Spanish BB - Sram GX cranks

[Private Repress]

Hi all, 

embarking on a new project and have hit a barrier. I’ve got a frame with a Spanish bb (37mm shell)

I want to run Sram GX cranks with minimal fuss, these ones:

 

Is there any adapter that exists so that I could simply run the external threaded sram gxp bb on the Spanish bb shell? 
 

I’ve seen @Swoofty YouTube guide, but that seems to be a case of replacing the bearings to a suitable size to fit the axel, then working out what spacers would need to be ran either side of the crank. Not sure the parts are easily available to achieve this in the uk.

I spoke to Charlie at Tarty bikes that suggested this truvativ adapter, but it seems this is for the larger American bb?

 

any help would be much appreciated

[Mark W]

Unfortunately there's no adaptor for Spanish to BSA. BSA threads are a shade under 35mm, so there's basically not really the room within the shell to actually fit any kind of adaptor between the Spanish BB bearing race and the BSA cup.

You could theoretically do what Swoofty said and just find bearings that have the right axle diameter, but from memory the GXP BB axles are stepped so you'd need a different size bearing for each one. I would have thought the chances of the bearing races on the axles lining up with an inboard-positioned BB would also be slim. If that's what Swoofty has managed then fair play to him!

[Private Repress]

Ah thanks @Mark W that makes perfect sense. I was thinking a press fit with the thread sitting outside of the frame, making it a 73mm shell. That said there’s only room for 2.5mm on each side to do that - bummer! 
 

looks like I’ll be sticking with a splined axel. 

unless there’s any decent trials alternative that fits a Spanish bb…

[La Bourde]

The SRAM gxp axle diameter is 22 mm onone side and 24mm on the other.

There are some bearing with ID 25 and OD 37: the 61805.

Then you need the plastic sleeve that is pressed in the bearing of a shimamo bb to run a 24mm axle.

Enduro bearing has a bearing with ID 22 and OD 37. 

With some spacers that shall work.

But not sure the result will be great.

[Swoofty]

Yeah it's all true what you've said. You can get 37x24 and 37x 22 bearings, but the GXP 'step' is farther from the BB so a 37x22 doesn't really help unless you're just using an isis axle. Racing line make/made some press fit Spanish to BB30 cups, but the interface walls are pretty thin and it's not 24mm. Hambini will make you some titanium Spanish to BSA cups that will fix you up, but the price is likely silly just to run gxp cranks. Otherwise you do just what I did with pressed 37x24 bearings and then 24mm and 22mm spacers to suit. I'd certainly rather my Czars had wider bearing spacing, but honestly I don't notice so much. It's even less noticeable with shorter crank arms. Good luck!

 

PS- if you do press in 37x24x7 bearings, remember Spanish bearings are 9mm thick so you'll need to take up those extra 2mm between the bearings and the frame. I used a 2mm spoke bent into a circle. So far so good after 3 years.

Edited March 24, 2023 by Swoofty

[Private Repress]

@La Bourde @Swoofty thanks guys, really appreciate the advice, which has put an end to hopeful internet searching!
 

I’ve decided to run the bb with the axel already installed with some middleburns. It’s the cleanest looking set up in my opinion without being able to run the gx’s. 
 

The cranks will need cleaning up, and I’ll likely powder coat them black to match the theme I’m going for with the bike. Build thread to follow!

[Mark W]

Have you checked the Middleburns definitely fit? Seem to remember a lot of newer frames had/have compatibility issues with them due to the low Q-factor/offset they've got. Might be worth throwing them on if you haven't already just to make sure before you spend some money on them.

[Private Repress]

Thanks @Mark W thankfully it came with the middleburns on;

Edited March 24, 2023 by Private Repress
Typo

[Swoofty]

Now that is a sweet lookin ride! Needs eeWings

[Private Repress]

4 hours ago, Swoofty said:

Now that is a sweet lookin ride! Needs eeWings

Haha! I’d still be stumped for a bash guard!

The bike is getting a bit of an overhaul. Just rebuilt the back wheel onto a black Hope hub, new chain and a 17t sprocket ready and waiting.
 

It came with Shimano XT brakes, and I happen to have a spare mt4 calliper and a spare MT5. So very likely I’ll be running shiguras. 

Oh and I’ve spent about 8hrs in total trying to remove the paint!

 

slow progress, but I like to put my own stamp on a build.

