Switching to pre-ABS 328 rims - Ferrari Life
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post #1 of 5 Old 06-29-2004, 07:12 PM Thread Starter
Join Date: Nov 2003
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Switching to pre-ABS 328 rims

Has anyone had experience (or know the tech details) with changing from the later convex "ABS" rims on a 328 to the earlier "concave" pre-ABS ones?

I am looking at a 3.2 Mondial that has metric Michelin TRX-style rims in the "convex" style. The main problem is tyre supply, being limited to 80's technology TRX tyres (ugh!!). Second-hand 16" 328 pre-ABS rims of the "concave" style are available that will allow any brand tyres to be fitted, but the books say that Ferrari changed the suspension geometry when going from the "dished" to the "bulged" rims on the 328. Any info on this ???
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post #2 of 5 Old 06-30-2004, 09:15 AM
Join Date: May 2004
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I don't think the concave wheels will work. The convex were used to clear the different ABS caliper set up. You'd need to go to an aftermarket wheel like Speedline, HRE, etc.., to get standard set up.

What's the problem with getting tires for the Convex?
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post #3 of 5 Old 06-30-2004, 02:59 PM Thread Starter
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Thanks Charles.

The problem is that most Mondials from 86 - 88 were fitted with "metric" rims which are specifically designed for Michelin TRX tyres. These tyres use a different rim mounting whereby the tyre bead contacts the rim on an angle rather than horizontal.

Put another way, you know how a normal rim has "flat" or horizontal surfaces just inside the flanges each side for the tyre to mount on? This means that the tyre sidewall has to go into double-curvature or an "S-shape" as you move from the tread to the rim (ie it starts by bulging OUT and then needs to bulge back IN to sit on the rim).

Anyway, this makes the sidewall stiffer (=bad), and during the early 80's (?) Michelin developed the TRX system which angles the tyre mounting surfaces of the rim outwards, so that the tyre could just have a single curve or bulge & hence work better. Problem was it needed matching tyres and rims. No regular tyres will fit, and since no-one else joined Michelin with this technology (maybe they charged too much ??), it has become a dead-end. Either have to stick with 80's tech TRX tyres or ditch the rims altogether.

Some 328s would also have this problem, as metric rims are also listed for some of those models. My query is whether the concave rim will fit in place of a convex one assuming that NO ABS calipers are fitted (because all pre-ABS 3.2 Mondials use the convex rim). I know regular 16" convex rims from a 328 would fit, but would the earlier 16" concave ones?
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post #4 of 5 Old 06-30-2004, 03:35 PM
Join Date: May 2004
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I would assume they would. If memory serves me correctly Both Mondial and 328 have the same suspension set up. In that case you wouldn't have to worry about the wheel interfering with the suspension. And if it didn't have the ABS I would assume the upright and brakes would be the same as the non ABS 328 upright. So, there should be no interference problems with the calipers. Assuming the offset on the wheels is the same I'd say you'd be good to go.

I've always prefered a deeper "dish" wheel. I think they'd look great on the car.
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post #5 of 5 Old 06-30-2004, 06:22 PM Thread Starter
Join Date: Nov 2003
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I definitely agree. The later 328/3.2 wheels just don't have "the look".

I'm just concerned about a reference I read that Ferrari changed the susp geometry for the later wheels which just look like they would have a very different offset (but I haven't measured them). If so then swapping them over could stuff-up the steering & stability I'm reckoning.
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