Showing posts with label Lowering Link. Show all posts
Showing posts with label Lowering Link. Show all posts

Tuesday 30 July 2013

How to Lower a CBR 1000F

CBR 1000F Lowering Link

There are various reasons why you might like to modify the stance of a bike.

Streetfighter types like to raise the rear ends of their bikes because they think it looks cool. The reason they think it looks cool is that vintage special builders do this to decrease the stability of their machines for more responsive cornering (with the added benefit of increased ground clearance, which means the bike can be leaned over more, which also helps with cornering). And it does look cool (up to a point).

Drag racer types lower both ends of their bikes for arcane reasons to do with centres of gravity and moments of inertia. Basically, it makes the bikes less inclined to wheelie.

Off-road types like to raise both both ends of their bikes for better ground clearance over obstacles. 

Adventure bike types also do this even though they don't generally need better clearance over obstacles. What they really need is to get their feet down securely to stabilise their heavy machines so lowering them might actually be a better way to go.

Which brings us to road-riders, who generally only lower their machines in order to better touch the ground with their feet.

I've been talking about lowering Big Honda for a while now and there are a number of reasons why I wanted to do this.

Firstly - Cosmetics. I like long, low bikes. If you have a bike that's already quite long, and you lower it, it looks even longer. I love that stretched street-bike look. I suspect it might be a bit dysfunctional, but as a look, it rocks! And at some point in the future, I may take Big Honda this far, but for the moment I just want it to be a little lower, and look a little longer without compromising it's useability too much.

How to Lower a CBR 1000F
As a practical daily runabout this may be slightly compromised but I think it looks fantastic!
Secondly - Feeling. I've run a number of lowered bikes over the years and I like the way they feel. Lowering the centre of gravity just feels more stable and secure and controlling the bike feels easier. But there's a tradeoff - you can't lean as far before bits of the bike start touching the ground. This is obviously detrimental to handling. However, driving normally, on a public road I very seldom lean a bike so far that it touches down, so on a road bike, and particularly on a tourer, I'm happy to trade some of that unused lean angle for the feeling of solidity.

How to Lower a CBR 1000F
Big Honda's new stance.

Thirdly (and this is really the main reason) - Comfort. It's comforting to be able to get both feet flat on the ground and it's nice to be able to get on and off a bike without any effort (Fully loaded adventure bike, I'm looking at you) but that's not exactly what I mean.

You see, the CBR 1000F has clip-on handlebars and they're quite low. If you want to go fast (over 90mph) it's a pretty comfortable bike. But when you're not going fast, (which if you live in a city is most of the time) you carry too much weight on your wrists and the bars stretch your shoulders and neck. 

How to Lower a CBR 1000F
VFR Clip-on bars mounted at the very top of the fork stanchions. The yokes (triple-trees) have been dropped down the forks, lowering the front of the bike while the rear of the bike has been dropped using a lowering link. This effectively raises the bars.

So my first attempt to alleviate this discomfort was to fit clip-on bars off a 1989 VFR 750. These pretty much bolted up with no modification. They're about 2" higher and a little closer so they do give an improvement. But on the trip to Kerry I still had pains in my neck and shoulder (from an old injury).

When I first put the VFR clip-ons on, I fitted them so that they were flush with the top of the fork-leg as opposed to touching the top of the top-yoke (triple-tree). This raised them about another 10mm. So, my really convoluted  reason for lowering the bike, was to bring the fork legs higher up in the top yoke which would effectively raise the bars.

In fact, the bars stay exactly the same height they've always been, but the rest of the bike is lowered under them. 

How to Lower a CBR 1000F
The new office. Note the GPS holder mounted on the filler cap bezel. More details on this Here

I could have just fitted handlebars which would have taken about the same amount of effort, but like I say, I just like low bikes. In fact, if I still get pains in my neck and shoulder, fitting handlebars will be my next move.

So how do you go about lowering a bike? 

Well the front is easy, you just open the yokes and slide the forks up through them, then clamp the yokes up again. I'm oversimplifying this a little, but not too much. You need to have an idea of how much travel the forks have so the fork-sliders/mudguard/wheel don't hit the bottom of the yoke. And if your bike has handlebars (as opposed to clip-ons) you might only be able to lower the bike a little before the fork legs hit the bars. With clip-ons this isn't an issue. It's generally possible to lower the front up to about two inches using this method. 

How to Lower a CBR 1000F
After lowering the rear, sliding the forks up inside the yokes restores the rake angle to it's normal setting of 27 degrees off the vertical.

How you lower the back depends on what kind of rear suspension you're dealing with. With a twin-shock setup you generally just fit shorter shocks, but you could relocate the shock mounts if you're a bit more adventurous.

This works with a Cantilever Monoshock  too, but you might be lucky enough to have a shock that's adjustable for ride height. The Öhlins shock on my Superlight has a couple of inches of ride height adjustment.

All this stuff works on a Rising-Rate Monoshock too, but cutting and welding the shock mounts is a lot of effort - there are much easier ways. Replacing the shock for an adjustable (or shorter) one is relatively easy but quite expensive unless you're lucky enough to pick one up second hand. The generally accepted way to lower this type of suspension is to use an aftermarket lowering link.

These are easy to get for popular, late model bikes and are easy to fit. 

