NC1: search for comfort on bad roads

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matthew-m
Posts: 82
Joined: Tue Jun 09, 2009 7:23 pm
Location: Santa Maria, CA

Re: NC1: search for comfort on bad roads

Post by matthew-m »

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
2010 Grey MX-5 GT, Manual, Sport Package, Street Single w/Baffle, FCM Coilovers - "GT" setup with KBO & Ripple Reducer, 16x8 wheels, Budget Big Brakes, Goodwin Underbody Braces, Cravenspeed Shift Knob
AndrewP061
Posts: 7
Joined: Sun Feb 02, 2014 12:07 pm

Re: NC1: search for comfort on bad roads

Post by AndrewP061 »

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.
skeeler
Posts: 282
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Location: Ann Arbor, Michigan
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Re: NC1: search for comfort on bad roads

Post by skeeler »

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.
matthew-m
Posts: 82
Joined: Tue Jun 09, 2009 7:23 pm
Location: Santa Maria, CA

Re: NC1: search for comfort on bad roads

Post by matthew-m »

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
2010 Grey MX-5 GT, Manual, Sport Package, Street Single w/Baffle, FCM Coilovers - "GT" setup with KBO & Ripple Reducer, 16x8 wheels, Budget Big Brakes, Goodwin Underbody Braces, Cravenspeed Shift Knob
AndrewP061
Posts: 7
Joined: Sun Feb 02, 2014 12:07 pm

Re: NC1: search for comfort on bad roads

Post by AndrewP061 »

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...
matthew-m
Posts: 82
Joined: Tue Jun 09, 2009 7:23 pm
Location: Santa Maria, CA

Re: NC1: search for comfort on bad roads

Post by matthew-m »

Andrew,

Yes, FCM helped fix some problems, but their only suggestion for fixing this particular problem was change either the front or rear springs to improve the "frequency". I still don't understand it, but as soon as I have some extra cash I may try 2 new springs... The problem is when will I have an extra $600 for springs and installation cost! It has only been 2 1/2 years...

I bought the car new at the end of 2006 and didn't replace the springs/shocks until June 2011. I don't remember when I decided the shocks were 'bad'; at the time of the coil-over install the car had 54000 miles.

The stock ride was merely OK, and I asked FCM to improve: comfort on California's broken freeways/rural roads; less dive/squat; less bottoming out on dips/bumps; and less body roll. There is less of everything on my list... I suspect new shocks and sway bars would have been a better place to start.

I have ridden in other modified Miatas and I know its possible to have the rear not beating me up on every bump. I just don't know how to fix it easily.

Sorry I hi-jacked your thread. You described the same symptoms I have been experiencing for the last 3+ years and I was hoping the forum had some (easy) suggestions. I look forward to your comments on the new parts.
Matthew Metoyer
2010 Grey MX-5 GT, Manual, Sport Package, Street Single w/Baffle, FCM Coilovers - "GT" setup with KBO & Ripple Reducer, 16x8 wheels, Budget Big Brakes, Goodwin Underbody Braces, Cravenspeed Shift Knob
skeeler
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Location: Ann Arbor, Michigan
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Re: NC1: search for comfort on bad roads

Post by skeeler »

matthew-m wrote: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 see that you have bounce frequencies of 1.79 and 1.72 Hz, a F/R ratio of 0.96. Many people, including Shaikh at Fat Cat would tell you that for best comfort, you want a "flat ride" setup with the rear a little higher than the front. That should help a bit. You can go to 250/224 springs for a ratio of 1.07 or 300/280 for a ratio of 1.07. That way, you only have to change one pair of springs.

You can get good springs for 50-75 dollars each, and installation isn't that bad if you have a jack, stands, a torque wrench, and a socket sets. Are you running the Tein 90- to 70-mm tapered spring in the rear? Those are starting to get hard to come by.

Before you start changing springs, let's consider your current setup. What sway bars are you running? Also, have you had the car aligned? What specs?

Given your power oversteer, I wonder if your "very used" tires also very old so that they aren't providing good grip. Can you borrow someone's wheels with new tires for a test drive?
2009, STR & DD. 1995, HPDE. 2004 MSM, sold. 2010 Mazda3, hers.
matthew-m
Posts: 82
Joined: Tue Jun 09, 2009 7:23 pm
Location: Santa Maria, CA

Re: NC1: search for comfort on bad roads

Post by matthew-m »

Power over-steer occurs whether the tires are new or old, hot or cold. I've tried extreme summer tires and had over-steer. I've had 2 sets of tires since adding the coil-overs and all have exhibited over-steer.

I do not have the desire to change springs myself. I was under the impression I have Eibach springs, but I have no idea. I only planned to change one set of springs, though I never decided whether to go down on the front rate or up on the rear.

Sway bars are stock and the car was aligned and corner balanced. Specs are 1.5 neg all around and toe is 1/16" in front, 3/32" in rear, or they were 2 years and 25,000 miles ago.
Matthew Metoyer
2010 Grey MX-5 GT, Manual, Sport Package, Street Single w/Baffle, FCM Coilovers - "GT" setup with KBO & Ripple Reducer, 16x8 wheels, Budget Big Brakes, Goodwin Underbody Braces, Cravenspeed Shift Knob
jboemler
Posts: 304
Joined: Fri Oct 10, 2008 6:15 pm
Location: Mukilteo WA

Re: NC1: search for comfort on bad roads

Post by jboemler »

Before you go replacing things, you might try adding a half-degree of camber in the rear...
monty11ez
Posts: 17
Joined: Sat Aug 18, 2012 9:59 am

Re: NC1: search for comfort on bad roads

Post by monty11ez »

Adding more camber isn't going to fix the frequency. Skeeler's suggestion is right on point. You will either need more spring in front or less in the rear. Also I hear you can use the 100-70mm tapered springs as well. Brian also sells adapters for regular springs.
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