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Old September 6th, 2016, 05:24 AM   #1
jc462
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Wheel weight reduction - Help

I have seen various posts referring to wheels that were lightened. From what I can gather it seems like people have the rims machined in some manner.

Does anyone have additional information on this procedure, e.g. how much weight can be removed, any safety issues, a recommendation on where to have this done?

My ninja does exclusive racing and track day duty for both my son and myself.

I’m old and fat and need all the help I can get plus I’m the only 250 in the field running against all 300’s.

Thanks
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Old September 6th, 2016, 06:40 AM   #2
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Old September 6th, 2016, 07:46 AM   #3
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As an old & fat rider myself; the safest, most cost/benefit results will be achieved if you remove the wheels, grab a wheel in each hand and raise them above your head. Do that for 3 sets of 10 every day. For even greater results: a little duct tape applied to the lips just before meals is extremely effective to reduce lap times!
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Old September 6th, 2016, 08:18 AM   #4
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Old September 6th, 2016, 08:23 AM   #5
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Old September 6th, 2016, 06:22 PM   #6
jc462
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Hahahahaha

I knew I'd open myself up to the "Hey dude visit the salad bar once in a blue moon" response.

I'm tryin for sure...was 216lbs down to 190ish and still going - I get it this will make the biggest difference.

Put the bike on a weight loss program as well - just wondering about the wheel thing as that is probably the most effective place to reduce weight if possible.
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Old September 6th, 2016, 07:04 PM   #7
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Quote:
Originally Posted by jc462 View Post
Hahahahaha

I knew I'd open myself up to the "Hey dude visit the salad bar once in a blue moon" response.

I'm tryin for sure...was 216lbs down to 190ish and still going - I get it this will make the biggest difference.

Put the bike on a weight loss program as well - just wondering about the wheel thing as that is probably the most effective place to reduce weight if possible.
In all seriousness; you do not want a wheel failure. I'm assuming you and your son race for shits & giggles. The bikes are designed for a typical rider and you & I are on the wrong side of the bell curve! The benefits of wanting to reduce unsprung, rotational forces by shaving unknown metallurgical, structural material from wheels cast in Indonesia should be considered carefully in the context of a weekend warrior! My (unwanted lol!) 2 cents!
It is very possible you might crack the wheel and your son disintegrates it!
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Old September 6th, 2016, 07:05 PM   #8
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Quote:
Originally Posted by jc462 View Post
......... Put the bike on a weight loss program as well - just wondering about the wheel thing as that is probably the most effective place to reduce weight if possible.
Please see this:
https://www.ninjette.org/forums/showthread.php?t=117501

There is no much weight that can be reduced from the wheel without affecting its strength.
The smallest profile of tire will help with both, lineal and rotational inertia.
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Old September 6th, 2016, 07:33 PM   #9
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Thanks for the responses - Points taken on safety which is why I was asking.

I definitely race for fun, my son is 14 and is learning more and more each time he throws a leg over a bike - super cool to watch.

I definitely checked out this thread (multiple times).

Quote:
Originally Posted by Motofool View Post
I've done many of the usual things, e.g. exhaust (full area P), lightweight battery, ceramic wheel bearings, 415 chain and sprockets, speedo cable removal (with cool replacement spacer from DC dude), clip ons, front fender removal.

Investigating aluminum fairing stay and replacement gauge, lightweight brake rotor, fan removal, key removal, switches and housing removal and any other stuff I can learn about.

I wonder if wheels from another bike like RS125 could work somehow.
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Old September 6th, 2016, 07:44 PM   #10
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Ain't much weight to shave from the bikes, but it can be done... Always safety first though
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Old September 6th, 2016, 09:17 PM   #11
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Good riding technique will swamp out small weight reductions in a hurry. I bet the time spent practicing on a track will be more important than the same amount of time spent trimming a little weight off the bike.
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Old September 7th, 2016, 05:25 AM   #12
jc462
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Quote:
Originally Posted by Triple Jim View Post
Good riding technique will swamp out small weight reductions in a hurry. I bet the time spent practicing on a track will be more important than the same amount of time spent trimming a little weight off the bike.

True dat. Definitely learning corner speed and momentum with this machine. I love to study riding - been to Corner spin, YCRS (3x) and CSS (levels 1 - 4).

Some folks are naturally good - I on the other hand need to work much harder to achieve a portion of a really talented riders skills. Never stop learning and tying to improve.

That being said racers are always looking to shave off a few ounces where ever they can.

This season a racing buddy bought a sprocket from a guy in the paddock - the next day the guy (another racer) came to him and said he forgot the thing had titanium hardware that he wanted back.
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Old September 7th, 2016, 06:11 AM   #13
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In all seriousness though, check out various race tire weights and put that into your decision.

If you're going to be buying tires anyway, might as well get a set that can drop some weight from the outside of the wheel (the spot where mass with have the most effect on rotational inertia).
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Old September 7th, 2016, 11:20 AM   #14
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Weight reduction is very often a gotta pay to play kind of thing.

Some old threads from racers that cut some serious weight but they are not leaving any stone unturned. We are talking grinding and cutting any extra metal from frame tabs, losing ones that are not 100% necessary, doing smaller chain conversions, drilling things out, LiPo battery, among lots of other tricks, most of that stuff isn't that expensive. Once you start milking oz's here and there with Ti bits it starts to get pricy.

You want lighter wheels... buy a set of lighter race wheels, anywhere from $1500 - $4k for the crazy stuff.
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Old September 7th, 2016, 12:02 PM   #15
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Quote:
Originally Posted by jc462 View Post
plus I’m the only 250 in the field running against all 300’s.

