Sam's build thread

[sambb]

I finally got the kick in the arse I needed to properly learn how to string line yesterday. I'd re shimed my left rear a couple of days ago to get 2 degrees neg camber and 2mm toe out. I did all the calcs based on the shims that had already been in there and then going up in the toe/camber settings from there to hopefully arrive at the angles that I wanted. The alignment numbers I had for the removed shims were from a Pedders printout from a year and a half ago.
So I went down to a local aligner that a local Porsche specialist said in the past that they send their customer road cars to and got the following rear toe:

left -1.2 right -0.3 Both toe'd out with more on the left but not enough.

They gave me a freeby because I'd only wanted the numbers which was very very generous. So I figured in the name of science I'd go somewhere else with my 50 bucks that I'd been planning on spending.

left -6.2mm right +1.7mm You'd read that as 6.2mm toe out on the left but apparently not!

Yep was thinking WTF at this stage especially when told by the operator that the lasers read from the back of the laser/paddle on their rig so -6.2mm is actually toe in.....double WTF. They were pretty cheap and being the OCD I am I went to another place where I also got straight on.

left -0.7mm right -1.75mm Both toe'd out but apparently more than double on the right now after a 50m drive.

So it seems that same car same day same tyre pressures etc etc I can have anywhere between 6.2mm toe in to 1.2mm toe out on my left rear. The right side can have a nearly 3mm variance too. The only thing they all agreed on is that I now have an even 2 degrees neg camber on both sides at the back. Precision machines eh? what a cluster f$%#k!

So I went home rigged up car stands, some braid fishing line with sinkers, got out the tape measures etc. I formed the rectangle around the car. Referenced each line to the end of the spindle at the front and at the back used the wheels centre cap ridge to get the car centred inside the string lines. I did 4 separate measure ups. Once because I tripped over the lines after an hour of setting it up and measuring and another after one of the tape measures popped off and dragged a string out of position. The other times because my OCD kicked in again. So after setting up from scratch 4 times I repeatedly have exactly 2mm toe out on the left rear (across a 15 inch rim) and 0.5mm toe out on the right rear. The front had 3mm total toe on the strings and I verified that afterwards with toe plates. I'm pretty dam confident that those are actual measurements. If you assume that I added the corrections to the old/removed shim numbers correctly, then the early Pedders printout from way back was probably still correct because that's the reference I went off.
The first aligner I went to on the day was the only one in the ballpark. I told them it was on 15 inch rims so their numbers are a bit under. If they'd put it in as 14 inch rims that might explain there numbers? But at least they were able to ascertain that the wheels were either pointed in or out unlike one place and didnt get readings suggesting that the other wheel was the one that was toe'd out the most.
So yeah after finding out what I've long suspected I will never be going to an aligner ever again.

[Sydneykid]

For string alignment I don't use string I use hat elastic, 2.0 or 2.5 mm 'ish cheap as from Lincraft,. Since it's elastic I can do things like hook it up over the exterior rear vision mirrors to get it out of the way while I do adjustments. If I bump (that never happens) the elastic it stretches and doesn't pull the axle stands. It also tends not to vibrate so much in the wind when doing rush alignments at the track.

I do string alignments on every race car at least once a year unless there is some reason to suspect the toe plates. Since they only measure the total toe, not individual wheel toe.

Add another 1 mm to the left and you should be good to go.

Cheers
Gary

[Sydneykid]

My forged rods are 20mm for the S3 pistons. Hondas are 21mm pin yeah. So for a 21mm pin end rod that'll fit my engine and the Honda pistons I was thinking golf mk5/6 rods.
Could my 20mm forged rods be drilled out to 21mm. That ever get done?

All the time, 0.5mm no big deal.
I'd still check out machining the S3 pistons.


Cheers
Gary

[metalhead]

Lol, yep! All of that is why even my old f250 gets aligned at home nowadays. The straw that broke me was taking it to have the front toe set as I had been busy with work (so wanted to save some time) and had replaced some tie rods. It came back wandering all over the place and with a steering box adjusted up so tight that it wouldn't return to centre by itself (I hadn't asked for or agreed to a steering box adjustment, they just did it to "help me out"). They told me there was something wrong with the steering box blah blah... I actually pulled over and loosened the adjustment on the steering box before I drove it more than a block, drove it home and parked it until the weekend when I readjusted the steering box correctly and corrected the toe - it had something like 20mm toe out from memory!! Never again. I like Gary's hat elastic suggestion, might have to update my string line setup!

[sambb]

Yep I strung mine up and then looked inside and realised that the handbrake wasnt on and that my pencil torch was in the glove box. If only I could open the door without upsetting the line. Too unwieldy at the track but I was planning on using 2 x aluminium square tubes say 2m wide and putting notches in each end exactly 1800mm apart. Rather than having to measure two separate strings widths from each other I just break out two rods, place them front and back across the stands and then run my pre made/weighted strings (marked length wise too) between them through the notches. I reckon you'd be able to zero in much quicker on squaring the car with the strings doing something like that. Thinking about it front toe is something I'd just do with toe plates anyway. I'd only ever string it to get everything referenced up for checking rear toe. No matter what the angles, adjusting rear toe on the twist beam is DEFINITELY not a job you can do whilst reaching under strings no matter what they are made of!
While I was at it I was able to accurately measure my front and rear tracks. With a front 8mm spacer and SimonK's rear stub axle spacer fitted It is 14mm wider on the front than the rear measured at the stub axle tips, so 7mm per side narrower on the rear. Next thing will be too see if 215/50/15's will fit under the rear guard lip with the extra tuck that the 2 degrees neg rear camber affords. Despite being medium compound I'd really like to run 215's all round at Bathurst this year. With the rear toe out, psychologically I think I'd feel a bit better about having more rear rubber on the back this year. A full 20mm wider per tyre than the 195/55's softs you'd think that'd give me more grip despite the harder compound.

edit: I'm lucky, at work we have a big one of those true flat surface granite slabs so before doing toe checks I can make sure the toe plates are bang on before I use them.

