NC1: search for comfort on bad roads

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NC1: search for comfort on bad roads

Postby AndrewP061 » Sun Feb 02, 2014 3:34 pm

Hello Brian,

I'm new to this forum and appreciate the opportunity to participate.

I recently purchased a 2008 GT PRHT (no sport package).
She has 37k miles and as checked out by a mechanic before the sale, is in excellent condition.
My previous long term driving experience is 20 years with a 94 corolla (300k) and some time with a 88 RX-7.

I test drove many NCs and a few RX8s in December in Raleigh NC. And although thought the RX8 rode a tad bit better, have wanted this particular NC since it came out.

While in NC I thought my new car rode better than my corolla ( obviously handled better). Even over speed bumps. Loved the car.

I drove it back to Southern Il/IN where I teach part of the year. The car was excellent from NC through the West VA mountains. However, as I approached IN through and past Louisville, I actually became quite scared.

When hitting certain expansion joints into small bridges on the interstate, at times I felt like I may lose control of the car. Either the car would be re-directed hard left or right, or the car would almost leap into the air. Then when the pavement became consistently torn up, I just started slowing down to 50mph as my nerves would be completely shot (slam slam as if no suspension at all).
I have since learned to hold the wheel more lightly, but.....

On smooth twisty roads this car is my dream, but on the typical highways and interstates in the Midwest this car has become my nightmare. The RX7 was never like this. Even my old corolla isn't this bad (original suspension). I drive at least 200 miles a week on such roads. During my usual job commute, only 4 miles, I'm just driving the old corolla.

Yes, I've done lots of reading on NC suspensions. But little talk of Comfort first. I regularly will make long trips back to the south.

I agree the NC could handle better but I would like the best ride on bad pavement with little drop in clearance.

I assume that I am both underdamped and under sprung for such roads?

FCM seams to be very expensive and a long wait.
The Ohlins sound great, but must wait for them and you mentioned they may be more than necessary.
The progress springs sound good but appear to be sprung only slightly more than stock, and if I wanted the tokicos, they appear to be out of stock indefinitely.

Your advice would be much appreciated.

Oh, tires are nearly new 205/45 17 Michelin pilot sport a/s plus. Running psi 29. I've tried down to 26 with minimal difference. She does ride a bit better when it's above freezing.

Thank you,

Andrew
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Re: NC1: search for comfort on bad roads

Postby Brian » Mon Feb 03, 2014 8:43 am

Welcome.

My suggestion is check around for customer selling the 16 inch factory wheels that this car also came with, those should improve the ride quite a bit. All the spring changes are going to be more firm. You are getting close to shock replacement time anyway, shocks may be about ready for replacement and you can do some KONI SPORT shocks for better control of the factory springs and the FCM COMFORT bumpstops. That would lower the car about half an inch and give much better damping.
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Re: NC1: search for comfort on bad roads

Postby skeeler » Mon Feb 03, 2014 2:12 pm

You might also want to get a good alignment to your specs (not the rather broad range Mazda considers acceptable). You'll find lots of discussion of NC alignments here and at Miata.net.

Brian is right that 205/50-16s tires on the stock 16x6.5 wheels will feel a lot softer. You should be able to find someone selling the stock wheels, having upgraded to something else.
2009, STR & DD. 1995, HPDE. 2004 MSM, sold. 2010 Mazda3, hers.
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Re: NC1: search for comfort on bad roads

Postby Brian » Mon Feb 03, 2014 2:30 pm

That point about alignment is a good point, could easily be a mess as you got it. If, for example, rear is TOE out and front is TOE IN then that would make the car feel unstable. My guess is that the numbers don't match left to right.
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Re: NC1: search for comfort on bad roads

Postby skeeler » Mon Feb 03, 2014 2:42 pm

I often say that a good alignment is the best bang-per-buck handling improvement you can make, especially on a car with unknown history.
2009, STR & DD. 1995, HPDE. 2004 MSM, sold. 2010 Mazda3, hers.
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Re: NC1: search for comfort on bad roads

Postby AndrewP061 » Mon Feb 03, 2014 2:56 pm

Thank you all.

I had planned to do an alignment, but the dealership almost refused to saying, "they were very well set up from the factory." (well, the car is 6 years old, who knows what's been done). I will have this done with moderate toe-in back and front.

Suggesting the 50s series on the 16" sounds good. However, when replacing the tires, would going to a 225 or 205/50 increase the sidewall on the 17" enough to make a difference? (unfortunately, tires are great and very new...expensive, hate to replace so quickly).

