View Full Version : mmmBop BB?

31-Aug-2011, 05:25 PM
Just been helping a mate change some its from his Kona Dawg frame onto his shiny new mmmbop frame. Got to the BB and got rather confused. The Kona has a 68mm BB shell and the mmmbop a 73mm one.

Here begins confusion. I thought that 68mm you have 3 spacers, two drive one non drive, and 73mm you have one on the drive side. So I do that, bosh it all together and it doesn't quite work. The chainset is Truvativ FireX and the BB is a Truvativ GXP one. Am I going frickin mental or what? I tried telling him to buy a Shimano chainset and have done but he won't!

31-Aug-2011, 06:14 PM
Unrelared but wwhat wss wrong with the dawg why the change to hardtail?

31-Aug-2011, 06:58 PM
Nothing wrong with it. He's taking all the stuff off the dawg so he can use the mmmBop as, ahem, a commuter. He'll then be sticking some blingy stuff and a double and bash on the dawg. He will still be using the mmmBop off road because I won't let him just use it to get to work on as that would be a massive waste of a fantastic frame.

31-Aug-2011, 08:43 PM
What bit doesn't quite work Matt?
In theory it should, the spacers are 2.5mm, you've taken 2 out.

31-Aug-2011, 08:49 PM
If only I had taken two spacers out mate! When I took the BB off the Kona it only had one spacer on it! I had to measure the BB on the Kona to make sure I wasn't going mental.

If I leave that one spacer on the crank axle doesn't fully come through the other side off the BB. The way I look at it even If I removed that single 2.5mm spacer the still isn't enough axle to fully engage the crank arm onto the splines. I'm not in front of the bike at the minute so most of this is coming from memory.

31-Aug-2011, 08:52 PM
Not that I know the gxp system, but your spacer logic sounds right to me.
In what way doesn't it quite work?

Have you tried checking the sram webby for the fitting instructions to see how they suggest fitting it all together?

You've not managed to do it in the wetting ode our get the BB cups mixed up our something equally simple have you?

31-Aug-2011, 08:57 PM
If there was only one spacer on a 68 shell then it may be that the BB is for 68 only? Do you have a model number for it that could be referenced on the SRAM site?

31-Aug-2011, 08:58 PM
Nope the BB cups are on the right sides (Truvativ ones are idiot proof, have drive/non-drive written on them!). The cranks are all the way through but the splines on the non-drive side that the crank arm goes onto don't come through far enough.

I have got the original fitting instructions somewhere so I may have to dig them out.

Oh yeah btw, wetting ode?

31-Aug-2011, 09:00 PM
wetting ode = wrong order

Haven't you learnt Fred speak yet? :D

31-Aug-2011, 09:04 PM
Right found the instructions. Turns out that when on the Kona it should have had two spacers, one for each side. 73mm shell requires no spacers. I'll have another butchers at it tomorrow and see how I get on.

31-Aug-2011, 09:07 PM
Hobo, I didn't know you have Swype too?!

Spot on with the wetting ode

31-Aug-2011, 09:09 PM
Damn, I nearly suggested taking the other spacer out.

Hope it works!

01-Sep-2011, 08:52 PM
The Firex chainset isn't compatible with 73E standard, so you're correct it runs with no spacers.