Topic: Mea Culpa (sort of) re: chain adjuster bolts

[MCRider]

In various threads I've taken the position that the chain adjuster bolts are for adjusting the chain. The axle nut carries the full load of holding the wheel where it belongs.

I've heard it from a respected source that the bolts are an effective failsafe and should always be there, tight and secure.  The CB750 bolt is a hardened piece after all and Honda probably did this for a reason. It has a point also which serves to anchor it in the bracket.

I still think that the the proper tightness of the axle nut cannot be understated (CB750 = 70-75ft lbs.) And reliance on the bolts for anything more than a failsafe is misguided, IMO.

But armed with this contra opinion I will refrain from presenting my position as being an absolute.

[Don R]

That's an open minded and well stated point. I agree the axle nut does the majority of the work. The adjusters work in harmony to achieve and maintain the setting. imho.

[Tews19]

Interesting... Any recommendations on a good, reasonable price torque wrench?

[iron_worker]

I was under the impression that the pinch bolts did most of the holding and the adjusting bolts were just for positioning and to give the ability to equally adjust the position of the axle on each side.

Would there really be need for a cotter pin on the axle nut if it was supposed to be tightened down to 70lb*ft? I assumed it would be more like a taper wheel bearing on old spindle set up.

IW

[MCRider]

Interesting... Any recommendations on a good, reasonable price torque wrench?

That's a problem in a few respects. Most of us own wrenches in inch lbs. But 75ft lbs = 900 inch lbs which goes off most scales.  Plus, many of us are on trips when the chain needs to be adjusted, and don't carry around a torque wrench.

The tool kit wrench is not very long even with the extension. But assume it is a workable 6". Then you would need to apply 150lbs force to get there. So, I stand on the wrench (being about 160lbs) and let my weight settle on it.

If you had a real (non-torque) wrench in the shop of 12" or so, then half your body weight would get you there.

Having done a few with a real torque wrench, i am confident that i am pretty darn close with my shady tree method. i would suggest borrowing a real torque wrench and practicing.

[MCRider]

I was under the impression that the pinch bolts did most of the holding and the adjusting bolts were just for positioning and to give the ability to equally adjust the position of the axle on each side.

Would there really be need for a cotter pin on the axle nut if it was supposed to be tightened down to 70lb*ft? I assumed it would be more like a taper wheel bearing on old spindle set up.

IW

If you mean by pinch bolts, the axle nut, then I agree with paragraph 1.

As to Para 2, my opinion is absolutely not like a taper trailer bearing. Our bearings are not like that at all. If you visualize the stack of spacers, and the internal races of the non-taper bearings, you can see that no matter how tight the axle is you cannot pinch the bearings or overtighten them. The torque on the axle nut per the various manuals is 70 to 75ft lbs at the high end (55 or so at the low end, which i would stay away from).

The cotter pin serves 2 purposes in my mind. It is never put in place until the nut is properly torqued, serving as a visual that all is well. Also, it prevents someone from monkeying with the nut, or at least deters them from it.

On the old taper wheel bearing set up like on a trailer, you snug the nut then back off to where the cotter pin can go in.  With our bikes you tighten it as tight as it should be, then go to the NEXT notch where the pin will fit in. IMO.

If its properly torqued its hard to think it will loosen, but there's always that probability i suppose.

http://www.salocal.com/sohc/tech/torquetable.htm
Scroll down to the "Tear wheel axle nut" (misspelled).

In my youth, at the Honda Shops,  we used to sell a lot of the chain adjuster bolts for dirt bikes. Bent like pretzels. While they swore the axle nut was tight I always wondered, and there was no way to prove it one way or t'other. So, sell them a bolt. So, I know both sides of the argument. But like in TEWS post, who's got a torque wrench that goes that high, and who uses it?

[Tews19]

Interesting... Any recommendations on a good, reasonable price torque wrench?

That's a problem in a few respects. Most of us own wrenches in inch lbs. But 75ft lbs = 900 inch lbs which goes off most scales.  Plus, many of us are on trips when the chain needs to be adjusted, and don't carry around a torque wrench.

The tool kit wrench is not very long even with the extension. But assume it is a workable 6". Then you would need to apply 150lbs force to get there. So, I stand on the wrench (being about 160lbs) and let my weight settle on it.

