Euge

iTrader: (11)

nah, I got lucky. I'm sure if your car was setup right for carpet foam, you would have done well also. but........just to make it interesting.........how much $$ we talking?

SpeedTech

iTrader: (5)

Hi Guys,

Just a quick post, we should have some square products in stock tomorrow for the Pro4, website should be updated by tomorrow night

Steve Wang

TOEBSTER2

iTrader: (6)

Just picked up a pro 4. Anyone got a good starting point for a rubber set up besides the kit one. The kit one is probably a mod setup for outdoor.

Entropy

The kit setup is ideal for stock too. You prob just need to set the stabilizers and camber link height to tune in more or less steering to your liking.

farls3589

The kit one.LOL

TOEBSTER2

iTrader: (6)

ssshhhhhhhhhuuuuuuuuuuutttt up Farley, go to bed!

Spud_J

Hi Guys,

Thought some of you may find this interesting / useful. Its a very simple wheel rate table (wheel movement vs spring movement)using some of the commonly used springs. It's something I do for every car I get - just helps me to uderstand the actual wheel rates and you can then work out % front roll stiffness etc. It's not 100% accurate as it's not modeled but just measured out using a vernier......not too far out though!!!

Here is the table for the front

I can pm the excel version to anyone who would like it to add in different springs etc.

Spud_J

......and the table for the rear

Mossie

What do the wheel rate numbers actually mean? What does a higher wheel rate when compared to a lower wheel rate indicate?

Is there a web site that I can read about wheel rates?

Cheers,

Mossie

Spud_J

The wheel rate is the actual "spring" rate at the wheel. The wishbone acts as a lever on the damper & spring and this leverage changes depending on which tower and wishbone holes you use. So, a higher wheelrate is stiffer.

You can see from the table that on the front, a 17.5lb Xray white spring on hole 2 on the tower and 1 on the wishbone gives very nearly the same wheel rate as a 22.5lb Xray dark blue spring on hole 1 on the tower and hole 2 on the wishbone, this is because ther is more leverage acting upon it in this configuration.

Now, there are many other factors like progressive rate changes depending on the damper angle, dynamic loads etc but this table is just a very simple reference so you can compare one spring and location to another and relate it to the wheel rate.

I dont know of any specific websites mossie but I'm sure a search on google will take you to plenty. Or if you really want to get seriously technical buy yourself a copy of the book "Race Car Vehicle Dynamics" by Milliken & Milliken........be prepared to be baffled though!!!!!

JohnB

iTrader: (1)

VERY NICE Spud!! Well done. We appreciate it.

Mossie

Thanks spud. I understand now!

Cheers,

Mossie

Spud_J

Hey no probs, glad you like it. Just remember that this does not take into account roll bars etc, just purely the main spring. I use these figures in my setup sheet which then tells me the % front roll stifness.

You calculate this by:

Front wheel rate / (front + Rear wheel rate)*(100)

I.E, say the springs and positions you are using give the following wheel rates...

Front wheel rate = 180g/mm
Rear wheel rate = 165g/mm

So

180 / (180+150) = 0.545 * 100 = 54.5%

That tells you that the front of the car is 54.5% of the total cars roll stiffness - simply the front is slightly stiffer than the rear.

In an absolutely ideal world, with good weight distribution, sensible roll centers, CofG etc (*can opening, worms everywhere!!!!*) around 50% front should equal a near neutral car, less than 50% front should equal lots of front end and greater than 50% front should equal gradual push or more rear grip.

I like a very aggressive car, so, depending on the tyres I usually start around 46 - 48% front and fine tune with damper oil, roll bars, ride hight etc.....

sturla

How do you calculate the total ammount of wheel rate?

Spud_J

Sturla,

Im not 100% sure what you mean by total wheel rate but if you run a HPI Pro4 then they are already calculated in my table!

If not, a simple way is to take the spring off and put the damper back in place. Next measure with a vernier the length of the damper rod - say between the ballcup and the body. next move the upright up exactly 5mm, measured at the centerline of where the wheel would sit (hudy droop blocks work well) and measure the damper rod again.

Say if your first measurement was 8mm and your second measurement was 5mm that then means that for your wheel to move 5mm the spring has only moved 3mm. Then divide 5 by 3 which = 1.66

This figure of 1.66 is the motion ratio of wheel to spring.

Them divide your sring rate - say 30lb by 1.66 that then gives you a wheel rate of 18.07lb/in or 322.69g/mm if you prefer metric.

You can repeat this with all the variations of damper position and come up with a table for your specific car

Hope that helps