Is the compression cap important?

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12/26/2017 4:41 PM

I am missing the cap, took my bike for a ride just around the neighbor hood and everything seemed fine. I can't find the cap at all, and I'm planning on hitting the park. Is it ok without it? I got the pinchbolts on pretty tight.

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12/26/2017 4:51 PM

what exactly do you mean by compression cap? does your bike have suspension?

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12/26/2017 4:54 PM

sorry I read that wrong.idk you should be good

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12/26/2017 5:05 PM

As long as you have the bearings sufficiently preloaded, it'll be fine. I can't quite understand why you'd have your compression bolt off your bike for long enough to lose it though.

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12/26/2017 5:37 PM

As long as the stem pinch bolts are tight and the headset isn't loose, it should be fine... but the second you need to tighten your headset or move your stem (if they slipped or something), you're shit out of luck. find it or buy a new one asap so you have it

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12/26/2017 7:21 PM

Get a new one asap. Shits important. Idk how you lost it in the first place...

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12/26/2017 9:30 PM

First thing I would do is ignore any comments saying it's okay to ride like that..

That compression bolt is the only thing that's going to keep your stem tied down to your forks. It may be fine for pedaling around and steering, but you're going to be highly disappointed when you get a serious injury due to negligence & your handle bars flying off mid trick.

I've had a handful of friends try riding without one over the years, and it never fails to watch them lose their headset bearings or eat shit shortly after.

Also, I've ripped a stem off my forks with a compression bolt. Pulled the threads clean off the bolt. So, yes, I would say they are incredibly important.

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12/26/2017 9:56 PM

HardBMX_Tim wrote:

First thing I would do is ignore any comments saying it's okay to ride like that..

That compression bolt is the only thing ...more

I think you and your friends need to tighten your pinch bolts more or have more steerer tube in the stem, ripping a stem off your fork shouldn't happen if the bolts are properly tightened... Not to mention if you're doing something that manages to rip your stem clean off of your fork like that, I don't think a thin aluminum cap is going to do much to prevent that, as demonstrated by your stem ripping your compression out.

I know a guy who hasn't used a compression bolt for the last 10 years, not sure why. But he's never had issues with his stem ripping clean off his fork. Sometimes it moves when he eats shit or throws his bike, but never pulled right off.

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12/26/2017 10:37 PM
Edited Date/Time: 12/26/2017 10:41 PM

HardBMX_Tim wrote:

First thing I would do is ignore any comments saying it's okay to ride like that..

That compression bolt is the only thing ...more

sundaybmxRR wrote:

I think you and your friends need to tighten your pinch bolts more or have more steerer tube in the stem, ripping a stem off ...more

Since you mention it, the stem I was running at the time of my incident was actually almost pinched completely. So, on the contrary, I know it was likely tighter than necessary. My uncut Odyssey steerer tube was 3/4 of the way into the stem, which is why the bolt stripped, there was only 4 threads making contact (substantially more than running no bolt at all.)

Also, it happened while attempting to learn fly-out 540s. I was yanking super hard on the take-off, and after probably an hour of trying them, my bars came right off.. lol
Photo

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12/26/2017 11:01 PM

HardBMX_Tim wrote:

First thing I would do is ignore any comments saying it's okay to ride like that..

That compression bolt is the only thing ...more

sundaybmxRR wrote:

I think you and your friends need to tighten your pinch bolts more or have more steerer tube in the stem, ripping a stem off ...more

HardBMX_Tim wrote:

Since you mention it, the stem I was running at the time of my incident was actually almost pinched completely. So, on the ...more

That's a snapped steerer, nothing to do with the compression bolt. Probably more to do with overtightening your stem.

Pinch bolts hold the stem on, compression bolts pre load your headset.

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12/26/2017 11:21 PM

sundaybmxRR wrote:

I think you and your friends need to tighten your pinch bolts more or have more steerer tube in the stem, ripping a stem off ...more

HardBMX_Tim wrote:

Since you mention it, the stem I was running at the time of my incident was actually almost pinched completely. So, on the ...more

grumpySteve wrote:

That's a snapped steerer, nothing to do with the compression bolt. Probably more to do with overtightening your stem.

Pinch ...more

No it is not a snapped steerer tube. The bolt pulled right out cause it barely reached the fork threads (I think the first thread or two were messed up anyways,) and the stem came off with it. I bought a new compression bolt , reassembled it and rode them on 3 other builds afterwards with no problems.

Photo
Photo
Photo

Also it's likely that it started stripping before the attempt that sealed the deal. I was raging trying to learn them and wasn't paying much attention to how my bike was holding up. It could have been loose and crying for help and I wouldn't have noticed. Headphones in and my focus was on the ramp and hucking that trick.grin

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12/26/2017 11:57 PM

Anyways, im not here to argue about it. I know what I've done to my own bike and I know what I've seen happen in person.

