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      10-20-2020, 02:07 PM   #1
Eric SS
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Will a CBC potentially mitigate interference if your hub does slip with it on?

I realize that the CBC is not the ultimate solution to the inherent design flaw of our crank snout, and that it only might help mitigate an issue. My question is if the CBC might help mitigate how MUCH the hub spins if it does slip before the friction catches the hub again. It seems like it would stop the spinning quicker since the bolt isn't backing out and therefore has more potential to mitigate valve/piston interference. Thoughts? I know the SCH doesn't happen as often as it probably seems to on the board but I'm still curious of the answer. Thanks.
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      10-20-2020, 04:32 PM   #2
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That's the point of the CBC. If the hub bolt starts to back out it hits the walls of the CBC like a socket wrench. Since the hub bolts hold it in place now you need to slip all 8 of those to get movement (not likely).

The only subsequent OEMhub+CBC issue would be to overpower the friction washer, somewhere in the very high TQ range (E85+HybridTurbos+Meth). Most custom tuners watch out for this, and also rods bending.
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      10-20-2020, 04:49 PM   #3
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Quote:
Originally Posted by TopJimmy View Post
That's the point of the CBC. If the hub bolt starts to back out it hits the walls of the CBC like a socket wrench. Since the hub bolts hold it in place now you need to slip all 8 of those to get movement (not likely).

The only subsequent OEMhub+CBC issue would be to overpower the friction washer, somewhere in the very high TQ range (E85+HybridTurbos+Meth). Most custom tuners watch out for this, and also rods bending.
Yeah, that's my question. If you are going to slip the friction washer, does the fact that you have a CBC on the car keep it from slipping as much so that you are less likely to slap the valves with the pistons. It sure seems like it would slip less if it slips with the CBC. The fact that the bolt won't move in relation to the crank makes me think that if it does slip, the friction disk will "catch" quicker. I wonder how many degrees out the timing can be until interference happens.
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      10-20-2020, 05:13 PM   #4
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Your answer depends on the situation... Suppose you were doing a drag launch and the washer slips, it's likely to slip a little (exactly how much???) since your clutch(es) take some load. Suppose you do a bad downshift or a mis-shift with rev match off, then more slippage is likely because you torqued the whole valvetrain with a huge RPM difference extra fast. Does that help?

If you're doing all the hub work why not pay the extra $1K for the 4-pin part? It's only 1 extra hour to drill the dimples.
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      10-20-2020, 05:59 PM   #5
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I wonder what is the threshold until the friction washer slips.

Quote:
Originally Posted by TopJimmy View Post
Your answer depends on the situation... Suppose you were doing a drag launch and the washer slips, it's likely to slip a little (exactly how much???) since your clutch(es) take some load. Suppose you do a bad downshift or a mis-shift with rev match off, then more slippage is likely because you torqued the whole valvetrain with a huge RPM difference extra fast. Does that help?

If you're doing all the hub work why not pay the extra $1K for the 4-pin part? It's only 1 extra hour to drill the dimples.
What is the 4 pin part?
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      10-20-2020, 06:36 PM   #6
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Quote:
Originally Posted by TopJimmy View Post
The only subsequent OEMhub+CBC issue would be to overpower the friction washer, somewhere in the very high TQ range (E85+HybridTurbos+Meth).
I completely agree. What I've always found interesting though is how sporadic spun hubs appear to be (modded, stock, backing out of a drive way) and thus far no one can fully explain the root cause.

Your mention of overpowering the friction washer is absolute valid too, much along the same lines though no one can tell us what the friction coefficient is and at what power level it would be in danger of exceeding its tolerance.

I personally feel that if the crank bolt is torqued correctly and held there via CBC, the crank hub would be fine until the friction coefficient of the disks were overwhelmed ; it would also be easier to determine cause and effect. The problem is, once the car has been driven there's no reliable method to really check if the bolt is still within factory specs prior to installing the CBC.

Without that, it's essentially a toss of the dice and take your chances that the bolt never moved before slapping on the CBC, or dole out 3k plus for a fix that may or may not be required.

