205 Rear Beam - Interchangable?
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  1. #1
    Member OLi205GTi's Avatar
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    Default 205 Rear Beam - Interchangable?

    Hi all, wondering if S1 and S3 rear beams are interchangeable?

    Can a S1 drum brake rear end be rebuilt utilising S3 rear beam tube and parts?

    Cheers,

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  2. #2
    1000+ Posts PeterT's Avatar
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    Yes, all the same. The only difference being the brakes and stub axles

    '92 205 Mi16
    '90 Mi16x4

  3. #3
    Member OLi205GTi's Avatar
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    Thanks Peter

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    Just a thought Peter....whilst on beams. What effect would an Si beam have on a GTi? Handling issues etc ?
    jr20516v

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    Exige SC [modded], 205 Si. 205 GTi , Megane R26 LY , Megane 225 [modded ]


    Previous: Honda EP3 Supercharged , 205 x34 [ including MI16 TURBO, 8v TURBO, CTI, 16V+TB's, 8V+TB's,] Fiat X1-9 X3, Beta coupes x5, Lancia Gamma coupe, GTI-R, Corvette C4, Fiero x5, Alpine GTA turbo, r5 GTT Dimma, 2cv ripple nose, Lotus Elise, 205 Dimma TT, Cliosport 172.x2, Clio rs 200

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    1000+ Posts Richard W's Avatar
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    Just an Si beam, or Si beam, torsion bar and ARB?

  6. #6
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    The full monty....not just the beam.
    jr20516v

    Now:
    Exige SC [modded], 205 Si. 205 GTi , Megane R26 LY , Megane 225 [modded ]


    Previous: Honda EP3 Supercharged , 205 x34 [ including MI16 TURBO, 8v TURBO, CTI, 16V+TB's, 8V+TB's,] Fiat X1-9 X3, Beta coupes x5, Lancia Gamma coupe, GTI-R, Corvette C4, Fiero x5, Alpine GTA turbo, r5 GTT Dimma, 2cv ripple nose, Lotus Elise, 205 Dimma TT, Cliosport 172.x2, Clio rs 200

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    depends on the arb size and torsion bars, if heavier then an improvement on the S1, if lighter then a degradation. Can show you a S1 Gti arb if you like?
    87 S1 205 GTI / GTI6 powered a project underway
    306 convertible (gti6 candidate)
    307 HDi wagon
    407 HDi wagon

  8. #8
    1000+ Posts PeterT's Avatar
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    Quote Originally Posted by jr20516v View Post
    The full monty....not just the beam.
    Why would you soften up the rear of a GTi? It will only lead to understeer. The only way to improve the handling of a GTi is to stiffen the rear.

    '92 205 Mi16
    '90 Mi16x4

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    Quote Originally Posted by Matthew View Post
    depends on the arb size and torsion bars, if heavier then an improvement on the S1, if lighter then a degradation. Can show you a S1 Gti arb if you like?
    Thx Matt......yes i have arb's here from a S1... i know they are thicker etc but i was simply asking what major effect would it have... i know softer but crazily so....10% so 50% so ?
    jr20516v

    Now:
    Exige SC [modded], 205 Si. 205 GTi , Megane R26 LY , Megane 225 [modded ]


    Previous: Honda EP3 Supercharged , 205 x34 [ including MI16 TURBO, 8v TURBO, CTI, 16V+TB's, 8V+TB's,] Fiat X1-9 X3, Beta coupes x5, Lancia Gamma coupe, GTI-R, Corvette C4, Fiero x5, Alpine GTA turbo, r5 GTT Dimma, 2cv ripple nose, Lotus Elise, 205 Dimma TT, Cliosport 172.x2, Clio rs 200

  10. #10
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    Quote Originally Posted by PeterT View Post
    Why would you soften up the rear of a GTi? It will only lead to understeer. The only way to improve the handling of a GTi is to stiffen the rear.
    Yes i know Peter however the reason i asked was simply because of this........ i have just purchased a 205 GTI with a suspect rear beam....and i have two great condition Si rear beams...before they go to the tip....can you see why i asked ?
    jr20516v

    Now:
    Exige SC [modded], 205 Si. 205 GTi , Megane R26 LY , Megane 225 [modded ]