I guess some people get away with riding without it, but imo it's there for a reason, you might aswell be safe and use it. I'm sure Mafia would be saving weight and cutting manufacturing costs by not threading forks by now if it wasn't necessary.grin

Also I find it ironic to preach the safety of helmets in some threads, and then tell people it's safe to ditch a whole piece of the bike in others.dizzy

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12/27/2017 12:28 AM

Tim,
Your forks/stem must have come apart from the cinch bolts not clamping the stem to the fork, most likely pulling the compression bolt with it.

To say they came off because of the compression bolt would imply two separate things happened at the same exact time.

No clue how you did not notice anything before it happened, By rights, your handlebar should have moved independently from the forks.

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12/27/2017 12:44 AM

Wayne S wrote:

Tim,
Your forks/stem must have come apart from the cinch bolts not clamping the stem to the fork, most likely pulling the ...more

As I said above, the clamping area on that stem was almost pinching due to how tight I keep those bolts, and the stem wouldn't fit back on the steerer tube without being loosened..

There wasn't enough good threads threaded into the fork to resist the stem. And a thread is only a couple mm thick, if that, so it didn't have to budge too far to ruin the threads.. If I would have had a good condition cap with good threads all the way down, it wouldn't have happened. Not sure why its so hard to believe that my bike failed due to running a damaged part..

& I've snapped a pedal body & ate shit on a roof drop, got back up immediately and landed the drop, not knowing my pedal was snapped. When I'm in my zone, nothing can bring me out of it lol.

You can hear my pedal snap here
& I landed it with the broken pedal here

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12/27/2017 12:53 AM

HardBMX_Tim wrote:

Since you mention it, the stem I was running at the time of my incident was actually almost pinched completely. So, on the ...more

"the stem I was running at the time of my incident was actually almost pinched completely. So, on the contrary, I know it was likely tighter than necessary"


uh, if they were pinched then that right there was your problem. The metal bent in so much that the pinch bolts could barely do their jobs in keeping the stem tight, which is why your stem came off like that. Think about it, the bolts rely on that little slit to compress in towards each other... they're not supposed to touch, and if they do, there's no compression to be made
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12/27/2017 12:54 AM

Oh, so your stem must have been hardly even on the steerer? It certainly doesn't look like there's enough steerer showing to securely clamp the stem on.
Compression bolts are literally just for tightening the headset. An easy way to describe this is: have you ever over tightened the compression bolt on a non sealed headset? It over tightens the headset until it can barely move. So it takes very little torque to get the tightness just right. And you think that little amount of torque on a wafty bolt is what helps keep the stem on? So how do seat clamps work? We don't need an extra bolt to keep the seat in place. And another example of how pinch bolts work is cranks. It's not ideal, but I've seen people run primo cranks with no compression bolt with no issues at all. The pinch bolts are what hold the arms on (I could use shimano hollowtech 2 chainsets as an example here too. 2 pinch bolts, one compression bolt that's specifically designed to only be finger tight. Yet you never see crank arms falling off).

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12/27/2017 1:04 AM

sundaybmxRR wrote: "the stem I was running at the time of my incident was actually almost pinched completely. So, on the contrary, I know it was ...more

Then how did I ride that same stem, forks, headset cap, and gyro plate without an issue for more than a year after the matter? Once equipped with a brand new compression cap. Bought the forks used and the cap was a bit stripped from the guy before me, I should have replaced it anyways. I assumed that because there was enough threads to tighten everything down, it would be fine, and look where that got me.

And yes, it was almost pinching, I'd say it was about 50% of the way pinched from being extra tight for the year or so that I owned it. The threads still worked great and obviously it was clamping fine enough if I had to loosen the bolts up to put it back on the forks..

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12/27/2017 1:11 AM
Edited Date/Time: 12/27/2017 1:22 AM

grumpySteve wrote:

Oh, so your stem must have been hardly even on the steerer? It certainly doesn't look like there's enough steerer showing to ...more

You guys are too much.. I feel like I'm preaching the earth is round to a group of flat earth believersgrin

As I stated in my OP, my fork was 3/4 of the way into my stem, as I run on most of my builds. I continued to run it this way with a new compression bolt for over a year of daily riding with out an issue..

Also, if you look closely enough, you'll see my frame wasn't sitting all the way on the fork in this picture. The rest of my steerer tube is under the head tube chillin.. got yagrin
Photo

Also, how can you compare a steerer tube and stem to a seat post and seat clamp? One is constantly being tugged on and the other MIGHT get landed on hard every now and then.. I want to think that a chromoly clamp on aluminum would even grip better than vice versa?