Last edited by MJ6; 10-20-2020 at 07:33 PM..
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      10-20-2020, 06:45 PM   #7
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Quote:
Originally Posted by MisterF80M3 View Post
What is the 4 pin part?
I mean the SSR 4-pin keyed hub solution, which is the updated version of the MaxPSI 2-pin solution.
https://www.kiesmotorsports.com/prod...30768992944243
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      10-20-2020, 06:57 PM   #8
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Answered in the other thread, but for continuity...

It's not something we can put a hard answer to. I can answer anecdotally, that of the crank hub spins I've seen, the majority of them got by with a re-time. The number of CBC only slipped hubs I've seen is much less, but of that smaller subset all of them were able to get by with just a re-time and proper hub install. No way of knowing if that's just raw data or more of a trend, just sharing what I've observed. I would not jump to a conclusion on that data, not trying to fearmonger, just don't want someone on the fence thinking "eh Chris said CBC only slips would just be a re-time". Can't say that. Just the few CBC only slips I've seen thus far were able to be saved simply.

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      10-20-2020, 07:03 PM   #9
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Quote:
Originally Posted by MJ6 View Post
What I've always found interesting though is how sporadic spun hubs appear to be (modded, stock, backing out of a drive way) and thus far no one can fully explain the root cause.
When Kies did my hub it was prevention at my request, nothing spun. Upon examining the washers (there are two) there were 5 dimple marks from little friction bumps on the sprockets. We had trouble trying to get the valve sprocket off the hub, but when it "popped loose" I noticed the massive crush of the bolt actually "sticks" (felt like little spot welds) the washer to the dimples. I think this is why the failure from a loosened bolt seems to be random...until those dimples un-stick.
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      10-20-2020, 07:31 PM   #10
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4K for full solution or -500 for a CBC. I gather if you are under stage 2 a CBC is the way to go.
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      10-20-2020, 11:16 PM   #11
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Quote:
Originally Posted by TopJimmy View Post
I mean the SSR 4-pin keyed hub solution, which is the updated version of the MaxPSI 2-pin solution.
https://www.kiesmotorsports.com/prod...30768992944243
My local shop charges $2000 in labor for the SSR 4pin + $1000 for the part = $3000 for the crank hub upgrade.
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      10-21-2020, 06:28 PM   #12
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Quote:
Originally Posted by MJ6 View Post
... and thus far no one can fully explain the root cause.
....
This right here is the worst part of the whole thing! Between this and the overall really low numbers it's just a guess how effective any fix is.

Is the problem purely that the hub bolt is backing off? If so, then a CBC is all the fix you need.

Is the problem that the hub can slip even with the bolt at the correct torque? If so, the CBC won't help at all and only one of the full pinned or spline-lock fixes would help.

Is it both? Then you can eliminate one cause for a reasonable cost or both for a pretty good chunk of change. And then what percentage of each of these already rare problems is due to each cause?

Is it really only a bigger problem with modified cars or is it based on how the car is driven and that just happens to overlap with the car being modified? Or maybe it appears to mostly be modified cars because we're surveying people on a forum where a huge percentage is modified.

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      10-21-2020, 08:55 PM   #13
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Quote:
Originally Posted by Tangent View Post

Is it really only a bigger problem with modified cars or is it based on how the car is driven and that just happens to overlap with the car being modified? Or maybe it appears to mostly be modified cars because we're surveying people on a forum where a huge percentage is modified.

My purely subjective opinion is that driving style has a lot to do with it but I see both sides of the coin.

I follow some owners on YouTube. I see videos of them beating on their cars amd think boy I’d never treat my cars like this. then I see more recent videos about how their ch failed. I also see people saying they don’t drive hard at all and fail on stage one bm3.

At the end of the day. Look. These cars have a known fail point that seems to be both power related and driving style related. I definitely woildnt abuse This M.
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      10-21-2020, 09:18 PM   #14
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Quote:
Originally Posted by matty088 View Post
My purely subjective opinion is that driving style has a lot to do with it but I see both sides of the coin.

I follow some owners on YouTube. I see videos of them beating on their cars amd think boy I’d never treat my cars like this. then I see more recent videos about how their ch failed. I also see people saying they don’t drive hard at all and fail on stage one bm3.

