Wheel Spacers

[Gippetto]

I need your expert opinion. I am about to select wheels for my 47 GMC. The width of my rear end is not wide enough to host most wheel choices. I am trying to avoid tubs or custom backspacing and accommodate a wheel with 4" backspacing. I can to it using 1-1/2" spacers. I will certainly use a quality spacer but don't like the idea.
What do you think?

[Robert Haas]

Depends on application and duty.

If you have less then 250 HP at the rear wheels, plan on not putting 1200 Lbs in the bed or tow a large trailer, you will be fine.

Exceed any of the above mentioned chores,.... I would pass on the spacers.

[Dan in Pasadena]

Robert, NOT disagreeing but where did those particular values come from?

[Robert Haas]

Originally Posted by Dan in Pasadena

Robert, NOT disagreeing but where did those particular values come from?

Wheel spacers and the companies that make them are not under any industry standards. Therefore us users need to use industry standards of similar classifications.

That said I have been building hot rods for 50 years and have a decent amount of experience to pull these "Specs" out of my butt.

[MARTINSR]

Originally Posted by Robert Haas

Wheel spacers and the companies that make them are not under any industry standards. Therefore us users need to use industry standards of similar classifications.

That said I have been building hot rods for 50 years and have a decent amount of experience to pull these "Specs" out of my butt.

I think they are a damn good way to look at it if nothing else. They are "usable" but you have to use your brains and not ask them to do too much.


Brian

[Gippetto]

You can't beat this forum. Where else can you get almost instant responses, challenges and constructive dialog between posters.

I will go with the spacers based on the advise and Robert's design criteria. And to Mr48chev , I have a few "high end" spacer mfrs in mind so it's not necessary to search, thanks.
By the way, I spent my career as a design engineer and I can say that I used the same database as Robert more than a few times.

[mr48chev]

I'm not a fan of the spacer/adapters but if you need to run the do your homework and find out which ones have the best reputation for quality. Then spend the money and get the good ones.

I was looking for some for six lug wheels to run early Chevy wire wheels on AD pickup axles a while back (ot roadster project) an found some quality billet ones available that were US made. No time to look right now and find the link but when I get time I'll try to hunt for it.

[Dan in Pasadena]

Robert, thanks. I totally agree that we all should use some (not so) common sense when selecting parts for our cars. Afterall, our cars/trucks are essentially one-offs. They're custom built vehicles to a greater or lesser degree.

I also like your admission of pulling these spec's from a fragrant area as I frequently do too. When I give someone some of my free, unsolicited advice I always tell them I hope they treat it In accordance with it's value, lol.

Best, Dan

[jweb]

I would only use hub centric wheel spacers. I originally had a cheap ebay set on my truck and I had quite a bit of vibration at higher speeds.

I ordered a set that centered perfectly on the axle and wheel from here and noticed a big difference.
http://www.motorsport-tech.com/wheel_adapters.html

[BIGglaSS]

Originally Posted by jweb

I would only use hub centric wheel spacers. I originally had a cheap ebay set on my truck and I had quite a bit of vibration at higher speeds.

I ordered a set that centered perfectly on the axle and wheel from here and noticed a big difference.
http://www.motorsport-tech.com/wheel_adapters.html

Same story. I had a set custom made by motorsport-tech, and another set of cheap ebay ones that came with my truck. I consider the cheap set nothing more of a means to bolt a wheel on so I can move it around my garage. The custom made set looks higher quality with nicer studs.

[dsraven]

the things I would think about would be
-would a different offset wheel be better and stronger for somewhere near the same cash

-do I need to upgrade the wheel bolts to handle the extra stress

-will the spacer affect the steering geometry. if there were an imaginary line drawn through the axis points of the upper and lower ball joints and extended through below ground level, and another imaginary line was drawn through the centerline of the wheel mounting surface, these 2 lines should intersect at the contact patch of the tire on the ground. this is called centerpoint steering and that way the tire scrubs a perfect circular patch on the ground when the steering is turned (vehicle at ride height and not moving). if the tire size is changed or the wheel mounting surface is relocated then the tire will roll in an arc around that scrub patch. it could affect steering, braking and handling characteristics. your alignment guy may need some details for a better alignment and possibly play with the caster angle. a lot of positive scrub radius will increase steering effort and possibly more kickback on bumps. you have more steering "feel" though. it could also take the steering wheel out of your hands if you had a tire blowout.
google kingpin inclination, some call it swivel/steering axle inclination (SAI). also google slip/scrub radius.
here is a little write up that can explain scrub radius better and how it can affect steering etc.
http://www.moderntiredealer.com/arti...offset-matters

below is something I pasted from a jeep forum on the subject of wheel offset. bear in mind that front wheel drive angles are a little different than rear wheel drive. hope this helps somebody out there.
-----------------------
For those who are into this sort of thing, I found a helpful explanation of how changes in scrub radius impact handling posted by someone going by the username "goldstar" on what appears to be a Mazda Protege forum. Posted below for reference.


Effect of Wheel Offset Change on Scrub Radius

Effect of Wheel Offset Change on Scrub Radius
One of the mods sometimes considered when switching to aftermarket wheels involves using a rim with less positive offset than OEM for the purposes of increasing the vehicle's track and, for those who think it enhances appearance, filling out the wheelwell. Assuming that either tire/fender interference is not a problem, or has been resolved, changing the offset of a wheel will change the scrub radius of the tire/wheel combination.

