Another tele fork question (sorry)

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bevanclark
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Another tele fork question (sorry)

Post by bevanclark »

Hi folks, while I have the forks off my 1950 VB to replace the seals, I thought I'd investigate another puzzle:

When I got the bike, 2 1/2 years ago, I was surprised at the softness of the forks. Also, they seemed to sit a bit low. This was confirmed when I was able to compare my bike to others on a recent N.Z. Ariel rally - you can see about 1" less of the seal carrier than other similar singles. i also get a definite clonk if I hit a decent bump or pothole (of which there are many around here). The steering head is not loose and i had the specified amount of oil in the forks (although it was SAE 30, which may not be appropriate ?).

The obvious reason is weakened springs, but after some basic measurements and tests I'm not so sure.

They look in good condition, have an orangish paint blob on the top, 20 1/2 turns and a free length of slightly over 10 inches and 0.21" wire thickness. Looking at Waller and the Draganfly site it seems that they are probably their part number H55-54 (Single and KH 11-20 stone rider), so their free length is perhaps a 1/4" shorter than quoted. I did a (rather crude) compression test with a 5L pack of oil and it seemed to be close to Drags quoted spring rate, so I'm a bit puzzled as to why they sit so much lower than other bikes.

Given that new springs are pretty costly by the time I get them over here, I was wondering about fitting a 1" pre-load spacer on top of the springs, but not sure if that would be a sensible or safe idea. Or do I just evict the moths from my wallet and buy replacement springs ?

As always, any guidance is welcomed.
Cheers, Bevan
Simon.Gardiner
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Re: Another tele fork question (sorry)

Post by Simon.Gardiner »

Bevan

My forks have always 'sat low'-ish on the oil-seal holders, and I've always used SAE30 - I'm fine with both. I did once buy an old VH field bike that the kids had 'improved' by putting 40 (or maybe 50) in the forks, which were essentially locked solid (maybe one reason why the bike came my way cheaply). I wouldn't advise using anything thicker than SAE 30!

Which top bush have you used, the later long one (which might well make you 'clonk' earlier) or the correct (for '50) short one?

It's not that difficult to get at the fork springs on these bikes, if you think it would be an improvement for you I'd say by all means try some spacers, easy enough to change again. I've got extra-long spacers in my BM forks (so a lot of pre-load, although with dual rate springs). It rides fine, just goes over quite a long way on the side stand!

SG
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'55 Huntmaster, '56 VH, ' 51 VH, '62 Arrow, '80 R100RT, '00 Sprint ST (now with a new Arrow project, and just now those 4-stroke Ariel parts can't even make one running bike...)
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Re: Another tele fork question (sorry)

Post by nevhunter »

A Spacer would be OK if there's no chance of it coil binding. Check what distance you need and add the spacer size to the compressed spring size. A progressively wound spring would increase the spring rate. I regularly bottom out my VCH and dent the front mudguard. That's the only Tele fork ARIEL I've regularly ridden. I use the thickest oil that's generally available SAE 60.The damping is by the tapered bit at the bottom of the fork filling the hollow end of the stancheon progressively. It's completely standard apart from the oil drain holes. Probably works as good as any BSA/ Ariel does. Nothing really special. Nev
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Re: Another tele fork question (sorry)

Post by Paul Gasson »

Hi Bevan, I have owned a 1955 NH for many years and spent ages trying to improve the forks with different springs and oil grades, nothing made enough of a positive difference throughout a range of fork impacts I am likely to encounter so stuck with 30W oil and normal springs, there is virtually no damping with the standard set up.

I am currently working on a 1950 model and have the same softness of fork action you mention. The only difference I noticed compared with the 1955 forks was the top bush length, other than oil drillings in the stanchions. The later type bushes are about 1 inch longer. I made a trial assembly and with later bushes, there was slight compression in the spring when fitted. The earlier short top bushes had an amount of free movement at the top of the fork travel but it was unused as the spring was not long enough, although to specification. The longer bush does not seem to reduce the amount of travel so I am changing to the longer bushes during my rebuild. Incidentally, I noticed about 1 inch extra seal holder with long bushes fitted as well. I think you could add a spacer under the spring and achieve a similar result but as Nev said, make sure the spring is no coil bound before you reach the bottom of the forks stroke.
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Re: Another tele fork question (sorry)

Post by nevhunter »

The oil I use is actually Tractor Transmission UNIVERSAL which is OK for all hydraulics and doesn't foam. I've used that kind of oil forever (almost) in every bike I service. It's fine for the primary chain also. Nev
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