Narrowing Rear Track

Chris M Johnson · Joined: 14 Oct 2005 Posts: 568

Lots of good advice in this thread

Pete Schaible · Posted: Wed May 09, 2012 7:28 pm Post subject:

Tires have 3 events on them so fairly new for autocross. I don't think the seat is laid back anymore than most but this is what it looks like.

Tom Reynolds · Posted: Wed May 09, 2012 8:49 pm Post subject:

I had my seat like that and it was constantly stated it was too far forward. You look like you could be around my height (5'8") but I managed to learn to drive it with it farther rear.

Brian Garfield · Posted: Wed May 09, 2012 8:58 pm Post subject:

Seat position looks good to me.

"4th rail in but no bolts in it"

Bolt that bitch down... You need to go full stiff on the chassis and see what it does. Tighten up everything in the chassis.

Also, and I hate to say this, there are some chassis that will NEVER have the grip for what we do, they're not designed for it since they're designed for a track. That said, I wouldn't give up.

After you've tried to trouble shoot this, consider narrowing the front significantly, adding a little push on turn in will make the rear more friendly in the quick transitions. I drove mine with a hair of push on turn in so I could drive the piss out of it without it snapping.

Brian

Christian Hubbell · Posted: Wed May 09, 2012 10:27 pm Post subject:

You could make all the changes in the world and it may just come down to driving style so take everyones info with a grain of salt.

Now if it were me I'd drop the seat 1/2" below the frame, bring it forward a 1/2" and tip it back a few degrees. All this is going to take weight off the rear wheels because lets face it, they are probably being overworked. You are going to run into problems though like your seat struts might now be too long. Drifting is always fun though.

Joe Ricard · Posted: Thu May 10, 2012 6:05 am Post subject:

Pete, what ICC motor is that?
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Pete Schaible · Posted: Thu May 10, 2012 12:40 pm Post subject:

Motor is a TM K9B. I will put the bolts in for the 4th rail and I may put some foam in the bottom of the seat to see what it does before I move it. Unfortunately I don't have another autocross for a month so I won't know how effective the changes are for a while.

Pete Schaible · Posted: Fri May 11, 2012 3:20 pm Post subject:

Well it turns out what I though was a hard axle may not be. So I know my next step. Is there any axle out there that has proven itself to work well. It seems like the Soft Medium Hard rating is so subjective and wall thickness varies among manufacturers.

Christian Hubbell · Posted: Fri May 11, 2012 7:23 pm Post subject:

Assuming they are all chromoly (which they should be) the thickness and length will be the only factor dictating the stiffness. I saw some ones for sale in the parts section here. I know PKT sells shorter axels too which may help you out. Still, moving the seat is free and probably less work. I once heard a guy on here saying if your seat doesn't look like swiss cheese you're not doing it right.

Tom Barth · Posted: Sat May 12, 2012 4:53 pm Post subject:

Look at Birel axle chart. It rates axles by diameter, length, and wall. There are several axles with same length, wall and diameter but have a different modulus of elasticity, measured in kg. The kg is etched on the axle. In the 50mm size there are (5) 1000mm and (5) 1040mm models.

Rear axle and tire pressure are major chassis tuning components.
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Tom Barth
http://www.greenflagkarting.com/

Power is good...more power is better... too much power is just right!

Vernon Head · Posted: Sat May 12, 2012 5:41 pm Post subject:

Pete:

You need to find out how hard your axle is. Whoever made it has a chart, like Tom was talking about. Then determine if you can where the axle is on the scale. If you are extremely loose you may have a soft axle and if that's the case I would go to a harder axle. A soft axle can really make you loose if you aren't on a grippy track, so loose that struts, hubs and seat position won't work.

Pete Schaible · Posted: Mon May 14, 2012 5:22 pm Post subject:

Measuring everything on this axle It looks to be a Shockwave axle. 7mm keyway holes and 34mm center to center spacing. 2.3mm wall thickness. If this is correct then it is a hard axle. How does this axle stand up to other hard axles or even a very hard axle? Anyone have experience with them?

Vernon Head · Posted: Mon May 14, 2012 5:59 pm Post subject:

I believe that Shockwave stamped an "S", an "M" or an "H" in the middle of the axle for Soft, Medium and Hard. Look for one of those letters and that will tell you what you have.

Pete Schaible · Posted: Mon May 14, 2012 6:12 pm Post subject:

Found a very faint H in the middle but definitely there. So its a hard Shockwave.

Vernon Head · Posted: Mon May 14, 2012 6:39 pm Post subject:

So you have a hard axle and that is probably not the problem.