What is the practical limit to Miata hubs?

So as I sort the Zoomboni I have questions.  It uses NA Miata suspension and hubs.  Which means it has 4x100 hubs and bearings designed for a street car wearing 185/14 tires.  But it’s an E mod build so the builders chose a set of Mustang wheels for it so it has bolt on  adapters to take the hubs from 4x100 to 5x114.  The front wheels are 295 Hoosiers on a 17x9” wheel and the rears are a ridiculous 315 on a 17x10.5”.

Weight is pretty minimal for the vehicle (well under 2,000 lbs) but these wheels are HEAVY.   What’s the smart setup here?  Is it worth keeping the massive rubber or would I be just as fast on lightweight TRM 17x9 wheels and 245 A7s?  Am I at risk for breaking the hub right off the car?    Should I shop around for 15xwides and get lighter by staying 4x100?

To compound my conundrum one of you math people can tell me..... these tires are 25” tall and the car is a 302 with a WC T-5 and a torsen 4.3 diff.  What realistic 2nd gear speed does that equal?

Thanks y’all!  

It's more a matter of "how long do you want them to last"?

What's the 2nd gear ratio on that T5? What's your redline?

Keith Tanner said:

It's more a matter of "how long do you want them to last"?

This. Enormous load for a short period of time, or a little load forever. I wouldn't think it would see enough miles for the hubs to be a problem. 

Miata hubs have been known to fail in SM with 15x8 wheels and 205 tires.  It ain’t pretty when it happens.

One issue is that the many of the parts store replacement front hubs had a sharp step machined into them, which would initiate a fatigue crack when racing.  Centric recognized this issue, and now offers two versions- standard and “premium”, without the machined step.  Get the premium.

For rear hubs, there is a guy that modifying the more sturdy MR-S rear hubs to fit the Miata.  Check out SadFab.

And it looks like the HP peak way back when came on at 4,600 rpm but the engine doesn’t really redline till 6,000.

Weight for all 4 Mustang wheels:  204 lbs

Weight for the TRMs:  168 lbs

One thing to consider is the bending load on the hub is 8-15% greater just from tire diameter alone vs. a miata sized tire (22.5-23").

And that 25" setup will only carry you to 53.5mph in 2nd.  The 23" is good for 49.2 

3rd with the 23" is good for 71mph.

Lots of discussion on miataturbo.net over the last year or so on hubs...  it seems the typical aftermarket hubs have decreased in quality over the last few years, and folks are having failures even with name brand parts.  OEM still seems the best of, well, OEM type stuff.

<200TW tires and >225 width seems to shorten life significantly.  Even with the light weight, you're probably going to experience pretty short hub life.

Sadfab has a converted MR-S hubs for the rear.  I have a set, but haven't got 'round to installing them yet.  Sadfab

There's this E30 conversion for the front:  E30 front conversion hubs

There's the Wilwood front hub, though I have yet to see much feedback, either way with these:   Wilwood front hubs

And the gold standard:  Miatahubs front hubs

In reply to KyAllroad (Jeremy) :

Those are the ratios for a t5-z. Yours probably has a 3.35 first but second should be pretty close to that. 

Pretty sure there were 4 cylinder WCs too, those had a much different 2nd gear.

Your 2nd gear will reach the limiter at ~55mph

The following site is a great reference for all of the various t5 versions.

T-5 guide - britishv8.org

I put wilwood hubs on our V6 car. Super cool design that's way stronger because it moves the outer bearing further outward. Clever engineering there. 

Rodan said:

Lots of discussion on miataturbo.net over the last year or so on hubs...  it seems the typical aftermarket hubs have decreased in quality over the last few years, and folks are having failures even with name brand parts.  OEM still seems the best of, well, OEM type stuff.

<200TW tires and >225 width seems to shorten life significantly.  Even with the light weight, you're probably going to experience pretty short hub life.

Sadfab has a converted MR-S hubs for the rear.  I have a set, but haven't got 'round to installing them yet.  Sadfab

There's this E30 conversion for the front:  E30 front conversion hubs

There's the Wilwood front hub, though I have yet to see much feedback, either way with these:   Wilwood front hubs

And the gold standard:  Miatahubs front hubs

 

Just quoting this so I can find it later when I need to - I hadn't heard about the wilwood hubs. That looks like a nice compromise between the stock and super-baller Miatahubs options

The Wilwood hubs are a “trailer style” design - their longevity is going to be directly related to accurate and frequent adjustment. FYI. 

