tegwin
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| posted on 13/6/10 at 10:20 PM |
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Bigger tintop brakes
Can anyone apply some logic to this please..
My Polo GTI as standard has 260mm front disks....
Using a combination of Corrado G60 parts you can quite easily fit 280mm disks to the Polo..
(Corrado carriers fit directly on the polo caliper and hub!)
But the question is... will an extra 20mm on the diameter of the disk rotor make any difference to the braking ability or brake fade?
It would look very nice, but is it worth spending £100 on?
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mookaloid
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| posted on 13/6/10 at 10:32 PM |
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It's the kind of thing I would do if I needed to get new discs and pads anyway. That way the cost is only actually the difference between what
you were going to spend and the higher cost of the upgrade 
You should get better braking for a given amount of effort.
"That thing you're thinking - it wont be that."
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tegwin
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| posted on 13/6/10 at 10:40 PM |
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Hmm... the tricky thing is.. I could get another 5000 miles from the current brakes...... but I am planning a trip to the alps in a fortnight and
better brakes would be nice... im just not sure if spending the money to go bigger is worth the effort... at the end of the day its still the same
single piston caliper trying to slow the rotor down!
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mookaloid
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| posted on 13/6/10 at 11:17 PM |
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It seems to me to be a matter of leverage - the bigger the disc - the more leverage you have,
For a trip to the Alps you need the brakes to be in tip top condition and brakes which are nearly worn out will not be as good as new ones and
certainly not as good as upgraded ones
Cheers
Mark
"That thing you're thinking - it wont be that."
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britishtrident
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| posted on 14/6/10 at 06:26 AM |
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What you should do is renew the pads and flush through new fluid to avoid the fluid boiling. If the pads are worn thin more heat gets
transferred to the fluid.
[Edited on 14/6/10 by britishtrident]
[I] “ What use our work, Bennet, if we cannot care for those we love? .”
― From BBC TV/Amazon's Ripper Street.
[/I]
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Ivan
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| posted on 14/6/10 at 06:41 AM |
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I must admit I am a sceptic on this one - I don't believe bigger front discs will stop you any quicker than the originals - mainly because all
they will do is unbalance the front rear balance causing the fronts to lock up earlier and the ABS to activate sooner.
They will also impact on pedal feel. Either to the better or worse - it's a gamble.
If fade is a problem look to your pad selection first - get one level up in pads.
Also bigger rotors add to unsprung weight spoiling handling and ride.
I believe this urge to get bigger brakes is a result of an excellent marketing ploy by the aftermarket - in fact you should have the smallest brakes
that will do the job - if you can lock your wheels then your brakes are adequate. If fade is a problem then upgrade cooling air flow and pads and if
that doesn't work then look at bigger discs and different callipers.
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iank
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| posted on 14/6/10 at 06:44 AM |
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Is it on modified insurance? If not then the difference in insurance cost will probably be the biggest money element. (changing brakes will be
blamed for almost any accident if you don't declare them).
--
Never argue with an idiot. They drag you down to their level, then beat you with experience.
Anonymous
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tegwin
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| posted on 14/6/10 at 08:22 AM |
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Insurance isnt really an issue.
Plus. the disks are 6mm thinner than the standard ones, so the extra weight from the bigger diameter is negligable! (they do still work fine
apparently with the origional caliper)
The pads in there at the moment are some generic cheap ones from the local motor factors... perhaps a set of the "oem" spec ones
(Brembo/zendo) would be the better option.... I bet they are not cheap!
I guess the root cause is a lack of "feeling" from the brakes... especially when they are hot... you really have to stand on the pedal
sometimes to get it to stop..... Perhaps a bigger MC would be better :p
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Ivan
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| posted on 14/6/10 at 10:14 AM |
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quote:
Originally posted by tegwin
The pads in there at the moment are some generic cheap ones from the local motor factors... perhaps a set of the "oem" spec ones
(Brembo/zendo) would be the better option.... I bet they are not cheap!
