Rain race setups

[Joe Vancura]

I have some idea of rain race setups but not a lot of rain experience.I would like any opinions of how to set up the chassis,and would like to know the physics of what we are doing.The more detail the better. Thanks in advance.

[John Denman]

http://www.ekartingnews.com/tech/010423techcc3.html

[Patrick Hubbell]

quote:

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Originally posted by Joe Vancura:
I have some idea of rain race setups but not a lot of rain experience.I would like any opinions of how to set up the chassis,and would like to know the physics of what we are doing.The more detail the better. Thanks in advance.

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Some things you can do for rain are:

1.widen the front track as much as possible. This will enhance the grip on the front of the kart. The caster affect is increased as is the weight jacking affect helping to transfer more weight to the outside wheels and lift the inside rear.

2.Raise the seat height or put a cusion in the seat to lift the center of gravity. This will also help transfer more weight.

3.Increase the toe out of the front wheels. This will help with turn in. A 1/4" would be the max here.

4. Use a late apex driving line and stay off the dry weather line. Roll the throttle on. Add two teeth to the rear sprocket.

5. Make sure you have dry clothes in the trailer/truck.

[Roy Harris]

Patrick has a good list going. I would also say if the corners have any banking the outside line will be drier. If you are driving a clutch kart it helps the clutch to raise the stall speed. Some drivers will tape the front of the side pods to keep water out and I have seen them drill holes in the bottom of the seat to drain water.
As for changing the toe out some karts have more than one hole for the tie rod to connect to on the spindle and you just have to move it to another hole for a quick toe change. And one thing I learned the hard way is to run higher pressure in your rain tires than in your slicks. I run 20 - 24 pounds in my Dunlops.

[Mark Dismore Jr]

quote:

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Originally posted by Patrick Hubbell:


4. Add two teeth to the rear sprocket.

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Remember that rain tires are usually a lot smaller diameter then slicks, so make sure you gear accordingly. You might change your gear and not even know it.

Mark

[Brian Kay]

One thing is guarenteed with ANY chassis in the rain - UNDERSTEER.

Here's what I've done with shifters, and Rotax Max to really get them hooked up.

If the kart has the sliding, 40mm front hubs:

**Put the front hubs on the rear

**Put the rear hubs on the front (100mm hubs)

This is a huge plus. Try to get the kart "square" On shifters, look for a front track around 48", and a rear trac width of 48-49"

**Lower rear ride height

**Raise front ride height

**Full caster

**Tune brake bias for more front brake

**1/16" of positive camber is a good thing (measured on toe plates)

**1/8" toe out.

**Loosen all stressed chassis members - bumpers, nerfs, floorpan.

**Tire psi 17-22 lbs (rains)

There's more, but usually there's not enough time to convert over to a FULL rain set-up. You have to prioritize! I'd say THE MOST critical move is getting the kart square by swapping Fr / Rr hubs. Take it from there if time permits.

It's a good idea to have a pair of cut down axle keys ready to go - They'll allow you to slide the hubs in on the rear that much further.

Good luck!!

Brian Kay - www.T2racekarts.com

[Ted Pyle]

Two posts in two days, I'm on a roll.
I mark my tie rods with Magic marker and then rotate them half a turn for toe out. This way, if it dries I can go back to my original dry setup with no problem. Moving the seat is a pain, but my driver has always been light, so I can move weight up higher quite easily. I also have found that high tire pressure USUALLY works, but sometimes not. If your track has a hot pit and it is the usual hectic morning practice, I send my driver out at a high pressure (20psi), have him do some laps,and then have him come in and start to bring the pressure down. Fronts out full is a given, but the rears have a limit to how much you can bring them in. In my experience, a 55" wide shifter should only be brought into about 49"-50". Shifter drivers should short shift to keep rear tires from spinning, and only brake in a straight line. Modulate the throttle and have fun. Don't forget when you get home your job is not done. Bearings, motor and anything that can corrode/rust will need to be taken care of. Be ready for about a one hour chassis cleanup (always the driver's job!)

[Patrick Hubbell]

quote:

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Originally posted by Mark Dismore Jr:


Remember that rain tires are usually a lot smaller diameter then slicks, so make sure you gear accordingly. You might change your gear and not even know it.

Mark

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They are also lighter. I know, I got DQ'd after qualifying once. I was 2 or 3 lbs. light. Smaller(the rears were 7.10's to start with) and the rains are 6.0" wide.

[stmichael22]

Rain Racing:
your best bet would be to get on one of the new Dameon RT karts. I've seen one testing rain setup, and they are wicked. I've never seen a kart able to pick up an inside rear tyre in the rain. If you can get one of those chassis, thats the way to go for rain(dry set up too). They are near impossible to get, from what i'm told, and only the top pro drivers are getting a hold of them. If you are racing against one in the rain you might as well just drop out of the event, they are insane. best wishes with your chassis.

[Drew Cleaver]

quote:

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Originally posted by Michael Johnson:
I've never seen a kart able to pick up an inside rear tyre in the rain.

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My physics/genius brother was telling me that it should be easier in the rain, something about how the front wheels are far out it increases the jacking and what not. I'll just have to ask him when he gets in town tomorrow.

[Joe Vancura]

Thanks for the tips.I knew some of this already,and I learned some new tricks.Karts are Brava 125 and Brava 1 Rotax.Our club races do not run in the rain.We do run on a wet track with slicks only,as long as it is not raining.I usually narrow the rear all the way in,slap some caster in,and widen the front out.What should I do for tire pressures for YGC/MG- yellow type tires?From watching the WKA rain races you can really see the importance of kart setup.Dry races separate karts by tenths-wet races by seconds,all with the same motors and drivers.P.S. I learned about drilling drain holes in the seat the hard way!

[ January 25, 2002: Message edited by: Joe Vancura ]

[John Learmonth]

quote:

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Originally posted by Drew Cleaver:


My physics/genius brother was telling me that it should be easier in the rain, something about how the front wheels are far out it increases the jacking and what not. I'll just have to ask him when he gets in town tomorrow.

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With a lot of weight jacking (scrub radius and caster) and a narrower rear track it will be easier to jack weight at turn-in, but KEEPING the IR unloaded later in the corner will be more difficult because horizontal acceleration will be lower with less grip. You really need 'dynamic' weight transfer after turn-in.

[Mike Beeles]

We have had good success adding some weight to the front center, and we follow most of the basic rule of rain as listed above. the best set-up is to play in the rain, but beware, dry that kart, I repeat, make sure you dry the kart, every piece of it.

[John Denman]

After looking over the responses, I did not notice any references to wheels, so I will ask;

Given a choice of Douglas (soft) wheels, cast (stiff) wheels, would it make a difference which ones were used to mount the rains on?

It would seem that stiff fronts and soft rears would be the best choice. Can anyone confirm this?

[Patrick Hubbell]

quote:

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Originally posted by John Denman:
After looking over the responses, I did not notice any references to wheels, so I will ask;

Given a choice of Douglas (soft) wheels, cast (stiff) wheels, would it make a difference which ones were used to mount the rains on?

Stiffer wheels will add grip.
It would seem that stiff fronts and soft rears would be the best choice. Can anyone confirm this?

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