I’ll do a build thread once I get a bit more done 

[Private Repress]

@Mark W @Swoofty @La Bourde

Right guys, I’m in the rabbit hole now. I figured some sort of custom push fit adapter could be made. Got talking to a mate who thinks he can do it on a lathe. 

Essentially it will be very similar to the racing line push fit cups (which I can’t find an anywhere in stock).

I’ve ordered these bearings that are gxp bb replacement bearings. 

let’s see where this goes! 

 

[Mark W]

On 3/25/2023 at 1:18 AM, Private Repress said:

Haha! I’d still be stumped for a bash guard!

The Inspired Integrated bashrings fit them, plus you can get SRAM direct mount double spiders so you could run a 4-bolt bash and 4-bolt chainring if you were so inclined...

16 hours ago, Private Repress said:

@Mark W @Swoofty @La Bourde

Right guys, I’m in the rabbit hole now. I figured some sort of custom push fit adapter could be made. Got talking to a mate who thinks he can do it on a lathe. 

Essentially it will be very similar to the racing line push fit cups (which I can’t find an anywhere in stock).

I’ve ordered these bearings that are gxp bb replacement bearings. 

let’s see where this goes! 

 

Are those bearings sized to fit straight inside the normal SRAM cups, so you'll basically just be pressing a sleeve into your BB that the bearings will then go into directly?

I still don't really see how it all fits together properly in light of the non-drive bearing seat being way out of place if the bearings you're using are going to be within your BB shell (rather than being an external cup, where the inside edge of the bearing would be around 8-9mm further outboard than it will be if they're located inside the shell)... I know the drive-side bearing can pretty much go wherever on the axle as that's how they're designed to work - it's just the non-drive side, and getting things lined up properly I'm struggling to get an idea of. Intrigued to see how you get on though!

[Private Repress]

@Mark W My thoughts are to machine external cups that house the new bearings, the cups will push fit into the Spanish bb shell. Machining the cups in theory should mean that I can position the new bearings exactly where they need to be in relation to the crank spindle. 

whether this will work, I’m not sure. 
 

the inspiration for this came from these, which are Spanish to BB30:

 

 

[Private Repress]

@Mark W if all goes to pot, I’ll run the middle burns that I already have, if I really get on we’ll with the frame - I quite like the look of the inspired Bmx style cranks which I believe can be ran on a Spanish bb?

[MaderaMark]

On 3/24/2023 at 7:23 PM, Private Repress said:

Thanks @Mark W thankfully it came with the middleburns on;

that fork! ohhhhh so sexy!

 

[Mark W]

14 hours ago, Private Repress said:

@Mark W if all goes to pot, I’ll run the middle burns that I already have, if I really get on we’ll with the frame - I quite like the look of the inspired Bmx style cranks which I believe can be ran on a Spanish bb?

Yeah, you'd just need to get a 22mm Spanish BB and the Arcade V2s would slide straight in there  One of the prototype Arcade frames had a press-fit BB and was used just like that.

Makes sense with the Racing Line-style cups. At least you've got a bit of room to play with in terms of how thick you can make the adaptor, should be fairly straight forward to get it strong enough  

[Eldertroll]

My old bike this. I lathed the bash down etc. specs changed a fair bit from when I sold it 

Edited April 2, 2023 by Eldertroll

[Private Repress]

@Swoofty @Mark W @La Bourde

after a lot of measuring, and some amazing lathe work here is the finished product:

 

I’m yet to build the whole bike up, but it feels good turning by hand, and I can’t feel any play (I’ll know immediately if there is any once I ride it). 
 

Super happy with how this ‘turned’ out

[Swoofty]

Well done! That looks great! What flavor aluminium did you use?

[Private Repress]

59 minutes ago, Swoofty said:

Well done! That looks great! What flavor aluminium did you use?

The heavy one, stainless steel haha 

[Swoofty]

Oh right, steel frame. Good thing you're paying attention!

[Ross McArthur]

Excellent work Gav!

Frame finish looks cool too.

Duck, Duck, Goose!!

[Private Repress]

14 hours ago, Swoofty said:

Oh right, steel frame. Good thing you're paying attention!

@Swoofty To be fair, if I was being weight conscious I probably would have gone for aluminium and used a compound to prevent ceasing. But the stainless steel was readily available and didn’t cost me a penny (I’ve built several wheels for my mate so it was a favour). Thanks again for the pointers on this conversion and inspiring a solution!