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Brian Degulis
Joined: 13 Aug 2012
Posts: 415
Location: United States, Florida,
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 Posted: Sat Nov 24, 2012 5:27 pm Post subject: A little Advice On Set Up |
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OK now that I'm getting good with a shifter even if I must say so myself and actually others are saying it and I'm starting to give some of the big dogs a run for thay're money which BTW realy makes me feel good I'm starting to look at the chassis. I'm working with an 02 CRG with a KX 125 running a 40 MM axle (I don't know the wall thickness or stiffness) Bridgestone YLC's and the front end is exactly as I got the kart. After the tires warm up and I start getting grip I'm hooping in the rear. I was running with the rear torsion bar in and today I took it out. That improved it a lot but I'm still hooping pushing thru the hair pin. It's pretty violant to even with a rib vest I'm feeling it in my ribs.
So for a mechanicaly inclined guy (diesel mechanic) That knows nothing about chassis set up what is my logical next step?
Thanks
Brian |
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Mike Unger
Joined: 18 Jul 2001
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Location: United States, Ohio,
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TJ Koyen
Joined: 03 Oct 2004
Posts: 1418
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| Posted: Sat Nov 24, 2012 10:16 pm Post subject: |
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Usually a hop is from too much weight jacking. I'd try taking some caster out or narrowing the front track. Those are two pretty easy adjustments.
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Brian Degulis
Joined: 13 Aug 2012
Posts: 415
Location: United States, Florida,
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| Posted: Sun Nov 25, 2012 6:49 am Post subject: |
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So you guys think the hop is being caused by to much grip? That's logical considering it doesn't happen with cold tires. I read the article and it sounds like my easiest next adjustment would be to lossen the bolts on the mid axle cassete. Right now they're tight. If that doesn't do it maybe try caster. Sound logical?
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TJ Koyen
Joined: 03 Oct 2004
Posts: 1418
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| Posted: Sun Nov 25, 2012 7:27 am Post subject: |
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| Brian Degulis wrote: | So you guys think the hop is being caused by to much grip? That's logical considering it doesn't happen with cold tires. I read the article and it sounds like my easiest next adjustment would be to lossen the bolts on the mid axle cassete. Right now they're tight. If that doesn't do it maybe try caster. Sound logical?
Brian |
You could try that too. I only suggested the front settings because sometimes an axle can "rebound" and cause a hop feeling if it's too soft. Loosening the third bearing would worsen that condition. I was also wary of how a shifter would react with a loose 3rd bearing and 40mm axle. I've never driven a shifter though so maybe I don't know. But it's another quick adjustment, you can make it and see what it does.
If the bearing helps, then you're fine. You might need a new softer axle in the future to solve that issue if the grip gets to be too much.
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Brian Degulis
Joined: 13 Aug 2012
Posts: 415
Location: United States, Florida,
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| Posted: Sun Nov 25, 2012 7:45 am Post subject: |
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Well I don't know about loosening the bearing on a shifter with a 40MM axle either. Maybe one of the shifter guys can chime in.
If the problem is to much grip what about a harder compound tire?
Brian |
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TJ Koyen
Joined: 03 Oct 2004
Posts: 1418
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| Posted: Sun Nov 25, 2012 8:28 am Post subject: |
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| Brian Degulis wrote: | Well I don't know about loosening the bearing on a shifter with a 40MM axle either. Maybe one of the shifter guys can chime in.
If the problem is to much grip what about a harder compound tire?
Brian |
Why go harder on tire compound? You could easily tune the hop out and use that grip and go faster.
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T.J. Koyen
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Brian Degulis
Joined: 13 Aug 2012
Posts: 415
Location: United States, Florida,
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| Posted: Sun Nov 25, 2012 3:01 pm Post subject: |
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Maybe I need to understand exactly what's causing the hop. Is it the inside or outside rear wheel strugling to break free and make the turn? If so then would the thinking be more axle flex would help it break free or changing caster would help take weight off and help it break free?
Then either of those fixes might get rid of the hop and maintain good grip?
Another question. Is any loss of grip even a smooth slight slide in the rear a loss in overall time?
Brian |
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TJ Koyen
Joined: 03 Oct 2004
Posts: 1418
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| Posted: Sun Nov 25, 2012 7:29 pm Post subject: |
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| Brian Degulis wrote: | Maybe I need to understand exactly what's causing the hop. Is it the inside or outside rear wheel strugling to break free and make the turn? If so then would the thinking be more axle flex would help it break free or changing caster would help take weight off and help it break free?
Then either of those fixes might get rid of the hop and maintain good grip?
Another question. Is any loss of grip even a smooth slight slide in the rear a loss in overall time?
Brian |
The outside rear is being overloaded, and then breaking traction most likely. Then it grips, overloads, breaks, grips, overloads, breaks etc.
If you can slow down your rate of lift with a softer axle, you won't overload that outside tire and it won't break traction.
Changing caster will also take some of the weight jacking out, putting less force on the outside rear tire.
In regards to sliding, a slight slide is better than having both rears stuck to the track, but having NO slide with the inside rear slightly lifted is best. With a shifter, it's less of an issue because you've got power to pull you out of a slide.
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T.J. Koyen
OKTANE VISUAL - Custom Helmet Paint & Graphic Design
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Tyson Henry
Joined: 10 Aug 2011
Posts: 349
Location: United States, Texas, Arlington
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| Posted: Mon Nov 26, 2012 8:16 pm Post subject: |
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| Just try narrowing the front first. Easy to do and will tell you if the problem is caused by too much jacking. I had the same exact problem and it helped my hopping. |
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Brian Degulis
Joined: 13 Aug 2012
Posts: 415
Location: United States, Florida,
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| Posted: Tue Nov 27, 2012 5:42 am Post subject: |
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Thanks guys. Now I understand what's happening and have some things to try. I'll try the easy stuff first and post the results.
Brian |
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Oscar Aguilera
Joined: 18 Jul 2001
Posts: 1614
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| Posted: Tue Nov 27, 2012 8:23 pm Post subject: |
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| yea you dont want to loosen a third bearing with any shifter...the axle will bend and possibly crack. |
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Mike Unger
Joined: 18 Jul 2001
Posts: 308
Location: United States, Ohio,
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| Posted: Wed Nov 28, 2012 4:15 am Post subject: |
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I ran my Kosmic without the 3rd bearing even installed when I ran ICC and never cracked or broke an axle.
It will work. |
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Brian Degulis
Joined: 13 Aug 2012
Posts: 415
Location: United States, Florida,
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| Posted: Wed Nov 28, 2012 5:51 am Post subject: |
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The front hubs are already all the way in. So I'm left with loosening the bearing or adding castor. I also noticed my rear hubs are very long I wonder if shorter hubs would help it flex?
Brian |
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Paul Makarucha
Joined: 11 Jun 2002
Posts: 861
Location: United States, New Jersey,
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| Posted: Wed Nov 28, 2012 6:10 am Post subject: |
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Yes to shorter hubs
See if you can find a marking on the axle and find out just what axle is in there. Since you are maxed out on the front track width you might want to be thinking softer axle.
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