Ride Height (front to rear difference) - Honda Prelude Forum

racinghonda · 10-31-2006, 03:52 AM

I have the Tanabe Sustec Pro S-S coilover kit in my car and after I had it installed (1yr ago) I got it corner weighted and the ride height set by the suspension place that sets up race/sports cars.

I decided to measure the ride height today and the front ride height measured at the front jacking points (left and right) were 135mm. But the rear height from the rear jacking points were 150mm. That is a 15mm forward rake.

The minimum legal ride height for cars in my Australian state is 100mm from the lowest point (header engine pipe).

Is that right? Should our cars have a forward rake? I have no idea what forward rake (if any) a stock Prelude has.

I am guessing that being a FWD car a forward rake would help it corner exit traction (due to weight transfer)?

Thoughts and comments please

paulyg · 10-31-2006, 07:09 AM

Most of us, when setting ride height use the center line of wheel to fender measurement. If that is accurate or not I have no idea. I have had several experienced autocrossers tell me they just get those heights even and forget it.

I don't know if those tabs are actually even. It's been so long since I've been on stock suspension but it always seemed like the front jack tabs were lower than the rear ones. By 6/10 of an inch (15mm)? No that much, that seems a little excessive.

marcucci · 10-31-2006, 07:58 AM

The tabs racinghonda is using should be more accurate than the body panels. Especially with some age. Regardless, if you are measuring to the body you are doing pretty good to get within 5-10mm IMHO.

A forward rake I would think would set you up for a front bias which should make the tail a little happier, though as you note, I have NO idea if the rear jack points are raked from the front at the factory- they may be mounted a little higher for appearance's sake. The car, when balanced, may be designed to have the appearance of a rake.

Moving to RR & A as you will get more feedback there.

mtbprelude · 10-31-2006, 09:37 AM

Forward rake = more weight on the nose.

There is no dynamic situation, except accelerating in a straight line, where you want that set up. When I actively campaigned my car (RIP) in STS, I had the rake set at 0. I believe when Drew campaigned his car in STX his rake was reduced similarly.

racinghonda · 10-31-2006, 01:44 PM

Quote:

Originally Posted by mtbprelude

Forward rake = more weight on the nose.

There is no dynamic situation, except accelerating in a straight line, where you want that set up. When I actively campaigned my car (RIP) in STS, I had the rake set at 0. I believe when Drew campaigned his car in STX his rake was reduced similarly.

Sorry to hear about your ride

Where is the rake measured from? Is it from the jacking tabs?

The 15mm rake isn't noticable to the eye, its only when you get under there with a measuring tape that you see the difference. The good news is that the difference in height from side to side is almost identical, with the right side 5mm higher which is probably to compensate for my weight in the driver's seat.

alvanderp · 10-31-2006, 05:23 PM

Quote:

Originally Posted by mtbprelude

I believe when Drew campaigned his car in STX his rake was reduced similarly.

I actually found the car handled best with a little forward rake. The measurements I took were from the center of the wheel arch on each corner. I had the fronts appx a half inch lower than the rear. When I had the measurements the same or less in the rear than the front it picked up a good bit of understeer.

All that said, I have no idea if these measurements are the same f/r on the stock suspension, I never measured a stock car. So its highly possible the same difference in measurements exists on the OE suspension.

racinghonda · 10-31-2006, 07:45 PM

Thanks for that. I rang the place that did the setup of my suspension and they said that they find that for FWD and cars like WRX, they set the rear a bit higher to improve front traction when exiting corners. He said that my driving style should include braking in a straight line as the rake can cause some oversteer.

I guess 15mm isn't much, but the roll centre will be a bit higher which would make the car feel on the nose.

ludehawk · 10-31-2006, 09:00 PM

when my sh was corner weighted (with driver and spare) and toe in racing spec (for me lol) it had an 8mm front rake.
rakes measured from the side jack points, AS the rear jack point (rear tow hook) is higher to keep it from being noticably visible below the bumper. with a lip or oe kit it's not noticable at all.

racinghonda · 10-31-2006, 09:49 PM

Yep, I measured my rake from the same side jack points. 15mm seems excessive . . . but then the 4th gen has a more even weight distribution to the 5th gen. 58%/42% vs 63%/37% of the 5th gen. I guess the guys doing the setting up would have taken this into account?

ludehawk · 10-31-2006, 11:01 PM

they don't care what the difference in preludes are... because the scales tell them what to do with YOUR car

racinghonda · 10-31-2006, 11:51 PM

^ I realise that, I just mean that the probable cause of mine running more rake is probably due to the natural weight distribution of the car.

mtbprelude · 11-01-2006, 11:15 AM

There is something about increasing rake in FWD car that seems theoretically wrong to me.

The only situation I see it as a feasible solution to a handling problem is the front spring rates are higher than the rear, and the rear of the car has reduced roll resistance (small/soft rear sway bar)

What are the spring rates in the Sustec Pro kit? Do you have a rear sway bar?

racinghonda · 11-01-2006, 03:01 PM

The Sustec Pro kit is 10kgmm front and 6kgmm rear and I have an adjustable 24mm rear sway bar.

mtbprelude · 11-03-2006, 09:55 AM

That is the reason you have rake dialed into your car to make it rotate with the softer springs in the rear.

The reason I find it theoretically wrong (but I know I am wrong) is that increasing load to gain traction moves you up the curve of diminishing returns. Or increasing load on a pair of tires, increases traction, but with each increase in load, the actual increase in traction is less than the previous one. At some point it falls the other way, where the increase in load exceeds what the tires are capable of handling, and you actually lose traction.

But an increase, is an increase, no matter what until you hit that point.