    Previous: Honda EP3 Supercharged , 205 x34 [ including MI16 TURBO, 8v TURBO, CTI, 16V+TB's, 8V+TB's,] Fiat X1-9 X3, Beta coupes x5, Lancia Gamma coupe, GTI-R, Corvette C4, Fiero x5, Alpine GTA turbo, r5 GTT Dimma, 2cv ripple nose, Lotus Elise, 205 Dimma TT, Cliosport 172.x2, Clio rs 200

  11. #11
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    S1 arb should fit Si beam, as do many other arb's if you make them to size. I would be surpised if the torsion bar ends are different so that they could be swapped as well if same length. Only issue are ther Si specifics which should make no difference to the outcome. Stifness goes up at the third power of bar thickness, so 18.9 cubed versus Si bar cubed. Gives you the answer. Get a vernier and measure.
    87 S1 205 GTI / GTI6 powered a project underway
    306 convertible (gti6 candidate)
    307 HDi wagon
    407 HDi wagon

  12. #12
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    So i am back to my original question LOL...... how bad would the handling be with an Si beam......?? From memory Si's handled very well [some people such as Graham W actually prefer them ]....how bad is "soft"?
    jr20516v

    Now:
    Exige SC [modded], 205 Si. 205 GTi , Megane R26 LY , Megane 225 [modded ]


    Previous: Honda EP3 Supercharged , 205 x34 [ including MI16 TURBO, 8v TURBO, CTI, 16V+TB's, 8V+TB's,] Fiat X1-9 X3, Beta coupes x5, Lancia Gamma coupe, GTI-R, Corvette C4, Fiero x5, Alpine GTA turbo, r5 GTT Dimma, 2cv ripple nose, Lotus Elise, 205 Dimma TT, Cliosport 172.x2, Clio rs 200

  13. #13
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    The torsion bars are nearly the same, just change the ARB, you wouldn't notice the difference.
    Sis are better for everyday use and rough roads but a GTi front and Si rear wouldn't be good.

  14. #14
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    argggh the Si guru awakes !!! So if i throw an ARB from a GTi [straight fit ? ] into the Si rear beam and install i should basically get the same handling as a normal Gti ?
    I think this will be a common question in the future....as there are more Si beams around than Gti's
    jr20516v

    Now:
    Exige SC [modded], 205 Si. 205 GTi , Megane R26 LY , Megane 225 [modded ]


    Previous: Honda EP3 Supercharged , 205 x34 [ including MI16 TURBO, 8v TURBO, CTI, 16V+TB's, 8V+TB's,] Fiat X1-9 X3, Beta coupes x5, Lancia Gamma coupe, GTI-R, Corvette C4, Fiero x5, Alpine GTA turbo, r5 GTT Dimma, 2cv ripple nose, Lotus Elise, 205 Dimma TT, Cliosport 172.x2, Clio rs 200

  15. #15
    1000+ Posts PeterT's Avatar
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    Whilst Graham says they're nearly the same diameter, that's not the full story. Resistance to twisting or torsion is measured by this formula:

    J=(pi x D^4)/32

    thus a small change in diameter equals a large change in torsional resistance.

    I'm not sure why you'd fit an unknown beam to a car anyway. Any 205 beam should be treated as suspect these days. Ditto for early 306.

    '92 205 Mi16
    '90 Mi16x4

  16. #16
    Fellow Frogger! racing405's Avatar
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    Once I got the beam out of my 306 and cleaned it for inspection, where I though it fell apart due to dud bearings, in fact it was almost perfect! Looking at threads from the UK, we are very fortunate that we don't have to cope with salted roads. At 250,000k and 20 years old, my 306 beam would be considered perfect in the UK!!!

    I should know the relative lengths of 205 and 306 bars - but I have no idea. I do have a set of 306 torsion bars and arb that could go to a good home, they'll never be used in this little green 306 again.
    racing 405
    1:59:09 last time at Phillip Island - less than standard Mi16.

  17. #17
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    Quote Originally Posted by PeterT View Post
    Whilst Graham says they're nearly the same diameter, that's not the full story. Resistance to twisting or torsion is measured by this formula:

    J=(pi x D^4)/32

    thus a small change in diameter equals a large change in torsional resistance.

    I'm not sure why you'd fit an unknown beam to a car anyway. Any 205 beam should be treated as suspect these days. Ditto for early 306.
    I have 3 very good rear beams from Si's and one shot Gti one on a car.... just doing my homework before i make a leap :}
    jr20516v

    Now:
    Exige SC [modded], 205 Si. 205 GTi , Megane R26 LY , Megane 225 [modded ]


    Previous: Honda EP3 Supercharged , 205 x34 [ including MI16 TURBO, 8v TURBO, CTI, 16V+TB's, 8V+TB's,] Fiat X1-9 X3, Beta coupes x5, Lancia Gamma coupe, GTI-R, Corvette C4, Fiero x5, Alpine GTA turbo, r5 GTT Dimma, 2cv ripple nose, Lotus Elise, 205 Dimma TT, Cliosport 172.x2, Clio rs 200

  18. #18
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    Nearly all beams are shot including Si, just do one up.

  19. #19
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    errr...the Si beams are done up :}
    jr20516v

    Now:
    Exige SC [modded], 205 Si. 205 GTi , Megane R26 LY , Megane 225 [modded ]


    Previous: Honda EP3 Supercharged , 205 x34 [ including MI16 TURBO, 8v TURBO, CTI, 16V+TB's, 8V+TB's,] Fiat X1-9 X3, Beta coupes x5, Lancia Gamma coupe, GTI-R, Corvette C4, Fiero x5, Alpine GTA turbo, r5 GTT Dimma, 2cv ripple nose, Lotus Elise, 205 Dimma TT, Cliosport 172.x2, Clio rs 200

  20. #20
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    But i do need a Gti ARB to finish the job.
    Matt....do you have that supplier off hand that we spoke about on the phone today ?
    jr20516v

    Now:
    Exige SC [modded], 205 Si. 205 GTi , Megane R26 LY , Megane 225 [modded ]


    Previous: Honda EP3 Supercharged , 205 x34 [ including MI16 TURBO, 8v TURBO, CTI, 16V+TB's, 8V+TB's,] Fiat X1-9 X3, Beta coupes x5, Lancia Gamma coupe, GTI-R, Corvette C4, Fiero x5, Alpine GTA turbo, r5 GTT Dimma, 2cv ripple nose, Lotus Elise, 205 Dimma TT, Cliosport 172.x2, Clio rs 200

  21. #21
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    What shocks are you going to use?

  22. #22
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    Bilstein B4's [gti6 items ]
    jr20516v

    Now:
    Exige SC [modded], 205 Si. 205 GTi , Megane R26 LY , Megane 225 [modded ]


    Previous: Honda EP3 Supercharged , 205 x34 [ including MI16 TURBO, 8v TURBO, CTI, 16V+TB's, 8V+TB's,] Fiat X1-9 X3, Beta coupes x5, Lancia Gamma coupe, GTI-R, Corvette C4, Fiero x5, Alpine GTA turbo, r5 GTT Dimma, 2cv ripple nose, Lotus Elise, 205 Dimma TT, Cliosport 172.x2, Clio rs 200

  23. #23
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    They will have a bigger adverse effect than the torsion bars in my experience. The ones I had did nothing.

  24. #24
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    The earlier B4's [they were fatter ] were not the best.....and started to get a name for themselves with the UK boys. I only buy the new versions and they work a treat IMHO.....as close as stock as one can get.....without the OE price !!
    jr20516v

    Now:
    Exige SC [modded], 205 Si. 205 GTi , Megane R26 LY , Megane 225 [modded ]


    Previous: Honda EP3 Supercharged , 205 x34 [ including MI16 TURBO, 8v TURBO, CTI, 16V+TB's, 8V+TB's,] Fiat X1-9 X3, Beta coupes x5, Lancia Gamma coupe, GTI-R, Corvette C4, Fiero x5, Alpine GTA turbo, r5 GTT Dimma, 2cv ripple nose, Lotus Elise, 205 Dimma TT, Cliosport 172.x2, Clio rs 200

  25. #25
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    The 205 ones I had just floated, they were the slim ones but probably pretty old. Fronts from that set were leaking.
    The fronts in my 405 have never worked well but at least are still intact after a huge amount of rally surveying along at times goat tracks. LIPs wouldn't have survived more than 6 months of that treatment.

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