Answer me a question for a change!

[Ken]

Has anybody run skinny wheels and tires on the front of their Corvette. Of course, the reason for doing this is for drag racing.

At any rate, my question regards whether the move to skinnies in the front had any affect on the C4's handling.

I've been fighting what seemed to be a losing battle trying to find someone I could trust to balance wheel/tire combinations competently, but last week I finally found someone who knew what he was doing. Which was of course, just taking time to re-check one's work after the combo is balanced. :duh

The combination of which I speak is my Weld Wheel/ET Street setup.

Anyhow, John got 'em balanced up and I remounted the set the other day. I took it out yesterday to the regular Friday night cruise, and noticed that I still had a vibration of sorts at around forty miles per hour.

I took it over there again today and experimented by taking my hands off the wheel when the event occured -- no difference. Tracked straight and true.

Below forty, and above forty-five or so, there's no problem, except for the fact that one knows one has skinny tires up front. It's a BIG difference from what we're used to with our big fat tires. :L

So, I'm kinda curious of course, as to why this is occuring. I guess I'll mount the Borbet/Firestone combo back on the front to see what happens.

Man I had a couple of good runs going there and back today! I was able to nail it and go through the gears on the streets around the Mobil refinery. Those streets are usually pretty busy during the week, but on the weekends it get wide-open for a couple of miles.

I had fun, but boy, I gotta watch myself. :L

 

[Mac]

The biggest effect of fats & skinnies is the radical shift in braking effectiveness. Your front tires account for the majority of braking power and if you limit your contact by reducing the size of your tires, the braking suffers.

The next biggest effect is on cornering... hang on!!

Many things can cause speed-related vibration; tires are just the usual culprit. It could be your brakes, your bearings, hell- even your driveshaft.

Glad you had some fun!!

-Mac

 

[Ken]

No, it's only when I put the skinnies on the front. That's why I answered my own question and said I guess I'll just try it by putting my Borbets and Firestones back on the front to test it out. I just wondered if it would have any affect on the geometry of the suspension that would cause that vibration/shimmy/shake effect, other than of course the handling in the canyons.

 

[redc4corvette]

http://www.ccwheel.com/

 

[KANE]

Has anybody run skinny wheels and tires on the front of their Corvette. Of course, the reason for doing this is for drag racing.

At any rate, my question regards whether the move to skinnies in the front had any affect on the C4's handling.

I've been fighting what seemed to be a losing battle trying to find someone I could trust to balance wheel/tire combinations competently, but last week I finally found someone who knew what he was doing. Which was of course, just taking time to re-check one's work after the combo is balanced. :duh

The combination of which I speak is my Weld Wheel/ET Street setup.

Anyhow, John got 'em balanced up and I remounted the set the other day. I took it out yesterday to the regular Friday night cruise, and noticed that I still had a vibration of sorts at around forty miles per hour.

I took it over there again today and experimented by taking my hands off the wheel when the event occured -- no difference. Tracked straight and true.

Below forty, and above forty-five or so, there's no problem, except for the fact that one knows one has skinny tires up front. It's a BIG difference from what we're used to with our big fat tires. :L

So, I'm kinda curious of course, as to why this is occuring. I guess I'll mount the Borbet/Firestone combo back on the front to see what happens.

Man I had a couple of good runs going there and back today! I was able to nail it and go through the gears on the streets around the Mobil refinery. Those streets are usually pretty busy during the week, but on the weekends it get wide-open for a couple of miles.

I had fun, but boy, I gotta watch myself. :L

Ken-

I ran 275s on the rear and 225s on the front of my 71 El Camino SS in highschool. Granted, it was a station wagon body Chevelle- but it did affect handling on a car that already had weight transfer issues. Also- these weren't true 6 inch skinnies.

I remember seeing an indy car with two sets of front wheels. They were smaller so as to cut down on drag. Having them in tandem allowed the car to get the same amount of surface area on the pavement. So, that being said, there is enough support for the practical application of the physics of rolling resistance, mass, and wheel/tire size.

Me- I'd only run the skinnies if my car lived on the track. If you enjoy carving up the turns onyour favorite stretch of road.... leave the fronts alone or better yet run "not quite skinnies but skinnier than the rears".

