Alignment with H&R Springs and 275's

Discussion in 'Generation 4 - Maintenance & Troubleshooting' started by jman1200, Jun 12, 2019.

  1. jman1200

    jman1200 SHO Member

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    I've owned my SHO for more than a year now. Last year I had it aligned as I noticed that the inside of the front tires was wearing out and the car acted weird whenever I hit a change in terrain.
    First I thought the wear was due to the angle caused by lowering the car's height but then, I started noticing that the car would pull either left or right whenever I ran over a patch or incline (on just one side of the road) or just drive on an irregular road.

    Got it aligned last year and it felt better but now, I started feeling the right/left pull again and the steering wheel is still centered so I do not suspect the alignment came off. The car drives straight when the road is flat.

    Thoughts on the right/left pull? I believe having a 275's and the suspension working on an angle doesn't help but wondering if anyone has experienced this and if there is a definitive solution I can implement before wearing my tires again.

    What alignment specs is the shop supposed to follow if the car has been lowered?
     
  2. krewat

    krewat SHO Member

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    With such wide tires, and what I suspect are aftermarket rims with a different offset, and possibly different diameter altogether, placing the tire outside of the "center" of where it is stock, this might have something to do with the SAI (Steering Axis Inclination - also known as King-Pin Inclination or KPI).

    Because of the changes, the various angles are out of the right "zone".

    When you're on level and even roads, the forces counteract each other. Once you get one tire on a different surface, it'll pull to one side.

    At least, that's my theory. When I put larger diameter tires on my F250 using the stock rims, the steering was worse in terms of exactly what you're describing. The reason being that the SAI fell outside of the zone it should be in, in terms of where the SAI hits the pavement, and where the tire was in relation to that. If I had gotten rims with more of an offset, that would have put the tire back into the right zone. In my case, the SAI had moved outwards. In your case, if the tires are the same diameter but you have more offset to tuck the tires in deeper into the wheel wells, your SAI has also moved towards the outside edge of where the tire meets the pavement.

    TBH, all three of my SHOs all pulled a lot on uneven surfaces. All three are/were PP's.



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  3. Lostneye

    Lostneye SHO Member

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    I am running 275s with H&Rs and the roads are crap here. It don't feel it's excessive but the car does pull a little more than it did before the H&Rs on uneven surfaces. There is a difference with stock springs and the 275s then stock wheels/tires as well. Haven't been lowered long enough to comment on tire wear. I think krewat is on the right track. With wider tires even on stock suspension you can see the car pull more, add the changes in suspension and things can add up. How long have you have the H&Rs and when was the last alignment?
     
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  4. jman1200

    jman1200 SHO Member

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    I bought the vehicle with the springs in it. Alignment was done about 6 months ago.

    What @krewat wrote is what I believe it's happening, just wondering if it can be minimized and again, what specs should be used to align it.
     
  5. Lostneye

    Lostneye SHO Member

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    I don't have what the actual specs are. My car was aligned to factory specs.
     

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