How to set toe when both axles are adjustable
Discussion
Hi all
Recently changed all the suspension components on my 986 boxster. New coil overs, coffin arms, drop links, tuning forks and track rods.
I will be taking the car for a proper alignment, but in order to get me there safely, traditionally on other cars I have done a ‘string box’ alignment.
By that I mean set up a string line and used the fixed rear wheels as a datum to set the front toe in/ out.
The 986 is the first car I have had where you can adjust the rear wheels for toe aswell. So…. How am I to know/ set the rear tow angle up in order to use it as a datum for the front wheels?
As far as I see it the string method can’t work because I don’t know and won’t ever know if the rear is truly at 0 degrees until I get it on a 4 wheels alignment machine?
Any advice greatly welcomed
Recently changed all the suspension components on my 986 boxster. New coil overs, coffin arms, drop links, tuning forks and track rods.
I will be taking the car for a proper alignment, but in order to get me there safely, traditionally on other cars I have done a ‘string box’ alignment.
By that I mean set up a string line and used the fixed rear wheels as a datum to set the front toe in/ out.
The 986 is the first car I have had where you can adjust the rear wheels for toe aswell. So…. How am I to know/ set the rear tow angle up in order to use it as a datum for the front wheels?
As far as I see it the string method can’t work because I don’t know and won’t ever know if the rear is truly at 0 degrees until I get it on a 4 wheels alignment machine?
Any advice greatly welcomed
The way I did this previously on 2 x e36s that underwent major suspension surgery when converting to track day cars was as follows.
Starting at one side, turn the steering to get that one front wheel pointing straight ahead, then (sighting down the rear wheel with a straight edge adjust that rear to straight ahead.
Same on the other side.
You will then be close enough to "straight ahead" at the rear to "string box" the front.
When you have "string boxed" the front a confidence check on the rear is sometimes the order of the day.
After that, I did another check of it all to confirm it was OK, and if any adjustments are required do it again, but they weren't required each time I did mine.
Yes, before anyone says, obviously I know this is never going to be 100% accurate, but it gets the car close enough to drive safely for a proper alignment.
In reality each time I did this it wasn't far off at the alignment place I used.
ETA.
Wasn't far off "straight ahead" that is.
Starting at one side, turn the steering to get that one front wheel pointing straight ahead, then (sighting down the rear wheel with a straight edge adjust that rear to straight ahead.
Same on the other side.
You will then be close enough to "straight ahead" at the rear to "string box" the front.
When you have "string boxed" the front a confidence check on the rear is sometimes the order of the day.
After that, I did another check of it all to confirm it was OK, and if any adjustments are required do it again, but they weren't required each time I did mine.
Yes, before anyone says, obviously I know this is never going to be 100% accurate, but it gets the car close enough to drive safely for a proper alignment.
In reality each time I did this it wasn't far off at the alignment place I used.
ETA.
Wasn't far off "straight ahead" that is.
Edited by E-bmw on Sunday 8th February 11:38
cliffords said:
I paid to have it done about £100 at my local garage with four wheel laser alignment.
I thought it was probably a bit of a con so I watched him do it . It was not at all. My rears were a long way out and the car drives so much nicer now .
Did you read my OP? That’s my plan. I thought it was probably a bit of a con so I watched him do it . It was not at all. My rears were a long way out and the car drives so much nicer now .
I was just asking how to get it close so I can safely take it there…. It’s SORN currently and probably will be till spring so I’ve time to play and so thought might as well try and get it close
eltax91 said:
cliffords said:
I paid to have it done about £100 at my local garage with four wheel laser alignment.
I thought it was probably a bit of a con so I watched him do it . It was not at all. My rears were a long way out and the car drives so much nicer now .
Did you read my OP? That s my plan. I thought it was probably a bit of a con so I watched him do it . It was not at all. My rears were a long way out and the car drives so much nicer now .
I was just asking how to get it close so I can safely take it there . It s SORN currently and probably will be till spring so I ve time to play and so thought might as well try and get it close
I made myself one of these:
https://wiki.seloc.org/a/Geo_Alignment_Rig_(Home_M...
I've found over the years that I can be accurate enough with it, that resetting the geo every year or so using that rig will result in a better average setup than taking it to a hunter rig every few years. At least on the Elise, which is somewhat renowned for throwing its geometry out every time you hit a pot-hole.
https://wiki.seloc.org/a/Geo_Alignment_Rig_(Home_M...
