Originally Posted by MikeXray

Unfourtunately rubber tire TC's have proven flex to be an integral, and in some cases essential to a well performing car. If you look at many of the changes the top cars are making these days they revolve around flex. I can say that running 4 screws vs 6 in the rear part of the top deck of my T3 yeilds a different change than what can be achieved with a spring, link or droop change.

Originally Posted by wingracer

Chassis flex only seems to be desirable when grip is at a premium. Looking at real world race cars, F1 cars with tons of grip run super stiff chassis while a dirt oval car is intentionally much more flexible. When TC ran on foam, they had fairly stiff chassis but with rubber, softer seems to be better.

Of course, a lot of the reason for this has nothing to do with ultimate performance. In theory, a stiff chassis should always be better but in our RC world, it is virtually impossible to get everything exactly right. We just don't have the fine adjustability, hyper accurate set-up tools and proper shocks to get a setup spot on. Plus, very few RC racers have the knowledge and experience of a professional race engineer. We also don't have a butt in the seat to give precise feedback on what the car is really doing or telemetry to give us data. This is where flex comes in big. Flex disguises other set-up problems. A flexible car has a HUGE sweet spot it will work in set-up wise. It will also be less effected by changes in condition such as weather, grip level, tire type and condition, etc. So a flexible car will still work reasonably well with a sub-optimal set-up. It will NEVER work as well as a stiff car with a PERFECT set-up but with all the limitations I described, a perfect set-up is virtually impossible for us to ever attain.

Originally Posted by roosterreagan

This whole idea has bothered me since day 1 of learning about rc racing. Millions, perhaps billions, of dollars is spent in the search for torsional rigidity, both on track and the street. I've asked high level rc drivers why do we purposely "add" or account for chassis flex? They don't know, like a lot of other things in rc they "just do it, it's how it's been forever". My opinion is its lazy. Something kind of works for someone so that's it, no discussion just follow everyone else, cuz that's how it is. Period. Bull, make the chassis stiff, and tune your suspension, why else have all this great suspension technology? Why not just make it a 1/10 pan car if you're going to negate a complicated and infinitely adjustable chassis system?! I feel similar regarding gluing the outer sidewall of tires to "cure" traction roll but that's another discussion. Just my 2 cents. Btw, thanks Bob for all your hard work, your program has been the funnest thing I've purchased related to rc cars in a while.

Originally Posted by Skiddins

A large amount of F1 suspension travel is in the sidewall of the tyres, if I recall it's a least 50%



'Normal' road cars have chassis flex built in as it improves the ride quality etc. For racing it's a different story.
I think part of the issue is that the laws of physics don't scale, they are the same whatever, and our tiny cars accelerate, corner and reach speeds (in comparison to scale) far greater than their full size equivalents.
It's the same when all slop etc is removed from suspension components in our cars, it makes them almost undrivable.

Originally Posted by roosterreagan

This whole idea has bothered me since day 1 of learning about rc racing. Millions, perhaps billions, of dollars is spent in the search for torsional rigidity, both on track and the street. I've asked high level rc drivers why do we purposely "add" or account for chassis flex? They don't know, like a lot of other things in rc they "just do it, it's how it's been forever". My opinion is its lazy. Something kind of works for someone so that's it, no discussion just follow everyone else, cuz that's how it is. Period. Bull, make the chassis stiff, and tune your suspension, why else have all this great suspension technology? Why not just make it a 1/10 pan car if you're going to negate a complicated and infinitely adjustable chassis system?!

Originally Posted by daleburr

I've seen similar posts on here before, but I'm yet to see a post from someone who has made a rigid chassis and gone any quicker

The cars haven't always been flexible. They started out rigid, following full-scale vehicle dynamics. Over the years they have evolved, as chassis flex gives more grip, better bump handling and a wider setup window.

Our cars are now about 500 times lighter than the lightest full-size race car. Yet they go at about one third the speed (mod TC >70mph). And they do it with much simpler suspension, tyres and aerodynamics. And they encounter curbs that come up to their axles, and bumps that would destroy a full-size car if scaled up.

When you put all that together, it's amazing the cars get round the track at all. So they need a lot of help, and flex is one of the things that helps. It keeps all 4 tyres in contact with the track, without resulting in any extra pitch or roll.

Give an old TC3 a go. The suspension geometry is similar to a modern car, but the chassis is ultra-stiff. See how it compares to a modern car.

Originally Posted by roosterreagan

^ thank you for that, that's the first time I've personally seen someone actually explain it in a thoughtful way. It makes sense when put that way, we race to have fun and just so happens winning is very much more fun than losing, why not use every means at your disposal to make driving easier. I get that, I do. Just seems, to me at least, "flex" is an unknown quantity, whereas all the components meant to do that job are of known values and predictable...
But I guess if you've done the trial and error on adding or omitting certain chassis fasteners and figured out how it effects handling on the track what's the difference, it's a tuning aid like anything else I reckon.