19 replies to this topic

[Hedgey]

Hi,

 

I'm currently setting up the suspension on a mini I have been rebuilding for the last 6 or so years and have some concern over the amount of toe in I have at the rear.

 

• Rear subframe is non genuine (I know these can cause some issues but it was changed before the car became mine)
• Radius arms are both refurbished units not original to the car (Refurbished by a mini specialist who said they are checked on a jig or straightness)
• I have measured the subframe alignment as accurately as I can on my drive - I got a 4mm difference from one diagonal to the other  

So I have being following the basic setup method outlined by Keith Calver here https://www.calverst...-set-up-method/

Front tracking has been set straight using a Gunson Trackrite guage and the steering centred.

 

When I run a string line around the car through the centre line of the wheels I'm getting a gap of 10mm NS & 6mm OS between the tyre sidewall and the string. Obviously this is much more toe in than the standard 1/8th

 

I know you can buy shims to correct the toe in http://www.minispare...|Back to search

The ones from Minispares say that the 0.028" shim alters the toe by 0.028" so 1:1 ratio on 10" wheels. By that I would need a 10mm shim on one side and a 6mm on the other.

 

Is this too much to shim? Would adjustable brackets be a better idea?

 

I appreciate any help I get on this. I don't really want to buy a new genuine subframe at £464

 

 

[Spider]

The Factory say that ' Approximately ' 1.0 mm of Shim, will reduce Toe In by 1.58 mm, however, they also give an upper limit of 3.0 mm of shims.

 

 

The differences you are seeing, from my experience, is not unusual and more likely to be the Arms being out rather than the Subframe not being right. I'm not sure how far the various Adjustable Brackets can take you, but it is entirely possible to bend the Arms to reduce this error, then Shim to fine tune them.

[Hedgey]

The Factory say that ' Approximately ' 1.0 mm of Shim, will reduce Toe In by 1.58 mm, however, they also give an upper limit of 3.0 mm of shims.



The differences you are seeing, from my experience, is not unusual and more likely to be the Arms being out rather than the Subframe not being right. I'm not sure how far the various Adjustable Brackets can take you, but it is entirely possible to bend the Arms to reduce this error, then Shim to fine tune them.

Thanks for the reply! That information is very useful. I will remeasure the toe in a couple more times before making some shims.

Is there any dimensions or a way to check the radius arms to see if they are bent?

[Spider]

I have a Jig I made for checking the arms but probably the easiest / simplest way for the guy at home to go about the job is to set the subframe up on the bench first. It may need some tweaking once in the car as it may not fit up dead square 'in car', but, at least this should get you well in the ball park.

 

Without the arms on the Subframe, fit up the outer brackets, If you are good with your eye, you can check all 4 holes for the Trailing Arm Pins are in a line in all planes. If you don't trust your eye, get a 4' length of 1/2" steel rod, check that it's straight and it should pass through all 4 holes easily and without bending. This will confirm that the Subframe is right (or not).

 

Next fit up the Arms (without Cones is easier), fit a couple of steel tubes of pipes over the shock studs so that these will hold the Arm in a fairly neutral height position and as near as you can get each side the same as the other, The Pipes here can rest on the subframe to hold them in this position.

 

With the hubs fitted, bolt up a couple of wheels (best if they don't have tyres fitted) and spin them to check for wobble. Steel wheels usually will have some. Find to the two points of wobble, then mark the mid point. Measure from the Subframe Mounts back the the centre of the Subframe on both the front and rear. Put down some Masking Tape to draw your centres marks on to.

 

Then measure from these centre marks back to the reference mark you made on the wheels, checking on the leading and trailing sides, by turning the about wheel 180 degrees. You can make your adjustments in and then check in the same way. It's a good idea as well as checking each side separately, to also check side to side. This will take a few hours, so be prepared for that. It will also show which arm is bent and by how much.

 

I did make a jig to hold the arms to bend them in the press, but more recently, I tried supporting the arm between Press V Blocks and then Pressing between these on a Hardwood block with good results, only I find I have way less feel because of the Hardwood Block, but it works. Take small 'bites' here, but, they do need a reasonable nudge to actually set them, so don't be alarmed by that.

[Hedgey]

Wow great write up! I think I’m going to start by moving the car and then remeasuring. According to the workshop manual information above one side will need 2.75mm of shims, the other 5.3mm

[GraemeC]

That seems a lot, even for non-genuine tolerances.

 

I think you are trying to get too much info from your string line. Doing it the way Keith describes will NOT allow you to measure the tracking on the rear - it will only tell you that both sides are the same (or not) and whether the back is aligned with the front (or not).  

 

It is possible to measure the tracking using a string line, but the string must be perfectly parallel down both sides of the car and parallel to the centre line of the car.  Given the Mini is wider at the front than the back, that will mean holding it off the car at the rear corners and then taking measurements from the string to both the front and rear of the wheel rims (not at the tyres) and subtracting the values from each other.

 

 

On 10" wheels, one way to measure it at home is:

Using a spirit level, mark the tyre at its fattest point out on the horizontal centre line, both to the front side and the rear side (from memory the marks are about 14.5" apart).

Drop plumb lines from these marks to the floor and mark the floor.

Do this on both side of the car.

Measure between the two 'front' marks and the two 'rear' marks and subtract the front measurement from the rear measurement.

This gives you the total toe (+ve is toe in, -ve is toe out).

 

With some maths you can extrapolate the recommended values for a 10", 12" & 13" wheeled Minis to give you the value at this 14.5" measurement (although to be honest if you aimed for the 13" recommendation you'd be well within tolerance).

