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Re: 300mm rear brake conversion
[Re: Jimbo]
#1071429
17/07/2010 22:48
17/07/2010 22:48
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Taz
Unregistered
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Taz
Unregistered
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As Jimbo says, not cheap, but the handbrake works !, basically, the leverage point of the caliper is moved out & makes all the difference plus it's also about the smae mass as the old crap, as it's a 2 part disc with alloy bells & disc
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Re: 300mm rear brake conversion
[Re: barnacle]
#1071518
18/07/2010 11:12
18/07/2010 11:12
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Joined: Mar 2008
Posts: 5,095 highlands
jimboy
Club Member 857
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Club Member 857
Forum is my life
Joined: Mar 2008
Posts: 5,095
highlands
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It's the front brakes that does most of the work on a car, we all know that,[cant remember the %] so I'm of the impression that it's the front that I always upgrade, if needed. It's been mentioned before, if you go overboard with the rear, you can sometimes make the car lock up & handle badly, under heavy braking. OK the Coop has ABS, but if on the other hand it's a case of wanting the handbrake to work properly as I see mentioned, I would be investigating the cause, & curing this.
I'm an old git & happy with it,most of the time
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Re: 300mm rear brake conversion
[Re: jimboy]
#1071525
18/07/2010 11:30
18/07/2010 11:30
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Joined: Dec 2005
Posts: 1,576 Glasgow,Near Florence..If only...
paul
My life on the forum
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My life on the forum
Joined: Dec 2005
Posts: 1,576
Glasgow,Near Florence..If only...
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i`ve got the Tarox rear conversion kit too,never had a problem with the rear breaking away under hard braking,but the brakes are definitely stronger,and as mentioned above, it provides you with a good handbrake too,only ever really available, to brand new coupes I think Jimbo means 4 tons alround braking effort
was Paul S,now just paul...Member since Oct 2000,Coupe may be FATALLY injured - :(oh no it's not
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Re: 300mm rear brake conversion
[Re: paul]
#1071543
18/07/2010 12:08
18/07/2010 12:08
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Joined: Dec 2005
Posts: 9,706 Gone
Jimbo
Je suis un Coupé
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Je suis un Coupé
Joined: Dec 2005
Posts: 9,706
Gone
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Hmmm maybe my 4 ton truck description wasn't so clear. On the brake effort rollers, my coupe has a total brake effort equivalent to the truck. I understand your non belief of the big disc conversion Neil, I too couldn't understand how it would work but by some sort of black magic, it does. Putting on my engineering head, I believe it's all due to the biasing valve. Normally when you brake hard, the front brakes will be providing 70% of the effort required to stop the car, that means the weight is transfered to the front causing the nose dive you always see. This nose dive results in the rear suspension to become unloaded and this unloading moves the arm on the biasing valve. On a big rear disc car, there is more effort provided from the rear so not as much weight transfer to the front, so the nose doesn't dive as much, the biasing valve, although still operating isn't limiting the pressure to the rear brakes and so more overall braking effort. That is certainly how it feels under hard braking, the car remains very neuteral without a large nose dive, the rears don't lock up as the rear end hasn't gone light through the weight transfer, most importantly, it comes to a halt very quickly indeed. The only way to demonstrate is to demonstrate really, have a go of a coupe with the conversion and feel your face elongate towards the windscreen, then park on a hill and apply the hand brake. It's sunshine indoors
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Re: 300mm rear brake conversion
[Re: Jimbo]
#1071563
18/07/2010 12:51
18/07/2010 12:51
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Joined: Mar 2008
Posts: 5,095 highlands
jimboy
Club Member 857
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Club Member 857
Forum is my life
Joined: Mar 2008
Posts: 5,095
highlands
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Good post there Jimbo.Fair points.
I'm an old git & happy with it,most of the time
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Re: 300mm rear brake conversion
[Re: jimboy]
#1071578
18/07/2010 13:32
18/07/2010 13:32
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jonone
Unregistered
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jonone
Unregistered
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Surely the lack of nose diving is also due to your coilovers, as the heavier spring rates will stop the pitch!
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Re: 300mm rear brake conversion
[Re: ]
#1071614
18/07/2010 16:03
18/07/2010 16:03
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Joined: Dec 2005
Posts: 9,706 Gone
Jimbo
Je suis un Coupé
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Je suis un Coupé
Joined: Dec 2005
Posts: 9,706
Gone
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Surely the lack of nose diving is also due to your coilovers, as the heavier spring rates will stop the pitch! It may have an impact but my springs aren't that uprated, probably the same as a set of standard Eibach springs. Lowered coupes still nose dive although not as much as a standard coupe.
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Re: 300mm rear brake conversion
[Re: Jimbo]
#1071654
18/07/2010 18:07
18/07/2010 18:07
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Joined: Dec 2005
Posts: 33,584 Berlin
barnacle
Club Member 18 - ex-Minister without Portfolio
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Club Member 18 - ex-Minister without Portfolio
Forum Demigod
Joined: Dec 2005
Posts: 33,584
Berlin
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Yabbut... I have *never* had a problem with the handbrake.