Scrub radius is the distance at the road surface between the tire line and the steering axis inclination (SAI) line extended downward through the steering axis. SAI is an imaginary line, that on strut suspensions runs through the lower ball joints and the upper end of the strut. The line through the steering axis creates a pivot point around which the tire turns. If these lines intersect at the road surface, a zero scrub radius would be present. When the intersection is below the surface of the road, positive scrub radius results. When the lines intersect above the road, negative scrub radius occurs. The point where the SAI line contacts the road is the fulcrum pivot point on which the tire is turned. One of the main effects of SAI is to promote directional stability, the tendency of a wheel to straighten from a turned position and remain straight. SAI is not adjustable on most vehicles and is usually only affected by loose, worn or damaged suspension parts or by frame damage.

Characteristics of Different Types of Scrub Radius
At zero scrub radius, the car steers easily and will have little or no kickback from bumps. At the same time there will be virtually no road feel or feedback and there will be a feeling of directional instability while cornering due to the tendency of the tires to squirm. This condition is also known as center-point steering.

A positive scrub radius will increase steering effort, torque steer and kickback on bumps to a considerable degree. At the same time, a blowout or a failure of one front brake could yank the wheel hard enough to pull it out of your hands. The advantage is that there is much greater road feel and feedback so that you can feel when the front tires start to break loose in a corner. Consequently, this is often the set-up of choice on race cars.

Negative scrub radius will also increase steering effort, torque steer and kickback but to a noticeably lesser degree than the positive kind. Additionally, front tire blowouts and single brake failures will act with less force on the steering wheel. Finally, there will be less road feel and feedback and less ability to feel when the front tires are about to break loose as compared with the positive state. In general, front-wheel drive cars are set-up with negative scrub radius.

Incidently, the term scrub radius derives from the fact that either in the positive or negative mode, the tire does not turn on its centerline (it scrubs the road in a turn) and due to the increased friction, more effort is needed to turn the wheel.

A significant reduction in positive offset of the wheels will EFFECTIVELY change the steering geometry's scrub radius, possibly increasing the steering effort and making the car harder to control during turning and cornering. As already stated, SAI is not adjustable on most cars so alignment changes may not be adequate to compensate for changes in scrub radius. That being said, I have no idea how much positive offset would have to be reduced for the change to be considered significant. It's just something to think about, particularly for those of you who consider your cars to be primarily daily drivers.

Reference:
Alignment Terms - Ingalls Engineering Co., Inc.

[mr48chev]

I agree that they need to be hub centric rather than lug centric.

This outfit is in Lubbock and will make hub centric wheel spacers to Order. 35.00 additional charge per spacer but worth it I would believe.
https://www.uswheeladapters.com/wheel-spacers/

[Gippetto]

I placed an order at US Wheel adapter. They seem very competent. The spacers will be custom machined and both hubcentric and lug centric with center bore being machined to drawing supplied by wheel company. They will have metric mounting to rotor and US to wheel. Hope they work out as good as they sound.
Thanks for the tip, Mr48chev.

[Gippetto]

Lots of information, thanks dsaven. Another thing to worry about although, in my case I am using spacers to get the wheels out where they clear the bed sides after swapping out the rear end for a narrow one. I would think that would approach the stock geometry. That and add a mustang 2 ifs you are on you're own as to outcome. Reading this forum regularly for years now, I never saw the problem come up. Maybe we just struggle with the outcome where we are changing stuff somewhat blindly in many cases.

[1952ssr]

I bought my 2 inch spacers from Ecklers back over 15 years ago to run 17 inch vette wheels on my S10 2wd blazer Typhoon clone. They were pricey back then! I have ran them on 3 different S trucks for more than 10 years.

[dsraven]

if you are just using spacers on the rear it's no biggie. check the original studs to ensure they are long enough to accomodate the thickness of the spacer. you want that bolted up well. try to get a hubcentric spacer.
post up some pics, always curious to see wheel choices.

[Gippetto]

The spacers just arrived and they fit perfectly. Both hubcentric and lug centric with the bore for the wheel matched to manufacturer's drawing. That was the good news. The bad news is the wheel studs are not long enough to fully tighten , torque the spacers. One nut started to strip as I was snuggling up on it. Need about 1/2"longer studs. Any suggestions where to source them?

[dsraven]

try napa.

[BBPanel]

Originally Posted by Gippetto

The spacers just arrived and they fit perfectly. Both hubcentric and lug centric with the bore for the wheel matched to manufacturer's drawing. That was the good news. The bad news is the wheel studs are not long enough to fully tighten , torque the spacers. One nut started to strip as I was snuggling up on it. Need about 1/2" longer studs. Any suggestions where to source them?

You bought "spacers" or "adapters" - there is a difference but most use the terms interchangeably.

[jweb]

Originally Posted by Gippetto

The spacers just arrived and they fit perfectly. Both hubcentric and lug centric with the bore for the wheel matched to manufacturer's drawing. That was the good news. The bad news is the wheel studs are not long enough to fully tighten , torque the spacers. One nut started to strip as I was snuggling up on it. Need about 1/2"longer studs. Any suggestions where to source them?

You can get new studs at Napa but you may want to contact the manufacturer of the spacers. They may replace them for you or at least they can give you the specs on the studs that are in there. Replacing studs in aluminum may be a different deal.