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I see, thanks Peter!
I still wonder if the MK1b had larger hubs (like FX16) than the Mk1a

Having said that, in my case, since I'm using a 2 pc disc with aluminum center hats, I may already have enough clearance for a slightly larger hub, or, can make up larger center hats.
I just need the diameter of those FX16 hubs
 

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Discussion Starter #23
Thanks, Peter. TommyG, the Corolla hubs were a half inch wider than the MR2 fronts, but I couldn't get an accurate measurement since it was returned. My mechanic said that there was not much meat for machining, certainly not 1/4" all the way around. Still researching.
AJ
 

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Thanks AJ, but I don't know the size of a Mk1a hub, and whether its smaller than a Mk1b, so basically its back to square 1
 

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Discussion Starter #26
My broken hub, which fit my '89 is the same, 4 -7/8" OD. The wheel centering hub is 2 -1/16" OD. I'm not sure where/what the difference in MK1a & MK1b is. For now I'm leaving the used backup hub on the car and hoping to make it through the Labor Day MARRS races at Summit Point, then I'll get back on hunting down replacements. Anyone with a supplier please come forward with the info. Advanced Auto Parts, Pep Boys, your local Mom & Pop, whatever. There's got to be someone somewhere with a bunch of these things.
Thanks. :thumbup
AJ

Toyota MR2 front hub assembly.
Toyota part number is 43502-17010
 

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it seems they're both the same...I wasn't sure if the brake differences between mk1 a and b extended to the hubs. Thanks for the info.
Oh well...just hate running out of spares
 

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Mk1 Front Hubs, Need Your Help!

I've broken two hubs when we used to run our MR2 in ITA. I believe that the hub that is affected depends on the direction of the track. In both cases we broke the passenger side hub on CCW tracks.

When converting the car to Super Production trim on slicks, I had new hubs made up by my local machinist out of 4340. The hub flange is ~ .125" thicker than stock. However this was not dictated by a strength consideration but where I wanted the rotor to be in the custom brake setup. Total shop time was ~ 6 hours for both hubs.





 

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Discussion Starter #30
Beautiful. A work of art. And look! NO ACCESS HOLES! Too bad they're illegal in IT or I'd be all over it. Steve B & I are buying/sharing a freaking parts car with 25+ year old hubs so we have a few spares. Just doesn't seem right. So, if I may ask, what did you have to pay for the pair? We might have to pursue this option (with stock thickness, of course) if I could get it approved by National. Yeah, right!
AJ
 

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What I'm not sure of is whether a billet item (machined from one piece of steel) will be as strong as the OEM (as weak as it is). The OEM piece may be forged, then machined down.

One of the MKI guys on our email thread about this says the OEM pieces may be welded some how (I assume because of the blueish hue to the inside-inner part of the flange). I feel that is from machining. There are no weld beads on this part that I can see.
 

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One of the MKI guys on our email thread about this says the OEM pieces may be welded some how (I assume because of the blueish hue to the inside-inner part of the flange). I feel that is from machining. There are no weld beads on this part that I can see.
That blue hue is ether heat treating or over heating from brakes. if they are brand new and are blueish in color they are heat treated.

now the billet one comes down to if the steel they started with is as strong as the hared factory piece.
 

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Only blueish at one point/circumferential stripe on the inner flange surface, right where the machining starts/stops. I will try to get a picture.
 

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I think one of the problems we are also dealing with is fatigue failure. Some of the parts are getting to the age where they have undergone many millions of cycles. This will be an even worse problem in the future if it is true that new pieces are no longer being sold.

I have to agree with PDoane in that a new custom piece of identical dimensions to a factory unit is not necessarily going to be stronger. I was able to make mine stronger largely because of the thicker flange - which is not an option for those with stock brakes.

BTW, the units I had made were for personal use only - I'm not trying to sell them. If you're interested, PM me and I will put you in touch directly with the machine shop that made them.
 

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AJMR2: If I thought there was enough interest I can have a machinist with CNC capability machine those out of good material(4340) and heat treated to 45 on the "C" scale. Then they won't break. Only draw back is I need 15 sets to get a decent price with a 50% deposit.
PS: Don't even think about approaching SCCA Nat'l for approval. You will not get it. Find them, make them, use them. How many times have you ever seen a tear down to check front hubs. Your safety is worth more than any rule IMHO. Otherwise, your only alternative is park the MR2, and build/race a Honda or VW. I will race my MR2 no matter what!!
 

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I'd be up for a pair or two if someone organized a production run. And I agree with racermr2... let them protest me (it's not like I ever see the podium). I'm in this for fun and wondering if every vibration I feel is the onset of a broken hub is not fun.

Besides, if we fabricate to OEM dimensions I fail to see why the lack of holes would exclude them from being considered after market replacements. Someone would have a hard time proving the lack of holes as a competitive advantage as we are actually ADDING rotational mass.
 
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