Let's talk about tracking - The Hunter Hawkeye

alex yates said:

As some may know I went to the local Kwik Fit the other day to have my alignment done and check out the Hunter Hawkeye system. Thought I'd do a little write-up about my observations and also maybe have a discussion on the system. I'll maybe do a write-up on my actual car's tracking as it's for a different discussion to this.

So, once I drove my car up on the ramps and the Kwik fit fitter swiftly closed the doors behind me (as he believed leaving the doors open fluctuated the readings) and we were on to the computer to start the process. Within minutes I was presented with a screen with all the parameters the machine measures and the tolerance bands for each one. They went something like this:

Front

Camber - 0 to minus 30 minutes
Caster - 8 degrees +/- 30 minutes
Toe - 0 to 5 minutes

Rear

Camber - minus 55 minutes to minus 1 degree 25 minutes
Toe - plus 5 minutes to plus 15 minutes

These are for the Carrera 4 996 and obviously other models differ.

Now my initial observation before we even did anything was, the international general rule of thumb of any measuring system is it MUST be 10 times more accurate than the tolerance band being measured. Anyone who knows anything about measuring will dismiss any measuring system not capable of doing so. It wouldn't even get through the front door of a quality department. So, the tolerance band of the front Toe is 5 minutes (and rear 10 minutes). The incremental resolution of the Hunter Hawkeye is 1 minute (on the display). Obviously 10 times more accurate that a 5 minute tolerance band would be an accuracy of 30 seconds. Or to put it the other way, the smallest tolerance band the Hunter Hawkeye would be deemed acceptable to measure would be a 10 minute tolerance band. So not acceptable to measure the front Toe and only borderline to measure the rear Toe. I think we can accept it is acceptable to measure the Camber and Castor as their tolerance bands are much greater.

On to getting some measurements. The fitter fit the wheel target quick grip adaptors. Now these just hook on over the tyres holding the adaptors flat against the alloys. There didn't seem any need to ensure they were sat central against the wheel but the fitter did check they were flat up against the wheel and in my case sat against all 5 knuckles of each spoke. Once all 5 are fitted the fitter then has to do some sort of process where I can only presume the overhead camera that do the measuring are setting some form of Datums to work from as the fitter turns the steering lock to lock (without engine running so no power steering) and then roll the car forwards until the computer says stop.
Once this process has been done, the computer then goes through the process on measuring all the parameter of alignment. I don't know how the software is written so don't know whether the program can compensate the the wheel adaptors not being central or any slight run-out of a face of an alloy wheel. A quick bit of trigonometry tells us that over a distance of 200mm (say the diameter of where the adaptor sits on the alloy) 5 minutes equates to around 0.3mm - not much!
Once all measurement are taken, the fitter then goes through each corner turning the relevant nuts and bolts (shown on the computer) until the reading goes from the red (out of spec.) into the green. All very simple and interesting to watch as each adjustment is made. Once all adjustments are made, the fitter then hits 'print' and the printer churns out a nice diagram of 'before' and 'after' of all parameters measured. All very interesting and good visual graphics to explain to the greatest novice what's actually being measured and adjusted. Pay the bill and you're on your way.

The deal was free check. £50 for any front end adjustment, £25 for each rear wheel adjustment (So £100 if any front and both rears need a tickle). For £120 you have a 2 year warranty with as many checks in that time window you want and 8 checks where adjustments are made, however much adjusting needs on each check. This can be done by driving in to any UK Kwik Fit establishment with a Hunter with just your name and reg. plate.
Obviously I took this deal out, especially when we were unable to get every parameter in spec.

Now a few questions from me that aren't addressed by Kwik Fit, Porsche, Hunter's website or anywhere else I had a quick browse on the web:

1. How can a system not deemed acceptable to measure some of the parameters be acceptable?
2. Does tyre pressures influence the readings of the system?
3. Should the car have a full tank of fuel, or empty, or halfway - would this influence the readings?
4. How repeatable is the system?
5. Define accuracy as all that's stated by Hunter is it's accurate?

After the fitter had finished making adjustments and we were happy with the results, I asked him to reset the computer, re enter model, etc. and do the test again. The results were different - to the point that some in spec. were now out of spec. :dont know:
I'm talking differences of 7 minutes to 20 minutes on rear LH Toe. 1 minute to 7 minutes on rear RH Toe. Also 1 minute and 5 minute discrepancy on both rear Cambers.
In a couple of weeks I'll bob in again for a free check and see what results they give me then.....also I'm due some new back tyres soon so will bob in again once those are fitted.

