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MiniTec front suspension bumpsteer

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  • MiniTec front suspension bumpsteer

    okay so here's the problem: Minitec's bespoke front suspension is rubbish. it produces tons of bump steer no matter how well you adjust it. the problem is that once the wheel is lifted up it does not hold it's vertical alignment, so if the road is not perfectly flat it drives like shit and can be dangerous (car goes to sides without any steering input)

    as of now I own 2 minis with minitec frames:
    - B16A2 based on old MTB1 frame (btw currently for sale)
    - D16 based on MTD frame

    I did not build any of these cars and I'm not too tech savvy so I need help: the thing is that my MTB1 mini have bumpsteer fixed https://www.youtube.com/watch?v=7c8yIxywiP8 and I would like to fix it on the D16 mini too. all I know is that on the B16 they welded some parts together, not sure which and how. so my question is how would you solve this? take both cars to some suspension specialist so that they could look what has been done and do the same? I'm sure MTB1 frame had bumpsteer before it was fixed as here is also MTB1 mini and tester says it bumpsteers like hell https://youtu.be/BO42hTCa3NM?t=110

  • #2
    In Video 1 as the car is raised and lowered both steering alignment and camber change fairly considerably. Assuming that no parts are broken, loose or bent, it means the suspension design is pretty bad.

    When I designed and made my frame for Vauxhall engine, I revised all the suspension pivot/ pickup heights. This was to get the engine into the frame and car without anything poking out of the bonnet etc. Because this meant that the relationship between them and the steering rack was now different, it increased bump steer. I cured this by measuring it and plotting the bump curve. I used the laser level , Perspex and mirror method and plotted the curve on the Perspex with dry wipe markers. You really need to see the curve to see what shape it is and to see over what suspension travel it occurs. When rectifying the problem, you are looking to reduce the tracking / alignment change to as low as possible over the most normal operating range. It is almost impossible to totally lose all bump steer and that should have been tackled at design stage on the kits you have.

    With the car set up for measuring you can add spacers to adjust the steering arm pick up height and drill through the taper and use good quality bolt with nylock. The only other alternative is to change height of steering rack, but that is much more involved.

    Check everything is good on the car first in steering and suspension. Best to get a spare set of steering mini arms, unless they are different on minitec? I seem to remember on MINITEC the arms were hollow and failed really badly on a few members cars. Look into that.

    2nd Video the guy is talking about Bump steer then torque steer. It's hard to tell what is actually going on.
    Whale Oil Beef Hooked!
    (use Irish accent)

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    • #3
      well as mentioned I have 2 minitec honda minis and the one with "suspension design is pretty bad" is the WAY better handling one. so there you see how bad the stock minitec suspension is. I have no video of the MTB2 but here's a photoshop impression how it would behave when lifted up

      anyway, any idea what parts my be welded so that it does not happen in my modified mini?
      Attached Files

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      • #4
        I just looked at the kits on superfast minis.com http://www.superfastminis.com/store

        Nothing needs welding? Both the top and bottom suspension arms are rose jointed throughout. What I believe is happening is that the top arm and bottom arm are not travelling through the same arc as the suspension rises and falls. First contact Superfast Minis in the USA to discuss. I think you need to measure and adjust the rose joint engagement on the arms to get them all the same. Speak to the manufacturer / retailer firstly though
        Whale Oil Beef Hooked!
        (use Irish accent)

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        • #5
          sadly they're not too responsive

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          • #6
            If your b16 mini has already been fixed and “had bits welded together”, could you not just take a wheel off and have a look to see what (if anything) has been welded?

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            • #7
              I can't say anything about the MTB kits, but my MTD had pretty bad torque steer at first, I don't think bump steer was ever an issue. I think mine was the second or third D frame that they made. They replaced the steering arm with a redesigned piece (I think. It's been a quite a few years) and it's been straight and true ever since. No bump or torque steer issues at all.

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              • #8
                can we define what bumsteer is? my mini drives terribly when road looks like attached pic. what happens is that the car starts to "float" in uncontrolled manner - when there is no steering wheel input (I hold steering wheel in the same position) the car moves from left to right. that's about the MTD mini, the "fixed" MTB mini has absolutely no problems on such road
                Attached Files

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                • #9
                  On the road you have pictured, you may be experiencing what is commonly known as "Tramlining". See this:.

                  https://motoringjunction.com/tips-tr...-it-dangerous/

                  This article also discusses the effect of suspension and wheel and tire changes.

                  Are both of your cars using the same alignment settings? it would be interesting to see the figures, if you have them!





                  It only took me 3 years to reach 100 posts and become a senior member!

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                  • #10
                    Bumpsteer is when the wheel exhibits change of toe throughout its travel from full droop to full bump.
                    Caused by a mismatch between the arcs scribed by the track rod and suspension arms - i.e. steering rack at the wrong height or unsuitable steering arms.
                    The effect is that the car can 'steer itself' as the suspension moves up and down, independent of your input through the steering wheel
                    Last edited by fynnbar; 29-05-2020, 05:44 AM.

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                    • #11
                      https://www.youtube.com/watch?v=_ilnd5wQEpg

                      Bumpsteer 101
                      New subframe fitting has begun - slowly

                      Build Thread - standard length round nose B series with Rover K series frame, will it all fit ??

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                      • #12
                        This is also an interesting read.

                        http://www.spagweb.com/v8mini/doris/05/06_torquesteer/

                        Whist this says Torque Steer it is actually bumpsteer and shows the horrendous tracking changes that can occur through the arc of the suspension, in this case caused by V8 torque lifting the front on acceleration !

                        New subframe fitting has begun - slowly

                        Build Thread - standard length round nose B series with Rover K series frame, will it all fit ??

                        Comment


                        • #13
                          Originally posted by sniezix View Post
                          can we define what bumsteer is? my mini drives terribly when road looks like attached pic. what happens is that the car starts to "float" in uncontrolled manner - when there is no steering wheel input (I hold steering wheel in the same position) the car moves from left to right. that's about the MTD mini, the "fixed" MTB mini has absolutely no problems on such road
                          Wow! If I tried to drive on that, I would be bottomed out. It's no wonder your car is wandering from side to side.

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                          • #14
                            Okay well that picture was an obvious exaggeration, but it's about these kinds of road imperfections that cause problems, on absolutly flat road I have no steering issues at all. Both my minis were built by the same person (which I'm unable to reach) and he definitely called this problem "bumpsteer". I think it's camber not toe that's causing the problem though

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                            • #15
                              From what I can see the MTB1 frame uses Mini suspension (ie a Mini Top arm and an adjustable bottom arm and tie rod set up) whereas the MTD frame uses custom double wishbone suspension.

                              At this stage I'd suggest getting the MTD car to an alignment specialist, ideally one with experience in race-car set up.

                              If the suspension is having a huge camber change across the suspension arc then there is a serious issue. There should be some camber change ideally getting a little more negative camber on compression but not going to excessive positive camber on droop.

                              New subframe fitting has begun - slowly

                              Build Thread - standard length round nose B series with Rover K series frame, will it all fit ??

                              Comment

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