ASK THE COACH
#166
Rennlist Member
TBDs have no affect on braking. I ran a Quaife unit in my '84 Carrera. LSDs have a very positive, stabilizing affect on braking and turn entry on the brakes. They will by design cause more understeer under hard acceleration. Having had a great LSD (4 plate cup car) in my RSA, I would never consider a TBD again. If I wanted to both autocross and track one car, I'ld get some fully adjustable sway bars so that I could loosen up the back for autocrossing, and tighten up the car for the track.
Does Quaife give better bang-per-buck on japanese gearboxes than Guard? Are they overall comparable?
#167
Rennlist
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I would assume that they work on the same principle, but have no idea as to who makes a better unit. They both have good reputations. For the LSD, I would go Porsche Motorsport or Guard.
__________________
Larry Herman
2016 Ford Transit Connect Titanium LWB
2018 Tesla Model 3 - Electricity can be fun!
Retired Club Racer & National PCA Instructor
Past Flames:
1994 RS America Club Racer
2004 GT3 Track Car
1984 911 Carrera Club Racer
1974 914/4 2.0 Track Car
CLICK HERE to see some of my ancient racing videos.
Larry Herman
2016 Ford Transit Connect Titanium LWB
2018 Tesla Model 3 - Electricity can be fun!
Retired Club Racer & National PCA Instructor
Past Flames:
1994 RS America Club Racer
2004 GT3 Track Car
1984 911 Carrera Club Racer
1974 914/4 2.0 Track Car
CLICK HERE to see some of my ancient racing videos.
#169
Three Wheelin'
Thanks for the 101 pointers. I am less concerned with being the butt of a joke (i was half joking with that) - I was just trying to express the humor that instructors might have the same way we would smile at teaching our kids how to ride a bike.
Hand Placement, seat position, Pedal control, etc....those are very important to me - if the basics are understood it makes "driving" easier.
Hand Placement, seat position, Pedal control, etc....those are very important to me - if the basics are understood it makes "driving" easier.
#170
Rennlist Member
Thread Starter
LOL...well, I think the only thing that cauuses amusement are driving techniques often seen in very powerful cars that involve the following sequence:
-drag race on straightaway
-park car & sip latte in corner
-lather
-rinse
-repeat
It is incumbent upon all instructors, with all levels of drivers, to encourage driving ALL cars like momentum cars.
JMHO....
#171
Rennlist Member
Dave, because I have a 996TT, I get kidded a lot for the reasons you stated above. How would you describe driving a turbo like a momentum car? Don't you also have to drive the car to it's strengths?
#172
Rennlist Member
Thread Starter
Those cars are very capable, actually, and get out of corners very well, but their weight & their understeer poses challenges. Trailbraking, later apexes, and frequent replacement of brake pads and tires...yeah they can be driven like momentum cars, withing their limits. That doesn't obviate their strengths, it emphasizes them IMO.
#173
Rennlist Member
I need some clarification about tire pressures. From what I've seen on the forums, most guys seem to set the front pressures a couple of pounds less than the rears for a 911 because of the 60/40 weight bias. I was reading an article yesterday that stated that in order to have a neutral handling car, you want all 4 tires to start sliding at the same time, as opposed to the fronts before the rears, or visa versa. Is the goal to have hot pressures equal at all 4 tires, or having hot temperatures equal at all 4 tires{I have a pyrometer}, or is it something else all together? How do you get all 4 tires to the same grip level in a 911?
#174
Rennlist Member
Thread Starter
One other factor to consider is that the rears will get hotter than the fronts (with a non-beginner driver) because even in AWD 911's, most of the drive energy is to the rears, all of the engine heat is back there, and the rear brakes are usually very poorly ventilated. So, depending on the driver & set up, sometimes having the rears start the same as the fronts, or even a bit lower, can work really well. Emphasis on sometimes. Also, to answer your questiion, I am a much bigger fan of taking probe pyrometer temps across the tread surface than just relying on pressures. And make sure it is a probe pyrometer, not the infrared versions, which onluy measure surface (rather than tread) temps.
