How do i keep killing rear hubs?
 

Back in December i had an OEM hub from my Kilo crack between the lockring and the cog. At the time, the consensus here and between local bike shops seemed to be that me installing a new cog, not getting it tight enough (and thus, the lockring that i did tighten to the cog was not tight enough later, after I'd ridden on it and tightened it further). I rode on it, tightening the cog, then tried to skid, and the cog backed up into the lockring, made a horrible sound, and probably cracked the hub at that point (is the theory).

I replaced that wheel with an Origin8 TrackAttak laced to Formula hub that i got thru my LBS. I greased both sets of threads, put on both cogs with a whip, tightened both lockrings, rode on both (coasting to a stop so as not to back off the cog) and retightened the lockrings with a lockring tool. I even had an LBS check my work and they pronounced them tight. I have checked them whenever i pull the wheel off (chain cleaning etc) and not found them to be loose. Meantime i have been skidding a fair bit and i weigh 250, so this is not easy on the hub, i understand.

Tuesday night i went for a ride, tried to skip not skid, and i felt a pronounced "pop" feeling thru the cranks. When i went to accelerate, the cog retightened itself. I pulled the lockring off and the threads came with it. I switched to the other side to get to work Wednesday, and when i checked that side out last night to see the state of its threads (they look good) I found another crack in the land between the lockring and hub threads. So that side's days are numbered.

What am i doing to destroy these hubs? is it just skidding being a ******? Something wrong in my mechanical approach (mind you i had the LBS "bless" my work, as well). I actually asked one of my LBSs about this and they said that maybe i'd see better results with a Phil hub, but probably not, and maybe it's just too much abuse on the equipment that is really not designed for this use (no one actually skids on a track, etc).

What do you think and what would you do to prevent this?

Get a brake.

i have a brake, i just prefer not to use it, because it's more fun not to. I will if i have to, i guess, but my question is whether i'm just abusing the equipment fundamentally in a way that a guy who weighs 130 would never do, so maybe i should knock it off.

It seems like you answered your question. If the bike is set up correctly then problem is with how it is being ridden. If you ride your bike hard then you can't expect it to last as long. This isn't quite as obvious as in the case of the fgfs'ers using track bikes but it it similar. How much do you weigh? Do you unweight the rear wheel when you skid or just muscle it?

250, and i have been trying more just pop up off the seat and lock up than bar humping, because now i'm strong enough to do that and i wasn't before. On 44x17 i probably can put a fair amount of torque into resisting, too. it's not like Formula hubs are made of cheese, but that's a lot to ask fine aluminum threads to do.

How are you doing this?

You are most likely over-torquing one part of the system and under-torquing the other.

This is incorrect and most likely the cause of your problem. Install once to correct torque and leave it alone. The lockring doesn't need to be crazy tight, it's not actually holding the cog in place. You want it to be able to tighten if the cog loosens. The cog is held in place by torque, this is true even if you are skidding. It's not the lockring, it's the cog being properly torqued.



I can't find the link for left-hand threading jam nuts but this article covers the basics.
http://www.boltscience.com/pages/twonuts.htm

Thanks, I'm straight on how jam nut systems work. I have been told as far as torque spec that i should go basically as hard as i can by one local mech(which again, being 250, i can lean on and torque the hell out of probably more than he can.) "Til the tool hurts your hand" is what another told me. Honestly, I am not making this up, and I may be getting bad advice.

I'm totally willing to believe i am gorilla-ing the lockring, but i don't know how i'd check torque with a stamped-steel lockring tool like my Park. I have used lockrings in engines before with a special socket that can fit a torque wrench, which i have, but not a socket that will fit a lockring.

So recommend learning to use brakes, drop 50-60 pounds, and don't voluntarily execute destructive component testing unless you can do it privately and can afford to pay the bills.

When folks bring in broken bikes for repair which have been abused, we normally turn them away as we don't want them as customers and secondly we don't want the hassle of trying to solve the problems they self-inflict.

Your mechanic(s) are giving you bad advice.

"As hard as you can" = "I don't know what I'm talking about"

To properly measure the torque you need a custom tool, not hard to make on your own. I've only ever seen one, but it's not really necessary. Just use the basic concepts, get it "tight" and then add 0.25, 0.5 or whatever turns to snug it up. Now, you want to get the cog really tight, but still not as tight as possible.

This is a very promising business plan.

