fitting small axle wheel to big axle bike, is this safe?

[Roaduser]

i have a 5 spoke dss wheel from an ss(small axle), and my bike is a m800(big axle).

here is the situation. the bearings for the big axles are thinner than the small axle bearings this wheel was originally designed for and had. so when i pressed the big axle bearings in they went flush to the external surface of the hub, were good and tight, and the inner axle tube is snug in there like it should be, but the bearings are not hard into the inside radial surface of the wheel hub like they would normally be.

considering the inner axle tube is there and holds the bearings spaced and that the swing arm or axle wont induce any axial force on the bearings themselves i don't think this could cause any issues with these parts as they cant move in respect to the swing arm or each other. but it is theoretically possible that the wheel could float axially on the bearings. i really don't know how much force would be required to make the wheel float nor what could or would cause such a strong axial force on the wheel, again, the bearings were very tight in the wheel as they should be. but if it did happen, depending on which way it went, either the tyre would rub on the chain or the brake rotor would push out on the pads/caliper.

the bearing thickness difference looked to be less than 3mm at a guess. i honestly didnt measure it but will when i get home.

a fix i could do if this is thought to be a problem is to pull the bearings out (wrecking them ) and then machine some spacers to the same inner and outer diameters as the bearings and put them in between the bearings and wheel hub.


What are your opinions on this? should i not worry about it or would you guys recommend i buy a new set of bearings and machine some spacers. and yes i know i should have thought about/asked this before i put the new bearings in, but the old ones were such a pregnant dog to get out that i got a bit excited when i had them out!!

Cheers Clint

[64duc]

  Take both bearings to a bearing supply house and explain your situation to them. They can then give you the correct size bearings.

[atomic410]

I had an aftermarket rear that I was going to do this with but ran into a problem with the cush drive/carrier bearing being too small. I would have been running a big risk on the race track with it.

[Ddan]

I don't understand how the internal axle spacer can be tight to both bearings if they aren't fully seated.  Regardless, I think you need to either get the right sized bearing, or press them all the way in and make spacers to take up the difference

[Roaduser]

I don't understand how the internal axle spacer can be tight to both bearings if they aren't fully seated.  Regardless, I think you need to either get the right sized bearing, or press them all the way in and make spacers to take up the difference

the inner axle spacer fits because the external width of the whole hub is identical on both wheels. so when i use bearings and inner tube from one in the other it all fits correct with respect to the external faces of the hub. the difference is in the depth of the wheels bearing recess' which allows there to be a gap behind the bearings on both sides.

yeah i wish i could just push the bearings in more and put a spacer on the outside but the inner tube prevents that. to machine the tube id have to pull the bearings so i may as well put the spacer on the inside like it should be. thanx for the thought tho man.

  Take both bearings to a bearing supply house and explain your situation to them. They can then give you the correct size bearings.

assuming they have bearings with such minor size increments, id have to machine down the inner tube to be narrower. the inner tube has a flange of sorts on it, so if i machined it down the bearings would be against a thinner section of the tube which i dont think would be a problem unless i changed to another wheel designed for the big axle bearings. ill have to make some calls, thanx.

additionally i cannot use the narrower inner tube originally with this wheel as it has the small axle hole through it.

I had an aftermarket rear that I was going to do this with but ran into a problem with the cush drive/carrier bearing being too small. I would have been running a big risk on the race track with it.

could you not source a wider sprocket carrier? with a 180 tyre on this 5.5in wheel im very close. maybe under some circumstances it may touch occasionally but thats not uncommon on some motards and dirt bikes. im still to look into what i can do to gain a little extra space. i know i can flip the front sproket but doing so will require a wider carrier or some form of spacing to keep the chain in line. any findings u have from your attempt would be great thanx man.

so far you guys are making me feel like its unsafe, so i think the best option still remains to make a pair of spacers that are the same external diameter as the bearings and a internal diameter large enough to go around the inner tube and replace the bearings.  my bad.

any further thoughts welcome.

[Speeddog]

Make some spacers to go between the inner faces of the outer races and the wheel.

Install with new bearings.

[Roaduser]

cool, consider it done.. 

now the sprocket carrier... im looking at options to move the chain a little further from the tyre. its probably not needed but im looking at the options.

The info: the sprocket carrier i have from the monster was for a 4.5in wheel and runs the chain too close/rubbing the tyre when used on the 5.5in wheel with 180 tyre. i see there are different part numbers for the sprocket carrier/flange for the baby monsters compared to the s4/st4 and again different from the ss. also im finding the tyres stated as being 160, 170, and 180 respectively.

The Questions: can someone confirm for me that the only part changed to move the chain out on the ss was the sprocket carrier/flange and the flipping of the front sprocket, in which case a carrier from a ss will move the chain out to the right spacing as a flipped front sprocket? is the s4 different spacing altogether or could i use an s4/st4 carrier too?
did the ss have a 5.5in wheel same as the s4 but simply ran a 170 tyre instead?
or the even simpler but possibly crude option, can i space the sprocket off the carrier to match/line up with a flipped front sprocket, or would such a thing be shied upon?

[ducpainter]

If you get a carrier and spacer for a 5.5 wheel you'll be good.

Many of the mid 90's bikes ran a 170 on the 5.5 wheel.

I wouldn't space the rear sprocket...it might work, but I wouldn't do it.

[atomic410]

could you not source a wider sprocket carrier? with a 180 tyre on this 5.5in wheel im very close. maybe under some circumstances it may touch occasionally but thats not uncommon on some motards and dirt bikes. im still to look into what i can do to gain a little extra space. i know i can flip the front sproket but doing so will require a wider carrier or some form of spacing to keep the chain in line. any findings u have from your attempt would be great thanx man



no I couldn't.  marchesini changed their cariers right after this wheel was made.  the one's i could source were crazy expensive and made the total with bearings and machening at almost the cost of a new wheel with the wheel price.  too bad too was a sweet wheel.  afwiw my tard gets chain rub on the tire but its pretty rare when i lean the tard as hard/fast as my road race bike.  i'm not sure i'd be cool with my road race rear tire edge being chewed up by the chain not to mention the chain lube on the edge of the tire aspect