#175
Rennlist Member
I have the probe type pyrometer.
From your answer I'm still not clear on what indicator tells you that all tires are equal in grip. If the rears will get hotter than the fronts, then I assume temperature is not the equalizing factor. I am able to feel when the tires get greasy from too high pressures. Do hot pressures give a better indication of grip? Should hot pressure be equal at all tires? Or is seat of the pants feel the only way to tell? That seems subjective rather than objective or quantitative.
From your answer I'm still not clear on what indicator tells you that all tires are equal in grip. If the rears will get hotter than the fronts, then I assume temperature is not the equalizing factor. I am able to feel when the tires get greasy from too high pressures. Do hot pressures give a better indication of grip? Should hot pressure be equal at all tires? Or is seat of the pants feel the only way to tell? That seems subjective rather than objective or quantitative.
#176
Rennlist Member
engine weight over the front part of the wheels in the rear vs not, is not the issue. Most of the forces are on the fronts, without question. even with 40/60 wieght, even with turbo, big power, etc. the braking is the hardest force on the turn, and the size stagger should make up on the heat comparisons of the front vs rear based on a neutral handlng car. (both tires getting worked in turns near the same) Because the fronts are causing much more physical change of speeds, vs the rears, they get hotter usually first. if they dont, there are driver factor that can change that.
the reason that many put slightly less pressure in the front, is to get more use out of the front tires, but its not the rule by any stretch. the weight transfer under braking is HUGE, even in a straight line , let a lone in trail braking. 10x the forces of acceleration putting greater force to the rears, generally.
the reason that many put slightly less pressure in the front, is to get more use out of the front tires, but its not the rule by any stretch. the weight transfer under braking is HUGE, even in a straight line , let a lone in trail braking. 10x the forces of acceleration putting greater force to the rears, generally.
I have the probe type pyrometer.
From your answer I'm still not clear on what indicator tells you that all tires are equal in grip. If the rears will get hotter than the fronts, then I assume temperature is not the equalizing factor. I am able to feel when the tires get greasy from too high pressures. Do hot pressures give a better indication of grip? Should hot pressure be equal at all tires? Or is seat of the pants feel the only way to tell? That seems subjective rather than objective or quantitative.
From your answer I'm still not clear on what indicator tells you that all tires are equal in grip. If the rears will get hotter than the fronts, then I assume temperature is not the equalizing factor. I am able to feel when the tires get greasy from too high pressures. Do hot pressures give a better indication of grip? Should hot pressure be equal at all tires? Or is seat of the pants feel the only way to tell? That seems subjective rather than objective or quantitative.
#177
Rennlist Member
Thread Starter
I have the probe type pyrometer.
From your answer I'm still not clear on what indicator tells you that all tires are equal in grip. If the rears will get hotter than the fronts, then I assume temperature is not the equalizing factor. I am able to feel when the tires get greasy from too high pressures. Do hot pressures give a better indication of grip? Should hot pressure be equal at all tires? Or is seat of the pants feel the only way to tell? That seems subjective rather than objective or quantitative.
From your answer I'm still not clear on what indicator tells you that all tires are equal in grip. If the rears will get hotter than the fronts, then I assume temperature is not the equalizing factor. I am able to feel when the tires get greasy from too high pressures. Do hot pressures give a better indication of grip? Should hot pressure be equal at all tires? Or is seat of the pants feel the only way to tell? That seems subjective rather than objective or quantitative.
#178
Rennlist Member
Those cars are very capable, actually, and get out of corners very well, but their weight & their understeer poses challenges. Trailbraking, later apexes, and frequent replacement of brake pads and tires...yeah they can be driven like momentum cars, withing their limits. That doesn't obviate their strengths, it emphasizes them IMO.
I find the most difficult part of driving it is the transition from quickly attained speed to intense braking for the next corner, and not over braking, lather, rinse,repeat, as you say. I need to get more flow into it. How can I apply the "momentum car " theory to help this situation?