Is there really such a thing as an "Axle Stretcher"? ... (eliminate wheel shims)

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Is there really such a thing as an "Axle Stretcher"? ... (eliminate wheel shims)

Post by NorthSouth » Wed Jul 24, 2019 7:33 pm

Hello Fellow Model T-ers,

A very generous and knowledgeable gentleman east of San Diego, CA has offered to teach me how to replace the driver's-side rear axle in my Ruckstell rear-end. It has somehow gotten bent causing the wheel to wobble like a drunken sailor on my 1915 Touring fitted with large drum Rocky Mountain Brakes.

I was told by another old time and respected Model T-er that the shim I discovered when removing the wheel can be eliminated through a process called "axle stretching". He scorned that wheel shims are a terrible thing to have on your car. Further, he explained, "they are not necessary on a properly constructed Model T". And, fortunately, he indicated that the need for these wheel shims can be eliminated when the bent axle is replace.

Jerry King picked me up a straight and solid replacement axle at the Long Beach Swapmeet for $20. I will be removing the rear-end myself to take to San Diego.

My question is, and please don't laugh; ...Without having to buy two new custom length axles specific to large drum Rock Mountain Brakes, does anyone know what this "axle stretching" process consist of? Surely, its is impractical, perhaps even impossible, to actually physically stretch an axle.

My good friend, and guide on most things Model T, Larry "Original" Smith demands that my car be as authentic as possible. Therefore, I would be grateful for any guidance you guys might offer in order to eliminate these incorrect wheel shims during this rebuilt, whether it be by this so called "axle stretching" or by other means.

Thank you in advance for your thoughts and enlightenment.
Last edited by NorthSouth on Wed Jul 24, 2019 7:56 pm, edited 1 time in total.

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Re: Is there really such a thing as an "Axle Stretcher"?

Post by Scott_Conger » Wed Jul 24, 2019 7:46 pm

I would assume that the groove for the axle pinion will be widened, moving the axle outward, and a custom spacer put in the differential.

Yes, metal can be stretched. Valves were stretched with specialty tools when there were no adjustable lifters. I do not see that happening with an axle, though.

Whether or not I'm correct remains to be seen, but there will be an awful lot of work involved in any event, and you'll still have to straighten the axle...good luck with that.

Shims mean more often than not, that the wheel hub is wallowed out as much or more than the axle is worn. Stretching the axle will not cure that malady.

After evaluating the axle and hub for fitness (sometimes they're just shot), I have never had a shim "go bad" and find them to be more than adequate to the task. The key to success is good axle threads, a quality nut, and a good/tight fitment.
Scott Conger

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wayne sheldon
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Re: Is there really such a thing as an "Axle Stretcher"?

Post by wayne sheldon » Wed Jul 24, 2019 8:18 pm

I don't know. The only ways I know of to stretch an axle, will also almost certainly create stress and/or potential fracture points. Done hot or cold, the clamping required would cause sub-surface damage. It is done often to forged front axles, but the rotational stresses on the rear axle makes them much more prone to future fracture from minor stresses required to stretch one. Personally, I would not want to trust a stretched rear axle.

I understand some people's dislike of the tapered shims between the axle and hub. Some of those concerns are well founded. However, provided the wear necessitating the shim is even enough, not oval in shape, or egg-shaped? And provided the key-ways are good? A single steel tapered shim should not hurt anything, or create any significant added risk of fracture or failure. PROVIDED the hub and nuts are properly tightened and checked a couple times the first thousand miles for any sign of significant wear issues.
Steel shims should be used. Any softer metal WILL hammer down and become loose in normal use, and will create a greater chance of future failure.

It Is NOT recommended. However, a slight oval shaped wear can be compensated for by VERY careful use of thin brass (.004 or less!) shim to fill the oval. ALWAYS use in combination with a steel shim, or the brass may hammer itself and be re-tightened into a lock that will not come apart. The steel shim maintains a separation point for future disassembly. The brass shim must be placed carefully into the wear gap, and then all assembled and tightened. RECHECK the nut tightness a few times until the brass assumes it's best fill. Again, that is not recommended as a general practice.

The second paragraph is my opinion. The third is given in part because it is important to try to understand what is happening near the atomic level in order to avoid future problems. Some bad ideas can offer good results, only if well understood.

For whatever it is worth.

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Re: Is there really such a thing as an "Axle Stretcher"? ... (eliminate wheel shims)

Post by Dan McEachern » Thu Jul 25, 2019 1:58 am

what Scott said- press the gear toward the tapered end, remove the keepers, put axle in lathe and widen the keeper groove toward the gear end, replace keepers, press gear back against keepers, make thicker spacer . . . . . . done

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