 

[Ken]

What? You work for those guys or something? :L

I'm aware of the wheels and the availabilty. Did you happen to notice the selection choices? For Corvettes they specify C5s but no C4s. Their stock offsets are a little different than my C4. I know, I know -- there's the "Other Cars" section. :L

I'm not looking to buy any wheels or anything; this peculiarity isn't bad enough that I can't drive through it. I'm mainly curious to see if anyone else has experienced similar problems.

I'm not usually running this combo around anyway; they're just on there for kicks right now.

 

[Ken]

Johnny, mine aren't truly "skinnies", aka "pizza cutters", either. I got the skinniest I could get, which is around a 225 width I think, because I couldn't fit truly skinny rims on front without reverting to my stock front braking system. No clearance with the Baer rotors and calipers, and i wasn't about to give those up. Not unless, as you say, the car lived on the track.

 

[G Winter]

You say a vibration of sorts, are you sure it isn't a wobble A wheel balance vibration at 40 to 45 isn't really that common. Usually balance doesn't bother till near 60 IMO. It may be the diffence in load on the front end parts. From what I know of you I would tend to believe you have the front end in very good repair,so I don't think worn parts is the problem.Toe in could cause a shake at a given speed. Caster can also have some very strange effects.I did some front end alignment for a time and the figures given in the manuals are usually a range. Being at one end or the other of the range can make a lot of diff. I did a search on google and did indeed find confermation that caster effects wheel wobble. With the wider tires there may be enough load on the front end to not cause a problem. Depening on how much it bothers you , maybe live with it ?

 

[WhalePirot]

Surely changing tires will tell you if it's therein lies the problem. While the car's nose is up, I would check for wheel/tire runout. One or the other, or both may not be truly round. Stay simple on this, Ken, at least for now.

I had a set of Dunlops that were not round, on my '63 'split'.
My stock Z-51 wheels were of those that were drilled off-center (in the Mexican factory, OldGoat ). They would hold a balance for about 10k, then start to shake. I thought it was the wide Gatorbacks until I read about the problem; after changing to these non-shaky Epsilon wheels.

 

[Ken]

I guess it could be a funny wheel except, wouldn't that show up on the balancing machine? I mean hell, it senses everything else. :L

And you're right Scav, my suspension is in good shape. That's not something that I would ignore.

 

[redc4corvette]

http://www.vbandp.com/instructions/htmlinstruct/align.htm

 

[Ken]

Thanks John.

 

[WhalePirot]

wouldn't that show up on the balancing machine?

It didn't in my case. The only way I could get a satisfactory, if temporary balance was to have them done on the car. I marked the lugs so I'd get the wheels reinstalled the same way.

A slow rotation of each wheel/tire, on the car, should point to or eliminate this as a problem. A dial indicator would be helpful. Oh hell, you know what to do.

 

[Ken]

:L Yeah, you got that Mike.

I wasn't really seeking an answer, so to speak, as much as seeing if there was anyone else who has encountered this anomaly.

 

[redc4corvette]

I would put it up on jack stands ,run it up to 130 mph and see what vibrates first.

Drive shaft half shaft or tq converter.

Then add a chamber brace and a center brace to the pop top.

When all else fails add an 8 point roll bar.
Or do what I did ,took the tires off my 94 and that cured it.

 

[Grizzly]

Since we are theorizing (guessing) I'll put in my two cents. I think you have a balance problem in your discs. The big tires have enought gyroscopic action to mask the problem the light tires don't. Find someone with an on the car balancer. They used to be quite common. Looked like a floor jack with a roller and an attachement for the wheel. That balances the entire rotating mass, wheel, tire, brakes and bearings. Just mark one of the studs and put the wheel back on the same way every time.

If you doubt the gyroscopic action bit, just find and old bicycle wheel and hold it by the shaft and get someone to give it a good spin. If you sit on a bar stool and tilt it, it will pull you right around.

Aren't old cars wonderful.................................

 

[Ken]

the rotor's are a possibilty I guess, Grizzly. Thanks.

And YES, old cars are, as Tony the Tiger would say -- GR-R-R-REAT! :J