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TECHNICAL MOTOBRICK WRENCHING In Remembrance of Inge K. => Project Custom Motobricks => Topic started by: diesis on April 17, 2025, 08:57:36 PM
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TLDR: Anybody have detailed information on the brake rotor bolt pattern for the 3 spoke front rim for a K75? I'm building a rotor adapter to a GSXR 1000 fork/caliper front end.
If you're bored:
I continue on my mission to break perfectly working things for no good reason other than "it's fun/I learn something when I do it wrong the first time". I'm doing a front end swap on my 93 K75C - it's getting a donor 2007 Suzuki GSXR 1000 set of forks and calipers (using a kit from https://www.jaxgarage.com.au/product/bmw-fork-conversion-kit-7s/#content-1 (https://www.jaxgarage.com.au/product/bmw-fork-conversion-kit-7s/#content-1)). I have both 4 spoke "snowflake" rims and 3 spoke rims for the bike. I was able to source kit parts to do the swap for the snowflake rim, but haven't found them for the 3 spoke. So, figured I'd try and design my own. I'll go out and caliper out the rim I have, but wanted to see if there were more precise measurements out there I could check against. Or if someone knows of a rotor adapter out there, all the better.
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I'm not real sure what you are talking about. I have swapped three spoke for the Y spoke wheels with no issues. Are the wheels you're working with all K75 wheels?
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I'm pretty sure they are: Y-spoke have 4 bolt holes to mount the brake rotor assembly on the cast rim, and the 3-spoke wheels have a 6 bolt pattern to do the same https://shop.maxbmw.com/fiche/DiagramsMain.aspx?vid=51745&rnd=10232024 (https://shop.maxbmw.com/fiche/DiagramsMain.aspx?vid=51745&rnd=10232024). Are the two wheels functionally interchangeable on a standard K75 front end - Absolutely. But, when adapting for the Suzuki GSXR fork spacing I have to adjust rotor position to line up with the calipers and thus was anticipating adapting off of the cast rim mount holes. I hadn't realized the difference between the rims initially and assumed the 3-spokes would work easily (and thus bought / powdered a set of 3-spoke wheels) and the following conversion kit: https://www.jaxgarage.com.au/product/bmw-k100-rotor-adapter-kit-1/#! (https://www.jaxgarage.com.au/product/bmw-k100-rotor-adapter-kit-1/#!) before reading the fine print (I still haven't learned to RTFM apparently) that it only works on the Y-spoke. I've got a set of Y-spokes and will run the kit on that, but figured I might as well try and adapt a 3-spoke as a learning experience.
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I might as well try and adapt a 3-spoke as a learning experience.
It looks like you're finding the fun in modification you set out to have! 103123
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The r1100 3 spoke has the 6 mounting points for the brake disk. The k4v series have 4 just like the y spoke.
Thats where the mixup might have happened.
Also check Hedgehoggarage for their conversion sets to gsxr forks. However changing to usd forks might be cheaper to do with R forks nowadays.