Alignment weirdness - does the rear affect the steering?

[joeluth]

Hi, well I've just finished replacing the worn out suspension parts on my boxster, 

I did the front coffin/control/tie rods/drop links/top mounts  and pretty much got away with it, took it for a little local drive and noticable improvement, wheel was straight, a touch of drift towards the kerb when I let go, but no steering wobble etc..  happy!

So I moved on to the back end,  did the drop links, coffin and control arms, new alignment bolts and put them back exactly where they were before.

No such luck this time, another short trip around the block and it's fixed the rear rattle, but the steering wheel is off centre,  it's turned right a fair bit when driving straight.

So I guess the rear alignment is now wrong enough to affect the steering, I didn't realise that could happen!  does anyone know what's going on?     

I am of course taking it to get aligned asap,   just curious as to what's happening at the moment. 

Cheers,

Joel

 

 

 

 

 

 

 

Edited August 24, 2021 by joeluth

[Danncus]

You have probably introduced a rear thrust angle

[Navman123]

Take a look at this, it's a start, there's a few more that are really good.

 

Edited August 25, 2021 by Navman123

[Lonewolfgjp]

I’m not sure 100% how it works but I had trouble with my rear camber bolts and the car was horrible to drive. I remember struggling just to keep it in a straight line, two new bolts and a 4 wheel alignment sorted it out 👍

[½cwt]

If you do the rear a full alignment is your only option.  I put my front back together and like you it was almost spot on, did the rear and I had to drive it the 1.5 miles to the alignment centre with almost ¼ of a turn of steering to get it to go straight  even with the front untouched.  The rear adjustments are very small to get the correct toe and no thrust angle.

[joeluth]

Cheers all, thanks for the responses and links, 

There's a race/performance car specialist near me so I've booked it in,  they did an alignment on my mx5 years ago, it's been straight as an arrow ever since. 

there's a 2 week wait for an appointment but after all the work I've done recently I'm just going to chill and wait to get it sorted properly.

[edc]

Quite a smart bodykit on your Boxster 🤣

[jonogt6]

4 hours ago, joeluth said:

Cheers all, thanks for the responses and links, 

There's a race/performance car specialist near me so I've booked it in,  they did an alignment on my mx5 years ago, it's been straight as an arrow ever since. 

there's a 2 week wait for an appointment but after all the work I've done recently I'm just going to chill and wait to get it sorted properly.

I thought the Ferrari body kit was only available for an MR2😉

[joeluth]

Just a quick update on this and a thanks again to those who mentioned the key word here "Thrust Angle" 

which led me to some interesting DIY videos on alignment, and enough to figure out what was so wrong with my car.

 I did indeed have a rear thrust angle offset, the main cause was the drivers side rear wheel being more "toe out"  so I adjusted it to match the passenger side best I could, and now we are steering straight again!

    of course this was a quick and dirty fix, I just eyeballed the markers on the alignment bolts,  but I feel a lot better about driving the 6 miles or so to the alignment now that it's not trying to drive in multiple directions at once! 

 

 

[Boxsum]

Excellent!

As others have previously advised on the forum if you have done your own suspension and then had alignment done it’s always a good idea to re-torque your bolts 👍

[RalphyBMW]

When I did my rear, I booked it in at Spires Tuning, but had a geo done at a local Halfords just to tide me over.

The result was way off what Spires’ delivered, but at least meant all 4 wheels were pointing in basically the right direction and that the car could be used in the meantime.