| Author | Message | ||
| Don McCormick (Dandy_don)
Junior Member Username: Dandy_don Post Number: 89 Registered: 2-2002 |
Interesting thread. I am currently in the middle of attempting to put a set of 348 stock rims (8x17 front and 9.5x 17 rear) and low profile tires on my '79 308GTS. I am pretty sure it can be done as Wolfgang Eistert of FerrariChat.com Europe has mounted a set on his 308QV with 50mm adaptors rear and 40mm spacers in the front, check his profile if you are interested. He also lowered the car by approx 1" (25mm). He raves about the handling and the setup has been approved by the German TUV (motor vehicle inspection bureau-which makes any stateside vehicle inspection look cursory at best) so I am not worried about safety with this modification. Also locally a guy has mounted the same wheels/tires on his 328 and they look great, although I do realize that the 328 has different offsets than a 308. I currently have a bid from a manufacturer to make each adapter for $90 each if I provide the studs (yes I am planning on getting rid of the cumbersome Ferrari wheel bolt setup) and use DIN grade 10.9 14mm x 1.5 pitch studs sourced from Germany. Just have pricing on the bolts and spacers so far but have purchased the wheels and tires for what still looks to be a good deal although as I get into it the costs are mounting (so what else is new you say). My questions after reading the posts are simple: What potential for wheel bearing/axle stub shaft problems will I have as I am definitely making the track of the vehicle wider as the wheels are much wider than stock and the adaptors will bring the outboard face of the wheels to the edge of the wheel wells? (Somewhat further than stock maybee an 1") Any sort of geometry/handling problems that might be encountered? I could go with thinner adaptors up front as the wheels fit (need longer bolts) but the rears won't as the inboard edge of the wheel fouls the shock/springs if mounted directly to the existing rear hub. Anyway, would be interested in whatever advice or thoughts you might have before I get into this thing too deeply- I can always sell the 348 wheels and tires and go with the 328's that Ferrari UK sells but the 348 wheels/tires really look aggressive, more so than the 328's although they do look good on Newman's profile. And I guess I am not that hung up on originality as can be seen from my even considering mounting 348 wheels. Don | ||
| Steve Magnusson (91tr)
Intermediate Member Username: 91tr Post Number: 2065 Registered: 1-2001 |
Omar -- I doubt that you'd see a serious problem using the 7.5" 360s all the way around if you can keep the different front/rear tire sizes (and if you can get them in the right place -- more on that below), but since you're going to a larger wheel diameter (i.e., less tire sidewall height) you might not be able to go with a very wide rear tire (maybe something to check with Tirerack, etc. -- 225 probably OK, but 245 might be pushing things). One other caution is that Paul H.'s spacer calculations are based on the early 328 chassis. The photo in your profile shows the convex 328 wheels, so if you've got the later 328 chassis, the spacer calculations will be different. In fact, the rear offset on the later 328 chassis might be larger than the +32.5mm of the 360 front wheels so this would push the 7.5" 360 wheels in the outboard direction even with no spacer. Bottom line is that you should measure/know your existing 328 wheel offsets (they might actually be shown on the back of the wheels spokes -- if not you can make the same measurements as Paul and do the calculation). | ||
| Ben Cannon (Artherd)
Member Username: Artherd Post Number: 772 Registered: 6-2002 |
Zoikes!, IMO- Stay away from equal size tyres (and thus, wheels) in a Mid-engine car, peroid. Your car will feel all messed up, and the handling limits will be lowered dramatically. It could even get dangerous. Mid engine cars need a lot of comparative 'stick' in the rear to keep that big swinging engine from becoming a pendilum. A car with equal size tyre will exibit serious "tail happy" conditions, from too little rear tread to stick the polar moments. (or rather, too much front, depending on how you look at it. Either way, it's not a good balanced condition!) Best! Ben. | ||
| Omar (Auraraptor)
Member Username: Auraraptor Post Number: 927 Registered: 9-2002 |
Paul, thats very interesting. I talked to Paul S. btw, and he said that the rears will NOT fit without other modifications as well. So my question, if I mounted 360 front 18x7.5 rims all around(wiht the right spacers), would I lose preformance from my rear(going from 8 to 7.5 in the rear)? I wonder as though the stock is wider, but the 360 rim would wear far more modern rubber. Can others comment on this? | ||
| Martin - Cavallino Motors (Miami348ts)
Senior Member Username: Miami348ts Post Number: 5849 Registered: 5-2001 |
so get 20mm front and 30mm rear? | ||
| Paul Hill (348paul)
Member Username: 348paul Post Number: 381 Registered: 12-2002 |
I have just had a set of 360 rims measured for the offset Here are the results: Front 145mm from inner edge to mounting face 80mm from outer edge to mounting face Rim width = 225mm Offset = +32.5mm Rear 180mm from inner edge to mounting face 95mm from outer edge to mounting face Rim width = 275mm Offset = 42.5 So by the above information and taking into account that the 328 Non ABS has a +11mm offset, the spacers needed to put the 360 wheels back on the original offset would be 21.5mm Front 31.5mm Rear The rear spacer thickness would be debatable as the rear 360 rim is 2 inches wider than the 328 rim � This would bring the rim out towards the wheel arch 1 inch. Would need to check for interference. This is all fine on paper but what happens in the real world in is another! Any comments from anyone appreciated! Paul | ||
| Ric Rainbolt (Ricrain)
Member Username: Ricrain Post Number: 547 Registered: 2-2002 |
The bearings are not the only component that see additional stress. The stub axles in 308's/328's are prone to failure from the use of incorrect offset wheels. This info comes directly from my (former) technical contact at FNA. In the 348 challenge (and maybe the 355), I was told it was a common practice to X-ray the rear stub axles for stress cracks. Something to consider... | ||
| Steve Magnusson (91tr)
Intermediate Member Username: 91tr Post Number: 2056 Registered: 1-2001 |
Mitch -- Which F model are you referring to? On the later cars with the compact double-row ball-bearings and very large "+" wheel offsets I believe your observation is generally correct, but on the earlier cars with separate bearings (e.g., 308) I believe the situation is otherwise. | ||
| Mitch Alsup (Mitch_alsup)
Member Username: Mitch_alsup Post Number: 992 Registered: 4-2002 |
As the originator of a warning concering stresses related to spacers: I went into the manual and looked at the geometry of the axle and bearings. Result: spacers (up to 25mm) actually REDUCE the stress seen on the axle bearings. The original wheel to bearing spacings have the bearing outside the centerline of the wheel, spacers bring the wheel out to closer to the centerline of the bearings. Result, spacers reduce the bending moment on the bearings. However, you are changing the stresses on the steering linkage, and this may deaden the sensitivity a little. In the original configuration, the steering axis passes through the center of the contact patch. This means that road irregularities are not transmitted through the steering axis to the steering wheel, and that there is little preloaded force on the steering rack bushings. And the shock inkages are no longer pointing towards the center of the contact patch which may change the feel of that corner of the car (also by a little). But so few cars have such good shock geometry to begin with. Moving the wheels outward will cause braking forces to toe the wheel outward (both ends), while acceleration forces will toe the wheels inward (rear only). Whereas the original configuration has negligable toe change with braking or acceleration. All in all, I retracted my warning last week, and continue to retract the warning. Just be aware that the geometry with spacers IS different than the geometry without spacers, and that alignment with spacers should set the toe every so slightly more inward than stock. | ||
| Martin - Cavallino Motors (Miami348ts)
Senior Member Username: Miami348ts Post Number: 5828 Registered: 5-2001 |
Omar, don't be scared. Paul Sloan has it on his 308 with 360 rims. You can find his posts in the FL section. Send him a private message he will help. | ||
| Ben Cannon (Artherd)
Member Username: Artherd Post Number: 750 Registered: 6-2002 |
Omar- if you keep teh wheel centers the same, and use good quality hub-centric spacers, you should be fine. Use the "adapter" type if you go with more than 25mm of spacer. Otherwise, the kind where you use "longer wheel studs" is OK if good quality. The dangers occur when you try to "widen" the car a great deal with the spacers. Best! Ben. | ||
| Omar (Auraraptor)
Member Username: Auraraptor Post Number: 903 Registered: 9-2002 |
Anka, the goal is not to change the track, just upgrade the wheels to increase grip, while retaining the orginal geometry and of course approx. the indiviual stresses and loads. So then in your opinion, what exact offset should I use to addapt the 328's hub to a 360's wheel ? Paul, did you get my email? | ||
| Paul Hill (348paul)
Member Username: 348paul Post Number: 376 Registered: 12-2002 |
Agree with Steve & Bert You have to remember putting on spacers on the stock wheels and spacers on a non standard wheel to fit on to a different car as two individual things. Just imagine if you had a stock rim and removed �� of material off the mounting face, then used a �� spacer with � longer bolts - you have not changed the position of the wheel in respect to its centreline. There would be no difference in the steering geometry or any added bearing load either (apart from the weight of the �� longer bolts  ). With a different wheel from a different model with a larger offset, using the spacer to bring the centre line back in follows the same rules. Paul | ||
| Steve Magnusson (91tr)
Intermediate Member Username: 91tr Post Number: 2049 Registered: 1-2001 |
Omar -- Bert K. said it correctly -- regardless of the spacer/adapter thickness needed, if the TIRE centerline is in the same location as the stock TIRE centerline than the suspension loads are no different than stock (but for such a large distance you should use an adapter not a spacer). | ||
| Anka (Mechanka)
Junior Member Username: Mechanka Post Number: 61 Registered: 4-2003 |
OK that didn't make sense - I meant track width, not wheelbase. So Omar, would you be changing the track? | ||
| Anka (Mechanka)
Junior Member Username: Mechanka Post Number: 60 Registered: 4-2003 |
Bert brings up a very good point, I think the rest of us are talking about a scenario where wheel width and wheelbase is changed. By the way nice project Bert - how long did it take you? | ||
| Phil Hughes (Ferrarifixer)
Junior Member Username: Ferrarifixer Post Number: 90 Registered: 7-2003 |
If using spacers on the front, the gyroscopic forces of the steering action with a rotating wheel will be affected. This can cause or increase the effect of bump steer, shimmy, judder or exaggerated feedback, and just plain bad feel. I would never place appearance ahead of sound engineering....but that's just me....if you're trying to achieve certain things with your suspension, then it's all part of a package. | ||
| Bert Kanters (Bert308)
Junior Member Username: Bert308 Post Number: 97 Registered: 11-2002 |
If you turn a 60 mm offset wheel into a 11 mm offset wheel with a spacer, the load on the suspension is the same as with a standard 11 mm offset wheel without a spacer. You are just compensating for the fact that the spokes on the 360 rim are on the outside and with a 308/328 wheel more to the inside. | ||
| Anka (Mechanka)
Junior Member Username: Mechanka Post Number: 59 Registered: 4-2003 |
Granted Nick - neither have I. Porsches taking 4 inch spacers is a testament to the way they are engineered, but those wheel bearings are under increased loading nevertheless. It comes down to durability - if this was an Audi those poor bearings would be toast - they can barely handle the stock set-up. | ||
| Omar (Auraraptor)
Member Username: Auraraptor Post Number: 901 Registered: 9-2002 |
Anka, from what I read, I would need something more than a few mm..as its like putting a +50~+60mm offset wheel on a +11mm offset 3(0/2)8 chassis (adapted from what Steve said in an earlier post) I mean thats like 2 and a half inches! (I think) | ||
| nickm........ (Nickm)
Member Username: Nickm Post Number: 270 Registered: 8-2001 |
I've heard directly from RUF (in LA, not Germany) that a 4 inch spacer is OK, they have used them on 911's before. I've also heard that the spacers can hurt your wheel bearings, BUT have never actually heard of it happening to anyone. ?????? | ||
| Anka (Mechanka)
Junior Member Username: Mechanka Post Number: 58 Registered: 4-2003 |
Omar - didn't mean to scare you, most likely you couldn't put a large enough spacer to harm the suspension without extending your fenders. See if members with experience with spacers reply before you make your decision. | ||
| nickm........ (Nickm)
Member Username: Nickm Post Number: 269 Registered: 8-2001 |
I'm not a expert on this, but I know that literaly 1000's of spacers have been put on Porsche 911's. 2-3inch on the back & 1-2 inches on the fronts. Thousands of guys have done this when making thier cars into "turbo bodies" (slantnoses etc...) A friend of mine makes the spacers by the hundreds and I am sure has been responsible for at least a thousand cars with spacers. I've never heard one bad thing happening. Of course, Ferrari is a different car. | ||
| Omar (Auraraptor)
Member Username: Auraraptor Post Number: 900 Registered: 9-2002 |
Thanks Anka for exactly what I didn't want to hear. I guess the best bet is to retain offset in aftermarket wheels. | ||
| Anka (Mechanka)
Junior Member Username: Mechanka Post Number: 57 Registered: 4-2003 |
Omar, It does put higher stresses on the wheel bearings. The percentage increase in the wheel bearing loads is roughly the same as the percentage you move the wheel center by. If you are moving it by less than an inch, you should most likely be ok. If it were possible it would be best to increase the wheel width equally, centered around the wheel center (of course you probably cant do that). Spacers are a fairly standard practice on re-bodied 911's for example, it may only affect the durability of your wheel bearings. The added structural loading on the uprights and control arms should also be taken into consideration. Short of FEA analysis or calculations, have a look at your suspension and make a judgment call if there are any weak areas. Good luck and were a helmet from now on | ||
| Omar (Auraraptor)
Member Username: Auraraptor Post Number: 898 Registered: 9-2002 |
Negetive sideeffects of spacers... ...what are they? I want to put large spacers on a 328 (to fit 360 rims). I read a post a while back where a 355 had its front struts or somehting messup becuase the spacers put too much stress on a part of the setup causing it to fail (and a costy replacement) I dont want something like that on my 328. So are there neg. effects? Should I be concerned with them? I really want to put larger rims on my car so I can upgrade the brakes as well. |