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Bumblebee

Help required before ordering new springs

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Hi All, 

Please help before my head implodes......

 

I managed to pick up a set of 4 koni dampers brand new for 325 quid on ebay. I was looking specifically for rears as the AVOs are shot anyhow, but the deal was too good, and reading reports on here lots of people seem pleased with Koni shocks.  So its for the GT6, 80-1388 front Koni 80-1389 rears. The car is a late mk3 with swing spring.

The rears are fitted with a starting point of half a turn adjustment wound in, although I did shorten the bump stops as the car is lowered with a 3/4 inch block on the back. 

 

The fronts however are making my head explode with spring rate calculations

It currenty has Protechs with an adjusting perch  and with the spring seated but uncompressed, so just enough on the perch to take up the slack the compression under load is  1.9 inches.

The springs themselves are 480lb 8 inches. so I work that out to be 912 lbs on the corner.  Heres where my brain fails to compute. The car could probably do with being 1/2 inch taller on the front give or take. The Konis Nick measured at 245mm perch to perch, and I agree having measured these ones here. Thats 9.64 inches. 
I calculate that by sticking on 475 lb springs an inch longer so 9 inches i will end up with1.92 inches  compressed under load ( so more the less the same) but as the spring is an inch longer it would sit an inch higher BUT less the .64 inch slack left between the perches with a nine inch spring ( the perches being spaced at 9.64 and the spring being 9) so in essence the front will come up .36 of an inch. plus the extra bit due to trigonometry I cant get my head round.so about half an inch.

Please please someone tell me Ive got this right or wrong cos I can take no more:blink:

My mind is officially boggled. I miss Alan, he would have PMd me with a detailed explanation in laymans terms without making me feel like an idiot. 
I read Nicks posts from when he went to Koni and was working spring rates out, but he was using springs that filled the perches, and its the extra slack in the perches thats confusing me somewhat.  I am trying to avoid spacers really although there is that option if required. I could also do with a ball park adjustment for them I thought I would throw a full turn in the front , so sort of half way and see how it felt. Taking them off and on to adjust is a bit of a pain

Many thks

PS the bolts in my back have all taken and I am now officially a bit cyborg. But without the awful back spasms

Andy.

 

 

Edited by Bumblebee

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I think you're right!  Or nearly.

The springs won't compress until the slack is gone, so 9" long and 475lbs/inch with 912lbs on it will compress by 1.92, springs now 7.08 long.

Compare with 8" long spring at 480lbs/inch with 912lb load, compresses by 1.9" to 6.1" long.     So new springs will stand 0.98" higher.   Less 0.64 gives 0.34".

The "extra bit" from the trig, I'd need the dimensions, but it's the ratio of the distance on the lower wishbone from the pivot to the spring base , and the distance from the pivot to the tyre centre.     Multiply 0.34" by that ratio.   About 3/4"?

John

 

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Thanks John. 

I will order a pair of new springs and see how we get on . 

A slight technical has occured when fitting the first rear shock. When I went to undo the lower nut it seemed loose. Oh well. Nothing new there then. HOWEVER the nut did not come off , it just spun. We all know where this is going. Much to and fro and I got it off to be presented with this. The AVO inner metal sleeve was still attached too but ive got that off. Now that does not look too healthy, and I submit to the people that the nut was cross threaded then hammered on! 

However its stopped me before I started and looks like a new upright will be required. Oh Koni bushes dont have a metal sleeve. Do I need one or do they just run on the bolts? I assume the latter. I am mildly peeved.

 

 

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What do the assembled gurus think?    Cut off the stripped end, drill the end of the stud, and tap for the same thread.      Insert a machine screw, using a permanent thread locker (Loctite 290?), cut off the head and make the end good?

Or, chuck it and get a new upright!

JOhn

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Either, though the reclamation would be tricky to do well even if all the kit is available. Shouldn’t be hard to find a link in better condition without great expense.

They didn’t have inner sleeves as standard, top or bottom, except on roto cars which had sleeves at the bottom. 
 

Glad to hear you are a fully recovered, pain-free cyber man Andy. Try to behave and not break yourself again........ (All three of my friends who have had back surgery, quite major in two cases and repeatedly in the other, suddenly become hung-ho again once fixed up and go back to doing stuff I’d think twice about even with a relatively undamaged back......)