I guess the root cause is a lack of "feeling" from the brakes... especially when they are hot... you really have to stand on the pedal
sometimes to get it to stop..... Perhaps a bigger MC would be better :p
I agree re pads - 80% of your problems will be corrected by correct pad selection - too soft a pad will give fantastic cold stopping with lots of feel
and poor feel and stopping ability when hot with the dreaded stand on the pedal and nothing happens - too hard a pad will give rotten cold stopping
with the stand on the pedal and nothing happens syndrome but will give great feel a stopping when hot.
If you need more pressure then you want a smaller MC not bigger - but then you will have more pedal travel and affect front/rear brake bias.
If you have enough meat on the discs I would suggest that you first get them faced, then replace the pads with good quality ones with fast road
compound not full race.
If that doesn't solve your problem then look at changing discs and you will have the right pad for them anyway.
If you want to change the master cylinders you had better fully understand what you are doing or get someone who does as a change in cylinder size
will impact on pedal travel, brake feel and brake bias.
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MikeRJ
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| posted on 14/6/10 at 11:21 AM |
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quote:
Originally posted by Ivan
if you can lock your wheels then your brakes are adequate.
This is one of those urban legends that keeps coming back like a bad dose of the clap! With the wheels locked the brakes are doing *nothing
whatsoever*, all the energy of the car is being converted to heat at the tyre/road interface.
The most significant improvement that larger brakes give is the greater thermal mass and surface area means they heat up more slowly and dissipate
heat more quickly.
They also tend to reduce braking effort which by itself may not be desirable as you mentioned, but this may also allow harder pads to be fitted
without requiring superhuman leg strength to stop with cold brakes.
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tegwin
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| posted on 14/6/10 at 11:34 AM |
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hmm.. some decent pads might be worth a try... deffinately the cheaper option..
So... what pads would be "suitable" for a road car?
EBC Greenstuff seem to be quite common... Although the OEM ones might be just as good...
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Ivan
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| posted on 14/6/10 at 12:20 PM |
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I have not had good experiences with EBC Greenstuff - despite being the right code they where marginally too big for the caliper once warm and cost me
two warped discs - only after sticking to the next disc did I work out that they were too big and not retracting properly and then a short session
with a file (there was only a couple of thou that needed removal) on the pad backing plate sorted the problem - thereafter I was reasonably happy with
them - but they where certainly less effective than the oem ones when cold.
MikeRJ - I never said locking wheels was effective - just that the brakes that can lock the wheel could achieve maximum retardation (ie just before
wheel locks) and not falling some way short of maximum retardation if they are physically unable to lock up the wheels ever.
As with all things - brakes are a compromise and one must be careful when modifying them on a normal commuter car where they are normally utilised
cold when commuting not to go over the top in preparing them for some other occasional usage to the detrement of the 80% scenario.
Certainly if you are using your car beyond what Joe Motorist would normally use it then consider modifying them to suit or your driving style to match
your existing setup.
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britishtrident
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| posted on 14/6/10 at 12:23 PM |
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Change the brake fluid ---
Old brake fluid and alpine passes = loss of pedal.
If the fluid boils the pedal goes to the floor without warning.
In contrast brake fade from the heat affecting the friction coefficient of the pads always gives you some warning, the car gets progressively harder
to stop.
If you can do 3 simulated emergency stops in quick succession from 60 mph with out requiring leg muscles like Geoff Capes on the third stop your
brakes are OK for a normal use.
[I] “ What use our work, Bennet, if we cannot care for those we love? .”
― From BBC TV/Amazon's Ripper Street.
[/I]
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alistairolsen
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| posted on 15/6/10 at 10:08 AM |
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I upgraded from 236x9 to 256x24 on my nova and the difference was night and day.
I had 284x24 on my corsa and again, the step up from the 256 combo was huge. The 256 and 284 used the same piston diameter.
Personally for the 100 quid Id be fitting them, bleeding through new fluid and buying some pads. If you want to use it mainly on the road, go for oe
spec but buy a brand like mintex rather than some of the complete poo on the market
My Build Thread
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ettore bugatti
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| posted on 15/6/10 at 07:44 PM |
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Look otherwise for Seat Ibiza Cupra R brakes;
-Brembo 4 pots
-305mm discs
-compatible with Polo chassis
-minimal 16" rims needed
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