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Discussion Starter · #1 ·
My T120V is almost finished . My final task is to set up the suspension so I have a quick question for the forum re progressive front fork springs. They seem to be available in 19" (stock) and 19.5" lengths .I am presuming that the 19.5 " springs exist because to fit them you effectively are increasing the pre-load. This will stiffen the front up and reduce the SAG Can anyone chip in here( ideally with their weight )and any experiences good or bad re the differing spring lengths and setting up the front I can make a decision as to which spring length to buy to achieve my target setting
 

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Hi
According to the Spec in the 1972 Triumph workshop manuals.
free length for Triumph 650 twin = 19.1"
free length for Triumph 750 triple =19.7"

regards
Peg.
 

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The progressive springs do improve the front suspension. During a few trials, i found a 7.5 fork oil to work best on British back roads and fast main roads. Any oil thicker than this will make it a bit crashy. About 30 psi tyre pressure seems to suit it so try both these ideas out. 190cc of oil per leg
 

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ive always put 20W50 in the forks of my 72 T120, because i have it handy.

today i put 5W20 into a BSA because i had some handier.

does a half inch of pre-load really make a difference? i live three miles from a paved road, so everywhere i go i start out dodging pebbles, cobbles, and sometimes boulders. i dont think i would even notice a half-inch difference in ride height, if that's what it would work out to be.
 

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Hi,
progressive front fork springs. They seem to be available in 19" (stock) and 19.5" lengths .
Assuming you're talking about springs from Progressive Suspension (as opposed to springs from those well-known suspension specialists Ebay :cool:), these are what PS recommend for a '72 T120. I found them by:-

. entering "progressive suspension" into Google;

. selecting "progressive suspension fork springs" from the returned list and then "Fork Spring Kit - Progressive Suspension" from the returned links;

. on Fork Spring Kit | Progressive Suspension, clicking on "Select Your Bike" then "1972", "TRIUMPH" and "T120 (air-cooled)" from the displayed tables;

. on https://www.progressivesuspension.com/products/3064/1972/triumph/t120-air-cooled , clicking on "Fork Spring Kit".

I am presuming
Don't use anything intended for a triple (unless you're ... errr ... very heavy ...), their springs are (should be) stiffer; fwiw, I have twin springs in/on all my triples and I couldn't be described as "light" by any stretch of the imagination. :cool:

In addition, if you haven't done so already, I advise Damper valve seal conversion 1971 on (pair) (y) instead of the standard 97-4003 Damper head O-rings, (n) the latter are known to cause stiction that affects the suspension's response to small bumps. :(

Hth.

Regards,
 

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Discussion Starter · #7 ·
The progressive springs do improve the front suspension. During a few trials, i found a 7.5 fork oil to work best on British back roads and fast main roads. Any oil thicker than this will make it a bit crashy. About 30 psi tyre pressure seems to suit it so try both these ideas out. 190cc of oil per leg
Cheers Rambo , I have will try your suggestions . My question was based upon the fact that many of the classic bike suppliers seem to offer the 19.5" length progressive spring as standard and having come from a sports bike background where everything is adjustable I was thinking (probably over thinking) that because there isn't a adjustment for front preload on the forks that the longer springs were to solve a problem I didn't know about.
 

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Discussion Starter · #8 ·
ive always put 20W50 in the forks of my 72 T120, because i have it handy.

today i put 5W20 into a BSA because i had some handier.

does a half inch of pre-load really make a difference? i live three miles from a paved road, so everywhere i go i start out dodging pebbles, cobbles, and sometimes boulders. i dont think i would even notice a half-inch difference in ride height, if that's it would work out to be.
Thanks Speed rattle as I have said to Rambo I have come from a sports bike background where 1/2" more preload makes a massive difference. I think I am probably over thinking it . Thanks for taking the time to respond though
 

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Discussion Starter · #9 ·
Hi,

Assuming you're talking about springs from Progressive Suspension (as opposed to springs from those well-known suspension specialists Ebay :cool:), these are what PS recommend for a '72 T120. I found them by:-

. entering "progressive suspension" into Google;

. selecting "progressive suspension fork springs" from the returned list and then "Fork Spring Kit - Progressive Suspension" from the returned links;

. on Fork Spring Kit | Progressive Suspension, clicking on "Select Your Bike" then "1972", "TRIUMPH" and "T120 (air-cooled)" from the displayed tables;

. on https://www.progressivesuspension.com/products/3064/1972/triumph/t120-air-cooled , clicking on "Fork Spring Kit".


Don't use anything intended for a triple (unless you're ... errr ... very heavy ...), their springs are (should be) stiffer; fwiw, I have twin springs in/on all my triples and I couldn't be described as "light" by any stretch of the imagination. :cool:

In addition, if you haven't done so already, I advise Damper valve seal conversion 1971 on (pair) (y) instead of the standard 97-4003 Damper head O-rings, (n) the latter are known to cause stiction that affects the suspension's response to small bumps. :(

Hth.