Hunter's USP seems to be "Other wheel alignment machines don't come close to matching the productivity and profit enhancing power of the HawkEye Elite® wheel alignment machine." "Say goodbye to wasted shop time"

Most guff on their website seems to be about speed and profit and not much in terms of accuracy. :dont know:

Now I'm in no way saying this isn't the best system on the market, or even rubbish, but just want to get my head around the importance of the accuracy of this kit and also the tolerance bands Porsche specify that the car should be within. Is it all smoke and mirrors, is the equipment capable, are the specs. baloney?? :?

Discuss.

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Hi Alex , hope you are well. I can answer these questions below for you.

1. How can a system not deemed acceptable to measure some of the parameters be acceptable?

I agree with the 10 - however 1 minute toe is fine - if you had 30 seconds it would be a nightmare to adjust. This is why all machines are to 1 minute - there is balance to time and accuracy.

2. Does tyre pressures influence the readings of the system?
3. Should the car have a full tank of fuel, or empty, or halfway - would this influence the readings?

So first and foremost
- all Porsche tolerance settings are based on a full tank of fuel, screenwash full, spare wheel, toolkit and no one present in the car
- all tyre pressures should be at Porsche recommended setting before rolling on to the machine.
- if tyre pressure is wrong - it will absolutely affect settings that are displayed
- if fuel is not full tank, or spare wheel or tool kit missing then it will affect the settings displayed.

4. How repeatable is the system?

If you set it and roll it back off, it should be the same. We have a beissbarth 3d machine but our wheel sensors are either clip on to the rim (since tyres can have different depths or if centre locks) or remove the wheel caps and we have wheel sensors that bolt into that space.

5. Define accuracy as all that's stated by Hunter is it's accurate?

It should be accurate setitng aside that example on your car re 5m toe.

The tolerance is to take account of wear and tear in terms of all suspension components etc e.g. bushes from one side might be different, which is why in suspension you replace in pairs generally.


Hope that helps.

If you would like (or others) a detail description of the differences between a geometry like at Kwitfit to bring into tolerances (Porsche) and a geometry like we do or Chris does ( I know Chris very well and chat regularly) I would be more than happy to explain when I have some time available on here.

That explanation would cover understanding of whether corner weighting is necessary, how a good set works and so on.

Ken

Hi Ken,

I'm great thanks, likewise.

Thanks for the informative post. If you do get time it would be great to read more information on the matter.

Much appreciated :thumbs:

As this maybe a long topic with lots of questions I'll add sections in rather than pages and pages of content. Before discussing the merits of changing geo settings on cars maybe let's address weight of a car, corner weighting and so on and how that affects handling. I'll write as simple as possible and assume no knowledge.

Weight distribution and how it affects cars handling.

Let's start with weight transfer. Let's imagine that unless otherwise stated below that the car has a weight distribution of 50:50 - so if you put it on a scales and the car weighs 1000kg, you would have 250kg at each corner, with 500kg at the front and 500kg at the rear.

Imagine (sorry I don't have a picture) a car that is completely clear to look at it. Now imagine it is half full of water.
- when you accelerate in a straight line, the water transfers from a flat line to a reduction in water at the front of centre, and an increase in water to the rear.
- it does the opposite when you brake in a straight line.
- so when accelerating the front is lighter than stationery and when you brake the front is heavier than stationery.

Now in a straight line you have stability in both accelerating and braking, because the water (weight) of the car is uniform. By this I mean that it is applied the same across the axles. All four wheels are having the same pressure even if the fronts are different to the rears.

You now approach a corner. Imagine the water in the car. Let's say a right hand bend. So there are a number of different situations now but if you are at a constant throttle through the right hand bend, the water will move to the near side (n/s - left) of the car. It will be pretty much uniform spread across from the off side (o/s - right) of the car to the n/s. There will still be water on all four tyres, but different levels and therefore weight and the speed of the car will impact. Grip on the o/s will be less because weight has been shifted to the n/s.

Now take the same above, and the driver panic brakes during the middle of the bend – maybe going too fast. Imagine the water in the car. So it transfers from right to left, but because you brake, water moves towards the front o/s wheel. If you brake hard enough you can remove the water from the rear of the car, and the car will pivot on the front, the rear will be lighter, and the rear will come around and try to swop with the front.

