Compression Strut Conversion

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Rich K
Wedge Pilot
Posts: 260
Joined: 08 Aug 2015 18:04
Location: Worcester, United Kingdom

Re: Compression Strut Conversion

Postby Rich K » 14 Oct 2021 21:20

Fascinating, quality insight from Hasbeen as always.
1980 TR7 drophead now repainted and started refitting plus V8 upgrade
1977 TR7 fixedhead awaiting restoration
1981 TR7 drophead bodywork now done, mechanicals next then final paint
Ford Ranger Wildtrak
Jaguar XKR Supercharged

Wedge Pilot
Posts: 268
Joined: 09 Sep 2005 05:15
Location: Australia

Re: Compression Strut Conversion

Postby Sondar » 18 Oct 2021 07:50

Thanks Hasbeen; as Beans said, an interesting read - I always enjoy reading your posts!

I've had one or two issues with spring rates myself. The guys that did the coil-overs for me also fitted a 1 inch roll bar, which is fine, happy with that. However, we had a "discussion" about spring rates, with me telling them it is a road car, so it should be sprung accordingly. He wanted to fit 300lb front springs, which I thought would be way too hard, so I managed to get him to come down to 250's (he was adamant that it needed higher rate). When I got it back, it was shall we say, firm. OK, I thought, maybe that's just what 250lb springs feel like. However, to keep the front tyres in contact with the road on any kind of bumpy surface (it spent quite a lot of time in the air!), I had to back the adjustable shocks off to minimum. Eventually, I got sick of it and when one of the shocks packed up after a few months, I took the opportunity to return the springs to them in return for softer ones. He then told me that the one's they originally fitted were in fact 350lb. No wonder it was bloody hard - there was no give in them at all.

The softer ones are in fact the 250's that he originally promised to fit. Still too hard in my opinion, and I was planning to drop back to 200lb, which is what the previous springs were before the coil-over conversion. So I guess that's my answer on the anti-roll bar - I need to keep it to avoid the higher spring rates needed without it.

I think as a first step, I'm going to drop the spring rates and fit offset roll bar mounts and see what that does. The alloy hubs that Hamilton's sell also look like a good option for reducing unsprung weight and getting the bigger outer bearings. I can try the compression struts later - there's always time.

Thanks again for the input.

1980 TR7V8 in Poseidon Green - 4.6 Rover V8, limited slip diff, front coil-overs, AP Racing 4-pot front brakes, leather interior. Last of 8 owners, mine since 1999 and no-one else is getting it...

Posts: 7708
Joined: 15 Mar 2006 19:29
Location: Netherlands

Re: Compression Strut Conversion

Postby Beans » 18 Oct 2021 21:36

The front springs on 't Kreng ( my blue Sprint powered FHC) are 60kg/cm (336lbs/in), giving an effective spring rate of 65,4kg/cm (366lbs/in).

The rear springs are 30kg/cm (168lbs/in). But as these are be placed slightly behind the axle (coil overs on the shock mounts) and as such further away from the lower links body mounting point, the effective spring rate is 33.9 kg/cm (190lbs/in). Which is almost 45% higher compared to the original rear spring set up. So they compare to 43kg/cm (241lbs/in) springs in the original location.

I quite like it with custom adjustable dampers. But you really have to trash the car on country lanes to get the best out of it!
At speed the car really is very well balanced and sure footed. Even on bad road surfaces
1976 TR7 FHC (currently being restored ...)
1980 TR7 DHC (my first car, a.k.a. Kermette)
1981 TR7 FHC (Sprint engined a.k.a. 't Kreng)

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