.

In Navarra (and in Spain) there is no restriction on the % a road can be. Here on this side they have limits which means you rarely find sections over 15%. So I have the 32 just in case I run into a hill I can't climb with the 42 when over the border.

 

[chris_n]

I don't have a front derailleur which makes things a lot easier, I haven't found one that can reach that far yet (in my price range). I have the precialps 104 BCD spider for the BBS01 which is compatible with my GSM and 42 and 32 tooth chainrings. The chainline is actually quite OK when compared to the stock chainring.

In Navarra (and in Spain) there is no restriction on the % a road can be. Here on this side they have limits which means you rarely find sections over 15%. So I have the 32 just in case I run into a hill I can't climb with the 42 when over the border.

If you use one of these with a direct mount front mech you should be able to get the reach that you want.
http://problemsolversbike.com/products/direct_mount_front_derailleur_adapter/

 

[anotherkiwi]

Oh thanks! Yes one for a 100 mm BB might do the trick.

Cheers!

 

[Yokel]

It won't fit without adaptors. You need PF30 to BSA adaptors, but the problem is that they can rotate in the BB, which means that the motor anti-rotation crimp thing will be ineffective, so you need to fabricate and fit a tie bar somewhere on the motor to stop it rotating around the BB.

http://www.wiggle.co.uk/sram-pressfit-30-to-bsa-adapter/

Here you can see my torque arm. We made a replacement part for the standard one out of aluminium. The only place it could be tied to was the suspension pivot because the frame is carbon fibre. You can put a strap around the seat tube or downtube and rub a tie bar from one of the two fixing holes to it.

That torque arm mod has given me an idea which will solve a similar arrangement. I am trying to figure out a further mod which would enable the motor to swivel round and ride higher off the ground. Water got in through the outer casing gasket and into the motor compartment when my BBS01 got fully immmersed for half a mile or so in flood water a year ago. The instructions do say not to immerse, and not for MTB use, but the replacement has held up well since then, lots of fun, and I've made up the original machine by mixing parts from a friend who had wrecked the gearing side of his machine somehow.