Metal Guru

Just talked to Jim Dorociak tonight as he just sent my RH centers and outer hoops back after re-finishing them (they came out great; I highly recommend Jim for all three piece wheel restoration work). Now my wheels were the first set of RH's he's ever worked on. He was impressed with the quality of the RH wheel and thought it compared favorably with the Speedlines he has worked with. The RH wheel is so close dimensionally to the Speedlines that he was able to assemble one of my outer hoops to a Speedline center and inner to straighten it.

As for the Speedline inner/outer sections being thicker that an RH, the only way to know is to measure each with a big set of point mics. If this is a fact, then the Speedlines will weigh more than RH's if the centers are equivalent. When it comes to weight per unit volume, aluminum is aluminum no matter what the alloy. If Speedline used an alloy with a lot of silicon, it wouldn't be very formable. Heat treating in the wrought aluminum alloys is very important to strength.

I used to work in wheel manufacturing. My opinion is that all wheel hoop assemblies that are formed by spinning aluminum make a light but fragile wheel when compared to cast or forged aluminum. Spinning also allows for a lower priced wheel due to the low tooling cost.

Both RH and Speedline wheels are approved by Tuv so I question whether there is an appreciable difference in strength between the two.

V

Interesting info Paul. I have a set of RH 3.6 wheels for my 993TT. Wheels are 9x18 ET52 and 11x18 ET40. The outer hoops of the rear wheels appear to be prone to bending.. Do you think it would be possible to exchange outer hoops for real speedline outer hoops? Given the the fitment was so close. Are there equal number of bolts? This will only be interesting if in fact the real speedline outer hoops are "stronger". Other than that, I'm really happy with my RH's.

cobalt

Paul.

I agree proper heat treating of the cast center and inner barrel are critical especially with the alloy used. Casting medium/processes, alloys used, make a big difference also. I believe Speedlines are pressure cast does anyone know if the RH's are, or are the gravity fed. The RH I have had to check was an older 38 bolt wheel and we are talking years back. The measurements I recall were less on the inner barrel but similar on the outer lip to the speedline. IIRC the Speedline barrel measured 5mm the RH was only 3.5mm. They might have changed manufacturing process since. Because I don't have any of this documented my numbers might be off as my memory isn't as good as it used to be. But I recall saying at the time that the RH wheel is at the minimum thickness I would feel comfortable using. I find aluminum alloys loose impact resistance at around .125" due to grain size and manufacturing limitations and at 3.5 mm your just a hair over that. The only manufacturing process that can overcome the strength issues with thin walled castings is BBS. The cast the wheel with a much thicker barrel and then roll it under high pressure and heat to reshape it. They give the wheel added strength this way and IIRC don't require the machining to control the shape. Machining if not done properly can weaken a casting also if allowed to heat up during the process, although I doubt that is an issue here.

To begin with this statement is false. Alloyed Aluminum can vary depending on % of alloying agent used albeit a relatively small difference. Aluminum alloys can vary by as much as 10% depending alloy composition this can up to 2 pounds ona wheel or more.

Weight/density is determined primarily on the casting design/alloy used and process. The barrels weigh less than half of the overall weight and the center hub is the bulk of the weight. IIRC the RH hub uses more material than the speedline by design.

I can tell you that the density of a high magnesium content aluminum alloy like ALmag35 is less than that of an aircraft aluminum like A356. Almag35 is relatively light and strong without the need to heat treat to obtain ultimate tensile strength. A356/356 will be useless without a T6 or solution age cycle. Purity levels of the alloy used will determine ultimate strength and process control will guaranty greater strength achieved. An alloy like ALmag 35 will have a typical tensile strength of 40KSI and a min of 35KSI in as cast condition A356 will see similar numbers in heat treated condition. More importantly than ultimate tensile strength is yield and in the case of these 2 alloys the heat treated A356 will be higher with a typical yield around 25KSI vs Almag35 which is closer to 20KSI. If we want to take this further grain refining while casting along with growth based on time and temperature used on the alloy during heat treatment will make additional changes to strength.

Along with all the other things discussed you need to consider such things as alloy Fatigue Endurance Limits, Compressive Yield and strength, Charpy Impact, Specific Gravity, Modulus of Elasticity and processing parameters.



So as you can see it is not all Apples.

speednme

Hey for every seat there's an A$$...with that said, while $4500.00(9k on the otherhand is ludicrous) might seem somewhat high it is not that unreasonable. The rarity of the wheels have something to do with it.

Just for giggles, I went to a Benz dealer(please don't beat me..lol) the other day. I saw a sl 550 with a set of 18" AMG wheels. The dealer wanted an extra $10k for the wheels. It was a good laugh.

Haggle while you can..

