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MX-5 brake swap
bcal - 31/5/04 at 12:15 PM

Hi all,
My name is Brett and I’m Sydney Oz.
Some of you may know me from the yahoo board.
I’m planning a scratch built mid engined roadster using WRX running gear and I’m thinking of using an IRS from a MX-5.
Problem is I want 5 stud wheels and the MX-5 is only 4.
I’ve heard on the grapevine that series 4 or 5 RX-7 brakes and discs fit. Anyone had any experience with this swap?
Also has anyone used the MX-5’s front end?

Bob C - 31/5/04 at 04:07 PM

I thought it went the other way & RX7s were 5stud(!)
There's a fair degree of swappability in the mazda range, I believe some of the 323 rear calipers in particular can be used on a mx5. The "sport 2000" rear brakes are 11" rotors and the same caliper onan extended bracket - a kit is available for mx5s - handy if you want reasonable brake balance after upgrading the fronts (again kits available) to bigger rotors.
I'm using mx5 uprights/irs on my locost - but I've had to do a fair bit of messing around - biggest headache is rack at same level as bottom wishbone at front, you change the upright or the whole chassis front..... I changed he upright!
Cheers
Bob C

bcal - 1/6/04 at 06:29 AM

quote:
Originally posted by Bob C
I thought it went the other way & RX7s were 5stud(!)

Err.. I thort that's what I said. MX-5 4 stud and RX-7 5 stud. I believe that the RX-7 is same pattern as Ford also.
I'm not sure at what HP, weight and tire width that you should go to 5 stud but it's better to be safe than sorry IMO so I'll go with 5

quote:
There's a fair degree of swappability in the mazda range, I believe some of the 323 rear calipers in particular can be used on a mx5. The "sport 2000" rear brakes are 11" rotors and the same caliper onan extended bracket - a kit is available for mx5s - handy if you want reasonable brake balance after upgrading the fronts (again kits available) to bigger rotors.

Yes I'll have to some research before I commit to going this way. An alternative is to use the WRX rear uprights with a pivot attachment where the macstrut bolts up. Just have to fab my own control arms that all.
quote:
I'm using mx5 uprights/irs on my locost - but I've had to do a fair bit of messing around - biggest headache is rack at same level as bottom wishbone at front, you change the upright or the whole chassis front..... I changed he upright!


Do you have any pics.
I was toying with the idea of using Alfetta uprights coz they're rear steer and have plenty of drop. I believe that the discs from one of the Mazda range fits them, 929 I think.

Thanks
Brett

Bob C - 1/6/04 at 10:39 AM

Brett, take a look at
http://freespace.virgin.net/bob.carter/locost_build.htm
some fotos of work in progress on front uprights near bottom. Note I also had to reduce the mad angle mazda mount the bottom balljoints at.
The hardest part is finding suitable taper reamers to finish the job off!!
Cheers
Bob
PS I'd have said 4 studs were plenty on anything below a ton (even a ton & a bit...) - but you're the guy who's going to drive it!

bcal - 1/6/04 at 11:58 AM

quote:
Originally posted by Bob C
Brett, take a look at
http://freespace.virgin.net/bob.carter/locost_build.htm
some fotos of work in progress on front uprights near bottom. Note I also had to reduce the mad angle mazda mount the bottom balljoints at.
The hardest part is finding suitable taper reamers to finish the job off!!

Hmm... I see what you mean. Think I'll stick with the alfetta uprights. Besides they're just lying round in my shed looking for something to do. The alfa rack is a pretty good little unit too.
quote:
PS I'd have said 4 studs were plenty on anything below a ton (even a ton & a bit...) - but you're the guy who's going to drive it!

800kg, 230hp, 10inch rubber.
Might be an overkill but when pullin Gs round a bend with the foot on the go peddle the extra stud on the outside wheel may give me some much needed reassurance.
Thanx again Bob.
Much appreciated.

andkilde - 1/6/04 at 12:48 PM

quote:
Originally posted by bcal

I'm not sure at what HP, weight and tire width that you should go to 5 stud but it's better to be safe than sorry IMO so I'll go with 5


Four stud should be fine strength wise -- my Galant VR4 has four stud, weighs about 3500lbs. The Galant WRC cars kept the four stud config as well with no ill effects.

Wheel selection might be better in five stud though.

Cheers, Ted

Miller - 2/6/04 at 07:42 AM

SO your gonna delete the awd on the subaru tranny? How are you gonna get the shift linkage worked out? I was thinking of this swap awhile back and never got the linkage solved.

bcal - 2/6/04 at 08:54 AM

quote:
Originally posted by Miller
SO your gonna delete the awd on the subaru tranny? How are you gonna get the shift linkage worked out? I was thinking of this swap awhile back and never got the linkage solved.


A mate of mine has one in a replica Porsche syder and it pulls mid 12s on the 1/4 so the shift must be pretty quick. It has a twin cable system with some little ball thingy on the box. BTW I think it's a 2wd box. I can get some pics if you want.
The awd can be deleted and only cost around $100 to have it done so I guess there isn't much to it. Some scooby owners have then setup for RWD only for a bit of fish tailing fun.
Mine will be an auto tho. Yes that's right auto. Just as quick, maybe quicker and the missus can drive it.
BTW it going in a hotrod .