If you had a real (non-torque) wrench in the shop of 12" or so, then half your body weight would get you there.

Having done a few with a real torque wrench, i am confident that i am pretty darn close with my shady tree method. i would suggest borrowing a real torque wrench and practicing.

I weigh 150... So stand on to tighten

[iron_worker]

The pinch bolt I was referring to is #19 in this diagram:

http://www.cmsnl.com/honda-cb750-four-k4-usa_model482/partslist/F++19.html#results

It seems to lock the slider in place once you've used the adjuster bolts to get the correct axles placement. #21 in this diagram:

http://www.cmsnl.com/honda-cb750-four-k4-usa_model482/partslist/F++17.html#results


Anyway, I have always left my axle bolt (#23 in the last diagram) fairly loose. Certainly not 50+ ft*lb but perhaps I shouldn't have been. I always thought the pinch bolts were doing most of the "holding." Maybe I'm lucky I haven't torn my wheel off or something. ha

IW

[MCRider]

The pinch bolt I was referring to is #19 in this diagram:

http://www.cmsnl.com/honda-cb750-four-k4-usa_model482/partslist/F++19.html#results

It seems to lock the slider in place once you've used the adjuster bolts to get the correct axles placement. #21 in this diagram:

http://www.cmsnl.com/honda-cb750-four-k4-usa_model482/partslist/F++17.html#results


Anyway, I have always left my axle bolt (#23 in the last diagram) fairly loose. Certainly not 50+ ft*lb but perhaps I shouldn't have been. I always thought the pinch bolts were doing most of the "holding." Maybe I'm lucky I haven't torn my wheel off or something. ha

IW

Oops on you. Bear with me as the are the misconceptions I've run across in this issue. The pinch bolts you reference are simply the bolts to hold the stoppers in place. They can't pinch anything as the stoppers dictate. The stoppers are not sliders, but are the push points for the adjuster bolts #21. keep in mind this whole design is made for the CB750. There would be no need for the stoppers except the only way to get the wheel out with the 4-4 pipes, is to have a removable end piece to the swingarm. Otherwise, the end of the swingarm would be a closed loop as it is on most bikes.

Yes, you have been very lucky. I ran across another person on the forum who said they only snugged the axle nut as they were afraid of binding the bearings. YIKES! The bearings are a very passive design. The axle nut clamps down on the inner race of the 3 bearings, the inner race which acts as a spacer, that's all. It is stationary, the balls and outer race rotate around it.

Please tighten it at least to 55ft lbs, and more if you can muster.

[DJ_AX]

When it comes to anything to do with safety redundancy rules.

In traditional rock climbing, any one piece of gear can and will save you... however it is standard practice to have at least three anchors... because as we all know... #$%* happens.

[iron_worker]

Well don't I feel silly now.

[CrankyOldGuy]

Thanks for the info on the torque value.  My goal is to learn something new each day.

In my youth, before computers and manuals, I use to put all my effort into tightening the bolt with a 12" wrench. I had a heck of a time getting that last little bit of movement so the cotter-pin would fit  . I bet I was well over the 75 ft-lb value   .  I never had a problem with the rear wheel not spinning easily    Btw did the little Honda manual that came with the motorcycle have torque values?, mine has long disappeared.

Harry O.

[vames]

On the 400f, the axle bolt (and the chain, in a way, I guess) is really all you have to hold the wheel on. The axle slips into open-ended slots in the back of the swingarm. The chain adjusters butt into pieces that close off the slots, but are held in place only by the pressure from the adjusters themselves. If the chain were to break and the axle bolt somehow loosen, the whole wheel would just slip off the back of the bike.

I definitely tighten the eff out of that axle bolt.

[seanbarney41]

Once, on my first bike, a cb350 twin, I forgot to tighten the axle nut and replace the cotter pin and went for a ride.  After about 5 miles I luckily heard the axle nut and/or washer bouncing off down the road behind me and took a peek back at the axle... ...it had slid out a good inch and a half and my blood ran cold.  I pulled over quickly.  Somehow everything had held together.  I fashioned a crude cotter pin from part of my key chain and rode home about 10mph on the shoulder with my eye on the back axle the whole time...