Regards,
Thanks for the information Stuart .As I said to Rambo I am probably overthinking this but I have always believed that fettling the suspension set up is the best investment you can make. From what I can see then the front can only be adjusted by the spring weight and its length ( there is no preload adjustment )so I was hoping ( as a good old fashioned Yorshireman) to get it as close to right with the one purchase . if need be I can drop in a few shims for fine adjustment . It is always a compromise but me personally,I have never been a fan of that tightening sphincter moment !!:rolleyes:so I try hard to get a set up up that is predictable and consistent . I have decided to buy some progressive springs at the stock length provided by Peg and will see how I get on.
 

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Thanks Speed rattle as I have said to Rambo I have come from a sports bike background where 1/2" more preload makes a massive difference. I think I am probably over thinking it . Thanks for taking the time to respond though
no , youre not overthinking. if you notice and it matters youre doing the right thing. the suspension on these machines is crude by modern standards but that doesnt mean that it csnnot be tuned to be better than it is. like i said, i ride primitive roads so subtle suspension adjustments are swamped by the large rocks and potholes. like trying to sharpen a razor on a kerbstone.

keep experimenting. im very interested in reading what you learn.
 
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Hi,

Assuming you're talking about springs from Progressive Suspension (as opposed to springs from those well-known suspension specialists Ebay :cool:), these are what PS recommend for a '72 T120. I found them by:-

. entering "progressive suspension" into Google;

. selecting "progressive suspension fork springs" from the returned list and then "Fork Spring Kit - Progressive Suspension" from the returned links;

. on Fork Spring Kit | Progressive Suspension, clicking on "Select Your Bike" then "1972", "TRIUMPH" and "T120 (air-cooled)" from the displayed tables;

. on https://www.progressivesuspension.com/products/3064/1972/triumph/t120-air-cooled , clicking on "Fork Spring Kit".


Don't use anything intended for a triple (unless you're ... errr ... very heavy ...), their springs are (should be) stiffer; fwiw, I have twin springs in/on all my triples and I couldn't be described as "light" by any stretch of the imagination. :cool:

In addition, if you haven't done so already, I advise Damper valve seal conversion 1971 on (pair) (y) instead of the standard 97-4003 Damper head O-rings, (n) the latter are known to cause stiction that affects the suspension's response to small bumps. :(

Hth.

Regards,
Hi Stuart,
I just wanted to repost your post (I hope you don’t mind), in case the most important message is overlooked.
In a world of sh1t aftermarket parts, it is likely that there is a plethora of badly wound, poorly weighed and poorly tempered springs out there, the cheap and the nasty. Most come with no information, spring rate. etc. If they are progressive, how much progressive, how much will the weak end of the spring affect sag, how much softer is the weak end from the stiff end, how does this compare to the original springs. How did the company determine this.

Buying from a quality specialist company such as ‘Progressive’ is good advice that should be heeded.

regards
Peg.
 

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Hi Peg,
I just wanted to repost your post (I hope you don’t mind), in case the most important message is overlooked.
Buying from a quality specialist company such as ‘Progressive’ is good advice
😔

I've Progressive Suspension springs in all my Triumphs. First pair I bought when Trevor Gleadall owned L.P. Williams, it was him that advised me to use twin springs even in a triple.

In a world of sh1t aftermarket parts, it is likely that there is a plethora of badly wound, poorly weighed and poorly tempered springs out there, the cheap and the nasty.
Three of my Triumphs have disc-brake forks so have the long PS springs. The T150 is pre-'71 so has the short springs but also PS. I'm dubious the short springs can be that 'progressive'; however, a while ago, someone posted their newly-arrived 'standard' short springs weren't actually both the same length ... at least the PS short springs were ... :cool:

Hth.

Regards,
 

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Discussion Starter · #13 ·
Hi Peg,

😔

I've Progressive Suspension springs in all my Triumphs. First pair I bought when Trevor Gleadall owned L.P. Williams, it was him that advised me to use twin springs even in a triple.


Three of my Triumphs have disc-brake forks so have the long PS springs. The T150 is pre-'71 so has the short springs but also PS. I'm dubious the short springs can be that 'progressive'; however, a while ago, someone posted their newly-arrived 'standard' short springs weren't actually both the same length ... at least the PS short springs were ... :cool:

Hth.

