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Wheel fitment-mock up


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I'm trying to have some custom 15" steel wheels made for landspeed racing. I contacted Marsh Racing Wheels (MRW) and they sent me a 15x8 barrel, a 15x4.5 barrel and a 4x114.3mm bolt pattern wheel center. I am to mock up a set of wheels combining their center and each barrel in order to know exactly how much offset is needed to clear my AZC brakes. Then, I send the parts back to them so they can weld them up, put dzus fastener tabs on for moon discs, powder coat them and send them back. So much goes into how a wheel fits, from the design/profile of the center, brake clearance, and barrel valley design. I hope I don't need spacers, but when the caliper protrudes 3/4" out from the hub face it is hard to predict what is going to fit. I post this to say: "Don't be afraid to ask wheel builders to work with you." Will mock up this weekend and follow this thru to completion or failure. So far I have $132 invested.

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  • 2 weeks later...

The issue in trying to fit 15" wheels over AZC brakes is that for strength, the inner diameter of steel rims necks down-this part of the wheel is called the valley. In the case of 15" MRW wheels, the valley is only 12" in diameter.

MRW wheels look like they are made from a basic stamped center welded to a rolled and welded rim, or barrel. There are several wheel makers selling wheels made from these mass produced kits: Aero, Diamond, Bassett. I can't be positive that they get their components from the same place but it sure looks like it.

I am not real happy with the stamping of the center where the wheel bolts to the hub. These centers look just like the center of the wheels that a fellow forum member was running who recently experienced a hub failure. The centers are stamped and they certainly are not flat where they contact the hub.

I think the fronts would work if I overlook these issues. I found that everything on the 4.5" wide wheels cleared the brakes with a 1-3/16" back spacing. Because of the un-flat centers, I would plan to run a 1/2" spacer and increase the back spacing to the max these valleys could handle at 1-11/16".

The rears were another matter altogether. The valley placement on the 8" wide barrels only allows for a 3-1/2" back spacing. I need 4-1/2".

So what to do? Does anybody know of a wheel shop that can narrow steel wheels and weld them together? Perhaps I could get a wider barrel that has more back spacing to the valley. Then maybe I could have some valley width removed to wind up with an 8" wheel....

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Edited by RebekahsZ
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Went to local Z boneyard. Got suckered into bringing home a couple of nice looking steel rims that measured 15" across the rim and looked just like 240z stock wheels with a hopeful looking backspacing. They had no tires to confirm diameter. Crap, they were exactly that-stock 14" Z wheels.

 

Wound up dragging home a single 15" wheel and tire from a 93 240sx. Haven't test fit them but they have 5-1/4" backspacing. That would work with a 1/2"-3/4" spacer...but will need widening for the back and narrowing for the front. Plan to add pics tomorrow and contact stocktonwheels this week to see if they can help.

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Photos added to second posting.  Especially after I went to the junk yard and looked at the quality of an OEM 240z 14" steel wheel and an OEM 240sx 15" steel wheel, I wasn't satisfied with the quality (maybe just my perception of the quality) of the center of the aftermarket wheel.  What I saw in the OEM wheels had cleaner mounting bolt holes, a flatter mounting surface, and more complicated stamping patterns that I think create a stronger, more rigid wheel.  I had a good conversation with Rick at Stockton Wheels, and he indicated that they can often put a 15" barrel on a stock 14" center, and that making custom steel wheels specifically to clear hot rod disc brake set ups is something that they do with regularity.  I am to send him some photos of the OEM wheels and my AZC disc brakes set up via email to get things started. I discussed this with Burton Brown and he said that he will be at Bonneville (when I am also there) running his streamliner. He says that his streamliner wheels were custom made by Diamond Racing and that they have a booth at Bonneville.  That's in 2 weeks, so I hope to lay some eyes on the Diamonds to see if that is an option.  Will post the photos that I take in the next few days to send to Stockton.

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So, I trial fit both the stock, steel 14" 240z wheels and a set of 1993 steel 240sx wheels hoping to be able to send the centers to a custom wheel shop. Thats gonna be a big no-go, the centers are way too small for the same reason that the MRWs wont fit-its the valley in the barrels that is the problem.

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Went to storage and got my 15X7 Rota RBs.  Turns out that they clear the AZC calipers.  The front clears by about 1/8" everywhere with no spacer.  The rear needs a 1/2" spacer and clears by about the same amount-not very much.  I'm going to the speed shop to get a set of Weld Rodlite wheels which have crazy slotted bolt holes which look like they take an insert to change them from 4X4.25 to 4X4.5.  But the Rodlite is a cast wheel, so I'm hoping that they gobble up less wheel stud length.  I will also get a pair of 4X4.25 Bogart front wheels to see if they can be run with my 4X4.25 to 4X4.5 spacer adapters-fortunately, with only 3.5" wide front wheels, there is more room for playing with backspacing.  Will report back.  If the other wheels do not fit, then my plan is to order some 15X8 RBRs for the rear and to try to have my 15X7s narrowed for the front.  I have about 2 weeks to decide whether I am buying 15" or 16" drag radials.  I hope to run 275/60/15 Drag Radial Pros, back up plan is to run 295/50/16s.

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Edited by RebekahsZ
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  • 2 weeks later...

Had a good talk with Rick at Bogart Racing Wheels yesterday.  Will send him my measurements; he is a good listener and seems to understand the issues.  I think I'm giving up on steel wheels.  I picked up some 2-1/2" backspacing 3-1/2" wide front wheels this week at the local speedshop for $100 a piece.  A machinist just quoted me $100 to have 4-4.5 bolt holes drilled.  So that is a set of front wheels that should fit (can't be sure till they are drilled).  One was straight as an arrow on the spin balancer, the other was not as straight, but I think it is still good enough.

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Edited by RebekahsZ
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