Effect of Chassis Rake / Ride Height?

[Tom Grossmann]

As the title says I'm not 100% on the effects of rake//ride height on the rear suspension on my Novakar so I thought it wise to ask here.

The car is a the 3rd Novakar built; for autocross I set the rear ride height 1.5" higher than the front. For the road racing I used the notes that came with the car and set the rear 1/2" higher than the front.

The extra rake seems to help the car turn at autocross but I'll fully admit that I do not know that it actually helps as I also changed the toe at the same time. I'm running 3/16" toe out for autocross vs 1/16" toe in for road racing.

I'm assuming the extra ride height is changing the rear suspension geometry enough to have a positive effect on the handling for autocross.

So my basic question is the 1" change in ride really doing anything or am I whizzing up a rope?

Any and all advice welcome.

[Garey Guzman]

See attached. Great document to study!

[t walgamuth]

Raising the rear will cause it to have a little less adhesion, so if your car is pushing, raising the rear may help.

The toe out will help the front of the car bite into the turn. I have not touched my toe yet in my new to me car (Groot) as the car's balance is presently perfect. The car does have the modifications to the front to get full ackerman (I am not sure if that is a correct use of the word).

I did raise the rear about 1/4" when I first got the car.

[Jnovak]

As the title says I'm not 100% on the effects of rake//ride height on the rear suspension on my Novakar so I thought it wise to ask here.

The car is a the 3rd Novakar built; for autocross I set the rear ride height 1.5" higher than the front. For the road racing I used the notes that came with the car and set the rear 1/2" higher than the front.

The extra rake seems to help the car turn at autocross but I'll fully admit that I do not know that it actually helps as I also changed the toe at the same time. I'm running 3/16" toe out for autocross vs 1/16" toe in for road racing.

I'm assuming the extra ride height is changing the rear suspension geometry enough to have a positive effect on the handling for autocross.

So my basic question is the 1" change in ride really doing anything or am I whizzing up a rope?

Any and all advice welcome.

Wow, great questions Tom. I need to think about this a bit as I have not worked on these cars for about 30 years!

Does it still have the center post rear suspension? If so then that's good for solo as raising the rear then raises the rear RC. The down side is that this increases the rear roll understeer at the same time but easy fix imo.

What is your min weight?

What engine?

One of those cars held the lap record at Waterford Hills for over 15 years!

Who was the original owner?

They were very good road racing cars in the day. One of the first of that 6 car build was strictly a solo car and won MANY solo events with FTD!

[Tom Grossmann]

Jay the car does have the center post suspension, it's still running the AMW engine, it weighs 778lbs with me in it and Larry Dupuis was the original owner. You drove 2 races in the car, the Golden Harvest & The Coca Cola 100 and after that Larry ran it at Waterford Hills.

I do have a Rotax 494 waiting to go in but I said I would run the AMW motor to it goes kablamo, so for the moment the AMW stays.

I believe the weight minimum for a 73" wheelbase car is 775lbs.

While the car will spend most of it's time as an autocross car I intend to do two vintage races a year so I'm trying keep the set up changes to a minimum between events. At the moment the change I've made was rear ride height, toe and gearing.

[Richard-6]

See attached. Great document to study!

Sorry but that PDF looks more like a list than a guide on how to set up a car for road racing.

Also did you notice that this is the F500 discussion tread? No shocks, and no anti-sway bars to adjust.

Also really hard to adjust the rear wheel toe in on a F500 car.

Richard

[EricP]

Sorry but that PDF looks more like a list than a guide on how to set up a car for road racing.

Also did you notice that this is the F500 discussion tread? No shocks, and no anti-sway bars to adjust.

Also really hard to adjust the rear wheel toe in on a F500 car.

Richard
reddevilsix@msn.com

I believe that PDF was a PowerPoint from a presentation (a very good one I hear) and not intended to be a stand alone document.

[Richard-6]

Here are some books on the subject. Unfortunately, they are not F500 specific.

Winning - the race driver handbook by George Anderson
While the book is a little dated, the information is still current.
https://www.amazon.com/Winning-Drive.../dp/0879387769


You also may want to invest in the Carroll Shelby book, Tune to win.
https://www.pegasusautoracing.com/pr...EaAo34EALw_wcB


And also the companion book, Prepare to Win also from Carroll Shelby. Again these books are somewhat dated, but the information is still valid.


Richard

[Garey Guzman]

Sorry but that PDF looks more like a list than a guide on how to set up a car for road racing.

