doje

Lets talk about...

SPACERS...


and...

ADAPTERS...


I do a lot of Auto-X events, and I am in the process of flaring my car for cosmetic reasons. When I get back to Auto-X next year, I am considering using spacers or adapters to push my race tires out and make the car "look right". However, I have serious concerns about the stress applied to the hubs / bearings / etc.

Knowing some basic physics, it would seem to me that the further I push that wheel out away from the original mounting surface, the more leverage that will be applied (think about prying open a door with a short bar vs a long bar). How much potential wear and damage am I setting myself up for? Spacers are available for up to 1/2" or so (which doesn't seem like much) while adapters can easily go 2" or more.

Where do we draw the line under the serious strain of Auto-X on R compound tires?

vettehardt

What year of car do you have?

My situation is probably completly different than yours, but i have been running adapters for aobut 10 years now on my 73 and have never had an issue. I use the 3" adapters and run 16X9.5" C4 wheels. This car only sees autocross events and is never driven on the streets. Both my dad and i have driven this car, and we don't exactly take it easy. I also started running my 76 this year and used the same setup.

If you do use the spacers, make sure to get longer studs. With the adapters you won't need to have he longer studs since it already has studs on it.

doje

vettehardt, how many wheel bearings have you been through? I've never had to replace one. My '97 has 150k on it and runs about 150-200 auto-x laps per year.

flink

Moving the wheels outwards will increase hub/bearing stresses slightly, but only a little bit. Particularly on high-offset wheels like a Corvette's - the hub and bearing will still be pretty close to the wheel's longitudinal centerline.

Pushing the wheels outwards will also slightly decrease your wheel rate, softening the suspension.

Spacers just creep me out from a strength POV. A lot of BMW racers run surprisingly thick ones, but it just Seems Wrong. Adapters are far preferable, IMO - no reduction in strength at all if the spacer nuts and studs are as strong as the originals.

Adapters retain hub-centricity, whereas a spacer more than 6mm or so will start to lose centricity. I spent some time futzing with 1" spacers once, and wasn't able to get the wheel centered, to stop it wobbling. I got it centered one time, but it started to wobble after 2 miles.

Adapters might mean you'll need to shorten the studs. If the track wheels don't have voids in the back (many do) then the studs will need to be shaved to be shorter than the thickness of the adapter. That's easy enough to do - just hacksaw them off and put a chamfer on with a hand file. But the shortened studs can cause fitment problems when you switch to other wheels without the adapters. I solved this problem once with shanked lugnuts - the ones which have a threaded tube which actually pokes inside the wheel, all the way down to the hub.

worldsaway

The '84-87 C4's had a different offset than '88> and C5's. I run 3/4" spacers on my '87 BSP autox car so I can run the C5 wheels and I've had no problems. I've changed wheel bearings but the car has 115k hard miles. Ed

John Shiels

been running .750 & .850" front for many track miles and years with no problem. They spacers came from DRM and CCW. Rear 3/8" spacer

Maynor29

Some wheel spacers tech from a well-regarded non-Corvette road racing site:

gkmccready

IIRC the DRM spacers are machined to keep the hubcentric lips.

vettehardt

I have never had to replace one since I started running the cars. I did replace the fronts on the 76 when I did a brake job to it just after I bought it. The right front dust cap came off on the street somewhere allowing the greese to escape and fried the bearings. That was 3 years ago and I just started running the car some this year. The 73 has seen many, many hard autocross laps since 1995 when we put the car together. We run every NCCC event in the Indiana region plus a select few out side the region. We run one high speed event at Putnam Park every year. We started running the adapters from VB&P and C4 wheels around 1999. We have never touched the bearings on that car since it was put together.

vettehardt

The adapters on my car are needed to take up the difference in offset that the C4 style wheels have over the C3. I only need the 2" adapters to clear the suspension, but I use the 3" ones to help push the wheels out further.

jgalaxy

I don't know about other folks here, but after trying a stint with some spacers front and rear (10mm front and 5mm rear each side) at the track for my race setup, I have since decided to give that up. This summer I bought a set to help with a wider stance up front to gain a little better turn in bite on my BMW. Mounted with my race rims and Dunlop Direzza's, I had vibrations under braking with the spacers and couldnt get rid of it no matter what I tried. Towards the end of an open track day at Calabogie Motorsports Park the vibrations were just too much. I pitted and went to inspect what was going on and see if I needed to re-torque the lug nuts. Low and behold, 2 sheared lug nuts lay right next to where I had parked and a third was also sheared and lost to the wind. Likely another pass would have sheared the remaining two lug nuts holding on the wheel. Scary stuff.

I'm not saying this is going to happen to you, but maybe you might want to consider getting rims with the correct offset for starters.

Curious about other folks' experiences ...

Kubs

I run an 8mm spacer in the rear and have no issues. I need them to clear some of the suspension in the back and have never had a tire wobble or vibration problem. I had some spacers machined at work that are hub centric to replace the ones on the car just to be safe.

0Randy@DRM

That is some scary stuff. I can think of a few problems that may have happened. First off many wheel spacer companies don't think about heat and the growth of the material. IF the spacer grows too much your torque setting will increase to the point of breaking off studs.

Vibrations and funny things like that are caused by un-flat spacers and unversial spacers with the larger holes to fit all sizes. They flatout are scary and I will not suggest them to anybody. Because they actually move during driving.

Randy

jgalaxy

Pretty scary indeed. I'm just happy I trusted my instincts. You know it's so easy to say to yourself for something like that, "ah, I'll check it when I come in at the next group change". The vibrations were always there cold or hot and would manifest themselves at specific speeds. I tried to moving the spacers around twiced during the day hoping that I would find just the right spots to eliminate the vibrations. Never quite gone though. I'm assuming that the vibrations under heavy braking eventually just wore and sheared off the lugs. Interestingly enough the same spacers never hadn't posed any problems with my street rims. Just my track rims.

There is no substitute for rims with the right offset ...

bssofro

1) Did you use the factory TORQUE specs?

2) Did you use a calibrated torque wrench?

3) Was the car serviced at a dealer or other shop that had the rims off at some time or another where they might have used an AIR GUN set to MAX TORQUE, and maybe "streteched" the stud?

Glad everything worked out..and no one was hurt.

jgalaxy

Yup of factory torque specs, yup on calibrated wrench and no, dealer never touches my track stuff.

I'm sure it just had to do with my track rims not being the perfect match for the spacers.

worldsaway

i had a blazer that sheared off several studs before I finally realized the problem. The wheels were expanded at the lug holes, so I was tightening the lugnuts and barely contacting the wheel. The fact that the load wasn't on the wheel made them shear under pressure.

fatbillybob

Think about this for a minute... a spacer is no different than the mechanics of how your brake rotor stays on the hub.

Jason Staley

All new cars use slip on brake rotors .... looks alot like a spacer. Don't really see how there is a difference as long as the spacer is a machined spacer and not one of those cheap cast ones (seen those break apart).

doje

Think of a pry bar. The longer the handle, the more leverage you have. A spacer, by moving the wheel further from the car, causes more leverage to be applied. The question is, how much is too much? I guarantee that a three foot spacer (adapter) would rip the hub right off. A 1/4" spacer is no issue. The $64,000 question is, where is the line between OK, and NO WAY?