TECH TALK - ask your technical car questions

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t3ice
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Re: TECH TALK - ask your technical car questions

Post by t3ice »

A noob question here... ive not done any driving in the snow here, but i just wanted to know whether i would need to change the tires of my car for everyday snow driving, since the previous owner had just replaced all 4 tires, n im not keen to replacing all four again.

Also, my car is equipped with abs, but ive heard that there are still chances of tires locking up under braking while on snow/iced roads. How true is that?
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Re: TECH TALK - ask your technical car questions

Post by Striker94 »

steelsnake00 wrote:However, because they are designed to work at higher temperatures they tend to require vastly increased braking pressure from the driver when cold, and have very little in the way of pedal feel.
So you're saying that they're basically optimized for racing aplications? Also on brakes, what's with the "4-piston, cross-drilled" thing? I has no idea whatsoever what it means, so if you guys could help me out???
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Re: TECH TALK - ask your technical car questions

Post by boganbusman »

t3ice wrote:A noob question here... ive not done any driving in the snow here, but i just wanted to know whether i would need to change the tires of my car for everyday snow driving, since the previous owner had just replaced all 4 tires, n im not keen to replacing all four again.
It would be a very good idea to buy a set of snow tyres if you are going to go through snow on a regular basis.
Try and find a set of second-hand wheels, then you can easily swap from normal tyres to snow tyres as the seasons change. I know new tyres are expensive but it's the most important safety feature on the car :wink:
t3ice wrote:Also, my car is equipped with abs, but ive heard that there are still chances of tires locking up under braking while on snow/iced roads. How true is that?
ABS works by quickly releasing and applying the brakes, on off on off etc. On modern cars the ABS works very fast and the wheels shouldn't lock up at all, but on older cars the ABS might allow the wheels to lock for a split second, which is alright on a dry/wet road but on ice it's not going to work very well. Still better than no ABS though . . .
Striker94 wrote:Also on brakes, what's with the "4-piston, cross-drilled" thing? I has no idea whatsoever what it means, so if you guys could help me out???
"4-piston" means that there are 4 hydraulic pistons inside the brake caliper. A typical 4-piston design will usually have 2 pistons on each side of the disc.
"Cross-drilled" refers to the disc, meaning that it simply has holes drilled into it.
Here's a picture of a cross-drilled rotor and 4-piston caliper:

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This rotor is actually slotted as well, which are those grooves that go between each row of drilled holes.
There are two pistons visible inside the caliper, and the other two you can't see because they're on the other side.
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Re: TECH TALK - ask your technical car questions

Post by t3ice »

Well.. as a precaution, i am getting my tires replaced, but i haven't bought new ones. Instead I just borrowed them from a friend who is leaving for a few months and has car with a similar tire profile.

About the abs, i tested it myself on the high way. I drove fast and braked suddenly and as u'd expect, i could feel the pumping-effect of the abs on the brakes. I never actually noticed it before, but it seems to be working.
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Re: TECH TALK - ask your technical car questions

Post by baumaxx1 »

Now... a few thing... more pistons=more braking pressure but it changes the pedal feel... is it softer? or harder?

And the slotted rotors keep the brake oad surface even from memory, and the cross-drilling is to dissipate heat better.
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Re: TECH TALK - ask your technical car questions

Post by boganbusman »

baumaxx1 wrote:Now... a few thing... more pistons=more braking pressure but it changes the pedal feel... is it softer? or harder?
Uprgading to bigger brakes and/or having more pistons per caliper will give you a softer pedal, unless you upgrade the master cylinder as well, which is what you should do.
Just upgrading the master you give you a harder pedal, which provides easier pedal modulation but will make it a bit more tiresome on your legs.
baumaxx1 wrote:And the slotted rotors keep the brake oad surface even from memory, and the cross-drilling is to dissipate heat better.
Slotted rotors are for keeping the pad/disc contact area clean from dirt and water, and to vent gases which are produced by the pad.
With drilled rotors, you're right about them being for heat dissipation, but remember that you are also losing contact area and overall mass, which can be considered a downside.
This is debatable, but under track conditions it's better to run plain or slotted rotors because drilled rotors can crack pretty easily. IMO it's more for show than anything else.
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Re: TECH TALK - ask your technical car questions

Post by baumaxx1 »

Yeah, I've seen drilled ones crack too. But yeah, brake choices require compromise.
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Re: TECH TALK - ask your technical car questions

Post by steelsnake00 »

boganbusman wrote:This is debatable, but under track conditions it's better to run plain or slotted rotors because drilled rotors can crack pretty easily. IMO it's more for show than anything else.
If the slots or holes have been correctly cut before the disk was finished then they won't crack. It's just cheaply, mechanically drilled disks which do because of the pressure of the bit causing small fractures in the metal.
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Re: TECH TALK - ask your technical car questions

Post by RSZETEC »

ive always found plain rotors with some decent pads(mintex are my weapon of choice)are spot on for track day conditions, my old fiesta track car ran standard discs with mintex pads with a 2.0 engine on track and it was just fine used to be able to out brake some more expensive toys there cos of its low weight + high suface area contact between the discs+pads(did fade a bit tho)

really for a road/track car keep the standard setup or upgrade the brakes with bigger disc/calipers from a highr model as it will still be nice to drive as ive found with 4-6pot calipers and large discs you dont realy get a good bite point theyre either on or off and they sqeal like nothing else when cold :D
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Re: TECH TALK - ask your technical car questions

