Iridium Plugs

[gripper]

A friend of mine has advised against using NGK Iridium plugs. He says in the motorcross world there is some evidence of the side electrode coming off and trashing the engine. Any body got any thoughts or experience on this subject?Dave E

[Dell Boy]

My only thought is why fit something you are unsure about when in my experience C7 [my choice] or C8`s last for many,many thousands of miles. If it aint broke dont fix it. I get mine from my local car parts shop for a little less than £4.00 each. Derek.

[Interpol2471]

I have been using the iridium plugs for some time now and have seen no degredation in the electrode, maybe it's because I dont thrash my engine to 1000's of rpm like the race boys do in motox.

[Interpol2471]

In fact to add to that I have iridium plugs in all of my bikes including the LC and that is thrashed with no issues to the plugs also so far. I also used the NGK race plugs with tiny electrodes in my RS125 race Honda years ago with no issues but then again I fitted a new plug every race and threw them away. I guess it's like everything personal experiences count for everything and we are all allowed to have opinions related to these. I am sure for your use the plugs are fine and to be sure check them regular when you do your weekly / monthly riding checks.

[Ian]

Well, I can only say that my Commander would regularly foul the RH plug (and only that one) in prolonged heavy traffic. I met an NGK man at a show, who said the Iridium plugs were designed as much as anything to counter plug fouling. Fitted them, never had a plug foul since. I change them every two years.

[johnbirchjar]

I've never used Irridium plugs since I buggered one one of them getting it out many,many, thousands of miles ago,(to damned expensive!)NGK's have allways served me well and have my vote. On an entirely different tack,but reverting to a subject mentioned before,re:brakes on IP2s & Classics,I have now managed to get the discs drilled on my Classic,what a difference!! Forget about fourpot callipers, stainless steel braided hoses and mounting the callipers before the tele forks,for about a 75% increase in braking,just have the discs drilled,cheap and simple,(and they look good to!!)regards,J.B.

[graham]

Why would drilled discs improve braking in the dry? I thought it just helped clear water in rainy weather.My simple brain looks at the surface area swept by the pad to decide how efficient a brake is. Taken to the (Illogical) Conclusion, if you drill the whole disc away, there will be no braking at all...I've seen extreme wear patterns on old drilled discs showing increased wear at the PCD of the holes which seems to clarify my thoughts.How can a brake pad grip a hole ? Am I missing something? Iridium plugs. Standard C7Es are lasting 10000 miles plus for me so the non-fouling properties of the expensive iridium variant are an unnecessary expense for any Yorkshireman or Scot worth his salt. Happy to be proved wrong Graham.

[rustynuts]

I believe the theory is that as they heat up, the resins in the brake compound can vapourise and cause the brake pad to float on a cushion of gas. Holes in the disk provide a vent path. Modern good quality brake compounds are supposed to be less susceptible to giving off gas when hot.

[Dell Boy]

I recognise that the "cushion of air" is just a theory but it just does not seem credible. The pressure exerted by the hydraulics on the pad is phenomenal. I`m sure that pressure would squeeze any "gas" out of the sides of the relatively small pads. Perhaps the discs run cooler with the addition of holes & therefore friction is increased causing better braking.Reminds me when I collected, in 1976, my nearly new Mark 3 Commando with front & rear chrome plated discs, from Luton. Coming down the M.1. in light rain the lorry in front of me started braking. I applied front & rear brakes as per usual & absolutely nothing happened. Forward motion continued at the same speed which was about 60 m.p.h. & the rear of the lorry was growing larger at a rate of knots. Heartstopper!!! Then the water cleared of the discs & something started to happen & I braked as hard as I dared on a wet, greasy road. I am still hear so I obviously didn`t hit the lorry.I have always wondered what Design Engineer came up with the "blinding" idea of putting an exceptionally slippery chrome finish on a friction surface which wore off anyway. Also in 1973 when despatch riding in London on a Commando I spun a "U" turn & heard a metallic tinkle on the road. Something made me look on the road where I spotted one of my front brake pads. It was excessively worn & just fell out as there is nothing physically holding them in. Again, who designed that brake? Lockheeds? If I hadn`t spotted it, at the next set of red lights I would have sailed straight through! I know, poor maintenance & all that but that`s a despatchers life. Your bike got ridden into the ground. The commando was completely knackered after 6 months & I sold it to a german who was going to ride to Turkey on it even after I had told him it was clapped out. I gave him the workshop manual which I usually never part with once bought but I knew he was going to need it! Derek.

[johnbirchjar]

I do'nt know the scientific answer or the physic's of drilled discs, I only know the difference is immediately apparent,will the holes get bigger over thousands of miles? only time will tell,regards,J.B.