Rear Brake Conversion

[David Sleith]

Started on the rear brakes last night so thought I would post up a few pics

http://www.twobrutal.co.uk/forum/images/recovered/2006/03/14.jpg

http://www.twobrutal.co.uk/forum/images/recovered/2006/03/15.jpg

[superchargedsam]

those are some spangly discs thats for sure !

[David Sleith]

Doh

Just realised I put the wrong side disc on the hub when I was trying to straighten the carrier bracket up last night.

[adamh]

heh i just realised that too.

is thata mk2 turbo rear conversion then ?.. you would be one of the very few that have done it, i'd like to see this one when done. hows the work? tricky?

[David Sleith]

Yes mate its a MK2 Turbo Revision 2 conversion

The job looked a bit tricky but it actually went pretty well and didn't cause too many problems.

I paid £70 for the discs on E-bay and a local VW fanatic who runs a machine shop took the centre bore out for nothing. You supplied the hub rings and I got the calipers for £55 delivered.

For the welding I changed my 0.6mm spool of wire that I had been using for the bodywork to a 0.8mm spool and cranked the dial round to max which is 200amps on my single phase machine and is about as high as you can get with a single phase supply. It kept tripping the MCB if I didn't strike the arc 100% right but the weld will hold forever I'm sure of that. I tapered the edges to get a deeper penetration and flush finish with a little grinding.

http://www.twobrutal.co.uk/forum/images/recovered/2006/03/16.jpg

The pic just shows the carriers in place without the calipers. I'm going to get some black caliper paint and a new seals kit. The rear calipers have a screw thread which the piston turns on and the best thing I had in the garage to remove them was an angle grinder key that you use to change the discs. The purpose of the screw action seems to be to activate the handbrake. When you pull the handbrake lever the screwed rod is pushed from the rear and moves the piston forward to clamp the disc.

And I have corrected my daft error from earlier using the wrong side disc.

[adamh]

excellent work david, i like the attention to detail chamfers for weld etc, and the replinishment of serious items!.. seals and pads/disks,.. a must have in my opinion. im not looking forward to refurbing my rear calipers, im going to keep them standard to save me some time, and sort out a turbo conversion on the bench etc at leisure.
so, the handbrake mechanism from mk1-mk2 caliper is literally the same?

[Paul Woods]

yep all the same adam,as a matter of fact a mk2T rear caliper will bolt straight onto a mk1 hub without any welding,same hole spacing on the rear! its just finding a disc that works.The full benefit can be had by using the 280mm corrados(welding) or bigger if you want!

Nice conversion david,im liking that.

[David Sleith]

Just got the rear brake kit from Brakes International. ?37 for both sides.

The pic shows what you get for one side

http://www.twobrutal.co.uk/forum/images/recovered/2006/03/22.jpg

[adamh]

good deal matey, runners included!, im definately going for this mod in the future. whats size discs you have?

[David Sleith]

VW G60 front discs - I think they are 280mm

Was speaking to a VW nut who is upgrading an old Jetta GTI this morning. He nearly had a canary when i told him i had G60 front discs on the back. He was a bit green with envy.

[Paul Woods]

its an excellent mod for sure,dont listen to those that shat their big girls pants over welding the caliper carrier,as david can confirm you can V the joins out and make such a solid job of it that it will never fail....you got to have faith in your snots!

[nik]

haha..
paul, do you fancy making some rear clappers up for me to bolt on my 1.5..
theres no way i can fabricate them out here in india..will pay handsomely for the job..basically i want to be able to hit the ground running when i get back in end may as time will be short, got lots of jobs to do to the 1.5 plus squeeze 2 south coast holidays, holiday at alton towers and a car show into 8 weeks back in the UK..would be great to be able to just bolt on some prefabbed clappers and disks..
interested..?..i know youre busy but thats never stopped you before..

[Jiff Lemon]

haha..
paul, do you fancy making some rear clappers up for me to bolt on my 1.5..
theres no way i can fabricate them out here in india..will pay handsomely for the job..basically i want to be able to hit the ground running when i get back in end may as time will be short, got lots of jobs to do to the 1.5 plus squeeze 2 south coast holidays, holiday at alton towers and a car show into 8 weeks back in the UK..would be great to be able to just bolt on some prefabbed clappers and disks..
interested..?..i know youre busy but thats never stopped you before..

You know, I was thinking the same thing.... My excuse is that I've no Snot making facilities.

