Rear brake combo with 266 front

[Arthur 12]

Hi all

 

I'm about having to change my discs at the front. I have a couple of 266 calipers collecting dust so I might go 266. Thinking to add upgraded pads, like EBC green stuff, while I'm at it. It's not a race car. Let's call it a fast road old-timer. 

 

I'm wondering though what is the best at the rear, since I have read upgrading the front in return means the rears get less pressure and so actually also need more oomph.  I also plan to upgrade the rear somewhere in the future. I also have several lengths (306) stub axles lying around. Would like to get it one time right. Are there any proven combo's with a good balance? 

 

I have C5 alu "steelies" so I do not need discs at the back for the looks. 306 drums might be fine option in that sense. Maybe it's best to overdue the rears and then add a rear comparator that is adjustable? (if that's not a huge cost) 

 

What I have now:

Cast steel master cyl with 4 brake leads. (Dunno the diameter, probably standard 1985 Lacoste)

9 inch 306/205 Euro GTI, left hand drive, booster (the left hand drive has space for a 9 inch booster) 

247 x 20 front on standard pads (base model hubs)

Phase 2 (the bigger) 205 rear drums.

No rear compensators

I'm no F1 driver but he balance on this setup feels fine to me. It could do with a bit more bite though. 

 

What I'm planning to do

Keep the cast steel master cyl with 4 brake leads

keep the 9 inch booster

266  x 22 discs with greed stuff pads

306 drums??? (with or without comparator )

205 rear dics???

306 dics rears (with or without comparator )

 

Edited November 30, 2022 by Arthur

[DamirGTI 342]

For 1.6/1.9 8v std. or mild engine tuned 205 , std. brakes are good enough for road driving (1.9 system front-back) .

 

I'm daily 205 driver for some 20 years now , had the engine and whole car in various state of tune though the years and std. braking system never failed to stop me (people say i'm a bit "harsh" driver .. never had a crash with a 205 though !) .

 

It's an light car to begin with , so it doesn't need much braking force .. certainly not at the back .

Actually , when speeding and if not careful with the braking application , you'll lock the brakes sooner than you'll slow it down to a steady stop - spend the money on some good quality rubber (tyres ! buy the best ones ..)

 

Bigger thus heavier brakes adds unsprung weight on the entire suspension , which personally i always try to avoid if not necessary .

 

If you're missing some better braking response and pedal "feel" , rather than going bigger which costs and adds weight , better invest in braided brake lines , better pads (try Ferodo DS , Carbone Lorraine RC5+ or similar) and better disc (slotted , or combo drilled-and-slotted discs .. avoid "full" racing purpose drilled though as they need to be often inspected and replaced due to crack formation .. slotted are best for road use)  but all in the std. size . And as said buy the best tyres .

That's what i would do ...

 

D

Edited November 30, 2022 by DamirGTI

[Kobayashi 35 2 Cars]

This stuff might be pretty subjective, so if you want a somewhat different opinion/experience: I upgraded from 247 to 266 fronts and from drums to standard disc rears last year on my own 'fast road oldtimer' (i like that ) and it was one of the BEST and most noticeable modifications in more than 20 years of 205 ownership (and I did plenty).

I also added a fresh, but standard master cylinder and an adjustable pressure limiter for the rears. I had been using braided brake lines before with the 247s and upgraded discs and pads, however it hat very little effect, compared to the 266 which i would see as being the optimum for any fast road applications.

[petert 586]

I agree. 266mm are great, with either rear 205 or 306 discs. They're almost identical, except for GTi6. I prefer the 22mm four master cylinder from a 306.

[Arthur 12]

Oké. I have 306, 137mm (dics) stub axles on the shelf, so 306 disc at the rear should be relative easy conversion. If that's a good combo with 266 fronts. 

 

Are 307 or 206 rear disc the same or should I look out for a 306 rear disc at the scrapyard? When I look at some parts catalogue my current master is 19,05 or 20,64 mm so I could source the master from the same 306 if I can find one with 4 outlets. 

 

Edited December 1, 2022 by Arthur

[petert 586]

You'd fit a 2nd hand master cylinder? I'd probably always fit new with that.

[Arthur 12]

Good point. Didn't even consider that to be honest. 45 euro's is not worth the headache.

