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Derek Mays
Joined: 28 Aug 2009
Posts: 96
Location: United States, Florida, Gainesville
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 Posted: Fri Jan 20, 2012 3:16 pm Post subject: Rear-tire wheel hop on hairpin corners |
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This is on a 2007 Tonykart Racer EVx chassis. What are a few quick (or quicker haha) changes that can be made during a test day to try and get the rear end to plant but not wheel hop mid-corner?
The front end seems to be working great, the rear end could still use some work on the faster corners but, most importantly the wheel-hop mid corner on hairpins is costing me a lot of time. I either hop it mid corner as if it is too fast, or I back the corner way up and slow down to much for it.
If not a chassis adjustment, perhaps a driving technique that i should try to counter this issue?
Thanks guys!
-Derek
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Peter Zambos
Joined: 22 Jun 2006
Posts: 538
Location: United States, Illinois, near Chicago
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| Posted: Fri Jan 20, 2012 4:32 pm Post subject: |
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| It is hopping because the inside rear is coming down hard or because the outside rear tire is breaking and regaining traction in quick succession? |
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TJ Koyen
Joined: 03 Oct 2004
Posts: 1413
Location: United States, Wisconsin, Sun Prairie
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| Posted: Fri Jan 20, 2012 5:50 pm Post subject: |
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It sounds like you are lacking rear stability and having a hard time finding that fine line where the rear is lifting the perfect amount. I usually find that if I'm having a hard time finding that fine line, it's because I'm too narrow or too stiff in the rear. Personally, I'd try and go softer on the axle, loosen the 3rd bearing, or widening the rear.
A rear hop can come from the opposite condition too, if you're too soft and the axle is rebounding. So if you're already soft in the rear, or going softer in the rear doesn't fix it, then try going stiffer.
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Brian Seward
Joined: 24 Aug 2006
Posts: 147
Location: United States, Indiana, Middletown
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| Posted: Fri Jan 20, 2012 6:34 pm Post subject: |
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| First make sure you are at or near max rear width. Typically with a Tonykart, going to a harder axle should cure the problem. I assume you have an N axle (standard) in the kart now? If so, going to an H should free it up. |
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Derek Mays
Joined: 28 Aug 2009
Posts: 96
Location: United States, Florida, Gainesville
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| Posted: Sat Jan 21, 2012 2:22 am Post subject: |
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Thanks guys. I'll be giving these a test when i head up to OGP soon. Hope one of them ends up solving one of my problem spots haha.
Derek
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al nunley
Joined: 13 Nov 2006
Posts: 3026
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| Posted: Sat Jan 21, 2012 7:22 am Post subject: |
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| Derek Mays wrote: | Thanks guys. I'll be giving these a test when i head up to OGP soon. Hope one of them ends up solving one of my problem spots haha.
Derek |
I've seen where low tire pressures can cause this and/or not enough seat bracing.
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TJ Koyen
Joined: 03 Oct 2004
Posts: 1413
Location: United States, Wisconsin, Sun Prairie
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| Posted: Sat Jan 21, 2012 12:00 pm Post subject: |
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| al nunley wrote: | | Derek Mays wrote: | Thanks guys. I'll be giving these a test when i head up to OGP soon. Hope one of them ends up solving one of my problem spots haha.
Derek |
I've seen where low tire pressures can cause this and/or not enough seat bracing. |
+1
Tire pressure being too low can give you the rebounding effect you'd get from a soft axle.
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T.J. Koyen
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Paul Makarucha
Joined: 11 Jun 2002
Posts: 858
Location: United States, New Jersey,
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| Posted: Sat Jan 21, 2012 1:00 pm Post subject: |
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| Brian Seward wrote: | | First make sure you are at or near max rear width. Typically with a Tonykart, going to a harder axle should cure the problem. I assume you have an N axle (standard) in the kart now? If so, going to an H should free it up. |
Listen to this.
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Shawn Campbell
Joined: 08 May 2004
Posts: 674
Location: United States, Wisconsin, Racine
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| Posted: Thu Feb 02, 2012 6:12 pm Post subject: |
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| Peter Zambos wrote: | | It is hopping because the inside rear is coming down hard or because the outside rear tire is breaking and regaining traction in quick succession? |
I agree with Peter here, you have to identify what type of hop you have because the way you fix the hop depends on what the chassis is doing.
One of the most common types of hop is the sidewall hop where the outside rear tire sticks hard to the track causing the sidewall to expand. Once it reaches its breaking point, the tire loses traction then begins to spring sideways which makes the entire kart hop. You would fix this problem by increasing the tire pressure or going to a softer wheel. Additionally, you would help the situation by reducing the grip on the outside wheels of the kart. Although you cannot physically change the amount of weight transfered onto that tire (because of physics), you can change the direction of the weight transfer to be less vertical and more horizontal. This helps the kart to allow the outside rear wheel to slide across the track surface rather than gripping it hard initially.
You do this by widening the rear out.
The other way you can help this problem would be to lower your seat back. It accomplishes the same thing as widening the rear track out by creating less downward force onto the tire during cornering.
Now, for the other hop, it would be caused by being too soft or too stiff. If the kart is too soft, the changes in the lateral forces cause too much flex which creates a rubber band effect and the kart will bounce around. If the chassis is too stiff, or has too much castor in the kart, it will lift the inside rear tire too much and slam it down causing the kart to hop as well. To fix this, you have to do what TJ said and determine if the kart is either too soft/not enough caster, or too stiff with too much caster.
Driving wise, if you put more turn into the steering wheel mid-corner, that can also cause the chassis to bind up and start springing. Its always best to try to use as little steering as possible to allow the chassis to drive free through the corner. If you aren't reducing your steering input mid corner, try turning in later and taking a later apex into the corner so that you can straighten the rest of the corner out.
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Ed Scott
Joined: 21 May 2006
Posts: 155
Location: United States, Oregon, medford
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| Posted: Fri Feb 10, 2012 2:47 pm Post subject: chassis |
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Good job Shawn. 
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George Vorrilas
Joined: 11 Feb 2007
Posts: 228
Location: United States, Massachusetts,
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| Posted: Fri Feb 10, 2012 4:33 pm Post subject: wheel hop |
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| Interested in Shawns statement of "going to a softer wheel". I recently posted a question regarding differences between Magnesium, Cast and spun aluminum.. Real curious to see what the thoughts are, differences in handling characteristics are between each.. many thanks |
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