1987 3.2 Carrera Backdate project - Sladeys hotrod

[sladey]

Thanks - just to repeat I did copy the idea off Nige - credit where it’s due

[sladey]

OK so I’ve got a trip to Spain/Portugal planned for the end of May - I’m daily driving the car now and started thinking what I’d like to do in preparation for the trip

First thing is to get the engine/ECU set up properly again - it was last done probably about 6 years ago at Wayne Schofield (Chip Wizards). Since then I’ve not done anything major but I’ve got a new injector loom, new injectors, and the cold idling isn’ great so I think it would benefit for a tune-up. So I’ve booked it in with Wayne for the 6th May. I’ve got to try and keep up with the potentially 3 964RS’s on the trip!

The second thing is setting up the suspension again. I last had it done 3 years ago at Centre Gravity. Whenever I’ve done any work since then I’ve made a real effort not to disturb centre gravity’s settings - but it’s not always possible to be exact with this. Also just driving it can eventually knock things out of place - so I’m overdue a setup.

I really like Chris at Centre Gravity - he’s one of a tiny number of people that I’m happy to work on my car (Wayne Schofield being one of the others). It would be expensive to book it into CG. I think it’s value for money but I love to mess with things. The cost of setting up at CG is less good value for money if you bugger up the settings after 6 months and have to go back again.

So I started thinking along the lines of a DIY alignment. I know it’s not rocket science but I also appreciate its fiddly work. I wanted to buy some kit but not spend loads


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[sladey]

So I started looking at what kit I should get.

I want to be able to set Camber and tow at the rear, Camber, Castor and Toe at the front, and most important I want to be able to corner-weight the car.

Now I know there are plenty on this forum who know all about setting your car up. Not a problem and if you have any tips I’m happy to benefit from advice. If you aren’t sure though I’m going to go into the detail as much as I can and hopefully demystify the process for some of you.

So let’s start with corner weighting.

Corner weights are important because they set the car’s balance. If most of your weight is on the front right wheel then it will corner differently Turing left and right because the outside tyre has more or less work to do. Similarly if you brake in a straight line one wheel will have much less weight on it - possibly making it more likely to lock up. Similarly putting the power down when the weight on your rear tyres is uneven can make things a bit squirrelly because one wheel might be slipping while the other is gripping.

My understanding is that you can’t change the front/rear weight bias by corner balancing - more that the aim is to adjust the diagonals- the corner to corner weight. So in an ideal world FL weight plus RR weight would equal FR weight plus RL. Porsche’s spec is that the difference in the corner weights should be under 20KG. I think the adjustments can affect the side to side weight of the front or rear to a small degree.

You increase weight on one diagonal by raising either the front or rear on that diagonal. I thought it was as simple as you raise the RL and it increases the weight on the RL, but I’ve now read that this will also increase the weight on the FR. I’ll see how it goes. the last few times I’ve been to CG he got the diagonals to be no more than 1KG different.

Raising and lower my car is easier than on most as I’ve got coilovers all round with adjustable perches. Happy days.

So how do you weigh the corners then? With corner scales, obvs. However looking round these tend to start at around £800 and easily go up to several grand.

The motorsport scales are so expensive because they have to be able to handle several hundred

I wondered if there was a way you could use levers to let you achieve the same thing with a set of bathroom scales.

Some people managed this by just spreading the load and buying a load of scales



That seemed OK but I’d have to do some fabrication to make that work. If I’m fabricating I think I’d want something a bit cheaper (16 x £10 scales is still £160) and probably easier to use.

I looked around some more and eventually and found some pictures of something called Ruggles Scales - here’s a picture of how they work


As far as I know they aren’t commercially available but that’s OK. the basic idea is that you have the tyre resting on a plate that has a bar down the middle and then you set it up so that this bar is a third of the way along the lever from the fulcrum to the scales end - meaning that the scales can weigh up to 3 times their normal weight or to put it another way to get the real weight you just multiply the value shown on each scale by 3.

