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Cynic

question for the engineers.

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Ok, this afternoon that rear wheel has been in and out soooooooo many times but I now have all the measurements for the spacers and such. Just wanted to ask, more to confirm my own opinion.

The chain run is a mile off with the wheel centred, like 7-8mm. so I know I can get 3mm from using a zxr250 front sprocket (same dimentions but 3mm offset) but to get it to fit real nice and keep it neat I'm going to get the sprocket carrier turned down by 4mm, I can get a mm or 2 with the wheel spacers too.

So what do we think about taking 4mm from the sprocket carrier, the sprocket runs on a machined pcd face rather than being centred by the bolts like the tdr, it just means taking the depth of the tapped threads in the machined face down to 24mm from 29. Sprocket is held with 5xm8 bolts.

What do we think, don't see any issues, shear force on the bolts is little changed and its  more substantial than the original tdr.

Just don't want to be missing something.

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could you re-enforce the sprocket bolts with locktited nuts on the other side of the sprocket carrier?

that would also spread the loading away from the  holes

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Hmm, the internal face isn't square though. Making it square would mean taking more metal out.

The cush drive is packed in there pretty tight too, I did wonder about trimming the outer edge of the sprocket carrier to fit deeper in the hub and trimming the tabs down by the same amount but there is only 6mm between the bearings so that would not have enough mass to resist crushing and then the wheel may not tighten up properly.

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To be honest if it looks right and it don't catch anywhere then do the minimum, seen folks spend hundreds and hours of time just to get it looking like it did before, your after that           " oooh look at that" moment really. Did the guy who you got the drawings from not include this info then? Email him and ask if he can suggest something if it's bothering you.

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Hmm, well, I kind of.......

The Aprilia wheels have never been fitted to my knowledge. Aprilia are kissing cousins to Cagiva, commonly sharing parts so I took a punt on them fitting, the spacers are similar sizes and the wheel does (its snug i'll accept) fit its just the chain alignment that's appreciably different, by 7-8mm. 

Not much if your cutting wood but miles talking about chain alignment.

Ps, mocked up they look ace, less intrusive with the y spokes so keeping the minimal look of the wheels but getting rid of the spokes and being able to fit modern rubber. 

My idea of modification is to be unnoticed unless you know what your looking at. I don't do lairy. 

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The grading (strength) of metric fasteners is done by a proof load test, which basically tries to pull/push the bolt out of the nut to a specified value without damage to the threads.

There are two ways to meet a higher proof load (grade).

1. Heat Treat the parts

2. Make the nut deeper, more threads = higher proof load.

We make parts in the material that we would use for a grade 8 nut that are approximately 30-40% deeper than standard to meet a grade 12 proof load (the highest grade), so as a standard M8 nut is 6.50mm deep your 24mm of thread depth is more than enough to mean that the bolts can perform as they should, if you were left with only 10mm of thread then I would think twice about it.

 

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Great thats the kind of info i wanted. Give that man a beer.

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