Damian in NJ

http://cgi.ebay.com/ebaymotors/GENUI...Q5fAccessories

Same guy.
He originally was asking an outrageous $995 for this but came to his senses-somewhat.

Metal Guru

I'm looking at a table of "Typical Characteristics and Physical Properties of Castings for Alcoa Aluminum" and the weight in lb/.cu.in. varies between .097 and .102. Alloying elements make up such a small amount of the alloy that as you can see, the difference is negligible.
Will a stronger alloy allow the designer to use less material? Absolutely, but wheels are consumer goods as opposed to aircraft. There is a tradeoff between performance, weight and cost.
My guess is that these three piece wheel rims are made from a wrought, non-heat treatable alloy due to cost considerations. Doing a quick web search today I found a manufacturer of aftermarket wheels making rims for three piece wheels out of 5000 series aluminum and forming them by spinning.
Unfortunately, we most likely will never know what alloys the manufacturers are using. If anyone would like to sacrifice one of their Speedlines, however, I'll get it tested

Metal Guru

Quit driving through potholes and you'll be fine

The hole patterns are the same. I'd pm Jim Dorociak and inquire with him. He has told me that he has to straighten a fair amount of Speedlines that come his way. Still, he's the guy to ask.

cobalt

Alcoa alloys on that chart are specific to most standard aluminum alloys used in aircraft and commercial applications. In the case of Porsche alloys we are talking specialty alloys which are proprietary. Assuming you are looking at the chart I believe you are I don't believe you see any high magnesium content alloys that also have a high silicon content, it is usually one or the other that is high.

Because the process and alloy is proprietary we will never know the facts. Looking at the chart you will see a wide variety of alloys some requiring heat treatment for this type of application others that achieve their ultimate strength in as cast condition and others that are self aging. The tighter the process control the more consistent the results. Usually these are expressed in minimum levels and that is for separately cast test specimens which are required to achieve a higher min level than the casting itself.

So yes using the Alcoa charts you will find a variety of alloys that encompass the vast majority of standard applications. Specialty alloys like the one we are talking about more than likely are smelted by the foundry producing the parts or are manufactured by Alcoa/Alcan etc without them being listed on charts you have.

I have a number of alloys here that would blow your mind on what can be achieved in as cast condition. The problem is most have their own series of issues regarding manufacturing process. Some of which are so hard they cannot be cut with a band saw blade others shrink erratically and others that are easy to control and very strong none of which are supplied by Alcoa.

There is a variety of alloys some of which are forgotten that are very unique in their characteristics because they are to temperamental and require strict process control or are just very costly to use and most foundries won't be bothered pouring.

There are Boron/Titanium/Aluminum alloys, high copper content aluminum alloys all of which have a significant variation in weight based on the quantity of alloying agent and vary in mechanical properties.

I thoroughly understand your point although I have tons of research from my grandfather when he managed Bendix's Eclipse Pioneer Program from 1930 to the late 1950's. Most of the info we use today was a result of years of R&D that he headed and released to the US government during WWII reducing national scrap rate by 40% and allowing the US to manufacture the magnesium and many of the aluminum alloys used for the war effort and still used today.

My info is based on his research and working with alloys like this first hand. After 3 generations and my personal 25 plus years of producing aluminum and magnesium castings I can assure you that the speedline is a stronger wheel than the RH. I cannot specifically point to the reason because the info is proprietary but you do pick up a few things working with the material first hand.

So what do we know?

We know the original RH's used a 38 bolt pattern and a thinner barrel. We don't know what alloy is used on either wheel although we have an idea to the primary alloying agents used in Porsche wheels. We know the early RH wheel had a bulkier casting for the center. We know from personal experience the RH will deform far more so than a Speedline although both are susceptible to bending because we use a low profile tires with thin sidewalls. We know sidewall strengths can impact the amount of damage incurred and that using a wide tire only reduces sidewall height allowing a greater chance of damage to either wheel.

So I guess the only answer here is:




BTW Jim is good at what he is doing and he has learned a lot over the past year or so. After many conversations, trial and errors he has overcome some major hurtles, I hope I can say I was of some help.

jim dorociak

Guys have not read this thread for a while because I assumed someone new just found the ebay ad and wanted to talk about the price. Wow you guys are sure active. Anthony you have been a great sounding board and I do appreciate the emails and phone calls. You are right at times last year it was very painful learning the nuances of Speedline wheels. I think between all of us at this site we have a pretty good handle on these special wheels. I keep looking at my Techart wheels made by OZ Racing and these gorgeous Speedline wheels and I might just have to build a set for myself. I posted some pictures of a test fit 11" under turbo quarters with NA trailing arms. You guys are going to be so jealous. Jim