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Is 8th gen fork offset 40mm?


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  • Member Contributer

Hello gentlemen,

 

Does anyone know for sure if 8th gen fork offset is the same 40mm as 6th gen and 5th gen?

 

I am in the process of replacing my 5th gen triple clamps with 8th gen top triple clamp and 6th gen bottom triple clamp as part of a suspension upgrade and brake delink [Yes, I am taking photos and yes, will post a build thread].

 

My notes say that somewhere my research found that the offset of 8th gen triples is 40mm, same as 6th gen and 5th gen [though 5th gen uses 41mm diameter forks]. I did not record the source of my data.

 

BUT - I started measuring the triples before installing today and found 8th gen with almost 2mm less offset than the 6th gen. 8th gen on left, 6th gen on right. Measured from edge of fork leg holes to edge of steering stem holes. Steering stem holes same diameter.

 

Thanks for any input.

 

IMG_1081.thumb.JPG.8aacca3bf8e13aa8a7dbe0b68f27a7cd.JPG

IMG_1084.thumb.JPG.9b078ba43434e1378f1cf44231924a00.JPGIMG_1085.thumb.JPG.d92a1c8d5cb48ac73ef6a786eb0519fa.JPG

 

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  • Member Contributer

I've measured "a few" triples in my time...but not the 8th-gen's.  My usual method is to pop some fork legs into the triple clamp and bridge them with a steel straight edge/ruler.  Then I can more accurately measure the distance between the straight edge and the steering stem hole.  (Or the stem, if you're measuring the bottom triple, but the stems often taper.)

 

Then you have to know the diameters of the fork legs and the stem hole and add or subtract 1/2, depending on which side you've put the straight edge or measured to.

 

It cannot have 48mm offset.  (NFW!)

 

Ciao,

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  • Member Contributer

Hey JZH - thanks for your input. NFW is a mild understatement for 48mm offset! I forgot to describe that I was only comparing the two lower triple clamps, not attempting to determine actual offset, so the 46.94mm and 48.61mm are from the datum line across the edge of fork leg holes to edge of steering stem hole, only to compare the two measurements from the two stems. When I measured the offsets center to center, the difference settled down to 1.13mm, and, finally, when I measured the 8th gen top triple offset using the method you recommended, it comes in at 39.98mm...close enough to 40mm for me to go ahead with assembly and far too accurate for government projects.

 

Do you have the RC51 SP1 forks in your possession yet? Do they offer the clamping range you hoped for?

 

Cheers

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  • Member Contributer

So 40 it is!  Glad you've got that settled.

 

I'm coming to CA in a couple of weeks, so I will fondle the forks then.

 

Ciao,

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