I liked this idea as I’d only need to buy 4 scales. I also wanted to make it out of steel that I had lying around - I’ve got a fair bit of 50x50 box section which is overkill but it’s there.

I’m short of angle iron so I order that and it arrived this afternoon.

Here’s where I’m at at the moment


The pivot point or fulcrum will be on the left hand side (underneath (obvs).

I’ll have another bar on the right hand side that will rest on the scales

That plate is 2mm thick stainless steel ( again it was lying around) - this is how that’s going to work - angle iron welded underneath so it rests on a bar - so I know exactly how far along from the fulcrum it is



I’m going away next week so won’t get a chance to weld them all up until a week on Saturday. I’ll update you all at that point.

In the meantime I’ll do another update on where I’ve got with Camber, Castor and Toe…..


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[rhd racer]

Very clever Mark. Don’t forget to replicate your weight in the driver’s seat. Sometimes you have to compromise a little on corner weights as the pure result can lead to a slightly unusual stance! Sometimes getting within a whisker is good enough, and be aware that adjusting one can impact the others so make small changes and leaving the locking collars loose til the very end!

Agree with both of your recommendations above having used both. In fact, am up with Mr Schofield on Monday setting up the new engine…..


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[911hillclimber]

I did my 911 totally a few years ago.
You end up iterating down to the accuracy you need, iirc I got to about 5 Kg across all the wheels with driver only weighting in the seats.
I was lucky and borrowed a set of pro scales from a hillclimber but it still took about 2 days to do the lot.
Hardest part was ensuring each scale was on a an even flat floor, my garage floor was miles out.

With the scales in place and 'shimmed' to level across them the car was on rotating pads and work began.

Every time you adjusted for weight and then geo symmetry the corners would change so around and around you go....patience is needed.

When Centre Gravity do it all in day my hat is off to them.

I found getting the right caster angle quite tricky and not sure today if each side is the same, but the car drives well.

Toe in etc all done using fishing line and calipers, cambers using a Dunlop mechanical gauge.

I think having good wheel plates on the scales an absolute must to stop the suspension binding.

Very satisfying to DIY this task.

I have the dubious credit of designing a set of digital scales for an F1 team in the early 80's!

[sladey]

Very clever Mark. Don’t forget to replicate your weight in the driver’s seat.

I’m ahead of you there

[sladey]

Yes I realise it’s going to be patience-trying. I’d like to get the stage where i can do it from scratch in a long week-end.

For the moment I’m focussing on having enough tools to be able to take measurements that are repeatable and believable.


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[jjeffries]

The Smart Strings kit/tool is excellent but I couldn’t afford so made my own (sort of) copy. We’ve probably all seen piccies of racing cars being aligned using strings (or fishing line). Camber/caster can be done with an iPhone although I forked out for a nice Longacre gauge. Like Hillclimber, I was able to borrow someone else’s proper scales. I work in the auto business and think we can all get a bit too intimidated by big Hunter or similar alignment machines. A bit like painting cars, where all the time is in the prep, the first time I did this (on my ‘82 SC), I spent forever creating level surfaces and buggering around with my strings. But the next time (my since departed ‘87 924S COVID project), it was repeatable and straightforward. I realize none of this is new-news, but a big thumbs-up for DIY alignments and set-up.

John

[sladey]

Thanks John - yes the smart string setup looks really good but very spendy.

I’ve opted for a DIY version which I’ve ordered from the USA.

I did some initial measurements using fishing wire and axles stands but I knocked one walking around so had to set it all up again. Also I was humming and ahhing about getting the strings aligned with the car. I measured off the hubs as mentioned in Ray Scruggs manual but then had to take the wheels off to measure the spacers thickness. It’s all a bit of a faff and as I said before I want something that is easier to set up and is repeatable

So I ordered these



They are from calipergarage.com in the US. I think it’s basically smartstrings kit without the poles - you then add the poles (plumbing fittings I think) yourself. I’ve got a lathe so will be able to put nice notches in the poles at specified distances. That should allow me to get the strings parallel to each other fairly consistently and hopefully fairly easily

So that will be toe-in covered - front and rear.

