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Spacers versus more rotating mass?

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    #16
    Originally posted by kaivball View Post
    Thanks for the feedback.

    I would have to find a light weight 15x7 4x100 with zero offset. Which doesn’t change the overall physics but at least all bolts are visible.

    Right now the wheels have +25 offset and need a 25mm space or they will make contact with the caliper.

    The wheel and tire package is ~33lbs (225/45/16 Direzza ZIII).

    The 17x7 rim and tire combo weighs ~40lbs but clears the caliper and doesn’t require the 25mm spacer.

    And it is for an endurance track car.

    Kai
    What is driving the geometry of your E30 setup to be so odd?
    Jimmy P.
    87 E30 M3 Prodrive British Touring Car
    88 E30 M3 Zinnoberot - Garage Queen
    88 E30 M3 Lachsilber - SCCA SPU #98
    92 M Technic Cabrio - S14 Powered!
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      #17
      Can you get a 2D clearance diagram from the brake manufacturer? When I was shopping for wheels, I sent one out to a couple companies to check for wheel to caliper clearance. Are you dead set on the set of 15's you've already picked or somewhat flexible? Personally, I'd pick the wheel based on the required diameter and width for the tire you want to run, not the other way around.

      Also, I'm with Nando on the physics of the wider wheel spacers. I don't see why it would be an issue. Longer stud length is better for maintaining clamp load anyway. The anti-rotation load shouldn't be carried in shear of the stud, it should be the friction between the hub & spacer / spacer & wheel. The main issue with running a spacer is that you're increasing the moment at the hub/bearing and increasing force on the LCA. It's more a function of the distance from contact patch to hub, rather than running a spacer or not. A wide wheel with a negative offset creates the exact same forces.
      Last edited by citizen_insane; 02-11-2019, 03:16 PM.

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        #18
        We're talking about an inch of increased moment (leverage). In engineering terms, that's rounding error. And it doesn't take into account the base hub center of the wheels. People do dumb crap like run ET0 wheels with adapters. That's way more leverage than a spacer.

        Feelings, thoughts, it's all bs. The difference between a 15mm and a 25mm spacer is meaningless and the comfort threshold is completely arbitrary.
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          #19
          Originally posted by JimmyP View Post
          I would avoid 16"s at all cost. The selection of track tires in 16" that are a good height for an E30 is 0
          Depends on your definition of "track tire." These are almost the exact same rolling diameter as the stock weaves on an iS.
          Originally posted by kronus
          would be in depending on tip slant and tube size

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            #20
            Originally posted by agent View Post
            Depends on your definition of "track tire." These are almost the exact same rolling diameter as the stock weaves on an iS.
            Thats not what I had in mind when I referenced track tires, but I know that lots of people do use those for a track tires these days.
            Jimmy P.
            87 E30 M3 Prodrive British Touring Car
            88 E30 M3 Zinnoberot - Garage Queen
            88 E30 M3 Lachsilber - SCCA SPU #98
            92 M Technic Cabrio - S14 Powered!
            98 318Ti Morea Green
            04 Ford F350 Dually Tow Machine

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              #21
              Originally posted by nando View Post
              We're talking about an inch of increased moment (leverage). In engineering terms, that's rounding error. And it doesn't take into account the base hub center of the wheels. People do dumb crap like run ET0 wheels with adapters. That's way more leverage than a spacer.

              Feelings, thoughts, it's all bs. The difference between a 15mm and a 25mm spacer is meaningless and the comfort threshold is completely arbitrary.
              Me personally on a track car / race car, I'd just get wheels that actually fit.
              People can "do" all sorts of spacers and / or adapters.
              Im not, nor would I ever recommend someone to run 1" spacers on a race car.
              I'd fix my car first so that I dont need 1" thick spacers.
              Jimmy P.
              87 E30 M3 Prodrive British Touring Car
              88 E30 M3 Zinnoberot - Garage Queen
              88 E30 M3 Lachsilber - SCCA SPU #98
              92 M Technic Cabrio - S14 Powered!
              98 318Ti Morea Green
              04 Ford F350 Dually Tow Machine

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                #22
                If you're doing W2W racing in an E30, you're probably running a spec tire and not 16" wheels anyway, and probably a spec wheel that just fits like you said.

                for an HDPE, daily driver, whatever - it's nothing to worry about.

