Alright so I've come into a set of BST's that were living on an S4RS, and they're to go on my HYM1100S. I've pulled the Hyper's wheels and measured the critical points, issues are as follows... On the fronts, the distance between the outer surfaces of the wheel bearings are 126.45mm for OEM and 110.24 for BST. I'll chock up the 0.21mm to bearing install variance and that leaves 16mm to make up. I'll whip up a couple 8mm spacers for either side and that'll be sorted easy. The less easy bit is the brake discs. The distance between mounting surfaces is the same, thankfully, but the BST hubs have a 6x80mm bolt pattern and OEM uses 5x90. So, I need to find rotors that have a 6x80 bolt pattern and 305mm diameter with 9.75mm offset. Does anybody know of a bike that uses such a size? If not, I'll have to make my own disc inners. Then on the rear, the spokes are fouling against the caliper by a couple mm. I could make a spacer plate for it, a few mm shouldn't really effect much but as a rule I'd prefer not to push the wheel off center at all. Possibly a smaller rotor would work, allowing me to push the caliper further inwards towards the rotational axis and away from the sweep of the spokes. Might also be able to machine down the caliper, though I'm not sure how much meat there is to take away before I start eating into the internals. You guys have any ideas here?
I think some of your measurements are awry (particularly the thickness of spacers required at the front) I would be surprised if the bearing face distances are actually in decimal parts of a millimetre because designers do not usually work that way. Also, be careful about measuring disc offsets and which face relative to the bolt flange you are using.
Like I said I'm sure there's some slight variance based on how well the bearings were installed, but I'm pretty confident in my measurements. The OEM is likely 126.5 and the BST is 110 or 110.5. I see engineers go halfway quite often but rarely is it a random .XX number. For width at the bearings I placed the wheels horizontally, with the inner race on bottom sitting on a pedestal with a flat top (just a doodad I'd turned up on the lathe), and measured the depth from the top of the inner race of the upper bearing with calipers. If there's real doubt here, I can bring the wheels in to work, jig them up, and measure them with our articulated probe system lol. As for the disc offset... I didn't even bother measuring, just took numbers from Galfer's website (they list the relevant specs for each bike... unfortunately there's' no function to search by a particular feature). They have the HYM1100S listed with a 9.75mm offset. The previous owner of these wheels has stated that the rotors he had on it are a 15mm offset, and comparing the two with the ol eyecrometers that seems to be about the difference between mine and his. I did find on Galfer's website that rotors for a 998S as well as those for an S2R 1000 will both come close enough to probably work, though I'll need to turn up spacers for the calipers to accomodate the larger diameter discs. Still searching for a more direct fit option, and brainstorming what the hell to do with the rear. On that end, I'm leaning towards a 1 or 2mm spacer under the wheel, coupled with shaving down the caliper.
Sorry to interject but you said outer to outer width was 126.45 then 120.24. That’s a variance of 6.21mm You mentioned 16mm.? Am I missing something ? I had similar issue with BST’s I fitted to my R1. I just had a pair of new spacers machined to match original wheel width. No washers.
Ope, so I did. 'Twas the beer talking. The BST's measure 110.24... just edited it to fix. Thanks for catching that. And yes, will be easy enough to turn a couple spacers to correct this, the width is really the easiest problem to solve in this ordeal.
Both wheels measure 105mm at the rotor mounting face, giving a centerline of 52.5mm. The distance between the bearings at their outer face is above for both wheels, but you make a good point in that the bearings may not actually be centered on the centerline of the wheel. In order to check I'll need to bring the wheel to work and check it with a probe as the bearing face and rotor mount face are too far apart to measure against each other with the instruments I have at home. Though I may be able to measure up to the hub lip and then down, depending on how it lines up... will check after coffee. For bore of the center hole, are you wondering at the diameter of the bearing seat or the inner dia of the bearing (aka the axle diameter)? And, forgive me, but why is this relevant? The axle does fit, for what it's worth... if it didn't I'd be on the hunt for bearings with the proper dimensions. Good info regarding measuring disc offset. I'm inclined to stick to using Galfer's numbers rather than measure directly though, and here's why... I don't care what the offset actually measures. I only care to match whatever it is. And given that I don't know for certain how Galfer measures it, me measuring mine directly and then using their numbers for other rotors creates a point of possible error if I measure differently from them. Given that the number is irrelevant and all that matters is to match it, if they have the Hyper listed as a 9.75mm offset then I just need to find a rotor on their site (thus using their same measurements) that matches or comes close to that. There does seem to be a number of options with the 6x80 pattern and 64mm inner diameter, and most of them are 320mm so I'll space the calipers and get a brake upgrade out of all this as well. Current best contenders are the 996, 998 and S4R 1000, with 9.5mm offsets and 4.5mm discs (HYM is also 4.5)... but there aren't any good options on eBay for those bikes. If you know of any other models with 9.5mm offset I'm all ears. If I can't find anything for those, the S2R 1000 uses 5mm rotors with 10.5mm offset, which should be close enough to let the calipers absorb the difference in their float even if I didn't shave a bit off the mounting face which I likely would. Mind you these offsets are taken from what Galfer has listed.
Having you folks as a sounding board is certainly helpful. Still having fits about the back end. Haven't come up with anything better than when I first posted, which is to make a 1-2mm spacer for the wheel and then shave the caliper down a bit for the rest of the clearance, but neither side of that seems ideal. I'm also not entirely sure how much clearance I need to compensate for caliper float. You have any thoughts towards this?
Get an S4R rear caliper hanger and disc. Pretty sure they are smaller diameter than the more modern Hyper 1100. I once put my 996 wheel on my M1100S and the spokes fouled the M1100 caliper as the disc is larger. Don’t piss about with spacers etc, change the disc and caliper mount.
That's not a bad thought. The S4R has the same size disc but there are others that might work... the 998 is 25mm smaller in dia, gotta look into it further to see what else is out there.
So the only donors I'm finding for the smaller rear brake are the 748/998/996 which use a 220mm 4 bolt rotor vs the 245mm that my Hyper and most other use. Trouble now is that the caliper bracket they came with doesn't have any provisions for a speed sensor... and presumably the rotor doesn't either. Fine by me, I hardly look at my speedo anyway, but I'm concerned that if the ECU sees rev's and gear shifts without seeing any wheel speed, it'll give me a trouble code. Assuming the bracket would even fit the axle.
