Rear wheel with rotor brake substitute

At one time I was running an oddball low profile rear tyre, 55 aspect. Great grip but it raised the revs 1000rpms for the same speed as with typical 80 or 90 aspect tyres. So I expect a 17 rim would do similar. Mostly ok, but not so good on really high-speed rides against other Laverdas. When they were doing 5 and 6k to keep up I had to do 6 and 7k for the same speed. I went back to a more typical tyre aspect
 
If my calculation is right, changing from an 18" to a 17" wheel and keeping the sprockets, it would be equivalent to keeping my 19T front and changing from a 36 to a 38T rear. Not quite 40 but better than the 36.
 
Chuck3CL said:
That's Ok Cam, appreciate the gesture. I may just stick with the 36 for now-tell you why....I just got back from a test run with the KLR650 wheel (albeit without rear brakes yet) and it handled very well. Very responsive in the turns.
And going from the 18" to 17" wheel knocks off a lot of that 'too tall' feel in the gearing.
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Measure out the circumference of both your 18 and the 17 Chuck. Easy to do on flat ground, mark the tyre and wheel it one rev. Be interesting to compare the diff in ratios.

You can maybe buy KLR sprockets in 530 and 38-40T? Or another make and do some machining. On my Z1000 hub I used Z650 or Z900/1000 sprockets - they have a small centre hole so might be a good candidate for machining out to 120mm and drilling 8 new holes.
 
our race bikes run 17" rims as we wish to race with slicks and you cannot get a slick to suit an 18" rim, rear slick we run at the moment is 17" x 160 x 60, next year plan is to run a 17" x 180 x 55

right now we use a standard 19 tooth front sprocket machined down to suit a 520 chain but that may change when we convert to the 180 rear tyre
on the rear we use anywhere from 37t through to 42t depending on which track we are racing on, have 4 sprockets machined in 520 pitch in each size from 36, 37, 38, 39, 40, 41 and 42
Broadford is 42 tooth, PI is either 39t or 38t, Hidden Valley is 40t, etc

My race sprockets are custom made as they mount on the inside of the cush drive but now that we are having issues finding blanks probably go to CNC from now on, far easier, plus we even get our company name engraved on the sprockets with CNC
This is a 40 tooth to suit a GSXR cush drive

rear sprocket
 
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Nice work Red.
Pretty sure Maurice runs stock 18's on Black Betty and same gearing Broadee and PI.....? Chime in Mo, I find that amazing considering the speed difference of both tracks. Just goes to show the grunt BB has i spose.
 
hooksey said:
Nice work Red.
Pretty sure Maurice runs stock 18's on Black Betty and same gearing Broadee and PI.....? Chime in Mo, I find that amazing considering the speed difference of both tracks. Just goes to show the grunt BB has i spose.
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just means Mo is too tight to have a range of sprockets to suit each track 😂 :ROFLMAO:
 
Nice looking kit, Red. Will any be available in 520 for retail to purveyors such as myself? That Gixxer looks very close to what fits my Triumph rear hub - can you give me the dimensions - centre hole and bolt circle PCD? I've got the 37 I machined from a blank I bought from you last year (or was that 2019?!!) but if I need to alter gearing, it'd be great to have a source in Oz.

Interesting to ride PI and Broady with the same gearing ... must be a huge diff in top speed. When i raced I tried to gear to avoid that big gap between 2nd and 3rd. Only tracks I've ridden that required 2nd were Winton and Turn 10 at PI. CR gearbox would solve that issue - obvious why the factory made them.
 
Another alternative would be to machine down an old Laverda sprocket and turn it into a sprocket carrier that will fit off-the-shelf sprockets from a common late model type of bike with a larger centre hole. Like the BMW G310 sprocket pictured below. They list a 40T with a large enough centre hole to bolt onto a custom carrier. There may be others that are more common. The BMW one was just the first one I came across that provided dimensions.
 

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After yesterday's test ride, I'm confident at present to use the 8 hole Lav 36T with 120mm spacer on the KLR cush, giving me an effective 38T using the 17" wheel.

I've asked Red about the possibility of buying a 40T, 120mm id from him if he is willing to produce it.

Ordered a new brake rotor and waiting for the caliper from eBay. Last task is to fit the brake by either cutting down the Lav brake carrier for a smaller space on the axle and putting an additional bracket on that, or modify the KLR brake support arm to fit.
 
motoddrob said:
How did the c/l of the rim to sprocket offset compare to the original rim/sprocket?
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Absolutely no difference. I gave it a pretty good workout and the bike tracked rock solid (both with or without hands on the handlebars).
It feels better, and the 17" makes it less tall than it was with the 36T 18".
It felt more responsive (less sluggish in the cornering). Unfortunately I could only ride within a 10km lockdown radius so I couldn't use my 'favorite' out-of-the-way roads to put it to the edges. And, because I left the KLR tire on it for now, flipping the wheel over to reverse brake&sprocket sides, I was running the reverse tire tread pattern with 80/20 treads.
So, still using the original Lav rt side axle spacer.
 
motoddrob said:
Well thats handy to know.
It seemed too easy
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That's what I thought too. This went much better than I expected. I think Red might be able to make a 40T sprocket too. The brake will take a bit of of nutting out but I don't have the parts yet. Waiting for new rotor and caliper.
 
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