28 replies to this topic

[the.grizzle]

Model: ROVER MINI RACING
Year: 1989
Hey all,
My problem is basically that when i bought my Mini a few weeks ago, its handling was amazing, and it would grip the road like anything.

However, where the experience was new to me, i obviously got happy with the handling, and my poor tyres wore out very quickly... I am running Yoko A539's all round on Ultralite 13x7 split rims. Well, i had the front tyres replaced with a new set of A539's, and as tracking was on offer at my local tyre place i thought i might as well have it checked. It turns out that it was out by about 20 degrees on the passengers side, and about 10 on the drivers side. So i had this fixed, and admittedly when i left it felt much nicer to drive and smoother.

However 100 miles later, I thought "finally i can give the new tyres some stick" only to find that the car does not compare to how it did handling-wise to how it did before...

And now im stuck for answers as to why? Surely the new tyres and perfect wheel alignment should have made an improvement if anything?

I was just wondering if anyone had the same issue, and if so how they resolved it?

Thanks guys.





Any non-standard parts that might be involved with the problem?

[Bungle]

did the garage jack the car up on the tie bars and bend them ?

[998dave]

Assuming you had 20 degrees tow in I wouldn't be surprised if it felt sharper going into corners as the outside tyre is scrubbing more, and wearing your tyre's out quicker.

Also the new tyres will have bigger tread blocks that will have more flex and movement.

Dave

[Wil_h]

20 degrees is about full lock, so I suspect that it wasn't out that much!

What exactly is the handling issue? understeer? oversteer?

Putting new tyres on the front only with really old tyres on the rear can give an imbalance in grip making it oversteer and feel unstable and unpredicatble, usually worse in the wet.

I may also be that the garage has made a mistake. I wouldn't let any tyre place touch my cars tracking (on any car) unless I specified the settings. The fact that you have 13s means that the standard settings might not apply. and if they told you it was 20 degrees out they may not know how to use their equipment.

[the.grizzle]

Thanks for the replies guys,

Well they definitely told me that was how far out they were, and even they said its one of the worst they've ever seen tracking out.

And the original reason i thought i should have it checked was due to the fact that driving down my straight and flat road, the steering sat as if i were turning sharply left and sometimes if i put my foot down even in third, it would squeal in a straight line.

And no, they definitely didnt jack up on the tie bars.

Though i did get rid of basically new tyres in just over two weeks

Hmm, Now i just get slight understeer whereas before the turn-in was amazing...

Dont get me wrong, it still handles well, just not how it did before...

[Dan]

What did they set the tracking to? Did they look up the Mini specifically or just use a common setting? The Mini is one of very few cars that is set toe out rather than toe in and so it's often set wrong at tyre and exhaust places. Do you mean the turn in was amazing or dangerous?

[Naif_Wolves]

I'm having the same problem...
Had tackign sortedo ut at my local tyre place (using laser's) and theer is no more scrubbing... but when turning in and under slight acceleration there is amazing understeer

[998dave]

And the original reason i thought i should have it checked was due to the fact that driving down my straight and flat road, the steering sat as if i were turning sharply left and sometimes if i put my foot down even in third, it would squeal in a straight line.

I'm not sure about 20 degrees out, but this sounds like there was a serious imbalance, no wonder you went through tyres so quickly, you were effectively skidding everywhere you went!

[the.grizzle]

Im not sure specifically what it was set to, but yes it was a common setting, which i thought would be ok. But no the handling was genuinely untouchable by any other small cars...

And yes i know i was dave, but you have to understand i would happily sacrifice a set of tyres a month to have that feeling again

Does anybody know a good setting, and i will go back and tell them to use my settings if any one knows a decent set up.

Thanks.

