Ariel Owners Motorcycle Club

I am trying to decide whether to buy stainless head to barrel studs or steel ones.
Is the expansion rate with stainless such that it would be a problem in that area ?

thanks for any insights !

Hi

As you have already highlighted, stainless steel has differing properties to that of a known grade of steel, rate of expansion, ductility, tensile strength etc. Whilst you could compare values if you were able to ascertain which grades are used I would , in the case of head fixings, stick with the original specification. I would however use stainless nuts for cosmetic reasons, well lubricated with Copperslip or Neverseez grease.

Regards Mick

Acme Stainless do head studs (or maybe bolts...) in stainless, so by that I'd ascertain that its oK to use for this application.

Steel imho

Vincent.vanGinneke wrote: Mon May 18, 2026 8:49 amIs the expansion rate with stainless such that it would be a problem in that area ?

The answer to your question is given by science. "Steel", "stainless steel," and "cast iron" all come in various flavors, with various coefficients of thermal expansion. The difference in thermal expansion between the unknown cast iron alloy and the unknown alloy used by reproduction "steel" studs could be larger or smaller than the original steel studs used by Ariel. It also could be larger or smaller than the unknown alloy used by reproduction "stainless steel" studs.

Luckily, the coefficients of thermal expansion of all of these are in the same ballpark. For a 6" length and temperature difference of 100 ℉, the difference in expansion of any of these combinations only will be ~0.001". Since torquing a 6"-long, 5/16" stud will stretch it by ~0.025" (~0.015" for 3/8"), the amount any of these combinations would loosen or tighten the stud would be minimal.

With thermal expansion out of the picture, the reason to use stainless is it doesn't rust, and the reason not to use stainless is it galls easily.

Best Material for studs is High Tensile steel that can be tensioned to the required figure, without stretching. Silver steel is a high carbon steel that is brittle and useless. The best studs/bolts for auto work are rolled threads. Nev