[metalhead]

Yeh, I just have two lengths of square steel bar, maybe 15mm square? With the string points marked on them and string permanently tied to them, I just roll them up string and all and stand them in the corner of the garage. Set them up with jackstands and some bits of timber to shim the heights. Not as quick and easy as the toe plates obviously, but it's pretty quick to setup and pack up again.

[sambb]

ah yeah even better. I'll do the right side soon enough to get those toe angles right and I also need to switch it over to a DBA T2 disc as well. Still so ****ty at those muppets. Like that day last year when I just couldn't get the thing turned despite so much effort and scratching my head chasing other problems when really I was running with toe in all along.
There's a VW day down at Wakefield in May apparently, sort of replacing the usual DubNats at SMSP south circuit so if I still have my silly OE turbo on at that stage, it'll be interesting to see how the car goes again now that it'll hopefully be properly sorted chassis wise. It'll still have second hand 3 year old + tyres but it'd have to go better than last time.

I just need to find one more 215/50/15 second hand somewhere and I'll have a full set, which you'd think would go better than the 205's mediums I had on last time. If they fit I'd love to take my beat up set of soft 195's on another pair of rims for the rear and see if a one lap wonder/time attack style can generate a quicker lap time with front 215 mediums and rear softs than a full set of 215 mediums.

[Sydneykid]

I'll see if I can find you a not terrible 215/50/15, I'll let you know. Have you got any 16" wheels yet, there's a couple of 225/45/16's that would do you for few meetings.

Cheers
Gary

[sambb]

That'd be unreal Gary. No the only 16's I have are the OE 16 x 6.5's. A 225/45/16 has a slightly narrower section width than a 215/50/15 doesn't it, but despite that I always figured the OEM 16's would still be too narrow for 225's They are definitely heavy that's for sure, I think 9.5kg from memory so 20ish with tyres.

[Eddy]

Hoyhoy.

My figures show that the 225/45/16 is about 10mm wider than the 215/50/15.
And you do need wider rims than the standards.
I went through 3 different width rims before finding the right one for the 225/45/16's, which ended up being 8".
The 225/45/16 is some controlled size tyre, can't remember what class.

[sambb]

Long time no hear Eddy. Good to see you're still lurking in the scene. Oh ok I thought there was a weird quirk with these where the higher aspect ratio of the 215's translated to a wider face despite the 215 designation but I probably got that wrong. Yeah I remember you ran those and yeah they are much more common than the 215/50 profile on the second hand market. I went with 15's initially because there were just no light motorsporty 16's getting around second hand that I could actually afford, and that has kind of locked me into a tyre size niche thats not as popular as 225/45/16.

[Sydneykid]

Hoyhoy.
My figures show that the 225/45/16 is about 10mm wider than the 215/50/15.ximum allowed rim doamter)
And you do need wider rims than the standards.
I went through 3 different width rims before finding the right one for the 225/45/16's, which ended up being 8".
The 225/45/16 is some controlled size tyre, can't remember what class.

The 225/45/16's work OK on a 7" rim but an 8" is marginally better.
The 225/45/16 in the A050 control tyre is the common size for early Commodores in Improved Production (16" is their max allowed rim diameter).
Tyre sizes (as stamped on the sidewall) are not always a good guide to actually dimensions. For example in A050's the 225/50/15 is actually 237 mm wide and the 225/45/16 is 224 mm wide.


Cheers
Gary

[Eddy]

The 225/45/16's work OK on a 7" rim but an 8" is marginally better.
The 225/45/16 in the A050 control tyre is the common size for early Commodores in Improved Production (16" is their max allowed rim diameter).
Tyre sizes (as stamped on the sidewall) are not always a good guide to actually dimensions. For example in A050's the 225/50/15 is actually 237 mm wide and the 225/45/16 is 224 mm wide.


Cheers
Gary

Hoyhoy.

Sam is comparing *215/50/15* to 225/45/16, I still come up with the latter being 10mm wider.
Actually on the calculator I'm using it has 225/50/15 & 225/45/16 as being the same width.
May be the AO50 is different for some reason.

[Sydneykid]

Hoyhoy.
Sam is comparing *215/50/15* to 225/45/16, I still come up with the latter being 10mm wider.
Actually on the calculator I'm using it has 225/50/15 & 225/45/16 as being the same width.
May be the AO50 is different for some reason.

In the A050 the 215/50/15 is actually 229 mm wide and I just measured a 225/45/16 and they are 227 mm wide. Which is what they are quoted as on the Yokohama tyre chart;
Advan A050 (Semi-Slick)

So the 225/45/16 is actually 2 mm narrower than the 215/50/16.

In A050's the 50 series (and higher) tend to be baggy in the sidewall which inflates their overall width. Under 50 series they are less baggy so the overall width is more in line with their tread width.

Cheers
Gary

[sambb]

I'm going to get this kind of driver coaching next time I'm on a circuit. What do you reckon he'd charge:

https://www.youtube.com/watch?v=_EaaygyhtVs