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As regards the front springs, going to a higher rate than 350lbs and standard or lower ride height becomes problematic on standard length dampers without adjustable spring perches - as you are finding. The springs just get too short. I would say 9.5” is about the minimum with the Konis and they’ll be slightly slack at that (just fitted 10” on the GT6 and they were marginally clamped). Helper springs is about the only thing you can do. Though at 9” not sure you have room for them. Hopefully the springs will just about stay in and not upset the mot man......

.

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are you telling me riding my bike 50 miles for the first time in 4 years was wrong?  I did think going 10.5 inches but then to get it to sit right needs springs a lot softer. i think the links will be easy to find. spit bits is 2 miles away.

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58 minutes ago, Bumblebee said:

are you telling me riding my bike 50 miles for the first time in 4 years was wrong

Absolutely not..... but walking around with a 6 cylinder engine block would probably be unwise :tongue:  Unless your surgeon told you you shouldn't ride a bike of course  :smile:

 

59 minutes ago, Bumblebee said:

I did think going 10.5 inches but then to get it to sit right needs springs a lot softer

Well that's exactly it.  To combine a high spring rate and a low ride, the standard damper lengths don't work.  For a road car I really like 350 llb / 10.5" (Vit) or 330lb / 10" (GT6) but not ideal for a more competitive intent.

 

1 hour ago, Bumblebee said:

i think the links will be easy to find. spit bits is 2 miles away.

Yep.  Hopefully the trunnions may come apart without a battle too....... :ninja:

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I very much doubt the trunnions will come apart.  They ( whoever it was) did that fitting a nut. What do we think the trunnion will look like. I am fully expecting to end up with the whole lot off the car on a bench, heat , a big tickling stick, a lot of swearing an angle grinder, a hacksaw and 3 days. That of course assumes the other bolts will free allowing me to get it as far as a bench.

All to change a shock! Still we live in hope, it may just fall out.

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I always expect the worst...... I dont claim to be a mechanical god either, but some previous owners do the crappest things you then have to sort.

I am not even prepared to start on why the tub has a single spacer between it and the chassis at the back, but 2 on the front. I suspect a body off welding session and perhaps roof repair without having braced the tub first. I spotted it yesterday.  Probably explains why the rear weber is so close to the bulkhead, the exhaust touched the steering column  and the bonnet fit is a bit random. I dont know if its worth my while investigating. It will open another can of worms no doubt. I am currently trying to scrub it from my memory so I dont feel it needs further investigation.

There is something nice about rebuilding stuff yourself. When I re shelled the Stag I had to sort all the minor issues. Which means I know every bodge on the car, and have written them down in the file for the car so anyone down the line can work my "fixes" back. I never hammered a nut on though. Or "repaired" steering column bushes with the inside of a toilet roll (Stag when I stripped it) 

 

 

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Well, I'm very glad your surgeon works to higher standards that the PO's of your cars!

8 hours ago, Bumblebee said:

There is something nice about rebuilding stuff yourself.

Nice to know that you've improved 'em and done stuff properly even if not completely original.  I'm getting stick from one of my more originality-minded mates for not re-instating the front roof seam on the GT6.  Yes, it changes the look a little (not necessarily for the worse IMO) but also reduces wind noise and does away with a fearsome rot trap.....

Toilet roll steering bushes...... :pinch: FFS! Cut their hands off!

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So... on order are a pair of 450lb  9 inch springs. . I can chuck in spacers if absolutely necessary. I have had to allow for the fact that I already thought it was a touch low on the front, and if you allow for the fact it has 2 spacers in it at the front body to chassis, in reality with the body 10mm or so lower at front it would be too too low as it will be tricking the eye to the chassis height when in reality the body is higher at the front anyhow.

Anyhow the die is cast so time will tell now. I've also got a used pair of rear verticals coming, so if the other side is knacked it wont matter.. 27 quid the pair.  And  trunnion kits for the inevitable monged trunnion bushes when the persuader gets near them. What I should have done is ordered a pair of tops for the front springs so I could have left the protechs built and built this set off the car. But inevitably I forgot. 

Hopefully I will get going on it the weekend although I am helping my 14 year old build his first ever engine on Saturday. A Lotus Twin cam, a Twink is not a bad place to start. The team leader is my Neighbour who spent years working on Bristols for Frazer Nash. Don't even ask what the parts and machining costs for that were! OBSCENE!  Still he is, with my neighbour's assistance, building a 1969 Elan +2 for his mum for Xmas. I don't know if she wants it, but her youngest will have built it, and its worth a few bob finished. I'm sure she will love it, and if she doesn't then she can gift it to the lad who put it together. He will be taught by the neighbour, properly, with plastigauge and gapping rings and the works. They did the gearbox last week. Here he is battling needle rollers.  I just thread drifted my own thread.

