Help Needed On Offset and 4 to 5 Lug conversion

[Temujin]

I've been reading as much as I can but being very new to restoring cars, finding the info I need isn't as easy as I hoped it would be.

 

I've tried real hard to search and find the answers I need to address my concerns but I just can't seem to find exact answers to what i need so i'm taking the chance (and the risk of getting quite a few "do the search" comments) in hopes of getting help fast.

 

Scenario: We're halfway done with the RB20 swap part of the restoration project and the plan is to move on next to bodywork and painting. First thing we need to do now is buy the rims and tires so we'll know how much to cut and how wide we need to extend/widen the flarings. I want to put 245 tires in front and 275 in the back and i'm in the process of looking for rims that'll allow for that. Per my research, I have to get rims 8" wide in front and 9.5" rear.

 

The stores that sell rims keep asking for the offset. I've researched and now know what offset and backspacing mean. The thing is, the rims currently installed aren't stock anymore and I don't know if they were a proper fit on the car when I bought it (we never got to road test the car) so giving the offset on the current rims isn't exactly definitive as they could've been a wrong fit. I would rather get the rims/tires now so we can start the flaring-extension job and not have to wait for the engine swap to finish and drive the car to the rim store.

 

My questions are:

 

1. What offset do I tell the salespeople at the mags store? Is there a stock offset to live by? All i've gotten from my search is that stock is 4x4.5

 

2. If I decide to opt for the 5 lug variety, what do you think of some guy's suggestion that I simply need to fabricate adapters (that can serve as backspacers too) that we'll bolt on to the stock 4-lug assembly. Is it true that this is as safe as changing the whole assembly to that of an original 5-lug one. I don't know if this question makes sense ... it's hard to ask questions when one doesn't know the proper terminologies.

 

3. We'll be extending the flaring as much as needed so the outer part shouldn't be a problem. What do I need to look out for in the inner part? Are there concerns about the inner part of the tire hitting anything inside (like the shocks I suppose)? With such wide rims/tires, do I automatically need to change the shocks/springs?

 

Really looking forward to helpful comments and suggestions. Please feel free to add anything you deem will prove helpful in this project.

 

Thanks in advance.

[Dudeboy]

I have been looking at my wheel/tire options for quite awhile, and I am glad I did not buy when I had the money to do it. Too many things to consider:

1. Purpose of car 2. Suspension and brake setup 3. Bodywork if needed (flares and what kind). 4. Money--How much do you want to spend.

 

1. 4 lug x 4.5 is your bolt pattern. Off hand I do not have the stock offset/backspace info, someone will chime in with that info. Have you installed larger brakes? Are you running coilovers or stock set-up with performance spring/strut? Are the flares already installed ? Here is a way to measure backspace based on the rims you already have (hopefully they were within optimum tolerances) ?http://www.carcraft.com/techarticles/ccrp_0610_muscle_car_performance_wheels_fitment/index.html

 

2. I have only seen 4 to 5 lug adapters in a two piece design, it can been done but you have to do your research on the pros and cons. I decided not to do it based on safety concerns, could not get a consensus answer if they should be hubcentric versus lug-centric or to use blue or red Loctite

when you install them. Again purpose of car, Show car ? Race car? Street/Race Car -You have to do your research and decide if this is the route you want to go. In my opinion, I do not think two piece 4 lug to 5 lug adapters are safer than having original 5 lug hubs IN MY HONEST OPINION.

 

3. Two answers to this one. You can build your car around the wheels you are buying, or install your flares, brakes and suspension first, then make your measurements and measure again then go out and buy the wheel/tire combo that clears bodywork ,suspension and brakes. If you underdstand backspace/offset, having coilovers or modifying the spring perches allow for more backspace and positive offset. Are you having wheels built to your specs? Are these ready made or warehouse stock with generic offsets, backspace and lug patterns?

 

If you know you specs and measurements, and come across a good deal you should not pass it up and buy your wheel/tire combo. I want tell you to "search" but I re-read and re-search because of small tid-bits I may have missed just by changing a word or two in my search query.

 

Good Luck

[Temujin]

Much appreciated, Glenn!

 

1. I'm 99% sure the car is stock inside and out except for the current rims. The plan is to get better (bigger) brakes since i'll be running a more powerful engine in the RB20 vs the stock 2.4L. My mechanic advices that we change to gas shocks and put fatter (that's the way he puts it) springs. This all sounds foreign to me but that's pretty much what i remember him saying.

 

2. Car will be used as a daily driver to and from the golf course (approx 30 kms total) but there's a nice kilometer-long stretch of open road that'll allow for some very spirited driving so I should get my daily dose of adrenaline-pumping blasts This is why I want to make sure the seemingly simple solution of using a backspacer that doubles as a 4-lug to 5-lug converter is really a viable one. I understand that having original 5 lug hubs is the safest way (also apparently a much more difficult endeavor) to go but am I right in understanding that going the adapter route should be ok if the car is meant for street use albeit relatively fast street use?

 

3. I really want rims of negative offset that'll allow for 245 f and 275 r so i think i'm going for rims/tires first then setup the flares, brakes and suspension accordingly. I'm gunning for a look similar to the rims on the red car below although i'm discovering that finding rims is far from easy after all I hope those rims aren't made-to-order as I'm pretty much stuck with choosing from whatever's already out there. What other rims sport similar features to those of the red car?

 

 

Trust that I haven't stopped searching here and on other sites for answers to my querries. I know I can trust my mechanic but I want to be a lot more knowledgeable about this whole project and take an even more pro-active role in the restoration process.

 

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By the way, I can't remember where I got them but these 2 figures helped me understand offset and backspacing. Maybe it'll help someone else.

 

[Dudeboy]

Right now I am not doing coilovers, but I have installed the Tokico springs/struts. Shocks, Springs and bushings will improve the ride quality/performance. Here recently, I have found that Porsche's, some large trucks and some the members here have wheel adapters from 1.5 inches to 4 inches thick, but they are one piece 4 lug to 4 lug, 5 lug to 5 lug and 6 lug to 6 lug adapters.

 

I think Aziza had some problems with his recently, and I have seen a BMW failure on Youtube. But, made with quality, fitted and installed correctly there are no issues. The 4 lug to 5 lug may work well on the street (spirited driving), I would be thinking about my wheel falling off too much, to enjoy the drive !!!!!

 

That car is one my favorites Zs', Those wheels are Weld wheels and they are not in the catalog anymore. I only know of two companies that make a will that is similar to those, Bogart and Kodiak wheels. And yes Made to Order !!! Cost a few bucks but worth it. Finding wheels is actually easy, it really comes down to how much money you are willing to spend. Kinesis, HRE, I-Forge all the stuff I like, two wheels will cost more than I paid for the car. Right now I a leaning towards Complete Custom Wheel and I plan on having a negative 40 to 55 offset on the rear between 11-12 inches wide, the fronts will be neutral to -16 on a 7.5 to 8 inch wheel. 17 inch tires are fairly price right now, but I am looking at some 18 and even 19 inch tires !!! Playing with plus 3-5 wheel calculators. If you find something out there in 4 lug please post.