Steering Vagueness

Discussion in 'Capri Chit Chat' started by BigJ, 3 November 2018.

  1. BigJ

    BigJ Registered Capri Power Member

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    Anyone else using 8” rims ET0 offset experiencing steering wander?

    I’ve run out of things to check and replace and through the process of elimination I’m wondering if these wide rims with 215 tyres fitted are causing this?

    Everything on the steering and suspension is new and correctly adjusted and there is no play between the steering wheel and the road wheels but when driving it feels like the whole front end is sloppy and steering itself as if every component was old and worn.

    Might try fitting some standard rims and tyres off the 2.0S to see how that goes but I thought I’d ask the question of others with similar wheels fitted.
     
  2. robt100

    robt100 Registered Capri Power Member

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    The increase in tyre width and offset will cause more scrub radius and therefore make it more "wandery", well, thats what I gather from what I've learnt on this forum over the years! Its worth trying smaller width back to back to see if there is a difference though, may help to narrow it down.
    If not, when you had the alignment on the tyres done, did they check your caster angle? That can also have a bearing on the stay-straight-ability
     
  3. Nick

    Nick A human. Being. Staff Member Forum Tech

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    Joe, I have 15x8 ET0 on mine. I do feel it from time to time on my car. Mainly on motorway slow lanes when the tracks are worn in by the lorries. Scared me until copey pointed that out. For pottering about on B roads it seems fine. All my front end is all new/reconditioned kit.
    As Rob says I think it just comes with the wider contact patch.

    I would be interested when you swap to some narrow wheels if it sorts it, as on the motorway my bum was twitching like a rabbits nose at times!!!
     
  4. CapriJake

    CapriJake Registered Capri Power Member

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    I have similar issues with my 205 wheels. But like Nick said it’s in the lorry grooves only basically. No issues on normal roads, or good excuse to use the fast lane only. ;)

    I assume since you said all new the steering rack is new/reconed.
     
  5. 302Capri

    302Capri Registered Capri Power Member

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    Different tread patterns can behave very differently. If you get the opportunity to try some different tyres even in the same size you may notice improvement.
    The first thing I would do is have your wheel alignment guy dial in a little more toe-in. This helps to reduce wandering on uneven surfaces.
     
  6. Stroker

    Stroker Registered Capri Power Member

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    I found my old Capri to be quite sensitive to the front wheel off-set. I remember changing the rims on my car from a 13 x 7" to 13 x 8" thinking that widening the track and stretching the 205 tyres out a bit would be a good call for a bit of club track work.
    With the same tyres and the only change to the car being the wheel off-set out to increase the wheel width, turned it into a under-steering pig.:mad: Subsequently I went back to the original 13 x 7" quick smart.:D
     
  7. BigJ

    BigJ Registered Capri Power Member

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    Thanks chaps. The sensation is similar to driving in the HGV grooves on the motorway but it happens on all types of road more so when I am driving at slower speeds and where the camber of the road may vary more. Every item on the car is brand new including the rack which I replaced out of sheer frustration after eliminating everything else. The slightest movement of the steering wheel causes the road wheels to move so no play at all in that particular chain.

    I just get the feeling it’s to do with the width of the tyres so as soon as I can swap them over and try out a narrower set then I will do and report back with the results.

    BTW I’m running Dunlop SP Sport 9000 215/50 ZR15 tyres.
     
  8. Clockwork Orange

    Clockwork Orange Electrical ??? what like .. bzztt Feck !!! Staff Member Moderator

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    never had any probs with either 205/50 or 195/50 x15 tyres..
    I was running 15x7 wheels at ET11 .. my Fondmetals ..
    I would suggest that your choice of wheels is probs OK.. but its the tyre size that's causing the problems..
    also, after a bit of experimenting with my 3ltrs, Lasers, and V8 .. try pulling the front of the legs forward a bit ..
    when you drop the ride height it is a natural product that pushes the wheels backwards a tad because of the way the anti roll bar works and influences the TCAs and the struts ..
    shorten the reaction length a bit, it increases the castor, your steering should feel sharper ..
    certainly worked on my 3ltr Mk1.. and have transposed it into all my Lasers since ...

    ARB (front) Mods.JPG
     
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  9. Crash & Burn

    Crash & Burn Registered Capri Power Member

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    Nice drawing and explanation, Alan, and the reasoning looks very similar to what my alignment guy suggested once. I've also found extra-wide tyres to be a challenge to the system, but there is true merit to your adjustments. Joe well deserves perfection, and should see it soon now.
     
