MTB old school conversion

[liefbike]

Hello to other pedelecs. I’m in Melbourne Victoria currently under COVID stage 4 evening curfew; so a good time for projects.

Rather than part with my 1998 GT XR-1000 (rare bike from the LTS era, retail then about US$4000), I am attempting to convert this 26 inch to a mid mount.

Current e-bike is a rear hub for road and trail only, so aim is to add mountain !

At present on steep (no pun intended) learning curve re mid mounts and due to lower cost, have ordered Bafang BBS02 48v 750w kit plus matching 48v battery.

Hoping Schwalbe Marathon Plus Tour 2.0 will cope and yet to come, is to figure out the best way to deal with groupset and lots of other setup matters, including chain line challenge.

 

[vfr400]

How wide is the front bottom swinging arm pivot? It looks wider than the BB in photos.

 

[peter.c]

Is that an i drive version, have looked hard at a mid drive conversion for that one, not sure if it will fit so did not buy one please post a picture of the bb and suspension arm location

 

[liefbike]

It’s not idrive, the vanilla air shock is trunion mounted just behind the seat post, so has a clear triangle for the battery.

 

[peter.c]

It was not the battery in the that worried me its the width and dia of the bb , now found a pic of the frame can see a octa link bb and if still v brakes stopping could be

 

[liefbike]

Standard 68 BB and this particular frame has options for v / cantilever as you say, and also discs. The currently fitted Avid Juicy 5 hydraulic brakes should manage; but given the 750 w, some have fitted sensors to both brake and shifters.

 

[vfr400]

Standard 68 BB and this particular frame has options for v / cantilever as you say, and also discs. The currently fitted Avid Juicy 5 hydraulic brakes should manage; but given the 750 w, some have fitted sensors to both brake and shifters.

You're not understanding. It's the width of the swinging arm right next to the BB that's concerning us. If it's wider than 68mm, you'll have a problem to solve. It looks like it is in the photo, but the angle isn't the best to see.

 

[liefbike]

How wide is the front bottom swinging arm pivot? It looks wider than the BB in photos.

Good question, I’

You're not understanding. It's the width of the swinging arm right next to the BB that's concerning us. If it's wider than 68mm, you'll have a problem to solve. It looks like it is in the photo, but the angle isn't the best to see.

yes you are right, it is wider, so I can only hope that I can find a way to ensure there is at least some gap using the BBS02.

 

[peter.c]

Thats great should be ok enjoy your conversion

 

[liefbike]

Thats great should be ok enjoy your conversion

Thanks Peter
Maybe some sort of bottom bracket extension will be needed, then hopefully it will be a goer, only time will tell.

 

[vfr400]

Thanks Peter
Maybe some sort of bottom bracket extension will be needed, then hopefully it will be a goer, only time will tell.

You can only do that if you have the BBS** with the longer shaft option, otherwise you're limited to about 5mm max from the bare edge of the BB shell. If you pull the motor too far to the right, you can't get the nut on the other side.

As I said, you must measure the width. Any more than 78mm is trouble. Anything less should be OK.

 

[Fat Rat]

Hi
Welcome to the site
And enjoy your conversion

 

[liefbike]

You can only do that if you have the BBS** with the longer shaft option, otherwise you're limited to about 5mm max from the bare edge of the BB shell. If you pull the motor too far to the right, you can't get the nut on the other side.

As I said, you must measure the width. Any more than 78mm is trouble. Anything less should be OK.

You can only do that if you have the BBS** with the longer shaft option, otherwise you're limited to about 5mm max from the bare edge of the BB shell. If you pull the motor too far to the right, you can't get the nut on the other side.

As I said, you must measure the width. Any more than 78mm is trouble. Anything less should be OK.

It gradually widens further back, to about 100mm, however at that width it is beyond the reach of the current chainwheel.

Found this estimate on a thread looking at chainring diameter and without undertaking the math, viz tooth size and spacing etc.

28T = 116mm
32T = 132mm
34T = 141mm
36T = 149mm
38T = 157mm
44T = 182mm
48T = 199mm

Not sure what size the 44T one provided with a BBS02 will be, however perhaps there is the option of buying an aftermarket (recommended per weight saving) small chainring, in combination with a wide ranging cassette (eg 11 speed HGS has 11-51T available); OR a bolt on adaptor with a front derailleur / second larger chainring system in use. Ballpark cost for both is around A$250.

On the actual use of 'Lekkie' type chainrings and perhaps adaptors, said to improve chainline for Bafang mid drives, I was waiting to see what that actually looks like on the bike.

 

[vfr400]

It's the reduction gear housing that will ne the first thing to touch. The chainwheel is further out. The only thing you need to measure is the width at the front pivot over the BB. If it's more than 78mm, you'll need the longer shaft version of the motor.

 

[wheeliepete]

Judging from your photos, as long as your BB is 67mm you should be OK. As your BBS is on route to you, there's not alot to do but wait and see. When you see the dustbin lid chainwheel Bafang send you I hope you see the need for a 42T Bling Ring to match your very cool looking bike.

 

[vfr400]

Judging from your photos, as long as your BB is 67mm you should be OK. bike.

That's not right. He has a swinging arm pivot that he said is wider than the BB and is right next to it.

 

[liefbike]

It's the reduction gear housing that will ne the first thing to touch. The chainwheel is further out. The only thing you need to measure is the width at the front pivot over the BB. If it's more than 78mm, you'll need the longer shaft version of the motor.

Thanks for your assistance; width measured at the front pivot is just under 70 mm

 

[wheeliepete]

The pivot looks OK to me, slightly concerned about the width of the webing on the linkage if it's the same as this frame.

 

[liefbike]

The pivot looks OK to me, slightly concerned about the width of the webing on the linkage if it's the same as this frame.

View attachment 37584

Webbing looks the same and its being wider was my concern, subject to the diameter of the closest chain ring.

 

[liefbike]

Further to old school mid mount clearance issues. With supplied 44T chainring, it appears to line up with about the second or third smallest cog, out of the 9 on this cassette. Given the stock chainring is only about 1 cm away from the chainstay, the bigger offset of a Lekkie may be a problem.