Bigger disks but the same calipers
Discussion
What are the thoughts about putting on a larger disk - 380mm instead of 360mm - but using the same calipers. The calipers bolt to the car towards the axle, rather than horizontally, so all that is needed is 10mm longer bolts and a 10mm spacer.
It appears to be reasonably cost effective, particularly if new disks and pads are needed anyway.
Disks are available as either drilled and slotted as per OEM, or with a J-hook pattern. I know that J-hook is supposed to provide better performance, but I'd prefer to keep the OEM look unless the difference is massive.
Not planning on tracking the car, but would like more confidence when braking from speed on places like the German autobahns.
It appears to be reasonably cost effective, particularly if new disks and pads are needed anyway.
Disks are available as either drilled and slotted as per OEM, or with a J-hook pattern. I know that J-hook is supposed to provide better performance, but I'd prefer to keep the OEM look unless the difference is massive.
Not planning on tracking the car, but would like more confidence when braking from speed on places like the German autobahns.
Im no expert, and I may be completely wrong with this, but would bigger discs with the same size pads not make any difference, as the pads are just grabbing the same surface area as they were on the smaller discs.
I would have thought that the whole point of bigger discs would be that bigger pads would grab more surface area and therefore better stopping power.
You may be better with just a good set up of discs and pads.
I would have thought that the whole point of bigger discs would be that bigger pads would grab more surface area and therefore better stopping power.
You may be better with just a good set up of discs and pads.
Bigger discs will give both improved braking because of the increased leverage (callipers further from the centre) and also greater heat capacity because of the larger disc mass. The brake pedal feel will be the same, as you're not changing the hydraulics or bores. Pad material will dictate initial bite.
Few modern cars are under braked unless tracked or driven up & down mountains.
Few modern cars are under braked unless tracked or driven up & down mountains.
Smurfsarepeopletoo said:
Im no expert, and I may be completely wrong with this, but would bigger discs with the same size pads not make any difference, as the pads are just grabbing the same surface area as they were on the smaller discs.
I would have thought that the whole point of bigger discs would be that bigger pads would grab more surface area and therefore better stopping power.
You may be better with just a good set up of discs and pads.
No. Leverege.I would have thought that the whole point of bigger discs would be that bigger pads would grab more surface area and therefore better stopping power.
You may be better with just a good set up of discs and pads.
There are limits as to the diameter of disc that can be parried with any caliper as it will affect pad coverage. But a 20mm jump should be fine.
Will it really make any difference given his discs are already a good size ? probably not that he'd ever feel.
Tony1963 said:
Op, what is the problem with your brakes that you’re looking to cure?
The car is quite heavy and quite fast. When braking from high speed, I'd just like a bit more rapid retardation. I'm not looking for a massive improvement, but would like it to be a noticeable improvement.I've done it in the past and yes, it worked.
It's a well known mod on a MkIV Golf to upgrade the brakes. A simple job using the caliper carriers and discs from a TT (the callipers were the same) you could go from weedy TDi size discs to ones that did the job properly. I can't remember the sizes, but it was a worthwhile change with better and more consistent stopping power for longer.
It's a well known mod on a MkIV Golf to upgrade the brakes. A simple job using the caliper carriers and discs from a TT (the callipers were the same) you could go from weedy TDi size discs to ones that did the job properly. I can't remember the sizes, but it was a worthwhile change with better and more consistent stopping power for longer.
phumy said:
Bad......it has more rotating mass and you need to cut down on that if you want better acceleration and handling.
Where does leverage come into it?
Same clamping force acting on the same pad area but at a bigger radius = more torque generated by the same brake calliper/pad on the axle.Where does leverage come into it?
As stated above, the second benefit is more thermal mass to delay the onset of any fade due to rising temperatures.
phumy said:
Bad......it has more rotating mass and you need to cut down on that if you want better acceleration and handling.
Where does leverage come into it?
