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Discussion Starter · #1 ·
I first posted this on the Scrambler section on the AdvRiders site back in January 09. It pains me that so many people waste huge amounts of money on their forks when you can get a dramatic improvement for under £10.

I had a fiddle with my forks whilst doing lots of other things to my bike. My impressions of the forks was that they were far too stiff. So, I got myself some 7.5W fork oil (Std. is 10W) and put that in the forks to a level of 140mm from the top of the leg with spring removed and leg fully compressed.
Why 140mm? Well, the Thruxton forks are filled to that level, whereas the Scrambler is filled to 123mm. So, if you're going to reduce the damping you also need to reduce the spring rate. The simplest way is to increase the air chamber above the oil.
I've just come back from a 100 mile ride to test it and I'm very pleased with the result. I rode a variety of roads from fast dual carriageway to bumpy back lanes covered in crap. The forks now absorb the bumps instead of crashing into them.
I have to say; I don't know if this would be too soft for dirt roads but if your riding is mainly paved roads and, like me, you think the forks come too hard, then you should give this a try.
7.5W oil to 140mm. You heard it here first.


There are a few people on that forum that have tried it now and like it. And, actually when you think about it, it doesn't cost anything because you have to change the oil every now and then anyway.
 

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I'm running 5w to the top of the springs. Very nice, but I have no idea what the oil depth is.
 

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I first posted this on the Scrambler section on the AdvRiders site back in January 09. It pains me that so many people waste huge amounts of money on their forks when you can get a dramatic improvement for under £10.
I'll vouch for blacktiger's fork fix. My biggest criticism of the Scrambler's forks was that the damping was far too harsh, causing a severe jolt on bumps.

With the fork oil adjustment the damping works perfectly with the spring rate. I wouldn't spend another penny on the forks now.

The service guy at a local bike shop (who rides a Sprint) tried my bike and commented on how good the suspension was. 'Nuff said.
 

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Hi,

I have just changed my fork oil as suggested and filled to 140mm from the top. Am off to Box Hill now via the scenic route and will give my verdict on my return in an hour or two.

Here's hoping!

Peter
 

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Nice ride round the Surrey lanes, certainly an improvement worth more than the £10 it cost me. However it has really flagged how basic the rear shocks are!

So I will invest in some Ikons and report back as to how the overall setup is.

Peter
 

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I have ordered the 7.5W fork oil just now from Dennis Kirk . Gonna do this when I have the forks off to install the 7in Bonnie headlike and brackets . I have to have this on my scrambler as it's needed to get the Parabellum Scout ( that is COMING IN TWO WEEKS :) FINALLY ) to fit .

Thanks for posting this info . I believe the harsh forks are why I had the front stock TrailWing tire cup so badly before it was even worn 1/2 out . Least my friend at work told me cupping a tire was a "shock" problem the tires shouldn't have done that just themselves . Made sense to me , as my bike "hits" Michigan speed bumps as they call them here pretty hard .

Anyone have a link to changeing the oil in the front forks etc would be nice . I do have the Triumph manual but it's always nice to read up on how others have done it too .

cheers
spro
 

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your results may be an improvement,
However
if you're going to reduce the damping you also need to reduce the spring rate. The simplest way is to increase the air chamber above the oil.
This is not correct. The only way to change the spring rate is to change the properties of the spring or replace it with a spring of a different rate.
Also
technically, you do not have to change the spring rate to affect the damping. Spaing rate and damping are independent of each other.

I'm just sayen, not diss'en.
I went the same route as you as these thing are undersprung and over damped.

I got myself some 7.5W fork oil (Std. is 10W)
in the early years 7.5 was standard from factory.
 

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Well, the Thruxton forks are filled to that level, whereas the Scrambler is filled to 123mm.
This is because the Thruxton comes equipped with pre-load adjustable fork caps. Their added depth takes-up that volume.

/Mike
 

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I first posted this on the Scrambler section on the AdvRiders site back in January 09. It pains me that so many people waste huge amounts of money on their forks when you can get a dramatic improvement for under £10.

