When I was looking to buy a Miata, one of the things that concerned me was the lack of trunk (or boot) space. Because my SO's job requires her to carry a large filing box and the fact that we both love to travel, I find it necessary to remedy this situation.
After searching and reading everything on this subject in the Miata.net archive, I decided to do the Spare-tire relocation modification. I first tried it out by removing the spare tire for one of our trips. Armed only with a can of fix-a-flat, a AAA membership card, and a cellular phone, we were surprised at the amount of room in the trunk. We can now put two (2) overnight bags or one large suitcase in the trunk!
One of my concerns for the spare hanging off the trunk is that it might not fit. There were some mentioning in the archives that the late models (94+?) have slightly thicker bumpers that would not allow the spare to fit properly. I was also concern that the weight of the spare tire hanging off the trunk might bent the sheetmetal under the trunk.
I solved both of these problems by using the Kaleva (not to be confused with Velveeta (tm)) Spare Tire Bracket. The bracket mounts perfectly in the place of the rear (US) driver's side tie down hook and it mounts the spare tire at an angle which would allow it to fit under the car and still not be seen from the rear of the vehicle. The Spare Tire Bracket from Paul Turin and Robert Ullrich is very well made, and is finished in a durable black powder coated finish. I am very impressed with the quality and would recommend it to anyone who is contemplating this modification.
I first installed the Kaleva bracket with the original muffler still in place. The next step was to find a muffler that would fit in the space left after the spare was mounted to the bracket. A call to Paul revealed that they are still working on the exhaust system that would work with this bracket. Request for help to the mailing list and in the club meeting turn up nothing, so I proceeded to call and visit the local muffler shops to do the surgery.
My main concern at this point is that since the car is used for two hours a day for daily commutes, I want the exhaust sound level to be equal or lower than stock so that I will be able to hear the stereo and talk on the cellular phone.
[Skipping the horror stories about sleeping on the couch]
After determining that only a very short (<12") muffler would fit under the car, I tried out various combinations for fit and noise levels. This is the setup I have currently. It is as follows:
It changes the exhaust note to a low rumble that is even quieter than the stock setup. The entire package was done by A&B Muffler and Brake #2 in Haltom City (near Fort Worth, 817-834-2287). The owner, Doug Palmer, was very patient with the whole experimentation and I would recommend his shop for any quality exhaust work. He will make the same exhaust conversion for any Miata for ~$270. Frankly, I would recommend skipping the ANSA tip and glass-pack and just do the Isuzu Impulse muffler with a generic chrome tip for ~$150.
I must warn everyone that the generic 12" muffler will have a horrendous rumble at 2.5k - 3.5k RPM.
If you are not in the D/FW area and are looking for a quiet muffler that fits, it is the first generation Isuzu Impulse muffler (not the Geo Storm look-alike). It is a listed Midas part, so you could get it from the Midas Muffler chain, but I would not recommend paying their retail price.
Finally, I finished off the muffler with some BBQ grill paint. Now I am looking for some speaker carpet to finish off the trunk and a custom set of Butterfly Luggage from PJ.
Mounts the spare tire under the trunk to provide more storage space in the trunk.
I am sending this in to provide list members my observations on the Kaleva Under-the-trunk spare tire mounting bracket. Observations are included on how to make the exhaust system installation easier and better are also included in this message.
I purchased the bracket from Kaleva (Robert Ullrich and Paul Turin, located at UC Berkeley Space Sciences Lab,two very nice guys). The bracket is professionally made; quality construction throughout. The bracket replaces the driver-side (left-hand drive) rear tie-down bracket using the same mounting holes.
I installed the bracket and spare tire under the trunk yesterday and the amount of room in the trunk is wonderful!
Now for the downside. Installation of the spare under the trunk requires a custom exhaust system. Robert and Paul are still working the bugs out of their exhaust design (normal in any engineering development process) so I went ahead and bought the bracket and had a custom exhaust installed. I now have a 2 1/4" exhaust with mandrel-bent tubing from the turbo exhaust outlet all the way to the rear of the car. I went with a Walker Dynomax muffler but clearances are very tight for the muffler. The installation is 95% complete but I will have two additional hangers added to prevent the Walker muffler from "clunking" against the frame on large bumps. If I had gone to the shop with several feet of steel rod I could have had the modifications made on the spot.
An alternative muffler with more clearance is a FlowMaster but I was told that it is a noisier muffler. The Walker DynoMax produces a low rumbling exhaust note; noisier than the turbo muffler I was running before but lower-pitched and more pleasing to my ear. I am not using a resonator.
If you go with this excellent bracket and have the exhaust installed yourself, I recommend the following: