MOORE996

I had a similar problem. Mine turned out to be a bent rim.

philooo

I wonder if you took a picture of the rim?

I mean could you see the bent on the rim when you look at it ? I wonder if you can always see it form the inside of the rim, or if you have remove the tire to see it.

bkjwhipple

If you had a bent rim it wouldn't come and go.

fpb111

This was my "seat of the pants" rear vibration that turned into a slow leak. I finally took the tire off to dunk it in water to see if I coud find the leak. I found this;

Near the crack it had about 1/2" of run-out. There was no other damage on the rim or tire?? I think the run-out happened when the crack relieved some stress.

philooo

Ok after a week of silence and puzzling driving, I have to report that all week the car has been driving without steering shaking!

I did not do anything new to the car, and as you recall, after my alignment, the steering was still shaking above 60mph.

After reading that tire inflation might play a role, I decided to deflate my tires 1psi at a time and to some test run. Even though the shake was still there above 60 mph, even at super low pressure, once back in the garage I had to re-inflate the tire with my little $20 compressor, and after that... I had to go to Mexico for a wedding... but that is another story

Anyways, since I am back, the car drive just fine !

So far, I think some water/moisture might have been in the tire and when I deflated my tire to almost flat it went out, and my little cheapy compressor seems to have done a good job inflating without H2O.

Unfortunately, no scientific explanation on this one. I did not see it with my own eyes but I think that was it.

I will keep you up to date if it comes back. I am really frustrated that it disappeared just like this, without anything major done.

The guy who did my alignment did tell me that I had a serious toe alignment problem and one of my front tire was worn improperly and that the new alignment would help worn down both my tire evenly over time. So that might be another explanation, even though it seems flimsy.

Barn996

That's good news, did you end up replacing all 4 tires in the process?

philooo

Nope everything is the same, same tires, same wheels.

Only change was the alignment and then the air....

Puzzles me !

Barn996

Wow. well at least your rough ride is history.

oze172

Hi there

Well, the scrapping noise in your video is probably the inner brake disc cover touching the disc. You can poke a screw driver between the spokes and gently push it off the disc again to prove the point. Had this a couple of times after some hot running on circuit.

As mentioned by others, your wheels look great but are definitely not OEM and you've got way too many weights in there to think all is well. Aftermarket alloy wheels can be of very variable quality, usually much heavier (hence more balancing weight required) and regularly don't have a good hubcentric fit. Don't be surprised if every time you refit the wheels you have a slightly different mounting point and therefore variable levels of imbalance. Being aftermarket could also explain why the tyres are spinning badly on the rims.
The fact you can go through periods of no wobble says the suspension is probably fine so the problem is most likely all in the unsprung weight of the wheels and tyres.
If the problem comes back (IMHO it will, sorry) I'd highly recommend checking the wheels have no warping, run straight and that they sit snugly on the hub (no side to side movement whatsoever). Also make sure the bolts are torqued to 130Nm (96lbft I think). The ultimate test would be to fit a set of OEM wheels (18" not 19") with the correct pressures and OEM tyre sizes.
BTW 19" rims do create a harsher ride and require lower than OEM pressures to avoid the front bouncing because of the lower profile sidewalls.

Interested to know how you get on, been through this kind of stuff a couple of times myself and always frustrating!

philooo

Right now the situation seems stable. I'll keep the thread alive if something arise.

I feel a very slight shake but I think I am getting picky. again I can feel a very different feel when the road id bad or when the steering start to wobble.

#oze172, are there any non oem you think are as good as oem ? FIKSE ? CHAMPION I know it is like another whole thread but my be you have some experience on that. I want to get some oem wheels but their quality seems questionable as I have seen bunch of them cracked and stuff.

wlee69

Philooo - Check out this link - post #9

https://rennlist.com/forums/996-foru...i-florida.html

These are the wheels you have. They aren't OEM - and if you are thinking of going OEM, I think you'd be better off than with what you have from a weight perspective alone. Those "Modular" wheels were popular 2-3 years ago as they were dirt cheap and were one piece wheels that looked like three piece (the bolts along the edge are for show). Wheels looked good, but I think they were pretty heavy.....

BTW - if you have the tires balanced on a Hunter machine, it checks for the rim being out of round at the same time - so if the tire place knows anything of what they are doing, the Hunter machine checks for both the tire and wheel being out of round along with balancing.

oze172

Hey,
I know a fair bit on the subject but don't consider myself to be an out and out expert because I'll never change from my OEM Sport Classic II split rim alloys, see attached, even though they're a pain to keep clean!

My experience of "replica" wheels is via a few friends and some have regretted it; citing a change in handling (weight), continual wheel balancing problems (manufacturing inconsistencies) and having to retorque wheel bolts regularly for whatever reason.

After market wheels (own brand and design) are typically more expensive and employ better manufacturing methods. BBS, OZ etc. You get what you pay for.

I personally put a lot of faith (and money!) in tyres, brakes and geometry to consistently get the most from my car at all speeds as safely as possible. The quickest way to undermine all of that is to put on some wheels that aren't capable of performing as expected.

Just to be clear, yours "could" be ok, but they're a question mark without the evidence to back it up for peace of mind. If you do find the wheels need changing I'd recommend going back to 18" OEM of your choice for a better driving experience.

Excert from Tirerack on manufacturing techniques:
http://www.tirerack.com/wheels/tech/....jsp?techid=90

One-Piece Cast Wheels
This is the most common type of aluminum wheel. The casting of wheels is the process of getting molten aluminum inside a mold to form a wheel. There are different ways this can be accomplished and although it sounds simple, this is truly an art when done properly.

GRAVITY CASTING
Gravity casting is the most basic process of pouring molten aluminum into a mold utilizing the earth's gravity to fill the mold. Gravity casting offers a very reasonable production cost and is a good method for casting designs that are more visually oriented or when reducing weight is not a primary concern. Since the process relies on gravity to fill the mold, the aluminum is not as densely packed in the mold as some other casting processes. Often gravity cast wheels will have a higher weight to achieve the required strength.

LOW PRESSURE CASTING
Low pressure casting uses positive pressure to move the molten aluminum into the mold quicker and achieve a finished product that has improved mechanical properties (more dense) over a gravity cast wheel. Low-pressure casting has a slightly higher production cost over gravity casting. Low pressure is the most common process approved for aluminum wheels sold to the O.E.M. market. Low-pressure cast wheels offer a good value for the aftermarket as well. Some companies offer wheels that are produced under a higher pressure in special casting equipment to create a wheel that is lighter and stronger than a wheel produced in low pressure. Once again in the quest for lighter weight, there is a higher cost associated with the process.

Spun-Rim, Flow-Forming or Rim Rolling Technology
This specialized process begins with a low pressure type of casting and uses a special machine that spins the initial casting, heats the outer portion of the casting and then uses steel rollers pressed against the rim area to pull the rim to its final width and shape. The combination of the heat, pressure and spinning create a rim area with the strength similar to a forged wheel without the high cost of the forging. Some of the special wheels produced for the O.E.M. high performance or limited production vehicles utilize this type of technology resulting in a light and strong wheel at a reasonable cost. BBS has used this technology for several years in their production of racing wheels for Formula One and Indy cars. BBS's RC wheel for the aftermarket is an example of a wheel produced using spun rim technology.
CNC Mill

In forged wheels, computer numerically controlled
(CNC) mills add the cosmetics and the bolt circle to exacting tolerances.

Forged
The ultimate in one-piece wheels. Forging is the process of forcing a solid billet of aluminum between the forging dies under an extreme amount of pressure. This creates a finished product that is very dense, very strong and therefore can be very light. The costs of tooling, development, equipment, etc., make this type of wheel very exclusive and usually demand a high price in the aftermarket.

Multi-Piece Wheels
This type of wheel utilizes two or three components assembled together to produce a finished wheel. Multi-piece wheels can use many different methods of manufacturing. Centers can be cast in various methods or forged. The rim sections for 3-piece wheels are normally spun from disks of aluminum. Generally, spun rim sections offer the ability to custom-tailor wheels for special applications that would not be available otherwise. The rim sections are bolted to the center and normally a sealant is applied in or on the assembly area to seal the wheel. This type of 3-piece construction was originally developed for racing in the early 1970s and has been used on cars ever since. The 3-piece wheels are most popular in the 17" and larger diameters.

There are now many options for 2-piece wheels in the market. The 2-piece wheel design does not offer as wide a range of application that a 3-piece wheel allows, however they are more common in the market and the prices start well below the average 3-piece wheel. Some 2-piece wheels have the center bolted into a cast or cast/spun rim section and other manufacturers press centers into spun rim sections and weld the unit together. When BBS developed a new 2-piece wheel to replace the previous 3-piece street wheel, they used the special rim-rolling technology (originally developed for racing wheels) to give the rim section the weight and strength advantages similar to a forged rim. On the high-end of the 2-piece wheel market you can find wheels using forged rims and forged centers. Since these are only sold in small volume and due to the high development and production costs associated with the forging process, they tend to be on the high end of the price scale.

Good luck, I hope it all works out!

oze172

I wrote a post earlier but got distracted and lost it!

Take a look at this article on different manufacturing methods http://www.tirerack.com/wheels/tech/....jsp?techid=90

There are 2 sorts of non OEM wheels; Replica and aftermarket.
Replicas typically adopt low cost manufacture methods that mean they weigh more and can be fairly unbalanced compared to original. Despite being heavier they're also weaker.

Aftermarket have their own brand and designs. BBS and OZ fit into this category. Might look the same but way stronger and better balanced because of the multistage manufacturing process.

Basically you get what you pay for. My personal favourite wheels are BBS on a Porsche, but I am biased!

Get the rims checked out for warp and hub fit. I'm more than happy to be wrong but it's worth it to get the driving fun back on track

Hope it all works out!

oze172

Hi

Tried to reply a couple of times but the posts are getting blocked for some reason?!

There are loads of good aftermarket wheels. Basically stick to wheels from companies with own designs and brand, BBS and OZ for example, that use advanced manufacturing methods such as rim spun or even forged.

Replica wheels are quite different and much more liable to cause problems on high performance cars because whilst they look the same they are physically quite different and therefore will behave differently.
Just to clear, Replicas can look the part but don't assume they will perform like OEM at the edge of the envelope.

Do a search on alloy wheel manufacture, loads of good sites about that explain the different manufacturing methods.

J

philooo

Ok so here is an update, I changed the rims and tires. I bought a set of used OEM 5 spoke rims. I checked the rims and they were round and true before mounting the brand new tires.

Same vague steering problem at speed with shaking.

So, ..
- Can I check myself for things like torque on the steering system ?
- I see some aftermarket part selling bushing or stuff like that, suggesting me that the OEM part might be of inferior quality ? can they be checked ?

If anyone had a list of things to play check, I'll be happy to spend more hours on this as it really drive me nuts.

Also is there something to get stiffer/sharper steering ? mine feels too much like a GT. My wife Mini cooper got sharper steering ! May be my whole suspension needs to go to PSS10...$$$