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Thread: How to change Wheel stud bolts(replacing a longer stud)

  1. #1
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    How to change Wheel stud bolts(replacing a longer stud)

    i'm planning to put spacers on my rear wheels to popout a lil more but the problem is i need long stud bolts which i just bought recently...

    how do i change my studbolts on my rear?what are the procedures?,..its a drum rotor by the way and my ride is a 78 corona rt100..thanks!

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    why not just run those common spacers with built in studs?
    -Matt

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    Quote Originally Posted by matt
    why not just run those common spacers with built in studs?
    its kinda expensive + i got 6pcs half inchers of spacers already just given by a friend so might aswell just use it since i have it already..

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    Depending on the wheel, you may not be able to use a bolt on type spacer for thicknesses of less than about 3/4 inch, because the original wheel stud and/or the nut used to hold the spacer onto the hub, may not clear the back of the wheel. If you are lucky, the wheel will have large pockets in the back of the mounting surface to allow for the needed clearance.

    For thicknesses less than 3/4 inch, the slide on spacers become the only option, and longer studs become a good idea.

    The longer studs were designed for racing, with some groups, like the SCCA, writing safety rules that require the use of an open ended nut, and that a certain length of threaded surface or a certain number of threads, be exposed past the end of the nut.

    The first thing you are going to have to do is find out if a longer wheel stud is even available in the same knurl diameter as what came on your car. This is the smooth diameter that the knurls project out from. This has to be the exact same size as the hole. You are looking for an inch measurement with three numbers to the right of the decimal place, and the precision is that important. Common sizes are for Ford, GM, and Chrysler, with some for Mazda Miata and Honda Civic.
    If your car doesn't match what is available, the only option is to make the hole bigger and use the next larger appropriate size stud knurl. This will require the use of a mill, do not try to drill out the holes with a drill press, they will not stay centered. Do not use a drill bit for this, buy a ream in the exact size from a machine tool shop.
    And, if you have to make the holes bigger, you will not be able to switch back to the original studs if you change your mind. You will either be stuck with the longer studs, or whatever length options may be available in the same knurl size.

    Installation may be as simple as pressing out the originals and pressing in the new ones. Probably requiring removal of the spindles from the car to put them on the hydraulic press. Or, if the backs of the studs are obscured, you may have to remove the hubs from the spindles, discard the wheel bearings (if they are sealed type bearings), and install new wheel bearings.

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    Quote Originally Posted by Daynger
    Quote Originally Posted by matt
    why not just run those common spacers with built in studs?
    its kinda expensive + i got 6pcs half inchers of spacers already just given by a friend so might aswell just use it since i have it already..
    Stacking spacers is suicidal. They will shift back and forth between the wheel and the disk/drum and back the nuts off the studs. Use only one spacer in the correct thickness. Make sure the center hole of the spacer matches the hubcentric ring and the lug holes match the studs. Do not use anything with slots or anything that is loose or sloppy. If you don't do it right, you're just creating an accident that will damage the car and probably injure you and several other people who will successfully sue you for everything you have and then some.

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    Quote Originally Posted by JT191
    The first thing you are going to have to do is find out if a longer wheel stud is even available in the same knurl diameter as what came on your car. This is the smooth diameter that the knurls project out from. This has to be the exact same size as the hole. You are looking for an inch measurement with three numbers to the right of the decimal place, and the precision is that important. Common sizes are for Ford, GM, and Chrysler, with some for Mazda Miata and Honda Civic.
    If your car doesn't match what is available, the only option is to make the hole bigger and use the next larger appropriate size stud knurl. This will require the use of a mill, do not try to drill out the holes with a drill press, they will not stay centered. Do not use a drill bit for this, buy a ream in the exact size from a machine tool shop.
    And, if you have to make the holes bigger, you will not be able to switch back to the original studs if you change your mind. You will either be stuck with the longer studs, or whatever length options may be available in the same knurl size.
    Question, do these two bolts look compatible to you?


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    Kostamojen, you may be asking a lot of Subaru to expect them to hold a consistent size for a part over 40 years of making cars.

    I don't know where to go to find the knurl dimension of a FF-1. This is probably going to be a similar problem for a lot of cars on this site.

    A lot of cross reference information can be dug up in catalogs, like Dorman Fasterners or ARP Bolts.

    http://video.arp-bolts.com/catalog/ARPCatalog.pdf
    Page 66
    The WRX studs from ARP show a knurl diameter of .565 inch and a knurl length of .270. Subaru changes a lot of suspension stuff between the different levels of Impreza. If they specify WRX and not "Impreza", then STi is probably different, and lends a little less hope that they backdate 40 years with one size of stud.

    ARP shows .565 for their Subaru WRX, Toyota Corolla, and Mitsubishi Lancer Evo 8. They don't cover all of any of those brands, and you can see that that there are a lot of other sizes, even their Lexus offering does not match the Corolla size.

    The importance of that knurl diameter is that the flutes are raised from that diameter to grip the spindle so that the stud does not turn when the nut is tightened and loosened. It has to fit correctly. Too big and it strips the flutes off going in. Too small and the flutes don't have enough grip on the sides of the hole. Either way, it would spin when you tighten and loosen the lug nits, and then you are trying to figure out how to drill it out and replace it without destroying the wheel.

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    The knurls are the grooved section that holds the bolt in the hub, correct?

    If that is the case, then yes they are the same diameter/number of knurls. The length is shorter as you can see, and the thread pattern is the same. Interestingly enough, Subaru has only used two or three different studs on everything from the 70's on. The FF-1 stud is the same as later 70's and even early 80's Subarus with drum brakes.

    So if the knurl diameter is the same, is the fact that the other stud may have longer knurls a problem, keeping the stud from going 100% into the hub?

    (sorry for the thread hijack)

  9. #9
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    Quote Originally Posted by Kostamojen
    The knurls are the grooved section that holds the bolt in the hub, correct?
    The knurl diameter is the the measurement of the round before the raised grooves or flutes is put into them. It has to be measured either before the grooves are raised, or next to the grooves where the smooth surface is exposed.
    The grooves or flutes are not cut into the studs with an abrasive tool. They are formed by pressing a collar around the smooth shaft which raises the grooves from the surface. This is similar to the difference between cutting threads with a die and the method of rolling threads used in bolt production.

    If you determine that the measurement is the same, and remember that is not close, but identical to the third decimal to the right, then look at what slides over the hub. The exposed flutes may or may bot be a problem. The newer stud looks like it has a different step down. Is there space for the disk or drum to slide on and off or does the larger diameter at the base of the exposed stud cause a problem?

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    I don't think there are any clearance issues with the stud sticking out a bit more on the back side, but I need to get in there and double check to be sure.

    Oh, and I don't have discs or drums on the hub (inboard brakes)



    I'm 99% sure the knurls are the same diameter (and the base of the knurl) but I don't have a super-accurate electronic feeler gauge to be sure.

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