Ok so big news if you haven’t already seen our new 125mm rubber wheels that’s ok because we’re changing them…
drum roll
We are making the switch to 28mm bearings and a new pulley pattern.
You might be wondering why are they doing this now?
Well here are the main reasons:
The off road version of the Mach1 is going to use 10mm axles, and it’s horrible having multiple variants of everything (standard Mach1 uses 8-9mm stepped axles).
The switch to 28mm bearings will mean boards like the Lacroix Nazare which have range and power can run these wheels instead of us being so concerned with small Chinese boards that these wheels don’t suit anyway.
Bearing lifespan is not great on the prototype SR125’s even with Zealous - our wheels need bigger balls.
To make 8mm axles work they need to be made with European steel and heat treated to a high standard, making the Mach1 axles crazy expensive.
Aluminium Kegel pulleys are heavy and expensive to make, and require a bearing that wears out because it’s almost impossible to shim them so they don’t end up taking the cornering loads.
The Kegel and Abec patterns don’t work with 28mm bearings, so a new mounting pattern is required.
Presenting our solution, the new updated SR125 wheel system.
With 28x8mm bearing seats and 22.5mm standard MTB spacing bearing lifespan won’t be an issue and standard sizes are available to support 8, 10 and 12mm axles.
Featuring a new 12 hole pattern on a 35mm pitch circle diameter. Made for 5.5mm dowel pins that still allow for gear drive possibilities and keeps weight down. However our pulleys don’t use dowel pins anymore.
4 of the 12 holes are threaded, allowing a pulley to bolt directly to the wheel. A locating lip ensures the pulley runs true, and the big 28mm bearings easily support the load without the need for a pulley bearing, reducing failure points and rolling resistance.
Instead of 137g the new pulleys weigh just 28g each reducing overall weight and inertia.
I tried to consider as much as possible with this new system, and I’m hoping it can become the new eboard standard for sub ~130mm wheels. Perhaps wishful thinking but someone has to do something.
Nothing is set in concrete just yet, so let me know your thoughts/questions!
Sounds really cool that you made the switch to 28mm bearings. In my opinion that was the right choice. It’s cool that you shared the pattern for other people as well
Just out of curiosity, could you share some of the dimensions of the pulley centering lip as well?
Not gonna lie I kinda want to try these on my BN-AT drives hahaha
Looks cool, does the threaded core mean it has to be made of metal? Just with the MTB-style pulleys without a bearing it looks like there are more load applied to the thread than there would be with a pulley bearing. Maybe I’m missing something and it’s still not an issue, but it seems like either a metal core would offset the weight savings, or a PU core with a cantilevered load could be a point of failure
Are these going to be what the current set of SR125’s sold will have? And is this going to be the core of choice going into the future? If it is, i’ll start developing my own parts to fit them haha. Sure beats the solution i was working on LOL (my own custom pulley teeth for BN kegel pullies)
I would suggest putting that locating lip on the pulley and not on the wheel (as it’s currently pictured). If that very narrow lip is on the wheel, then it could get damaged much more easily. And once it’s damaged, it could require replacing the wheel.
If the lip is on the pulley, then the chances of it getting damaged goes way down because the only time the pulley is in use is when it’s installed on the wheel, therefore engaging that lip and protecting it from damage. Plus if somehow it does get damaged, you can replace a pulley much more affordably.
Having threaded holes as well as normal ones for dowel pins is a super clever solution! I like that it gives pulley manufacturers options.
I’m curious why you decided to move away from the 10-hole pattern. In my opinion, the larger pattern present on the Dadbod wheels seemed to be Orangatang’s (small) push for the community to switch to that pattern for future wheels that use 28mm bearings.
12 holes gets a nice symmetrical threaded pulley interface, but there’s no reason there couldn’t be 4 out of 10 threaded holes instead, just at angles other than 90°.
Reusing Orangatang’s pattern would require the locating lip to be on the pulley instead of the wheel like others have mentioned, but do you think it would be worth sticking to their pattern since other large urethane wheels will likely be made with that core?
Yes in fact I encourage others to adopt this pattern and hope this can become a new standard.
Good point, just updated the post with dimensions for that.
The spacers MBS sells on their website are listed as 22.5mm. Can someone confirm?
To mount a pulley to the hub this way it ideally should be metal, but I do think it’s possible to do a urethane core mounting the pulley this way using through bolts and nuts. But it’s also possible to make a pulley with pins and a bearing that mounts like a Kegel pulley.
Yes we have to commit to one system because the tooling costs are high. Those who’ve already ordered and can’t use the new system will be fully refunded if they wish.
Fair point about damage, however putting the lip on the pulley will increase the pulley cost and because the lip interferes with the holes there will be heaps of sharp edges in the hub where the groove cuts into the holes.
There isn’t space to thicken the ring without colliding with the mounting holes in the pulley. And if we increase the size of the hole pattern, the weight starts to increase quite a bit. The centering ring isn’t super essential as tight hole fitment will also keep the pulley fairly centered. I’d rather keep the design light weight and affordable if possible but keen for further suggestions.
I thought so too and wanted to use it, but once I saw just how big the dad bod pattern actually is in CAD I realized its no good. It’s just too big which either means expensive or heavy hub design and same goes for the pulleys. It’s quite difficult making an aluminium hub that’s both light weight and affordable with low volume manufacturing techniques.
I’ve been working on developing some custom hubs for BRP racing wheels to take a kegel core pulley, but if this is going to be the standard going forwards, i might change out to the new radium standard.
Is the sizing of the holes on the core side exactly 5.6mm diameter on a 35mm diameter pattern? Or should there be some additional tolerance on the hole diameter? For the four threaded holes, what thread pitch are you using?
I guess the big question is how does this affect those who run ‘‘medium class’’ DIY’s, not china ones? Is there any reasonable way to upgrade existing systems that use cal2 trucks? For example 3DS/BN 200-300mm trucks? Maybe a radium hanger that could use old baseplates?
Design itself is excelent. It just feels like it leaves out everyone who doesn’t run radium or 300mm+ lacroix AT setup out of the loop.
Hmmm I’m team no spacer on mountainboards but fivestar and rockstar hubs both have 38.2mm outer bearing to bearing. With 2x 8mm bearings, that does point to 22.2 being the right dimension.
Fuck knows… i have a drawer that ive thrown mbs/mtb stuff into, theres a few others in there ill check… calipers defo read that on the one i measured mine must have extra gravity
mine must have extra gravity