Iso question

freefly103 · Feb 7, 2016

Recently changed all ISO rubbers on my 70 with standard replacement rubbers i.e. I did NOT upgrade to the vernier type. It was a bit of a challenge, but eventually go the job done, and used the existing shims spacing to 10 thou per the manual. I use a Dave Taylor type head steady.

Am experiencing an increase in vibration, especially through the seat.

Just wondering if there is a "break in" period and if the vibes will decrease over time or should I expect an immediate improvement?

The new rubbers were significantly harder than the marshmallow consistency old ones that I replaced.

Cheers,

Joe

Danno · Feb 7, 2016

It might loosen up over time, but you may have it shimmed too tight. The advantage of the verniers is you can easily tune the mounts to suit; too much vibe, turn them out a bit. Too wobbly in the turns, tighten. Instead of going by clearance, make it do what you want.

DogT · Feb 7, 2016

I had the same issue. I can't say the new iso rubbers have loosened up any. I think the old rubbers were more spongy than the new ones. I think hobot used to drill them out. Vibration is tolerable on the road. The engine spring will help idle rpm vibration if you want to install it.

Towner · Feb 7, 2016

Perhaps they have been too loose before. Have you adjusted the head steady as well ? Maybe it has to be realigned.

acadian · Feb 7, 2016

Recently did this myself, and running a Taylor head steady BUT I am also running the Hemmings ISO collars... I suggest you do the same

Fullauto · Feb 7, 2016

I replaced mine with all new isos some years ago. I immediately dubbed it "The Atlas conversion" because of the vibes. It eventually settled down but it takes time and use.

grandpaul · Feb 7, 2016

It just seems to me that the cost and time involved in replacing, properly adjusting and tuning the non-adjustable shimmed isolastics is not a good value as compared to buying, installing, adjusting and tuning the vernier type. Especially when you are adding an aftermarket head steady and/or suspension upgrades. It then becomes a simple matter to re-adjust as required to dial-in the package.

DogT · Feb 7, 2016

I got the Hemmings adjusters too. Didn't do anything for the vibes, just made it easier to adjust. Bike was really smooth with the old iso rubbers and no PTFE washers, they disintegrated. But it flopped around like a fish. Hemmings adjusters go on the original fitment.

lcrken · Feb 7, 2016

Joe, I think the extra vibration you are noticing is normal with new isos. By the time most of us replace them, the old ones are mush. I recently replaced the isos in one of my bikes with new ones from Andover, and it definitely has a bit more vibration transmission. From past experience, I expect it to mellow out a little with time, but not to go back to where it was, unless you keep the bike another 40 years or so. I think the reason it's so noticeable in my bike is that the old isos were totally shot. Sounds like you are in the same situation. I haven't found it to be a problem for riding. It's still way less than the vibration you would get with solid mounts, and nothing to make the riding experience less pleasurable.

There has also been some discussion here in the past about differing densities of the rubber in replacements over the years, but I don't recall the conclusions. Not that it matters a lot today. I'm confident that the ones Andover sells are quality products.

Ken

Torontonian · Feb 7, 2016

Well I vote for softer. Not worn out old original rubbers but brand new soft type. If you can get them. The smoothest Commando I've ever owned was the 70 model with soft rubbers. You could start the bike up , stand back watching it idle and see the motor hop up and down. After 2200 R.P.M. no more hoppings , just a smooth transition to happiness. Back then I always strived for .08 with the feeler gauge. Have used/tried several vernier types on several Norts over the years and none smooth the vibes out as that. Yes the Taylor headsteady was one of the best systems I purchased recently , not affecting vibes , but allowing rail-like tracking and handling. Good luck.

Interbak · Feb 8, 2016

The original rubbers used on shimmed iso's were softer than MkIII and much softer than any of the modern replacements. Dyno Dave did some measuring and here's a link to some of his findings. http://atlanticgreen.com/images/frontiso.jpg I recall he explained his measurements further somewhere, can seem to find it at the moment. Adjustable iso's will gve you convenience, but not a smoother ride. I've heard a lot of people complain about this, they figured that they spent a lot of money upgrading the system and should get a less vibration for their money. I've never seen it work out that way.

