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Discussion Starter · #1 ·
Hello!, so Just got a used bike, put new NSK 6903-DUs in the rear hub for the wheel bearings (cartridge bearing rear hub)
go to adjust it so that i'm not crushing the bearings against one side of the race and I always seem to have play in the rear. If I tighten it anymore past that it will feel notchy when I go to spin the axle which is obviously bad. its very very slight and accompanied by a very quiet knock sound (lateral play like grabbing the tire from 12 and 6 position like checking a ball joint on a car) Is this normal for cart style bearings?
 

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Elitest thrill junkie
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It is not normal to "adjust" cartridge bearings. That's what makes them cartridge bearings. They are pressed in. This doesn't sound normal at all.
 

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Discussion Starter · #3 ·
It is not normal to "adjust" cartridge bearings. That's what makes them cartridge bearings. They are pressed in. This doesn't sound normal at all.
Yes, maybe not "adjust" but to clarify its a 12mm thru axle with the right side having 2 nuts one to take up slack and then a lock or jam nut to lock it in place. now you can technically adjust this by making the slack nut tighter however as I described above it puts too much axial load on the bearing and it binds up. And the play I'm talking about is very minimal you really have to try to feel for it. These are very high quality bearings made in japan from NSK so I doubt its that and they were pressed in by me with no issue at all. some say its normal to have a very tiny amount of play, some say its not I read. Just hoping to get an answer from someone who's done a lot of cartridge bearing replacements!
 

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Elitest thrill junkie
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Yes, maybe not "adjust" but to clarify its a 12mm thru axle with the right side having 2 nuts one to take up slack and then a lock or jam nut to lock it in place. now you can technically adjust this by making the slack nut tighter however as I described above it puts too much axial load on the bearing and it binds up. And the play I'm talking about is very minimal you really have to try to feel for it. These are very high quality bearings made in japan from NSK so I doubt its that and they were pressed in by me with no issue at all. some say its normal to have a very tiny amount of play, some say its not I read. Just hoping to get an answer from someone who's done a lot of cartridge bearing replacements!
I've done a lot of cartridge bearing replacements, but that sounds totally fishy. What you are describing is an angular contact cup-n-cone bearing system, those are the ones that use the jam-nuts.

What is the brand and model of the hub?
 

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Discussion Starter · #5 ·
I've done a lot of cartridge bearing replacements, but that sounds totally fishy. What you are describing is an angular contact cup-n-cone bearing system, those are the ones that use the jam-nuts.

What is the brand and model of the hub?
I believe its a formula DC-1248, virtually no info on its existence online and I assure you it has the jam nut and the little adjust nut both use a 19mm thin spanner ONLY on the right side it has this. Has the 3 paw shimano style freehub, then you got the left side axle bearing behind that and then behind that one the right side axle bearing then a little dust seal that goes over the right side bearing and the adjuster nut I guess you'd call it then the lock nut. The one I'm describing that you adjust just pushes against the inner race of the right side cartridge bearing using this nut. hopefully that sounds familiar ha. bikes a 2020 Raleigh Tokul 3 with factory rear hub. the front is a loose ball cone style and that one I got adjusted perfectly with no issue. Copy paste link to bike Raleigh Tokul 3 Mountain Bike - Americancycle.com
 

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Elitest thrill junkie
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I see, and I see a parts kit for the hub online, which has all the parts set out. That is one strange configuration for a hub and there are several red flags there. The part that is tightening/snugging up against the bearing should only contact it at the race, the inner metal ring of the bearing. If it's contacting it anywhere else, like on the seal or outer race, it's going to destroy the bearing pretty quick. If you are able to snug it up with no play, it contacts the right race at the base, and it still does this, it's likely something is out of spec or damaged on the hub. It may be an ovalized bearing receptacle, bent axle, etc. These would be slight imperfections not visible to the naked eye. It's possible the bearing is out of spec, but extremely unlikely, given it's a new bearing. The usual test is if it spun freely and smoothly before pressing it in there, then it's probably what you are pressing it into that is the problem. The same I said above about where the bearing contacts the jam nut thing also holds for installation, although it depends how you are pressing the bearing in, if it's going into the hole, you do it by the outside race. If it's going onto the axle, you do it by the inside race. Most tools cover both of these so that neither one gets loaded more. Never press a bearing in on the rubber seal area. Also, are you sure the bearing is fully seated?

It's a very odd system on that hub, but usually any play is bad and will kill bearings relatively fast.
 
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I had a stock rear Formula hub (12×148 ta) with cartridge bearings that had play/knocking. Mine had to be pre loaded with cone nuts as the cartridge inner races weren't 'locked'. To my surprise it didn't have any shoulders on the hub axle or a sleeve/tube to butt up on the inside of the inner races that I fully expected to see in there.

Got it running okay by doing the same sort of pre load method used on cup and cone hubs. Hub worked fine for the time I owned it but was never happy with that set up and placing axial loads on cartridge bearings so sold the wheelset on.
 

