Baller on a Budget BBK (BBBBK)

bajallama

New member
MWP":3u494xus said:
Inertia is of almost zero concern.
Sustained braking power and unsprung weight are the important ones.

I would have to disagree with you on that, for acceleration on a 4WD vehicle (and stopping one) inertia is very important.
Equation from a rotating wheel(with no slip), spring, and damper system is as follows:

Fin = 1.5m X" + bX' + kX

50% more effective mass due to translation and rotation of components. So that 20 pound rotor is going to feel like a 30 pound rotor when you accelerate and decelerate. If this were not the case lightened flywheels, small diameter multiplate clutches, carbon driveshafts and all lightweight drive line components would be of no performance value.

Here is a neat little tool:

http://stephenmason.com/cars/rotationalinertia.html#component
 

MWP

New member
Yeah ok, but will you see/feel that difference (seat of pants, or lap times)?
I very much doubt it.
How many of us care that much about tire weight and distribution of mass?

Drag racers may see a difference , but they dont care about stopping so much, so big brakes aren't on the must have list.
 

MWP

New member
bajallama":1os16ol3 said:
If this were not the case lightened flywheels, small diameter multiplate clutches, carbon driveshafts and all lightweight drive line components would be of no performance value.

Oh, and almost none of these are performance items due to lower inertia that helps with acceleration.
Sure they might have a slight positive effect in that regard, but its not why they exist.

lightweight flywheels & clutches - light to help with high rpm gearshifting (drop revs quicker on disengaging clutch). multiplate is for power handling.
carbon driveshafts - because steel is heavy (car weight), and they reduce unsprung weight in live axle applications.
 

ALLensTRAC

New member
As was stated earlier any modification to a brake system is a compromise based on the vehicles end goals. To me the important factors were mechanical bias, hydraulic bias, sustained braking force, increased pad contact area, increased overall diameter, reduced unsprung weight. Inertia is something that is increased but it's something I'll have to compromise on.
 

bajallama

New member
MWP":37kx2jcb said:
Yeah ok, but will you see/feel that difference (seat of pants, or lap times)?
I very much doubt it.
How many of us care that much about tire weight and distribution of mass?

Drag racers may see a difference , but they don't care about stopping so much, so big brakes aren't on the must have list.

Well, yes you should. You are constantly decelerating and accelerating on a track. Force(accel)=Force(stop). Therefore, lighter rotating components will effect your braking. I'm not trying to fight you guys on this but the math doesn't lie. It's very often overlooked and is a situation to consider. In FormulaSAE this was a very big concern and we did a lot to avoid the issue(Diffs with most mass near the center, smallest brakes we could get away with(rear was mounted on the diff) aluminum axle carriers). In a 4wd car you take a big hit in the area but you regain in reduced wheel slip (for acceleration).

A little guesstimated arithmetic:
Al flywheel = 10 lbs loss
Large vs Very Large rotor delta (4 corners) = 8 lbs loss
Carbon Driveshaft = 20 lbs loss
Wheel/Tires (4 corners) = 25 lbs loss

63 x 1.5 = 94.5 lbs of effective mass lost

The real objective of my concern is just don't think throwing the biggest brakes you can on a car is going to make it perform at its best. If the thermal mass (which the AllTrac completely lacks) is correct and the proper clamping force is determined, there should no need to put 18" rotors on your car because you WILL effect your lap times and handling. Other things like pads, fluids, and ducting will make the additional performance push you need.

MWP":37kx2jcb said:
Oh, and almost none of these are performance items due to lower inertia that helps with acceleration.
Sure they might have a slight positive effect in that regard, but its not why they exist.

lightweight flywheels & clutches - light to help with high rpm gearshifting (drop revs quicker on disengaging clutch). multiplate is for power handling.
carbon driveshafts - because steel is heavy (car weight), and they reduce unsprung weight in live axle applications.

Yup they help those as well, but you better tell ACPT they have they're selling points all wrong:

Independent testing by a leading automotive magazine (Turbo, October, 1996) showed rear wheel horsepower gains of more than 5% with the simple switch to an ACPT carbon fiber driveshaft. This significant increase is primarily due to lower rotational mass of the driveshaft.

http://www.acpt.com/Products/Composite-Driveshafts.aspx

Low engine rotating inertia is essential as, in the lower gears especially, it adds significantly to the overall mass of the car that has to be accelerated.

Source: http://www.grandprix.com/ft/ftpw005.html
 

MWP

New member
CF tail shaft increases wheel HP? :twisted:
It was probably tested on a rolling road / chassis dyno with little load and a very high ramp rate where inertia will play a much larger role.
Anything to make the marketing team happy.

