Which BB for Profile Racing cranks?

[rentedmule]

After an oddly stressful deliberation over which cranks to run on my Dekerf Implant, I decided to go with the Profiles pictured. The plan is to clean/polish them and run 2 rings and a bash guard, not the setup shown (I copied the pictures from the seller's ad on Pinkbike).

Profile cranks by Rented Mule, on Flickr

Profile 2 by Rented Mule, on Flickr

I need help figuring out which bottom bracket I need. The frame has a standard old threaded BB mount, either 68 or 73 mm (I can't remember off the top of my head). Is it this one? https://www.profileracing.com/product/bsa30-outboard-bottom-bracket/

Gratuitous picture of the bike with old Truvativ Stylos I had on hand to get it moving.

20240822_081239 by Rented Mule, on Flickr

 

[NigelFinnighan]

I believe either the BSA or Euro BB would work- I'd contact Profile Racing and ask them what you'd need. They're helpful, I've contacted them before. Those look the same crank as a BMX with a double/triple spider on it. Reach out to them, I'm sure they'll get you set.

 

[d8mok]

Didn’t realise that Profile made mtb bottom brackets.

I’ve a pair on a spooky. Running bmx bb. Extremely heavy set up.

 

[wesmamyke]

Euro BB is just the BMX term for a standard english threaded BB. Just make sure you get the correct axle size. Probably 19mm, but they did 22mm oversized too. The axles come in a bunch of different lengths as well, I think it's generally the longest one they offer for a MTB.

 

[rentedmule]

Thanks for the info! I'll measure the spindle size when they arrive and confirm with Profile on the BB spec. Back in the day, some of the hardcore freeride guys at the shop I frequented ran Profiles with 2 rings and a bash, so I knew it was an option. Profile still sells the spider for that setup.

I know they're going to be heavy, I run a similar SINZ setup on my BMX. The rest of the Dekerf is fairly lightweight, so I think I'll be able to tolerate them. If I'm honest, I'll probably spend more time admiring it in my shop than I will riding it anyway

 

[Mace4130]

Thanks for the info! I'll measure the spindle size when they arrive and confirm with Profile on the BB spec. Back in the day, some of the hardcore freeride guys at the shop I frequented ran Profiles with 2 rings and a bash, so I knew it was an option. Profile still sells the spider for that setup.

I know they're going to be heavy, I run a similar SINZ setup on my BMX. The rest of the Dekerf is fairly lightweight, so I think I'll be able to tolerate them. If I'm honest, I'll probably spend more time admiring it in my shop than I will riding it anyway

You will need a Euro bottom bracket, and a Profile Mtb axle, the standard length bmx axle will be to short, you won’t have enough clearance between the crank arms and the stays.
Your franks look like the regular 19mm axle version, not the SS 22mm version.

 

[thetho]

I run them with the spider pictured. It will only fit on a 19mm width axle, so make sure to get one of these. As regards axle length, I'm pretty sure you would need the 6.875″ so as to have enough clearance for the arms, chainrings, a proper chainline and enough space for the crankarms to sit on the axle. As for the BB I have no experience with threaded ones as I run a BMX American press in. If I were you, I'd rather go for the Profile Euro Internal BB as it won't take away as much length from the axle as the Outboard BB and if you have too much you can just add spacers.

 

[rentedmule]

Thanks!

I did a bunch of measuring using an old Hope outboard BB and I came up with 6.2" from the outer edge of the crank arm splines. I figured a 6" axle would work with the extra 0.1" on either side necessary to cinch the crank arms snug. It looked like the arms would have plenty of chainstay clearance at that width. The Profile website suggests a 6" axle somewhere too, so I'm going to give it a shot.

I've been dragging my butt on buying the parts because they're pricey and hard to find outside of the US. I'd love a titanium axle, but the cost with exchange and shipping is crazy. I found a reasonably priced new chromoly axle on Ebay and have it in shopping cart, now I just need to bring myself to buy something from the US...

 

[rentedmule]

2.5 months later and I finally have the cranks installed - good thing I don't get paid by the hour.

I used a 68 mm Euro BB with a 6" gun drilled hollow (GDH) chromoly axle. That length worked fine, with lots of spindle engagement on the arms, but a 6.25 would have been optimal. I needed to space the drive side arm out about 10mm because the chain ring was scuffing the BB around where the ring bolts were. I probably could have filed the chain ring. Otherwise, the install was easy with the proper Profile GDH install tool.

20250703_182451 by Rented Mule, on Flickr

They feel as stiff as you'd expect - absolutely rock solid. I didn't weigh them, but they feel ~50% heavier than an aluminum DH crank like a Hussefelt or RF North Shore. I think the bike is still under 30 lbs, but I haven't weighed it. It certainly feels fine for a trail ride.

20250703_182443 by Rented Mule, on Flickr

There are still a few things I need to fix/change on the bike before I'm calling it done. The 2.4" rear tire rubs the chainstay, so I need to get a 2.25", and the titanium XTR cassette is worn out . The stem is a random Easton EA90 I had and it doesn't fit the aesthetic. I also like the TRP Spike cable discs for the simplicity and lack of maintenance, but something vintage and billet like Hopes would have more cool factor