Steel Wheel Lateral Runout

PostPost by: type26owner » Tue Aug 31, 2004 4:58 am

All my 4.5J steel wheels had an estimated 3-4mm lateral runout at the bead when they were brand new. Doesn't this change the scrub radius enough from one side to the other per revolution and could this possibly introduce some steering which manifests itself as a shimmy? Obviously tires can have this problem too I'm guessing. Has this been the main source of my dithering problem all along? Anyone face cut the wheel's mating surface to the hub before to remove that lateral runout? I've already tried to have people that straighten wheels for a living do mine but none will attempt the Lotus wheels.
-Keith
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PostPost by: rgh0 » Tue Aug 31, 2004 6:42 am

Keith

3 to 4 mm lateral runout in the rims is too great in my experience and would give you a shimmy / stability problem especially if it combines with any runout in the tire of a similar order of magnitude. I would be looking for about 1 mm run out max.

If the wheels are the original Lotus steel wheels then they will probably keep distorting and moving around and I dont think any straightening or face cutting will remove the problem permanently.

If the wheels are the replica ones made by the Elan factory in Australia and sold as I understand it by the usual suppliers in UK and USA I am surprised they had this much runout. As they are substantially stronger and made to much better tolerances than the original wheels. They should be capable of being straightened to remove any significant run out present in them like any conventional steel wheel.

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PostPost by: type26owner » Tue Aug 31, 2004 1:08 pm

Rohan,
Bought these welded steel wheels a couple of years ago as new. Don't know who made them but they have the thicker reinforced centers. Two out of the five have had the clear coat flake off completely within six months and the other three are chipping and peeling. The quality of these wheels has underwhelmed me. Still with the stresses I'm putting through these wheels I'll stick with the steel ones. Has anyone had the newer reinforced welded steel wheels crack or bend yet from normal usage?

They should be capable of being straightened to remove any significant run out present in them like any conventional steel wheel.

That's what I thought too. No one has the tooling required I guess so it's no dice. I'm to chicken to take a sledgehammer and potentially bash them to destruction. Going to consider other alternatives which I can pull off with relatively low risk.

How about tig brazing a bead around the contact area using nickel bronze brazing rod and truing that to remove the runout. By building the surface up in short quick passes of tig brazing one can minimize the heat distortion and residual stresses.
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-Keith
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PostPost by: rgh0 » Wed Sep 01, 2004 3:54 am

Keith

It does not sound like your wheels came from the Elan Factory as the ones I have seen come out of their have been made to modern wheel building tolerances using laser cut centres and modern commercially available 4.5jj rims.

3 suggestions on ways to get them straightened none of which include a sledge hammer !

1. Find a good quality wheel straigtening place run by people old enough to respect an Elan and work with them to machine up an adapter for their equipment to handle the Lotus knock on wheels.

2. If you have an old hub and access to a big enough lathe mount the hub and wheel in the lathe. Make some form of rolling press tool to mount on the lathe tool carrier and press against the rim and work to straighten the run out as you spin the rim in the lathe. Some gentle heating of the wheel in the location you want to move would also help

3. Mount the wheel with a hub attached in a shop press and work very carefully around it in small steps to press out the lateral run out. Again gentle heating would help.

After any exercise like this stripping, crack testing and repainting is probably a good idea.

Alternatively get a new set of wheels and make sure the run out is OK before accepting them.

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PostPost by: khamai » Wed Sep 01, 2004 5:59 am

Hi Keith,

First I've not thanked you for all your development work over the past months. GREAT stuff!!!

With regards to the wheel run out. I'll confirm that it is the likely cause of the shimmy you're feeling. As you've discovered it's near impossible to find anyone that does wheel straightening. Would you consider going to Panasports? They are light, strong, a ton stiffer & stronger. Available both in bolt-on & KO. Needless to say I'm a big fan of them.

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PostPost by: type26owner » Wed Sep 01, 2004 2:10 pm

Rohan,
I don't have the tooling necessary to brute force bend the wheels into the correct shape. What's more buying or building that stuff will cost a small fortune and lots of my weekends. I've pondered all the possible options and have proposed the best solution earlier in my opinion.

My solution has one niggling problem though. The conical female pocket that the KO nuts engages would be tilted slightly from being square to the contact plane and shifted off center relative to the rotation axis. This is assuming it's at all aligned to begin with. Very likely the nut would make line contact on one side only. Tightening up the nut to the 240 ft/lbs might elastically deform the wheel so there is contact around or it might not. There would likely also be a shearing force exerted on the drive pins. Maybe this is okay and maybe not. Certainly not ideal though. Only way to fully correct the runout and reduce these errant forces is to true the KO conic to the new mating plane and the lug-centric drive pins. What a pain! Realizing I should do a static finite element analysis of this scenario and see how bad this might be.

Kiyoshi,
If you and I sat and had a beer and I told you all I know about engineering loaded structures with aluminum you would likely not be so enamored as a result. Aluminum has no lower fatigue limit while steel does. This difference is monumental in my opinion. I'd be constantly inspecting them for cracks. I don't need that kind of constant apprehension associated with stressing my aluminum wheels.

You were dead on correct by stating the RE92's were good. Can't wait to try them at Thunderhill. Thanks again!

As you can see I'm caught between two undesirable situations.
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-Keith
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PostPost by: khamai » Thu Sep 02, 2004 3:49 pm

Understand about AL. I'm not a engineer or metalergist so absolute no claims about what is a better material.

I can say that I've seen plenty of stock Elan steel wheels fail. (do understand you don't have stock wheels) And, I've only seen 1 Panasport fail (on a FF car).

On the Elans that I've had where I've gone from stock steel to Panasports I found the steering to be more precise, more direct, which in turn gave me more confidence.

So, I can only say that I and many others have had good experiences with them.

Good to hear about the RE92s! And... they're cheap!!! One tire for my truck (SVT Lightning) was more than all 4 on my Elan!

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PostPost by: type26owner » Thu Sep 02, 2004 7:28 pm

Kiyoshi,
The Panasports are my backup plan if my repair effort goes poorly truing these steel wheels. I've managed to mangle the aluminum wheels on my Maserati in the past so I'm a bit hesitant to reduce the margin of error again. Besides my wife is going to throttle me if I spend anymore money on the Elan in the near future. :ph34r:
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-Keith
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PostPost by: khamai » Fri Sep 03, 2004 4:54 am

Keith... use my technique to blunt the "wife noises" about spending money on the Elan... Use what the magicians use and get them to put their attention on something else. In my case I'm buying an Elise! She's not said a thing about my Elan bills. :lol:

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PostPost by: steveww » Fri Sep 03, 2004 8:27 am

Ahh Great minds think alike B) I have diverted SWMBO with my interest in buying a new Mini :lol:

I have recently fitted 5x13 minilites (panasports) to my S4. I kept the same tyres 155x80x13. I got a significant improvement in stability, that extra 0.5" of width really made a difference. I guess because it has increased the car's track and taken some curve out of the side walls. I am really pleased as I appear to have more grip but the car is still progessive and predictable. Of course it still moves around more than a modern car but that is all part of the fun :D
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