[HondaMan]

Once, on my first bike, a cb350 twin, I forgot to tighten the axle nut and replace the cotter pin and went for a ride.  After about 5 miles I luckily heard the axle nut and/or washer bouncing off down the road behind me and took a peek back at the axle... ...it had slid out a good inch and a half and my blood ran cold.  I pulled over quickly.  Somehow everything had held together.  I fashioned a crude cotter pin from part of my key chain and rode home about 10mph on the shoulder with my eye on the back axle the whole time...

I once wasn't quite so lucky: I hopped on a Yammie RD350 that the customer complained "had a slipping clutch when I get on it". So, I went out an got on it: apparently considerably more than he did. The rear axle nut was maybe hand-tight (sans wrench) and the cotter key installed. The little 6mm adjuster bolts folded all the way up and broke off (heard them go) and the bike and I went scrambling into the weeds at redline 2nd gear. Tore up my jacket and elbow in the crash.

I was supposed to be the professional, or I might have kicked his butt when I got back to the shop, pushing that Hammer down the road sideways...

[camelman]

So, what's the diameter of that bolt?  0.6" or so?  Add to that a machine thread and a healthy dose of torque, and you have an immense clamping force.  Clamping force is a tough analysis with the best of equipment, but the rear axle setup on our bikes probably delivers over 5,000 pounds of clamping force at 55 ft-lbs.  Take 50% of that as a conservative value for coefficient of friction (published values are 0.7-0.8 ) and you have a slip resistance of at least 2500 pounds.  If you tighten to 75 ft-lbs, then that slip resistance is more like 3750 pounds.  Again... on the conservative side.  Of course this varies depending on the cleanliness of the clamped surfaces, the smoothness of the surfaces (smoother equals greater resistance to slipping), and the torque exerted on the axle nut.  In short, unless you are a total sissy, you should be able to put at least 1000 pounds of slip resistance onto that bolted flange.

Our bikes don't accelerate or brake with anywhere near 1 G of force.  There are instances where we might get jerk load through the chain, or due to bumps, but that load is still traction limited.  So, considering a fully loaded CB750 should be under 1000 pounds, the likelihood of the rear axle slipping with only 25 ft-lbs of torque on the axle nut is pretty slim.  And you would have to be either negligent or a total sissy to not be able to apply 25 ft-lbs of force onto that nut.

This is a very standard and common lesson taught during mechanical design.  FYI, your car wheel is likely clamped to the steering knuckle assembly with 35,000 (or so) pounds of force.  It won't slip even if the slightest person were to tighten the wheel nuts.  Neither should your rear axle slip.

Regards,
Camelman

[seanbarney41]

So, what's the diameter of that bolt?  0.6" or so?  Add to that a machine thread and a healthy dose of torque, and you have an immense clamping force.  Clamping force is a tough analysis with the best of equipment, but the rear axle setup on our bikes probably delivers over 5,000 pounds of clamping force at 55 ft-lbs.  Take 50% of that as a conservative value for coefficient of friction (published values are 0.7-0.8 ) and you have a slip resistance of at least 2500 pounds.  If you tighten to 75 ft-lbs, then that slip resistance is more like 3750 pounds.  Again... on the conservative side.  Of course this varies depending on the cleanliness of the clamped surfaces, the smoothness of the surfaces (smoother equals greater resistance to slipping), and the torque exerted on the axle nut.  In short, unless you are a total sissy, you should be able to put at least 1000 pounds of slip resistance onto that bolted flange.

Our bikes don't accelerate or brake with anywhere near 1 G of force.  There are instances where we might get jerk load through the chain, or due to bumps, but that load is still traction limited.  So, considering a fully loaded CB750 should be under 1000 pounds, the likelihood of the rear axle slipping with only 25 ft-lbs of torque on the axle nut is pretty slim.  And you would have to be either negligent or a total sissy to not be able to apply 25 ft-lbs of force onto that nut.

This is a very standard and common lesson taught during mechanical design.  FYI, your car wheel is likely clamped to the steering knuckle assembly with 35,000 (or so) pounds of force.  It won't slip even if the slightest person were to tighten the wheel nuts.  Neither should your rear axle slip.

Regards,
Camelman

ok whatever the math works to, I got lucky in my last story with a bike...1991 Dodge Van?, not so lucky...when the back wheel fell off in the dying remnants of a hurricane, scattering brake parts all down the rain soaked highway, stranding me and the rest of my band in Stampford Connecticutt...I swear to god it took me three days to find the necessary parts... I bought them off of Click and Clack...

