AlanV

Hey guys. I was pouring through the search engine and couldn't find anything substantial on my question, so here it is. I've been thinking about getting a set of adaptors to go from our 4x110 bolt pattern to a 4x100 bolt pattern. What are yalls opinion on them and what offset should I get to keep the centerline as close to stock as possible with them? My rx7 is an 84 gsl. Any help would be much appreciated.

j9fd3s

iTrader: (3)

well if you want to do adaptors, make sure they are hub centric, its kind of important. although the hubcentric part can be plastic.

since you need to have enough room for the fasteners, the adaptor needs to be around 20mm thick, if not 25mm (1"). since the stock wheels are ~20 offset, adding 25mm, means your new wheels should be in the 40-45 offset range, which actually should be really easy.

other than that its totally fine.

AlanV

Ok cool. Thank you so much. I saw some billit aluminum adaptors for ~$130. I really want to run enkei rpf1 to keep the light weight of the run that the stocks have

elwood

iTrader: (1)

BTW - you can buy hubcentric adapters in many sizes on Amazon. They have both plastic and aluminum.

Carl

iTrader: (2)

Try adaptitusa.com. I have a set of 25mm thick adapters. They are very good and I use them on my IT race car. With 2.5" coilovers, 15x7 wheels with 205-50-15 Hoosiers rub slightly on the spring if the offset is et40. et38 just clears, but 35 would be more comfortable. The Hoosiers also tend to be wide for 205's. When using stock 2nd gen Miata wheels that are 15x6, the 205's clear fine. With that in mind, you need to understand clearly what tires and wheels you want to run to get the offset correct (either the wheel offset or the spacer thickness.

I am not sure how the wheels will fit with the stock springs. I think the wide part of the stock springs sits fairly high so may still clear the wide wheels/tires. I know that our chumpcar uses stock size springs with 15x7 wheels and 205-50-15 street tires. Just not sure what combos will work correctly. et20 konig rewinds rub and need about 1/4" spacer. If you forget the spacer it will only take a couple miles at speed to machine a groove all the way through the tire. Guess how I know?

Hope you can use some of this information to figure out what you want.

One thing that the adaptitusa adapters do that I like a lot is that the lugnuts that attach the adapter to the hub have an extended shaft that fits tightly into the machined hole. This provides a very secure connection of the adapter to the hub. All other adapters (admittedly a small sample size) do not have that feature.

Carl

gracer7-rx7

iTrader: (16)

Good stuff Carl.

What do offset do you suggest for a 15x7 running something like the Toyo RR? The 38?

Did you try mounting a Miata 15x7 +25 or +30?

Thanks.

Carl

iTrader: (2)

I have not tried mounting a +25 or +30, because I don't have any. My spec Miata came with +40 and in favor of not spending money to get all new wheels, I have am using those with some +38's blended in. I use the same wheels and tires now on both the ITA RX7 and Spec Miata.

I have attached a picture of 15x7, ET38 wheels with Hoosiers. The gap at the fender is OK, but it could not get much smaller. These fenders are rolled. I am sure they would rub not rolled. There is also a picture of Hoosier and RR on 15x7 rims. The Hoosier is definitely wider. Maybe not quite 1/2". That means the RR would stick out about 1/4" less, which is 6mm. Thus the RR on ET32 would be about the same as in this picture. A +30 would be a little too close for comfort for me anyway. If you need accurate info, I could check later using spacers. I was just going to do it, but I tripped on a trailer hitch lying in the driveway and may have broken a toe, so not in such a good working mood right now. I will probably try it in a couple of days for my own information.

As a clarification to my post, the Rewinds are used without a spacer. I was just using that example to explain that a properly located 15x7 would fit without the rubbing on the spring. ET+15 on the Rewind (but the don't come in that backspace) would prevent rubbing on the inside and pretty much fill the fender well on the outside.

Also the 15x6 Miata wheels are ET40. They are light (13lb each) and cheap. I have bought sets of 4 for as little as $75.

The adapters real open up what you can do for wheels and tires.

Carl

mustanghammer

iTrader: (3)

Good information.


I am having a set of adapters made for the front of my STU RX7 that will adapt from 4x114.3 to 4x100. On the rear, I had the axles drilled to 4x100 because I want as much positive off set as I can get. My car uses 15x8 wheels.


I should have built my car like this to start with. 4x100 wheels will save me 4lbs a corner and are so easy to get.

Carl

iTrader: (2)

OK. I went out and did some fitting with 205-50-15 Toyo RR's and Hoosier SM7's. The wheels are 15x7 and the adapter is 25mm thick on the stock big bearing hub. I have 2.5" coilovers installed. Fenders are tightly rolled (taken off the car and flattened with a rubber mallet.

With the Toyo RR's on the front,

+40 gives about 1" fender clearance, but rubs on spring (depending on location of adjuster)
+34 gives a fingers width fender clearance and clears the spring
+28 probably does not rub on fender and of course clears the spring

With Hoosier SM7 on the front,

+28 is closer than Toyo at fender, but still might be OK.
+34 is good clearance at fender and spring
+40 definitely hits spring

With Hoosier SM7 on the rear,
+ 28 is very close and will probably rub
+34 is as close as I would be comfortable with and it might hit every once in a while.
No clearance problems on the inside with any offset.

I hope this helps. Basically there is not a lot of flexibility for 205-50-15 race rubber in the RX7 wheel wells.

Carl

mustanghammer

iTrader: (3)

Carl,
What size springs are you running on the front? I switched to 6" tall 2.5 coil overs on the front and picked up some tire clearance.

Carl

iTrader: (2)

I am running 7" x 2.5". For me 6" would make it worse, because the problem is the adjusting collar hitting the wheel, not the spring. 8" would actually be better in my case, at least.

I think the main issue is the wheel well is small and to fit a racing 205 or even 225 x 15 you need to get the offset just right. It works fine, just not alot of flexibility on offset.

I have enjoyed watching your STL build Scott. Lots of cool stuff.

Carl

placd1

iTrader: (3)

On an unrelated note, curious to know if the Miata suspension can work on an FB. Enquiring minds want to know

mustanghammer

iTrader: (3)

Thanks!


My current setup in front is a 4x114.3 15x8" wheel with a net 0 offset (+15mm wheel with a 15mm spacer) with a 205 50 15 Kumho V710 tire. A 205 50 15 Hoosier/225 45 15 Hankook/Toyo RR will fit up front but that is the max. I am running -3 degrees of camber which helps too. I am running the same wheel/Kumho tire on the rear and the +15mm off set is not enough.

My 4x100 setup will use 15x8 +35mm front and back with a 25mm lug adapter up front and no adapter in the rear because I changed the pattern on the axle. Hopefully this will allow me to drop the rear ride height around an inch over what I have now.