The Camaro Club (UK)
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1st Gen speed wobble or bad vibration?
http://classiccamaroclub.mfatw.com/viewtopic.php?f=9&t=4459		 Page 1 of 2
Author:  Pa's F-bodies [Sun May 03, 2015 12:57 pm ]
Post subject:  1st Gen speed wobble or bad vibration?
Hi I'm going crazy trying to find a really bad vibration on my 68 Firebird it starts at just over 65mph and gets unbearable at 80mph like the car is going to pull it's self apart, it shakes violently and you can see the hood bobing up and down about an inch, has anyone had this before?

Ive had the rear p on jacks and run it upto 90mph and it's very smooth so I don't think it's in the rear or the drive line.

also spun the rims up on a balancer and there not bent and changed the tyres on the front.
Author:  Twistedsanity [Sun May 03, 2015 2:56 pm ]
Post subject:  Re: 1st Gen speed wobble or bad vibration?
Is this the convertible?
Author:  Pa's F-bodies [Sun May 03, 2015 5:57 pm ]
Post subject:  Re: 1st Gen speed wobble or bad vibration?
No it's my 400 coupe, most of it is original apart from all poly bushed and 17" TT2's with 225/50/17 fronts and 245/45/17 rears,

No play in the bearing's or steering joint's it just feels like some sort of harmonic wobble up and down, a sort of 0ne inch speed bump type of feeling. it's not coming through the steering wheel it's more like the front end is juddering up and down.

I'm fed up putting t on the ramp and staring at it....


My convertible has vibes to at speed but I can live with that and they do seem to be prone to it anyway :(
Author:  chevy-stu [Mon May 04, 2015 1:41 am ]
Post subject:  Re: 1st Gen speed wobble or bad vibration?
Propshaft?
Author:  Twistedsanity [Mon May 04, 2015 8:22 am ]
Post subject:  Re: 1st Gen speed wobble or bad vibration?
I have just been reading a new book about camaros which highlighted the excessive noise and vibration when they first made them, caused by the front chassis rails joining the body and stating how they lessened it by utilising big soft rubber bushes at the joints, which you have poly bushed, maybe that's part of the issue? Did u drive it before the poly bushes were installed? It also says how they added huge hanging weights in all four corners of the convertibles to stop noise and flex which is why I asked if it was the ragtop
Author:  Pa's F-bodies [Mon May 04, 2015 5:12 pm ]
Post subject:  Re: 1st Gen speed wobble or bad vibration?
OK thanks I'll look into the soft bushes, no I didn't drive it before as I bought it in bit's, funny isn't it I was thinking the the other way and adding joiner rails to the chassis.

I know about the Convertible with the cocktail shaker in the corners, I don't generally drive it fast so I'm not to worried about that one altho it is a shame because it has got a very quick motor in it :)

Not the prop as I've had it on jacks and run it up to 90mph and its very smooth.
Author:  TopCat [Mon May 04, 2015 7:18 pm ]
Post subject:  Re: 1st Gen speed wobble or bad vibration?
Have the new front tyres been balanced?

what suspension settings are you using

all track rod ends OK?

What torque are front wheel studs set to?

how old are your front shocks?
Author:  Pa's F-bodies [Tue May 05, 2015 8:48 am ]
Post subject:  Re: 1st Gen speed wobble or bad vibration?
Hi Top cat my shocks are new Gabriel's all round but I have just taken off the rears as I think they were too stiff and made it a bit unpleasant or harsh to drive,
I have also got new front and rear sway bar's fitted 1.25" front and .75" rear which keep the car very flat when cornering.

I have only got 3 leaves now in my rear springs as the new 5 leaf springs that were on the car were very hard and made it sit too high.

My steering is set up with standard toe out but with an extra .25" inch shim to give a little extra castor, I havebeen reading however that may be with radial tyres it my be best to reduce the toe out by 50% as the original spec's were for cross ply tyres.

I think each time I turn a spanner I'm creating a bigger monster and its spoiling my car for me, I want too move forward with it and fit some new Stainless exhaust and disc brakes, but I don't feel like spending any more time or money on a car that I'm not enjoying driving.

Do you have any suggestion on a front end spec for me please, before I beat this thing with a stick :roll: and get back in my lovely smooth Z28.

Thank you
Author:  3rdGenmalc [Tue May 05, 2015 4:33 pm ]
Post subject:  Re: 1st Gen speed wobble or bad vibration?
Are the tyres in good condition, no flat spots or sidewall bulges ?
Author:  TopCat [Wed May 06, 2015 11:23 am ]
Post subject:  Re: 1st Gen speed wobble or bad vibration?
Defo first check is whether those tyres are bulging or have flat spots

Type caster camber toe total
Settings
Hard street 2 1/2 -1 3/32
Road racing 3 -1 3/4 1/16

All measurements taken with driver weight added caster and camber measured in degrees toe in in minutes

If vehicle has a lot of rack get as much caster available as long as camber is zero.

If you go musch more than -1 3/4 degrees neg camber you may have front tyre wear
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