I had a fiddle with my forks whilst doing lots of other things to my bike. My impressions of the forks was that they were far too stiff. So, I got myself some 7.5W fork oil (Std. is 10W) and put that in the forks to a level of 140mm from the top of the leg with spring removed and leg fully compressed.
Why 140mm? Well, the Thruxton forks are filled to that level, whereas the Scrambler is filled to 123mm. So, if you're going to reduce the damping you also need to reduce the spring rate. The simplest way is to increase the air chamber above the oil.
I've just come back from a 100 mile ride to test it and I'm very pleased with the result. I rode a variety of roads from fast dual carriageway to bumpy back lanes covered in crap. The forks now absorb the bumps instead of crashing into them.
I have to say; I don't know if this would be too soft for dirt roads but if your riding is mainly paved roads and, like me, you think the forks come too hard, then you should give this a try.
7.5W oil to 140mm. You heard it here first.


There are a few people on that forum that have tried it now and like it. And, actually when you think about it, it doesn't cost anything because you have to change the oil every now and then anyway.
I did this fix and it does seem better when hitting the so called Michigan "speed" bumps . I haven't gotten a chance to do a lot of riding yet as the weather has turned wet then very very cold . I did try it two up the other day and it works with my and the misses also ( lets say the bike is loaded down )

I bought two quarts of oil and only used one , I had thought that the forks took more than that , go figure . 5.5 inches = 140 mm and I used at $1.97 Turkey baster that I got at WalMart to set the depth fully compressed . Was pretty easy to do with all the how to stuff here and pics to help .

I did find I need a 1/2 torque wrench to set the front axle nut correctly , I used my very old ( none click ? ) wrench . I had gotten a 3/8 drive , that works for all but the bigger nut .

best
spro
 

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Discussion Starter · #12 ·
your results may be an improvement,
However

This is not correct. The only way to change the spring rate is to change the properties of the spring or replace it with a spring of a different rate.
Also
technically, you do not have to change the spring rate to affect the damping. Spaing rate and damping are independent of each other.

I'm just sayen, not diss'en.
I went the same route as you as these thing are undersprung and over damped.


in the early years 7.5 was standard from factory.
I don't think you actually read what I wrote. Or didn't understand.
The air in the chamber above the oil acts as a progressive, RISING RATE spring as the forks compress, giving assistance to the steel spring.
I also never wrote that you had to change the spring rate to affect the damping. WHAT I meant in what I wrote was if you change one it's a good idea to change the other to suit.
That's why, when I decreased the oil viscosity from 10W to 7.5W, I increase the air chamber by putting less oil in thus giving LESS assistance to the steel spring.
Got it now?
It's cheap and it's an improvement. What the hell?
 

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Same problems with stock Bonnie springs as well, which went away with the simple installation of Ikon progressive springs. I didn't even add oil or change it as the miles were low on the bike.
 

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WHAT I meant in what I wrote was if you change one it's a good idea to change the other to suit.
That's why, when I decreased the oil viscosity from 10W to 7.5W, I increase the air chamber by putting less oil in thus giving LESS assistance to the steel spring.
I'd think keeping the same oil level might result in a harsher rebound.
It also sounds like this fix should work good at making the front more compliant over the bumps - but also make the brake dive even worse than before..?
 

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Hmm, I've gone another way with my Scrambler: Ikon fork springs (tight coils UP of course) and 517cc of 15W fork oil in each leg (I think having the correct quantity (and the SAME quantity!) in each fork is what matters, not this crap about fork oil levels. I now see I didn't note how big a space I cut, but think it was 1.5 inches.
Anyway, the result has been great, a firm ride, which I like (but I'm 100kg and use the Scram for 2-up touring often), with nice sharp steering and a kindof good solid 'feel' to the front end.
The front now matches the ikon shocks on the back, all works well and inspires confidence on numerous surfaces.

I guess the bottom line with suspension setup is that it's very subjective indeed, and the factors that impact it (roads, use, weight, preferences, combinations of mods etc etc) are legion, and the whole thing is down to preference and trial & error.