[Paul Woods]

if theres enough interest how about i do a production run of these for whoevers interested,instead of paying me for each set i'll take a full day out and churn out 5 or 6 sets of modified turbo calipers that will bolt straight on with the corrado disc....then you can all club together and pay me a days labour which will work out a hell of a lot cheaper than individually.Usually i work for ?20 an hour which is pittance in garage labour terms,now i reckon if i got a little production run going i could maybe do as many as 5 or 6 sets in one day....at 8 hours labour for a full day that is ?160 divided by maybe 5 or 6 of you is going to work out at around ?25/?30 each plus postage?

I think the first thing to do is gauge interest,start a thread of how many would like modified carriers and take it from there? then the next step is everyone sends me the 22v coded carrier brackets (ive got the caliper body here so no need to post them up)....or if anyone else can think of an easier/cheaper way?

[superchargedsam]

Im in if I can find some carriers and calipers for sure !

[nik]

yup im in..finding clappers n carriers is gonna be difficult for me though..not many twos (none) in india..

[Paul Woods]

fear not sir nikalot :) i can get my hands on one set of 22v calipers,probably free ,got to see the guy first....you asked first so they are yours,hows that for service!

[nik]

marveloso splendido..

[Jiff Lemon]

Usually i work for ?20 an hour which is pittance in garage labour terms

OMG! If anyone is wondering how that compares, the local bodjit'n'scarper boys down here are charging ?80 an hour. Don't dare asking what the main dealers charge.

Paul, the moment I find some calipers, you've got my money :) (hell, I may even through a pack of hob nobs in!)

[Paul Woods]

deal!! the hobnobs clinched it.

[Rowdan]

Right, Welly had a set of calipers with his clip which if they were 22V he promised to me :tease: , so (when he turns up and if he is still selling them) i'm in.

[Rowdan]

Just a quick point that i'm sure someone will clarify. :shrug:
The calipers required, do they need to be tubby calipers as all mk2's from rev 2 on had the larger brake discs and 15" wheels didn't they???

[djdna2000]

I'm definitely IN if I can find the calipers. Cheers once again Paul, you're a star.

Which specific calipers am I looking for?

[Jiff Lemon]

Rev 2 onwards rear calipers - They're stamped with 22v (see this thread http://twobrutal.co.uk/showthread.php?t=2621 for an ebay link with pic)

[Paul Woods]

indeed as jiff says,they must have 22v stamped on them,rev2 onwards i believe.

Also i will need your old mk1 carrier brackets so that i can cut them up to make your new carriers,nobody needs to send calipers,just the mk2 22v carriers and the old mk1 carriers.

[rattymr2]

to bring this post up to date i have the mk2 rear conversion on m 1.5 and with the WMS front brakes i have not driven a better braked car. that includes my old integra type R on race pads.

the reason for this is the rear brakes balance the increased stopping power of the 4 pot fronts. The 195 tyres on the car have proved to be very difficult to lock up even IN THE WET and with a warped rear disc.

i need to put a new pair of discs on which when i tried previously wouldnt fit. i understand i need to machine the inside of the disc mount a little and put a spacer in there to move the disc over to line everything up. i have seen a guide to fit the disc but have lost it. can anyone point me in the right direction. the car is in at 3S and fitting the discs is an item i would like them to do.

thanks

[Rowdan]

Was the guide in Garys' build diary?

http://www.mr2mk1turbo.co.uk/diary33.htm

[rattymr2]

thats the one. no mention of the size spigot ring so hopefully my old discs will have them on.

thanks mate

[weegaz22]

thats the one. no mention of the size spigot ring so hopefully my old discs will have them on.

thanks mate


send adamh a pm, he might be able to tell you as im sure david said it was adam that machined the rings on my car:thumbsup:

[rattymr2]

spigot rings appear to be used in two places now. inside the disc hub and inside the rim itself. i will chat to James at 3S and see if he can source some.

buck passed!

[snowtigger]

was looking in to this conversion has anybody got a set of 22v calipers and carriers going spare .

[rattymr2]

best upgrade to the brakes is to balance the rears. makes such a big difference.

[TobyA]

best upgrade to the brakes is to balance the rears. makes such a big difference.

i agree with you, ratty.

with the standard bias i can't imagine that the rear brakes would actually suffer from fade (but i'm open to correction cos i've not yet abused mine on a track). obviously bigger discs and better pads will increase rate of braking for a given cylinder pressure, but will the benefits of cross grooved/vented/drilled discs be of any use with a standard hydraulic bias?