I guess it's possible to have that perspective. But the last time I autocrossed, there were left and right turns and the basics principles of handling still applied.

Also did you notice that this is the F500 discussion tread? No shocks, and no anti-sway bars to adjust.

Also really hard to adjust the rear wheel toe in on a F500 car.

Yes, I noticed that too but the F500 parts can be viewed to act similarly to conventional suspension. Not everything there applies to FF or FA either but the principles still apply. I was just trying to offer this as background for a new guy. Personally, it helps me to understand the REASON I'm changing ride height, rake, etc., rather than just ask someone to tell me what to do.

YMMV

[Tom Grossmann]

Gary I appreciated the link; when I had the D-Sports Racer I learned a lot about dampers and alignment settings but obviously only half of that applies to F500. I've got all of the Carroll Smtih books, while I have a basic understanding of roll center effects on the car the Novakar has a pretty unique rear suspension set up, which I do not fully understand. This post was my roundabout way of trying to find out the reason why a certain amount of rake has X effect on the car. There are some really talented engineers on here who are always willing to share their knowledge.

[Jnovak]

Tom.
1. Raising the rear ride height on those very simple cars 1.5 inches will raise the rear roll center very close to the same amount thus freeing the car up too.

There is a downside which is that this change also changes the rear roll steer from very slight roll understeer to some level of roll oversteer. I never tried that much change but the car liked a 1/2" increase in rear ride height.

Now the roll steer can be fixed but will require some minor bracket mods.

More info as you need it. Just ask and I will try to help

[Tom Grossmann]

Jay that was the information I was looking for. I used Larry's set up notes that came with the car for track set up and that seems to be pretty neutral. When I first got the car I took it to my first autocross with the Waterford Hills set up and as one would expect it had terminal understeer. I think it was Jeff Colgrove who suggested putting more rake in the car.

The autocross set up I've been using is very edgy, in fact I had to dial it back when my son as he ended to loop the car. My next autocross isn't until January 19th but for that event I think I'll try using 1" of rake as a happy medium.

Jay thanks again for answering my questions, especially considering you built the car 33 years ago, I'm sure when you built it you never imagined someone would be taking it vintage racing.

[Jnovak]

Tom, please post a side view picture of the trailing arms so that i can make some suggestions on mods

What tires are you using?

Are you using the original black rubbers that were on the car way back?

I need lots of pictures

[Richard-6]

Tom and other members

Attached are two documents that I used when I was racing to help me at home and at the track.

Please note that the extensions are .pdf, however they are not real PDF documents. Turns out one can not attach .XLS or .DOC documents.

Chassis setup.pdf

Race_log1.pdf

Down load these files to your desktop, change the extension as noted below:

Race_log1.doc

Chassis setup.xls

You should now be able to open these files. If you have trouble, post it here on this thread.

Please feel free to use and modify as you like.

Richard

[sathorp]

I do have a Rotax 494 waiting to go in but I said I would run the AMW motor to it goes kablamo, so for the moment the AMW stays.

Tom, every snowmobile mechanic and engine builder that I respect and trust has told me Rotax 494 is a bulletproof engine package. I currently have 8 fully complete Rotax 494 Engines in my garage right now, another one possible on the way, I know where there are 2 more, plus I have spare jugs, heads, cranks, etc. Low-Cost parts are available for the Rotax 494 Engines. The SCCA Vintage Racers can keep out of production engines from the 60’s & 70’s running at low cost for 50 to 60 years. I guess some people just have no idea how to keep cost down! All the Rotax 494 engines I’ve purchased as fully complete engine packages for between $400-$600 from multiple sources. None of the engines I’ve purchased where built from separate parts or components.

I wish you a lot success when you convert to the 494 Engine. I think you’ll be very happy with the Rotax 494 Engine.

[Tom Grossmann]

Jay I'm using the standard Hoosier 18 X 7.5 R25B. The pucks on the car now are black rubber type (they car came with a selection that appeared to be fresh) I will try and get some pictures up in the next day or so.

[Tom Grossmann]

@Sathorp totally understood on the 494; I paid $600 for the one I have and it even came with a primary and secondary clutch. The changes to fit the 494 are pretty minor but my off season is actually June through August so I'd prefer to do the swap then. I am looking forward to the extra 10-15hp. My schedule is pretty limited as I only do 8 autocrosses and two vintage races a year so I expect the 494 to go several seasons.

[Richard-6]

Merry Christmas to everyone.




Richard

[sathorp]

Merry Christmas to everyone.




Richard

Happy Holiday to you also!!!