In addition to the crazy rough ride, on a moderately smooth surface, she will "pogo" a bit. So, new shocks definitely.

Brian suggested keeping the stock springs. However, everyone complains of how soggy they are. I've been wondering if half my problem hasn't been "slamming" into the bumpstops all the time and therefore stiffer springs would help as well? Or will the comfort bumpstops truly save me?

Finally, regarding going to smaller wheels. Obviously used stocks would be cheaper, but perhaps lighter wheels would help. Instead of going to 16", would just going to lighter 17" wheels do the trick? I'm trying to interpolate whether it's the smaller wheel, taller sidewall, or lighter wheel that is "implied" here to make the biggest difference.

If I went to 16" wheels, was it implied that I would get a tall enough tire to compensate for the speedo? which would therefore soften the ride?

It's interesting; a firm ride doesn't bother me. This is something else. I thought I would be upgrading the car for performance at this point.

Thanks again all. I welcome any thoughts.
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Re: NC1: search for comfort on bad roads

Postby skeeler » Mon Feb 03, 2014 3:18 pm

In my opinion, 225 street tires would be way to wide for the stock 17x7 wheels. They'd be very sloppy.

205/50-17s would increase your outer diameter. The additional sidewall would give you more cushion, but it would hurt your acceleration and unsprung weight.

205/50-16 is a stock tire size, and the OD is very close to the 205/45-17s you have now, so the speedo won't change much. You can do the calculation yourself if you know how to read tire sizes.

I think Brian's suggestion of the stock 16s was aimed principally at adding more sidewall. The stock 16-inch wheel/tire setup is the same weight as the stock 17-inch combination, so you won't save any unsprung weight going to that.

Lower unsprung weight always helps the suspension respond, so it helps both ride and handling. I'm not sure if you will get enough benefit to warrant the expense, though. That said, there are some very light 16x6.5 and 16x7 wheels out there, and Brian offers a number of 17x7 and 17x7.5 wheels that will save you 2-3 pounds per corner. Example:

http://www.good-win-racing.com/Mazda-Pe ... 290NC.html

I still say you should start with a good alignment.
2009, STR & DD. 1995, HPDE. 2004 MSM, sold. 2010 Mazda3, hers.
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Re: NC1: search for comfort on bad roads

Postby Brian » Tue Feb 04, 2014 9:16 am

Yes, given this customer's choice of words about need for more comfort I am hesitant to suggest stiffer springs.
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Re: NC1: search for comfort on bad roads

Postby AndrewP061 » Tue Feb 04, 2014 12:44 pm

Hello,

Thank you all for the information.

I am leaning towards the Koni Shocks and Comfort FCM Bumpstops as Brian has suggested.


However, perhaps I made it sound like I was in a hurry (I'm anxious, but would rather take my time for the best solution) in my original post.

If time and money were less of an issue, would waiting for the tokicos be better?

Or, are the Ohlins really the dream, both comfort and performance? I feel like there must be a way to have both and are related from a certain point of view.

It terms of expense, it may be the same either way. Changing shocks and bumpstops no big deal, but wheels with new tires too (perhaps going to the right full coilover would cure everything? or not?)

Will the resistance to compression of the Koni shocks help with the dive and squat?

In response to your last post regarding my word "comfort" : The car is odd. At times on smoother long and slower bumps, she feels like a boat (slow nauseating, pogo like motion). Other times a slam. On small bumps, the rear wheels seem to be more upset, both in slamming me, but also with regaining traction (feels like skipping). I can actually feel the rear tires skip if I'm closely paying attention to the motion, particularly when accelerating.

I'm sure I have no idea what I'm talking about, but after watching a few FCM videos on shocks, it feels like my car has little resistance to compression but too much on rebound (the jacking down thing).

P.S. I will head for an alignment, (note that on smooth to ok roads the car tracks very well, only on broken pavement or deep tire ruts will she be pull off line).

I appreciate your help. It is truly appreciated.
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Re: NC1: search for comfort on bad roads

Postby skeeler » Tue Feb 04, 2014 1:49 pm

At times on smoother long and slower bumps, she feels like a boat (slow nauseating, pogo like motion). Other times a slam.