Regards,
Hi Stuart , My progressive springs arrived from LP Williams this morning and are now fitted awaiting my clutch plates to arrive which unfortunately are currently out of stock.! The rebuild will then be pretty much complete just in time for winter:(
 

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The new springs will not be anything like modern suspension but there is an improvement. I also fitted some top quality stanchions from Len Craig but he has retired now. He told me there were budget versions and top quality and mine have been on over 10 years and not a speck of rust on the chrome. It is fun at times when out on a fast road to look down at the forks and watch them reacting very fast to all the little ripples. When i used engine oil many years ago, it was just a very harsh ride then i discovered thin fork oil
 

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Discussion Starter · #15 ·
The new springs will not be anything like modern suspension but there is an improvement. I also fitted some top quality stanchions from Len Craig but he has retired now. He told me there were budget versions and top quality and mine have been on over 10 years and not a speck of rust on the chrome. It is fun at times when out on a fast road to look down at the forks and watch them reacting very fast to all the little ripples. When i used engine oil many years ago, it was just a very harsh ride then i discovered thin fork oil
Hi, Rambo, As we say up here, buy cheap pay twice,so glad your stanchions are proving the mantra. To be fair I bought the T120 to enjoy something different because if I am been totally honest I know that the gap between what I can do and what my trusty Aprilia can do is widening . Old father time has got his hooks in me so I think my head down arse up days are numbered . I just want to potter about up in the Dales on something that is hopefully reliable and generally does what I tell it . The first thing I noticed on the test ride was the lack of front brake I then hit a false neutral which meant i was going quicker into a corner than I planned . Although she was bouncing around a bit she settled and impressed me which got me to thinking if I buy this thing then the first job, sort the brakes and upgrade the suspension . It was a wonder I didn't end up in a hedge back because when I got the bike home and sorted the brakes I couldn't get the front wheel to sit equi-distant in the forks. Initially I thought I had assembled the wheel incorrectly, then I thought that one stanchion must be higher in the yolks than the other. I stripped the front and found two different spring lengths. Worse I think someone had tried to address because the fork leg with the longer spring had about 75cc of oil, the one with the shorter spring about 150cc.In reality only one fork hag any damping To be fair when I was 19 ,skint and had my T140 then I may have tried something similar to stay on the road. This made me wonder what else I would find, so, I have pretty much rebuilt the chassis from the ground up. New alloys,electrics, lights,bearings ,rattle can paint job .suspension , sorted fuelling ( I think) etc.etc. I know she is a bit of a model hybrid, but I have kept the bits that make her a 72 so should I ever sell her and someone wants to they can with a new paint job re style her as original.
Anyway beneath is the result of 3 months of late nights and a few barrels of F**ks!! I forgot how every job, pretty much needs the removal of another part to complete it.
Fuel tank Tire Wheel Automotive fuel system Vehicle
 

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Those silencers, although quiet, will rob quite a bit of power. Alright up to about 70 mph then holds back a little. It depends just how fast you want to go versus the noise. That bike looks very presentable, especially the rims.
 

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When I was a kid, I took those silencers off my 72, but now I've got another same bike and I think the silencers look really nice. Worked in noisy environments my whole life and I've come to appreciate something quiet, but I think they sound plenty ballsy. Anyway, she's a beauty!
 

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Discussion Starter · #18 ·
Those silencers, although quiet, will rob quite a bit of power. Alright up to about 70 mph then holds back a little. It depends just how fast you want to go versus the noise. That bike looks very presentable, especially the rims.
Hi Rambo Thanks , the rims took up most of my budget the pipes were on when I bought it, on the test ride she pulled up to 90mph (on the clocks ) with a slipping clutch .The clutch only seemed to slip if you were a bit aggressive with the throttle . I tried tightening the springs and following the instructions to set the clutch up, but all i did was push the slipping higher up the rev range. I have now had the plates out and ordered a 7 plate conversion . I don't know whether you or anyone else can explain but the friction plates showing the wear seem to be mostly worn on the one face and then most of the wear is on their outer extremities (outside dia rather than inside dia) When my bank balance recovers then what pipes do you recommend , what will they give and will they need a re think on the carbs. ?
 

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Discussion Starter · #19 ·
When I was a kid, I took those silencers off my 72, but now I've got another same bike and I think the silencers look really nice. Worked in noisy environments my whole life and I've come to appreciate something quiet, but I think they sound plenty ballsy. Anyway, she's a beauty!
Cheers Flicker, When I was at home in the early 80s my oldT140 had Dunstalls fitted and my dear old mum used to make me push the bike to the end of the street to start it when i set off to work in the morning . I worked about 5 miles from home and when I got in there was always a cuppa waiting on the kitchen table (and women wonder why us lads love our mums) she reckoned she could hear when I left work .
 

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Cheers Flicker, When I was at home in the early 80s my oldT140 had Dunstalls fitted and my dear old mum used to make me push the bike to the end of the street to start it when i set off to work in the morning . I worked about 5 miles from home and when I got in there was always a cuppa waiting on the kitchen table (and women wonder why us lads love our mums) she reckoned she could hear when I left work .
My buddy back then had a '70 Tiger and lived 2 miles away. I could hear him start his bike and tell if he was riding toward me or away. Nice memories
 
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