J30/Q45 rotors
J30/Q45 rotors
Are the rear rotors of the J30 and Q45 interchangable? If so, which years? Also, I am pretty sure that the front rotors are interchangeable, but it would be nice if someone could confirm that! thanks!
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greg_atlanta
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- Car: 2008 G35 Journey Sedan, silver/black (no sunroof), 1992 Q45 (in a past life)
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Q45tech
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- Car: 1990 Q45 342,400 miles 22 years ownership with original engine
1995 G20t 5 speed 334,000 miles 16" 2002 wheels - 205/50/16 Sr20ve vvl
The 97 Q and the 97J rear rotors are interchangable but the pads are a different composition. Each single pound of weight difference represents 16.5 foot lbs difference at 70 mph, so even 100 pounds should require a different pad/rotor design but this is rarely the case.
Notice the difference on a QX4 or other SUV.
If brakes can stop a car in half the time it takes to accelerate the car to the speed, the brakes have [can generate] quadruple to triple the HP of the engine.All Infiniti's have more than enough brakes to lock the tires from even 80-120 mph [with ABS turned off].Braking distance is primrily a function of tire softness [and the tires ability to shed heat in the 4 seconds sidewall height, tread width and rolling diameter] - once the brakes get fully applied.
The tires overheat faster than the pads rotors on a single high speed stop!!!!!!!!!!!!!!!!!!!! in 90F ambient because they may already be 120-130F at the road interface from simple rolling friction. [functiom of aligment camber and toein] and wheel bearings.Sure the iron rotor may go from 150F to 400F but the tires are not built to last long at 200-250F.
If a 4400 pounder at 70mph requires 726,000 lb/ft to stop how much heat is that over 4-5 seconds.........550/lb/ft per second is 1.0 HP= 2545 BTU HR...............thirteen hundred horsepower
Notice the difference on a QX4 or other SUV.
If brakes can stop a car in half the time it takes to accelerate the car to the speed, the brakes have [can generate] quadruple to triple the HP of the engine.All Infiniti's have more than enough brakes to lock the tires from even 80-120 mph [with ABS turned off].Braking distance is primrily a function of tire softness [and the tires ability to shed heat in the 4 seconds sidewall height, tread width and rolling diameter] - once the brakes get fully applied.
The tires overheat faster than the pads rotors on a single high speed stop!!!!!!!!!!!!!!!!!!!! in 90F ambient because they may already be 120-130F at the road interface from simple rolling friction. [functiom of aligment camber and toein] and wheel bearings.Sure the iron rotor may go from 150F to 400F but the tires are not built to last long at 200-250F.
If a 4400 pounder at 70mph requires 726,000 lb/ft to stop how much heat is that over 4-5 seconds.........550/lb/ft per second is 1.0 HP= 2545 BTU HR...............thirteen hundred horsepower
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Q45tech
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- Posts: 14296
- Joined: Tue Apr 30, 2002 3:19 am
- Car: 1990 Q45 342,400 miles 22 years ownership with original engine
1995 G20t 5 speed 334,000 miles 16" 2002 wheels - 205/50/16 Sr20ve vvl
Generally the oem pads out brake any aftermarket [including race pads] since the compound is optimized to the system on a single or dual sequential stop whereas aftermarket compounds are just slapped on a factory design type back plate..........they do no testing on our cars -------too expensive. Whereas the factory may test every single compound available on the car before deciding upon the correct one for the widest possible conditions.
Sure some compounds work better cold and some work better hot, some make less dust but they don't have the wide temperature range........its all a trade off and to get the factory business all pad compounds cost the same give or take 20 cents per pad so while $1.60 [on a $50,000 car] is important it is generally the least skimped area.
If you care about the shortest possible single stop distance you would be advised to purchase factory pads.
If high speed pursuit or extreme mountain driving is your game then there may be a better compound but it definitely will have trade offs and problems in cool weather and may not have the same initial bite so it may take a few feet longer to stop in a single 60 mph stop.Drilled/slotted rotors don't help in single 60 mph stops unless it is raining and may actually hurt performance [a small amount] in certain situations it all depends on the exact test you are doing!
Sure some compounds work better cold and some work better hot, some make less dust but they don't have the wide temperature range........its all a trade off and to get the factory business all pad compounds cost the same give or take 20 cents per pad so while $1.60 [on a $50,000 car] is important it is generally the least skimped area.
If you care about the shortest possible single stop distance you would be advised to purchase factory pads.
If high speed pursuit or extreme mountain driving is your game then there may be a better compound but it definitely will have trade offs and problems in cool weather and may not have the same initial bite so it may take a few feet longer to stop in a single 60 mph stop.Drilled/slotted rotors don't help in single 60 mph stops unless it is raining and may actually hurt performance [a small amount] in certain situations it all depends on the exact test you are doing!
when you say "97J", are you implying that the J30 changed its rear rotors in its last year of production, or do you simply choose 97, meaning through model year 97, (93-97)? i was under the impression that the J30 never changed brake design, so i would assume you meant the latter. thanks. i agree that fully stock brake components make for the best all-around driving as was originally intended by the car's engineers.