280mm rear disc conversion.

5 years 1 day ago #50931 by cjj
I won a 280mm disc and conversion set for the rear brakes for £132 on e-bay and I thought I would trial it for you and see what difference it makes.

I won the conversion kit from this ebayer http://myworld.ebay.co.uk/evthinmustgo/

Is it a bargain?

Well, VHS do a 266mm brake conversion kit for around £395.50.

So, if they work as planned then they are slightly better and cost £263.50 less.

They allow you to keep your current calipers while increasing braking torque and thermal dissipation. This does away with problems involving the hanbrake mechanism etc that you may get if you change the calipers.

I will tchange them first with no change to the front brakes or the pads and see how it compares. I will then be fitting my new bargain EBC drilled and grooved discs and greenstuff pads all round and see how that does.

Hopefully I will be able to give you some sort of advice on whether it improves braking or not.

It is also designed to fit under 15" wheels as well.

These are the discs and spacers. You also get spigot rings and stainless bolts etc.





The discs are Ford Focus ST170 rear disks machined to fit the pcd of the F/TF.



Fitting was easy

These are some before shots.







And with the wheel removed.



With the old disc removed you can see the difference between the new 280mm and the old standard 240mm.



and you can see the difference in offset between the discs. The new disc is shallower so sits further into the wheel.



With the old disc removed, and the hub cleaned up, the first thing to do is fit the spigot ring. This holds the disc central and stops wheel imbalance at high speed. The spigot ring needs to be fitted with the recess facing the hub.



The next picture shows how the carrier extension block bolts to the hub.

They are handed and the stepped part should face you with the narrow end of the step at the top. We do not fit this yet as we need to bolt it to the carrier.



Fit the disc onto the hub, using the retaining screws, (The supplied screws are shorter and allan headed, but are very soft. I will be cutting my stainless ones to size and using them) bolt the extension block to the caliper and bolt into place.





And with the wheel fitted you can see the difference. Even if it doesn't give better braking I am glad I did it just for the better looks.







For those who like proof and statistics I had them tested before and after the mod. Note, the same pads were used for both and were bedded in for around 60 miles on the new discs. Will probably get better with further bedding in, but I will be fitting Greenstuff pads soon.

I would also like to thank Kwikfit of Ashington for doing the tests for free and allowing me to photograph the results.

So, here are the results

Pre mod



and post mod



as you can see, that is an increase of 60kgf braking force per side, or an increase of rear braking of more than 33%

Also, for those who like pics, here is the before



and here is the after



Well worth it even for the looks, let alone the increase in stopping power.


My next job is to fit these to the front:



and these all round



Will let you know how it goes.

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5 years 1 day ago #50932 by cjj
This conversion was done in Feb 2010.

I ran the brakes for over a year and was extremely pleased with the braking advantage that it gave.

However, due to the extra heat generated, or the crap Rover calipers, the discs started to warp.

I have now gone back to standard but I am toying with 304mm vented discs and 4 pot calipers on the back.

I will update if I ever do this.

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5 years 1 day ago #50935 by Leigh Ping
Have you noticably missed that amazing 33% improvement at all?

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5 years 1 day ago #50936 by cjj
Oh yes.

Which is why I want better.

The coversion was good, but the weak point was using the old standard calipers which aren't brilliant and don't age well. The brake distribution, even between the 2 pads on the same caliper is crap. This is a downside of single pot calipers.
The following user(s) said Thank You: bryan young

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5 years 1 day ago #50950 by bensewell
Wow shame it didn't last

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5 years 1 day ago #50958 by bryan young

cjj wrote: Oh yes.

Which is why I want better.

The coversion was good, but the weak point was using the old standard calipers which aren't brilliant and don't age well. The brake distribution, even between the 2 pads on the same caliper is crap. This is a downside of single pot calipers.


When you think about it, those rear "crap" callipers started life in 1984 on the rear of the Rover 800 stirling :rant: Yet more of the MGR parts bin special :slapme:

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5 years 18 hours ago #51071 by Rich in Vancouver
Did you ever try popping on a 15" wheel to see what the clearance was like?

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4 years 8 months ago #70568 by Edunit
The only warping on discs I have ever experienced has been due to the disc design/material but I suppose if you pressurise it - in the extreme - on one side only, something's got to give. I am interested in fitting 280s to my car (old 1.8i) - is there any way to improve the 'slide-ability' of the existing caliper?
Also, I have bought a pair of 160 four-pots on fleabay - could you tell me what mods are needed (got 16s)? Does it need a m/cyl change?

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4 years 8 months ago - 4 years 8 months ago #70578 by GOLDIE
:-? Wouldnt a bigger disc, disperse the heat more, and would a vented disc be better?

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4 years 8 months ago - 4 years 8 months ago #70583 by cjmillsnun

Edunit wrote: Also, I have bought a pair of 160 four-pots on fleabay - could you tell me what mods are needed (got 16s)? Does it need a m/cyl change?


I don't know which 16" wheels you have, but IIRC you need to have either

Trophy 160 wheels
MG TF 11 Spokes
Swedish wheels
Abingdon Wheels (with a small spacer)
Multispokes

otherwise the calipers won't fit.

Apart from that it's a straight swap. Nothing required except callipers, pads and discs.
The following user(s) said Thank You: PQD44

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4 years 8 months ago #70622 by cjj

Edunit wrote: The only warping on discs I have ever experienced has been due to the disc design/material but I suppose if you pressurise it - in the extreme - on one side only, something's got to give. I am interested in fitting 280s to my car (old 1.8i) - is there any way to improve the 'slide-ability' of the existing caliper?
Also, I have bought a pair of 160 four-pots on fleabay - could you tell me what mods are needed (got 16s)? Does it need a m/cyl change?


The best and only real way to optimise the rear brake calipers is to keep them maintained 100% with regular stripdown and cleaning.

As far as I know the master cylinder is the same whether you have standard calipers or APs.

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4 years 8 months ago #70624 by cjj

GOLDIE wrote: :-? Wouldnt a bigger disc, disperse the heat more, and would a vented disc be better?


Apparently not. The vented discs disperse heat better, but also resist warping due to the nature of their construction.

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