rear bearings and cassettes

david stratton · Joined: 27 Jul 2001 Posts: 23 Location: houston

i never thought about this before, but.............should the rear bearings still be free to float inside the cassette once the entire assembly is installed, or should the cassette be snugged down after the assembly is complete

Rick Blood · Posted: Thu Oct 25, 2001 6:13 am Post subject: rear bearings and cassettes

If you tighten down the clinch bolts, the bearing race will deform and cause drag and undo wear on the bearing. It will also stiffen the chassis.

Roger Miller · Posted: Thu Oct 25, 2001 6:55 am Post subject: rear bearings and cassettes

Yes, absolutely. They should "float" but without play. Use assembly lube, moly-lube, anti-sieze, or similar material on the bearing and cassette mating surfaces. A light film is sufficient.

Stan Smith · Joined: 22 Aug 2001 Posts: 36 Location: Afghanistan,

quote:
Originally posted by Roger Miller:
Yes, absolutely. They should "float" but without play. Use assembly lube, moly-lube, anti-sieze, or similar material on the bearing and cassette mating surfaces. A light film is sufficient.

Does alot of people do this. I never herd of it before ? Sure sounds like it might be good.

Chuck Bunnell · Posted: Wed Oct 31, 2001 7:49 am Post subject: rear bearings and cassettes

Definitely. Greasing the mating surfaces of the cassettes and the bearings is a requirement. First it makes assembly that much easier and second, helps prevent corrosion down the road that will inhibit the whole point of having a spherical bearing mount. The bearings must be able to rotate within the cassettes after everything is totally assembled. That's the whole point to avoid excessive loads on the bearings causing excessive drag, that's what the term "chassis bind" is referring to. Note that the fit between the bearing and cassette is noticeably snug. A slip fit will not work. It should take a fair amount of effort to rotate the bearing in the cassette; that's normal and required.

You may need to add re-lubing the bearings and the cassettes to your maintenance schedule.

Andy Szyszkowski · Joined: 01 Aug 2001 Posts: 149

I would suggest that you not overlook the bearing hanger itself. If it is not flat, due to poor fabrication or perhaps bent from an accident, then after tightening you may defom the cassette and cause the bearing to bind.

Andy

Graeme · Joined: 02 Nov 2001 Posts: 17

I have 1 two piece "quick release" cassette which seems to clamp aronud the bearing pretty tight.

The bearing even spins much freer when out of the carrier due to it clamping down, is that too tight and how would I loosen it up to allow it to rotate?

Thanks!

Roger Miller · Posted: Thu Nov 01, 2001 10:19 pm Post subject: rear bearings and cassettes

Graeme, if you mean two piece, as in, two circles, that come together with the bearing in the middle, then what you do is place shim stock between the halves when you tighten it down. This spaces the rings apart and relieves the pressure on the bearing outer race.

I have these on our TrackMagic.

Mike Conser · Joined: 02 Nov 2001 Posts: 114

Roger, I have a 97 trackmagic, and for the life of me I cant get the axle to spin freely when I put the axle back in. How do i get the bearings centered and straight in the cassettes, and what size shims do you speak of. Any advise you have would be great. Im new to the sport this year, so any tricks you might have for this frame would be nice.

[ November 02, 2001: Message edited by: Mike Conser ]

John Learmonth · Posted: Sat Nov 03, 2001 3:50 am Post subject: rear bearings and cassettes

quote:
Originally posted by Mike Conser:
Roger, I have a 97 trackmagic, and for the life of me I cant get the axle to spin freely when I put the axle back in. How do i get the bearings centered and straight in the cassettes, and what size shims do you speak of. Any advise you have would be great. Im new to the sport this year, so any tricks you might have for this frame would be nice.

[ November 02, 2001: Message edited by: Mike Conser ]

The slightest bend or bow in the axle will create some bind when all three bearing hangers are tight in the chassis. If the bearings have neoprene seals then you'll also get some bind from the friction at the seal lips (2 seals per bearing X three bearings = 6 friction points).