B

Nater_Potater · Feb 8, 2016

DogT said:
I think hobot used to drill them out.

He once said that he added extra rubbers to the rear mount, then ground the front rubbers in a shallow taper, something like the shape of a discus, until the edge was around 3/8" wide. I'll be trying that this Spring when the front iso gets replaced. Updates to follow...

Nathan

aceaceca · Feb 8, 2016

I knew there was a reason for leaving my 71 iso's alone. Who wants to put some rocks hard rubber in there and lose that beautiful smooth ride. Whoever is making the replacements needs to revisit the compounds being used. There are some high tech alternatives to old black rubber.

WZ507 · Feb 8, 2016

Below is a quote from a previous thread where iso modulus was rehashed. Might have some value as the modulus of a current offering from one vendor is quantified.

shore-hardness-t20120.html?hilit=shore%20A#p262348

WZ507 said:
Re: Shore hardness

Postby Fast Eddie » Sat Aug 16, 2014 12:47 pm

When I spoke to Norman White about this he was really quite annoyed, it "touched a nerve" as we say.

His main point was that the factory spent a lot of time and money establishing the correct shore hardness. So why do these people with lesser knowledge and resources think they can 'improve' on the design?!

His argument was directed mainly at those selling harder ones (like mine were) but the argument applies equally to softer ones I would suggest.

Norman did tell me exactly what the shore hardness should be, but I've forgotten. He also went on to say that new AN ones are correct, and in his opinion, the only ones to use.

I fitted them and they certainly contributed to my huge reduction in vibration.

Click to expand...

Just measured Shore A durometer of a new set of Andover Norton vernier-style isos. Made multiple measurements on each individual rubber donut and found all measurements to fall in the range of 45-50. FWIW.

Peter R · Feb 8, 2016

I too replaced the iso rubbers, and noticed an increase in vibration, unfortunately, 3years and several thousand km/miles later, the iso's did not loosen up. :evil:

Danno · Feb 8, 2016

No reason vernier isos should be any less smooth than shimmed ones given he same rubbers. Clearance is clearance whether taken up by shims or screws.

freefly103 · Feb 9, 2016

I went with the old style rubbers as nothing I read on here indicated convinced me that the new style were any better for vibration, just easier to adjust. What I neglected to do was research if replacing the old rubbers with new actually reduced vibration. It doesn't appear to be the case in many accounts that I have ready on here including mine.

I changed out the Dave Taylor HS with the Norvil one just as an experiment - made no difference at all.

The bike is pretty smooth until 3000 rpm, then vibes are very buzzy especially through the seat until just above 5000 rpm when they seem to smooth out a little.

I've only put 100 miles or so on the these new rubbers. Will report back after a few hundred more.

pete.v · Feb 9, 2016

Nothing is set in stone here. The clearance may say .010 but it can be any variable. It may be ,010 a side, .005 a side, 020 a side maybe, more, maybe less and anything in between. You need to add and take away until you achieve the desired results. Also, it maybe more or less on the front than on the rear.
Don't just set to .010 and assume that it, it's not.

PeterJoe · Feb 9, 2016

A few years ago I bought iso mounts from RGM Motors. With these mounts installed the vibration was pretty severe. As a matter of fact within a month of riding the rear left hand turn signal broke off at the mounting bracket due to vibration. I later replaced the iso mounts with genuine Andover Norton mounts and they worked much better. I felt very little vibration above 3000 rpm.

Peter Joe

DogT · Feb 9, 2016

I got the ones listed at Old Brits which should be Andover products, at least marked as so, for the 71 model and they do have a buzz in the pegs and bars, but tolerable. Yes, the adjuster type will not affect the vibration. I've tried different settings with the Hemmings adjuster and found no difference unless I get it real tight.

Iso question

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