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Arthur

brake option for rear

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Arthur

Hi all

 

Probably the google-st topic about this but I can't find info for me specifically. I'm doing my rallye arches atm, and will end up with quite some extra room in the rear arches. I will be rebuilding the complete inner arch skin to make max use of the extra room. Now thinking ahead this will give me 20 to 25 mm each side to widen the track. It's not a racer, but I do have 150 ish bhp and do like a car that doesn't roll to much. Looks do matter to me as well. 

 

Front I have 1.9 disks with base hubs and 1.6 shafts. I don't know whether the shafts will keep up, but if they don't, I might be going 82mm hubs with 1,9 shafts, but then I'm thinking to add the 309 arms or something different while I'm at it. I don't need to go 283mm disk imo, perhaps 266 would be nice, or keep the  247 with a good patch.

 

But now the option on the rear. I have no clue what's on the back. Drums seem 40mm, but I don't know. Don't know anything about the rear beam. Can I measure the bars to confirm what I have? It's an 1985 so I might be having the "very very old" beam that  doesn't mix with other trailing arms. 

 

But now the question. What would be the easiest what to change the back track and perhaps gain some camber, toe and brakes performance? Of course wideners are the easiest option. The bettered front braking will result in less pressure at the back, so better front brakes make the rear worse, right? 306/7 HDI is quite common here. Could I get trailing arms of a 306 and kill 3 birds in 1 go? 

Edited by Arthur

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Tom Fenton

306 trailing arms are easy to fit and give 9mm per side track width and if you get the right ones disc brakes. However the drums are more than good enough for the braking effort that is actually required.

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Arthur

Hmmm. 9mm might not be enough. I have the C5 alu "steelies", so I don't see the drums anyway. That's not a reason to go disks from ecstatic's point of view. But if the arms come with disks and the lot... I'm even thinking I will go 306/7 hubs in the front with 306/7 shafts and (a lot) longer front trailing arms. I don't know how the camber will be when you do this. One loses 1 deg camber from the hub, and then gains it back from shaft being 20mm or so longer. But that would make I need only 1 306/7 hdi for a donor for about all I need. 

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petert

Isn't this a race car? 306 arms kill the 205 "feel" due to the extra toe-in. By all means buy some 306 arms, as they're cheap, but get Bridgecraft to re-machine them for zero or positive toe, -ve camber and get longer stub axles at the same time.

 

Edited by petert

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Arthur

No, it's not a race car. It's a fast oldtimer, intended to be a rallye lookalike, but with a better (imo) engine (tu5jp4s on itb's). No slicks, long gearbox (still wheelspin in 2nd in wet).

 

So I'm really not sure whether the front driveshafts will cope. Might just as well. And I'm after a decent handling, nothing extreme. I think it rolls quite a lot, but I don't know other 205's. It does roll more then the lowered 106 ralley that I had. A lot of inner wheelspin off the apex. But I do have about 180 Nm of torque I guess. But the corner speed seems quite normal, apart from it feels like being on 3 wheels. I just went BS b4,s and eibach spings and that seems good enough for me. It's just the things I might change for the better "while I'm at it" that I want to think about. 

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Arthur

just measured my torsion bar at 21 mm

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Arthur

When you do take a 306 disk arm, and slap on 205 drums, will the longer sub axle from the 306 make it so I can add a 11mm (ish) spacer in between the arm and the drum so get 20mm track increase from 306 arms with 205 drums? 

Edited by Arthur

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welshpug

that will not work as you will move th drum away from the brake shoes, you need to fit the 205 stub axle.

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Arthur

Even when you put a spacer between the drum and the arm? One would move the whole drum assembly imo

Edited by Arthur

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welshpug

there are no spacers for the backplate.

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petert
10 hours ago, Arthur said:

No, it's not a race car. It's a fast oldtimer, intended to be a rallye lookalike, but with a better (imo) engine (tu5jp4s on itb's). No slicks, long gearbox (still wheelspin in 2nd in wet).

 

So it's not a race car but you still want it to go around corners properly? I'd still do either

as I suggested 

or

fit 306 brakes, stub axles etc to your 205 arms

or

fit 306 brakes etc to your 205 arms with longer stub axles from Bridgecarft

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Arthur

Thanks. Obviously I need to make spacers if I go that route. I will finish the work on the arch first to see what I need. 

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petert

Spacers? No. The point of having longer stub axles is to alleviate the need for spacers. They are the devil's tool. Adding camber to the rear needs longer stub axles if you're running big tyres.

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welshpug

you really dont need to go wider on the back, you dont see people doing stuff to the 106 do you?   that is 40mm narrower than a 205!  but the same width on the front to the mm..

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welshpug

sort the front grip, make sure the rear is balanced to the front, the rear will follow.

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Arthur

Yeah, It's also the looks to be honest. Let's see how that turns out. Tires were rubbing the standard body wheel arch. The (fake) rallye arches are about 20mm wider by the looks of it. So the 306 arms might be enough, but will give a pro on camber, but a con on toe. Have read a bit more, and the sharper 205, (low camber low toe) setup on low speed, does sound better to me then the 306 setup (more camber and toe) creating better high speed stability. I would prefer the first. 

 

Are we talking the same spacers here? I know spacers at the wheels will increase the load on the bearings, Why is the 306 stub axle longer? Does it stick out more, or is the part inside the arm just longer?

 

My idea was to perhaps use 306 stub axles in the 205 arm, and then use the extra 12??? mm to sandwich a spacer between the arm and the drum. NOT between the drum and the rim.  I could even use alu, because the load will still be on the stub axle and not on the extra long bolts I would need. "My" spacer would just be sachwiched in between the drum and the arm. Or is there something crucial I miss? When using longer stub axles and disks one also needs some spacer rings to rest the bearing to, right :unsure:

 

I have a lathe, so drilling 25mm axle hole and 4 bold holes in an alu plate would be easy. Obviously that would not give me more camber, only  more track. It's not needed, but I guess it won't hurt much either. So only for the looks that might be a cheap solution. Just need 2 306 sub axles, a 12 mm spacer (make that myself) and 8 longer bolts. 

 

175659278_3934413209971109_6506925687086

 

 

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jord294

Extra width you can go 309 axle and also use the 205 gti spec drums. 

 

But all honesty, std width with refreshed axle and the right bar set up, and it will be spot on anyway

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Arthur

Oké, so all in all only the looks remain. Let's see how it looks. I do think the standard rallye looks a little bit to much arch for the wheels they run. But I run the C5 alu's (6j ET18) with 195/50/15.

 

309 axles are like rocking horse sh#t around here. 

Edited by Arthur

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jord294
3 hours ago, Arthur said:

309 axles are like rocking horse sh#t around here. 

Where's here? I have about 6 in my workshop

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Arthur

The Netherlands 

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wicked

If it is only for the looks, just fit 20mm spacers (between drum and rim); job done.

The 306 has wider bearings because of the abs ring. In theory you will load the bearing a bit more with 20mm spacers on 205 drums/stub, but in practice you will not notice significant difference in lifetime. 

Given the rest of the spec, I think -ve camber on the rear is not the first thing I would spend my money on, as it does not come for cheap. Would first get the front sorted...  

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petert
14 hours ago, Arthur said:

Are we talking the same spacers here? I know spacers at the wheels will increase the load on the bearings, Why is the 306 stub axle longer? Does it stick out more, or is the part inside the arm just longer?

Sorry, I thought we were talking about wheel spacers. There is a spacer in the 306 axle assembly, to make up for the ABS sensor from memory (#5 -14.45 long). It's been a while, but I think the wheel still ends up being in the same place regardless. I made spacers similar to your drawing. I have a pair of Bridgecraft axles here if you're interested.

Screen Shot 2021-04-21 at 10.09.29 am.png

Edited by petert

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Arthur

Oké, thanks all. Rear camber is indeed probably not the first thing to spent money on. I was also thinking that 20mm wheel spacers would not be too bad. Especially since there is no fat basterds ever going to sit in the back anyhow. I don't think the best option (rebore) is ever worth the money for me. If there was a trailing arm that has camber, but same toe, that might be worth it. ZX has that but only without the extra trackwidth, correct?

 

I guess that the stub axle difference between 306 abs and 205 (gti)drums, might even be more then 12/13 mm.

 

I might indeed start at the front. Really wonder if my 1.6 driveshafts will cope. I see really counter info on here about that. I must laugh every time someone says more power will kill driveshafts. It's more complicated. Race clutches, slicks, lsd's and potholes with an 1,1 engine might be worse then 150 bhp on normal road tires. Even when it spins in 2nd, the torque on the driveshaft will be the same regardless. 

 

1,9 hubs are also very rare here, but again 307 hdi are very common in the scrapyards. But when I take that hub, the extra 10mm of a 309 trailing arm will not be enough to get to a nice camber setting because of the camber on 306/7 hubs. The extra lengths of an 306/7 driveshaft with 306/7, 82mm hub, might be spot on camber wise. That would then require even longer trailing arms. I'm also walking around with the idea to modify the subframe instead of taking longer trailing arms. Wonder why no one ever did that. Seems easier than making custom trailing arms. Why not just move the swivel point of the subframe out 20 or 25 mm? Perhaps even move them up a little so the arms would be above horizontal like standard geom. If you get then horizontal while doing 1 G, you're a winner, right? 

Edited by Arthur

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welshpug

zx has zero toe same width as 306.

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welshpug

307 hubs will not work, balljoint is in the hub and has a 2 bolt damper clamp.

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