[Tews19]

So, what's the diameter of that bolt?  0.6" or so?  Add to that a machine thread and a healthy dose of torque, and you have an immense clamping force.  Clamping force is a tough analysis with the best of equipment, but the rear axle setup on our bikes probably delivers over 5,000 pounds of clamping force at 55 ft-lbs.  Take 50% of that as a conservative value for coefficient of friction (published values are 0.7-0.8 ) and you have a slip resistance of at least 2500 pounds.  If you tighten to 75 ft-lbs, then that slip resistance is more like 3750 pounds.  Again... on the conservative side.  Of course this varies depending on the cleanliness of the clamped surfaces, the smoothness of the surfaces (smoother equals greater resistance to slipping), and the torque exerted on the axle nut.  In short, unless you are a total sissy, you should be able to put at least 1000 pounds of slip resistance onto that bolted flange.

Our bikes don't accelerate or brake with anywhere near 1 G of force.  There are instances where we might get jerk load through the chain, or due to bumps, but that load is still traction limited.  So, considering a fully loaded CB750 should be under 1000 pounds, the likelihood of the rear axle slipping with only 25 ft-lbs of torque on the axle nut is pretty slim.  And you would have to be either negligent or a total sissy to not be able to apply 25 ft-lbs of force onto that nut.

This is a very standard and common lesson taught during mechanical design.  FYI, your car wheel is likely clamped to the steering knuckle assembly with 35,000 (or so) pounds of force.  It won't slip even if the slightest person were to tighten the wheel nuts.  Neither should your rear axle slip.

Regards,
Camelman

ok whatever the math works to, I got lucky in my last story with a bike...1991 Dodge Van?, not so lucky...when the back wheel fell off in the dying remnants of a hurricane, scattering brake parts all down the rain soaked highway, stranding me and the rest of my band in Stampford Connecticutt...I swear to god it took me three days to find the necessary parts... I bought them off of Click and Clack...

Back in my Fast and Furious days, I bought some low pro 17" rims for my Honda Accord. After swapping out to a set of tokico's and H and R springs my buddy and I were driving back from the shop on base. We both heard click click click clunk and the car felt wobbly.

We bot get out of the and ask, "did you tighten the lugs?" at the same time.... Both starting laughing.. I ended up walking to the tire store on base to borrow the 4 way.

[camelman]

Oh man, lug nuts. We've all probably forgotten to tighten them at some point. I had the pleasure of four of them shearing off one wheel in a car I was a passenger in. We limped to the nearest repair center on the remaining lug and bought replacements. That could have been bad!

I'm always surprised at the clamping forces exerted by fasteners...when they're tightened.

[MCRider]

So, what's the diameter of that bolt?  0.6" or so?  Add to that a machine thread and a healthy dose of torque, and you have an immense clamping force.  Clamping force is a tough analysis with the best of equipment, but the rear axle setup on our bikes probably delivers over 5,000 pounds of clamping force at 55 ft-lbs.  Take 50% of that as a conservative value for coefficient of friction (published values are 0.7-0.8 ) and you have a slip resistance of at least 2500 pounds.  If you tighten to 75 ft-lbs, then that slip resistance is more like 3750 pounds.  Again... on the conservative side.  Of course this varies depending on the cleanliness of the clamped surfaces, the smoothness of the surfaces (smoother equals greater resistance to slipping), and the torque exerted on the axle nut.  In short, unless you are a total sissy, you should be able to put at least 1000 pounds of slip resistance onto that bolted flange.

Our bikes don't accelerate or brake with anywhere near 1 G of force.  There are instances where we might get jerk load through the chain, or due to bumps, but that load is still traction limited.  So, considering a fully loaded CB750 should be under 1000 pounds, the likelihood of the rear axle slipping with only 25 ft-lbs of torque on the axle nut is pretty slim.  And you would have to be either negligent or a total sissy to not be able to apply 25 ft-lbs of force onto that nut.

This is a very standard and common lesson taught during mechanical design.  FYI, your car wheel is likely clamped to the steering knuckle assembly with 35,000 (or so) pounds of force.  It won't slip even if the slightest person were to tighten the wheel nuts.  Neither should your rear axle slip.

Regards,
Camelman

Wow. appreciate the math, makes sense.