Technical My Sei Tried To Kill Me!!

[Roswell]

OK maybe I'm over exaggerating a little but I had a bit of a moment last night.

I had to jump on the brakes to avoid a mountain bike falling off a Ford Focus travelling in the opposite direction and the Sei tried to swap end on me!

The NSR came round enough for the tyres to squeal and for me to have to correct it with an armful of opposite lock.

What would cause that to happen?

 

[gp3000000]

Plenty of things. Were you going round a corner?

Was the road surface wet, or loose dirt on a country lane?

How's your brake balance?

Do you have the same brand of tyre all round the car, or 4 different tyres on each corner? What brand(s)? How deep is the tread on each?

Condition of the suspension? When was your last MOT?

If you were going in a straight line on a dry road with 4 decent tyres the same brand and tread level on each corner, and your brakes are even, then I would be worried.

 

[Roswell]

The road was quite uneven so I tried the brakes again on a flat, even surface and got the same results.

I don't know the condition of the brakes as I've only had the car a week.

The car has three Nankang tyres and one Pirelli on the NSR. The Pirelli is the most worn.

The suspension seems OK.

The car was MOTed 2 weeks ago.

 

[arc]

so depsite being the most worn, the pirelli grips better than the nankangs? oh i'm glad i have decent tyres in each corner !!

 

[StoneNewt]

when you say the NSR came round did it step towards the curb or move towards the crown of the road.

Anyway your most likely explanation is the Pirelli tyre isn't in balance with the other tyres on the car. However it may well be worth getting the brake balance checked out as well, you only need a 5% variance up front & under heavy breaking the rear will become unsettles and start to slide in one direction.

 

[AppleSei]

Nankang tyres

Theres one of your reasons, put some decent rubber on, they arent the best tyre for the cento have a look on forum via search.

Majority of members will agree

 

[Roswell]

when you say the NSR came round did it step towards the curb or move towards the crown of the road.

The NSR went towards the curb.

 

[gp3000000]

Theres one of your reasons, put some decent rubber on, they arent the best tyre for the cento have a look on forum via search.

It's not necessarily a reason, the OP says the N/S/R came round, and the N/S/R has a Pirelli on, which on most tyre review websites (and my personal opinion) loses out to the Nankang.

Roswell, are they Nankang EX500 or XR611? And was it wet out when this happened?

so depsite being the most worn, the pirelli grips better than the nankangs? oh i'm glad i have decent tyres in each corner !!

Where do you get that statement from? If the N/S/R came round and the N/S/R has a Pirelli on then the Pirelli lost grip!

In my opinion after trying Nankangs, Pirellis, Goodyears and other budget brands the Nankang XR611 was the best tyre for the standard Sei, standard size, grip is the same as the Pirelli in the wet and quite a bit better in the wet. The EX500s are just as good in the wet, in my opinion, but more unpredictable in the dry.

The road was quite uneven so I tried the brakes again on a flat, even surface and got the same results.

Do you mean the same result as in the car braked evenly, or not? An MOT from 2 weeks ago would (should) indicate that the shocks were not worn & brakes were performing evenly.

I would put the cause down to having that one tyre of a different brand and more worn than the rest, at the moment.

 

[gp3000000]

Having just seen Roswell's post claryifying that the N/S/R moved toward the curb, means the Pirelli moved first...

Read StoneNewt's post on how the Pirelli is throwing out the balance, and get a nice new (or partworn depending on the tread levels on the rest of the tyres) Nankang put on there. Especially seeing as the Pirelli is worn, are we talking minimum (1.6mm) of tread or more?

 

[arc]

Where do you get that statement from? If the N/S/R came round and the N/S/R has a Pirelli on then the Pirelli lost grip!

not engaging brain, nevermind - i think they're both crap tyres - and mixing tyre types on axels is never wise

 

[StoneNewt]

Then on a nice quiet stretch of road, without any other cars try the same thing on the wrong side and see what happens. Obviously this really does need a clear section where you can see everything going on. It may be that the rear is simply very low on grip for your car, again this is a marker of badly worn or low quality tyres.

 

[Roswell]

I've just been out and inspected the tyres.

OSF - Nankang Toursport 611 with average 6.00mm of tread and (under) inflated to 1.5 bar

OSR - Nankang Toursport 611 with average 6.75mm of tread and (under) inflated to 1.5 bar

NSF - Nankang Toursport 611 with average 6.25mm of tread and (under) inflated to 1.6 bar

NSR - Pirelli P700-Z with average 4.75mm of tread and (under) inflated to 1.6 bar

 

[StoneNewt]

Do you mean the same result as in the car braked evenly, or not? An MOT from 2 weeks ago would (should) indicate that the shocks were not worn & brakes were performing evenly.

Unfortunately the MOT requires no more than 20% variance between braking effort on one axle. From experience, under heavy braking with a 'cento around 5% front imbalance is enough to cause the rear to step round due to it's very light rear end, lower quality &/or worn tyres tend to be worse for this sort of behavior.

 

[StoneNewt]

I've just been out and inspected the tyres.

OSF - Nankang Toursport 611 with average 6.00mm of tread and (under) inflated to 1.5 bar

OSR - Nankang Toursport 611 with average 6.75mm of tread and (under) inflated to 1.5 bar

NSF - Nankang Toursport 611 with average 6.25mm of tread and (under) inflated to 1.6 bar

NSR - Pirelli P700-Z with average 4.75mm of tread and (under) inflated to 1.6 bar

So all tyres are around 0.5bar bellow appropriate pressure?!

 

[Roswell]

Was it wet out when this happened?

No, it was dry and has been for a few days.

Do you mean the same result as in the car braked evenly, or not?

I mean the rear of the car moved towards the kerb on both the uneven and even roads.

 

[Roswell]

So all tyres are around 0.5bar bellow appropriate pressure?!

Yes.

 

[Diwiak]

absolutely normal for such car, and low pressure at all tyres. i dont believe better tyres will help stability

 

[Roswell]

Absolutely normal for such car...

Surely that can't be right.

 

[rallycinq]

Surely that can't be right.

Probably not 'absolutely normal' for a brand new car or even a car after a brake and suspension overhaul, but probably 'absolutely normal' for a used car with odd tyres and unknown brake/suspension history.

It could be many different things, or a combination of some or all of them.

Tyre, damper, spring, bush, brake shoes, cylinder, drum, bearing, alignment or road camber to name a few.

Cheers

SPD

 

[Roswell]

So how do I make sure it doesn't happen again?