 

 

Obviously to know which side to adjust, you need to know if they are both same (or their relationship to each other) using Keith's method.

Edited by GraemeC, 16 April 2020 - 09:29 AM.

[Hedgey]

That seems a lot, even for non-genuine tolerances.

I think you are trying to get too much info from your string line. Doing it the way Keith describes will NOT allow you to measure the tracking on the rear - it will only tell you that both sides are the same (or not) and whether the back is aligned with the front (or not).

It is possible to measure the tracking using a string line, but the string must be perfectly parallel down both sides of the car and parallel to the centre line of the car. Given the Mini is wider at the front than the back, that will mean holding it off the car at the rear corners and then taking measurements from the string to both the front and rear of the wheel rims (not at the tyres) and subtracting the values from each other.


On 10" wheels, one way to measure it at home is:
Using a spirit level, mark the tyre at its fattest point out on the horizontal centre line, both to the front side and the rear side (from memory the marks are about 14.5" apart).
Drop plumb lines from these marks to the floor and mark the floor.
Do this on both side of the car.
Measure between the two 'front' marks and the two 'rear' marks and subtract the front measurement from the rear measurement.
This gives you the total toe (+ve is toe in, -ve is toe out).

With some maths you can extrapolate the recommended values for a 10", 12" & 13" wheeled Minis to give you the value at this 14.5" measurement (although to be honest if you aimed for the 13" recommendation you'd be well within tolerance).


Obviously to know which side to adjust, you need to know if they are both same (or their relationship to each other) using Keith's method.

Thanks for your reply.

I appreciate the way I have been using to check alignment isn’t the most accurate for the task in hand.

The mini was actually booked in at a local classic specialist who was going to set up the alignment & suspension whilst also checking it for road worthiness (Mot exempt) before it goes on the road. Obviously with the current Covid-19 situation that won’t be happening anytime soon so I just wanted to get the alignment somewhere near and check the values against standard.

Keith’s article says if the measurements form the string line to the tyre differ by more that 1.6mm to get it sorted before going further. That’s what I’m trying to achieve and thought that shims were the way to do it.

I will look at doing more accurate measurements

[Hedgey]

I managed to do some more measuring today using the string line method to see if I had made any errors.

 

• This time I decided to measure to the rim edge instead of the the tire side wall (on the 2nd & 3rd test I measured the distance to the side wall and the rim edge closest to the rear as well)
• I took the measurements 3 times, each time the mini was moved to a different spot on the driveway and the string line set up from scratch
• The driveway is smooth & flat concrete flags (only minor deviations)
• The mini was rolled forwards approx 2m before each test and the handbrake was applied (I made sure it didn't roll backwards at any point)

So the results:

 

Test 1

 

String line to Rim edge (Closest to Front)  LH: 19.5mm RH: 18.5mm

 

Test 2

 

String line to Rim edge (Closest to Front) LH: 19mm RH: 19mm

String line to Rim edge (Closest to Rear) LH: 14mm RH: 14.5mm

String line to Side wall  LH: 7mm RH: 6mm

 

Test 3

 

String line to Rim edge (Closest to Front) LH: 20mm RH: 19mm

String line to Rim edge (Closest to Rear) LH: 15mm RH: 14mm

String line to Side wall  LH: 9mm RH: 7mm

 

 

So the average between the string line and rim edge (Closest to front) is LH: 19.5mm & RH: 18.8mm 

A difference of 0.8mm

 

I know this inst perfectly accurate but I feel its close enough for me to be happy the wheels are in-line.

 

I also did a test for toe that Cooperman suggests using 2 straight pieces of wood and measuring at 2 different points along them. Through this I calculated the rear wheels toe in a total of 7.5mm

[GraemeC]

That sounds a lot better!

Well apart from your ‘calculated’ 7.5mm toe in - if it’s really that much you’d be scrubbing tyres off in just hundreds of miles!

[Hedgey]

That sounds a lot better!
Well apart from your ‘calculated’ 7.5mm toe in - if it’s really that much you’d be scrubbing tyres off in just hundreds of miles!

I did try to do the test as accurately as possible though I think there was a lot of potential for error.

I do have one of the drive Gunson over gauges I could use to check the toe if a value in degrees is known? I haven’t found one yet

[GraemeC]

About 10-12 minutes toe in

Edited by GraemeC, 16 April 2020 - 08:24 PM.

[Spider]

If I'm reading your numbers right (not sure I am), then you have Toe Out and no shimming will correct that, one or both arms are bent, usually the near side one.

[hoggy]

Hey I’ve been doing the exact same job last two days.

I centred the front wheel to straight ahead with one of them trackace tools.

Then ran a string line along the front to rear. Ensuring the stein touched both edges of wheel on the front, then touching the rear wheel. The gap on the front of the rear wheel was around 10mm each side.

I’ve added 7 shims to the first side and it’s down to around 2mm toe in. Seems excessive to have to do that!

Am I doing this correctly?

[GraemeC]

No. - As I said above, you CAN NOT use this method to measure the toe in.

You now likely have massive toe out which will be very dangerous to drive

[Hedgey]

As above, I also made the mistake of believing the string line indicated the toe value. It only indicates the alignment of the rear wheels to the front.

To be honest I believe a few people have made the same mistake. I have read a few threads where posters have set the string line to wheel measurement at 2mm believing it was the toe.

Edited by Hedgey, 17 April 2020 - 07:59 AM.