The above is made worse when for example the weight distribution of the car is at the front, and the car is Rear Wheel Drive (RWD). Let's say the car is 60:40 distribution because of the weight of the engine at the front, and if the driver panic brakes in the corner, not only does that distribution shift more, you lose grip on the rear wheels that drive the car. The classic oversteer situation.

How is this relevant to geometry?

Most Porsche is around 40:60 but some models can be 30:70
- so thinking back to the 50:50 situation, a car with 30:70 is going to have less weight over the front tyres on turn in
- this is why generally with Porsche tolerances set that the car will understeer through a corner when pushing on
- but you can through your driving, shift weight to the front of the car during a corner
- this is basically the term of 'trail braking' - in simple terms by braking in the corner to the apex, you shift weight to the front to enable better grip and turn in and reduce understeer.
- trailing braking requires you to carry more speed
- it is basically balancing the car

Now we know the fuel tank is at the front. Fuel has a weight - approx 0.75kg per litre. Let's make this simple and say the car has 60l tank.

When the car is full of fuel and you go around the corner, you have 45kg of weight extra when compared to having a near empty tank.

That difference in fuel is very noticeable on track. Forget about tyres going off etc, you would notice the difference in turn in with a full tank of fuel against a near empty tank - I am making the assumption that when the car was set up, regardless of the geometry settings, that it had a full tank of fuel.

How much you will notice will depend on weight distribution. On a 50:50 not so much. But on a 30:70 you would notice more. You want weight over the front on turn in when the car is lighter at the front than rear.

So to address the situation re corner weighting - a cup car is allowed 10kg difference across an axle. Some people ask why when you do corner weighting is it not the exact same weight. It is not always easy to get precisely the same weight on each axle corner, but generally 5-10kgs is a good tolerance.

So, the question was asked about having someone in the car (or simulating ) balast etc when doing a geo. The Porsche tolerances are as I mentioned earlier on the assumption that no one is in the car. And that is fine for general road driving.

If you are going to be the only person in the car generally, then let's say you weigh 80kg, you can see how in the car water weight example that you now have that additional weight in the n/s front to n/s middle of the car.

If you corner weight then clearly that would make it better. But then you put your partner or friend in the car and the weight changes again.

If we are doing a geometry with corner weights and the car is track focused, then corner weighting to the drivers' weight is a good thing. At the same time, it also comes down to the drivers' ability to get the most out of the set up - if I gave two cars to the same driver with or without cornering weighting, the amount of difference the driver would notice would probably be down to how good a driver they are.

Back to the fuel tank, you could set up with 1/2 a tank as well but even if you set up with a full tank, as the fuel reduces, so will the weight over the front, and driver should be able to compensate for that.

One final part about weight and geometry. Rake.

So looking at the car sideways on, rake is the angle of attack through the car. If you raise the ride heights on the rear and lower the front, you increase the weight to the front. It impacts other things like drag as well and downforce, but you can see that the weight can be shifted as well. If you add for example a bigger rear wing, if that adds downforce, that affects how the car handles and so on - pushing down gives you the same

It is important to understand weight distribution before getting on to geometry adjustments. Geometry adjustments can transform a car's handling as long as the driver also understands weight distribution - you cannot assume that every person knows how to trail brake for example – if you set the car up on the basis of trailing braking, someone that does not trail brake will think the car handles poorly. It is why one of the critical criteria of a good geometry (outside of Porsche tolerances) to understand the driver.

Next time we will look at geometry and how this impacts handling......

Ken

loved reading that Ken :thumb: look forward to part 2 :grin: :thumb:

Phil 997 said:

loved reading that Ken :thumb: look forward to part 2 :grin: :thumb:

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+1!

Respect Ken - thank you very much. Looking forward to the next instalment.

In other news, Alex had a blow-out on a rear tyre tonight, then drove home at high speed before realising. Thought the handling seemed to go a bit (lot) poor on the way home. Anyway, rear tyre is most likely mullered (as I smoked all the neighbours out on my return) so I've just ordered a couple of new tyres for the rear. Fitted on Friday, so will possibly go and have another check done once they're on.

One of my best mates is a private large general garage and likes his quality equipment. Amongst other things he has a Hunter alignment machine. I was fortunate enough to sit in on the training of one of his new members of staff a few years ago on the use of the machine because it interested me. I certainly don't know all of the in's and out's and do not consider myself an expert but have been able to experiment with the machine and my own cars so can answer some of the questions relating to that machine.

