[Fish777]

I've been doing some searching but have not found the definite answer I'm looking for so sorry for the familiar questions.

I've got some Profile 170mm cranks and Profile euro BB with 6" spindle(48spline) to replace the crappy stock Hussefelts and ISIS BB.

Somewhere, I thought on Profiles site, I found that for a 73mm BB you should go with a 6" spindle though I can't find it now.

Anyways, I'm just wanting to ask those of you own a dirt jump MTB with 73mm BB shell who ALSO have converted to or built your bike with a BMX crankset, what spindle length are you using and how many spacers, if any, did you have to use?

Did you have any install issues or have tips to make install easier?

Additionally, I'll be using a Tree lite splined sprocket in 28t if that helps any and of course this is a SS setup.

 

[Boxxer]

6 inch is good. Install your drive crank and sprocket and set up your chain line. You get a feel for how many spacers after youve done it a few times, but I can tell you you wont need many.

Go ahead and install your BB. Even with the 'correct' tube spacer you might find you have to add shims to get it to sit with the right preload while having the non drive side bb cup threaded all the way in....

Once youve got the BB installed put the sprocket on the drive crank(loosely) and then thread the drive crank onto the spindle. Id put one of the 5mm spacers between the sprocket and the BB. Get good spindle overlap... more than half is accepted as correct.

If your chainline looks good then go ahead and install the non drive crank. Here youll need some spacers for sure... usually two of the thicker ones. The nice thing about BMX cranks is you can set up both your chainline and crank spacing so its perfect. I like to take a caliper and measure from the drive crank to the center of the seat or downtube and set up the non drive with the same spacing. Again youll get a feel for whats close to perfect with some experience.

Youll end up taking the non drive crank on and off a few times if you dont guess correctly the first time. When you do this, leave the drive crank on and just knock the non drive side off....

All that being said, make sure to grease the splines and if you dont have atleast 1/2 spindle to crank overlap then youll need a longer spindle. The 6 inch works for most MTBs with 73 mm shells. Also make sure the back of your crank pedal boss isnt too close to your drive side chainstay or it could rub(depending on the frame)... grinding down the back side of the boss a few MMs is ok.

Its easier to actually do all this than it is to type it out.

 

[Fish777]

Excellent! Great detailed reply and I appreciate it!!