Stability / Handling
My Blade engined, book car seems to be unstable at speeds of over 60 mph. It’s got the book caster – all of it, 5.5 degrees I seem to recal, a live
axle and a quick rack fitted.
It tends to get into a bit of a “tank slapper” that feels like it could be the rear tyre side walls flexing / moving around, but I note from an
earlier thread that the caster angle seems to be the usual suspect.
So what’s the consensus for caster angle and are there any other areas that I should look at?
Check Tyre pressures, Toe-in and corner weights.
Toe-in is often the cause (mine needs sorting too!). One clue - does it get really twitchy under hard braking? If so, get the toe-in checked -
presuming that your tyres aren't excessively soft (what pressure are you using?).
David
Rear wheels with no toe in will give you unstable handling at speed. Try a 1/4 or 1/2 degree toe in on each rear wheel.
I experimented on race cars.
With zero toe on the rears, the car was slightly quicker, but it meant that the rear end was really twitchy on long straights.
It sounds like your castor is enough.
I am lucky in that I bought a 4 wheel alignment machine from ebay. It makes all the difference to set the car up this way.
If you can, invest in a suspension tune up.
[Edited on 6/6/2006 by nitram38]
Do you mean its unstable on, lets say a motorway at 60mph or a country lane with bumps and curves etc?
You could be suffering from bump steer
[Edited on 6/6/06 by Mad Dave]
Ok
The corner weights are all OK
The tyre pressures are all at 20psi.
I have between 2 to 4 mm of toe in.
Bump steer is very very small if any at all – special steering rack.
It's on straight, bends are OK.
Any ideas? How stable should it be?
quote:
Originally posted by nitram38
Rear wheels with no toe in will give you unstable handling at speed. Try a 1/4 or 1/2 degree toe in on each rear wheel.
These cars do feel 'edgy and nervous' when compared against a normal tin-top, especially when you have quick rack.
When I've been driving the 7 for a while, and got settled into it, afterwards I find the tin-top very stodgy!
quote:
Originally posted by wildchild
quote:
Originally posted by nitram38
Rear wheels with no toe in will give you unstable handling at speed. Try a 1/4 or 1/2 degree toe in on each rear wheel.
I'll be impressed if he can manage this on a live axle car!
Hi perfectly possible to put toe and camber on a live axle . Standard on all our cars.
cheers matt