UPPER Fork Diameter

I know the Rocket 3 has 43mm inverted forks, however NOWHERE can I find the diameter of the upper fork tubes. I am looking at having Custom Dynamics make me some custom wrap-around LED turn signals, and they insist that my tubes (which measure 8.5 in around) are 57mm, but my math puts them closer to 66 mm..

Anyone know the answer on this one? I don't want to get it wrong and end up wasting a huge amount of dough on something I can't return,.

I would like to say that I called Triumph USA, and asked about this, and was told they would not tell me, there was no way for me to find out, and they have a very STRONG stance on non-triumph approved accessories. WTF? He told me essentially "just go measure it" like I'm a feckin moron in a rude tone, but I KNOW the fork-tube is ~8.25 in around, and then when it comes to doing the math to get a diameter, the part-maker and myself come up with TOTALLY different numbers, and I can't afford to hedge 300 bucks on a "maybe". Thanks, Triumph, you arseholes.

Ok dude I measured mine at the lower tree which I will check to make sure the upper is the same diameter after I go to the shop and hunt up a 2 to 3 inch micrometer. I believe they are but right now with a vernier caliper I get 2.318 inches diameter and Circumference of 7.2822117711 inches which is 58.8772 mm diameter and a Circumference of 184.968179 mm.
Let me go to the shop and get a micrometer so see how close the vernier is.

Ok I get 2.320 inches with a cold ass micrometer so that is 7.288494955 inches in circumference, which is a diameter is 58.928 mm, and a circumference of185.1277719mm

Thats a .002 difference between the instraments which I am sure there is some manufacturing tollerance. But I am sure there is some. I did not check if both forks were the same diameter as there still will be some tolerances.
Also this is a 06 classic not sure if the Roadster's are the same or not.

Now let me stick up for corperate Triumph USA. I doubt very much if they have a blueprint for every part on the bike in the USA as that would be like expecting them to be able to rattle off every tooth dimension on every gear in the bike. Triumph engineering in the UK would probably have that on file some where I am sure but how readily accessable it is I could not tell you.

I just think your being a wee bit picky.

I hope I did not upset you by sticking up for them I just think your asking a wee bit to much of them.
Anyway I hope the measurements help you. I did not check the upper mount as I figure your going to mount the turn signal down on the lower where on comming traffic can see them.

Wow, desertwOlf, that's a helluva introductory post!!

Seems simple enough to me to go buy a cheap slide vernier and measure the diameter yourself. Any wrap-around mounting would surely have some tolerance built in for clamping anyway??

No way would you need the precision measurements Warp has gone to the trouble of getting for you. In any case, they seem different to your bike.

I agree with Warp that you're asking a lot for them to produce this figure. It's not what you might call a commonly used measurement.

But welcome to the forum anyway, and you can see already the amount of trouble our members are prepared to go to to help out if they can.

Dang Warp ...vernier calipers ? Good Eyes .............mine aren't what they used to be.

I'm getting 58.87 -58.88 mm ( 2.3177-2.3181" ) with a varience of 15 degrees between mic and bike ( 65f mic and checked against a standard and 50f bike ( garage heat yeah! ).


MY bike is a 09 standard.

Manufacturing tolerances (of the forks ) and temp differences are to blame for our discrepencies I'm sure.

I would suggest that Desertwolf take his bike to a local small machine shop ( and one with a bike or 2 in the parking lot doesn't hurt ) and have them check his particular bike.

They may possibly do it for free or a minute fee.

Have your wallet out as you are taking time away from them making a living and they should be compensated for it.

..welcome desertwolf...duct tape and baling wire..:whistle:

RadioFlyer said:

Dang Warp ...vernier calipers ? Good Eyes .............mine aren't what they used to be.

I'm getting 58.87 -58.88 mm ( 2.3177-2.3181" ) with a varience of 15 degrees between mic and bike ( 65f mic and checked against a standard and 50f bike ( garage heat yeah! ).
MY bike is a 09 standard.

Manufacturing tolerances (of the forks ) and temp differences are to blame for our discrepencies I'm sure.

I would suggest that Desertwolf take his bike to a local small machine shop ( and one with a bike or 2 in the parking lot doesn't hurt ) and have them check his particular bike.

They may possibly do it for free or a minute fee.

Have your wallet out as you are taking time away from them making a living and they should be compensated for it.

Click to expand...

I always wondered how close the verniers were. They were my dads and dated 1965. Somewhere I have his Starrett gear tooth Vernier caliper, I am guessing from the late 1950's

Well Scott, a good tradesmans should be able to read a vernier calliper to within .002" and a micrometer to .00001" so your dads instruments and your eyes are right on.

Triple trouble said:

Well Scott, a good tradesmans should be able to read a vernier calliper to within .002" and a micrometer to .00001" so your dads instruments and your eyes are right on.

Click to expand...

Trifocals help recalibrate the eyes

Egads trifocals ...not that :shock: .... I only have bifocals .

I did go and finally find/dig out my Vernier Caliper, which got me ~59.9 MM. My caliper was buried in the very bottom of one of the tool chests. Go figure.

Secondly, I wouldn't have been so upset w/ Triumph except they TOLD me they had the measurement, and that they would refuse to give it, period. I asked if it was possible, I was told "yes, but f you for wanting to put non-triumph approved parts on your bike" in a very rude manner. If they had said "no, we don't have it at hand" instead of "Yeah, I have it but go take a long walk off a short pier" my post would've been completely different. I own several other Triumphs, and have had many of them through the years. Triumph is one of my most favorite companies - so to be treated like that over the phone was a wee bit irritating.

Hell, I can call Harley right now and they'll tell me "Sure, here's the measurement." or "No, but we'll go check that for you". Not "We have it but think you suck so no".

Got my part ordered, though. Apologies if my first post here came off a little rough. I was upset. Also, thank you for all that tried to help me out!