The 3rd party disks that I am looking at (Formula Dynamics) are lighter than the OEM disks, even though they're bigger. Obviously I would get new pads as part of the upgrade, and make sure they were decent.Where does leverage come into it?
chrisch77 said:
phumy said:
Bad......it has more rotating mass and you need to cut down on that if you want better acceleration and handling.
Where does leverage come into it?
Same clamping force acting on the same pad area but at a bigger radius = more torque generated by the same brake calliper/pad on the axle.Where does leverage come into it?
As stated above, the second benefit is more thermal mass to delay the onset of any fade due to rising temperatures.
I can see the heat being delayed due to the extra mass but it still has more rotating mass, which is not good, so unless your tracking the car it really has no other benefit
phumy said:
chrisch77 said:
phumy said:
Bad......it has more rotating mass and you need to cut down on that if you want better acceleration and handling.
Where does leverage come into it?
Same clamping force acting on the same pad area but at a bigger radius = more torque generated by the same brake calliper/pad on the axle.Where does leverage come into it?
As stated above, the second benefit is more thermal mass to delay the onset of any fade due to rising temperatures.
I can see the heat being delayed due to the extra mass but it still has more rotating mass, which is not good, so unless your tracking the car it really has no other benefit
The OP plans to move the calliper out 10mm to fit a 20mm larger diameter disc.
The effective centre of the (same) brake pad is now 10mm further from the axis of the hub.
=>This setup will generate the same frictional braking force on each disc as before, as it is the same pad applied by the same calliper piston area by the same operating pressure.
However, braking works by applying a torque to the wheel/axle/hub using the clamping of the pads onto the disc.
Torque = force (F) x distance from axis (R).
In this case R is now 10mm bigger, therefore the new braking torque will be proportionally larger than before.
Let's take a guess at effective pad radius - what was (say) 150mm now becomes 160mm with the change from 360mm to 380mm diameter disc. Braking torque is therefore (theoretically) 160/150 of the original value, a 7% increase.
Edited by chrisch77 on Tuesday 9th March 15:54
As mentioned above, press the brake pedal harder.
If the disc is lighter, then it probably won’t hold as much heat energy as the smaller disc.
I did the Mk4 Golf mod, 288mm to 312, and felt little difference, if any.
My measure is, if you can activate the ABS on a dry, smooth and level road, your brakes are powerful enough.
If the disc is lighter, then it probably won’t hold as much heat energy as the smaller disc.
I did the Mk4 Golf mod, 288mm to 312, and felt little difference, if any.
My measure is, if you can activate the ABS on a dry, smooth and level road, your brakes are powerful enough.
Tony1963 said:
As mentioned above, press the brake pedal harder.
If the disc is lighter, then it probably won’t hold as much heat energy as the smaller disc.
I did the Mk4 Golf mod, 288mm to 312, and felt little difference, if any.
My measure is, if you can activate the ABS on a dry, smooth and level road, your brakes are powerful enough.
But - if I need new disks and pads on the front, and these larger disks with "performance" pads (from a reputable aftermarket supplier) are the same price as pattern parts to OEM specifications (actual OEM parts are significantly more expensive), then is there any reason NOT to do this?If the disc is lighter, then it probably won’t hold as much heat energy as the smaller disc.
I did the Mk4 Golf mod, 288mm to 312, and felt little difference, if any.
My measure is, if you can activate the ABS on a dry, smooth and level road, your brakes are powerful enough.
The sort of thing I am thinking of is that the additional force on the bolts, given the 10mm spacer, will be greater and there is a risk that the bolts might bend / snap. Given the post above says it's 7% more, then I suspect it's not an issue.
You are going to need longer bolts, so make sure you source high tensile version - at least grade 8.8. The best option would be a socket head cap screw (I.e. with internal hex head) and you may be able to get these in 10.9 or even 12.9 grade (e.g. Unbrako branded not nameless off the internet!).
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