With regard to adjusting toe-in the front isn’t a problem but at the rear I’m running 935 spring plates which have their own adjuster screw so I’m hoping that will make it easier than the normal eccentric bolt

[911hillclimber]

Just a few thoughts Mark:
If you are just nipping thing up after a small tweek then great, but if you are taking most of it apart a realy good clean of the 'sliding surfaces' works wonders when pulling it all together. I think CG do this to get thier ultra fine positioning.

I found detarmining the centre of the car hard, but simply use the bonnet and tail gate latch holes as the C/L and i think that is ok.

My poles come from B&Q metal section stand, 10mm thin wall tubes, 2.5 meters wide and surprisingly straight.

Masking tape in the middle with a felt tip mark and then the marks at eack pole end the same of course and you have a good starting point.

Poles on 4 axle stands.
You are not the first to knock a stand in the middle of this task!

It will be interesting to see how you fare with those USA parts.

The line I use is red high tensile fishing line, possibly 0.3 mm diameter.

I use all the same stuff for the Lola too.

[Bootsy]

And subject of our Instagram page today https://www.instagram.com/p/DITJnhzoPR5 ... N3Y3E5N2Jo

[Bruce M]

I found the big difference in effort / efficiency was when i moved the poles from axle stands, to some form of mounting to the car. As you found, its very easy to knock the poles when moving around the car and very hard to not mess them up when you try to make some adjustments. With the pole hanging off the front / back of the car, you can jack up, adjust, drop & recheck very quickly. The car tends to move around on the floor, a little, when doing adjustments so the axle stand mounted poles need realigned frequently.

[Bruce M]

Big ziplock bags with a dollop of grease or oil inside are fairly effective as slip plates. If the concrete is rough, then a smooth tile or similar underneath will reduce damage to the bags.

[sladey]

And subject of our Instagram page today https://www.instagram.com/p/DITJnhzoPR5 ... N3Y3E5N2Jo

Thanks Thomas! My kids might actually believe I have some friends now it’s on insta

(Setting up for comment from Jason)

[sladey]

Thanks for the comments. I’ll let you know how the us parts are when they arrive.

In case anyone is completely new to this, here’s a bit more about toe-in and why it’s so important.

I am obviously not an expert - just someone who won’t accept that I can’t do something - and I’ve read a lot and watched a lot of YouTube vids.

This is what I understand (happy to be corrected)

toe-in is how much the front (and rear) wheels are toe’d in - (pigeon-toed ) or toed out (like a penguin)

If the rears are toe’d in slightly then if you take off and land or go over a big bump then It stays stable on landing - if they were toed out then it could get squirrelly.

With the fronts if they are toed out you get sharper turn-in with your steering - verging on the ‘snatchy’ and maybe twitchy at high speeds. If toed in you get stability at higher speeds and slightly less sharp steering turn in.

You measure it by running strings down the side of the car which needs to be exactly parallel with the car.

So how to find a line that is parallel with the car? One way is to measure out from the wheel hubs, with the knowledge that the rear hub is 3/4 of an inch narrower (on each side) than the front. So you measure, say, 2 and 3/4 inches out from the rear hub and 2 inches out from the front hub. You run your string between axle stands and position them so that the strings are in those two correct positions

The bar method means you have a framework of bars at the front and rear and which results in bars running across the front and rear of the car the centre of the bar is centred on the centre line of the car. You then run the strings the same distance from each end of the bar. This should also produce perfectly parallel strings that you can measure from.

When you are then measuring toe-in you are measuring the front and rear of each wheel against the string and that tells you whether they are pigeons or penguins. There are websites that convert the measurement into degrees and minutes (which is how toe-in is expressed)

I appreciate this is a lot of detail but the aim is to encourage more people to have a go or at least understand more of the theory about alignment.

Again very happy to be corrected if I am wrong (but don’t be a cont eh? )

I’ll come into turn plates, castor and camber next my