                I didn't know they still made the RT615. Was a great tire back in the day.
                Build thread

                Bimmerlabs

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                  #23
                  Yeah, I think the Hankook RS-4s are better but the Azenis are still perfectly serviceable for track days and relatively cheap.

                  A 200 tread wear rating is the minimum for ChampCar Jimmy, that's what I had in mind when I posted that one.
                  Last edited by agent; 02-12-2019, 10:02 AM.
                  Originally posted by kronus
                  would be in depending on tip slant and tube size

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                    #24
                    Originally posted by agent View Post
                    Yeah, I think the Hankook RS-4s are better but the Azenis are still perfectly serviceable for track days and relatively cheap.

                    A 200 tread wear rating is the minimum for ChampCar Jimmy, that's what I had in mind when I posted that one.
                    Yeah its a whole different world out there with the numerous 200TW tires race series.
                    They are not something I think about when I think about track tires, my mind goes to the old standard of Hoosiers, Goodyears, BFGR1, Toyo, etc. but I know that lots of guys are using the 200TW street tires as track day tires as well as the race series that spec that 200TW rating.
                    They do seem pretty impressive for what is considered a street tire.
                    Jimmy P.
                    87 E30 M3 Prodrive British Touring Car
                    88 E30 M3 Zinnoberot - Garage Queen
                    88 E30 M3 Lachsilber - SCCA SPU #98
                    92 M Technic Cabrio - S14 Powered!
                    98 318Ti Morea Green
                    04 Ford F350 Dually Tow Machine

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                      #25
                      Originally posted by nando View Post
                      If you're doing W2W racing in an E30, you're probably running a spec tire and not 16" wheels anyway, and probably a spec wheel that just fits like you said.

                      for an HDPE, daily driver, whatever - it's nothing to worry about.

                      I didn't know they still made the RT615. Was a great tire back in the day.
                      Originally posted by agent View Post
                      Yeah, I think the Hankook RS-4s are better but the Azenis are still perfectly serviceable for track days and relatively cheap.

                      A 200 tread wear rating is the minimum for ChampCar Jimmy, that's what I had in mind when I posted that one.

                      We have been running the 615k"+" since they came out a few years ago - they are softer than the 615, for sure as I had new a set of each at the same time.



                      This time around, we tried the Maxxis VR1 and they are even stickier. One of our friends did a back to back at Sebring with the 615+ vs the VR1 - same car, same day, three hot laps each and the VR's were worth almost 2 sec with an extremely talented driver. I liked tham, and they are actually a little cheaper than the 615's when buying direct from the MFGR.
                      john@m20guru.com
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                        #26
                        We ran that Maxxis tire in a couple of events when they came on as a contingency sponsor (in 2017?). It's a good enough tire for short runs but they fell off pretty significantly when pushed ,and were overly sensitive to pressure adjustments - IMO of course.
                        Originally posted by kronus
                        would be in depending on tip slant and tube size

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                          #27
                          Mechanically, there is no difference between a given wheel with the wrong offset and 1" hubcentric spacer to make up for it and the wheel with the correct offset unless you don't torque your nuts adequately. The clamping loads are immense, thus the friction is immense and the forces involved are far too small to cause the spacer or wheel to slide on the hub let alone deflect the metal spacer itself. Having a spacer isn't going to overload the hub, if the center of the contact patch is in the same place as a stock setup it makes no difference at all a even in scrub radius. If the tire is further out



                          Then you're changing scrub radius, wheel rate, and putting more load on the hub.
                          Last edited by varg; 02-13-2019, 08:47 AM.

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                            #28
                            Now that's a spacer I could recommend to anyone! haha.
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                              #29
                              Lol!
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                              OEM v8 manual chip or dme - https://www.r3vlimited.com/board/sho....php?p=4938827

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