If the damn cap wasn't necessary, forks would come with an installation tool instead of a bolt..

Still not sure why everyone wants to argue about my own personal experience. dizzy I'm not lying to y'all I promise. grin

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12/27/2017 2:29 AM

HardBMX_Tim wrote:

You guys are too much.. I feel like I'm preaching the earth is round to a group of flat earth believersgrin

As I stated in my ...more

If you were preaching that the Earth is round to us, we wouldn't be here to argue that be cause we'd be too retarded to know how to log onto a computer. Flat Earthers are among the dumbest creatures on the planet.



None of us are questioning whether or not they're necessary, they ARE necessary to install your fork and tighten your headset. But if you choose to remove it afterwards, it's not going to be like riding without an axle bolt or something, the stem is still tight and as long as it has an adequate clamping area and isn't pinched, it's not going to just pull off unless the bolts are barely tightened. And that thin piece of aluminum isn't going to do much to prevent your stem from flying off either if you did something/landed hard enough to have that happen in the first place which is likely what you did when learning 540s because I have a hard time believing anyone could just rip a stem off the steerer tube using just the force of them yanking up on the take off, unless it was barely tightened or they're the fucking hulk having their feet planted on the ground intentionally yanking up on it.

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12/27/2017 3:08 AM
Edited Date/Time: 12/27/2017 3:11 AM

sundaybmxRR wrote:

If you were preaching that the Earth is round to us, we wouldn't be here to argue that be cause we'd be too retarded to know ...more

To each their own I guess. I've been out on a riding related injury for 4 months, I guess I'd juat rather not go through another one simply because of negligence.

And if the bolt is only for installation, then why do they bother threading the steerer tube? I assume it would be significantly cheaper to just include a cheap installation tool or a mallet than to thread the fork and machine a bunch of custom bolts with laser etched logos and such..

Sure, maybe you can get away with riding without a compression bolt, just in the same way that you can get away with riding without a helmet. Everything is all fine until that one time it's not, & it only takes that one time to be life changing or worse.

I just don't think it's good advice to be telling people it's okay to ride without it. There's plenty of instances of the stem coming off due to negligence of the compression bolt, even outside of my own experiences. I'm sure it works fine for some people, but we don't know what this guy or the next guy reading this has going on. He could have a super short steerer tube, or a cheap stem with a poor clamping surface, or a stem thats beginning to pinch (since according to you that makes it unable to clamp properly.. i call BS), etc. & riding without the bolt could absolutely be a catastrophic for them for all we know.

I can drink a whole gallon of milk in an hour no problem, but I wouldn't go around recommending people to try it.. that would be mean.

& as far as I'm concerned, you can tell me it was my stem that was the problem all day long, but I'm still going to believe the year+ of experience I had riding the piss out of it afterwards without any issue.

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12/27/2017 3:24 AM

Well, I tighten my pinch bolts properly, so I wouldn't be even remotely worried about my stem magically finding a way to slide off the steerer tube. When you sit on your seat, does it slide down? There's only one bolt holding that..... 2 bolts that handle greater torque is adequate to hold a stem onto the steerer.

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12/27/2017 3:44 AM
Edited Date/Time: 12/27/2017 3:59 AM

grumpySteve wrote:

Well, I tighten my pinch bolts properly, so I wouldn't be even remotely worried about my stem magically finding a way to slide ...more

There's a huge difference in force between my 200lb self resting my ass on my seat & pulling up with X amount of force to lift my then 250lb self and 30lb bike into the air repeatedly, back to back, over the course of an hour or so. & correct me if im wrong, but a chromoly clamp will dig into an aluminum post far more than an aluminum clamp will with a steel post. & a seat post has far more contact surface than a steerer tube in a stem, so your comparison is pretty irrelevant..

I'm really not sure what to tell you. My pinch bolts were tighter than necessary and it still happened. And that's with an Odyssey stem and fork. Didn't have a problem with it for the few hours before trying 540s, or any of the sessions prior to this one. & I don't understand how the pinch bolts would have magically tightened themselves in my stem after the incident, if they were actually loose like you are so sure they were.. also not sure how my bars stayed straight for over an hour of trying 540s, landing goofy on the bike, bailing and throwing the bike, the whole 9 yards.. you'd think they'd move side to side before they'd move upwards with a compression bolt..

& do you actually have experience running forks without a compression bolt for a long enough period of time to deem it as safe? Or am I the only one here giving this lad advice based off of personal experience?

Still don't know why you feel like this is up for debate.. I have nothing to lie about, what happened happened. I'm only sharing my personal experience in hopes of keeping this guy from injuring himself. I could care less if you believe me, I remember it all like it was yesterdaygrin

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12/27/2017 5:44 AM

I'm not saying you're lying. But bolts just don't loosen themselves like that. If they did, yeah your bars would've moved, but they didn't.