If the car is braked - from either end - then there *must* be a 'weight transfer' forwards. The mass of the car wants to keep going forwards, and it's being restrained by the brakes, so the mass of the car rotates around the point midway between the axles.
The point with the proportioning valve - if set up per the design - is that it's intended to reduce the overall brake pressure as that lift reduces the weight on the rear axle to the point where skidding is likely. There's obviously plenty of grip there on a fully working system, or it wouldn't be necessary to reduce the braking effort...
I'd still argue that if you're seeing a difference, you're seeing the difference between a working system and a non-working one, not a big and small brake disk.
That said - if your springs are harder at the front, or dropped in height, you will certainly change the dynamic of the vehicle. With a stiffer, and certainly with a lower, front end, there's not going to be as much dive at that end, and that means that the rear won't lift as much, so the pressure won't be reduced...
I'd love to do the experiment. Standard - but correctly set up - and modified discs, all else being equal. High speed camera, timers, accelerometers in three dimensions, and a nice long runway with room to spin...
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Re: 300mm rear brake conversion
[Re: barnacle]
#1071667
18/07/2010 18:36
18/07/2010 18:36
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Joined: Dec 2005
Posts: 10,728 N.E Scotland
mattB
Club member 6
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Club member 6
I AM a Coop
Joined: Dec 2005
Posts: 10,728
N.E Scotland
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I have the Tarox kit and have had for a few years. I'm pretty happy with it. It's quite expensive, but then two part discs are.
I will say though, that fitting bigger brakes at the front is one of the best things I've done to my coupe.
Death-rattle-tastic
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Re: 300mm rear brake conversion
[Re: reza_q]
#1071903
19/07/2010 11:03
19/07/2010 11:03
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Joined: Dec 2005
Posts: 1,985 In an Audi
Taffy20vt
My life on the forum
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My life on the forum
Joined: Dec 2005
Posts: 1,985
In an Audi
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Ex 432bhp '00 Sprinty 20vt6 '17 S3 Sportback '69 Amazon 131
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Re: 300mm rear brake conversion
[Re: Taffy20vt]
#1071927
19/07/2010 12:06
19/07/2010 12:06
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Nobby
Unregistered
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Nobby
Unregistered
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I thought you were looking at getting some rear brackets made up for the rears Adam - plus using an off the shelf bigger disc?
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Re: 300mm rear brake conversion
[Re: ]
#1071949
19/07/2010 12:55
19/07/2010 12:55
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Joined: Dec 2005
Posts: 2,588 Essex
Rog20VT
I need some sleep
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I need some sleep
Joined: Dec 2005
Posts: 2,588
Essex
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Group buy on Tarox rear brake conversions any one? Even coupes with a perfect working brake compensator valve have 'light' squirming when braking hard at very high speeds. The Tarox kit sorts that and does inspire greater confidence. Comes at a price though, and i dont think there is a 4x98 brake disc that can be used on the rear for a DIY upgrade.
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Re: 300mm rear brake conversion
[Re: ]
#1072061
19/07/2010 15:49
19/07/2010 15:49
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Joined: Dec 2005
Posts: 1,985 In an Audi
Taffy20vt
My life on the forum
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My life on the forum
Joined: Dec 2005
Posts: 1,985
In an Audi
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I thought you were looking at getting some rear brackets made up for the rears Adam - plus using an off the shelf bigger disc? Its in the pipeline, the pipeline just seems to be getting longer and longer......... Im looking at a vented rear set up using Seat Leon CupraR rear calipers and a 16vt front disks.Maybe
Ex 432bhp '00 Sprinty 20vt6 '17 S3 Sportback '69 Amazon 131
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Re: 300mm rear brake conversion
[Re: szkom]
#1072201
19/07/2010 18:11
19/07/2010 18:11
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Joined: Dec 2005
Posts: 33,584 Berlin
barnacle
Club Member 18 - ex-Minister without Portfolio
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Club Member 18 - ex-Minister without Portfolio
Forum Demigod
Joined: Dec 2005
Posts: 33,584
Berlin
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Neil, what I think is happening based on Jimbo's explanation is that the larger disc and hence greater lever arm are causing a greater torsional reaction between the hub pin and the trailing arm pin. In effect causing the rear of the vehicle to squat under braking.
It's very interesting as it's slightly counter intuitive as the C of G still moves forward. Not convinced, but I'd like to see the experiment.
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Re: 300mm rear brake conversion
[Re: Jimbo]
#1072202
19/07/2010 18:12
19/07/2010 18:12
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Nobby
Unregistered
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Nobby
Unregistered
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I think there was a group buy for about £450
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Re: 300mm rear brake conversion
[Re: DaveG]
#1072514
20/07/2010 01:31
20/07/2010 01:31
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ktm450exc
Unregistered
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ktm450exc
Unregistered
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mattb what set up did you use for the front?
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