Keep on mind that even if you achieve a very free spinning axle when no weight is in the kart, when you sit in it the axle will be slightly bowed down in the middle, and this will introduce some bind into the axle that won't be apparent when you check for bind on the stand. Perhaps the best way to achieve a 'dynamically' free spinning axle would be to only tighten the third (middle) bearing to its hanger when driver weight is flexing the axle???

Its easy to get fussy about axle freeness, the reality is if it spins with little resistance this is good enough, it doesn't need to spin 'forever'.

Roger Miller · Posted: Sat Nov 03, 2001 6:01 pm Post subject: rear bearings and cassettes

Mike, shim stock comes in various thicknesses, but I use .002 material generally. Cut three pieces, slip in between the bolt holes in the cassette, so they are between bolts, and equidistant around the ring, and this should take the pressure off of the bearings.

It sounds like you might have other problems.

First, are the bearings reasonable free, packed with grease? If you have three bearings with grease, it won't just spin on the stand. It's probably fine on the track. That was a whole other thread.

Once it is all installed, and the mounting bolts still not tight, and brake rotor not dragging on the caliper, and the clutch/chain whatever, not connected (so it isn't dragging, try spinning a 3 disk wet clutch on a Super Sportsman)... if all that is OK, then, the axle should be able to spin as free as the bearings allow...

Then, begin tightening up all of the mounting bolts, together, and checking the axle "freeness". If it gets tight, then something is out of alignment, or, those cassette halves are too tight.

One other tip, don't put in any of the set screws for the bearings, or, any axle collars, (whatever you choose to "set" the axle) until the absolute last thing. Its possible to create a side load.

[ November 03, 2001: Message edited by: Roger Miller ]

Mike Conser · Joined: 02 Nov 2001 Posts: 114

Thanks roger and john, I am very appreciative of the advice. as i read on later i saw that i needed to lube the cassettes, which i never did before. I figure that with the shims should solve my problem. what do you guys think of getting rid of the third bearing, middle, all together for running the hard tire?

Roger Miller · Posted: Mon Nov 05, 2001 6:45 am Post subject: rear bearings and cassettes

So far, sprinting, for both hard and soft tires, we have been running the third bearing loose. No bolts, fixed with ty-wraps. We have tested bolted it in and it tightens up the rear on our chassis. So, if we needed the grip, we would bolt it in but that hasn't happened yet. This is junior classes. For heavy classes with more HP, you probably need to do A/B tests with it in and out back to back and see whawt changes it make.

On the roadracing chassis, that bearing is removed completely.

Graeme · Joined: 02 Nov 2001 Posts: 17

This topic is intreging [sp?] me...

The cassette I ahve is not split vertically (two circles side by side), it is actually cut horizontally (two half-circles). That makes the shim thing s a bit harder as any shim makes it distort the shape of the cassette.

Can a bearing be bought with the same inner diameter for the axle (i.e. 40mm) with a slighly smaller outer diameter (to be less of a squeeze into the cassette?
Also, are there such things as "low-friction" bearings or something, new ones are not very free spinning and anloy improve marginally once I get all the grease out.
I have two that fly around but that's mainly due to excessive wear which can't be right leaving them ON the kart.

Thanks for all tips.

Roger Miller · Posted: Mon Nov 05, 2001 3:12 pm Post subject: rear bearings and cassettes

Same deal with those cassettes Graeme. Use shim stock between the halfs, punch holes for the bolts to go through. THe small amount of spacing using .002 shim stock will free up the bearing and still hold it securely.

I am not a bearing expert, all I know is that I try to find the zero contact seals, and remove the grease, lube with high quality oil, and off we go, it's true that as they wear a bit, they get freer, but that is only unloaded and I don't think indicative of the "freeness" when rolling on the ground with all the weight on it.

I do work on a free spinning axle, but, I don't lay awake at night over some amount of tightness I know is in the bearing itself, or, in the state of the lubrication.