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Discussion Starter #1
Hello Folks,

I also run a Triumph Sprint ST1050. It has uprated front forks and a Wilber rear shock. When I get back on the Duke it feels like the handlebars have been locked in comparison. It really needs pushing over and feels like it is running wide. The Duke has a heavier spring fitted (+ 2 Weight) and I have the seat height up a bit so there is around 15mm of wheel clearance on the centre stand.

Any comments to make her feel quicker in the turn?

Cheers John
 

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Raise the rear ride height if it is still at the OEM lower setting. In contrast my ST feels light at the bars compared to the 916, like it has power steering and the 916 does not. The 916 is the lighter bike by a lot, and you can feel that, but takes a good push at the bars to get it over. Other factors may be tire profile, bar width even rim and tire weight although the ST4s should have the decently light (for OEM) rims. Bar width is a big factor in my case. The ST has Cycle Cat bars and the grip is pretty wide offering more leverage. The 916 bars have a very narrow grip. The only thing between my hands and the fork tubes are switch gear and master cylinder clamps.
 

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Good afternoon John,
I am in the thinking process of that too.
Mine is raised at the back, so I have a 10mm gap between a new rear tyre and the floor, but she again runs wide in a turn when on the throttle.
I was thinking of lowering the front by raising the forks about 3mm.
Right now the top yoke is face to face with the forks (the forks do not protrude at all from the top yoke, if I am understood).
I am not sure that this is right, but I am trying to find a way to measure the distance of the upper side of the bottom yoke to the top end of the fork, as per the manual. I do not have such a long caliper, so any ideas welcomed.
 

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My SS felt that way when I bought it. I did all the changes described above but it still wasn’t like I felt it should be. New tires were the fix. The PO rode the slab every day and flattened the profile of the tires. They weren’t worn out, just worn in the center. With new tires , ( forks lowered a bit) turn in got much easier. The effort required was reduced much .
 

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I upgraded the steering stem bearings to a tapered set, which made a huge difference.

You might at least check/service those bearings and make sure the steering stem is set properly. If you go that far, though, you may as well install the tapered set while you're there. You can get a set for less than $50 and they are a big improvement over stock.
 

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I just measured my rear wheel height from floor , my ST3s is very stable at speed and I have no issues with initiating a turn , the distance between floor and center of rear tire while on center stand is 42mm or 1 and 5/8 inches ( rear tire is brand new PR4 with 500kms on it ) .... hope this helps ... I think I have seen much higher distances as well ....
Craig
 

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The Duke has a heavier spring fitted (+ 2 Weight) and I have the seat height up a bit so there is around 15mm of wheel clearance on the centre stand.

Any comments to make her feel quicker in the turn?
Is the "heavier" spring for your specific weight?
first and foremost, you MUST set the suspension sag
this is a fundamental must for correct handling

good basic video here:

at the 8:30 mark in the video, personal spring setup is also addressed
if your sag is wrong, and spring is to soft/hard for your weight then your bike will handle badly

ride height on my own bike has the tire touching the floor when on the center stand
I have the standard handle bars and it turns in like a dream
tire pressure (if to low) can cause problems
also worn tires can cause problems as the guys have said above

hope this is helpful :)
 

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Discussion Starter #9
Thanks Guys,

Spring was chosen for my weight which is around 210 lbs 95 Kilo. I have attempted to set sag but to my reading there is not enough adjustment which would suggest I should have gone 1 higher on the spring.

Anyway I set about looking at the rear height. First up is to WD the nuts top and bottom on the rod. I always do this 2-3 days before hand. I have cracked them before so the top came off easy. Bottom is tough to get to but it was loose! Um.. I checked seat height – 1.5 “ or 40 mm odd ! The height must have worked loose and extended.
I adjusted this down to 10mm ( I have had it touching before but found this awkward when parking or working on the bike)

It is much better now, but still a bit on the wide side. I shall have another go at my sag latter
 

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(The) ride height on my own bike has the tire touching the floor when on the center stand
I have the standard handle bars and it turns in like a dream
I had mine set to be ~ 3/8" (10 mm) off the floor. That gave a very neutral response in corners when changing throttle. However, it also meant that the chain was riding on the plastic slider atop the swingarm because it has to bend down to reach the top of the countershaft sprocket. When I recently went from a 15- to 14-tooth sprocket, this problem was made substantially worse. Hence, I raised the rear wheel back up somewhat and now there's some more tendency to swing wide. LT Snyder states that he's seen bikes with chain grooves worn into the top of the swingarm pivot caused by this geometry problem. With the tire at floor level, do you see any issues with the slider or wear marks on the swingarm? What size front sprocket are you using?

Atm, the only solutions I see are either/both: 1) Slide the front forks upwards in the triple clamp so that the rear wheel can be raised. 2) Use a 15- tooth front sprocket and go to a 44- or 46-tooth rear for lower gearing.

Opinions?
 

