Isolastic

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Egholt

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I have upgraded my Mk2A to Isolastic front and rear .
The ID of the inner tube of the rear iso is much bigger than the OD of the long mounting stud .

Have any make bushes to fill the gab ?

Michael
 
Original Iso's had a "neat" fitting bolt/tube...it appears that Modern units are produced from seamed tube that is "Big" in the bore.
Some Experts , "experts" say that this clearance allows the bolt to find it's correct place due to frame/bolt hole mis-alignment . and once tightened up maintains its position ...in other words the ends of the tube are clamped between the frame ,and not located by a close fitting bolt. Not the best engineering method ...so in answer ...i would prefer a neat bolt/hole .
If you intend to bush the hole you will need to establish a good hole,removing the weld flash first. But remember the bush is going to have a very thin wall.
 
I had the same problem. Rolled a bushing out of sheet metal and improved the fit. It is not perfect, but...

Greg
 
Why not use the original equipment and just buy the Hemmings adjusters?
 
I have seen this before, and the so called 'expert' who claims that this is done to allow correct centering of the bolt in the frame and tube is talking complete and utter BS.
This expert, (by any chance the man with the beard ? ), has a batch of incorrectly made iso's that he has been is trying to flog for years.
These incorrectly made isolastics should not be used, and any claim that this is done on purpose is false, this material is unacceptable by any standard.
 
I had some Norvil Mk3 ISO that where made of seam welded tube the internal bore was 14.5mm not counting the weld itself. I considered making some form of bush to take up the play but because of the fact the weld would need removing for best fit i just couldn't be bothered trying to improve on a badly made part.

I ordered new AN ones from the ever helpful Mick Hemmings and fitted them. They are drilled steel bar an have just less an 20 thou clearance on the bolt. They fitted together with the remaining stainless adjustable ends of the Norvil kit plus being thicker wall they didn't buckle when the grub screws were nipped up unlike the thin wall Norvil tubes.
Buy AN ones an save yourself lots of unnecessary hassle is my advice.
 
Yes I have those Norvil parts. No issue till someone mentioned it. I rolled up shims for front and rear (next time it was apart) so the fit is even both ends and re-installed. There is no difference to my insensitive backside! I'm not defending the guy and I hardly buy from him any longer but there is more likely a greater misalignment in the rest of the frame mounts. The cobblers he does talk are the instructions to tighten and back off half a turn for 010". With 25ft/lbs torque I get 015" following instructions. Using the pitch and working out number of turns is a crude way of doing it inaccurately.
 
I bought Norvil ones and wont be using them, just measured, the tube is 3/4" (19mm) OD the ID is 15.25. thats a hell of a lot of clearance on a 1/2" bolt , not even 2mm wall thickness, Are the ones from RGM the same ones? or better quality?
 
madass140 said:
I bought Norvil ones and wont be using them, just measured, the tube is 3/4" (19mm) OD the ID is 15.25. thats a hell of a lot of clearance on a 1/2" bolt , not even 2mm wall thickness, Are the ones from RGM the same ones? or better quality?
Click to expand...

Don't know about Norvil or RGM as I always buy Andover Norton parts. This particular iso tube (too large ID) has been sold by AN as well for a while however recently I received the right size tube again. These imperfect tubes can be used without problems by turning and loctiting 30mm steel sleeve bushes in both ends of the tube.
 
The thin section where the grub screw is locked is way to thin to prevent the section buckling ..it's yet another bodge to keep costs down.



nortonspeed said:
madass140 said:
I bought Norvil ones and wont be using them, just measured, the tube is 3/4" (19mm) OD the ID is 15.25. thats a hell of a lot of clearance on a 1/2" bolt , not even 2mm wall thickness, Are the ones from RGM the same ones? or better quality?
Click to expand...

Don't know about Norvil or RGM as I always buy Andover Norton parts. This particular iso tube (too large ID) has been sold by AN as well for a while however recently I received the right size tube again. These imperfect tubes can be used without problems by turning and loctiting 30mm steel sleeve bushes in both ends of the tube.
Click to expand...
 
john robert bould said:
The thin section where the grub screw is locked is way to thin to prevent the section buckling ..it's yet another bodge to keep costs down.



nortonspeed said:
madass140 said:
I bought Norvil ones and wont be using them, just measured, the tube is 3/4" (19mm) OD the ID is 15.25. thats a hell of a lot of clearance on a 1/2" bolt , not even 2mm wall thickness, Are the ones from RGM the same ones? or better quality?
Click to expand...

Don't know about Norvil or RGM as I always buy Andover Norton parts. This particular iso tube (too large ID) has been sold by AN as well for a while however recently I received the right size tube again. These imperfect tubes can be used without problems by turning and loctiting 30mm steel sleeve bushes in both ends of the tube.
Click to expand...
Click to expand...

Like I said AN does supply the right size iso tubes again but if you already have one with the imperfect tube adding the sleeves will do the job and just don't tighting the grub screw that much rather use some loctite on the abutment threads.
 
madass140 said:
I bought Norvil ones and wont be using them, just measured, the tube is 3/4" (19mm) OD the ID is 15.25. thats a hell of a lot of clearance on a 1/2" bolt , not even 2mm wall thickness, Are the ones from RGM the same ones? or better quality?
Click to expand...
I am relying on the one fixed end cap and a shim at the other end in the tube to centre the bolt. I can see it would be nicer to have a good fit in the tube overall but I don't have that sort of excessive clearance that you have, more like 030" shimmed down to 020". I guess he got closer when he first introduced these....they were bought around 2005/6 I think.
 
OK , so now Im looking for ISO with the correct bore of 12,9 mm .

Where can I buy these ?

Michael
 
Just measured my, new and still in the packaging, AN rear and the ID was 0.522" (13.3 mm), perhaps suggesting that AN and RGM (0.525" spec) are the same part since the sizing appears well within mfg tolerance.
 
well today I modified (bushed) the Norvil Iso's, I machined some 5/8" x 1/16" WT tube down to 15.12mm about 35mm long and put a longtitudanal groove on the outside for the welded seam inside the Norvil tubes, pressed in with 290 Loctite, now has 13.1mm ID. much much better. another small project today, make the weld in gussets to bring the early swingarm up to later spec.
Oh, also about the Norvil Iso's, the mating face for the friction washers on the stainless threaded end caps were not machined flat therefore encouraging faster wear of the fiber/teflon washers, they are now flat with 100% contact area.
Oh and Norvil did not supply the grub screws for the adjuster caps as well.
 
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