[Paul Woods]

lets not forget an mr2 has a 55/45 front to rear brake bias,which is a lot more rearward acting than most cars which have 75/25... so modding the rears is quite important on an mr2.

The americans have been known to gut the bias valve in the frunk so that it ends up having a 50/50 bias,ive never done this but its supposed to be a good mod.

[rattymr2]

Toby,

you dont own my old car do you?

[biteme]

The americans have been known to gut the bias valve in the frunk so that it ends up having a 50/50 bias,ive never done this but its supposed to be a good mod.

Just make sure you have slightly bigger, more effective braking on the fronts then!

[Jim-SR]

Just make sure you have slightly bigger, more effective braking on the fronts then!

with the way the weight distribution is and the "need" (not my personal thoughts, but the way the car drives as standard it does need something to loosen the back end up) for more rear braking as standard anyway you can get away with it a lot more than you can on a front engined car. especially if you go stiffer on spring rates and reduce the weight transfer further (which isnt huge to begin with)

most of the guys in the states are stupidly stiff on spring rate, with japanese spec dampers loaded with rebound damping and sod all bump, so the front doesnt dive due to stiff springs, and the rear doesnt sit up due to too much rebound damping, and you end up with the tyres being the limiting factor much more than the braking. truth be told you could get a lot more braking performance with smaller brakes and the suspension setup properly.

personally id prefer a bit more braking bias on the front, combined with a bit less weight transfer than standard, but enough not to negate the benefit completely. but most people dont have the benefit of cheaply revalvable dampers, and for an MR2 with macphersons all round its a touch pricey unless you work for a company that makes dampers lol

[rattymr2]

group buy coming up then Jim?

[keri-WMS]

Limiting the line pressure to the front is a really bad idea, most "bias valves" are really a "stepped action flow limiting device" which is a sprun loaded plunger/bung with a small (low flow rate) hole in it, and adjustment is only changing the pre-load on the spring.

Fit smaller piston front calipers instead, or a bias-bar pedal box, or bigger rear pistons and a bigger master cylinder.....

[Jim-SR]

group buy coming up then Jim?

if it were up to me i probably would. there are 2 problems though...

1. the mk2 struts are badged up as Ohlins, but arent actually made by them. theyre made under license by a company in Japan called "Soqi", who due to some politics when Yamaha bought out Ohlins years ago were allowed to manufacture dampers under license. theyre 90% as good as Ohlins in terms of damping, but about 30% of the quality control. but still better than most stuff you can get, and definitely better than everything else in their price range.

the issue here is that Soqi hate everyone (or so it seems), you cant get their product from ANYWHERE, the only people who sell it are the Japanese Ohlins distributor (good luck, many have tried, many have failed), and Ohlins USA (same again), and im not even sure that mk2 MR2 kit is still being produced anyway, although i beleive mk3 stuff is, and that it also fits with minor modification, not sure though.

2. the standard valving in the dampers is pretty cráp, and theyd need a revalve (or if theyre used theyd need servicing as well). a revalve is easy to do and on brand new builds would basically be free (IF we could source the dampers!! and if we could a set would probably cost £1200-1800 at a guesstimate). however a service on 4 used units would set you back between £400-700, assuming the chrome tubes arent damaged which they often are, and then its an extra £150-200/corner!!! e.g. it costs as much to repair them as it does to replace them if the chrome tubes are damaged, and they almost always are unless the struts have been really well looked after. we replace them with genuine Ohlins tubes though and then they last 3 times as well!!

so id love to do a group buy, but the lack of product availability combined with the expense combined with me not owning the company and not having a say in such a discount means it probably couldnt happen :(

if i can source brand new sets of mk2 stuff though (which i am trying to do) then il gladly offer such a deal where id sell the kit on at cost price plus a nominal fee for the labour and parts used in revalving them (so would probably be cost price, using a favourable dollar exchange rate, plus about £50/corner). il hopefully be able to find some stuff out next month

anyways, sorry to totally hijack this thread with irrelevant ramblings about Ohlins dampers!!

[Tom G]

Limiting the line pressure to the front is a really bad idea, most "bias valves" are really a "stepped action flow limiting device" which is a sprun loaded plunger/bung with a small (low flow rate) hole in it, and adjustment is only changing the pre-load on the spring.

Fit smaller piston front calipers instead, or a bias-bar pedal box, or bigger rear pistons and a bigger master cylinder.....

that's interesting, I was going to stick an adjustable bias valve on the front if my mk2 rears didn't give enough power... hehe I might end up swapping the st165 calipers for the std ones!

