The $1,200 Miata

Dropping air pressure has absolutely helped the handling, but the vibration is still present.  Next up, I'm going to see about having Tire Discounters balance the tires on their Hunter machine.  I recall going through something like this on the Mazda 5 way back when - my usual tire store has a not-Hunter Roadforce machine and I guess the tires all balanced okay on that, but when TD put them on the Roadforce, the vibration stopped.

In other news, I got the new seat covers today and the color isn't exactly what I was hoping for, but it'll be fine.  I need to scare up the seat heaters that I have in storage over at the shop somewhere and get a hog ring pliers and some hog rings.

This weekend, I took the car down to Bowling Green via the long way to pick up my daughter, bring her home, and then made the round trip a second time to take her back to school.  Since October 1st, I've put just shy of 2,000 miles on the car!  Just making up for lost time, I guess!

If you have the 65 MPH "shimmy" i found the hunter road force down to 10 lbs (or less) helps alot, problem is finding a shop will to do the extra work to get down that low. I have searched the forums and found a thread here where Keith T. (here on GRMS forms) had adjusted someones PPF/pinion angle to 66 mm from the top of the PPF to the plane at the frame rails (straight edge across frame rails). I adjusted mine from 60 mm to around 65 (slipped when tightening the PPF to trans bolts back up) and my shimmy is almost completely gone. May be worth a try.

In reply to David_H :

I did set the PPF alignment when I put the first driveshaft on...  and took it back off...  but it would be worth double-checking it.  I was pretty frustrated at the time, so it's possible that I didn't take a good measurement.

A question for you though...  When you say to "take it down that low" to 10lb or less on the Roadforce machine, what do you mean by that?  I want to be able to converse intelligently with the shop and I'm not familiar with what a Roadforce machine does that a static balancer doesn't other than somehow simulating pressure from the pavement or something like that.

Feel free to stop by and steal the wheels off my Miata for a short stretch too, to confirm if it's the wheels/tires or something else.

In reply to wae :

Roadforce simulates the force exerted on the tire when it rolls on the road by applying a controlled load of some amount (1000 lbs or more), the lower the force number the better the balance, most vehicles are fine with the standard 40-20 lb balance but with the NA being extra sensitive 10lbs or less gives the best results.

Deeper dive here

roadforce

In reply to David_H :

Thanks for the explainer!  I've gone ahead and made an appointment to have a local shop put them on their machine tomorrow.  Interestingly, I called three shops and the first two said that while they did have Road Force machines, they were down and "Hunter was having some problems". 

In reply to eastsideTim :

I appreciate the offer to borrow your wheels and tires...  If the balancing job doesn't get it done and the PPF measurement is in spec, I will probably take you up on that.

Good news and bad news!

They threw the wheels on the Hunter machine and the balance was off on all of them, so they corrected that on three of the four.  The fourth, however, they balanced up as best as they could, but it's got a pretty decent bend to it so I'm going to need to replace it.  The vibration is signficantly reduced at this point, so that's good, but I've got to add "source another daisy" to my to-do list.

wae said:

You autocross people have let this whole classing thing get a little out of hand.  There's a million different classes, then index classes, novice classes, ladies' classes, and what the everloving berkeley is a PAX??  As far as I'm concerned, I'm Stock Rear.  Anyway, the car is completely uncompetitive since it's just running on 14" General Altimax tires and has absolutely no modifications or tuning of any sort, plus the suspension is more than likely whatever it left Hiroshima with 27 years ago. 

But it's gonna be fun!

Late to this but I will say WOR is not as complicated.  Our November 3rd fun/charity event is getting rolled into Cincy that weekend at Trader's world now, and looking up their system, yeah.  WOR just uses the regular SCCA classes (Street ST Prep Mod etc), and PAX.  (But definitely more than RX for sure.)

Daisies are pretty cheap/available from Treasure Coast Miata, or other Spec Miata breakers. Not too bad to ship one, either. (Of course, it is likely you already know this bombshell of information). Hopefully that gets you straight.

We are a number of hours away but I believe I have three (3) daisies sitting in my basement... I have to imagine one is straight enough for you.

I'd happily trade you one just so I can keep a set of rollers. 

Jerry said:

wae said:

You autocross people have let this whole classing thing get a little out of hand.  There's a million different classes, then index classes, novice classes, ladies' classes, and what the everloving berkeley is a PAX??  As far as I'm concerned, I'm Stock Rear.  Anyway, the car is completely uncompetitive since it's just running on 14" General Altimax tires and has absolutely no modifications or tuning of any sort, plus the suspension is more than likely whatever it left Hiroshima with 27 years ago. 

But it's gonna be fun!

Late to this but I will say WOR is not as complicated.  Our November 3rd fun/charity event is getting rolled into Cincy that weekend at Trader's world now, and looking up their system, yeah.  WOR just uses the regular SCCA classes (Street ST Prep Mod etc), and PAX.  (But definitely more than RX for sure.)

I was originally thinking about going to that event - I really want to see how much better the car is with proper tire pressures and stuff - but if everything goes right, I think we're going to wind up taking our first camping trip of the year (!!) that weekend.  I always did like running with WOR's autoX group.  Having an autoX on the figure-8 track at Kil-Kare was always pretty awesome!

AxeHealey said:

We are a number of hours away but I believe I have three (3) daisies sitting in my basement... I have to imagine one is straight enough for you.

I'd happily trade you one just so I can keep a set of rollers. 

Oh wow!  Thank you!  Well, it just so happens that I will be in the general neighborhood before too long.  We'll be up in Canton to see my wife's side of the family the week before Christmas.  That would give me time to pull the wheel off, have the tire dismounted, and I could bring that bad boy up with me then.

wheelsmithy (Joe-with-an-L) said:

Hopefully that gets you straight.

So to speak! hehe

Yeah, the biggest problem I've seen with daises is finding someone with just 1!  There are a couple people on FBM selling sets of them for pretty cheap, but I've got so many damned wheels and tires hanging around, I'd like to not get any more than I really need.  Heck, I need to unload the alloys that came on the car when I bought it still...

wae said:

 

......  Heck, I need to unload the alloys that came on the car when I bought it still...

They wouldn't  happen to be 15" x 7", would they?

Indy - Guy said:

wae said:

 

......  Heck, I need to unload the alloys that came on the car when I bought it still...

They wouldn't  happen to be 15" x 7", would they?

Unfortunately, no.  I don't know how wide they are, but they're 14s.

In reply to wae :

Just keep me updated of schedule/etc. I don't know the balance of any of them but I could choose the prettiest one and have the tire pulled off to be ready for you. 

Feel free to shoot me a PM to coordinate rather than clog up your thread here.