1881 replies to this topic

[Jammy]

Ahhh, I'm petty sure I understand, in a distant way is it kind of like a pendulum, the more weight on one end the more it swings around, so the trick is to get a balance.

[R1minimagic]

Think of it as being like a trailer which is pretty light compared to the wheels and suspension.

If it has a car on it then it is nice and smooth over the bumps. If it has no car on it then it is bouncing around like a b***ard!!!

[Jammy]

But then that suggests a heavier car is better for getting rid of bump steer?


Edit, maybe a mod should/could move these post about bump steer to there own topic?

[pete]

Ade
You got PM

[pete]

Dale
Off topic a bit but where do you have your temp sender unit mounted. Fitted ours by the thermostat housing but am now thinking that won't give a true reading as the fan sensor is in the rad. They read about 100degrees c before the fan cuts in. Mine even went to 120 when I tried it last night.

Pete

[R1minimagic]

Its a bit tricky to explain this.... Can anyone help me out??


A heavier car suffers less from unsprung weight compared to a lighter car with the same suspension so it should be more composed over bumpy roads. ie the suspension can be moving around a lot on a heavier car but it doesn't really effect the car body very much and the body height stays fairly constant to the ground..

The bumpsteer is more to do with the suspension movement which you can still have a lot of on a heavy car with soft suspension ie it will suffer from bumpsteer

Am I making any sense or just talking complete nonsense???

[R1minimagic]

Pete

I originally had mine fitted on the top radiator hose but have now fitted it on the bottom one so that it is always in the water. It doesn't make any difference to the temperature readout on mine as long as the level is ok so the water circulation must be pretty good.

[markrally]

It's not fair
I can't download the clip to see what it looked like from outside. From inside the car it was scary to say the least. Damn plastic toy kept bouncing about every time it hit a bump
It'll be fun watching Chris at z-cars give it a quick road test on Monday.

Pete, can you get the settings for me as i do my own set-up on my mates 4-wheel alingnment kit where he works, It will be interesting to see what angles chris sets em up at!!!!

Cheers Mark :wales:

Ps i cant see the clip either but i can hear it!!!!!!!!

[Ade]

I think the settings for Pete and mine will be a bit different from standard settings for minis..... :fear:

[ryan69]

oooh i love the sound of it ade, its awesome :grin:

[dean_chad]

oi oi bit off subject but do the front hubs and disks come in the z-cars kit? just bought a shell!

did any of you lads re-wire you own looms? how much did it set you back to get yours altered?

whats the main problem you have all been having?

sorry bout thread jacking!

[MikeS]

Well I finally registered Ade. Firstly I must say congratulations what a very nice job you (and Pete) seem to have done there. Look forward to seeing it (them) the flesh when your ready and want a coffee! You know where to find me.

Bump-steer, this interested me. Firstly bump-steer is a function of geometry issues not weight. If you make the car lighter without lowering the relevant spring rates then bump steer is not going to automatically result, a rather "jouncy" ride yes, since the springs are now over rated, and over damped, for their requirement, but bump steer - sorry, not at all.

Firstly can I ask who and why the phrase-bump steer is being used at all? I suspect that it mostly down to using a much wider profile/low ratio tyre which is naturally going to be more sensitive to road irregularities, coupled with a probably increased offset in the steering which just magnifies these deflections. I would be very interested in the dimensions of the rim, width, off-set, and hub and kingpin arrangement to see what has happened to the steering offset, I suspect this is the most likely problem. The greater the offset, the greater the torque reaction causes the wheels to deviate from their original angle and the greater the feedback into the steering wheel.

The steering geometry on the mini is pretty sound and it will take much more than lowering it by 40mm to result in enough error in the steering arcs to cause it.

[Dick Dastardly]

Here's a decent article on bump steer.....

Click

Have fun!

D.D.

[R1minimagic]

I dont think there is any one single factor that is totally responsible for these bike engined minis feeling twitchy when coming off the power. So much has been changed with these minis that the effects are cumulative.

The combination of the increased track, wider tyres, lighter car, unoptimised spring/damper rates, lowered suspension and maybe some more bumpsteer magnify the effects. The coil spring setup (required due to loss of engine) is also not ideal when you lower the front of a mini unless you change the geometry of the spring/damper unit as they tend to rock inwards at the bottom due to the obtuse inclination of the top suspension arm.

They can be made to handle very well, it just takes time to optimise all these things as I am finding out!

[pete]

Dean chad
Front hubs don't come in the kit. Most of us are using metro vented discs and 4 pot calipers on mini hubs. Adjustable bottom arms and tie bars. Myself and Ade sent the bike looms to Chris to be modified because we were told that if you got it wrong the ecu would go into safe mode and we would be stuck. After getting them back we realised we could have done them ourselves as the yamaha manual tells you how to reset the ecu if you get it wrong. The rest of the loom I made for both cars. Not pretty but they both work.


Mike
Nice to hear from you. I think the biggest problem with Ade's car is that the wheels don't all point in the same direction. All camber,castor and toe settings have been guessed untill we get them up to z-cars on Monday. Won't be putting mine on the road this year but will definately catch up with you at next years STCC. Might even let you have a drive :grin:

Dale
Is your temp sender at the front by the rad or at the back by the engine.

Mark rally
Will get the settings for you although as Ade said, they may be different. A friend had his set up last week by Chris so I will ask him if he knows what it was set to.
Pete