GSlender's Track Beeotch!

[gslender]

It's already as low as it should be for a track like Lakeside. Need a decent amount of suspension travel.

Well, I've gone for these settings (the race alignment) and the front is 100 mm at the pinch welds (3.9" in the old stuff).

http://949racing.com/miata-race-alignment-info.aspx

Not sure if that's "too low" as you're suggesting, but I'll find out soon enough.....!!

[Magpie]

100mm at the pinch welds is VERY low there are a few things under the car that will be very close to the road. Further a rough guess the front of the car will be about 5mm closer to the ground due to the rake (assuming the rake is about 0.20 deg). At that height you will have bump steer issues unless your tie rods (or other parts) have been modified to get the geometry back to how it was designed.

I run about 125mm at the pinch welds (with zero rake) and have clearance issues. 125mm at the pinch welds equates to about 95mm at the front below the splitter. There is not much change to toe in/out on my car through the range of suspension movement.

[gslender]

100mm at the pinch welds is VERY low there are a few things under the car that will be very close to the road. Further a rough guess the front of the car will be about 5mm closer to the ground due to the rake (assuming the rake is about 0.20 deg). At that height you will have bump steer issues unless your tie rods (or other parts) have been modified to get the geometry back to how it was designed.

I run about 125mm at the pinch welds (with zero rake) and have clearance issues. 125mm at the pinch welds equates to about 95mm at the front below the splitter. There is not much change to toe in/out on my car through the range of suspension movement.

Mark, those settings are proven at the track by hundreds and hundreds of Miata's racing in the USA. I'm sure everything you've said is true (ie yep it is low, and yep on the road you'll have clearance issues) but I'm not going to assume the SpecMiata race setup is crap and they have no clue. Oh, and they run with mostly stock cars, with minimal changes due to the class they run.

I'll admit I'm curious to see how it handles, but again, the Spec Miata settings are proven and well documented. You'd be hard up to make broad assumptions about how those settings aren't valid.

[Magpie]

Yep I agree that those numbers are great for the track but difficult to live with on normal roads.

Spec Miata also allows the changing of tie rod ends to the LE part number and this fixes up some of the bump steer issues with going that low. Rule 15.14 - All cars are permitted to use the “R” model tie rod ends part # N021-32-280A. In addition rule 16.3 allows for the steering rack to be shimmed, this helps reduce bump steer as well, Further Spec Miata allows the use of threaded Sleeves and Spring Perches (rule 15.2) so the correct suspension lengths can be set to match wheel travel. Wheels (rule 17) in Spec Miata are restricted to 15" dia and 7" and tyres 205/50/15 (rule 17.2) hence the alignment settings.

No broad assumptions by me. 949 does have the following comment "These settings may not be compatible with your vehicle, driving style or conditions." as well as "To maximize the performance you need to test, test, test", you have 10kg/mm front springs and a 25mm front sway bar.

Have a chat with Accurate Suspension and get a custom alignment designed to work with YOUR car, YOUR tyres and YOUR driving ability/style and the roads YOU drive on.

[gslender]

Well, until someone who is doing consistently good times and many others have followed and get the same results, I will probably start with the Spec Miata settings and see how it goes.

If my times improve and it feels stable then I will stick with it, if not then I will think about changing something.

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[plohl]

I don't like how ken prefers more camber in the rear. I found I would need to stiffen the rear up too much to stop it understeering. Plus it made my set up completely different between the dirt sprints and the track. Found something along the lines of the 949 spec works well. The 949 allignment specs are the best place to start I think.

So 62s next outing at lakeside g?

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[Dan]

I don't like how ken prefers more camber in the rear. I found I would need to stiffen the rear up too much to stop it understeering.

If more rear camber is increasing understeer the extra camber is getting the tyre in better contact with the track which is what you want isn't it?

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[plohl]

It depends on camber curves. The rear gains more camber than the front for the same amount of roll. Fatcat motorsport did a write up on miata.net about it which gives a good explanation.
I think that's why you generally see na/nb alignments with more front camber.


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[Dan]

Yeh camber settings will depend on the camber curve, regardless of what the curve is though the objective of setting camber is to get the tyre to have the greatest amount of contact with the track. An easy way for us ametuers to try to get to the optimum camber setting is by reading the tyres and looking at the temperature distribution across the tyre.

Understeer/oversteer is best tuned through other mechanisms like damping/spring/sways.

Obviously those same tools to control the cars handling characteristics will influence the camber curve so you need to think of the whole set up as an interconnected system and when you change one you need to test to figure out how to adjust the other.

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[plohl]

Yep

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[Magpie]

I'm not a fast driver so my comments should be taken with a grain of salt.

[madjak]

My car is pretty much set up to 949's specs or as close as I could get to it. 100mm (or slightly less) at the front pinch welds with the back a bit higher.

For hillclimb and sprint events where you need to launch, you can't push the rear camber up past around -3 degrees otherwise you don't get enough rear grip for take off. In fact I think I'm at slightly less now as I was wearing out the inner edges on my launches. If it was just a track car you run much higher camber so that the cornering is improved a bit at the slight loss of forwards traction and braking.

I also run zero toe front and rear and I have a 22mm Mazdaspeed solid front sway bar, and 11mm rear. All up I'm fairly happy with the setup, however getting it on an off a trailer without hitting the splitter is pretty much impossible. I'm thinking of adding a bit more toe in on the rear to help with power oversteer but I need a test day on the track to trial it.

I kinda think that amateur drivers just need to get the car in the ballpark and then drive around the limits of the car and slowly refine. It's very hard to measure benefits or negatives without back to back testing. I think the 949 racing specs are close enough for most of use until you get serious and start testing tyre temps etc.

Btw I just made up a jig for wheel alignments. Basically two equal length ally bars hung from the boot and bumper with a string line between. It's much more accurate than me sighting down the wheel walls to "measure" the toe! I'll post some pics.

Rick

[Magpie]

Agree Madjak (and others) the 949 settings are a good place to start.

I'll retreat back to my build thread (tucks tail between legs and slinks away)

[gslender]

Guards are rolled, and with the neg camber on the fronts as they are, it looks unlikely that I'll have much tyre/panel contact going forward.... at least I'm hoping not!!

G

[toppertee]

Guards are rolled, and with the neg camber on the fronts as they are, it looks unlikely that I'll have much tyre/panel contact going forward.... at least I'm hoping not!!

G

You could always man up and use the slide hammer....