Longer Rear Shocks

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snowdr

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I have a 750 Combat Interstate. I have recently upgraded the isolastics to vernier style, and fitted clamps to the swinging arm pivot, which has tightened things up considerably. I’m now planning on new rear shocks, and I am considering increasing the length slightly, maybe by ½” from the standard 12.9 up to 13.4”.

Factors in this decision are

1. Slightly improved ground clearance

2. Easier to roll onto the centre stand. A not insignificant factor with my advancing age! Note that I have comfortably more than ½” clearance under the rear tyre when on the centre stand.

3. Slightly faster steering, although I am happy with the general feel at the moment, and certainly I would not want to do this if it were to make the bike “twitchy”.

Has anyone any experience of doing this? I would welcome any advice or suggestions.

I’m leaning towards Falcon shocks as they seem to get good reviews. They have been very helpful and are quick to respond to emails.

Many thanks.
 
I went for 10mm longer at the advice of Maxton. I’ve not had it on the track yet, but on the road it feels good.

Falcon shocks are very good. I do prefer the Maxton’s, but they are more costly.
 
I went with longer shocks from ikon, works great to deal with the slight rear end drop due to the change to 18" rear rim.
 
I would rather go for slightly SHORTER rear shocks:

- To free the rear wheel from the ground on the centre stand (longer shocks can make the bike wiggle on the centre stand)

- Slightly better steering due to lower centre of gravity (no ground clearance problem with well set up exhaust system)

- No rubbing from rear chain on swing arm chainguard lug, longer shocks will make the chain rub this lug especially with a 21 teeth (or smaller) sprocket

- Easier to put your feet on the ground (when you are not that tall)
 
I’ve run longer shocks for years. I wish I could go longer. Limit is the cross brace of the swing arm wlll interfere with oil filter.
 
I did the same on my Commando racer with good results. Herb Becker does this with his Commando road race builds. You will not get into the twitchy mode with what you described.

Also consider the quality of the replacement shocks.
 
snowdr said:
I have a 750 Combat Interstate. I have recently upgraded the isolastics to vernier style, and fitted clamps to the swinging arm pivot, which has tightened things up considerably. I’m now planning on new rear shocks, and I am considering increasing the length slightly, maybe by ½” from the standard 12.9 up to 13.4”.

Factors in this decision are

1. Slightly improved ground clearance

2. Easier to roll onto the centre stand. A not insignificant factor with my advancing age! Note that I have comfortably more than ½” clearance under the rear tyre when on the centre stand.

3. Slightly faster steering, although I am happy with the general feel at the moment, and certainly I would not want to do this if it were to make the bike “twitchy”.

Has anyone any experience of doing this? I would welcome any advice or suggestions.

I’m leaning towards Falcon shocks as they seem to get good reviews. They have been very helpful and are quick to respond to emails.

Many thanks.
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I'm confused. There seems to be a difference of opinion about whether longer or shorter shocks make it easier or more difficult to get a bike up on its centerstand. Would like to see the reasoning behind these two opposite opinions. Also wouldn't increasing/decreasing the pre-load accomplish the same thing - within limits.
 
Bodger said:
I'm confused. There seems to be a difference of opinion about whether longer or shorter shocks make it easier or more difficult to get a bike up on its centerstand.
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No difference of opinion expressed by any of the posters on this matter. nortonspeed just stated his opinion about how the bike behaves once up on the center stand.


Bodger said:
Also wouldn't increasing/decreasing the pre-load accomplish the same thing - within limits.
Click to expand...

Yes, increasing the preload, within reason but I don't recommend it as a specific preload is for other more important reasons.

nortonspeed asserted that shorter shocks result in better handling ("Slightly better steering due to lower centre of gravity"). The question I have is what is meant by "better steering"; slower more stable?
 
With the isolastics, changing steering geometry might be a dangerous game. In some situations the big tank-slapper can come from nowhere. With a normal bike, all you need do is to relax in a tight corner and note whether the bike tends to tighten it's line or run wide as you come out under power. As you brake, a neutral steering bike will tend to run wide as the rake on the steering head reduces. As you accelerate, the rear end squats increasing the rake on the steering head, so the bike tends to tighten it's line. When you increase the length of the rear shocks, you tend to reduce the rake on the steering head, so the bike will tend to run wide a bit more, as you come out of corners. - Not what you need if you want to ride fast. When the bike tightens it's line as you power out of corners, it inspires confidence. If it runs wide, it is always a worry and hard work.
I would not let considerations involving the centre stand affect my thinking about my bike's handling. What it does on the road is more important.
 