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  10. BigJ

    BigJ Registered Capri Power Member

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    You’re too kind Gary, I just want the car to drive as intended. You know how it is when you need to rely on it to go where you point it when you need it to...

    I did look at Alan’s thread some years ago now but struggled to work out how to keep the diameter of the ARB the same all round when making the adjustment. I did think that using castor correction strut mounts instead might help but then when using them, there seemed to be a trade off between ride height and comfort to achieve that and then the results might be subjective at best. I wanted to eliminate the basics first which I think I have done whilst only covering a hundred or so miles a year recently .

    I’ve just finished building my workshop, inspired by yours but without the good weather and so hopefully over the winter months I will make some headway with this and be able to report back. First job is to swap over the wheels to standard to see what happens. If things improve then I know I will be looking in the right direction.
     
  11. Crash & Burn

    Crash & Burn Registered Capri Power Member

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    Credit where it's due, Joe -- You've put such meticulous planning and care in that you naturally deserve it all to be right. I do think that within all the suggestions above you should find the needed correction, and none of us is in a better position than you to find and select that right direction. At the moment, I'm not seeing how the ARB diameter issue arises, but have no reason to disbelieve you either. If you're that much more attentive to it, that only makes me more confident you'll get it right. And I'd like to see what you built - If inspired by mine, it must be at least mediocre! :) I'll get some pics of my new garage in next week when I return there....
     
  12. fordperv

    fordperv Registered Capri Power Member

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    I have been contemplating doing this to mine as I have a spare arb and wanted a bit more castor, im glad what I was thinking works
     
  13. therealpinto

    therealpinto Registered Capri Power Member

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    I agree with what has been said above, basically. The increased scrub radius is what is giving the problems.

    More caster and more toe in may help, caster is the most important thing to correct. In order for the wheel to sit central you might end up wanting to change both the ARB and the strut top (shortening the ARB too much will pull the wheel forwards into the wing).

    One option for the caster is to modify the brackets that hold the ARB to the body. Sometimes, depending on what kind of equipment you have, it is easier to change them to bring the ARB forwards, than to machine the ARB. That also makes the change more reversible. Basically you can cut and weld the brackets (the ones that fit into the corners of the engine bay) to bring the mounting points further forward.

    Regards

    Gustaf
     
  14. BigJ

    BigJ Registered Capri Power Member

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    One concern I have about moving the strut forward on the ARB is that in doing so it might place the TCA inner bush under lateral tension and cause it to wear prematurely as it’s fixed in position by the chassis recess it fits into and looks like it’s only intended to move vertically with the movement of the roadwheel.

    I can see how doing so would compensate for a lowered car where the strut was pushed rearwards by the change of height as Alan described but mine is on standard 2.8i springs and so has retained the standard ride height as a result. Bearing in mind Ford manufacturing tolerances though, I might get the castor angle checked and compare it to the factory settings if I can find them. Can the castor angle be checked as a DIY exercise at home in the garage or does it require specialist equipment?

    Can the same be achieved by using adjustable top mounts instead to improve the scrub radius?
     
    Last edited: 12 November 2018 at 10:48 PM
  15. therealpinto

    therealpinto Registered Capri Power Member

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    The bush can take the angle, that's not a big problem.

    The only way to change the scrub radius itself is to change the effective ET or the angle between the wheel and strut (and changing overall wheel diameter but that has other effects). But moving the strut top rearwards will increase caster and that will help.

    Setting/measuring caster properly means special equipment but an inclinometer (angle finder) against the strut casing (cleaned) will work as a start. There are nice inclinometer (spirit level...) apps for smart phones, a handy tip :)

    Gustaf
     
  16. BigJ

    BigJ Registered Capri Power Member

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    Cheers Gustaf

    I’m more inclined (pardon the pun) to go the way of an adjustable strut top rather than modifying the ARB. Would it just be a case of trial and error to find the right amount of angle to adjust or is there some way to calculate it accurately?

    Failing that then maybe my only option would be to get another set of narrower wheels say a 7.5” to reduce the scrub radius that way. I know I can get the same style Revos in that size and I think 7.5” rims were an option offered by Ford weren’t they? With a narrower rim could I also change the offset to reduce the scrub radius even further back towards standard? I’m on ET0 at the moment on the 8” rims.
     

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