I gutted the stock bias valve last weekend:
http://www.twobrutal.co.uk/forum/images/recovered/2008/03/86.jpg
made a decent difference, along with mk2 master cylinder.
Some maths: Std mk1b rear calipers have a piston area of 1040mm2 and mk1b front are 2050mm2, so even without the valve the brakes are still 66% front. add st165 calipers (at 2864mm2) and bias changes to 73% front. put on mk2 rears and it's back to 66% front

[Icsunonove]

Some maths: Std mk1b rear calipers have a piston area of 1040mm2 and mk1b front are 2050mm2, so even without the valve the brakes are still 66% front. add st165 calipers (at 2864mm2) and bias changes to 73% front. put on mk2 rears and it's back to 66% front


Exactly. And in my opinion there's too much bias towards the front anyway. So adding larger x-cross sectional area at the front makes the whole thing worse. So in my opinion it's either change all the calipers or change none. I've gone the other route and kept the standard calipers and bought Carbotech XP8 pads. They're excellent but they should be at £200 a set!

[keri-WMS]

Don't forget there are more factors to remember when making sweeping statements...

1 - Wider front tyres give more surface area = more "static" friction (grip). "Sliding" friction is not affected by contact area because it's defined as "friction = pressure x coeficient of friction of the material"

2 - Better suspension will also increase grip.

Take factors 1 + 2 and you can see that you can brake harder before losing traction if you have uprated wheels/tyres/shocks. This creates:

..factor 3 - An increase in the forces acting "forwards" on the chassis as it tries to maintain speed. This creates an increase in the "weight shift" and bodyroll to the front under maximum braking, and you've suddenly got an even greater amount of grip at the front (and less at the back).

So, the short version for non-standard cars: Wider tyres and better shocks = more grip all round = higher possible braking forces = increased weight shift to the front = more grip at the front and less at the rear = a need to INCREASE front bias. (in some cars)

:hidesbehi

[Icsunonove]

Cheers Keri. I do understand all that but trust me I really could do with some more bias towards the rear. At the Toyota Sprint thingy it was hopeless on the brakes in the wet. Obviously as it dried up it was better but even when it was bone dry I STILL needed more bias towards the rear.

I don't know how to go about this as there doesn't seem to be anything off the shelf I can use, so it's going to be mega expensive....

[Tom G]

hi tom, I also had way too much front bias. If you still have standard front brakes, and you've already removed the std bias valve, you can increase rear bias cheaply by putting on the 22V rear calipers, I'm hoping they'll go on OK with 5mm washers instead of spacing the discs.

[keri-WMS]

I don't know how to go about this as there doesn't seem to be anything off the shelf I can use, so it's going to be mega expensive....


What we need is this kind of thing but servo-mount:

http://images.google.co.uk/images?um=1&hl=en&q=bias+bar

...maybe from here...

www.demon-tweeks.co.uk/products/ProductList.asp?cls=MSPORT&grp=MP177&pgrp=M008&tlgrp=MS002

http://www.demon-tweeks.co.uk/resources/images/zoom/ISA3344.jpg
http://www.demon-tweeks.co.uk/products/ProductDetail.asp?cls=MSPORT&pcode=ISA3344-0

or

http://www.demon-tweeks.co.uk/resources/images/zoom/ait_C26PEDALBOX_SERVO-BRAKE_08.jpg
http://www.demon-tweeks.co.uk/products/ProductDetail.asp?cls=MSPORT&pcode=AITC26
maybe....?

[Icsunonove]

Thanks very much for replies both. :thumbsup:

Tom, during the sighting laps I was very lucky that the person behind me left a huge gap. So I took the opportunity to find out how much extra pressure was needed after the fronts locked to make the rears lock. And the answer was absolutely loads! :banghead:

Keri, thanks for your post. But that is going to cost an awful lot of money.:sad:

I *think* I will check out how much it would cost to rebore my standard calipers and have some special pistons made (with standard sized main seals). That won't be cheap either but if I guess right with the sizes it may be a worthwhile mod to a few people.

[snowtigger]

any one tried an adjustable brake bias propotioning valve then so u can ajust the front to rear pressure, look at the other rear brake thread of 22v rears and aw11 front disks.

[keri-WMS]

any one tried an adjustable brake bias propotioning valve then so u can ajust the front to rear pressure, look at the other rear brake thread of 22v rears and aw11 front disks.

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