Probably wouldn't hurt to google for "how to use a torque wrench" and proceed from there. Having a torque wrench is definately not the same as knowing what to do with it. Make sure you find out the specs for the jam nut and hub you are abusing and whether the spec is for lubed or none lubed. Also be more selective on how much of the advice from the folks at your current LBS you listen too. Sounds a bit ham-fisted type.

1. Dropped 30 already, working on it.
2. Willing to recognize this is my fault. Not asking for charity, just trying to understand here.
3. Have a nice day.

What are you talking about?

Having a torque wrench wouldn't help here unless he also had a custom socket/head to mate with the cog or lockring. It's also not necessary, he just needs to tighten the lockring less, the cog a little more and don't check the tightness. It's better to remove and re-torque if you you're worried about the system loosening up.

[QUOTE=ksisler;15684288]Probably wouldn't hurt to google for "how to use a torque wrench" and proceed from there. QUOTE]

Having built engines, i think i'm OK on how to use a torque wrench, honestly. My point was, there are no pin-spanner type sockets that *i* know of that i could fit to a torque wrench; the only lockring tools i've ever seen are straight up wrenches. Point me at what will fit a craftsman torque wrench and i'm there.

It can be and is if one does the calculations based on having a real business plan and on decades of experience. The answer to the formula is that these customers always cost far more in time/effort/frustration than they ever generate in sales or profits. They also seem to be completely resistant and/or incapable of learning anything so it is doubly difficult to work with them.

/K

You really cannot tighten a fixed cog properly by hand or by rotafixing... you do of course torque the hell out of it when you install it but after that first ride around the block it will be tighter than it was when you started riding as the torque you can apply by pedalling far exceeds that which you can apply with your meager arms.

This is when you go back and check the lock ring which should have also been installed with a high degree of torque and bet it will tighten up just a little more. After that you should be golden... make sure you lube the threads to prevent corrosion and to allow the cog and lockring to seat.

I am just a little guy... after installing rear wheels and torquing the nuts down to spec I know a lot of bigger guys who cannot undo them. The rear cog has an even higher torque spec and anyone who has tried to remove a well ridden in cog / lockring knows how tight they can be.

Biggest issue I see with fg bikes that come into the shop is that the initial installation of the cog and lockring was done improperly... in many cases the bikes came this way from the shop that sold them because the mechs do not understand the principles of proper torque for fixed drives.

Whatever you do, I suggest sticking with the lower cost hubs, at least until you can figure out what the problem is. I'd hate to hear of you continuing to have the same problem on Phils, or Dura Ace hubs. Would really hurt the wallet.

If someone comes into a car dealer and says he burned his tires out again and wants a new car, you give him a new ****ing car. You don't turn him away to another shop. If your shop has their nose that far up in the air they shouldn't be doing business, they should be eating grey poupon by the mouthful.

You got it wrong. It's more like dude came in with his car complaining about burned out tires again, and the shop turns him away because all he wants are new tires INSTEAD of the new car. ksisler's plan is to cater to the new car buyers instead. Also, mouthfuls of grey poupon is so gross I don't even.

I'm leaning heavily toward "I'm overtorquing the F out of the lockring," because that would explain how i'm stripping threads/cracking hubs nicely. I'm sure the cog is staying tight otherwise. As you point out, it should be a self-tightening/equilibrium maintaining system (cog backs off, tends to tighten lockring).

OP; All's cool here and awesome on the -30 to date. My original thought was that breakage = downtime = time not available to ride and enjoy (and add 'to lose more'); thus must avoid preventable breakage, etc.

Oh, and I was in real grump this morn. Am over that now...see smiley here -> :)

This. Emphasis on using your legs to tighten the cog, then retightening the lock ring.

Maybe this - http://www.citygrounds.com/sunlite/s...over-head-2806

This kind of post is what keeps me coming back here. Glad to see the sunshines are back :)

To the OP. I've been riding track bikes with fixed cogs for over 40 years on the road and have learned some things about properly tightening a track cog so that it won't unscrew when you backpedal. The best way I've found is to screw on the cog by hand, install the wheel in the bike, brace the front wheel against a wall and stand on the the front facing pedal with all your weight. The more you weigh, the tighter it will get, such that it is physically impossible to overcome the tightening torque no matter how hard you backpedal. After that, remove the wheel and install the lock ring snug tight, nothing more.