My last couple of posts Here and Here deal with this in a bit more detail, but essentially, I wasn't able to get a lowering link for a CBR 1000F so I made my own. This dropped the back end by 30mm.

I then lowered the front by a corresponding amount by sliding the forks through the yokes as described above.

So now the whole thing sits a bit lower, except the handlebars, which are where they always were but feel like they've been raised.  The geometry remains essentially unchanged and the suspension works the way it's always done (in other words, it's no worse, but there's still room for improvement). I've ridden it for a couple of days (including some off road trails on Sunday) and ground clearance isn't an issue. It'll still do kerbs and speed bumps without touching down. So from a useability point of view the bike is unchanged.

However, the bike looks cooler without looking like it's really low.

It feels nicer to ride - it's hard to describe, but Diane drove it and she said it felt better too.

And it's more comfortable - the extra 30mm height on the bars puts them pretty much where I want them to be. I'll be going for a long trip next weekend so it remains to be seen if they're comfortable enough...

How to Lower a CBR 1000F
Does this make my boom look big?

#BigHonda #CBR1000F #CBR1000FTouring #Mercenary #MercenaryGarage

Monday 29 July 2013

CBR 1000F Lowering Link - Some Useful Information

The newest CBR 1000F in the world is now about 14 years old while the oldest is about 26! They're exceptionally well built and they sold well from new so there are still plenty of them around.

Generally, aftermarket support for them is still reasonably good - for example, I was able to get a new Givi mounting kit for the Wingrack and a taller screen. However, there don't appear to be any commercially available lowering links.

There's lots of talk about this on CBR Forum about this but there's very little hard data. So here's my contribution...

CBR 1000F Lowering Link - Some Useful Information

Above is a sketch of the standard link from a 1994 CBR 1000F. Below is what it all means...

  • The Pivot length is 115mm (the bearing housing is slightly shorter than this)
  • The Pivot Bolt is 10mm Diameter (M10)
  • The Rising-Rate Pivot length is 90mm (In other words, the distance between the dog-bones is 90mm)
  • The Rising-Rate Pivot Bolt is 10mm Diameter (M10)
  • The standard distance between the two bolts is 120mm centre to centre
  • Increasing the distance between the bolts by 12mm to 132mm centre to centre gives a drop of 30mm 

This is the standard link before I cut it up. It's shown here upside-down - the arm with the hole in the middle is on the RHS when the link is in the bike. I don't know what this hole is for - it doesn't appear to have a function. I wonder if it's an artifact from an earlier model or maybe something to do with the manufacturing process... Dunno.

Ground clearance on the standard bike is 135mm (Approx 5 1/4"). Increasing the length of the linkage by 12mm (Approx 1/2") reduces ground clearance to 105mm (Approx 4 1/8").

#CBR1000F #LoweringLink #Mercenary #MercenaryGarage

CBR 1000F Lowering Link (Cont.)

A couple of weeks ago I did a post about making a Lowering Link for Big Honda... Here

It got cut short because I ran out of Argon. So here's the rest...

CBR 1000F Lowering Link

The shot above shows extended arms fabricated out of 25mm x 3mm flat bar, with the remains of the original bearing housing with the arms cut off. The holes on the left are 10mm diameter and will take a 10mm bolt to connect the linkage to the Rising-Rate Link. The holes on the right are also 10mm diameter, but their only function is to act as a jig during the welding process.

CBR 1000F Lowering Link

The shot above shows the whole thing assembled and tack-welded. The nuts and threaded bars are just to keep everything in alignment. It was at this point that I discovered that I'd no argon and couldn't finish the welds.

CBR 1000F Lowering Link

Above, the thing is welded and painted and the bearings, seals and bushes have been replaced. And this reveals a problem...

I had been wondering why the original Dog-bones were in fact dog-bone shaped? Why not just weld on the arms with big welds like I've done here?

Well, I suspect the answer is something like this. The original dog-bones would work reasonably well with no welding at all, and in fact, the welds holding them on to the bearing housing are little more than tack-welds.

My deep-penetrating welds are plenty strong and I'm not worried about them failing, but the heat from the welding process has distorted the bearing housing very slightly and the pivot is now much tighter than it should be.

It still works, but this is not the way to fabricate a lowering link. If I was doing it again (and I suspect I probably will be), I would do it differently. I'd do it the way Honda did it in the first instance.

#CBR1000F #LoweringLink #Mercenary #MercenaryGarage

Wednesday 10 July 2013

CBR 1000F Lowering Link

Yesterday I was was making a lowering link to drop Big Honda a couple of inches. This is partly for cosmetic reasons and partly 'cos I can't leave well enough alone...

Anyway, it was all going smoothly 'til I went to weld the thing together, only to find that I'd run out of Argon. I wasn't really expecting this as as far as I can recall, the gas bottle isn't that old and I haven't done a lot of welding recently. Anyway, the upshot is, no welding until the replacement bottle arrives, hopefully tomorrow.

So rather than get all pissed off, I did something else instead... (See above)

There's a follow-up to this post... Here

Honda CBR1000F Lowering Link Dogbones

New lowering link (dogbone) jigged and tacked and ready for welding.

#CBR1000F #LoweringLink #Mercenary #MercenaryGarage