I've found over the years that I can be accurate enough with it, that resetting the geo every year or so using that rig will result in a better average setup than taking it to a hunter rig every few years. At least on the Elise, which is somewhat renowned for throwing its geometry out every time you hit a pot-hole.
To do a string alignment like the motorsport teams do, you out the lines down either side of the car and then set the lines to be parallel to each other by measuring to the centre of each wheel, and the width of the box at either end, noting that one axle might have a different track width to the other.
What you are aiming for is a square box around the car that is parallel to the centreline of the car.
You can then measure the distance from the line to the wheel at the front and back of each wheel to get the tracking dimensions.
What you are aiming for is a square box around the car that is parallel to the centreline of the car.
You can then measure the distance from the line to the wheel at the front and back of each wheel to get the tracking dimensions.
MK2 rigged up so i could raise/ lower the car if needed.
Car has entire new front suspension, arms, TRE's, tuningn forks etc
Rear, I changed all that 1300 miles ago to replace a broken spring. So this time I only replaced the lower control arms (becsause I damaged the boot upon removal). The tuning forks and control arm are 18 months and 1300 miles old.
I got the fronts nice and true. and the drivers rear is fine. But even with the adjustment at it's max, the passenger rear is still 10mm out of true when measured at the front/ back of the rim edge. I've raised it and turned it 1/8 turn at a time and it's consisten roight around the circumference....
Any idea greatly appreciated.
Edited by eltax91 on Monday 9th February 13:38
E-bmw said:
Sounds like either something is bent or you haven't allowed for different track width front/rear.
ETA.
I don't know if they are different, just something I had to deal with doing mine as above.
Guess what i did?! Didn't allow for the difference in track width. Will be having another go tomorrow. ETA.
I don't know if they are different, just something I had to deal with doing mine as above.
Edited by E-bmw on Monday 9th February 14:39
Before I had to get back to work and after reading the guide above on the Elise, I have:
Marked the centre of the car with a plumb line. Front and rear.
Measured outwards from there 910mm on all 4 corners a made a mark for the string.
Fitted the rear bar to two axle stands. There’s still too much movement in the front bar so tomorrow I’ll fix that to two more stands, square it up (properly this time) and have another go.
That should get me close enough to get it in for laser when I decide to take it off sorn
Marked the centre of the car with a plumb line. Front and rear.
Measured outwards from there 910mm on all 4 corners a made a mark for the string.
Fitted the rear bar to two axle stands. There’s still too much movement in the front bar so tomorrow I’ll fix that to two more stands, square it up (properly this time) and have another go.
That should get me close enough to get it in for laser when I decide to take it off sorn
I drilled holes through the metal bars to feed the line through; that forced them to stay the same width apart and the same distance from my centre mark on both bars and allowed me to use a weight (just a nut tied onto the end of the line) on one end for tension.
Edited by kambites on Monday 9th February 19:09
I'd just get them straight by eye and get the alignment guy to do it properly. That's what I did after changing the dampers and springs and polybushing my MX5.
I was curious to see how my straight by eye alignment checked out on the machine though.. It didn't show a reading at first! A box came up saying: "A large adjustment is required"
I was curious to see how my straight by eye alignment checked out on the machine though.. It didn't show a reading at first! A box came up saying: "A large adjustment is required"
Bainbridge said:
I'd just get them straight by eye and get the alignment guy to do it properly. That's what I did after changing the dampers and springs and polybushing my MX5.
I was curious to see how my straight by eye alignment checked out on the machine though.. It didn't show a reading at first! A box came up saying: "A large adjustment is required"
Where’s the fun and learning in that? I was curious to see how my straight by eye alignment checked out on the machine though.. It didn't show a reading at first! A box came up saying: "A large adjustment is required"
eltax91 said:
E-bmw said:
Sounds like either something is bent or you haven't allowed for different track width front/rear.
ETA.
I don't know if they are different, just something I had to deal with doing mine as above.
Guess what i did?! Didn't allow for the difference in track width. Will be having another go tomorrow. ETA.
I don't know if they are different, just something I had to deal with doing mine as above.
Edited by E-bmw on Monday 9th February 14:39
Ask me why I guessed that?
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