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Front end drift/float @ speeds above 50mph

Old 07-11-2018, 08:55 AM
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KevinL46
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Default Front end drift/float @ speeds above 50mph

Hi all. I'm a long time lurker who finally made the jump to being a member. I'm the 3rd owner of a 102k actual miles, L46/M21 '69 convertible with a set of G60 Goodyear PolyGlas tires. I've owned the car for several months now and love it, it's such a blast to drive. Everything works but the one issue I have is that the car can be a little squirrelly as you approach highway speeds. It drives pretty straight with only the slightest pull to the right (so slight it's almost not noticeable and I even hesitate to mention it). However, as I get up to speeds of 50mph and greater it seems to have a drift or float in the front end or at least I think its coming from the front end. What I mean by drift/float is that without hitting a bump, groove in the pavement or whatever, @70mph I'll suddenly find myself going from the center of my lane to 6" into the lane next to me, without any input to the steering wheel from me. This could be either the lane to the left or the right. It's like something is loose in the front end allowing the wheels to go one direction and the suddenly the slop or looseness allows the wheels to shift orientation ever so slightly the other direction (I hope that long rambling explanation makes sense). I thought for sure that it must have a bad bushing(s), tie rod end, ball joint or something. Since I couldn't locate anything, I took it to the front end shop and had them take a look. They took it for a drive and said they experienced exactly what I described but they found everything up front was tight as a drum and said all the bushings looked better than what they see in most 5 year old cars. The only recommendations the front end guys had was to ditch the PolyGlas tires (which was already on my to do list) and talk to someone who knew C3 cars and see if they had any suggestions. So that leads me to here, reaching out to this community for any input on what you think the root cause might be or where I should start looking next to find what's causing the problem.

Thanks in advance for sharing your knowledge - Kevin
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Old 07-11-2018, 09:14 AM
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dochorsepower
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Well, welcome to the forum. First of all Those tires have not been made in this century, they're dangerous.. Next, you should have the condition of front suspension bushings and steering checked by a C-3 Corvette specialist - NOT the auto shop down the street.
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Old 07-11-2018, 09:34 AM
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gbvette62
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Without a doubt, get rid of the Polyglas GT's. If you plan on driving the car, a good set of modern radials, like BF Goodrich TA's, is the way to go. The original tires on the car were F70 x 15 bias ply's, and the modern equivalent to the F70's is P215/70R15. There are reproductions of the original F70 bias ply tires available, but they're really best for show cars and "trailer queens", and not for cars that are driven regularly.

Once you've replaced the tires, I would find a shop familiar with the Corvette suspension, and have a good, 4 wheel alignment done. Making sure the Corvette's independent rear suspension is properly aligned, is as important as the condition and alignment of the front end.

Let us know where you are in Florida, as there are a number of Corvette shops in Florida, and a number of members here live in Florida, so I'm sure someone can recommend a good shop to take your Corvette too.

Welcome to the Forum!
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Old 07-11-2018, 02:15 PM
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Originally Posted by gbvette62 View Post
Without a doubt, get rid of the Polyglas GT's. If you plan on driving the car, a good set of modern radials, like BF Goodrich TA's, is the way to go. The original tires on the car were F70 x 15 bias ply's, and the modern equivalent to the F70's is P215/70R15. There are reproductions of the original F70 bias ply tires available, but they're really best for show cars and "trailer queens", and not for cars that are driven regularly.

Once you've replaced the tires, I would find a shop familiar with the Corvette suspension, and have a good, 4 wheel alignment done. Making sure the Corvette's independent rear suspension is properly aligned, is as important as the condition and alignment of the front end.

Let us know where you are in Florida, as there are a number of Corvette shops in Florida, and a number of members here live in Florida, so I'm sure someone can recommend a good shop to take your Corvette too.

Welcome to the Forum!
Thanks GBVETTE62. I'm in the Northeast Florida/Jacksonville area. Any reputable Corvette shop recommendations in the area would be appreciated.
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Old 07-11-2018, 11:47 PM
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doorgunner
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Unofficial quick-check pictures below...…………………….



BEFORE DIY temporary camber adjustment






AFTER DIY camber adjustment...notice there is NO gap between tire and level now.
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Old 07-12-2018, 12:26 AM
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Metalhead140
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Also, worn rear end suspension bits can also cause wandering at speed that feels like it's the front end - voice of experience here. Check out the rear as well.
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Old 07-12-2018, 07:44 AM
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Pictures are always good for me, Thanks Doorgunner
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Old 07-12-2018, 07:46 AM
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Originally Posted by Metalhead140 View Post
Also, worn rear end suspension bits can also cause wandering at speed that feels like it's the front end - voice of experience here. Check out the rear as well.
Good advice I had not considered, Thanks
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Old 07-12-2018, 05:41 PM
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Do you have play in the steering going straight? If you have to move the steering wheel a few inches you are not steering the car you are aiming it, I agree a complete front suspension check is in order. The car should not wander under 120mph
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Old 07-22-2018, 10:16 PM
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Originally Posted by gbvette62 View Post
Without a doubt, get rid of the Polyglas GT's. If you plan on driving the car, a good set of modern radials, like BF Goodrich TA's, is the way to go.
Just to follow up on my original post, Replacing the Polyglas GTs did the trick! I put a set of modern Goodyear p225/70R15s on it and now it rides like it's on rails. Previously, I'll admit it was a bit of a hairy ride when you got above 55 but with the new shoes I got it out on the interstate and did "a wee bit" over over the posted 70mph speed limit, purely for testing purposes , and it couldn't have handled better.
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Old 07-22-2018, 10:29 PM
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Originally Posted by KevinL46 View Post
"a wee bit" over over the posted 70mph speed limit, purely for testing purposes
That's just "normal Corvette testing" ......you won't get in trouble on here for that, everyone's a bit of a test pilot
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Old 07-30-2018, 09:52 PM
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Hell, if I could, I'd be doing daily tests. Like... leave a work meeting early because I need to run the unit tests on the corvette daily...
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Old 09-19-2018, 03:05 PM
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Had a similar issue definetly check rear trailing arm bushings. Mine where so hard they shattered when moving the arm while on lift.
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