26 replies to this topic

[Rosssco]

Does a smaller front wheel (16 in) give more front bias ??

 
Smaller front rolling radius would bias to the front yep. Different disc diameters also affect bias (e.g. those running large 308mm front discs).

 

So running a 205/45/16 in place of the original 175/55/17 would increase front bias. However, its the same braking system as many Lotus which run similar rolling radius, but obviously use a different ABS controller (which I'm guessing regulates braking forces front / rear)

[piwo]

first of all, we need to consider what braking we mean.

if braking on the street on cold tires, on rain or sandy or bumpy asphalt often with leaves on the road then the front always locks on the serial abs and serial wheel size and increasing the width will not help much here. smaller wheel size is located lower front and a little more kg on the front axle which has some effect but small. An additional advantage is that with a smaller wheel diameter at the front there are more impulses to the abs from the front wheels, so the abs will be less the wheel will stop. which is good with a serial two-channel abs.

 

another situation is the track where the tires are hot and the asphalt is hot.

 it is harder to block the front, especially if it has grippy 205 or 215 wide Semislicki.

but still I feel faster locking the front with 215 / 40r17 v70a in front without abs.

the solution was to use weaker pads at the front and strong ones at the back. and it solved the problem.

additionally in the cold street when the brake is initialized there is no sudden blocking of the front and more force immediately hits the rear brakes because the pads in the back are harder. I did not notice any negative behavior with this configuration. maybe on ice on the bend it would affect but winter i'm not driving.

4 channel abs from 111r is very good and fast. and stronger pads at the back (i have ds1.11) and wider tires at the front (i have 215 / 40r17) do not bother lotus abs at all and in my opinion such a setup works well on the street and on the track. and no other calipers or larger discs are needed because even at 200km / h abs blocks the brakes. I also don't feel any overheating even after 30 minutes of continuous burning on the track.

I was also riding in parallel with a friend and braked from 160 to zero.

he was on 6-piston porsche calipers with 322mm discs with brake power corrector and without abs, and i on serial 288mm discs and calipers and lotus 111r abs . I stopped the car car length earlier.

 

Edited by piwo, 04 September 2019 - 04:31 AM.

[Flanners]

I don't track, I have AP4's on a TF, the 2's on the VX, obviously pad choice and owner's perception of feel/modulation is in the mix too, I have Brembo's on a Coupe and a GTV and Alcon 380mm on an RCZR. Best brakes are the Alcon's followed by the AP4's with the Brembo's the 'worst'. Haven't had AP4's on the VX but the feel and stopping power is far better in my experience on the AP4's than the 2's; have always found the VX brakes a bit 'wooden' and the ABS activation causing a few scary brown trouser moments over the years.

Edited by Flanners, 05 September 2019 - 07:09 AM.

[Nelpo]

Seems like we have a wide array of answers here, I'll throw in my two cents for good measure:

 

As long as your brakes are powerful enough to lock your wheels (and you have a reasonable front/rear brake balance), changing the components of your braking system will do absolutely nothing to increase the maximum deceleration you can generate under hard braking. The only way to decrease your stopping distance from a certain speed is to decrease your mass, or increase the friction between the tyres and the road.

 

 

So, if you want to stop faster, you can lighten the vehicle or fit tyres that generate more friction (wider tyres or stickier rubber).

 

 

This becomes a very different situation when you start running multiple hard laps round a track. Disc and pad temperatures will rise, decreasing the amount of friction generated between the disc and pad (and often moving the pad compound out of its effective temperature range) to the point where the brake pedal effort required becomes fatiguing to the driver (or impossible to reach) and any sense of 'feel' is lost. This is why race cars have big brakes, to be able to dissipate more heat (also to increase brake life). 

[piwo]

This is why race cars have big brakes, to be able to dissipate more heat (also to increase brake life).

Brakes on Race cars have to hold out 1,5 hour race. Race cars often weight 1200kg and more.
To improve stopping distance in vx220 can't allow to block front tires because if the front wheels get blocks then the abs automatically releases braking backwards.

[hairy]

 

To improve stopping distance in vx220 can't allow to block front tires because if the front wheels get blocks then the abs automatically releases braking backwards.

 

 

I didn't know that, can you explain how that happens Piwo?
 

[piwo]

Its Simple. ABS is not only for braking but also for maintaining a straight direction of travel when braking.secand thing is when the front blocks then controller dont knows what is really car speed and how much can blocks rear.best stop performance is when the wheel slip is 10% at all wheels. But controller can't counts This witout fifths ancillary wheel. So some wheels should't slip to knows what is really velocity.