I installed the FM Butterfly Brace on my 90 Miata last night. Holy smokes! What a difference! I can't believe how much stiffer the car is now.
It wasn't the easiest job I've ever done, but it wasn't too bad. The only issue to sort out is that the exhaust seems to resonate much more now. I don't believe it's touching the brace anywhere, but I must be wrong because I'm sure I can hear it.
Rob
Did you already have the frame rails, or did you just install both?
The installation effort for just the butterfly (on a car that already has the frame rails) is about the same as doing the frame rails and butterfly at the same time.
If you're hearing more exhaust resonance, I suspect you have interference somewhere. I've found that I sometimes have to put a hose clamp around the exhaust hanger just behind the butterfly to compensate for, umm, "well-experienced" rubber hangers and keep the exhaust from drooping too far.
Keith, how much of a difference is there between just the frame rails and the frame rails and butterfly? How do the frame rails attach to the chassis? I know your web site says there are 16(?) holes to be drilled. Do those holes get tapped or are they clearance?
I'll let one of our customers review that for you (from our testimonials page):
As far as the rails vs. the brace: I can definitely say the brace made the bigger difference of the two. With only the rails, the cowl shake wasn't really reduced, but the car did seem to communicate more to the driver, espically with what the rear end was doing. Adding the brace to the rails really seemed to tighten everything up overall. I haven't had a chance to really thrash on the car with the brace in, but it does make a more noticable difference simply driving around when compared to just the rails. I had thought about only doing the rails in a bid to save some cash. After experiencing things both ways, I'd definatly say both pieces are the way to go and I'm glad I went that direction.
The frame rails are bolted to the chassis with 16 bolts. I'll bet you just figured out what the holes are for :) They're not tapped - the chassis is made of sheet steel, there's not much there to tap - so you have to remove the carpet and seats to deal with the nuts. Frame rail instructions (PDF)
What kind of facilities do you need for the install? Is this something that can be done by a schmoe in a garage with jack stands? Or does it require a lift?
I did it in the garage on four jack stands. It wasn't too bad. However, I am having a friend put my car on a hoist tonight to see where it may be making contact with the exhaust, because I don't have the energy to go back under the car tonight. There were no real issues with working under the car -- nothing is too heavy or cumbersome.
How much does the brace weigh?
I re-adjusted the centre section, and now only have the occasional moment when the exhaust rubs on the brace. I need to take a good look at all the hangers and make sure there's not too much movement in the system. Sadly, I'm running an HPDE all day today, so I'll have to suck up the occasional vibration :)
The most amazing difference is the manner in which I can feel the suspension working. I run AGX shocks, and the older FM spings -- and there is a noticeable, positive difference. Well done, FM!
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