Thanks
So sell the 250 and get a 300. It'll cost you less than trying to lighten the 250 enough to compete.

I echo what others said. Have you considered liposuction or lat band surgery?

Unsprung weight/rotating mass reduction has a big effect, but look at cost/benefit. There's a lot of room for weight savings before you start carving up mission-critical components willy-nilly.

A smallest-possible lithium battery will save you a lot of weight... ripping the wiring harness apart and chucking all but the essentials, ditto. Rig a keyswitch eliminator and save a couple more pounds. And none of those cost anywhere near what dedicated ultralight race wheels do.
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Old September 8th, 2016, 05:36 AM   #16
jc462
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Quote:
Originally Posted by subxero View Post
Weight reduction is very often a gotta pay to play kind of thing.
I hear ya on that one - hence the ask on machining the wheels.

Quote:
Originally Posted by adouglas View Post
So sell the 250 and get a 300. It'll cost you less than trying to lighten the 250 enough to compete.

Unsprung weight/rotating mass reduction has a big effect, but look at cost/benefit. There's a lot of room for weight savings before you start carving up mission-critical components willy-nilly.

A smallest-possible lithium battery will save you a lot of weight... ripping the wiring harness apart and chucking all but the essentials, ditto. Rig a keyswitch eliminator and save a couple more pounds. And none of those cost anywhere near what dedicated ultralight race wheels do.
Thought about the 300 - probably would make more sense...problem is I don't have an abundance of sense sometimes.

Seriously - the 250 is really my sons bike that's why I am not willy-nilly and I check everything out before I make any move. I raced it this year in addition to my R6 to put it under some pressure and work out kinks. He does track days on it when he's not riding dirt or kart tracks.

This bike is a stepping stone for him if he decides to continue on.

I've done several things to the bike, e.g. harvested a lithium battery from one of my other race bikes, chain conversion etc...

Really poking around at options now that I'm in the off-season from racing.

I appreciate all of the responses and good advice - especially the motivating words folks offer around the rider weight reduction modification
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Old September 8th, 2016, 07:01 AM   #17
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Don't machine the wheels. Don't worry about weight. The small amount you'll lose even with expensive Marchesini's won't do much for you. They won't keep with Ninja 300's or KTM 390's or Yamaha R3's no matter what you do. Those have at least 10 HP on the Ninja 250. You can keep up in the corners but will get dogged in the straights.

Instead, get good tires, good suspension and then focus on rider skills. Don't race to win, race to have fun and learn! Race the lap timer.
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Old September 8th, 2016, 07:03 AM   #18
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Old September 8th, 2016, 08:58 AM   #19
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Quote:
Originally Posted by jc462 View Post
......... Really poking around at options now that I'm in the off-season from racing.......
Quote:
Originally Posted by choneofakind View Post
In all seriousness though, check out various race tire weights and put that into your decision.

If you're going to be buying tires anyway, might as well get a set that can drop some weight from the outside of the wheel (the spot where mass with have the most effect on rotational inertia).
Weight saved in tires provides a double gain for both acceleration and braking.

Besides the force (along the chain) necessary to lineally accelerate the mass of both tires (rotating or not, just the mass or weight), an additional torque (radius of sprocket times force also along the chain) is needed to overcome the moment of inertia (angular mass or rotational inertia) of both tires while they change speed.

Force along the chain is limited by the torque of the engine, which has a max.
For that reason, heavier tires will consume more of that torque, slowing the processes of acceleration and braking down.
Discs brakes are superior to drum brakes in that aspect.

Please see:
http://hpwizard.com/rotational-inertia.html

https://en.wikipedia.org/wiki/Moment_of_inertia

As @choneofakind has explained, for two more or less similar wheel-tire combinations, the mass farther from the center of rotation is the more important to reduce resistance to acceleration and deceleration as much as possible.
In that sense, 16" wheels and tires are better than 17" ones.

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Old September 8th, 2016, 10:14 AM   #20
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One of the fastest 250 riders I know is 300+lbs. ijs.....
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Old September 8th, 2016, 10:33 AM   #21
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One of the fastest 250 riders I know is 300+lbs. ijs.....
Momentum riding.

The less you slow down, the less you have to accelerate.
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Old September 8th, 2016, 12:43 PM   #22
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One of the fastest 250 riders I know is 300+lbs. ijs.....
Ask Misti about Stuman! He's not on a 250 and he's not 300 lbs but he's a big man and holy holy; he's fast!!!!
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Old September 9th, 2016, 05:43 PM   #23
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Change bikes - Go to a real GP bike

You're missing a real easy way to have the best.

Buy a MotoGP 125cc bike. New, they were $10k, with spares $20k. Weight 155 pounds, 40hp.

You can pick one up with tons of spares: pistons, cylinders, gear sets for the six-speed trans, etc. Prices seem to be in the $2-4k range, which is the same price as a used Ninja. But you get a sophisticated race bike with nothing that needs to be done to it. It will run with the Ninjas, but brakes and turns for real. If dragging knees is important to you (seems to be on this forum), this bike will let you drag knees, boots and elbows.

That's what I did for my boy at that age. I told him, when that bike had taught him everything it could, he would know exactly what bike to race. But he surprised me, by staying with it until he quit racing. (job and family)

It was really fun watching him stuff 600's in turns and out braking them by a mile. But the best thing was putting it back in the truck - no ramp! Lift up the front, place on tailgate, lift up back, done.

Just some thoughts,
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Old September 12th, 2016, 10:36 AM   #24
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