Bikin Vibration

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Bikin Vibration

Postby Gabe on Tue Jun 24, 2014 2:36 pm

Hi Guys, wonder whether someone could help. I am battling for some time with a vibration on my Birkin starting at 110 kph right through. I have balanced the wheels, re balanced them, replaced the tyres and it is still there. Checked suspension for play, front bearings and everything seems fine. I have my new rebuild Kent plus type 9 gearbox fitted, shaft balanced and the vibration is still there. I am at my witts end, I swear I chop this car up and sell for scrap..!! I need some objectivity here, anyone with some advice where to look next is welcome..and yes the vibration was there with the old gearbox and engine as well :? Cheers Gabe
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Re: Bikin Vibration

Postby 200sxrb25 on Tue Jun 24, 2014 11:22 pm

Did you check your prop shaft?
Is your wheels not bend?
Is your diff side shafts not bend?
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Re: Bikin Vibration

Postby Gabe on Wed Jun 25, 2014 7:28 am

Hi there, checked all of those, seems fine. It almost feel that it originates from the front, the only thing that I can find that maybe, and this is a long shot, the right front disk pinches slightly. In other words when you tun the disk it is free to a point and then it pinches not a heck of a lot, but it pinches.

Just maybe that could be it that starts at that particular speed some resonance that manifests itselves as a vibration. I tried last night to eliminate the "pinch" without succsess. The rotor is not warped, it is like I have to move the caliper a tiny bit inwards as it seems the pinch is from the inside disk. The problem is that now it it is stuck completely if tighten up. Will give it another go towards the weekend. Thanks for trying to help. Appreciated.
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Re: Bikin Vibration

Postby BradW on Wed Jun 25, 2014 9:10 am

Gabe wrote: the right front disk pinches slightly. In other words when you tun the disk it is free to a point and then it pinches not a heck of a lot, but it pinches.


If it 'pinches' at one point only and the disk is not warped or unevenly worn, then either your stub axle is bent, or your caliper mounts aren't true to the rotation of the hub/disk.

Does the vibration go away or get worse when you apply the brakes ?

Can you visually see any 'runout' in the wheel/tyre when driving ?


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Re: Bikin Vibration

Postby Gabe on Thu Jun 26, 2014 6:45 am

Hi Brad, disc seems fine and that is what it so frustrating, as said earlier, the vibration starts at about 110 and stays there up to flatout, as soon as you slow down to about 110 and under it goes away. I went through the whole car and nothing seems to be wrong. I have done the one caliper last night giving it more space so it does not have that "pinching" spot anymore. The left one touches also slightly, will give it more space and run the car and see what happens, will let you know. It is complete like almost a unbalanced wheel, I have tried to eliminate that as said before new tyres rebalanced about four times to make sure.. :? Cheers thanks for trying to help.. :)
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Re: Bikin Vibration

Postby Gabe on Thu Jun 26, 2014 6:48 am

Sorry do not want to sound dom, what do you mean by "runout"..??
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Re: Bikin Vibration

Postby BradW on Thu Jun 26, 2014 8:53 am

Gabe wrote:Sorry do not want to sound dom, what do you mean by "runout"..??


If you look at the edge of the tyre at the top when it's spinning does it stay straight or look like it is moving from side to side
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Re: Bikin Vibration

Postby Gabe on Thu Jun 26, 2014 10:38 am

Checked that its looking straight, stable under braking etc. find no play on front end nothing, bearings are fine hence my frustration. It cannot be the drivetrain as it is behaving exactly the same as before the engine, gearbox and driveshaft replacement. If you drive in town, nothing wrong, go over 110 and that is another story. Let me do the left caliper and see how she behaves, will let you know... Regards GB
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Re: Bikin Vibration

Postby BuzzFuzz on Thu Jun 26, 2014 11:33 am

What does the vibration feel like? (strange question, buzzing, slow throb... :? )

Just thinking if its something to do with the drive train or possibly the aerodynamics.

Just as a test, take the front fenders of and give the car a run. Maybe there is resonance being caused by the air/fender vibrating down the fork into the hub. Its a long shot, but seems you've covered all the mechanical issues.
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Re: Bikin Vibration

Postby Gabe on Thu Jun 26, 2014 12:52 pm

Would say feels like a "buzz" almost like a wheel thats out of balance, it would start at about 110 and at approximately 115/120 it is "buzzing" the frequincy stay the same from thereon. Also thought it could be the cycle fenders, but broke one on my way back from Pmb after a day at Cars in the Park. So one fender on, one fender off, vibration was still the same..! Come to think of it, almost like driving on a coarse cement road with that draining grooves just a bit more amplified. Tyre presure is at 1.3 bar new semi slicks on. :?
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Re: Bikin Vibration

Postby andersonhdj on Thu Jun 26, 2014 5:23 pm

Just thinking at a tangent here - run her up to vibration level , pull her out of gear , engine at idle , and freewheel , what happens if anything?
You're saying , it's the same engine and gearbox assembly as before ?

Just by way of an arb story , one of the vehicles in our workshop was a Toyota Stout , a real "kanniedood" , it was fitted as from factory with heavy duty truck type tyres and the ride was real hard , but it was driveable at any speed it could attain ! :shock:

Anyway , some one in the workshop got the bright idea to fit RV180's , it was good up to about 110km but between 110 and 130 it became a death trap, it appeared as if the frame was flexing and oscillating and it felt as though some one was sitting behind the seat trying to kick your kidneys out! :lol:
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Re: Bikin Vibration

Postby Gabe on Fri Jun 27, 2014 6:42 am

Hi Andersonh, it is a new drive train, but a good idea, I will run her over the weekend, I finished the calipers last night by eliminating the "pinch" they had, just used a thicker washer that centred them more!... Thanks again for everyones input, much appreciated. Cheers Gabe
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Re: Bikin Vibration

Postby Gabe on Mon Jun 30, 2014 6:39 am

Ran the car yesterday and the vibration is about 60% better, also took it out of gear as suggested by Hamish, but alas, the vibration remain. I think I will rebalance the front wheels and see what happens.... :| Gabe
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Re: Bikin Vibration

Postby andersonhdj on Mon Jun 30, 2014 11:53 am

Keep us posted. There must be an answer. Is it a live axle btw ? Also windscreen fitted ?
Hamish.
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Re: Bikin Vibration

Postby Gabe on Mon Jun 30, 2014 12:05 pm

Live axle yes, no windscreen, have a set of Brookland screens on, trust me they are mounted properly and are sturdy.. I am starting to think maybe it is a rim thats out, running 15 inch Superlights and they always battle a bit to balance one of them, long shot one can only try... :|
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