Machining a TRX wheel???

This is an excellent question that I've been researching as well. Sorry to not have an answer. I looked at the other end of the horse by going to Pirelli who has a custom tire dept about making a good modern tire for this situation. That turned out to be a no-quote. I learned about this capability on Modern Marvels. I think they would have to be approached by a car company. 4.5mm (about .180") doesn't seem impossible. I wonder if the rim cross section could be given to a wheel company to analyze for fatigue etc? But who?

 

Removing material, especially in the rim area, will almost certainly reduce strength, and a high or even medium speed wheel failure can have disastrous (and lethal) consequences for the car's occupants and possibly others on the road. In addition to basic finite element analysis, wheel manufacturers go through a very strict protocol of testing (some of it to destruction) to ensure that new designs meet specific criteria for strength under the types of loads that wheels are subjected to. Unless you're prepared to subject a modified wheel to the same battery of tests (which would be impractical and prohibitively expensive), you'd best just buy a new set of wheels. (I spent nine years in the aftermarket wheel business, by the way.)

 

I'm with ya on that, I don't think Ferrari would lay up extra material/weight where it isn't needed.

 

Does it have to be a TRX wheel? Cant you just settle for something else rather than compromise your safety? Or cant you just buy the size tire intended for the rims? Just askin'.

 

Kind of on track...

I was also wondering if any other car wheel could be machined to fit the ferrari? Are the lug nuts/offset so far off that no other car in the universe is a fit? Not even close??? Seems the market would be huge. Or some sort of adaptor could be machined to adapt the wheels...

 

When I bought my 81 GTSi, in 2005 an incident driving home ( tire failure on another vehicle ) inspired me to replace the 24 year old tires. I was in your position and bought 14 inch Campy's and Sumi tires for less than $1000.00.

I have since replaced the wheels with 16 inch BBS and Mich's.


Stephen

 

Fellows, Michelin TRX's have a specialized and proprietary bead area design. Even if you can machine the OD down, you can't duplicate the standard bead locking area profile because it is so different from standard.

My information comes from Michelin USA Greenville, SC.

-Peter (started working on Ferraris professionally when the TRX was OEM <grin>)

 

You forget a 3rd option which is to find a Volvo aftermarket wheel fitment and purchase tires/wheels to replace the TRX. I did exactly that for my Mondial. If you can find a wheel with the right offset, then you're in business.

 

At the risk of being flamed (on goes the asbestos suit) I'm going to state the obvious so that maybe you'll wake up soon enough.

Apparently your life is worth less to you than $3,900.
So then what the hell are you doing owning a Ferrari?

Do what a lot of people do. Keep the original setup for shows and get something else that's more reasonable and works better.

Bob S.

 

There seems to be a few issues here. I can see dave's point on cost and he raised a good question. Everything is designed with a specific safety factor and for folks to just say if you do this you are dead should take a breath. The right thing here would be to do the modification to see if it can be done. Then get the data that determines the new strength parameters of the wheel. See how that comes out and then make your own judgement as to whether it is safe to use or just scrap the experiment. The cost for 390 tires and even 14" tires are out of sorts. Also the cost of replacement wheels are not reasonable if you compare them to the various aftermarket wheels. I would also assume that you would not track these but if the stress results look good then they may work. Also any normal person on this site is not driving these 30 year old cars around the local roads at triple figures. So a 390 wheel is 15.35" and I assume that a 15" wheel is actually 15". What needs to be determined is how does .17" removal affect the strength of the wheel. Does it reduce the safety factor by 10X or 100X. So if someone has a extra wheel and know of a machine shop that can do this then give it a try and report the results. Then you could put this issue to bed with data and not emotion.

 

Has anyone fitted a set of Volvo wheels to their 308/328?
I'd like to see pics.

 

It has nothing to do with emotion. You're talking about removing .17 inches of material in an area that's what, maybe .5 or .6 inches thick to begin with. How will a wheel be tested appropriately to gauge the effects of this very substantial reduction in material over time? Production wheels are tested to destruction for rim roll and cornering fatigue. What safety factor is considered to be acceptable?

I have no more to say here.

 

Take a couple of engineering courses on strength and materials. You'll understand then. There are also various non-destructive and destructive test that can be done. We are trying to establish if it is safe or unsafe based on the results of the data. I guess it would be interesting to see if the repro or Chinese wheels meet the Ferrari standard. How do we know?

 

I tried my Volvo 960 wheels on my GT4. They don't fit. The bolt pattern is right but the offset and hub diameter is different. I believe that a correct spacer could be made to make it work. Mondials have a different offset, so they might clear the brakes on a Mondi, but the hub was about 1mm different, I think the wheels' hole was too small, and I didn't want to use the lug nuts to press the wheel on with an interference fit. Do a search for Volvo wheels and you'll see some pics I posted.

Volvo might have (at least) two different off sets, one for rear wheel drive cars and one for front wheel drive cars, so theer might be a different model's wheel that could fit with minimal mods.

Volvo made a ton of diffferent OEM wheel designs. Some would look good on a 308. Some (like mine) would not.

 

I can show you a fitment on my Mondial. Works great. Offset between the Mondial and 308 are different, of course, but just throwing that out as a suggestion.
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I haven't seen a set of TRX 308 or Mondial wheels in a while.

Can anyone tell me if they are Magnesium or aluminum?

Thanks