[Cooperman]

It definately couldn't be 20 deg out one side and 10 deg the other! Maybe 20 mm one side and 10 mm the other (even that would be a huge amount).
However, with those 13" wheels the geometry is never going to be correct as the steering geometry is designed for 10" wheels with no offset. That is why 10" are always best, followed by 4.5J x 12".
The best setting for the tracking is 'straight ahead'. i.e. no toe-in or toe-out. I would have it re-tracked.
Those Yokos are fine tyres, so you should be OK with them, although with that width they could have too much tyre area on the road in wet conditions which will give less grip in the wet.
You say the handling is worse. Now, do you mean handling or road-holding. They are not the same. A good handling Mini has safe lift-off oversteer when cornering and mild understeer when under power in a corner. That is not the same as road-holding which is an entirely different thing. Road-holding is the ability to generate cornering force (measured in 'G'). A poor handling Mini can still have high road holding, as unlikely as that may sound.
The other factor having a great effect on handling is the rear suspension settings. Ideally it shoud have between 3 mm and 5 mm toe-in on the rear wheels with zero to 0.5 deg negative camber. It's worth having that checked and, if it's not within those limits come back on here and someone will tell you how to set it up yourself.
If you have it tracked and all is OK, try altering your tyre pressures to, maybe, 34 psi front and 30 psi rear. Then adjust them a bit more each way until you like the feel of the car.
Damper settings also effect handling. If you stiffen up the front dampers, you'll increase the understeer. If you stiffen the rear you'll increase the oversteer. This applies only on smooth tarmac as on bumps or unsurfaced roads, the stiffness will effect the amount of time the wheels are actually on the ground. For example, on a really bumpy road, too stiff front dampers will cause the car to 'bounce' across the road in terminal understeer (been there, done that!).
I hope all this helps.

Edited by Cooperman, 27 April 2009 - 02:13 PM.

[the.grizzle]

Thanks cooperman, that is a great help, and i do understand the handling and road holding situations.

Basically before i had these tyres and tracking, the road holding was brilliant, and when it finally let go at the front very slightly as you said, i could lift off slightly for a second apply the power again, and then i would have a nice bit of controllable oversteer.

Now the road holding is poo in comparison, and now i will throw it into a bend and it has to understeer to the point where it must look like im about to fly off the road in a cloud of smoke before i have generated enough force to lift off oversteer and by that point its not controlled oversteer anymore, its just a 4 wheel slide to wherever the road wants to take me.

(In the dry, I don't take it out in the wet.)

And although i am unsure of the rear suspension set-up i know it is untouched and i was happy with the control of the oversteer before so i dont really want to fiddle with that to be honest. But i just cant understand why it understeers so much.

Thanks

Edited by the.grizzle, 27 April 2009 - 02:43 PM.

[GraemeC]

I thought a standard 3.5x10" wheel had just under 1" (24mm) positive offset, not zero.

Front tracking - the standard is 1.5mm toe out (around 12 minutes from memory)
Rear Tracking - the standard is 3.2mm toe in - this cannot easily be altered on a Mini with std rear suspensions parts.

[the.grizzle]

Hmm im not to sure on that one, and i know it has Gaz Adjustable shocks and hilo's all round im not too sure on the back but i know the front was definitely differently set to that.

I think i need to go and have a word with my tyre place because the way they have set my tracking has completely the handling and road holding* of my car....

Thanks for the help though guys, i really appreciate the opinions.

[Cooperman]

Are all the tyres new or only the front ones? Sorry if you've already told us.
If they are new they may just need quite a few miles to bed-in properly. Remember, with the very wide tyres the contact pressure between tyre and road is quite low when compared to a narrower tyre and thus bedding-in will take proportionally longer.
Have you got the damper settings to hard on the front?
What tyre pressures are you running?
Have you thought about taking it to another tracking specialist as it may be toeing-out too much?
Just a few things to try.

Peter

Edited by Cooperman, 28 April 2009 - 08:57 AM.

[Wil_h]

Some interesting stuff Cooperman, but no mini I've ever driven has lift off oversteer, it is however a common misconception that they do.

Also, the wider the tyre, the more grip will be generated wet or dry. However, wet grip is really dependant on how much water there is and how well you groves can get rid of the water. In wet conditiond where there is no standing water a wider tyre will be better than a narrow one. Where there is lots of standing water, narrow may be be better if the limit of the wider tyre to displace water has been reached.

I would agree that a mini on 10" wheels potentially handles better than those on larger wheels, this is mainly owing to the large tyre wall giving lots of feel and a slow drop off in grip. Larger wheels with narrow tyre walls tend to lose grip more suddenly, making them feel twitchy. My personal opinion is that 6x12s are the best compromise, lots of feel and lots of grip.

Tyre presures are definately worth looking at and experimanting with. To be honest it sounds like you mini handle pretty much how I'd expect.