Post by steelsnake00 »

That's because you need to uprate the master cylinder when your fitting large big brake kits. The 4-pot Porsche monoblocks I had on my Audi S2 (with 340/323mm grooved RS4 disks) needed a new master cylinder (from a 968 Clubsport if I remember rightly) and my M3 CSL 6-pot AP racing brakes used a custom Wilwood master cylinder.
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Re: TECH TALK - ask your technical car questions

Post by RSZETEC »

pretty much what im going to be doing with my mk2, gonna be using a land rover master cylinder along with(if i can find them)a set of austin princess 4pot APs on the front and some sierra discs and calipers on the back :D
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Re: TECH TALK - ask your technical car questions

Post by viper16 »

Im confused now when I start building my car im going to get a RB26 i want to up the displacement and so far I've only found 2 stroker kits the Brian Crower 2.9 and the OS Giken 3.1. Well my autoshop teacher told me that the bigger the discplacement the less revs and boost it can handle is this true. If so would it be better to keep the stock bore.
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Re: TECH TALK - ask your technical car questions

Post by t3ice »

some how i have this sudden manic urge to powerslide in the rain... I just wanted to know what toll does it have on the car. :)
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Re: TECH TALK - ask your technical car questions

Post by xHaZxMaTx »

Depends on what you hit when you go careening off the road. ;)

Sliding around on wet pavement is a very bad idea if you don't know exactly what you're doing. I know from experience. :P I was lucky I only had to buy new tires.
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hehe.. but normally i powerslide with a fwd car if u call it powersliding :P ..which i feel is a tad safer, but i just wanted to know whether it has any adverse effects on the cars axels and such.

But yeah, i tried powersliding with a rwd car once, and boy it was uber scary and uber fun at the same time .. :D almost wet me pants
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Re: TECH TALK - ask your technical car questions

Post by PSZeTa »

The same things that happen to your car when you're simply driving it, just at an increased rate.
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Re: TECH TALK - ask your technical car questions

Post by RSZETEC »

The bigger the displacement the lower down in the rev band it will make its maximum power, it can rev higher but it would be pointless as it would be just stressing out the engine more, max boost is more reliant on lower compression than displacement the lower the compression ratio the more boost you can run which is why its not a great idea to turbocharge an N/A engine without lowering the compression ratio :D
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Re: TECH TALK - ask your technical car questions

Post by steelsnake00 »

viper16 wrote:Im confused now when I start building my car im going to get a RB26 i want to up the displacement and so far I've only found 2 stroker kits the Brian Crower 2.9 and the OS Giken 3.1. Well my autoshop teacher told me that the bigger the discplacement the less revs and boost it can handle is this true. If so would it be better to keep the stock bore.
Increasing the displacement with a stroker kit modifies the compression ratio and the cylinder stroke. This in turn means that because the conrods need to be longer. Longer conrods mean more weight and more weight means less freedom to rev.
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Re: TECH TALK - ask your technical car questions

Post by boganbusman »

A stroker has shorter conrods, not longer :|

They can't rev as hard because the piston and rod is going through more g-forces at each end of the stroke, which puts more stress on all the reciprocating parts.
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Re: TECH TALK - ask your technical car questions

Post by steelsnake00 »

boganbusman wrote:A stroker has shorter conrods, not longer :|
You are quite right, forget what I said. The only experience I have with strokers is stroked 2.5L I5 turbo engines, which use the Eurovan I5 block and actually have longer conrods than standard 2226cc I5 turbo motors.
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Re: TECH TALK - ask your technical car questions

Post by TONTO89 »

hey I don't know if this is a tech question
but I didn't know where to put it and I didn't want to start a new thread.

my friend and I were trying to figure out the difference between pearlescent and iridescent paint finishes.

can someone shed some light on this for me?
try to explain it in a way that someone who has no idea about paint in any way would understand please lol
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Re: TECH TALK - ask your technical car questions

Post by Koenigsegg_Rox »

Well as far as I can tell, pearlescent has 2 or more different colours, and iridescent only has 1. I've never seen iridescent though so....

The most obvious example of pearlescent paint is chameleon, like House Of Kolor Kameleon, where there are many different colours that change depending on the light and viewing angle. There's a VX Commodore rolling here with chameleon paint, I might be able to take some pics.

Otherwise, this is sort of an example of it.
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Re: TECH TALK - ask your technical car questions

Post by boganbusman »

Iridescence and pearlescence are basically the same thing :| [read: exactly]
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Re: TECH TALK - ask your technical car questions

Post by t3ice »

Yea, even if you wiki for pearlescent or iridescence, you result at the same page.
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Re: TECH TALK - ask your technical car questions

Post by baumaxx1 »

Seems like EA is just compensating for a restrictive pearlescent paint system... because I've never heard of iridescence outside of an EA game... and I'm buried in the car magazines.
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