At the end of the day. Look. These cars have a known fail point that seems to be both power related and driving style related. I definitely woildnt abuse This M.
My homie has a F80 stage 2 tune with FBO with a CBC. He abuses the living crap out of his car. He floors it every opportunity he gets. Brings it to the track and drag strip and his crank hub is still doing fine 3 years later.
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      10-21-2020, 09:25 PM   #15
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@Tangent those are a lot of questions. Let's just put it this way, there are two separate issues.

The hub bolt can come loose, likely by repeated torquing back and forth, which can either immediately slip or hold on a little bit and slip later (seeming random). The hub bolt loosening can happen to an aftermarket "fixed hub" just like on an OEM hub, and the CBC corrects this issue on both.

The other issue...even if the hub bolt is torqued right (held with a CBC or not) an excessive force can overcome the crush-fit of an OEM hub's friction washers and slip a sprocket. A fixed-hub corrects this with pins/splines and keyways which secures the hub and sprockets to the crank. We don't know where this breaking point is because there are so few documented failures with CBC, but likely starting around 600TQ (<<not sure!).

Since most of us spend 50K on a car and then to pay for DPs, CPs, TMIC, intake, exhaust...doesn't it make sense to pay the 4K and get the hub out of the way (and off our mind)? Ever since I did my hub now I can drive my car like a true race car without worry. Last night a tuned Caddy CTS-V found out that a 6-speed 6-cyl can take down an auto trans 8-cyl, then he got me in round 2. I say we tie.
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      10-22-2020, 06:24 PM   #16
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Would be interesting to compare how much torque it takes to slip the hub on a OEM friction disc application vs a pinned/splined hub.
Both torqued correctly, and both under torqued to simulate a backed out bolt.

Also, if the main issue is the bolt coming loose, why does it not happen with the upgraded hubs? Or is basically everybody also using a capture?
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      10-22-2020, 06:29 PM   #17
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Quote:
Originally Posted by Nisse Järnet View Post
Would be interesting to compare how much torque it takes to slip the hub on a OEM friction disc application vs a pinned/splined hub.
Both torqued correctly, and both under torqued to simulate a backed out bolt.

Also, if the main issue is the bolt coming loose, why does it not happen with the upgraded hubs? Or is basically everybody also using a capture?
It does happen. There is a thread on MaximumPSI crank hubs that were not drilled correctly. Multiple people spun their hubs because the bolt backed out.
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      10-22-2020, 11:14 PM   #18
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Quote:
Originally Posted by Nisse Järnet View Post
Would be interesting to compare how much torque it takes to slip the hub on a OEM friction disc application vs a pinned/splined hub.
Both torqued correctly, and both under torqued to simulate a backed out bolt.

Also, if the main issue is the bolt coming loose, why does it not happen with the upgraded hubs? Or is basically everybody also using a capture?
The aftermarket hub solutions only resolve the over-torque-the-washer situation. Bolts can still back out depending on abuse level, but it's more likely that the mechanic does a proper job installing after a failure happened.

As for using a capture or not...I can't see any reason not to add a $100 part when doing a couple-grand job.
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      10-23-2020, 01:29 PM   #19
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Link to thread?

Quote:
Originally Posted by MisterF80M3 View Post
It does happen. There is a thread on MaximumPSI crank hubs that were not drilled correctly. Multiple people spun their hubs because the bolt backed out.
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      10-24-2020, 03:11 AM   #20
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There are still no documented crank hub slips with using just a CBC
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      10-24-2020, 08:22 AM   #21
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Quote:
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There are still no documented crank hub slips with using just a CBC
A guy did spin his CBC'd stock hub on a botched money shift. A sudden rev to 9K will overtorque the washer. It's not the "too much power" slip that we're looking to examine, but it happened.
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      10-24-2020, 02:48 PM   #22
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My car has now seen 58-60+ 3+k rpm launch controls on prep and about three times that in street launches within the last year or so with a CBC.

Hasn't skipped a beat. The trans is what is seemingly the weak point when it comes to drag racing shocks, wear and load on my f82.
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