Anyway, we are talking about modified street cars here, not top $ or top engineered race cars.
Its far cheaper for us to increase engine HP than it is to reduce rotating mass for the same gain.
We also cannot test 10 variations of calipers and rotors to come up with the lightest combination that suits the needs, hence why its better to aim larger.
All our needs are different too, so one simple formula wont work.

Assuming i can find parts, ill be looking at the IS350 caliper + 2pc STi rotor setup.
 

underscore

Well-known member
bajallama":a8qoi7qd said:
smallest brakes we could get away with

The only problem with that is that in a multi-use vehicle the smallest you can get away with is going to vary depending on what you're doing. Brakes that are sufficient for one task might be too small for another. For a car that's used for more than one thing I'd rather just have big effing brakes that I don't have to worry about cooking. Sure I lose slightly in a few areas, but IMO it's worth is because stopping trumps going every time.
 

bajallama

New member
MWP":jhnoinew said:
CF tail shaft increases wheel HP? :twisted:
It was probably tested on a rolling road / chassis dyno with little load and a very high ramp rate where inertia will play a much larger role.
Anything to make the marketing team happy.

I see no falsehood in their data, it will show a increase in wheel power in transient conditions since it takes kinetic energy to rotate an object. That mass is no longer there so no that energy will be put down on the pavement. Steady state HP will show no improvement.

Anyway, we are talking about modified street cars here, not top $ or top engineered race cars.
Its far cheaper for us to increase engine HP than it is to reduce rotating mass for the same gain.
We also cannot test 10 variations of calipers and rotors to come up with the lightest combination that suits the needs, hence why its better to aim larger.
All our needs are different too, so one simple formula wont work.


I am in agreement with this statement. I'm not saying I will put any of those components on my car, I'm obviously on a budget. It was used as an example to show that it is important and everyone posting seemed to shrug it off. It is very important though when you are racing in power/weight limited street classes.


Assuming i can find parts, ill be looking at the IS350 caliper + 2pc STi rotor setup.

It's pretty much the same setup I have, why go a more expensive caliper?
 

bajallama

New member
underscore":a4updg71 said:
bajallama":a4updg71 said:
smallest brakes we could get away with

The only problem with that is that in a multi-use vehicle the smallest you can get away with is going to vary depending on what you're doing. Brakes that are sufficient for one task might be too small for another. For a car that's used for more than one thing I'd rather just have big effing brakes that I don't have to worry about cooking. Sure I lose slightly in a few areas, but IMO it's worth is because stopping trumps going every time.

My example with this was the reduction in inertia because we were racing. The system was brought to its minimum need because in competitive racing that's how you win. For a multi-purpse vehicle, sure you have compromise due to budget and application. But doing the calcs can help you produce something that does not hinder other aspects of your car, is that hard to do?
 

ALLensTRAC

New member
bajallama":6u8wh4bt said:
Anyway, we are talking about modified street cars here, not top $ or top engineered race cars.
Its far cheaper for us to increase engine HP than it is to reduce rotating mass for the same gain.
We also cannot test 10 variations of calipers and rotors to come up with the lightest combination that suits the needs, hence why its better to aim larger.
All our needs are different too, so one simple formula wont work.


I am in agreement with this statement. I'm not saying I will put any of those components on my car, I'm obviously on a budget. It was used as an example to show that it is important and everyone posting seemed to shrug it off. It is very important though when you are racing in power/weight limited street classes.


Assuming i can find parts, ill be looking at the IS350 caliper + 2pc STi rotor setup.

355mm caliper on a 326mm rotor?


The IS350 caliper is designed for 334mm rotors not 355mm. The GS350 Fsport uses a different mono block body designed to fit the larger rotor. Piston size and pads are the exact same. In fact I'm going to have to grind some metal out of the caliper to get it down so as not to have 1mm of pad overhang.

As for your statement regarding us shrugging it off believe me I did not. If anything I was waiting on your excel spread sheet so I could run my rear options for bias. I believe everyone posting in this thread understands what you are trying to convey but we all take it as a necessary evil. As you said the Alltrac completely lacks thermal mass and with increasing that mass comes increased diameter and width. This increases the negative effect associated with inertia. Personally I'm not going to increase the diameter beyond 14" as it's not needed.
 

bajallama

New member
The IS350 caliper is designed for 334mm rotors not 355mm. The GS350 Fsport uses a different mono block body designed to fit the larger rotor. Piston size and pads are the exact same. In fact I'm going to have to grind some metal out of the caliper to get it down so as not to have 1mm of pad overhang.

