Isolastic durometer, old, new, by brand...

I've searched and read, more questions than answers now. I've read several posts about vibes being excessive AFTER replacing, and the aftermarket having wild variation in other parts, now I really want to know: 1) Is there more than one maker of replacements? 2) Quality level, rubber being as close to original properties? I just want to make sure I get the best quality parts for the repair work I'm going to do. Sorry if this has been covered, but I couldn't find it.

I replaced my iso rubber donuts about 6 months ago.

I got them from Phil at Fair Spares America and they are just fine.

I also would not hesitate to order from Fred and Ella at Old Britts.

The horror stories I think you are referring to involved a bad batch of harder rubber being supplied sometime
over 10 years ago.

I do not believe this has been an issue for a long time now.

Yes our DynoDave has tested a variety, which may or may not apply on what ya might get today. Search that if no ones posts it first.
After feeling what soft decayed cushions felt like compared to hard oxidized felt like and the very common complaint of more vibes on renewals than prior I decided to just cut through the Gordian Knot by bench grinder bevel a 45' angle leaving about 1/4" flat rim. So far on two Combat I've very pleased I did.
You can always expect some break in seating wearing to occur on new installs over 1000 miles or so. Can't really judge your isolastics till then and must be on good proper aired tires as those play right back into isolation dampening. I leave the rear as supplied and add two more to boot. Tested on 500 mile days to feel more comfy in saddle than standing around, didn't find limit I wanted to get off.

Concours, aswell as just replacing the bushes. It is good to take the time to check the trueness of the pipe housings, as this effects how easily the iso's can ocillate. Read the tech section form Old Brit some good info there to really get smooth riding.

Cheers Richard

The observed "droop" as shown by the concentricity error on this front mount (boot removed) is typical bearing the weight of the engine? Or a sign the iso rubbers are totally bagged out? I measured the side to side backlash with an indicator, front is .025", rear is .020". I had considered shimming to tighten, but don't want to throw good effort after bad. I have every reason to beleive these are the originals fitted, 11.000 miles, 38 years ago.

What do the 38 year old PTFE washers look like? I couldn't even find the dust from mine. It sure was smooth though.

Dave
69S

DogT said:

What do the 38 year old PTFE washers look like? I couldn't even find the dust from mine. It sure was smooth though.

Dave
69S

Click to expand...

LOL, remarkably, they look ok, intact. I think indoor storage has a big part in it, when the adjoining steel washers get rusty, the iron oxide rapidly gobbles up anything nearby. I've seen it in many other applications.

DogT said:

What do the 38 year old PTFE washers look like? I couldn't even find the dust from mine. It sure was smooth though.

Dave
69S

Click to expand...

"Someday," I say to myself, "Someday I will compile an acronym dictionary," but I never do. Some acronyms refer to a technical area and some are just things everybody says. Well, maybe everybody says those things, and maybe not, but everyone on the internet seems to love them. Things like PTFE for instance. I ask myself, "Is that like a joke thing or a technical thing." Usually when someone tells me it becomes immediately obvious. "How stupid of me," I say to myself, "I should have realized that!" And then I go around wishing I was quick and "with it" too. I know I could look it up, but I suspect it's technical. So, please, kindly, what does PTFE mean.

Joe Schlaberdowski said:

So, please, kindly, what does PTFE mean.

Click to expand...

https://en.wikipedia.org/wiki/Polytetrafluoroethylene

https://andover-norton.co.uk/en/shop-details/16380/isolastic-ptfe-washer-06-3556-06-0578-

L.A.B. said:

https://en.wikipedia.org/wiki/Polytetrafluoroethylene

https://andover-norton.co.uk/en/shop-details/16380/isolastic-ptfe-washer-06-3556-06-0578-

Click to expand...

Thanks L.A.B. I knew I should have realized.

Joe Schlaberdowski said:

So, please, kindly, what does PTFE mean.

Click to expand...

L.A.B. said:

https://en.wikipedia.org/wiki/Polytetrafluoroethylene

https://andover-norton.co.uk/en/shop-details/16380/isolastic-ptfe-washer-06-3556-06-0578-

Click to expand...

teflon is an interesting substance that I have worked with during a period in the 90's. Interesting that Wikipedia says they used teflon in the 40's in the nuclear field, yet they must have discovered it does not hold up. My products were prohibited from using teflon coated wire when used in nuclear plants in radioactive "hot" environment...

The pix at ANIL appears to show a dark teflon (usually white). Back in the day the original iso washers were supposedly bronze powder "loaded" teflon for wear resistance. Plain white teflon is not considered to hold up or resist pressure "creep". I tried to find and buy bronze loaded teflon and never could find a source (many decades ago). There was a period when tan polyurethane was being sold as ISO washers.
Glad to have good ones available...

I worked with the white & dark back in the 80's. Used it in low load apps. for conveyors.... Bearings & wear strips under belts/drag chains. resistant to boiling seawater & freezing brine. Delrin was much more suitable for bearings and sheaves though. Wonderful stuff with major price difference between white and dark. Gotta watch machining it because it comes after you with a vengeance if you become greedy with the cut.

My Inorganic Chemistry prof in undergraduate third year told us Teflon was discovered quite by accident. The story goes over at Dupont Labs they were decommissioning some old Fluorine gas cylinder tanks that had sat unused for more than a decade. When they cut the tanks open they found this white plastic like substance at the bottom and later determine it had great low friction properties. Analysis showed it to be PTFE.