Wider Tyres

[GavinL]

probably an old question..but

 

Is it worth putting wider tyres, I was thinking 245 front and 265 rear on

the MKIV. Do you get more grip or does the handling go to sh*te.

 

Do you tell your insurance co about wider tyres?

 

Thanks..........

[Branners]

dont forget if you put 265s on the back the rolling radius will go up and the speedo becomes slightly less accurate. I could only find a 265x40x17 which isnt a huge increase and to be honest is the tyre I should have bought, but I went the cautious route and fitted 255 as per the stock tyre sizes.

 

Going up a size may slightly help grip but it will also change the handling of the car to make it slightly less predictable. I think Toyota spent most of their time getting a neutral handling car, stick bigger tyres on or lowering springs and it changes it totally. My car is now running Eibachs and turn in and handling has improved BUT the car is now quite tail happy under really hard braking. That could also be attributted to the Chris Wilson pads which are just awesome at stopping the car.

 

JB

[Phil]

Agreed. I've got Eibachs on standard shocks with CW pads and when we were at Bentwaters I could almost reverse it into corners by holding the brakes on too long.

 

This was mostly needed after the front straight because I was struggling for turn in grip and wanted some oversteer!

[Branners]

a properly trained driver would never turn in under braking, you do everything before you get to the corner and then steer and accelerate as required. The problem is remembering to do that corner after corner, lap after lap. I get bored trying to remember my training and just let lose, which is what happened when I did my psycho spin and blew the crank oil seal!!

 

I wonder what happens when I eventually fit UK brakes...might change the handling yet again.

 

Even with the strange handling I would still not remove my eibachs, I accept the change because the car looks much better with the nose down approach, and I havent even ground it out once.

 

JB

[Paul Booth]

As I wasn't the one to raise brakes in this thread.....

 

I could probably answer my question by lifting the bonnet but anyway, I'm already sat at my PC.

 

Most turbo vehicles have to have a vacuum pump to drive the brake servo and I've recent experience of the huge difference it makes if that pump is not operating 100%, on another car.

 

Does the Supe have a vacuum pump/reservoir or does it achieve the same goal by other means?

 

[Guest Ash]

 

 

No, just the normal manifold connection. There is a one-way valve, just before the flexi-pipe connecting to the servo, that stops the servo being pressurised and that's it.

 

Yours,

J

[Phil Wall]

John

 

I agree the stock suspension does have a nose up look

 

Your set up looks very good, a much more aggressive stance!

[Guest Ash]

 

 

"a properly trained driver would never turn in under braking........."

 

Unless you wanted to take the inside line, late on the brakes, come in real hot and scrub-off some pace with speed-induced understeer, drift out and cut in front of someone trying to take you on the outside then step on the gas. :biggrin:

 

Yours,

J

[francesca]

Ash, you hooligan! I'm shocked! (VVBG)

[Phil Wall]

Nice move!

Can't wait to meet you on the track:biggrin:

[Paul Booth]

Quote: from Ash on 6:10 pm on July 6, 2001[br]

 

No, just the normal manifold connection. There is a one-way valve, just before the flexi-pipe connecting to the servo, that stops the servo being pressurised and that's it.

 

Yours,

J

 

That probably explains why the brakes on my 406 are 100x better than my Supe (Turbo + vacuum pump & reservoir)

 

[Doughie]

 

The classic "get all your braking done in a straight line" is a good basis point to start with for track driving, but there is a technique called "trail braking" where you do use moderate braking right up til the apex.    not HARD braking but moderate braking.   This all depends on the handling characteristics of the vehicle, how tight the corners are, etc.etc.  

Generally in a road car, they're way too softly sprung (for a track) to entertain much trail braking as the weight transfer forward is extreme and this (as JB has found) hugely redcues weight on the rear, which leads to rear wheel lock up and off you go.... generally.

 

If you've piled into a corner too quick (certainly on a kart which only has rear-axle brakes anyway) then you HAVE to get off the brakes when you turn in (even though you're going too quick) otherwise it's like handbraking a car - you'll spin.    better to throw it in too quick and scrub off speed through oversteer.    not the quick way to get round the corner, but generally you keep going rather than spinning to a halt.

 

 

[Rich J]

Quote: from Paul Booth on 7:44 pm on July 6, 2001[br]

Quote: from Ash on 6:10 pm on July 6, 2001[br]

 

No, just the normal manifold connection. There is a one-way valve, just before the flexi-pipe connecting to the servo, that stops the servo being pressurised and that's it.

 

Yours,

J

 

That probably explains why the brakes on my 406 are 100x better than my Supe (Turbo + vacuum pump & reservoir)

 

 

WHen your braking you should be off boost and should be getting vacuum anyway, unless you've got your foot down on both peddles which isn't going to do you stopping distances any good :biggrin:

[Paul Booth]

Well that's what I thought when Peugot told me that the reason it wasn't stopping very well, about 6 months ago, was that the brake vacuum pump was goosed.

In fact I asked them why it was there.

They told me that the delay in building a decent vacuum from going  off-boost was too long for consistent brakes. Hey, they were paying for it under the warranty so my interest stopped at that point.

 

Intuitively, I would assume the principle used by Toyota to be effective but we all know what people who make assumptions deserve, don't we? Hence my question.

 

If I can make my car stop better, all the better for when I start to make it go quicker.