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Loopian
Senior Member Joined: 03 Sep 2015 Location: Brighton Status: Offline Points: 202 |
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Posted: 18 May 2019 at 18:11 |
I’ve just finished the renovation of my 1973 Eldorado, registered it and got me new number plate. The engine is running sweet and everything looks good. But (and as their always has to be a but!) the front forks are just not right, they seem too soft, bottom out over bumps, look very low when any weight is put on them or when braking. I’ve re built them with new seals and Wirth progressive springs from Stein Dinse. I’ve overhauled my V7 special (1971) forks before and managed ok, although I used the existing springs. So my thinking is that I’ve got something fundamentally wrong in the rebuild but I cannot for life of me think what that would be, or maybe I have been sent the wrong springs?
Your thoughts would be much appreciated. Cheers Ian
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Ben.
Senior Member Joined: 18 Mar 2015 Location: Lanjaron Spain Status: Offline Points: 937 |
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Sounds like stronger rated springs, or some sort of spacer to encourage the ones you've got, would improve the situation. Does the fork travel match the operating range of the springs?
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Brian UK
Moderator Group Joined: 13 May 2014 Location: Surrey Status: Offline Points: 17641 |
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Did you compare the old and new progressive springs before fitting? Same length? It does sound like a spring problem.
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Brian.
Better 5 minutes late in this world than years early in the next. |
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Loopian
Senior Member Joined: 03 Sep 2015 Location: Brighton Status: Offline Points: 202 |
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I did compare the springs before fitting and they were the same size but I didn’t compare how much spring there was in the springs, plus I am feeling a bit daft as I’ve had clear out and seem to have thrown the old ones away, mind everything else bike related I don’t need I seem to have kept. I’ll do a bit more research on the springs I fitted when I strip them down as I do remember part no’s stamped on them.
The bike sits just the same as my V7 until I sit on it and then it sits about 40mm lower than when I sit on the V7. Thanks for your input. Ian
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iansoady
Senior Member Joined: 23 Jul 2017 Location: Redditch Status: Offline Points: 2402 |
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40mm extra sag is a lot. It does sound like the springs at fault, although progressive springs do often appear soft for the first part of their travel. I'd contact the suppliers.
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Ian
1952 Norton ES2 1986 Honda XBR500 1958-ish Greeves/Triumph in progress |
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Loopian
Senior Member Joined: 03 Sep 2015 Location: Brighton Status: Offline Points: 202 |
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Just a quick update, I’ve taken the fork legs off and found that these springs are for a Tonti framed bike, not a loop so the wrong springs were sent, and I installed them. I don’t think I could have compared them very well because according to the measurements I found, these springs are 10mm shorter then they should be. Hey ho, I’ll have to phone Stein Dinse and see what we can do.
Thanks all Ian
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Brian UK
Moderator Group Joined: 13 May 2014 Location: Surrey Status: Offline Points: 17641 |
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If the weight of the springs is about correct, then a spacer might well suffice. But it's sounding like the springs are softer.
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Brian.
Better 5 minutes late in this world than years early in the next. |
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Amboman
Senior Member Joined: 05 Dec 2015 Location: Maryland, USA Status: Offline Points: 383 |
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I'm not sure how they could be Tonti springs - those springs are smaller diameter (approx. 25 mm) and internal of the fork tubes vs. larger diameter and external of the tubes on a Loop.
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Charlie
'69 Ambassador,'71 Ambassador,'73 Eldorado,'75 Eldorado police,'76 Convert,'77 Morini 3 1/2 Strada,'81 Ducati 500SL Pantah http://www.AntietamClassicCycle.com |
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Loopian
Senior Member Joined: 03 Sep 2015 Location: Brighton Status: Offline Points: 202 |
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I’m certainly confused now, Greg’s site states that the free spring length is 240mm (ie holding it in your hand) I measured my Wirth springs and they are 230mm long with a reference number of 4060, Wirths reference 4060 states they are for a V7 Sport, 850t, 850t3, hence my assumption. Taking note of Amboman’s post, I then looked at the Chiltons workshop manual which states that the free length of the spring should be 230mm +/- 15mm. I’m going to try and speak to Wirth.
Cheers Ian
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Loopian
Senior Member Joined: 03 Sep 2015 Location: Brighton Status: Offline Points: 202 |
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I haven’t managed to speak to Wirth but it now appears that I do have the correct springs, and they are the correct length (230mm) I have confirmed this from information on the M G Cycle website. The correct length for cheaper springs are 247mm in length. So it’s not all about the length then! The trouble is I’m not any wiser about what to do next.
Cheers Ian
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Brian UK
Moderator Group Joined: 13 May 2014 Location: Surrey Status: Offline Points: 17641 |
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Are there any guides to checking the compression on the Wirth springs?
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Brian.
Better 5 minutes late in this world than years early in the next. |
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iansoady
Senior Member Joined: 23 Jul 2017 Location: Redditch Status: Offline Points: 2402 |
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I seem to remember that a rough guide is that the static sag should be 1/3 of the total travel - ie if the travel is 6 inches then it should sag 2" (again, as I remember this is unladen). Check by putting a cable tie on the stanchion with no load then see how far it's pushed up when the bike is on its wheels. But I don't know if this would apply to your situation.
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Ian
1952 Norton ES2 1986 Honda XBR500 1958-ish Greeves/Triumph in progress |
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c13pep
Senior Member Joined: 31 Aug 2017 Location: Doncaster Status: Offline Points: 2110 |
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`Tuning` the sag will also involve the rear suspension therefor it may be that the rear now needs retuning to accommodate the new front springs.
CHRIS |
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you can`t have any fun in a straight line
Monza Honda CB77 project |
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Loopian
Senior Member Joined: 03 Sep 2015 Location: Brighton Status: Offline Points: 202 |
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Right problem solved. However I must first award myself “plonker of the year”. Although I had thought that I had filled the forks with oil I had not. I did check that I had put in oil by cracking off the drain screw and oil came out, it has a distinctive red colour and I wrongly assumed that the oil was there. What I hadn’t thought about was that when I rebuilt the forks (it was last year sometime) I used fork oil as assembly oil and consequently that oil unsurprisingly pooled at the bottom of the forks and that’s what I released by undoing the drain screw. So I’ve put the bike back together and put in the oil and it now feels right. I haven’t been for a spin yet I’ll be doing that this afternoon, I just thought I’d better confess first!
Thanks very much for all your thoughts and apologies to Stein-Dinse. Ian
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jpc
Senior Member Joined: 06 Oct 2016 Location: Belgium Status: Offline Points: 651 |
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"Plonker of the year" ? Seven months to go ...
It's a bit early to congratulate yourself, plenty of opportunity left for us all
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