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Discussion Starter #11 (Edited)
Ok so i am running a 15 front cog but I run a bigger rear. I guess this may give the same issue but the old girl is 17 now so not see any issues
 

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The turn in feel will be helped by the ride height adjustment, but the running wide thing is suspension set up. Sag / preload, rebound and compression.

Here's a down and dirty cheat sheet.


On the chain rubbing the swing arm after raising the ride height issue. Going to a 14T front is an inexpensive and fast way to overcome the high OEM final drive ratio but IMHO not a good idea for the reason you mention, among others. I am up 3 on the rear and the normal 15T front. Rear tire about 10mm off the ground with fresh rubber and zero problems with chain rub.
 

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On the chain rubbing the swing arm after raising the ride height issue. Going to a 14T front is an inexpensive and fast way to overcome the high OEM final drive ratio but IMHO not a good idea for the reason you mention, among others. I am up 3 on the rear and the normal 15T front. Rear tire about 10mm off the ground with fresh rubber and zero problems with chain rub.
Does this require a longer-than-stock chain? If so, how much longer?
 

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SS904
excellent table for troubleshooting.
Please take into account that the front suspension of the ST4 has this design flaw, that you can not dial compression and rebound adjustments independently. This is a major issue to start with.
There have been a number of solutions applied through other forum members.
I am still thinking of it.
What I wish to do, is replace the internals of my front forks with a set from a 996-998, but they are shorter by 15mm. So I have to tackle this.
 

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Please take into account that the front suspension of the ST4 has this design flaw, that you can not dial compression and rebound adjustments independently.
That's very true. It's due to the rebound valve being at the top just under the fork cap. If the rebound valve is open enough for proper rebound, the compression circuit takes the path of least resistance and the oil blows right up the hollow rod to the rebound valve. The only way for compression to work as it should is to have the rebound valve closed, or mostly closed. Not going to work out...

Superbike cartridges have the rebound valve down at the bottom closer to the compression end with the screw adjuster being a long rod that fills the hole in the tube. Still not completely independent adjustments, but much much better.

Long ago I did Race Tech gold valves on the ST. I used lighter fork oil and set the high speed compression valves to my liking. Works fine for me. Haven't really changed anything since, except seals and fresh oil here and there. Good news is for the OP, the problem of going wide in the corners is possibly remedied with less compression (which can be accomplished with lighter oil if needed), and maybe less front pre load.
 

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Does this require a longer-than-stock chain? If so, how much longer?
FWIW, I went 1 up in the rear from stock (for the ST2) 15/42 to 15/43. It was a subtle but nice improvement, though I haven't had issues with the chain rubbing. The stock 102 link chain was barely long enough; I have maybe 1/4" forward adjustability at best. Then again, a slightly shorter wheelbase should help improve responsiveness somewhat.
 

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Discussion Starter #18
I am running Drive Chain 15/102/42. I "think" that there is an error in the owners manual and the ST4S is 100 link as standard but someone needs to confirm that
 

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LT Snyder states that he's seen bikes with chain grooves worn into the top of the swingarm pivot caused by this geometry problem.

With the tire at floor level, do you see any issues with the slider or wear marks on the swingarm? What size front sprocket are you using?
In my opinion there is no "geometry problem"
as you can see from the picture below, there is ample clearance between the chain and the swingarm
All motorcycle chains run on the nylon slider that is attached to the swingarm
that's what it's designed for
I would hazard a guess that Mr Snyder has seen bikes that have worn out chain sliders that have lacked maintenance

my ride height is set to what I consider a comfortable maximum adjustment
At that point the tire is touching the floor when on the center stand
I have it sitting on a piece of timber so I can lube/adjust the chain and check tire pressures etc
My chain and sprockets are all standard sizes

I would recommend that Johnny put all rebound and compression settings back to stock and start from there
from memory it was a good base to start from
But, again, sag, sag, sag
set up the sag correctly
This is a motorcycle handling fundamental !

I have my forks set pretty much flush with the top of the triple clamps
my bars as low as I can get them (because I like the riding position)
The rear tire touching the ground on the center stand and I just think about tipping into a corner and "she's there"

This bike is one of the most neutral handling bikes I have owned, so I find it a bit confusing why someone would have such a bad handling issue
maybe all of the running gear is in need of servicing ie: swingarm/wheel bearings, rear shock pivots, rear shock service, head stock bearings etc









Looking at this picture, I am probably up for some new fork springs
I have acquired some extra weight and now my pre-load is almost at maximum


 

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In the G.O.D ( good old days ) when you had a handling issue you would get the manual and go over the bike yourself to make sure everything seemed right, because you wouldn’t want to take the bike to the local shop only to find out you’d missed some bit of maintenance or had a loose bolt or something. You would be embarrassed that you weren’t maintaining things as they should be. Now, people jump on the web to find out why the bike they’ve never bothered to check so much as the air pressure in the tires doesn’t handle like a brand new one. I’m waiting for just one post where the poster has already at least done maintenance and adjusted things per the manual before asking questions. That will probably be a long wait.
 
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