As for your statement regarding us shrugging it off believe me I did not. If anything I was waiting on your excel spread sheet so I could run my rear options for bias. I believe everyone posting in this thread understands what you are trying to convey but we all take it as a necessary evil. As you said the Alltrac completely lacks thermal mass and with increasing that mass comes increased diameter and width. This increases the negative effect associated with inertia. Personally I'm not going to increase the diameter beyond 14" as it's not needed.

My bad (and edited). I thought he was talking about the GS caliper for some reason, I got them mixed up from the previous discussion. Ya the sheet is kinda messy, I'm reorganizing it to make it more user friendly. Rear bias can always be adjusted, but always goal your rear setup so it's as close to ideal with not having to have a proportioning valve almost closed to retain 4 wheel lockup, but not too small where you don't, that's why you calculate! So I'll let you know when I finish it.
 

ALLensTRAC

New member
RedCelicaTRD":214o3g8o said:
Do you happen to have a part number for those rotors?

Oh I almost forgot here are the rotor part numbers:
RH 43512-30371
LH 43516-30061
These are the most current updated numbers from the TSIB. I know a couple people pm'd me for them so I figured I'd post them here.
 

RedCelicaTRD

Moderator
I checked a few other online spots and also come up with an MSRP of just under $100. I say if you want them, get them now. That price wont last forever. The low price is likely associated with the TSB.
 

Cuttyman9

New member
Those are worth nabbing just cuz lol
So those part numbers come with the disc the hat and the bolts all assembled?

Thank you for posting them!
What I was thinking is if I had two sets of bolts and a spacer bracket for my bracket(or two sets of brackets) I could swap between rotors at least that way I still have some wheel options.
 

ALLensTRAC

New member
RedCelicaTRD":39eztgcz said:
I checked a few other online spots and also come up with an MSRP of just under $100. I say if you want them, get them now. That price wont last forever. The low price is likely associated with the TSB.

That's exactly what we thought but the pre TSB numbers and post TSB numbers come up with the same price. We also checked stock and there were quite a few in our regional warehouse. If you want the pre TSB numbers just remove the 1 from the end and replace it with a zero (the ones I have). If anyone really wants these I can buy them for you but shipping may not make it cost effective. I will have to look into that.

I don't have the IS350 caliper part numbers as I got mine through a new take off situation. They are not cheap through the dealer! IIRC the correct body F sport ones were 330$ each dead cost so expect an online retailer to charge around 450-500 per caliper. They can be had much cheaper on eBay though.
 

bajallama

New member
Can I ask why you guys are hung up on the IS350 caliper? I am pretty sure they almost identical in size and weight as the UCF30 caliper at almost 5 times the price?? I paid $80 for mine each

I tried to find the piston diameter for it and it looks like they are 42.8 mm just like the UCF30's but just don't have fancy paint (which I prefer) :shrug: or are the F sports 6 pot
 

ALLensTRAC

New member
Cuttyman9":2p6m74yk said:
Those are worth nabbing just cuz lol
So those part numbers come with the disc the hat and the bolts all assembled?

Thank you for posting them!
What I was thinking is if I had two sets of bolts and a spacer bracket for my bracket(or two sets of brackets) I could swap between rotors at least that way I still have some wheel options.

Yessir it is everything!! They do not list a way to disassemble them and from me looking at the hardware it would require drilling them out. I have no experience with full floating rotor hardware so maybe someone else can chime in regarding how to remove the rotor from the hat.
 

ALLensTRAC

New member
bajallama":2261aorx said:
Can I ask why you guys are hung up on the IS350 caliper? I am pretty sure they almost identical in size and weight as the UCF30 caliper at almost 5 times the price?? I paid $80 for mine each

I tried to find the piston diameter for it and it looks like they are 42.8 mm just like the UCF30's but just don't have fancy paint (which I prefer) :shrug: or are the F sports 6 pot

I got the whole front and rear setup from an IS350 as new for free originally. I had planned to put them on my IS250 but I traded that car in on my ES. I then sold them to a buddy who had them painted Fsport blue with the decals. The calipers pictured are stock IS350 calipers. The real IS F-sport add on kit is 6 piston front 4 piston rear and are just Stoptech kits rebranded.

The IS350 caliper has non staggered pistons at 40mm x4. They are not the same as the UCF30 calipers. There is increased clearance for larger rotors, smaller pistons, lug mount, larger pad swept area, and they are Advics calipers vs. Sumitomo although I believe Advics bought or merged with Sumitomo. Doesn't matter they are both owned by Toyota.

I really wanted to use the LS calipers but you would have to grind into the fluid passages to get them to sit over the GS rotor. That and the pad annulus would not line up properly.
 
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