Edited December 1, 2022 by Arthur

[SRDT 175]

The big master cylinder upgrade (23.8mm) is the one from the 406 without ABS but maybe 266mm brakes are a bit small for it.

All 306 mk2 should have bigger bore rear calipers like the GTI6.

[pug_ham 244 3 Cars]

A 22mm master cylinder with four ports is from a 405, I've got one on a car I'm building but you need to alter the length of the pushrod in the servo iirc so it works best.

 

g

[petert 586]

18 minutes ago, pug_ham said:

A 22mm master cylinder with four ports is from a 405, I've got one on a car I'm building but you need to alter the length of the pushrod in the servo iirc so it works best.

 

g

Also from a 306 with 266mm brakes.

[Arthur 12]

Only thing is I believe the 306 is at 45 degrees angle. My booster is a 306 one. I bought it and opened it brand new to close it back up 45 deg turned. This pod was 60 EUR while the 9 inch 205 gti pod is 200 EUR. On the left hand side the bulkhead has a dome to fit 9 inch booster while the right hand side does not, so I think 9 inch is not an option for RHD. But I can undo that if needed. Is the angle not an issue for RHD? 

 

 

Edited December 2, 2022 by Arthur

[Arthur 12]

I have read a bit more all over this forum. My current setup 1 can find no compensator whatsoever, but I'm pretty sure I have the bigger drums of the 1.6 gti. Does that mean there is a compensator in the drum and I can check that with my union being 13mm? 

 

Quote:

 

"These can be easily identified by the size of the brake pipe union going into the backplate on the drum into the wheel cylinder, if it's a 10mm union then you have a separate compensator elsewhere inline but if they are a 13mm union, they have the limiter built in."

 

Ifso, converting the rear to disc would mean I have no limitation to the rear after conversion, which in turn mean I will have too much pressure to the rears? Or will the 266 in front balance that back to about neutral. Ending up with too much rear pressure wouldn't really mind when I add an adjustable racy aftermarket compensator balancer thingy imo. Maybe a bit over overdone for a street car, but oké. How do you mount those anyway? Just drill a whole in the bottom and get the knob inside but leave the business part out? (did that sound like I think it does?) 

 

I could very easily stick on the 266's front with current setup and see what that bring me. I've ordered Brembo 266's with groves now. (09.8695.75) and the calipers I have on the shelve are fine with almost new standard pads. this will be my stating pint then. 

 

Edited December 2, 2022 by Arthur

[Kobayashi 35 2 Cars]

I am just realizing that what you intend to do is very, very similar to what I did 1 or 2 years ago. I am not saying that you nee to do the exact same thing, but I'd like to offer any Information (including my conclusion in the last post) that was collected back then: 

 

[Kobayashi 35 2 Cars]

1 hour ago, Arthur said:

 Ending up with too much rear pressure wouldn't really mind when I add an adjustable racy aftermarket compensator balancer thingy imo. Maybe a bit over overdone for a street car, but oké. How do you mount those anyway? Just drill a whole in the bottom and get the knob inside but leave the business part out? (did that sound like I think it does?) 

 

Here is how i mounted the limiter - hiding away in the engine bay,   behind the battery, yet accessible when you need to adjust. The holder is a custom one.

[Arthur 12]

Quite similar indeed only I have two lines to the rear. I’d need two or a double one and some re routing. I guess this means I can go in steps. 266 front and 247 rear without comp. If the rears bite too hard I could increase front capacity with better pads an so reduce the presumptive to the rear. On the other hand, I think a perfect balance on dry would make the rears lock up in the wet. I think that’s the reason for the weight transfer compensation. One can either give up some rear capacity in the dry and be safe in the wet, OR add compensators the increase capacity rear on higher transfer in higher grip. Again maybe overkill for the streets but a knob or leaver next to my seat to a double compensator sound like the best option. 

[pug_ham 244 3 Cars]

On 12/1/2022 at 9:39 PM, petert said:

Also from a 306 with 266mm brakes.

They are but the 405 is a better source imo as they didn't have the servo flange at an angle on some later models so there's less chance of getting the wrong one that won't fit onto the 205 servo.

 

Although if Arthur has a 306 servo with the studs at 45', he'll obviously need one from a 306 to suit.

On 12/2/2022 at 7:34 AM, Arthur said:

Only thing is I believe the 306 is at 45 degrees angle. My booster is a 306 one. I bought it and opened it brand new to close it back up 45 deg turned.

 

20 hours ago, Arthur said:

I have read a bit more all over this forum. My current setup 1 can find no compensator whatsoever, but I'm pretty sure I have the bigger drums of the 1.6 gti. Does that mean there is a compensator in the drum and I can check that with my union being 13mm? 

 

Quote:

 

"These can be easily identified by the size of the brake pipe union going into the backplate on the drum into the wheel cylinder, if it's a 10mm union then you have a separate compensator elsewhere inline but if they are a 13mm union, they have the limiter built in."

Not quite, the 1.6 GTI has a 10mm union into the wheel cylinder on the drum plate with the compensater on the l/h chassis leg in the engine bay.

 

Only the wheel cylinders with a larger 13mm union have the compensater built in which are fitted to lower spec models generally.

 

g

[Arthur 12]

Well mines a French 1.4 lacoste. Someone put it on gti front but the hubs are standard. Rear beam is also not standard most prob

[Ryan 99]

On 12/1/2022 at 9:20 PM, pug_ham said:

A 22mm master cylinder with four ports is from a 405, I've got one on a car I'm building but you need to alter the length of the pushrod in the servo iirc so it works best.

 

g

Do you remember what you need to do to the pushrod? (is there an adjustment spec anywhere). I've got a 266mm setup from a 306 and a 22mm m/c I've been meaning to fit for years...

[pug_ham 244 3 Cars]

10 minutes ago, Ryan said:

Do you remember what you need to do to the pushrod? (is there an adjustment spec anywhere). I've got a 266mm setup from a 306 and a 22mm m/c I've been meaning to fit for years...

IIRC it's on here somewhere, I can't remember if its lengthen or shorten the rod tbh.

 

If you have a some of vernier calipers you could measure the new m/c and compare the depth of the plunger to the 205 one and the adjust the servo rod to suit.

 

g

[petert 586]

It just needs to have freeplay. If not, the brakes keep applying and never come off. 

[Arthur 12]

Can’t remember checking it. I just bought a 9 inch 306 booster, pulled it apart and remounted it 45 deg rotated. Works a treat. 

[pug_ham 244 3 Cars]

11 hours ago, Arthur said:

Can’t remember checking it. I just bought a 9 inch 306 booster, pulled it apart and remounted it 45 deg rotated. Works a treat. 

The 306 came with the 22mm master cylinder as standard on certain models so you only need to alter the pushrod when fitted the 22mm m/c to a 205 servo.

 

g

[Arthur 12]

Yes. But it’s a cast iron 205 MC in a 306 45 deg rotated servo. So would the rod be too short now then? What if one would add something like this under the bonnet and then cable operate that from inside? Would that work? 

[wicked 103 3 Cars]

That compensator is designed for the 306 to have load dependent braking at the rear (attached to rear beam; reduce pressure when rear is lifted).

Why don't you just add fix rate 205 compensators and job done...?? 

205's don't need much brake pressure at the rear and you certainly don't want to run without, because on that one rainy day they will lock up unexpected...

 

I you go with discs on the rear and have 2 lines to the rear, just use 1.9 Gti compensators in the lines. If you have single line to the rear, use the 1.6 gti version with the correct tilted bracket. 

Both available local:

https://www.retro-lion.com/c-3956689/brakes/ 

 

The increased size of you front brakes have only limited impact on the rear; before you can tell the diff between 266 and 247mm discs, the 1.9 rear limiter is already active. 

FYI I run 4 pots brembo's on the front on all 3 205's and all have stock limiters on the rear. Only for my trackday 205 I consider to add adjustable brake limiter on the rears, but only to allow more pressure on the rears to be able warm up the rear tires quicker. 

 

If you insist on adjustable, do it like Kobayashi did..

Edited December 5, 2022 by wicked

[Arthur 12]

I don't really insist. Just that I would prefer adjustable when that's almost the same price and maybe easier. But this is also why I consider keeping my drums when they have build in compensators. Or maybe go 306 drum if they have compensators in them. As you say, a system without compensators might not be wise in wet weather. But if increasing the front capacity does not reduce the pressure to the rear that much, even with quite good fronts, then indeed standard compensators should be fine. Let's say the front needs 20 bar and the rear compensators already limit 10 bar. I don't know the figures. But let's say that's true, one could double the front capacity without problems. 

 

Let's see what the 266's do first.