Top Yoke Nut & Fork Leg Adjustment

[alex]

2 dumb questions / lack of mechanic experience.

1. If I undo the top yoke nut to replace it with a shiny one from ProBolt (forum discount ), do I need to support the front end in any particular way? What actually happens when you undo it? What's it holding in place, the triple clamp?

2. If I want to adjust the front forks (drop them 1 line) to increase the front ride height, which bolts am I undoing? And as per the other question is this a job for a frame lift only?

There's probably a manual I should have downloaded, but it's good to talk...

 

[RRoss]

I recently replaced the top yoke nut with a nice gilles one and had no issues. Just check torque value as it was a lot higher than what I would have thought,also service manual says to lightly lubricate it first. As for the fork clamp bolts that you'll need to slacken I would advise that front is unloaded,abba stand with front lift arm or paddock stand that hooks into bottom of steering tube.

 

[Stephen]

If the yolk pinch bolts are tight then there's no problem swapping the nut

To adjust the height of your forks ideally you want the front end off the floor and the front wheel out however if you can't lift the front end you may be able to adjust them without, loosen the pinch bolts on the top and bottom yoke and the handlebar then twist the fork up or down as required. Obviously do each side separately...

 

[fast_ryan]

Ride Height

Just remember the following if your making any changes to ride height. The main reason to change a bike's ride height is to alter the steering geometry of the bike to either help it to turn more quickly or become more stable. An decrease in ride height quickens the steering, but makes the bike less stable and reduces rear grip under power. More ride height slows the steering, but makes the bike more stable and increases rear grip under power.

Geometry changes can be positive if you know the effect that you want to achieve and understand what the bike is preventing you from doing. However changing the ride height can result in the following symptoms.

Too little ride height will give you:
High-speed instability.
Poor rear grip.
Instability under heavy braking.

Too much ride height will give you:
Understeer on corner exit.
Difficulty in changing direction.
Poor front end grip on exit.

 

[alex]

Top Yoke Nut & Fork Leg Adjustment

Cheers Ryan.
Because its jacked up at the rear (due to the shock type) and at least 3 rings down at the front I want to experiment a bit.
Bring it up one line at a time and see how it goes.
I'll only do it though when I can test back to back on a 3 dayer in Spain.
I'm not trying to fix anything, I'm trying to understand how the changes affect things in real terms.


- Sent from Mobile

 

[RRoss]

That's more to do with changing the angle of the front forks I think. Did this on my bandit by raising the rear and it was noticeably sharper steering. Personally I wouldn't mess with standard geometry on the BMW as I'm sure they spent more than a few quid developing it.


Sent from my iPhone using Tapatalk

 

[soofsayer]

Alex's geometry is far from standard and his suspension isn't oe either. No pun intended.

 

[baz]

Raising the front will lengthen trail,which will slow the steering but will be more stable.However,it will improve rear traction.
In Alex's case,dropping the forks through will probably put his settings back nearer to where the gen2 seems to work best!

In answer to the original questionut the bike on a rear paddock stand,leave the front wheel in,place a jack under the engine and raise slightly to take the sag out of the forks.Slacken the four bolts on the lower triple clamp,slacken the two bolts slightly on the top yoke,raise/lower the jack to achieve the desired fork height.Tighten the lower bolts and upper bolts.And don't forget to raise the clip-ons.

 

[alex]

Cheers guys - good info.

Baz, would I need to ship a jack to the track or do their mechanics/garages come with stuff like that?

 

[fast_ryan]

Geometry

It will depend on which trackday provider you are using. Parkitt Racing support No Limits' European events and offer a full suspension setup service trackside. They have all manner of stands with them to facilitate suspension changes including geometry.

 

[alex]

Yeah I was just thinking that - better to wheel it down to one of them and work with them during the day on getting it setup. Gets the job done faster and I can discuss it with a more experienced engineer at the same time.

I'm a bit unhappy with the rear shock setup as it's nibbled the undertray under compression...so clearly doesn't fit as well as it could and is forcing the jacked up position. Overall, I think it would be better fitted to a 2015+ (like it's designed for) and I should get a K-Tech 35DDS lol - but I'll speak to Buildbase/Hawk...before they sling all the BMW gear out the door.

In my inexperience, I can't currently tell what "state" my bike is in...or which of the changes did what. I took a load of rotational mass out. Took out sprung and un-sprung weight. Fitted different tyres. Changed the gearing, suspension (inc flipped the eccentric bolt) and the geo. I think it needs riding by someone more experienced than me to baseline...but failing that I will just make iterative changes and try to understand what changes feel like.

When going through the build I asked for it to be pretty road orientated, softer springs all round, something good for places like Snetterton. But the rear could be compromising everything.
There's nothing specifically wrong, I just want to understand the bike more and understand how I can make changes to suit different tracks/usage. That's as much understanding what doesn't work as what does.

 

[baz]

Cheers guys - good info.

Baz, would I need to ship a jack to the track or do their mechanics/garages come with stuff like that?

You could probably put a small scissor jack with your kit/tools.Alternatively,at the circuit,you could improvise with a block of wood or similar(that's what I did,in Spain) and carefully lower the front paddock stand.As Ryan said,No Limits have Parkit,Focused Events have their own mechanic and also,in Spain,there is a very useful chap(I've forgotten his name)attends with his van-he has full facilities and can do virtually everything.He fitted my new wheel bearings,after I gave up trying to get them out(!),and only charged me 15 euros.
Failing all that,if you happen to be there when I'm there,I'll give you a hand.

 

[Andijoe]

Hi all, I've read this post with great interest as I'm currently suffering from a 'pushed wide' and 'difficult to turn' feel from my Gen 1. I've just had K-Tech internals fitted with a 10nm spring and have flipped the eccentric adjuster on the shock so that the whole is at the bottom not the top and my ride height is now at 84.8cm against a suggested 85cm from BMW for my height. I have 3 rings showing on my forks which is where they where last year when she handled really well. I've also changed to a 200 rear section tyre from a 190.

Can anybody suggest anything that would potentially cause her to push wide or not want to turn on a couple of corners at Snetterton, namely Wilson (1st hairpin) corner onto the back straight and Corams? I'm wondering if it's the eccentric adjuster that's maybe increased my preload thus making the back not want to do what I want it to?

Cheers in advance.

 

[alex]

Devils advocate. Is it the bike or the line/entry speed? IE you need higher entry speed, later apex to get the turn done under compression? Just a thought.

 

[Andijoe]

I don't think it's the line/entry speed Alex, as I tried a whole host of them with much the same results. I'm going to flip my eccentric adjuster back over, get the sag measured and adjusted if necessary and remeasure the ride height then try again as I'm back there in 2.5 weeks.

On another note, does anybody know what the OEM shock spring is rated at? I've tried a shock that had a 9.5nm rating but that was too stiff for my weight even with the preload fully wound out.

Cheers

 

[alex]

Ok cool - lots of experimenting.

FWIW...
https://www.southbayriders.com/forums/threads/105224/