NZ Triumph owner's club National Rally down here this weekend - the town is overrun with Triumphs - yee-hah!
cheers Pat
 

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Well it's nice out again and have had 4 trips on the bike to work so far and I can say that the front shocks are much much better over the speed bumps . I have one mile of road that has 4 pretty good ones and tonight it just glided over those bumps at 60 mph were it used bounce me pretty good .

Over all I would say this mod has been a real winner . Thanks again for the TIP !
 

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Here's an old drawing I made showing using the turkey baster. It was specific to the intiminator installation (fork oil wt and level). Works great ..... just don't return it to the kitchen!



Bob
 

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I first posted this on the Scrambler section on the AdvRiders site back in January 09. It pains me that so many people waste huge amounts of money on their forks when you can get a dramatic improvement for under £10.

I had a fiddle with my forks whilst doing lots of other things to my bike. My impressions of the forks was that they were far too stiff. So, I got myself some 7.5W fork oil (Std. is 10W) and put that in the forks to a level of 140mm from the top of the leg with spring removed and leg fully compressed.
Why 140mm? Well, the Thruxton forks are filled to that level, whereas the Scrambler is filled to 123mm. So, if you're going to reduce the damping you also need to reduce the spring rate. The simplest way is to increase the air chamber above the oil.
I've just come back from a 100 mile ride to test it and I'm very pleased with the result. I rode a variety of roads from fast dual carriageway to bumpy back lanes covered in crap. The forks now absorb the bumps instead of crashing into them.
I have to say; I don't know if this would be too soft for dirt roads but if your riding is mainly paved roads and, like me, you think the forks come too hard, then you should give this a try.
7.5W oil to 140mm. You heard it here first.


There are a few people on that forum that have tried it now and like it. And, actually when you think about it, it doesn't cost anything because you have to change the oil every now and then anyway.
BTiger,

Tried this mod and was really impressed at the way the forks were able to absorb the lumps & bumps without jarring me or the bike. I ran the bike like this for about a month with no problems. Only after time, I started to feel that the bike didn’t like turning into a bend at speed and the steering felt vague, and I noticed the front end skimming up & down a bit into the lean. So I topped the forks back up to factory spec (123mm for the Scram) and went for a test ride. Strange thing is that the riding position feels much more assured and positive, the steering into the lean is much more direct and not vague at all, and the forks are not skimming in a lean. As you’d expect the down side is that the lumps & bumps are back, I would not have thought that 17mm difference in fork oil depth would make such a difference. Just wondering if this is just peculiar to me and my bike or if anyone else has encountered a similar experience?

Cheers
Steve
 

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Fork Air Gap Anomaly

Need some help here gents and gals. Old thread I know but it's a good one and my issue seems to line right up with it rather than a start a new one.....

I'm refreshing my Scram's forks with new seals, oil etc. and was planning on a minor tweak that Blacktiger has suggested mainly to increase my air gap to hopefully help curb some of the harshness of the Scram's forks.

Here's where it gets interesting.....
Pulled forks off, measured air gap for fun to see where the factory had it. According to the manual and common knowledge the stock Scram's air gap should be 123mm measured from the top of the slider to the top of the oil with the springs and spacers out, forks compressed.
Both of mine were at precisely 165mm. ?????
I have always noticed the forks are very harsh on sharp bumps which I am excited to remedy. However, if I raise the oil level to 140mm from 165mm they are going to be brick abrupt if not just flat lock up?
What might ya'll think is going on here? Only thing I can think of is I didn't have the sliders all of the way compressed therefore giving me a false or larger reading. The manual states to not push too hard in compressing the forks to avoid damaging the damper tubes/mechanism. I experimented a few times and definitely pushed them down firmly to where I could feel the spring loaded mechanism at the bottom... They sure felt bottomed out to me. I wish I had thought of draining the oil solely from one fork and measuring the volume that came out to cross reference but I didn't think of that until too late..... It's all mixed up in one of my oil recycle jugs now. Woops.
Anyone have any suggestions? I'm stumped on this one.
Thanks for any help or advice.
cdub
 
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