In reply to Tom Suddard :

They also fit BG chassis cars :) 

KyAllroad (Jeremy) said:

So as I sort the Zoomboni I have questions.  It uses NA Miata suspension and hubs.  Which means it has 4x100 hubs and bearings designed for a street car wearing 185/14 tires.  But it’s an E mod build so the builders chose a set of Mustang wheels for it so it has bolt on  adapters to take the hubs from 4x100 to 5x114.  The front wheels are 295 Hoosiers on a 17x9” wheel and the rears are a ridiculous 315 on a 17x10.5”.

Weight is pretty minimal for the vehicle (well under 2,000 lbs) but these wheels are HEAVY.   What’s the smart setup here?  Is it worth keeping the massive rubber or would I be just as fast on lightweight TRM 17x9 wheels and 245 A7s?  Am I at risk for breaking the hub right off the car?    Should I shop around for 15xwides and get lighter by staying 4x100?

To compound my conundrum one of you math people can tell me..... these tires are 25” tall and the car is a 302 with a WC T-5 and a torsen 4.3 diff.  What realistic 2nd gear speed does that equal?

Thanks y’all!  

I can't imagine the lighter 245 setup being faster unless you just simply can't get the wider tires up to temp.

Well, I've been inspired to order the Sadfab rear hubs.

I'd like to hear more on the Wilwood hubs (including where the heck do you buy them??).  There website is having some kind of cert breakdown.

Those Miatahub hubs look pretty nice though....

I'm still working on my eternal quest to bulletproof my Exocet.

z31maniac said:

KyAllroad (Jeremy) said:

So as I sort the Zoomboni I have questions.  It uses NA Miata suspension and hubs.  Which means it has 4x100 hubs and bearings designed for a street car wearing 185/14 tires.  But it’s an E mod build so the builders chose a set of Mustang wheels for it so it has bolt on  adapters to take the hubs from 4x100 to 5x114.  The front wheels are 295 Hoosiers on a 17x9” wheel and the rears are a ridiculous 315 on a 17x10.5”.

Weight is pretty minimal for the vehicle (well under 2,000 lbs) but these wheels are HEAVY.   What’s the smart setup here?  Is it worth keeping the massive rubber or would I be just as fast on lightweight TRM 17x9 wheels and 245 A7s?  Am I at risk for breaking the hub right off the car?    Should I shop around for 15xwides and get lighter by staying 4x100?

To compound my conundrum one of you math people can tell me..... these tires are 25” tall and the car is a 302 with a WC T-5 and a torsen 4.3 diff.  What realistic 2nd gear speed does that equal?

Thanks y’all!  

I can't imagine the lighter 245 setup being faster unless you just simply can't get the wider tires up to temp.

Is there a reason for the 245 limitation?  If you can run 315s on the rear already, why not run the 295/35 on 15x12 combo?  Or at least 275/35?

In reply to accordionfolder :

I may try to see if these will work on my Exocet later. https://www.palatov.com/shop/suspension/pm-modular-uprights-gtx/

In reply to accordionfolder :

Here's the Wilwood pieces:

https://www.wilwood.com/BrakeKits/BrakeKitListFront?mincatdesc=Front%20Hub%20Kit%20(Race)

Looks like you have to call to order. 

In reply to ProDarwin :

No real reason.  I have the 245s on 17x9 wheels already.  Given that the 245 setup is 45 lbs of rotating weight lighter than the 295/315 setup I have a feeling it will feel more lively with them.   Remember this is only 1800 lbs of car so pretty minimal weight.

Keith Tanner said:

The Wilwood hubs are a “trailer style” design - their longevity is going to be directly related to accurate and frequent adjustment. FYI. 

Thanks, Keith... that was the bit I'd heard about the Wilwoods, but couldn't remember last night.

Here's a relevant thread with my findings about Miata hubs from a while back: https://forum.miata.net/vb/showthread.php?t=582020

Specifically, it has photos of the step that ShinnyGroove mentioned earlier in the thread. I don't have any direct experience since that thread. YMMV

So to get a bit more clarity - are the fronts just prone to toasting bearings? Or do they also explode like the rears? (I'm prioritizing my purchases)

I'm only seeing the rears giving up and letting your wheel go it's separate way. 

The fronts are the one that eat bearings. The rears have drive flange separation problems when timed out or when replaced with bad aftermarket parts.

After I lost my rear wheel in turn 9 at Laguna Seca (poorly designed aftermarket part), we approached Mazda Motorsports with a proposal for stronger rear hubs. "That's not needed," they said. "Nobody breaks rear hubs". Then they put stock replacements as a high visibility product on their website because there were three high-profile failures in a week.