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Discussion Starter · #8 ·
I had a stock rear Formula hub (12×148 ta) with cartridge bearings that had play/knocking. Mine had to be pre loaded with cone nuts as the cartridge inner races weren't 'locked'. To my surprise it didn't have any shoulder on hub axle or sleeve/tube to butt up on the inside of the inner races that I fully expected to see in there.

Got it running okay by doing the same sort of pre load method used on cup and cone hubs but was never happy with that set up especially on a cartridge hub.
YES this is what I was doing pretty much and the tube between the inner races makes sense given the design of the bearings this hub takes.. Terrible design I think but I guess maybe get a new hub haha.
 

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Discussion Starter · #9 ·
I see, and I see a parts kit for the hub online, which has all the parts set out. That is one strange configuration for a hub and there are several red flags there. The part that is tightening/snugging up against the bearing should only contact it at the race, the inner metal ring of the bearing. If it's contacting it anywhere else, like on the seal or outer race, it's going to destroy the bearing pretty quick. If you are able to snug it up with no play, it contacts the right race at the base, and it still does this, it's likely something is out of spec or damaged on the hub. It may be an ovalized bearing receptacle, bent axle, etc. These would be slight imperfections not visible to the naked eye. It's possible the bearing is out of spec, but extremely unlikely, given it's a new bearing. The usual test is if it spun freely and smoothly before pressing it in there, then it's probably what you are pressing it into that is the problem. The same I said above about where the bearing contacts the jam nut thing also holds for installation, although it depends how you are pressing the bearing in, if it's going into the hole, you do it by the outside race. If it's going onto the axle, you do it by the inside race. Most tools cover both of these so that neither one gets loaded more. Never press a bearing in on the rubber seal area. Also, are you sure the bearing is fully seated?

It's a very odd system on that hub, but usually any play is bad and will kill bearings relatively fast.
Visually there was nothing wrong. Its just some of these generic parts that come on these bikes that are like these hubs have like NO service information, I cant even find the DC-1248 on formulas own web sight, probably for good reason. But what the reaper guy said I think is it. That there should be some sort of link between like a sleeve or a tube to connect the inner races on the inside but there is none, it's just sandwiching the race against nothing on the right side for a bearing that not really designed to do that which is why I'm so confused lol. But anyway, yes the adjustment nut contacts the inner race nothing out of the ordinary there. Might just get like a DT swiss 350 or something because I literally go this bike lightly used, rode on one trail and the rear started knocking. And that is why I replaced them. I'm just going to do my best and get a different rear hub maybe. The problem seems to be the design possibly. Or maybe I can get to the bottom of this lol.
 

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I put it down to Formula hubs being cheap, cost cutting pieces of sh#t! That stock hub stung me after I realised what brand it was, especially after I swore to avoid Formula hubs from a previous experience. 🤬

Got Hope hoops with Pro 4's now, worth the cost, very happy with the upgrade and recomend binning that hub and go for something a lot better. 😃
 

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I had a stock rear Formula hub (12×148 ta) with cartridge bearings that had play/knocking. Mine had to be pre loaded with cone nuts as the cartridge inner races weren't 'locked'. To my surprise it didn't have any shoulders on the hub axle or a sleeve/tube to butt up on the inside of the inner races that I fully expected to see in there.

Got it running okay by doing the same sort of pre load method used on cup and cone hubs. Hub worked fine for the time I owned it but was never happy with that set up and placing axial loads on cartridge bearings so sold the wheelset on.
Found some pre sale pics of my Formula hubs:-

Rear.
Bicycle Bicycle wheel rim Wheel Bicycle wheel Bicycle hub


Rear.
Bicycle Bicycles--Equipment and supplies Bicycle wheel rim Wheel Crankset


Front.
Bicycle Bicycles--Equipment and supplies Bicycle wheel rim Wheel Bicycle hub


Front.
Bicycle Wheel Bicycle wheel rim Bicycle tire Bicycle hub
 

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Cool. Good choice imo. 😎👌 I'm not a wheel builder and never attempted that job before.

I bought a Hope Fortus 30 wheelset for a good price and really, really happy with them, especially those Pro 4's.

DT Swiss were the next on my list as replacements and reckon they're very good too.
 

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Discussion Starter · #14 ·
Yeah, I was torn between the DT and the pros but I feel I like the sound of the 4 more. I plan on just taking it when it comes in the mail to a bike shop so they can rebuild my rear wheel with the same rim and hopefully the same spokes if the flanges are the same dimensions. The wheels and spokes I have are in really good shape so I couldn’t justify just buying a whole new wheel set just for the rear hub so I just got the hub itself. Thanks for the help to!
 

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Search Sram MTH748. It’s the same garbage hub! No matter how you adjust it the adjustment always moves and the hub either develops play or locks up. I broke a freehub on mine after 600km and got a new one under warranty. Quickly sold the wheelset and swore never to touch these again. A few friends have broken axles on theirs and all the ones I’ve seen were the same: the adjustment never held for very long.
 
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