Wheel adapter size?

I picked up some C5 Z06 wheels a while back to put some (wider) track tires on the '69 (I got tired of always having the skinniest tires at any event). Got the tires mounted yesterday (a damn sight tougher job than mounting 60 profile 15 inch tires) and installed on the car. The rears (10.5"/285-18) fit perfectly with 2.25" adapters. The fronts (9.5"/275-17) fit with no clearance issues, but they're tucked in about a half inch narrower than I would like for appearance. Another pair of 2.25" adapters should do the trick, but before I spend the money is there any issue I'm not considering? I'd like the track width to be as wide as possible for best handling. I haven't looked at the change in scrub radius, but I hope that issue is minimal at higher speeds. I haven't yet measured the wheel offset to see where I'm at with the adapters to see how much the net offset is (affecting wheel bearing stress). So, any thoughts before I order different adapters next week?

Thanks,
Mike

So you want to move the front wheels "out" 1/2" ? Why are you saying you want to use another pair of 2.25" adapters? That would move the wheel way past the fender ???

Just a thought - They probably aren't a HUGE expense - but you could give it a go and see how the car handles first.

See how the car handles with regard to understeer/oversteer and then play with the track/scrub by using the adapters. Wider front track (when you add the adapters) will cure some understeer and then add the front adapters if needed. A lot easier to use those than swap out anti-roll bars, and major geometry changes!

Cheers - Jim

BTW: My starting point is similar -- 315/35/17 rears and 285/45/17 front. But I gotta build this new rear end - subframe, etc first!

Mike, my car is much more stock than yours, sorry but I can't keep all the modifications straight between guys here, much less elsewhere....

I have a basic stock shark and some simple suspention mods...and '89 vette wheels/tires and 2.5" VBP wheel adapters since '95 now....

I suppose you have read this over the years....

take care and have fun man....

MYBAD79 said:

So you want to move the front wheels "out" 1/2" ? Why are you saying you want to use another pair of 2.25" adapters? That would move the wheel way past the fender ???

Click to expand...

Sorry, poor wording in my original post. I've got 2.25" adapters in the back, and 1.75" adapters in the front. I am looking at buying another pair of 2.25" adapters to replace the fronts, giving me that additional 1/2 inch.

ok, now I get it.... test fit the rear spacers (2.25") on the front first to make sure it's the size you need....

Mike, way pre internet and anyone to talk to about it, in '95, I just looked at the wheel width and between 8" and 9.5" and wanting to keep same centerline as not knowing the affects of messing with that shit, I measured the wheels and ordered the 2.25 and 2.5" wheel adapters from VBP, they took my basic information and results to their web site and stuck on line, knowing to move the ebrake cable in rear, and limit the front with 255/50/17 on them....

I lament the next go round on tires in the rear, as 275/50/17 is NLA>...

but larger cheep rims are not going to happen, so I can't swap so easy, and the rubber is good to go for a couple years, anyway....

GENE

My only hesitation would just be how close the tires will be to the fender under heavy cornering. I love the way my car looks with the c5 five spokes and 3" adapters, but I do get very slight rubbing even with spirited street driving.

measure from rim mounting surface on rotor to edge of wheel well. Then take straight edge and lay on out side rim bead, then pop center rim cap and measure from straight edge to surface of rim to rotor mounting surface and this should give you a very close measurement of wheel adapter you need buy, by subtracting the measurement differences.

Just a couple of things you might want to worry about...

#1. If you use adapters to mount wider tires/wheels, you must be VERY careful about putting stress on them. As in doing holeshots and burnouts and popping the clutch. If you have an auto and drive like the granny down the street at 20 MPH all the time, this worry is much less. I have seen a bunch of adapter installations where the bolts and studs sheared off from stress of doing burnouts.


#2 An additional stress is put on the bearings when you mess with the centerline, as mrvette mentioned. See all those rice burners with the wheels with horrendous offests? They are tearing up the real axle bearings by putting stress on them that they weren't designed to handle and eventually they will fail with possible catastrophic results.

This could be you:

[ame]http://www.youtube.com/watch?v=jv4m41viy4I[/ame]

DJ Dep said:

Just a couple of things you might want to worry about...

#1. If you use adapters to mount wider tires/wheels, you must be VERY careful about putting stress on them. As in doing holeshots and burnouts and popping the clutch. If you have an auto and drive like the granny down the street at 20 MPH all the time, this worry is much less. I have seen a bunch of adapter installations where the bolts and studs sheared off from stress of doing burnouts.


#2 An additional stress is put on the bearings when you mess with the centerline, as mrvette mentioned. See all those rice burners with the wheels with horrendous offests? They are tearing up the real axle bearings by putting stress on them that they weren't designed to handle and eventually they will fail with possible catastrophic results.

This could be you:

http://www.youtube.com/watch?v=jv4m41viy4I

Click to expand...

DEP, there is a difference between a ADAPTOR and a SPACER, a simple spacer like the crap we see on the shelves, cast in China, and thin as hell, and made of some cheeeeeeeep material that shatters upon seeing light, don't get it.....

what I use for some years now is a billet? aluminum machined cut adapter that has all 5 bolts interleaved on the pattern, so it takes TEN lug nutz and TEN wheel studs to get the job done....they are stronger than the OEM wheels, easy....the reason for MY use of them was the later vette wheels were flat faced, and so to keep same centerline that was the calculation and to boot had to move the ebrake cable in rear, and limit the front steering radius by padding the snubs on the lower A arms....still tighter than a C4....

:drink:

Mike, I've got a couple different sets of those laying around. I don't remember the thickness, but if you want to try them for measurement they're available

TimAT said:

Mike, I've got a couple different sets of those laying around. I don't remember the thickness, but if you want to try them for measurement they're available

Click to expand...

Hey Tim, I appreciate the offer.
I did some additional measurements and it looks like a set of 2.25" adapters on the front, like the rear, will do the trick. I ordered a set yesterday, so we'll see how these wheels fit when the stuff gets here.

Thanks again!

The concerns you listed are pretty much a non-issue with correctly installed high quality adaptors. I have thousands of miles of both street and track driving using adaptors on my car. In all fairness, I did install ARP long wheel studs in the hubs, but otherwise, it's all stock.
As for the bearing load, it is relevant but most people think about it wrong. Just because you mount a 2.5" or 3" adaptor on your hubs doesn't necessarily change bearing load. If the width of the wheel is roughly the same as stock and the centerline of the wheel is located the same relative to the original design, there will be virtually no discernible difference.
For years now, I've been running a 9.5" rear tire (or larger) on my stock c3 hubs and still have no unusual bearing wear issues.
Now if you're running slicks and drag racing, I can understand your hesitation. But for a street tire, even sticky ones, under pretty much any other driving conditions, there are no issues.

Not sure what, but there is something hokey about that video. Catastrophic failure is one thing, but for all four wheels to come off? Fishy.

clutchdust said:

Now if you're running slicks and drag racing, I can understand your hesitation. But for a street tire, even sticky ones, under pretty much any other driving conditions, there are no issues.

Not sure what, but there is something hokey about that video. Catastrophic failure is one thing, but for all four wheels to come off? Fishy.

Click to expand...

Like I said, if you are running an auto and driving like granny, no problemo.

I WILL be running slicks and I have a stick. So driveline shock and stress are a real concern. Even still, no way I will run adapters on a car. Especially cast ones.