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Rear wheel bearing discussion

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RobSelina

RobSelina

Jedi Warrior
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So I started replacing the rear wheel bearings yesterday. I completed the passenger side bearings and brakes and I understand now why we need double bearing hubs.

The bearings, even new ones, leave a lot of play in the hub face. When using stock ball bearings, I can see why you need double bearings to stop axle flange flex and breakage. The cost of these kits is high though, so I'm wondering what would prohibit the use of Timken style tapered roller bearings?

You could press the race into the hub along with the seal, then put the hub on the spindle and press on the tapered bearing, using the retaining nut for bearing tension. This (assuming i can find one that fits), would eliminate most of the flex at the flange and I don't see any adverse effects. I've only ever dealt with timken style bearings before the so the weakness in the single ball bearing design seems unecessary. I'm questioning if the timken conversion I'm considering is feasible though, since if it was, I'd assume it would be a standard conversion for most race cars instead of double bearing hubs.

So, where's the flaw in my logic?

Thanks, /ubbthreads/images/graemlins/cheers.gif
 
I'm not quite following what you propose, but I'm definitely interested in this line of thinking ... this would allow for FSP legal improvements (not that I really have that many qualms about breaking the rules for non-performance related reasons, but I'd rather they're not possible to prove). From what I gather, most national competitors in Solo tend to feel somewhat similarly, and generally only protest if it's a performance related improvement.

Of course, the rules-legal solution would be to write a letter requesting a rules change on the subject!
 
Hmmm?
This seems like a fair idea, but I feel like I'm missing something.
I wonder if this would stress the stub area of the axle housing even more (rememeber, I just bent one).
Anyone else want to chime in?

I'm adding a picture of a tapered roller bearing to help clarify things.

06-03-31-12-55-061143780906.gif
 
The bearing is a 207 series, the dimensions of the stock bearing (6207 or 7207) is 35 mm ID, 72 mm od, and 17 mm thick. A 32207 tapered roller bearing is the same id and od but is 24.25 mm thick. Dimensionally a cylindrical roller bearing like a NUP207E works but a roller bearing can’t take the side thrust that you would see, especially with race or AutoX rubber. I’ve got an old Bearing Manual set and I couldn’t find anything that would work without machine work. If anyone knows of something that would work I’d like to hear it as well.
 
I was thinking about the thickness issue, and by eliminating the stock seal, you could have quite a deep roller bearing. I think it would be relatively easy to add a seal on the back side of the hub. It would take a little cleanup with the lathe (as would deepending the bearing surface) but not much.

Now what do you mean about the side thrust? which force are you refering to?
 
oh, to clarify what I was proposing.

The outer race for the bearing is the top piece in Nial's photo. This would be pressed into the hub with the thicker side towards the seal (as noted in my last post, the seal may have to move). Then you place that hub assembly onto the spindle, and press on the bearing using a driver and then the retaining nut. These roller bearings would remove the flex you can get from the hub to axle flange.

In my mind it will work, but I'd like to hear more about what Chris is saying about side thrust.
 
Okay, reading up on bearings and Chris is right. Tapered roller bearings can support large radial loads (the weight of the vehicle under acceleration and deceleration) and thrust loads (ie, cornering), but only in one direction.

To use roller bearings efficiently, you need two of them, tapered in oposite directions.

So to continue this line of thought, we'd have to machine the spindle back to fit two of the bearings chris mentions, and also the hub far enough back to accomodate two (if even possible). Then move the seal to the back side of the hub.
 
When you go around a RH corner the body is pushing the axle housing left and the tire is pushing the hub right. A typical cylindrical roller bearing doesn't like this type of load; they are designed for radial loads like you would find in a pulley. The attached sketch shows a simple radial and thrush load on a ball bearing. In reality the force is only on the bottom (tire contact with pavement) and there is angular movement of the other race causing the axle to be stressed and the lip seal to loose contact with the rear end housing and oil to leak out. I hope I explained that right.
 

Attachments

  • 238689-BallBearing.JPG
    238689-BallBearing.JPG
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Sorry, I was trying to edit the attachment when you were putting up your last few posts. What you have pictured is a spherical roller bearing; the bearing number would be 21207. These are self aligning bearings, i.e. they are insensitive to shaft (axle housing) deflection. This is the problem that we are trying to address to keep the load off of the axle. If you used this the axle would be the only thing keeping the hub from rotating perpendicular to the axle, and I would expect the axle to snap.

If you look closely the rollers are opposite how they would be if it were two separate tapered roller bearings like the front conversion setup is. They are in a radial arc (best way I can think to describe it) with each other where they need to be opposite one another,

I’ve look at all these and I’m hoping I’m wrong, but I figure people have been trying to fix this for 40 years and someone a lot smarter than me would have come up with it already.
 
my head's starting to hurt, but I think I understand. I thought that bearing was retained in it's race, but if it's self aligning, you're right, it's the exact oposite of what I want.