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12/27/2017 6:11 AM

HardBMX_Tim wrote:

There's a huge difference in force between my 200lb self resting my ass on my seat & pulling up with X amount of force to ...more

It's certainly not ideal but I ran no compression bolt for over a month with no problems at one stage. As long as your stem is clamping right, it's usually fine. Having the compression bolt always in the fork is both a safety feature and an 'ease of use' feature. It's there as a safety for if somebody doesn't tighten their pinch bolts enough or if somebody doesn't have enough clamping area, to give you some chance of realizing there's a problem before it injures you(the stem should spin on the steerer a little). It's not supposed to take much, if any load and especially not for any length of time.

I ran 3 piece cranks with only 1 crank bolt for almost a year and a half at one stage as the other was snapped off in the spindle by the original owner. As long as the pinch bolt on the side without the crank bolt was tight, it was fine. Didn't slip in the entire time I had those cranks.

On the pinched stem point, the 2 sides of the clamp need to be apart from each other in order for there to be tension and therefore, clamping load on the steerer. If the 2 sides of the clamp are touching, they might clamp on the steerer some small amount but most of the force will be trying to crush the other side of the clamp.

On the seat tube contact surface point, the only place on the entire seat tube that is clamped on is right underneath the seatclamp. The rest is just basically just floating there doing nothing until the odd occasion where you land on the seat hard enough to flex the post. Then, it pushes against the inside of the seat tube and prevents the seatpost from ripping out altogether.

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My Sunday Soundwave V3 Build
Insta: @p.gibbons

"You can't educate pork"
- grumpySteve

"Life should not be a journey to the grave with the intention of arriving safely in a pretty and well preserved body, but rather to skid in broadside in a cloud of smoke, thoroughly used up, totally worn out, and loudly proclaiming "Wow! What a Ride!""
- Hunter S. Thompson

12/27/2017 7:30 AM

guys a compression cap is like $10... You don't need to roast this guy tim because he is saying the dude should spend $10 and be safe. Also its nothing like a seat clamp....

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12/27/2017 7:41 AM

watsonbmx wrote:

guys a compression cap is like $10... You don't need to roast this guy tim because he is saying the dude should spend $10 and ...more

Yeah, Tim seems like a good dude. Isn't the entire purpose of the forums to share and discuss your experiences and views though?

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My Sunday Soundwave V3 Build
Insta: @p.gibbons

"You can't educate pork"
- grumpySteve

"Life should not be a journey to the grave with the intention of arriving safely in a pretty and well preserved body, but rather to skid in broadside in a cloud of smoke, thoroughly used up, totally worn out, and loudly proclaiming "Wow! What a Ride!""
- Hunter S. Thompson

12/27/2017 8:20 AM

watsonbmx wrote:

guys a compression cap is like $10... You don't need to roast this guy tim because he is saying the dude should spend $10 and ...more

I agree with this Tim has helped me quite a bit over the last day or so and the bars coming off was probably one of those things a bit like the time I somehow sheared the heads off the anti roll pins in my back peg. Spending 10 bucks to have peace of mind over something is worth it imo. Also without a top cap what are you going to do when you need to tighten your headset?

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Hmmm

12/27/2017 9:53 AM
Edited Date/Time: 12/27/2017 9:53 AM

HardBMX_Tim wrote:

Since you mention it, the stem I was running at the time of my incident was actually almost pinched completely. So, on the ...more

That's fucking crazy, and so scary. That picture alone, no matter what the cause, is enough evidence that giving your bike a once over before every ride is crucial.

Personally, I understand that shit happens and sometimes you gotta ride without this or that, but I wouldn't do it for long. I like my bike dialed. Everything tight. Everything working right. Those "what if's" can quickly become "should haves"

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12/27/2017 11:15 AM

Whenever I've tried this, no matter how tight my pinch bolts are, my stem always gets loose within a few hours. Riding with a lose headset will ovalize your head tube eventually. You can buy a cheap cap for under $10. Why not?

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12/27/2017 11:18 AM

ggallin422 wrote:

Whenever I've tried this, no matter how tight my pinch bolts are, my stem always gets loose within a few hours. Riding with a ...more

I don't know what you're doing different, I did it for over a month and had no problems.

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My Sunday Soundwave V3 Build
Insta: @p.gibbons

"You can't educate pork"
- grumpySteve

"Life should not be a journey to the grave with the intention of arriving safely in a pretty and well preserved body, but rather to skid in broadside in a cloud of smoke, thoroughly used up, totally worn out, and loudly proclaiming "Wow! What a Ride!""
- Hunter S. Thompson