This makes me think your dampers are blown. But I'm no expert.
2009, STR & DD. 1995, HPDE. 2004 MSM, sold. 2010 Mazda3, hers.
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Re: NC1: search for comfort on bad roads

Postby matthew-m » Wed Feb 05, 2014 9:52 pm

I am also interested in any responses. I am experiencing the same symptoms. The symptoms were increased after installing new coil-overs. When I purchased them, I was hoping it would resolve the issue from the worn stock suspension.
Matthew Metoyer
2007 Silver MX-5 PRHT, 6-speed Manual, Sport Package, Roadstersport Street Single w/Baffle, FCM Coilovers - "GT" setup with KBO & Ripple Reducer, Kosei K4R 16x6.5 wheels, Goodwin Underbody Braces
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Re: NC1: search for comfort on bad roads

Postby AndrewP061 » Wed Feb 05, 2014 11:25 pm

Really? FCM comfort coilovers? He's supposed to be the guru.

Can you give more details on your symptoms?

Where do you live? Patterns? Specific speeds? Top down differences?

I wonder if the PRHT has something to do with it. I heard rear spring rates are different.

What are your current spring rates? Tires?

I'm about to try the Konis and comfort bumpstops. Interested in your detailed experiences.
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Re: NC1: search for comfort on bad roads

Postby skeeler » Thu Feb 06, 2014 8:00 pm

The PRHT adds 77 lb, mostly to rear axle, so the rear spring rates will have to be different to achieve the same ride.
2009, STR & DD. 1995, HPDE. 2004 MSM, sold. 2010 Mazda3, hers.
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Re: NC1: search for comfort on bad roads

Postby matthew-m » Fri Feb 07, 2014 6:55 am

I have FCM coil-overs with 300 lb/in front and 224 lb/in rear springs. According to Shaikh, the front damping is at 0.58, 0.65 and 0.41 at 2/5/10. Rear is 0.48, 0.44 0.31. Tires are (very used) Michelin Pilot Super Sport 215/45/17 on Enkei 17x8 wheels.

I live in Santa Barbara County, California. If you've been here recently, you know the county has not been maintaining the roads - potholes, settling at bridge joints, etc. There are some great roads here, though I can't enjoy them because the car isn't comfortable. I don't autocross or race, so the setup was designed to increase handling while maintaining comfort. Ride height is as high as the coil-overs will allow, roughly 13.5".

At highway speeds (50+) the rear end feels like a pogo stick over expansion joints. Makes no difference top up or down. Concrete highways are the worst example. Particularly bad bumps on the highway launch the rear end up and my head lands against the roof. Any bumps encountered in corners (taken aggressively) will move the rear end off line. It was this way when the coil-overs were new as well.

At slow speeds, the best example I can give is drainage dips. The shape of the ditch is smaller than a tire. The front end comes out smoothly while the rear end follows the profile exactly without compressing, forcing the rear end up quickly. I notice this whether I am going 10 mph or 25 mph. I was able to go through these dips faster with the stock (sport) suspension (when new) and by the time the original shocks were due for replacement, the stock suspension was showing the same symptoms.

I also notice a tendency to over-steer at all speeds. Rain slick roads require extra careful throttle application, especially on sanded-smooth agricultural roads that I rarely had traction on in dry weather. (How many of you can do burnouts in third gear at 25 mph with a stock car?) Although aggressive off-the-line starts on 'normal' roads just causes wheel hop.

Put another way, it seems the rear end doesn't have any compliance over these fast-occurring events. Any other suggestions for me and Andrew?
Matthew Metoyer
2007 Silver MX-5 PRHT, 6-speed Manual, Sport Package, Roadstersport Street Single w/Baffle, FCM Coilovers - "GT" setup with KBO & Ripple Reducer, Kosei K4R 16x6.5 wheels, Goodwin Underbody Braces
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Re: NC1: search for comfort on bad roads

Postby AndrewP061 » Fri Feb 07, 2014 8:54 pm

Matthew,

That really sucks. Did you report the immediate problem to FCM?

You said the stock suspension was better before the shocks went bad...when did they go bad?

Did you like the stock ride? or was it just ok and that's why you went to FCM?

I just ordered the koni sports for my stock springs with the FCM bumpstops. I'll let you know in a few weeks if that seems to make things better.

I did read on one of the forums about a 70-year-old couple that drove cross-country in comfort using the progress springs with the tokicos. That's honestly what I would try if they were currently available.

This situation has been quite upsetting as I've been wanting a miata for 20 years, and this particular model, year, color, interior since it came out in 2008 and only now am I in a financial position to afford it. I was first going to buy an 06, much cheaper, and thought I'd use the savings for a few mods, but instead spent my entire limit for this one. So, to try to make it work I'll have to sink more money in. If this fails, I don't know. I love the car so much, but...
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