So we'd actually need a bearing like this then?

unipac.gif


https://www.timken.com/products/bearings/products/unipac.asp

https://www.timken.com/products/bearings/products/TaperedRollerBearings/tworow.asp


BTW, looks like that unipac is presealed and lubricated, so we could eliminate the oil seal if the hub was machined to fit this larger style bearing.....
 
Chris,

I think I understand what you're trying to say, but I really don't see how the arrangement of the bearings is relevant. That bearing (the one before Rob's most recent post) is a tapered roller bearing as far as I can tell. I'm not sure what you mean about spherical bearings. Also, the arrangement shouldn't matter because either way, the axial load will be absorbed. However, I haven't thoroughly considered the bending load involved. That's what you're referring to with respect to leaking oil seals, I'm sure.
 
I'm glad there's smart folks like y'all in the world. I'm trying to follow this discussion and now my head hurts. /ubbthreads/images/graemlins/confused.gif
 
[ QUOTE ]
Chris,

I think I understand what you're trying to say, but I really don't see how the arrangement of the bearings is relevant. That bearing (the one before Rob's most recent post) is a tapered roller bearing as far as I can tell. I'm not sure what you mean about spherical bearings. Also, the arrangement shouldn't matter because either way, the axial load will be absorbed. However, I haven't thoroughly considered the bending load involved. That's what you're referring to with respect to leaking oil seals, I'm sure.

[/ QUOTE ]
Your right, I missed the taper and assumed it was spherical - my bad. Since the spindle nut contacts the inner race you would want to use the second double tapered roller bearing Rob pictured (TDO) so that you can set the endplay on the hub. I tried searching for a 207 series TDO bearing to get the width but I couldn't find it. I'll try the local bearing shop next week but I suspect that it is pretty wide, say in the 25 mm range. If there is enough hub material to machine out that bearing holds promise.
Click for TDO Image
 
For those running real double bearing hubs - what is the bearing number for those?
 
I found these bearings on the last two Sprite prototypes. They are a bit more substantial than the stock ones. You can cross this number over because it is an R&M bearing number. I think R&M doesn't exist anymore but other folks make the same bearing. R&M# LJBL35. This is what I install on all my stock hubbed cars. Also try and find "Viton" type seal too.(I think I spelled that right)
Basically the bearing has a bit less slop and more bearings.
 
[ QUOTE ]
I tried searching for a 207 series TDO bearing to get the width but I couldn't find it. I'll try the local bearing shop next week but I suspect that it is pretty wide, say in the 25 mm range. If there is enough hub material to machine out that bearing holds promise.

[/ QUOTE ]

Thanks for your help Chris, let us know what you find out!

If you can't find one with the right ID and OD, try finding ones with the right ID. I'd be interested to see if there were units with smaller OD, so we could sleeve the inside of the hub if necessary.....complexity is increasing but it still sounds doable!
 
"""""""For those running real double bearing hubs - what is the bearing number for those? '""""""

207 or 207 single or double sealed for the outer.

1-3/4XLS ( not having my notes with me now but pretty sure) inner....this is only availiable in an open bearing.

there HAS been in the past...the way past....a double brng hub that used a caged roller bearing and hardened sleeve that pressed over the seal area on the axle end. Bearings are expensive and the sleeves have to be trimmed....at 60 hard thats a grinding operation.

Short answer.....don't try to reinvent the wheel. 2 x Brng
hubs are somewhat inexpensive.
 
""""""". You can cross this number """""""
"""""""". R&M# LJBL35.""""

x's to a 207 steel cage, open no seals in deference to a 207 with a plastic cage.


""""""" Basically the bearing has a bit less slop and more bearings.""""""

IF there was a difference that would be classified as a "special" and would be VERY expensive to make in small quantities...so I dont think so....



"""""""Also try and find "Viton" type seal too"""""""

Most of the 2 x B hubs use a CR 17699 seal. this is a DOUBLE lip Nitrile seal.

The Viton counterpart is a CR 17709 BUT it has only a single lip.

this is a poor trade of as you need the double lip to keep brake dust /dirt out of the primary seal (inner lip) area.
 
Ok, don't buy the up graded bearing or viton seal. Buy the double bearing hubs they do work great....$$$$. I have a set on my really fast sprite racer.
First sprite I put the 207-M's on was in 1990. That car still has the same bearings and seals and is driven hard on the street almost daily. (they were on the 1969 fuel injected sprite prototype that ran the 12 hour Sebring and 24 Daytona race, 150 mph, and didn't fail) Spend mucho bucks if ya have to. I was just trying to offer a cheaper way for guys who are not racing. What I suggested was a way to save money and get good street durability. Heck why stop with the double bearing hubs...tell everyone they will die if they don't have coil over rear springs, relocated lower control arms, full tube frame, fuel cell, hardened axles, and all the other racer-boy stuff ya don't need for the street.
 
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