1. How can a system not deemed acceptable to measure some of the parameters be acceptable?
2. Does tyre pressures influence the readings of the system?
Yes they do have an influence and should be set correctly.
3. Should the car have a full tank of fuel, or empty, or halfway - would this influence the readings?
Yes it has an influence. Hunter recommend a full tank a fuel and my friends machine has balast weights that can be put on the drivers seat to simulate the drivers weight. When the car is put on the machine, you load the program for the model you are doing and then follow the guide. This includes setting tyre pressures, checking heights and other dimensions are within tolerance before mounting the units on the wheels. You then roll the car forward which calibrates the machine for any discrepancy in the mounting of the unit on the wheel/tyre.
4. How repeatable is the system?
It is repeatable but the mounting of the tyre/wheel units, the roll forward and then steering calibration make a difference, down to the operator.My friend also has his machine calibrated every six months and it was the calibrator from Hunter that provided the training I saw.
5. Define accuracy as all that's stated by Hunter is it's accurate?

For me, the results can be as good as the operator and the time allowed. I could easily repeat settings provided by somebody else on my car, whether copying CG or anybody else. If you want a stock or know what settings you want, you could take those settings to a guy with a Hunter and they should be able to repeat them (assuming they are within the cars tolerances). The Hunter could also be loaded with specific settings to achieve, for example my friends garage does a number of drift cars.
I have been told that kwik fit use internal trainers that train managers that train staff etc so perhaps bits get lost along the way...
I believe that CG's strength is the ability to recognise parts that are past their best but not obviously failed, as I'm sure 9e could do also. But also there depth of knowledge if you want a certain type of ride and that's due to their experience in the models.

Last week I decided it would be a good idea for all my alloys to look mullered rather then just the passenger side, so I ran into a kerb on the drivers side, dinged both alloys and blew a 1.5 inch square hole in the side of my rear tyre :frustrated:

New rubber fitted last Friday so thought I'd get the alignment checked out today as it's free of charge and also want to ensure my alignment isn't way out of whack.

Visit to my local Kwik-fit and it's soon up in the air with the Hunter Hawkeye taking measurements. I expected my tracking to possibly be out on the driver's side front wheel and possibly some variation on the rear wheel Camber & Toe, even though the car drove straight with the wheel straight and nothing felt any different.

1st check and the tracking is out on the front with both front wheels pointing to the right (driver's side further out of spec than passenger. Rear Toe on both rear wheels now pointing more to the right and out of spec. I told him not to touch the back but just to realign my tracking on the front. He did this and adjusted both track arms bringing the Toe back into spec.

I get a print-off, jump in my car and I'm on my way. Less than a mile down the road and I'm now realising my steering wheel is at around a 10 degree angle to the left to make the car drive in a straight line, so I immediately drive back down there. The Technician puts the car back up on the rig, fits the wheel sensors, goes through the process and the readings come up on the screen. The rear end is almost back to where it was after they'd done their adjustments 11 days ago. The fronts are around 13 minutes away from the readings just taken and both (obviously) are out of spec. and pointing in the same direction - to the right. The Technician re-adjusts the tracking arms and brings the Toe on each front wheel back into spec. I ask him how that's happened and he just shrugs his shoulders and says pass.

For the second time, I jump in my car and I'm on my way. Steering wheel now seems bob on when car drives in a straight line. I can only assume it's now correct and looking at the results from each check, I'd guess that something is not lined up right on the system as the deviation in degrees on each axle from side to side is repeatable (ish) on each check but showing in a different position each time.

My (Quality Engineer) mate reckons these tracking machines are no good and can not fathom out where they set their Datums from when they do a check.......and without having a correct Datum, you're p**sing in the wind. I must say, I'm leaning towards his theory. From what I can see, it's one or both of 2 things: A) It's not able to establish a correct Datum to work from.....or B) It is by no means fool proof and the simplest of errors created by the user makes all the data useless........or both.

:what:

The first result in my experience is the steering wheel slipping from the centered position during the toe alignment.

rhino-man said:

The first result in my experience is the steering wheel slipping from the centered position during the toe alignment.

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Most likely. My thought too, but makes it a pretty poor system when something so simple is not made idiot proof.

But would the steering wheel not be centred perfectly alter the results on the rear wheels?? :dont know: