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Old 21st September 2020, 14:59   #1
YMGF
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Default Rear shock absorber length

This is possibly a dim question but does anyone know whether the rear shock absorbers extend beyond what feels like a mechanical stop which limits their length when off the car?
My 2.5 saloon has just been going through a rear end re-build, (It must have had a hard life), and most components are new. Subframe, upper and lower arms, ARB and springs. Everything has been nipped up but not fully tightened pending putting the car on the wheels. From what I can see, all seems correctly aligned.
I came to putting the new shocks on today which I bought assembled. They have the same code as the previous, and off the car they are the same length.
However when the tops are secured the bottom fixing is approx 100mm away from the trailing arm fixing point. Jacking under the arm until the car is about to lift brings the shock mounting to with about 25mm of the trailing arm point.
It seems impossible to extend the shock any further.
I would have expected the shocks to extend as far as the suspension could travel so the top mounting doesn't act as a suspension stop? Or am I missing something? (It has been a long day!)
Would appreciate any thoughts you might have.
Thanks
Michael
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Old 21st September 2020, 16:36   #2
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I just happen to have my 1.8 saloon jacked up with the rear wheel/hub/disc removed. The whole rear suspension is hanging on the shocker. So, just for you, I went out and measured the extended length.. I pushed the tape end as far up into the mounting turret as possible and measured down to the centre of the lower mounting bolt. It's 810mm, give or take a mm.

I'm not aware of any 'stop' in the extension of the unit.

TC


(EDIT dated 22 Sept 20: The above measurement is 610mm not 810mm. Sorry for any confusion)

Last edited by T-Cut; 22nd September 2020 at 14:08.. Reason: Typo
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Old 21st September 2020, 17:29   #3
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Thanks TC, that dim certainly makes sense.
I've just been out and measured both old and new shocks from the underside of the top mount stud to centre of dog bolt and both are 610mm. (Both are off the car of course). Clearly that suggests mine have at least another 200mm of extension in them. Now I'm no Geoff Capes, but I could not get neither old nor new shocks to extend at all beyond their current 610mm. Also can't get dog bolt into trailing arm.
If I compress old or new and leave to extend there is a metallic sound where they stop, (610mm). The arm won't jack any higher as the car will lift off the stands.
I have to say I'm at a loss to know how to get them extended. I must be missing something.
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Old 21st September 2020, 19:47   #4
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What make and model no. are your shocks ? Perhaps the manufacturer's website has a spec which gives extended length ?
Have you tried pumping them a few times ?
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Who said it was simples ?

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Old 21st September 2020, 20:53   #5
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reminds me of when i did my rear shocks renewal couple of years back. i had the same problem. i ordered my shocks on line from a company advertising genuine mgrover spares. cannot recall the name. they were supposed to be saiac (probably spelt wrongly) original and were to fit the rover 75 ... but they were too short !! i got a refund and bought some sachs from ecp . the length was longer on the ecp ones as i even took my measuring tape with me and fully extended them befor i paid my money. the reason being the ones that i purchased from ebay were for the contempory rover 75 and these i believe had the same setup as the mgzt..... shorter. it must also follow that the springs may be of different lengths and the setups have been mixed probably. i also had to jack up the arms to fit them and thay were on the stops fully extended position from word go. i did go around the block once with them fitted and almost took off and landed at the rear over the slow down humps !! took them straight off and refitted my oldies back on. get the spring colours right and then the shocks !! or you may be ok with just a shocker length change.
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Old 21st September 2020, 23:09   #6
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Those are the wrong shocks for your car.--
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Old 22nd September 2020, 08:01   #7
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Thanks all for your replies.
I believe the shocks are correct for the car as they are Delphi type G and identical to the originals.
The only things that are different are the springs. My label under seat had lost it's text so following a discussion here I decided to buy white code diesel springs on the basis that there would be little difference at the rear between by 2.5 and a diesel. In any case, as type G shocks apply across all saloon models they would be the same on a diesel.
I couldn't find length spec for the Delphi shocks, but TRW list their lengths as 604 and 379mm, so a stroke of 225mm. This is nothing like my original or new ones, both of which have a stroke of approx 110mm. Maybe coincidence, but measuring mine from under the top plate to centre eye does give 604mm. Does anyone know how shocks should be measured? Is it from top of piston rod to centre of eye?
I certainly can't get either the originals or new to extend further and I can't believe it should be necessary to jack up the suspension so far to even get close to aligning shock to the arm. I'm clearly missing something fundamental
TC, would you mind confirming the make/spec of your shocks please.
Thanks,
Michael.

Last edited by YMGF; 22nd September 2020 at 09:50.. Reason: Update.
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Old 22nd September 2020, 09:44   #8
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Quote:
Originally Posted by YMGF View Post
TC, would you mind confirming the make/spec of your shocks please.
They're the original factory fit (2004), so will be as listed in the Rimmer data for the Rover 75 Saloon https://rimmerbros.com/Item--i-RPD102250

Code G
Part No: RPD102250
Make: ??

TC

Last edited by T-Cut; 22nd September 2020 at 09:46..
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Old 22nd September 2020, 09:58   #9
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Updated.
I've now got the shock connected by jacking under the shock boss almost to the point when the car is lifting from the stands. (Admittedly it is light, with no fuel nor interior). The distance from the underside of the top mount studs to the centre of the eye is 613mm.
So as the suspension is compressed, now the spring loads are being taken by the shocker and transferred to the body via the two 8mm studs in the shocker top mount. I'm not an expert on this suspension but can that be right? There is nothing to spread the load in that area other than the two M8 nuts.
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Old 22nd September 2020, 10:01   #10
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Thanks TC. They are what I have too.
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