 

 

 

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What a great education and experience for the young lad - well done him, you and your neighbour.

I had all sorts of problems getting the TR front height right when fitting later TR front suspension to enable discs and the improved castor/camber set up. I'm currently having issues with the Stag too - having fitted new standard springs front and back the front sits far too high. I'm about to try 1" lowered fronts. The car is absolutely standard and the springs being replaced were the 1974 originals, but as ever, nothing is straightforward.

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Well Nick, the cynic is us both has been more than proved right. The bolt is well and truly seized. 

More worrying, annoying, and all round bigger pain in the butt is now the upright is free bar the big bolt I need to cut out there is significant and large amount of movement between the bearing carrier the trunnion bolt passes through and the shaft itself. The movement is clearly visible and clunky and can clearly be seen where the carrier meets the flinger. I didnt notice it before, possibly as everything was seized tightish stroke stuffed full of solidified grease. So changing a shock has revealed it, but it is what it is. Better to find it now than a catastrophic failure, I guess the needle roller has either broken up, or more likely eaten the shaft. Of course I wont know till I get it out and I cant get it off until Ive got a hub puller. Then it will be a case of deciding how to proceed, either a second hand unit of unknown quality, or seeing what is ok and buying the rest and hoping they arent of chinese plasti-metal. 

Im feeling a bit glum now:ermm: I suppose a hub puller will be the next purchase. I may be a touch out of my depth here, but hey ho, Im sure I can blag it somehow

Edited by Bumblebee

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Such a finely engineered thing the swing-axle rear end.........

 

.............NOT!

Yes, sounds like the bearings are shot and high probability that the shaft is too. Apart from getting the hub flange off (only the right puller stands a chance and even then it can be a struggle), there is nothing difficult about the design apart from how anyone thought it suitable for a road-going vehicle.

Next challenge (as you note!) will be finding a decent shaft (should be a long one), and if choosing to buy new, determining whether the UJ trunnion is properly attached.....

Dunno whether any of our previous sufferers in that saga ever got any useful feedback from their respective suppliers?

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Thanks Nick, the last comment pointed me in the direction of search, and Roger has advised me Fitchetts ones seem to hang together. Next up is to get a puller, and then see if I can get the hub split and see what gives in there. And then the age old saga of trying to find bearings not made of toothpaste.

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Bearings shouldn’t be a problem. The ball race at least will have a bearing number on it, which you can google. This should bring you up a multitude of suppliers and wide choice of makes.  Originals were probably RHP or Timken  but any reputable make should be fine.

The roller bearing might be a bit harder to identify. Not sure whether it will have ID markings. May have to measure shaft & housing dimensions and use those. Might be worth seeing whether there is room for one with longer rollers......

Possibly Fitchetts can supply decent bearings anyway, but I’ve not been impressed with the offerings from the other suspects in the past.

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16 hours ago, Bumblebee said:

Thanks Nick, the last comment pointed me in the direction of search, and Roger has advised me Fitchetts ones seem to hang together. Next up is to get a puller, and then see if I can get the hub split and see what gives in there. And then the age old saga of trying to find bearings not made of toothpaste.

Hello 

          If you are not in a rush i can tell you the Torrinton needle roller number when home thursday(and diamentions if you want as i have a old torrington catalouge

Roger

Ps i have a puller as well in the midlands stourbridge area

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Damn! 

I had already ordered a puller. Thats a bummer! Thanks anyway Roger. I will get it apart and all will become clear. 

Had fun building short engine with Lewis this weekend for the Elan. Forgive me throwing up a load of photos, but I am quite proud of him. I put the circlips in the pistons ( theres a chance of screwdriver stabbing!) Other than that he did the lot, and we now have a short engine less the sump pan. We need to order a couple of bits before we can close the sump out so its all wrapped in clingfilm now. Photos are not in order but you get the drift. Seemed a shame to put those pistons in an engine, they are lovely:biggrin:

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Edited by Bumblebee

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Start them young...…  I approve :smile: Don't they look funny with all those main bearings :huh:

You do know that the pistons shouldn't all be at the top at the same time though...….? :P

BTW, if you own a swing axle a car it's good to have your own puller.  I solved the problem a different way and got rid of the swings axles!

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