1881 replies to this topic

[pete]

Is it bump steering badly at the moment?

Definate understatement. Apparrently the way a mini subframe is set it has a certain amount of bumpsteer built into it.Lowering it and adding big wheels makes it worse. Hopefully next Monday will cure this.

[The Matt]

I guess it won't help not having much weight up front (apart form Ade :tongue: )

[R1minimagic]

I am not sure exactly how much bump steer minis actually have but if you read Bill Sollis's book he reckons that there is no discernible difference between a car set up with a lot of bumpsteer to one with no bumpsteer.

Having said that you dont get anything like as many bumps on the racetrack as on the road!

After getting mine setup at zcars i still found that it wasnt very good on the roads where Chris lives (really bumpy). I think getting the car as low as possible helps a lot. I lowered mine at the back after getting back from the Z cars setup and it felt much better.

[Ade]

Yeah lowering the back will make the effect bumpsteer less. I'll just be happy with much less twitchyness!

Did you get it set-up with your 048r's on it Dale?

[Jammy]

I know I haven't got a Z-car or anything, but I get a lot of bump steer with my lowered 1425, I think its down about 40mm, on 10s, so take what you want from that!

[R1minimagic]

no with the A008's...

The main reason i couldn't lower the car any more is that i still had the inner arches fitted for a bit of extra strength and somewhere to route the wires.

When i got home i decided to cut them out and set it to the same ride height as Chris's hyabusa.

I also noticed on his hyabusa that he runs massive negative camber at the front......

[The Matt]

wider tyres will 'feel' the bumps more too I guess especially lower profile ones.

[R1minimagic]

Another thing with these bike engined cars is that they are so much lighter that they suffer from unsprung weight a lot more which wont help at all on bumpy roads. There's not much you can do about that unless you are prepared to spend a fortune on lightweight components (titanium arms, mega expensive wheels, calipers etc)...

[The Matt]

yeah, this unsprung mass thinig goes against the tendancy to bang a set of 7 or 8 x 13 superlites on a Mini (like I have on mine).

[Jammy]

There's not much you can do about that unless you are prepared to spend a fortune on lightweight components (titanium arms, mega expensive wheels, calipers etc)...

Wahoo!!! At least its not all dome and gloom for my Clubby then!

[R1minimagic]

With Ade sat in the car, it shouldn't have a problem with unsprung weight I would have thought..... :fear: :fear: :fear:

[Jammy]

Lol! Without meaning to hijack Ades thread even more, why is bump steer reduced with a lighter unsprung weight? I thought bump steer was all to do with suspension/steering geometry?

[R1minimagic]

Yes you are correct, bumpsteer relates to changes in the length of the steering arm as the car moves up and down on it's suspension

The unsprung weight also has a similar effect as the springs/dampers and weight of the car has to control the weight of the unsprung bits! ie the lighter the car in relation to the wheels, hubs, discs, calipers, suspension gubbins the more the suspension tends to bounce up and down in relation to the car, making the car unsettled on the road..

[Bungle]

would stiffer shocks help and limit the movement ?

[R1minimagic]

Not really, thats the problem..... the weight of the car is on the other end of the springs/shocks giving the control. If you lighten the car, you need to lighten the suspension as well to keep the composure