If your bike tightens it's line as you power out of corners, you will usually find it is better as you brake into the corners. It does not become as stiff when you try to turn in. So more rear end squat is probably good - softer springs and more travel.
 
On my bike the center stand was worn and the bike sat lower with both tyres touching the ground, it also made it harder to get onto the stand and off it. I welded up the worn holes and the touching pads, the front wheel is now 1" off the floor but the bike can be tipped forward with finger pressure to get the rear off the floor, its easier to get both onto and off the stand. Longer shocks may have the same effect, or maybe not but it will affect the angle the center stand makes when you depress the stand to touch the floor.
 
Thanks for replies. I get the relationship between pre-load/length and rake but I dont really understand why this would have any benegicial effect on the centerstand. Seems to me you would be raising the back of the bike which would have the effect of lifting the centerstand. Wouldn't this, in turn, make it harder to lever the bike on to the stand - less of a fulcrum effect?
 
Dances with Shrapnel said:
nortonspeed asserted that shorter shocks result in better handling ("Slightly better steering due to lower centre of gravity"). The question I have is what is meant by "better steering"; slower more stable?
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Lowering the centre of gravity generally results in less front end lift on acceleration and less rear end lift when braking. If you want to know all about centre of gravity I recommend reading "the racing motorcycle" by John Bradley.
 
In about 1993, Honda built a 500cc MotoGP bike with a very low centre of gravity. It would not handle because the C of G was not high enough to rock the bike forwards and backwards sufficiently, as the bike accelerated and braked. In the same year, the 500cc Suzuki was underpowered but became world championship bike, because it tightened it's line in corners. There is an interesting video with Alan Cathcart which Duke Video has in stock. I once had a copy up on Youtube, but it infringed copyright and was taken down. Most handling aspects do not translate well between modern and classic bikes because of the immense horsepower differences. I think you will find modern bikes have much more stable handling, than a classic racing bike. With a classic bike, the handling can be extremely quick and it will still be safe.
 
Some time back I asked if anyone having the Greg Fauth extended travel front forks was using longer rear shocks with that modification. I don't think I got any replies, but I would think longer rear shocks would be a good Idea with the extra travel on the front forks assuming equal sag when riding.
Any thoughts?
Ray
 
nortonspeed said:
Lowering the centre of gravity generally results in less front end lift on acceleration and less rear end lift when braking. If you want to know all about centre of gravity I recommend reading "the racing motorcycle" by John Bradley.
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Lowering the centre of gravity, whilst keeping all else equal, should indeed do as you say.

But only lowering the rear will surely accentuate the effect of the front rising on acceleration?

It would also increase the rake, so will have other influences on the handling.
 
Scooter62 said:
Some time back I asked if anyone having the Greg Fauth extended travel front forks was using longer rear shocks with that modification. I don't think I got any replies, but I would think longer rear shocks would be a good Idea with the extra travel on the front forks assuming equal sag when riding.
Any thoughts?
Ray
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IMHO you’ve kinda answered your own question; it depends on the sag. It’s where the bike sits under sag that will determine if longer shocks will be needed I think.
 
Longer shocks make the bike easier to put on the center stand.
I had a FJR1300 with a Penske adjustable length shock and the difference hoisting that bike on the stand was huge.
 
nortonspeed said:
Lowering the centre of gravity generally results in less front end lift on acceleration and less rear end lift when braking. If you want to know all about centre of gravity I recommend reading "the racing motorcycle" by John Bradley.
Click to expand...

Lowering the center of gravity will diminish useable load transfer rear upon acceleration and forward upon hard braking, just when you need the useable load transfer the most. I recommend reading a whole variety of texts on the matter including those of Tony Foale, John Robinson, Kevin Cameron, Keith Code and....... PM me for the particulars; once read then let's chat again. It's not so black and white; there are clear benefits to quicker steering turn in as a result of raising the rear 10-20mm.
 
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